bluuebunny/crossref_metadata_2025 huggingface dataset:
Parameters of bacterial killing and regrowth kinetics and antimicrobial effect examined in terms of area under the concentration-time curve relationships: action of ciprofloxacin against Escherichia coli in an in vitro dynamic model
Authors: Firsov A A , Vostrov S N , Shevchenko A A , Cornaglia G
Published: October 2018

Although many parameters have been described to quantitate the killing and regrowth of bacteria, substantial shortcomings are inherent in most of them, such as low sensitivity to pharmacokinetic determinants of the antimicrobial effect, an inability to predict a total effect, insufficient robustness, and uncertain interrelations between the parameters that prevent an ultimate determination of the effect. To examine different parameters, the kinetics of killing and regrowth of Escherichia coli (MIC, 0.013 microg/ml) were studied in vitro by simulating a series of ciprofloxacin monoexponential pharmacokinetic profiles. Initial ciprofloxacin concentrations varied from 0.02 to 19.2 microg/ml, whereas the half-life of 4 h was the same in all experiments. The following parameters were calculated and estimated: the time to reduce the initial inoculum (N0) 10-, 100-, and 1,000-fold (T90%, T99%, and T99.9%, respectively), the rate constant of bacterial elimination (k(elb)), the nadir level (Nmin) in the viable count (N)-versus-time (t) curve, the time to reach Nmin (t(min)), the numbers of bacteria that survived (Ntau) by the end of the observation period (tau), the area under the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point (time zero) to tau (AUBC), the area above this curve (AAC), the area between the control growth curve (log N(C)-t curve) and the bacterial killing and regrowth curve (log N(A)-t curve) from the zero point to tau (ABBC) or to the time point when log N(A) reaches the maximal values observed in the log N(C)-t curve (I(E); intensity of the effect), and the time shift between the control growth and regrowth curves (T(E); duration of the effect). Being highly sensitive to the AUC, I(E), and T(E) showed the most regular AUC relationships: the effect expressed by I(E) or T(E) increased systematically when the AUC or initial concentration of ciprofloxacin rose. Other parameters, especially T90%, T99%, T99.9%, t(min), and log N0 - log Nmin = delta log Nmin, related to the AUC less regularly and were poorly sensitive to the AUC. T(E) proved to be the best predictor and t(min) proved to be the worst predictor of the total antimicrobial effect reflected by I(E). Distinct feedback relationships between the effect determination and the experimental design were demonstrated. It was shown that unjustified shortening of the observation period, i.e., cutting off the log N(A)-t curves, may lead to the degeneration of the AUC-response relationships, as expressed by log N0 - log Ntau = delta log Ntau, AUBC, AAC, or ABBC, to a point where it gives rise to the false idea of an AUC- or concentration-independent effect. Thus, use of I(E) and T(E) provides the most unbiased, robust, and comprehensive means of determining the antimicrobial effect.
A complex mutant of TEM-1 beta-lactamase with mutations encountered in both IRT-4 and extended-spectrum TEM-15, produced by an Escherichia coli clinical isolate
Authors: Sirot D , Recule C , Chaibi E B , Bret L , Croize J , Chanal-Claris C , Labia R , Sirot J
Published: October 2018

Escherichia coli GR102 was isolated from feces of a leukemic patient. It expressed different levels of resistance to amoxicillin or ticarcillin plus clavulanate and to the various cephalosporins tested. The double-disk synergy test was weakly positive. Production of a beta-lactamase with a pI of 5.6 was transferred to E. coli HB101 by conjugation. The nucleotide sequence was determined by direct sequencing of the amplification products obtained by PCR performed with TEM gene primers. This enzyme differed from TEM-1 (blaT-1B gene) by four amino acid substitutions: Met-->Leu-69, Glu-->Lys-104, Gly-->Ser-238 and Asn-->Asp-276. The amino acid susbstitutions Leu-69 and Asp-276 are known to be responsible for inhibitor resistance of the IRT-4 mutant, as are Lys-104 and Ser-238 substitutions for hydrolytic activity of the extended-spectrum beta-lactamases TEM-15, TEM-4, and TEM-3. These combined mutations led to a mutant enzyme which conferred a level of resistance to coamoxiclav (MIC, 64 microg/ml) much lower than that conferred by IRT-4 (MIC, 2,048 microg/ml) but higher than that conferred by TEM-15 or TEM-1 (MIC, 16 microg/ml). In addition, the MIC of ceftazidime for E. coli transconjugant GR202 (1 microg/ml) was lower than that for E. coli TEM-15 (16 microg/ml) and higher than that for E. coli IRT-4 or TEM-1 (0.06 microg/ml). The MICs observed for this TEM-type enzyme were related to the kinetic constants Km and k(cat) and the 50% inhibitory concentration, which were intermediate between those observed for IRT-4 and TEM-15. In conclusion, this new type of complex mutant derived from TEM-1 (CMT-1) is able to confer resistance at a very low level to inhibitors and at a low level to extended-spectrum cephalosporins. CMT-1 received the designation TEM-50.
Pharmacodynamic properties of BAY 12-8039 on gram-positive and gram-negative organisms as demonstrated by studies of time-kill kinetics and postantibiotic effect
Authors: Boswell F J , Andrews J M , Wise R
Published: October 2018

