bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential increased survival of staphylococci and limited ultrastructural changes in the core of infected fibrin clots after daptomycin administration
Authors: Michiels M J , Bergeron M G
Published: October 2018

A possible explanation for the difficulties encountered in curing deep fibrin-embedded infections is that antibiotic diffusion inside the infected fibrin matrix is not homogeneous and is insufficient to neutralize the pathogen. To evaluate this conjecture, the differential pharmacodynamics of daptomycin in fibrin clots infected with methicillin-susceptible and -resistant Staphylococcus aureus and Staphylococcus epidermidis was estimated. Daptomycin (20 or 50 mg/kg of body weight) was infused over 30 min. Fibrin clots and blood samples were evaluated from 0.5 to 42 h after the injections. The half-lives of daptomycin in serum and fibrin clot were close to identical after the two doses and averaged 5.4 and 22 h, respectively. The mean areas under the concentration-time curves from 0 to 42 h (AUC0-infinity) for daptomycin concentrations in serum and infected clots were 575 +/- 36.7 and 215 +/- 6.2 micrograms/g/h after administration of 20 mg/kg and 1,089 +/- 39.9 and 326 +/- 16.8 micrograms/g/h after administration of 50 mg/kg. A concentration gradient from the periphery to the core of the clots was observed in many clots up to 18 h after treatment. Mean peak concentrations in the core of the clots reached 60% of the peripheral values (P < 0.05) and were delayed for at least 3 h compared with the peripheral peak concentrations. AUC0-42 h of daptomycin concentration in the periphery and the core of clots were significantly different (P < 0.01). Survival of microorganisms was better in the core than in the periphery, with as much as a 3 log10 CFU/g difference between the center and the surface of the clot. Bacterial examination by transmission electron microscopy also showed noticeable differences in ultrastructural changes between those in the periphery and those in the core of the clots. In conclusion, the pharmacokinetics of daptomycin are significantly different at the periphery and within the core of fibrin clots, which may have led to the higher bacterial survival in the core of clots. Limited diffusion of daptomycin in fibrin, an essential component of the vegetation in bacterial endocarditis, could explain at least in part some of the treatment failures.
In vitro activities of azithromycin, clarithromycin, erythromycin, and tetracycline against 13 strains of Chlamydia pneumoniae
Authors: Welsh L , Gaydos C , Quinn T C
Published: October 2018

Thirteen strains of Chlamydia pneumoniae were evaluated for their in vitro susceptibilities to azithromycin, clarithromycin, erythromycin, and tetracycline. The MIC ranges were 0.125 to 0.5 micrograms/ml for azithromycin, 0.031 to 1.0 micrograms/ml for clarithromycin, 0.125 to 1.0 micrograms/ml for erythromycin, and 0.25 to 1.0 micrograms/ml for tetracycline. The ranges for the minimal lethal concentrations were 0.125 to 0.5 micrograms/ml for azithromycin, 0.031 to 1.0 micrograms/ml for clarithromycin, 0.125 to 1.0 micrograms/ml for erythromycin, and 0.25 to 1.0 micrograms/ml for tetracycline. Clarithromycin and azithromycin were the most active antibiotics against C. pneumoniae in vitro.
Absence of effect of trimethoprim-sulfamethoxazole on pharmacokinetics of zidovudine in patients infected with human immunodeficiency virus
Authors: Cañas E , Pachon J , Garcia-Pesquera F , Castillo J R , Viciana P , Cisneros J M , Jimenez-Mejias M E
Published: October 2018

Pharmacokinetic parameters of zidovudine (ZDV) were not altered in 16 patients receiving concomitant therapy with ZDV and trimethoprim-sulfamethoxazole by oral administration. ZDV areas under the concentration-time curves were (means +/- standard deviations) 1.80 +/- 0.70 and 1.69 +/- 0.64 micrograms.h/ml in the absence and presence of trimethoprim-sulfamethoxazole, respectively. ZDV clearances were 1.57 +/- 0.61 and 1.74 +/- 0.66 liters/h/kg, respectively.
Naphthalene sulfonate polymers with CD4-blocking and anti-human immunodeficiency virus type 1 activities
Authors: Rusconi S , Moonis M , Merrill D P , Pallai P V , Neidhardt E A , Singh S K , Willis K J , Osburne M S , Profy A T , Jenson J C , Hirsch M S
Published: October 2018

PIC 024-4 and PRO 2000 are naphthalene sulfonate polymers that bind to CD4 with nanomolar affinity and block binding of gp120. Both have activity against human immunodeficiency virus type 1 in H9 cells, peripheral blood mononuclear cells, and primary monocyte/macrophages, are synergistic with zidovudine, and do not inhibit tetanus toxoid-stimulated T-cell proliferation at anti-human immunodeficiency virus type 1 concentrations.
Antibiotic activity in microbiological media versus that in human urine: comparison of ampicillin, ciprofloxacin, and trimethoprim-sulfamethoxazole
Authors: Drobot G R , Karlowsky J A , Hoban D J , Zhanel G G
Published: October 2018

The activities of three antibiotics in both Mueller-Hinton broth (MHB) and pooled human urine were compared by using an in vitro pharmacodynamic model. Clinical and reference strains of Escherichia coli were exposed to antibiotics at concentrations achievable in human urine. The rate of bacterial killing (time to a reduction of 3 log10 CFU/ml) and the extent of bacterial killing at 24 h were examined. Between MHB and urine, there were no significant differences in the rate or extent of bacterial killing for both ampicillin and ciprofloxacin. For trimethoprim-sulfamethoxazole there was no significant difference in the extent of bacterial killing in urine compared with that in MHB (P > 0.1); however, there was a significant decrease in the rate of bacterial killing in urine compared with that in MHB (P < 0.001). We conclude that with ampicillin and ciprofloxacin, activity against E. coli in MHB is predictive of the effects in human urine. The activity of trimethoprim-sulfamethoxazole in MHB predicts the extent but not the rate of bacterial killing in human urine.
Inhibitory effect of cephalothin on matrix metalloproteinase activity around loose hip prostheses
Authors: Santavirta S , Takagi M , Konttinen Y T , Sorsa T , Suda A
Published: October 2018