Time-kill kinetics of BAY 12-8039 were studied at two inocula against three strains each of Bacteroides fragilis, Escherichia coli, Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pyogenes. The postantibiotic effects of BAY 12-8039 were studied on three strains each of E. coli, S. aureus, H. influenzae, Streptococcus pyogenes, and Streptococcus pneumoniae. The pharmacodynamic data demonstrated that BAY 12-8039 has marked activity against gram-positive and gram-negative organisms (under both anaerobic and aerobic conditions) and anaerobes. BAY 12-8039 also exhibited a postantibiotic effect of >1 h for all strains except one E. coli strain.
Pharmacodynamic effects of amoxicillin versus cefotaxime against penicillin-susceptible and penicillin-resistant pneumococcal strains: a phase I study
Authors: Aguilar L , Rosendo J , Balcabao I P , Martín M , Giménez M J , Frías J , Prieto J
Published: October 2018

Serum bactericidal activity against a penicillin-susceptible strain and a penicillin-resistant strain of Streptococcus pneumoniae (amoxicillin and cefotaxime MICs, 0.001 and 1 microg/ml, respectively, and MBCs, 0.01 and 2 microg/ml, respectively) was measured in 12 healthy volunteers who each received an oral 875-mg dose of amoxicillin and an intramuscular 1-g dose of cefotaxime in a crossover fashion. The areas under the bactericidal activity-time curves for the two strains were found to be similar for both antibiotics despite the significantly higher (P < 0.002) AUC/MIC and peak level/MIC values for cefotaxime.
Apparent involvement of a multidrug transporter in the fluoroquinolone resistance of Streptococcus pneumoniae
Authors: Baranova N N , Neyfakh A A
Published: October 2018

A Streptococcus pneumoniae strain selected for resistance to ethidium bromide demonstrated enhanced energy-dependent efflux of this toxic dye. Both the ethidium resistance and the ethidium efflux could be inhibited by the plant alkaloid reserpine. The ethidium-selected cells demonstrated cross-resistance to the fluoroquinolones norfloxacin and ciprofloxacin; this resistance could also be completely reversed by reserpine. Furthermore, reserpine potentiated the susceptibility of wild-type S. pneumoniae to fluoroquinolones and ethidium. The most plausible explanation for these results is that S. pneumoniae, like some other gram-positive bacteria, expresses a reserpine-sensitive multidrug transporter, which may play an important role in both intrinsic and acquired resistances of this pathogen to fluoroquinolone therapy.
In vivo and in vitro antiplasmodial activities of some plants traditionally used in Guatemala against malaria
Authors: Franssen F F , Smeijsters L J , Berger I , Medinilla Aldana B E
Published: October 2018

We present an evaluation of the antiplasmodial and cytotoxic effects of four plants commonly used in Guatemalan folk medicine against malaria. Methanol extracts of Simarouba glauca D. C., Sansevieria guineensis Willd, Croton guatemalensis Lotsy, and Neurolaena lobata (L.)R.Br. significantly reduced parasitemias in Plasmodium berghei-infected mice. Dichloromethane fractions were screened for their cytotoxicities on Artemia salina (brine shrimp) larvae, and 50% inhibitory concentrations were determined for Plasmodium falciparum in in vitro cultures. Both chloroquine-susceptible and -resistant strains of P. falciparum were significantly inhibited by these extracts. Of all dichloromethane extracts, only the S. glauca cortex extract was considered to be toxic to nauplii of A. salina in the brine shrimp test.
Efficacy of SCH-56592 in a temporarily neutropenic murine model of invasive aspergillosis with an itraconazole-susceptible and an itraconazole-resistant isolate of Aspergillus fumigatus
Authors: Oakley K L , Morrissey G , Denning D W
Published: October 2018

SCH-56592 (SCH) is a novel triazole antifungal agent with excellent in vitro activity against Aspergillus. We compared three doses (5, 10, and 25 mg/kg of body weight) of SCH with itraconazole (ITZ; 25 mg/kg) and amphotericin B (AB; 5 mg/kg) in a temporarily neutropenic murine model of disseminated aspergillosis (lungs and kidneys) against one ITZ-susceptible (AF71) and one ITZ-resistant (AF90) isolate of Aspergillus fumigatus. Treatment started 24 h after infection and lasted for 10 days. Dosing regimens for SCH were once daily for 10 days, those for ITZ were three times daily for 2 days and then twice daily for 3 to 10 days, and those for AB were once daily on days 1, 2, 4, and 7. Both isolates killed 90% of control mice. Kidneys and lungs from survivors were cultured on day 11. Against AF71, all three doses of SCH and ITZ yielded a 90 to 100% survival rate and AB yielded 40% survival (P < or = 0.01 to 0.0001 for all treatment groups compared with the controls). All three doses of SCH were superior to AB in cultures of lung and kidney tissue samples (P < or = 0.01 to 0.0002) and SCH at 25 mg/kg was superior to ITZ in cultures of kidneys (P = 0.01). Against AF90, the highest dose of SCH (25 mg/kg) resulted in a 100% survival rate, compared with 60 and 20% survival rates for the groups treated with SCH at 10 and 5 mg/kg, respectively. Treatment with ITZ yielded no survivors. AB therapy achieved a 50% survival rate. SCH at 25 mg/kg (P < 0.001), SCH at 10 mg/kg (P < or = 0.005), and AB (P < 0.05) were superior to ITZ in cultures of lungs and kidneys. There was a correlation between the MICs of SCH and quantitative organ culture results and between the minimum fungicidal concentration of AB with quantitative organ culture results. SCH appears to be a highly effective anti-Aspergillus compound in this model. There appears to be a degree of cross-resistance between itraconazole and SCH.
In vitro activity of Bay 12-8039, a new 8-methoxyquinolone, compared to the activities of 11 other oral antimicrobial agents against 390 aerobic and anaerobic bacteria isolated from human and animal bite wound skin and soft tissue infections in humans
Authors: Goldstein E J , Citron D M , Hudspeth M , Hunt Gerardo S , Merriam C V
Published: October 2018

The in vitro activity of Bay 12-8039, a new oral 8-methoxyquinolone, was compared to the activities of 11 other oral antimicrobial agents (ciprofloxacin, levofloxacin, ofloxacin, sparfloxacin, azithromycin, clarithromycin, amoxicillin clavulanate, penicillin, cefuroxime, cefpodoxime, and doxycycline) against 250 aerobic and 140 anaerobic bacteria recently isolated from animal and human bite wound infections. Bay 12-8039 was active against all aerobic isolates, both gram-positive and gram-negative isolates, at < or = 1.0 microg/ml (MICs at which 90% of isolates are inhibited [MIC90s < or = 0.25 microg/ml) and was active against most anaerobes at < or = 0.5 microg/ml; the exceptions were Fusobacterium nucleatum and other Fusobacterium species (MIC90s, > or = 4.0 microg/ml) and one strain of Prevotella loeschii (MICs, 2.0 microg/ml). In comparison, the other quinolones tested had similar in vitro activities against the aerobic strains but were less active against the anaerobes, including peptostreptococci, Porphyromonas species, and Prevotella species. The fusobacteria were relatively resistant to all the antimicrobial agents tested except penicillin G (one penicillinase-producing strain of F. nucleatum was found) and amoxicillin clavulanate.
Absence of age and gender effects on the pharmacokinetics of a single 500-milligram oral dose of levofloxacin in healthy subjects
Authors: Chien S C , Chow A T , Natarajan J , Williams R R , Wong F A , Rogge M C , Nayak R K
Published: October 2018

The influence of age and gender on the pharmacokinetics of levofloxacin in healthy subjects receiving a single oral 500-mg dose of levofloxacin was investigated in this parallel design study. Six young males (aged 18 to 40 years), six elderly males (aged > or = 65 years), six young females (aged 18 to 40 years), and six elderly females (aged > or = 65 years) were enrolled and completed the study. The study reveals that the bioavailability (rate and extent) of levofloxacin was not affected by either age or gender. In both age (young and elderly) and gender (male and female) groups of subjects, peak concentrations in plasma were reached at approximately 1.5 h after dosing; renal clearance of levofloxacin accounted for approximately 77% of total body clearance, and approximately 76% of the administered dose was recovered unchanged in urine over the 36 h of collection. The apparent differences in the calculated pharmacokinetic parameters for levofloxacin between the age groups (young versus elderly) and between the gender groups (males versus females) could be explained by differences in renal function among the subjects. A single dose of 500 mg of levofloxacin administered orally to both young and old, male and female healthy subjects was found to be safe and well tolerated. As the differences in levofloxacin kinetics between the young and the elderly or the males and the females are limited and are mainly related to the renal function of the subjects, dose adjustment based on age or gender alone is not necessary.
Variability of chromosomally encoded beta-lactamases from Klebsiella oxytoca
Authors: Fournier B , Roy P H
Published: October 2018