The inhibitory effects of drugs on matrix metalloproteinase (MMP) activity in tissues around sites of loose total hip arthroplasty (THA) prostheses were studied. For activity measurements, a DNP-S (dinitrophenyl-Pro-Gln-Gly-Ile-Ala-Gly-Gln-D-Arg) peptide degradation assay was performed by means of high-performance liquid chromatography. Neutral salt tissue extracts revealed significantly elevated MMP activity in THA samples compared with that in noninflamed synovial tissue from the knee joint. This elevation was markedly inhibited by cephalothin, but not by doxycycline, tetracycline, or gentamicin. These results indicate that cephalothin can inhibit MMP activity in reactive periprosthetic tissue and thus reduce, by a nonantimicrobial mechanism, the tissue destruction associated with the loosening of THA implants.
Influence of antibiotic and E5 monoclonal immunoglobulin M interactions on endotoxin release from Escherichia coli and Pseudomonas aeruginosa
Authors: Lamp K C , Rybak M J , McGrath B J , Summers K K
Published: October 2018

Recent controversy surrounding the activity of monoclonal antibodies against endotoxin highlights the necessity of identifying all factors associated with increased mortality, one of which is endotoxin concentrations. Antibiotics may induce different patterns of endotoxin release. We compared the release of free endotoxin (in endotoxin units per milliliter) over 6 h and changes in numbers of CFU of exponentially growing Escherichia coli and Pseudomonas aeruginosa (10(6) to 10(7) CFU/ml) cultured in chemically defined endotoxin-free broth combined with pooled human serum and/or 10 micrograms of E5 immunoglobulin M monoclonal antibody per ml. MICs and MBCs were tested in each medium at the same inoculum. The inoculum was exposed to antibiotics at a single fixed multiple of the MIC for each medium (range, two to eight times the MIC). E5 antibody had no effect on MICs, MBCs, bactericidal activity, or endotoxin release. In the presence of 50% serum, amikacin, ceftazidime, imipenem, and ofloxacin each killed equivalent amounts of E. coli over 6 h; however, ceftazidime induced the highest release of endotoxin. Amikacin and ofloxacin produced the most favorable ratio of endotoxin release to amount of bacterial killing. In the presence of 50% serum, ceftazidime and imipenem reduced the P. aeruginosa inoculum to the greatest extent over 6 h. Although its bactericidal activity was diminished, ofloxacin caused the lowest release of free endotoxin. Imipenem and ofloxacin showed similar low ratios of endotoxin release to bacterial killing. In summary, antibiotic class, presence of serum, and type of organism influenced bactericidal activity and endotoxin release.
Antibacterial activity and pharmacokinetics of four new 7-azetidinyl fluoroquinolones
Authors: Coll R , Gargallo-Viola D , Tudela E , Xicota M A , Llovera S , Guinea J
Published: October 2018

The activity of E-4535, E-4534, E-4528, and E-4527, four new 7-azetidinyl-6-fluoroquinolones, was studied to evaluate the role played by the C-2' and C-3' substitutions of the azetidinyl group, together with a C-8 fluorine atom. In general, like other 6,8-difluoroquinolones, E-4534 and E-4527 showed higher levels of activity than the corresponding monofluorinated derivatives, E-4535 and E-4528. E-4535 and E-4534, having a 7-(2-methyl-3-aminoazetidinyl) substituent, demonstrated higher levels of activity in vitro than their corresponding structural analogs, E-4528 and E-4527, distinguished by a 3-methyl-3-methylaminoazetidinyl group at position 7 of the quinolone nucleus. In consequence, E-4534 was the most potent of the new agents tested.
Double-blind comparison of cefazolin and ceftizoxime for prophylaxis against infections following elective biliary tract surgery
Authors: Jewesson P J , Stiver G , Wai A , Frighetto L , Nickoloff D , Smith J , Schwartz L , Sleigh K , Danforth D , Scudamore C , Chow A
Published: October 2018

Antibiotics have been shown to reduce the incidence of wound infections after elective biliary tract procedures. Cefazolin and cefoxitin are among the agents most commonly promoted for this purpose. Cefoxitin has been substituted with ceftizoxime in many institutions; however, the role of ceftizoxime as a prophylactic agent in this setting has not been determined. To assess the comparative prophylactic efficacies of cefazolin and ceftizoxime in biliary tract surgery, we conducted a double-blind, randomized prospective clinical trial in a tertiary-care teaching hospital. Adult patients were randomized to one of two treatment groups and received a 30-min preoperative dose of study drug and as many as two postoperative doses at 12 and 24 h, depending on hospitalization status. Cefazolin and ceftizoxime were given as 1,000-mg doses. Patients with infections, those receiving prior antibiotics, or those with beta-lactam allergies were excluded. Over the 19-month study tenure, 167 patients were enrolled. Seventeen patients were excluded from analysis because of protocol violations. Of the 150 evaluable patients (72 and 78 receiving cefazolin and ceftizoxime doses, respectively), there was no significant difference among groups regarding sex, age, weight, preoperative Apache II score, baseline chemistry, and hematological parameters. Groups were also equivalent regarding the surgeon, type of procedure, characteristics (blood loss, drains, organ injury, and complications), and duration of hospital stay (mean, 5.6 versus 4.3 days [P = 0.31]). No clinical evidence of infection (7-day hospital stay and 30-day follow-up) was identified in 93% of cefazolin and 92% of ceftizoxime patients (P = 1.0). Microbiological confirmation was found in only 18% of primary-site infections. In conclusion, cefazolin and ceftizoxime appear to be equivalent for the prevention of infection in biliary tract surgery with the dosage regimens studied.
Ampicillin-sulbactam is effective in prevention and therapy of experimental endocarditis caused by beta-lactamase-producing coagulase-negative staphylococci
Authors: Ramos M C , Ing M , Kim E , Witt M D , Bayer A S
Published: October 2018