The beta-lactamase genes of Klebsiella oxytoca were previously divided into two main groups: bla(OXY-1) and bla(OXY-2). The two beta-lactamase groups were each represented by beta-lactamases with four different pIs. In each group, one form of beta-lactamase is more frequent than the others combined. The beta-lactamase gene of each representative beta-lactamase with a different pI that was not yet sequenced (pIs 5.7, 6.8 [OXY-2], 7.1, 8.2, and 8.8 [OXY-1]) was cloned and sequenced. The susceptibility patterns as well as relative rates and kinetic parameters for beta-lactam hydrolysis revealed that OXY-2 enzymes hydrolyzed several of the beta-lactams that were examined (carbenicillin, cephalothin, cefamandole, ceftriaxone, and aztreonam) at a greater rate than the OXY-1 enzymes did. Comparison of K. oxytoca beta-lactamases with plasmid-mediated extended-spectrum beta-lactamases MEN-1 and TOHO-1 implied that the threonine at position 168 present in OXY-2 beta-lactamase instead of the alanine in OXY-1 could be responsible for its modified substrate hydrolysis. In each group, the beta-lactamase with a variant pI differs from the main form of beta-lactamase by one to five amino acid substitutions. The substrate profile and the 50% inhibitory concentrations revealed that all substitutions differing from the main form of beta-lactamase were neutral except one difference in the OXY-1 group. This substitution of an Ala to a Gly at position 237 increases the hydrolysis of some beta-lactams, particularly aztreonam; decreases the hydrolysis of benzylpenicillin, cephaloridine, and cefamandole, and decreases the susceptibility to clavulanic acid (fivefold increase in the 50% inhibitory concentration).
Activity of a new liposomal formulation of amphotericin B against two strains of Leishmania infantum in a murine model
Authors: Paul M , Durand R , Fessi H , Rivollet D , Houin R , Astier A , Deniau M
Published: October 2018

The efficacy of a new liposomal formulation of amphotericin B was compared to that of amphotericin B deoxycholate (Fungizone) in a murine model of visceral leishmaniasis induced by Leishmania infantum. Median effective doses (ED50) were determined with two different strains: strain 1 was obtained from an untreated patient, and strain 2 was obtained from a patient who had received 12.5 g of amphotericin B over 3 years. BALB/c mice were infected intravenously on day 0 with promastigotes and then treated on days 14, 16, and 18 (strain 1) or on days 21, 23, and 25 (strain 2) with the liposomal formulation of amphotericin B (five doses were tested for each strain: 0.05, 0.1, 0.5, 0.8, and 3 mg/kg of body weight) or with conventional amphotericin B (four doses were tested for each strain: 0.05, 0.1, 0.5, and 0.8 mg/kg). Mice in the control group received normal saline solution. The liposomal amphotericin B formulation was about three times more active than the conventional drug against both strains. ED50 of the liposomal formulation were 0.054 (strain 1) and 0.194 (strain 2) mg/kg. ED50 of conventional amphotericin B were 0.171 (strain 1) and 0.406 (strain 2) mg/kg. Determination of drug tissular levels, 3 days after the last drug administration, showed a drug accumulation in hepatic and splenic tissues much higher after administration of liposomal amphotericin B than after conventional amphotericin B. A lack of toxicity was noted in all groups treated with the liposomal formulation.
Pharmacokinetics of L-749,345, a long-acting carbapenem antibiotic, in primates
Authors: Sundelof J G , Hajdu R , Gill C J , Thompson R , Rosen H , Kropp H
Published: October 2018

L-749,345 is a carbapenem antibiotic, currently in phase II clinical trials, which possesses a broad antibacterial spectrum and extended half-life. The time courses of levels of the drugs in plasma and urinary recovery were evaluated for L-749,345, imipenem-cilastatin (IPM), and ceftriaxone (CTX) in male rhesus monkeys (Macaca mulatta) and a chimpanzee (Pan troglodytes). The chimpanzee pharmacokinetics was predictive of human results and indicated a compound that was superior to IPM and approached CTX in its ability to persist in the circulation. Levels of binding to protein, in the range of clinically relevant concentrations in serum, are virtually equivalent for L-749,345 and CTX in humans. Results of a crossover bioassay versus those of a high-pressure liquid chromatography assay of 1-g human samples showed that there were no bioactive metabolites of L-749,345. The extended half-life at elimination phase of L-749,345 allows consideration of single daily dosing. In contrast to results with IPM, the improved stability of L-749,345 with respect to hydrolysis by the renal dehydropeptidase I (0.25 times the rate of IPM) results in urinary recovery sufficient for the drug's use as a single agent.
A study to determine the pharmacokinetics and inflammatory fluid penetration of two doses of a solid formulation of the hexetil prodrug of a trinem, sanfetrinem (GV 104326)
Authors: Wise R , Andrews J M , Da Ros L , Child J , Mortiboy D
Published: October 2018