Optimal strategies for the prophylaxis and therapy of endocarditis caused by oxacillin-resistant, coagulase-negative staphylococci in patients with native or prosthetic valvular heart disease are not well defined. We compared the in vivo efficacies of ampicillin-sulbactam-based regimens with those of vancomycin-based oxacillin-resistant, beta-lactamase-producing coagulase-negative staphylococcal isolate (Staphylococcus haemolyticus SE220). Ampicillin-sulbactam (100 and 20 mg/kg of body weight, respectively, given intramuscularly in a two-dose regimen) was equivalent to vancomycin (30 mg/kg given intravenously in a two-dose regimen) in its prophylactic efficacy against the coagulase-negative staphylococcal strain (93 and 80%, respectively). The combination of ampicillin-sulbactam plus either rifampin or vancomycin did not enhance the prophylactic efficacy compared with that of ampicillin-sulbactam or vancomycin alone. In the therapy of established aortic valve endocarditis in rabbits caused by this same coagulase-negative staphylococcal strain, animals received 7-day ampicillin-sulbactam-based or vancomycin-based regimens with or without rifampin. All treatment regimens were effective at lowering intravegetation coagulase-negative staphylococcal densities and rendering vegetations culture negative compared with the coagulase-negative staphylococcal densities and vegetations of untreated controls, with ampicillin-sulbactam in combination with rifampin or vancomycin being the most active regimen. However, only the regimen of ampicillin-sulbactam in combination with vancomycin effectively prevented relapse of endocarditis posttherapy after a 5-day antibiotic-free period. For animals receiving rifampin-containing regimens, relapses of endocarditis were associated with the in vivo development of rifampin resistance among coagulase-negative staphylococcal isolates in the vegetation. Ampicillin-sulbactam was highly effective in the prevention of experimental endocarditis caused by a beta-lactamase-producing, oxacillin-resistant coagulase-negative staphylococcal strain. Ampicillin-sulbactam was also efficacious for the therapy of coagulase-negative staphylococcal endocarditis, especially when it was combined with vancomycin to prevent posttherapeutic relapses.
Disposition of intravenous metronidazole in Asian surgical patients
Authors: Ti T Y , Lee H S , Khoo Y M
Published: October 2018

Steady-state peak and trough concentrations of metronidazole and its metabolites were measured in the sera of 54 surgical patients who were on intravenous metronidazole, 500 mg every 8 h. These patients had no significant renal or hepatic impairment. High-pressure liquid chromatography was used to determine the concentrations of metronidazole and its metabolites. The mean peak and trough metronidazole concentrations were 28.9 +/- 11.0 and 18.0 +/- 9.9 micrograms/ml, respectively. The acid metabolite was not detectable in all the blood specimens. The mean peak concentration of the hydroxy metabolite (MH) was 6.6 +/- 4.3 micrograms/ml, the mean trough concentration of MH was 6.2 +/- 4.2 micrograms/ml, and the MH concentration/metronidazole concentration ratio was 0.4 +/- 0.24. Using a population-based method for the pharmacokinetic analysis and stepwise regression between parameters and covariables (sex, age, and weight), we found that weight showed the highest correlation with the total body clearance (CL). The mean CL was 0.89 +/- 0.3 ml min-1 kg-1 (3.029 liters/h), the mean volume of distribution was 0.73 +/- 0.14 liter/kg, and the mean elimination half-life was 10.6 +/- 4.5 h. For the patients in our study, the CL was lower and the elimination half-life was longer compared with those for healthy volunteers, but the values of these parameters were comparable to those found for hospitalized patients. There was an inverse correlation between age and CL.
Evaluation of susceptibility of gram-positive and -negative bacteria to human defensins by using radial diffusion assay
Authors: Takemura H , Kaku M , Kohno S , Hirakata Y , Tanaka H , Yoshida R , Tomono K , Koga H , Wada A , Hirayama T , Kamihira S
Published: October 2018

Defensins are small cationic bactericidal peptides present abundantly in the granules of polymorphonuclear neutrophils (PMNs). Human PMNs contain four defensins termed HNP-1 to HNP-4. We used a new assay system in agar plates, the radial diffusion assay, to evaluate the effects of human defensins against gram-positive and -negative bacteria. A crude mixture of HNP-1, -2, and -3 (crude HNPs) was purified from human PMN extracts by reversed-phase high-pressure liquid chromatography (RP-HPLC). The different components were later separated by RP-HPLC and gel permeation chromatography. We compared the antibacterial activities of purified HNP-1, -2, and -3 against Escherichia coli, Pseudomonas aeruginosa, methicillin-susceptible Staphylococcus aureus, and methicillin-resistant S. aureus strains using the radial diffusion assay. The antibacterial activities of HNP-1 and HNP-2 against all strains tested were similar to those of the crude HNPs, but the activity of HNP-3 was less than those of the other defensins. To quantitate the activities of HNPs against different bacteria, we defined the minimal dose of crude HNPs forming a detectable clear zone around the bacteria as the minimal inhibitory dose (MID) and determined the MIDs for 10 strains of E. coli, 12 strains of P. aeruginosa, 10 strains of methicillin-susceptible S. aureus, and 12 strains of methicillin-resistant S. aureus isolates, including clinical isolates. In general, the MIDs of the HNPs were similar against similar bacterial species. However, the MIDs for P. aeruginosa were higher than those for the other organisms tested. The radial diffusion assay is suitable as a screening test for measuring the susceptibilities of isolates to defensins, because it is sensitive and simple and has good reproducibility.
Specificity of induction of glycopeptide resistance genes in Enterococcus faecalis
Authors: Baptista M , Depardieu F , Courvalin P , Arthur M
Published: October 2018

Regulation of VanA- and VanB-type glycopeptide resistance in enterococci is mediated by related two-component regulatory systems (VanR-VanS and VanRB-VanSB). The transglycosylase inhibitors vancomycin, teicoplanin, and moenomycin induced synthesis of the VanX D,D-dipeptidase in a VanA-type Enterococcus faecalis harboring transposon Tn1546. Inhibitors of reactions immediately preceding (ramoplanin) or following (penicillin G and bacitracin) transglycosylation were not inducers. These results identify accumulation of membrane-bound lipid intermediate II as a potential signal for induction of VanA-type resistance. In E.faecalis BM4281 harboring a wild vanB genetic element, D,D-dipeptidase synthesis was only inducible by vancomycin. Induction of the production of the VanB ligase by vancomycin was required for growth of a vancomycin-dependent derivative of BM4281, since introduction of a plasmid coding for constitutive synthesis of the VanA ligase eliminated the requirement of glycopeptide for growth. Both vancomycin and teicoplanin were able to induce D,D-dipeptidase synthesis in BM4281 derivatives that were vancomycin and teicoplanin resistant or vancomycin and teicoplanin dependent. Acquisition of teicoplanin resistance in the latter types of strains was due to alteration in induction specificity associated with an increase in the sensitivity of the regulatory system to vancomycin. Thus, the wild VanRB-VanSB system is unable or not sensitive enough to sense teicoplanin, although mutations can lead to recognition of this antibiotic.
Involvement of topoisomerase IV and DNA gyrase as ciprofloxacin targets in Streptococcus pneumoniae
Authors: Pan X S , Ambler J , Mehtar S , Fisher L M
Published: October 2018

Ciprofloxacin-resistant mutants of Streptococcus pneumoniae 7785 were generated by stepwise selection at increasing drug concentrations. Sequence analysis of PCR products from the strains was used to examine the quinolone resistance-determining regions of the GyrA and GyrB proteins of DNA gyrase and the analogous regions of the ParC and ParE subunits of DNA topoisomerase IV. First-step mutants exhibiting low-level resistance had no detectable changes in their topoisomerase quinolone resistance-determining regions, suggesting altered permeation or another novel resistance mechanism. Nine of 10 second-step mutants exhibited an alteration in ParC at Ser-79 to Tyr or Phe or at Ala-84 to Thr. Third- and fourth-step mutants displaying high-level ciprofloxacin resistance were found to have, in addition to the ParC alteration, a change in GyrA at residues equivalent to Escherichia coli GyrA resistance hot spots Ser-83 and Asp-87 or in GyrB at Asp-435 to Asn, equivalent to E. coli Asp-426, part of a highly conserved EGDSA motif in GyrB. No ParE changes were observed. Complementary analysis of two S. pneumoniae clinical isolates displaying low-level resistance to ciprofloxacin revealed a ParC change at Ser-79 to Phe or Arg-95 to Cys but no changes in GyrA, GyrB, or ParE. A highly resistant isolate, in addition to a ParC mutation, had a GyrA alteration at the residue equivalent to E. coli Asp-87. Thus, in both laboratory strains and clinical isolates, ParC mutations preceded those in GyrA, suggesting that topoisomerase IV is a primary topoisomerase target and gyrase is a secondary target for ciprofloxacin in S. pneumoniae.
Microdilution antifungal susceptibility testing of Candida albicans and Cryptococcus neoformans with and without agitation: an eight-center collaborative study
Authors: Anaissie E J , Paetznick V L , Ensign L G , Espinel-Ingroff A , Galgiani J N , Hitchcock C A , LaRocco M , Patterson T , Pfaller M A , Rex J H , Rinaldi M G
Published: October 2018

The growth patterns observed in the trailing wells when fluconazole is being tested may give rise to readings that suggest resistance or increased MICs for known susceptible strains. We conducted a multicenter study to evaluate the intralaboratory and interlaboratory reproducibilities of a method that uses agitation to disperse these types of growth. Ten strains of Candida albicans and five strains of Cryptococcus neoformans were tested against fluconazole, flucytosine, and amphotericin B by using a microdilution adaptation of the proposed reference method of the National Committee for Clinical Laboratory Standards for yeasts (M27-T). The endpoint criterion used before agitation was consistent with the M27-T recommendation, while a criterion of 50% or more reduction of growth compared with the control was used after agitation. The results of this study showed that use of agitation and the modified endpoint criterion both improved intralaboratory and inter-laboratory agreement and increased the frequency of interpretable MICs. The MICs obtained by this method were comparable to those obtained by the broth macrodilution M27-T method. Like M27-T, this method was not able to definitely distinguish amphotericin B-susceptible from -resistant strains, although the MICs for the resistant strains were consistently higher than those for the susceptible ones. The findings imply that agitation should be seriously considered when antifungal agents, particularly fluconazole, are tested in a microdilution format.
Human immunodeficiency virus type 1 drug susceptibility determination by using recombinant viruses generated from patient sera tested in a cell-killing assay
Authors: Boucher C A , Keulen W , van Bommel T , Nijhuis M , de Jong D , de Jong M D , Schipper P , Back N K
Published: October 2018