The trinem sanfetrinem (GV 104326) was administered as the oral hexetil prodrug GV 118819X in two dose levels to six healthy volunteers. A single dose equivalent to 125 mg of sanfetrinem was administered, followed 6 weeks later by a single dose equivalent to 500 mg of sanfetrinem. The concentrations of the drug in plasma, cantharidin-induced inflammatory fluid, and urine were measured with a microbiological assay. The stability of sanfetrinem was studied in serum and inflammatory fluid. The mean peak concentrations in plasma of 0.77 and 2.47 microg/ml were attained at 1.1 and 2.0 h after the 125- and 500-mg doses, respectively. Mean peak concentrations in inflammatory exudate of 0.26 and 0.86 microg/ml were attained at 2.80 and 2.67 h after the 125- and 500-mg doses, respectively. The mean terminal elimination half-lives in plasma were 1.33 and 1.97 h for the 125- and 500-mg doses, respectively. The half-lives in the inflammatory fluid were 1.66 and 1.74 h for the 125- and 500-mg doses, respectively. The overall penetration of the drug into the inflammatory fluid was 51.4 and 47.0% for the 125- and 500-mg doses, respectively. Mean urine recovery was greater following 500 mg (24.15%) than after 125 mg (18.4%) of sanfetrinem. Sanfetrinem was relatively unstable in the inflammatory exudate in vitro (half-life, 5.5 h), and this could explain the poor penetration of the drug in the inflammatory exudate observed in this study.
Pharmacokinetics of isepamicin following a single administration by intravenous infusion or intramuscular injections
Authors: Radwanski E , Batra V , Cayen M , Korduba C , Cutler D , Affrime M , Nomeir A , Lin C C
Published: October 2018

The pharmacokinetics of isepamicin following administration of a 1-g dose were evaluated for 18 healthy male volunteers between the ages of 26 and 38. In a randomized crossover fashion, each volunteer received doses of isepamicin by a 30-min intravenous infusion and as an intramuscular injection. Blood samples were collected at specified times after dosing and assayed for isepamicin by a validated radioimmunoassay method. The individual plasma concentration-time curves were analyzed by noncompartmental methods. In general, the pharmacokinetics after intravenous infusion and intramuscular injection were similar. As expected, the maximum concentration of isepamicin in serum following intramuscular injection (37.2 microg/ml) was lower than the observed concentration at the end of infusion (66.7 microg/ml). The areas under the concentration-time curves from 0 h to infinity following intramuscular and intravenous administration were 164.8 and 154.5 microg x hr/ml, respectively, indicating complete absorption following intramuscular administration. The respective mean terminal-phase half-life (t1/2) values were 2.6 and 3.6 h. Although t1/2 was slightly longer following intravenous infusion, the small difference in the observed t1/2 values was not considered to be clinically significant. Total body clearances following intramuscular injection and intravenous infusion were 1.3 and 1.4 ml/min/kg, respectively, which were similar to renal serum creatinine clearances in healthy volunteers (> 1.14 ml/min/kg). The drug was safe and well tolerated. The results of the present study clearly show complete absorption of isepamicin following intramuscular administration. The similarity in the pharmacokinetics after intravenous infusion and intramuscular dosing would permit interchangeable administration of isepamicin by either route without compromising clinical efficacy.
Basis for the selective antibacterial activity in vitro of proton pump inhibitors against Helicobacter spp
Authors: Sjøstrøm J E , Kühler T , Larsson H
Published: October 2018

Proton pump inhibitors of the benzimidazole type exert a specific antibacterial activity against Helicobacter pylori in vitro. In the present study, the basis for this selectivity was investigated, and in particular, various factors affecting the in vitro antibacterial activity of sulfide analogs of benzimidazoles were studied. Upon preincubation of omeprazole for a period of up to 72 h in a buffer at pH 7, a product was formed that was bactericidal for H. pylori but had no effect on urease activity. Sulfide constitutes the main end product of degradation. The sulfide analog of omeprazole (H 168/22) exerted a bactericidal activity specifically against both resting (in buffer) and growing (in broth) Helicobacter spp., and time-kill in buffer at pH 5 was enhanced compared to that at pH 7. There was no or very low covalent binding of 3H-labeled H 168/22 to Helicobacter spp. or to other gram-negative and gram-positive bacteria. In the presence of fetal calf serum (FCS) under the same conditions, binding was only slightly lowered while the killing activity was markedly reduced, indicating a probably nonspecific interaction with proteins and/or protection of bacterial target(s) by FCS. Addition of H 168/22 (four times the minimum bactericidal concentration [MBC]) to exponentially growing H. pylori immediately stopped growth, and after an incubation period of 20 h viable counts were reduced by >7 log10. One-hour exposure of H. pylori to the drug followed by repeated washing retarded growth by about 2 h, indicating that the effect is reversible after short-term exposure. MICs and MBCs of various sulfide structures were lower than those obtained in broth after the addition of the corresponding sulfoxide. Thus, the MBC of the sulfide structure of omeprazole against 140 clinical isolates of H. pylori ranged from 8 to 32 microg/ml, compared to an MBC of omeprazole of 32 to 128 microg/ml. A similar potency was also recorded against other helicobacters. In conclusion, formation of sulfides of benzimidazoles in culture media is the reason for the selective antibacterial effect against H. pylori. The sulfides rapidly exerted a reversible antibacterial activity, which was specific against both resting and growing Helicobacter spp. without any covalent protein binding.
Successful single-dose teicoplanin prophylaxis against experimental streptococcal, enterococcal, and staphylococcal aortic valve endocarditis
Authors: Perdikaris G S , Pefanis A , Giamarellou H , Nikolopoulos A , Margaris E P , Donta I , Tsitsika A , Karayiannakos P
Published: October 2018

Teicoplanin is a glycopeptide antibiotic that is administered both intramuscularly and intravenously. It has a prolonged half-life and a less toxic profile in comparison to those of vancomycin. The efficacy of a single dose of teicoplanin (18 mg/kg of body weight given intramuscularly) for the prevention of endocarditis due to Streptococcus oralis, Enterococcus faecium, and methicillin-resistant Staphylococcus aureus (MRSA) was evaluated after applying the rabbit model. Vancomycin at a single dose of 30 mg/kg given intravenously was used as the comparative agent for the prevention of endocarditis due to MRSA and E. faecium, while ampicillin at a single dose of 40 mg/kg given intravenously was used as the comparative agent for the prevention of endocarditis due to S. oralis. Rabbits in the teicoplanin group were infected at 1 h postdosing with approximately 10(7) CFU of each strain. Rabbits in the other groups were infected at 0.5 h postdosing with approximately 10(7) CFU of S. oralis (ampicillin group) or E. faecium and MRSA (vancomycin group). All rabbits were sacrificed 5 days later. Teicoplanin and vancomycin protected the animals challenged with E. faecium by 87.5 and 50%, respectively, and protected the animals challenged with MRSA by 100 and 92%, respectively. Teicoplanin and ampicillin protected the animals challenged with S. oralis by 100 and 77%, respectively. Prevention of endocarditis by teicoplanin was likely to be due to a prolonged inhibition of bacterial growth by the sustained supra-MICs. It is concluded that teicoplanin is very effective in preventing experimental streptococcal, enterococcal, and staphylococcal endocarditis and may be an attractive alternative antibiotic in patients allergic to beta-lactams, especially in the outpatient setting.
Treatment of murine Candida krusei or Candida glabrata infection with L-743,872
Authors: Graybill J R , Bocanegra R , Luther M , Fothergill A , Rinaldi M J
Published: October 2018

L-743,872 is a broad-spectrum pneumocandin antifungal drug developed by Merck Research Co., and in the present work it was evaluated in vivo in murine models of Candida krusei and Candida glabrata infection. Mice were infected intravenously with two isolates of C. krusei and treated with fluconazole or L-743,872. Fluconazole was beneficial only in immune-competent mice infected with isolate 94-2696. At > 0.5 mg/kg of body weight/day, L-743,872 was effective against both infecting isolates in immune-competent and immune-suppressed mice. Against C. glabrata, L-743,872 was effective, at doses > or = 0.5 mg/kg, in reducing fungal cell counts in the kidneys but not in the spleen. L-743,872 has significant potential for clinical development.
Amoxicillin treatment of experimental acute otitis media caused by Haemophilus influenzae with non-beta-lactamase-mediated resistance to beta-lactams: aspects of virulence and treatment
Authors: Melhus A , Janson H , Westman E , Hermansson A , Forsgren A , Prellner K
Published: October 2018

Through alterations primarily in the penicillin-binding proteins, a non-beta-lactamase-mediated resistance to beta-lactams has evolved in Haemophilus influenzae. The virulence of these chromosomally changed strains has been questioned. To ascertain whether these alterations involve a reduction in virulence of H. influenzae and whether they could be advantageous for the bacterium during amoxicillin treatment of acute otitis media, a total of 70 Sprague-Dawley rats were challenged with a susceptible recipient strain or a genetically similar resistant transformant strain. Antibiotic therapy was started on day 3 after inoculation, and the animals were monitored by daily otomicroscopy and analysis of bacterial samples from middle ear effusions obtained on day 8, the last day of observation. The animals were also sacrificed on days 4 and 8 and after 2 months for morphological examination. Compared with the susceptible recipient strain, recovery from infections caused by the resistant transformant strain was delayed, and the late structural changes were more severe in the animals challenged with the latter strain. The results of the study indicate that chromosomal alterations mediating a relatively low level of resistance to beta-lactams may be advantageous for H. influenzae during antibiotic treatment of a local infection in the rat, and the alterations may occur without any significant loss of virulence.
Influence of OprM expression on multiple antibiotic resistance in Pseudomonas aeruginosa
Authors: Wong K K , Poole K , Gotoh N , Hancock R E
Published: October 2018

MexA-MexB-OprM is an efflux system in Pseudomonas aeruginosa. OprM overproduced from the cloned gene was able to complement OprM-deficient mutants but did not alter the resistance of a wild-type P. aeruginosa strain to the different antimicrobial agents tested. This suggests that OprM cannot function by itself to efflux antibiotics, including beta-lactams targeted to the periplasm.
Synergistic activities of clarithromycin and pyrazinamide against Mycobacterium tuberculosis in human macrophages
Authors: Mor N , Esfandiari A
Published: October 2018