A simple approach for the determination of drug susceptibilities by using human immunodeficiency virus type 1 (HIV-1) RNA from the sera of patients is described. HIV-1 RNA was extracted from patient sera, and the 5' part of the reverse transcriptase (RT) gene was transcribed into DNA and amplified in a nested PCR. The amplified fragment covers the 3' part of the protease gene and amino acids 1 to 304 of the RT gene. This fragment can be introduced through homologous recombination, as described previously, into a novel HIV-1 reference strain (pHXB2 delta 2-261RT) from which amino acids 2 to 261 of RT have been deleted. The resulting recombinant virus expresses all properties of the HXB2 reference strain except for those encoded by the introduced part of the patient RT gene. Recombinant viruses were subsequently tested for drug susceptibility in a microtiter format killing assay [3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay] as well as in the standard HeLa CD4+ plaque reduction assay. Similar susceptibility profiles were obtained by each assay with recombinant viruses derived from patients receiving alternating nevirapine and zidovudine treatment or lamivudine-zidovudine combination therapy. In conclusion, this approach enables high-through-put determination of the drug susceptibilities of serum RNA-derived RT genes, independent of the patient's viral background, and generates the possibility of relating changes in susceptibility to changes in viral genotypes.
Reduced accumulation of drug in Candida krusei accounts for itraconazole resistance
Authors: Venkateswarlu K , Denning D W , Manning N J , Kelly S L
Published: October 2018

Due to intrinsic resistance Candida krusei is emerging as a systemic pathogen in AIDS patients undergoing fluconazole therapy, but acquired resistance to itraconazole has not been studied biochemically. We report here studies on the basis for azole resistance and sterol composition in C. krusei. An itraconazole-resistant isolate showed reduced susceptibility to azole drugs in in vitro growth inhibition studies. Accumulation of 14 alpha-methyl-3,6-diol under azole treatment was associated with growth arrest. In vitro ergosterol biosynthesis and type II binding studies suggested no alteration in the affinity to azole drugs of the target enzyme, the cytochrome P-450 sterol 14 alpha-demethylase, in the resistant isolate. Resistance was associated with a decreased intracellular content of drug in the resistant isolate.
A TEM-derived extended-spectrum beta-lactamase in Pseudomonas aeruginosa
Authors: Mugnier P , Dubrous P , Casin I , Arlet G , Collatz E
Published: October 2018

A clinical strain of Pseudomonas aeruginosa, PAe1100, was found to be resistant to all antipseudomonal beta-lactam antibiotics and to aminoglycosides, including gentamicin, amikacin, and isepamicin. PAe1100 produced two beta-lactamases, TEM-2 (pI 5.6) and a novel, TEM-derived extended-spectrum beta-lactamase called TEM-42 (pI 5.8), susceptible to inhibition by clavulanate, sulbactam, and tazobactam. Both enzymes, as well as the aminoglycoside resistance which resulted from AAC(3)-IIa and AAC(6')-I production, were encoded by an 18-kb nonconjugative plasmid, pLRM1, that could be transferred to Escherichia coli by transformation. The gene coding for TEM-42 had four mutations that led to as many amino acid substitutions with respect to TEM-2: Val for Ala at position 42 (Ala42), Ser for Gly238, Lys for Glu240, and Met for Thr265 (Ambler numbering). The double mutation Ser for Gly238 and Lys for Glu240, which has so far only been described in SHV-type but not TEM-type enzymes, conferred concomitant high-level resistance to cefotaxime and ceftazidime. The novel, TEM-derived extended-spectrum beta-lactamase appears to be the first of its class to be described in P. aeruginosa.
Genetic organization and distribution of tetracycline resistance determinants in Clostridium perfringens
Authors: Lyras D , Rood J I
Published: October 2018

The Tet P determinant from the conjugative Clostridium perfringens R plasmid pCW3 two functional overlapping tetracycline resistance genes, tetA(P) and tetB(P). The tetA(P) gene encodes a putative 46-kDa transmembrane protein which mediates active efflux of tetracycline from the cell, while tetB(P) encodes a putative 72.6-kDa protein which has significant similarity to Tet M-like tetracycline resistance proteins (J. Sloan, L.M. McMurry, D. Lyras, S. B. Levy, and J. I. Rood, Mol. Microbiol. 11:403-415, 1994). In the present study, hybridization and PCR analysis of 81 tetracycline-resistant isolates of C. perfringens showed that they all carried the tetA(P) gene. Most of these isolates (93%) carried a second tetracycline resistance gene, with 53% carrying tetB(P) and 40% carrying a tet(M)-like gene. Despite the wide distribution of the tetB(P) and tet(M) genes, no isolate which carried both of these determinants was detected. In isolates that carried both tetA(P) and tetB(P) these genes overlapped, as in pCW3. Isolates carrying this combination of genes originated from diverse geographical locations and environmental sources. The single Clostridium paraputrificum isolate examined carried tetA(P), indicating that this gene is not confined to C.perfringens. However, neither tetA(P) nor tetB(P) was detected in the nine Clostridium difficile isolates tested. Nucleotide sequence analysis of isolates lacking tetB(P) revealed that they contained the tetA408(P) gene, which lacked the codons for the 12 carboxy-terminal amino acids of the TetA(P) protein.
Distribution of genes encoding resistance to streptogramin A and related compounds among staphylococci resistant to these antibiotics
Authors: Allignet J , Aubert S , Morvan A , el Solh N
Published: October 2018

The levels of resistance to pristinamycin (Pt) and to its major constituents, pristinamycin IIA and IB (PIIA and PIB, respectively; classified as streptogramins A and B, respectively) were determined for 126 staphylococcal isolates. The results suggest tentative susceptibility breakpoints of < or = 2, < or = 8, and < or = 0.5 microgram/ml for PIIA, PIB, and Pt, respectively. Fifty-six isolates that were inhibited by > or = 4 micrograms of PIIA per ml were investigated for the presence of staphylococcal genes encoding resistance to PIIA (vga, vat, and vatB) and PIB (vgb). None of these genes was found in the 4 isolates inhibited by 4 micrograms of PIIA per ml or in 4 of the other 52 isolates tested. The remaining 48 isolates harbored plasmids carrying vatB and vga or combinations of genes (vga-vat-vgb or vga-vat). The absence of any known PIIA resistance gene from the four Staphylococcus aureus isolates inhibited by > or = 8 micrograms of PIIA per ml suggests that there is at least one PIIA resistance mechanism in staphylococci that has not yet been characterized.
Effects of topical erythromycin on ecology of aerobic cutaneous bacterial flora
Authors: Vowels B R , Feingold D S , Sloughfy C , Foglia A N , Konnikov N , Ordoukhanian E , Starkey P , Leyden J J
Published: October 2018

We have demonstrated previously that application of topical erythromycin, an antibiotic commonly used for the treatment of acne, results in an increased density of cutaneous erythromycin-resistant (Emr) coagulase-negative staphylococci; however, it is unknown if this increase results in an overall higher density of total cutaneous staphylococci or if upon cessation of erythromycin use, Emr coagulase-negative staphylococci remain at an increased density compared with the pretreatment density. To investigate this, 2% erythromycin or vehicle was applied to each subject's forehead (n = 225) twice a day by laboratory personnel for a period of 6 weeks. Samples were obtained for culture from the forehead, anterior nares, and back of the subjects at baseline and at weeks 6, 9, and 12 of the study. Cultures were performed on differential media. Plates into which erythromycin was incorporated (8 micrograms/ml) were used to identify Emr coagulase-negative staphylococci. The species of all Emr coagulase-negative staphylococci were determined, and an antibiogram for 16 antibiotics was obtained. The baseline prevalence of Emr coagulase-negative staphylococci on the forehead and nose was about 80% at the two study sites, whereas that on the back was 50%. The baseline density of Emr coagulase-negative staphylococci on the forehead, nose, and back was approximately 20% of the total flora. Following 6 weeks of erythromycin treatment, the prevalence of Emr coagulase-negative staphylococci on the forehead and nose was nearly 100% and the densities were 73 and 62%, respectively; the prevalence and density for the back were 78 and 42%, respectively. The most prevalent erythromycin resistance gene expressed by the Emr coagulase-negative staphylococci was ermC. There was no increase in the numbers of Staphylococcus aureus, gram-negative rods, or yeasts, nor was there increased resistance to any other antibiotic except clindamycin. The density of total aerobic organisms also remained static. There were no changes in the prevalence or density of Emr coagulase-negative staphylococci in the vehicle group. A statistically significant decrease in the prevalence and density of Emr coagulase-negative staphylococci in the erythromycin group was observed within 3 weeks posttreatment and by 6 weeks posttreatment, the prevalence and density returned to baseline values. These data demonstrate that the increased prevalence and density of Emr coagulase-negative staphylococci as a result of topical 2% erythromycin use are transient on both population and individual levels.
In vitro activities of 14 antibiotics against 100 human isolates of Yersinia pestis from a southern African plague focus
Authors: Frean J A , Arntzen L , Capper T , Bryskier A , Klugman K P
Published: October 2018

A limited repertoire of antimicrobial agents is currently in use for the treatment of plague. We investigated the in vitro activities of some newer antimicrobial agents against Yersinia pestis. Among the injectable agents tested, cefotaxime was the most active, and among the oral agents, both levofloxacin and ofloxacin were highly active, with MICs at which 90% of isolates are inhibited of < 0.03 microgram/ml. the susceptibilities to the ketolide RU004 and the penem faropenem warrant attention. The enhanced activities of quinolones against Y. pestis suggest that these agents should be further investigated for the treatment of human plague in the future.
Uptake and intracellular activity of AM-1155 in phagocytic cells
Authors: Yamamoto T , Kusajima H , Hosaka M , Fukuda H , Oomori Y , Shinoda H
Published: October 2018

The uptake and intracellular activity of AM-1155 in murine J774.1 macrophages and human polymorphonuclear leukocytes were investigated. AM-1155 penetrated phagocytic cells rapidly and reversibly, although the penetration process was not affected by metabolic inhibitors such as sodium fluoride, cyanide m-chlorophenylhydrazone, or ouabain or by nucleoside transport system inhibitors such as adenosine. The intracellular concentration-to-extracellular concentration ratio of AM-1155 in both cell types of phagocytes ranged from 5 to 7. These ratios were almost equal to those for sparfloxacin. The intracellular activity of AM-1155 in J774.1 macrophages, examined with Staphylococcus aureus 209P as a test bacterium, was dependent on the extracellular concentration. AM-1155 at a concentration of 1 microgram/ml reduced the number of viable cells of S. aureus ingested by more than 90%. The intracellular activity of AM-1155 was more potent than those of sparfloxacin, ofloxacin, ciprofloxacin, flomoxef, and erythromycin. These results suggest that the potent intracellular activity of AM-1155 might mainly be due to the high intracellular concentration and its potent in vitro activity.
High-level fluoroquinolone resistance in Streptococcus pneumoniae requires mutations in parC and gyrA
Authors: Janoir C , Zeller V , Kitzis M D , Moreau N J , Gutmann L
Published: October 2018