The combination of clarithromycin and pyrazinamide was found to be synergistic against Mycobacterium tuberculosis in human macrophages. MICs were four- to eightfold lower for this combination than they were for either drug alone. Clarithromycin and rifampin, however, had only an additive effect.
In vitro pharmacodynamics of ceftazidime against Pseudomonas aeruginosa isolates from cystic fibrosis patients
Authors: Manduru M , Mihm L B , White R L , Friedrich L V , Flume P A , Bosso J A
Published: October 2018

The concentration/MIC (C/MIC) ratio maximizing the bactericidal activity of ceftazidime against 10 Pseudomonas aeruginosa isolates from cystic fibrosis patients was identified. Bactericidal activity was assessed by determining the percent difference in the area under the killing curve at each C/MIC ratio for all of the isolates from that of their growth control. The percent effect at each C/MIC ratio was fitted to a sigmoidal Emax model with maximum bactericidal activity defined as the C/MIC ratio that produced an effect that was 90% of the Emax. Our results suggest that at least some isolates may require higher C/MIC ratios than previously reported for maximal activity.
Adaptive mutations produce resistance to ciprofloxacin
Authors: Riesenfeld C , Everett M , Piddock L J , Hall B G
Published: October 2018

Mutation to ciprofloxacin resistance continually occurred in nondividing Escherichia coli cells during a 7-day exposure to ciprofloxacin in agar, while no accumulation of rifampin resistance mutations was detected in those cells. We propose that the resistance mutations result from adaptive mutations, which preferentially produce phenotypes that promote growth in nondividing cells.
Treatment of Histoplasmosis with MK-991 (L-743,872)
Authors: Graybill John R. , Najvar Laura K. , Montalbo Eleanor M. , Barchiesi Francesco J. , Luther Michael F. , Rinaldi Michael G.
Published: October 2018

BALB/c
nu
/+ immunocompetent and athymic (
nu/nu
) mice were infected intravenously with yeast cells of
Histoplasma capsulatum
. Mice were either given water (controls) intraperitoneally (i.p.) or given MK-991 i.p. once daily or twice daily. Protection was measured as prolonged survival or reduction in tissue counts. MK-991 was protective in immunocompetent mice, prolonging survival and reducing counts in spleen and livers at a dose as low as 0.05 mg/kg of body weight/day. MK-991 was modestly effective in athymic mice at a higher dose, 5 mg/kg/day. These studies suggest that MK-991 may be appropriate for clinical development in histoplasmosis.
Interaction of
Streptococcus pneumoniae
and
Moraxella catarrhalis
: Investigation of the Indirect Pathogenic Role of β-Lactamase-Producing Moraxellae by Use of a Continuous-Culture Biofilm System
Authors: Budhani R. K. , Struthers J. K.
Published: October 2018

The majority of clinical isolates of
Moraxella catarrhalis
produce β-lactamase. The role of this enzyme in the phenomenon of indirect pathogenicity, in which a true pathogen such as
Streptococcus pneumoniae
is protected from the action of certain β-lactam antibiotics, is well recognized. By using a simple continuous-culture biofilm system, it has been shown that the pneumococcus attains high titers in excess of 10
12
CFU/biofilm; furthermore, the penicillin-sensitive pneumococcus used remained susceptible to a range of β-lactam antibiotics in these biofilms (R. K. Budhani and J. K. Struthers, J. Antimicrob. Chemother. 40:601–602, 1997). This system was used to characterize the antibiotic susceptibility of this isolate when grown with β-lactamase-negative or -positive moraxellae. When grown with β-lactamase-producing moraxellae in the presence of either benzylpenicillin or amoxicillin, the pneumococcus was protected in the range of the antibiotic concentrations to which it would be considered resistant. With amoxicillin-clavulanic acid the titers of the two organisms collapsed at the antibiotic concentration at which moraxellae became susceptible. The levels of β-lactamase activity in cell-free supernatants of broth culture, in biofilm, and in biofilm effluent revealed distinct differences in this activity; levels in biofilm were significantly lower than those in broth culture supernatants. The system appears suitable for studying organisms under antibiotic stress and for investigating the interactions of bacteria under such conditions.
Identification and Characterization of Novel Antimicrobial Decapeptides Generated by Combinatorial Chemistry
Authors: Hong Sung Yu , Oh Jong Eun , Kwon Mi yun , Choi Myeong Jun , Lee Ji Hye , Lee Bok Luel , Moon Hong Mo , Lee Keun Hyeung
Published: October 2018