The mechanism of high-level fluoroquinolone resistance was studied in strains of Streptococcus pneumoniae, either selected in vitro or isolated from clinical samples. By using DNA from these high-level-resistant strains, low-level-resistant transformants (MIC of pefloxacin, > or = 32 micrograms/ml; MIC of ciprofloxacin, 4 micrograms/ml; MIC of sparfloxacin, 0.50 micrograms/ml) were obtained at high frequencies (ca.10(-2)), while high-level-resistant transformants (MIC of pefloxacin, > or = 64 micrograms/ml; MIC of ciprofloxacin, 16 to 64 micrograms/ml; MIC of sparfloxacin, > or = 8 micrograms/ml) were obtained only at low frequencies (ca.10(-4)). This suggested that mutations in at least two unlinked genes were necessary to obtain high-level resistance. Low-level resistance was associated with ParC mutations (change from Ser to Tyr at position 79 [Ser79Tyr], Ser79Phe, or Asp83Gly). ParC mutations were associated, in high-level-resistant strains and transformants, with alterations in the quinolone resistance-determining region of GyrA (Ser84Tyr, Ser84Phe, and/or Glu88Lys). Low-level resistance was shown to be necessary for expression of the gyrA mutations. No mutation in the region corresponding to the quinolone resistance-determining region of GyrB and no alteration of drug accumulation were found.
Naturally azole-resistant Leishmania braziliensis promastigotes are rendered susceptible in the presence of terbinafine: comparative study with azole-susceptible Leishmania mexicana promastigotes
Authors: Rangel H , Dagger F , Hernandez A , Liendo A , Urbina J A
Published: October 2018

Leishmania braziliensis (isolate 2903) was naturally resistant to ketoconazole or the bis-triazole D0870, inhibitors of sterol C-14 demethylase, which produced only moderate effects on the proliferation of promastigotes at 10 microM. In contrast, Leishmania mexicana (isolate NR) was extremely susceptible to the azoles, as complete growth arrest and cell lysis were induced by incubation of the parasites with 0.05 microM concentrations of the drugs for 72 h. The opposite response was observed with terbinafine, an inhibitor of squalene epoxidase: L. braziliensis 2903 was three times more susceptible to the drug than L. mexicana NR (MICs of 5 and 15 microM, respectively). However, when the L. braziliensis stock was grown in the presence of 1 microM terbinafine, which by itself produced only marginal (< 10%) effects on growth, it became highly susceptible to the azoles, with an MIC of 0.03 microM. Analysis of cellular free sterols by high-resolution capillary gas chromatography coupled to mass spectrometry showed that 14-methyl sterols can support normal growth of L. braziliensis 2903 but not of L. mexicana NR. On the other hand, the higher susceptibility of the L. braziliensis isolate to terbinafine was correlated with a massive accumulation of squalene in the presence of the allylamine while no significant effects on L. mexicana sterol composition were observed at drug concentrations up to 1 microM. Thus, the > 300-fold increase in the susceptibility of L. braziliensis promastigotes to azoles in the presence of terbinafine was attributed to the combined effect of squalene and the methylated sterol precursors on the physical properties of the cell's membranes, leading to the loss of cell viability. Combination therapy with azoles and terbinafine in the treatment of human L. braziliensis infections deserves further study.
Inexpensive 4-hour micro-agar dilution susceptibility determination method
Authors: Holloway Y , Snijder J A , Schiphuis J
Published: October 2018

Using a micro-agar dilution (MAD) method in which microscope slides are covered with a thin film of agar, and MICs are read microscopically after a 4-h incubation, 18 antibiotics were tested against 29 to 32 microorganisms each. Identical MICs were obtained for microscopic MAD MICs performed in duplicate in 87.1% of the antibiotic-microorganism combinations, and 97.9% were identical within one dilution. When read macroscopically after an 18-h incubation, identical duplicate MICs were obtained in 86.8% of the cases, and 98.4% were identical within one dilution. Using agar dilution as the "gold standard," the correlation obtained with MAD slides read microscopically at 4 h was 94.3%, and macroscopic correlation at 18 h was 97.6%. The correlation of MAD slides with agar dilution for the groups of microorganisms most frequently used was as follows (microscopic/macroscopic): Staphylococcus aureus 96%/98%; Streptococcaceae 97%/98%; Enterobacteriaceae 98%/99%; and Pseudomonadaceae 95%/98%. At the present rate of exchange (fl 1.60 = $1.00f1p4he cost of a MAD slide, including labor, is $1.28 (20 microorganisms tested) or $0.06 per microorganism-antibiotic combination tested. This method is easy to perform, rapid, and inexpensive. It is suitable for use in routine and research laboratories.
Comparative serum bactericidal activities of ceftizoxime and cefotaxime against intermediately penicillin-resistant Streptococcus pneumoniae
Authors: Patel K B , Nicolau D P , Nightingale C H , Quintiliani R
Published: October 2018

In a randomized crossover study involving 12 healthy volunteers, 1 g of ceftizoxime or cefotaxime was administered intravenously every 12 h for a total of three doses on two separate weekends. The duration of serum bactericidal titers (SBTs) greater than 1:2 and the time serum drug concentrations remained above the MIC (T > MIC) were determined against three clinical isolates of Streptococcus pneumoniae with intermediate resistance to penicillin. The duration of SBTs and T > MIC for both antimicrobial agents exceeded 50% of the dosing interval for all isolates. Ceftizoxime's T > MIC was statistically greater than that of cefotaxime, indicating that its longer half-life in serum (1.7 h) compared with that of cefotaxime (approximately 1 h) compensates for its slightly lower microbiologic activity against the penicillin-resistant pneumococci tested in this study.
Safety and pharmacokinetics of 5-chloro-2',3'-dideoxy-3'-fluorouridine (935U83) following oral administration of escalating single doses in human immunodeficiency virus-infected adults
Authors: Riddler S A , Wang L H , Bartlett J A , Savina P M , Packard M V , McMahon D K , Blum M R , Dunn J A , Elkins M M , Mellors J W
Published: October 2018

5-Chloro-2',3'-dideoxy-3'-fluorouridine (935U83) is a nucleoside analog reverse transcriptase inhibitor that has demonstrated selective anti-human immunodeficiency virus (HIV) activity in vitro and favorable safety profiles in monkeys and mice. A phase I study was conducted to evaluate the safety and pharmacokinetics of six escalating single oral doses of 935U83 in 12 HIV-infected adults. The effect of a high-fat meal on the oral bioavailability of 935U83 was also assessed. The volunteers enrolled had CD4+ cell counts ranging from < 50 to 753 cells per mm3 (median, 198). In the dose range of 100 to 1,500 mg 935U83 was well tolerated by all subjects with no drug-related adverse events reported. No significant clinical or laboratory abnormalities were observed throughout the study. 935U83 was rapidly and well absorbed following oral administration with peak plasma concentrations (Cmax) occurring at 0.8 to 1.3 h postdosing. Mean Cmax and AUC0-infinity values of 935U83 were nearly dose proportional in the 100- to 1,500-mg dose range (from 2.4 to 30 micrograms/ml and from 3.4 to 59 h.micrograms/ml, respectively). Elimination of 935U83 from the plasma was rapid, with an apparent half-life of 1.3 to 1.7 h which was independent of the dose level. Administration of 935U83 with a high-fat meal decreased the rate of 935U83 absorption (mean Cmax decreased by approximately 50% and mean time to Cmax increased by approximately 1 h) but did not affect the extent of oral bioavailability (AUC0-infinity) of 935U83. The 5'-O-glucuronide conjugate was the principal metabolite of 935U83 and was present in the plasma of all volunteers at concentrations lower than 935U83. The molar AUC0-infinity ratio (935U83 glucuronide to the parent compound) was similar across all dose levels (mean, 21 to 27%). At least 60% of the 935U83 dose was absorbed, and approximately an equal percentage of the dose (approximately 30%) was excreted as unchanged 935U83 and as 935U83 glucuronide. Systemic exposure to 935U83 at levels exceeding its average in vitro antiretroviral 50% inhibitory concentration (approximately 0.5 microgram/ml or 1.8 microM) can be achieved after a single oral dose.
Genotypic and phenotypic changes during culture of a multinucleoside-resistant human immunodeficiency virus type 1 strain in the presence and absence of additional reverse transcriptase inhibitors
Authors: Shafer R W , Winters M A , Iversen A K , Merigan T C
Published: October 2018

The observation that human immunodeficiency virus type 1 (HIV-1) mutations conferring resistance to one reverse transcriptase (RT) inhibitor may suppress resistance to other RT inhibitors provides a rationale for treating HIV-1 with certain RT inhibitor combinations. We examined phenotypic and genotypic changes during culture of a multinucleoside (zidovudine, didanosine, zalcitibine, and stavudine)-resistant HIV-1 strain with and without additional RT inhibitors (nevirapine and lamivudine). The development of nevirapine or lamivudine resistance by the multinucleoside-resistant strain was not accompanied by a reduction in zidovudine or didanosine resistance.
Effect of alpha interferon (IFN-alpha) on 2'-5' oligoadenylate synthetase activity in peripheral blood mononuclear cells of patients with chronic hepatitis C: relationship to the antiviral effect of IFN-alpha
Authors: Pawlotsky J M , Hovanessian A G , Roudot-Thoraval F , Robert N , Bouvier M , Babany G , Duval J , Dhumeaux D
Published: October 2018

Alpha interferon (IFN-alpha) is, to date, the only treatment with proven efficacy in patients with chronic hepatitis C. However, less than 15% of the patients have a sustained response to IFN-alpha. Interferon acts through the induction of various cellular enzymes. Among them, the 2'-5' oligoadenylate synthetase (2-5OAS) is (at least in part) responsible for a direct antiviral effect of IFN-alpha. The aim of this study was to determine whether basal and IFN-alpha-induced in vivo and in vitro 2-5OAS activities measured in peripheral blood mononuclear cells predict biochemical and virological responses to IFN-alpha in patients with chronic hepatitis C. 2-5OAS activity in peripheral blood mononuclear cells and the antiviral effect of IFN-alpha were studied in 36 patients with chronic hepatitis C (27 men and 9 women; mean age, 44.7 years). Basal in vivo 2-5OAS activity (mean +/- standard error of the mean) was 4.41 +/- 0.69 nmol/10(6) cells. It was significantly induced at month 3 of IFN-alpha therapy (18.07 +/- 2.74 nmol/10(6) cells; P = 0.0001). No significant differences were found in basal in vivo 2-5OAS activities, in IFN-alpha-induced/basal in vitro 2-5OAS activity ratios, in IFN-alpha-induced in vivo 2-5OAS activities, and in IFN-alpha-induced/basal in vivo 2-5OAS activity ratios between the patients with and without a biochemical response (normal alanine aminotransferase activity in serum) or a virological response (normal alanine aminotransferase activity in serum and negative hepatitis C virus RNA detection) at any step of the study. At month 3 of therapy, p69, which is considered to be the active isoform of 2-5OAS, was induced, as demonstrated by Western blot (immunoblot) analysis in 50% of the patients, and induction of the p100 isoform was observed in 70% of the patients. No significant relationship with the response to IFN-alpha therapy was observed. Our results suggest that a deficiency of the IFN-alpha-dependent 2-5OAS system, which could be genetically determined, is unlikely to be responsible for the failure to achieve biochemical and virological responses to IFN-alpha therapy in patients with chronic hepatitis C.