Novel combinatorial libraries consisting of simplified amino acid sequences were designed to screen for peptides active against the
Candida albicans
membrane. A novel decapeptide, KKVVFKVKFK, that had a unique primary amino acid sequence was identified in this work. This peptide irreversibly inhibited the growth of
C. albicans
and showed a broad range of antibacterial activity but no hemolytic activity. Circular dichroism spectra revealed that the predominant secondary structure of this peptide strongly depended on the membrane-mimetic environments; the peptide preferred to form an amphipathic α-helical structure in the presence of 50% trifluoroethanol, while it preferred to adopt a distorted α-helical structure in the presence of sodium dodecyl sulfate micelles. Experiments in which dye was released from vesicles indicated that this novel antimicrobial peptide killed microorganisms through the action on the membrane as its primary target. Replacement of amino acids in this active decapeptide on the basis of information from the libraries could provide unique information about factors affecting its antimicrobial activity such as its secondary structure, net positive charge, and hydrophobicity.
An
Escherichia coli
System Expressing Human Deoxyribonucleoside Salvage Enzymes for Evaluation of Potential Antiproliferative Nucleoside Analogs
Authors: Wang Jianghai , Neuhard Jan , Eriksson Staffan
Published: October 2018

Deoxyribonucleoside salvage in animal cells is mainly dependent on two cytosolic enzymes, thymidine kinase (TK1) and deoxycytidine kinase (dCK), while
Escherichia coli
expresses only one type of deoxynucleoside kinase, i.e., TK. A bacterial whole-cell system based on genetically modified
E. coli
was developed in which the relevant bacterial deoxypyrimidine metabolic enzymes were mutated, and the cDNA for human dCK or TK1 under the control of the
lac
promoter was introduced. The TK level in extract from induced bacteria with cDNA for human TK1 was found to be 20,000-fold higher than that in the parental strain, and for the strain with human dCK, the enzyme activity was 160-fold higher. The in vivo incorporation of deoxythymidine (Thd) and deoxycytidine (dCyd) into bacterial DNA by the two recombinant strains was 20 and 40 times higher, respectively, than that of the parental cells. A number of nucleoside analogs, including cytosine arabinoside, 5-fluoro-dCyd, difluoro-dCyd, and several 5-halogenated deoxyuridine analogs, were tested with the bacterial system, as well as with human T-lymphoblast CEM cells. The results showed a close correlation between the inhibitory effects of several important cytostatic and antiviral analogs on the recombinant bacteria and the cellular system. Thus,
E. coli
expressing human salvage kinases is a rapid and convenient model system which may complement other screening methods in drug discovery projects.
Antibiotic Susceptibility Patterns of
Streptococcus pneumoniae
in China and Comparison of MICs by Agar Dilution and E-Test Methods
Authors: Wang Hui , Huebner Robin , Chen Minjun , Klugman Keith
Published: October 2018

Beta-lactam resistance by
Streptococcus pneumoniae
is becoming a significant threat to public health worldwide. However, data concerning antibiotic susceptibility patterns in China have not been published. In this study, a total of 79 clinical isolates and 244 nasopharyngeal isolates of
S. pneumoniae
were recovered between June and November 1997 in Beijing. The agreement between the MICs (±1 log
2
dilution) of penicillin and ceftriaxone obtained by the agar dilution and E-test methods for the 79 clinical strains was very good (97.5 and 93.7%, respectively). Of these 79 strains, 9 (11.4%) were intermediate and 2 (2.5%) were resistant to penicillin. Of the 244 nasopharyngeal strains, 32 (13.1%) were intermediate and 3 (1.2%) were resistant to penicillin. The total of 277 penicillin-susceptible clinical and nasopharyngeal isolates of
Streptococcus pneumoniae
were 100% susceptible to amoxicillin-clavulanic acid, cefuroxime, ceftriaxone, and cefotaxime. In the 35 penicillin-intermediate and -resistant nasopharyngeal strains, elevated MICs of amoxicillin-clavulanic acid, cefuroxime, ceftriaxone, and cefotaxime were seen for ≤4 isolates. Of 244 nasopharyngeal isolates, the overall percentages of tetracycline, erythromycin, chloramphenicol, ofloxacin, and trimethoprim-sulfamethoxazole resistance were 87.6, 74.0, 47.8, 3.7 and 63.3, respectively. Vancomycin and rifampin resistance were not detected. These findings demonstrate that the rate of penicillin-resistant pneumococci is relatively low in China compared to those of other Asian countries. Resistance to non-beta-lactams was much higher than to beta-lactams. The E-test and agar dilution methods appeared to be comparable in identifying resistant strains.
Development of a New Cartridge Radioimmunoassay for Determination of Intracellular Levels of Lamivudine Triphosphate in the Peripheral Blood Mononuclear Cells of Human Immunodeficiency Virus-Infected Patients
Authors: Robbins Brian L. , Tran Thu T. , Pinkerton Frank H. , Akeb Fatima , Guedj Roger , Grassi Jacques , Lancaster Danny , Fridland Arnold
Published: October 2018

A new sensitive method for the measurement of lamivudine triphosphate (3TC-TP), the active intracellular metabolite of lamivudine in human cells in vivo, has been established. The procedure involves rapid separation of 3TC-TP by using Sep-Pak cartridges, dephosphorylation to 3TC by using acid phosphatase, and measurement by radioimmunoassay using a newly developed anti-3TC serum. The radioimmunoassay had errors of less than 21% and a cross-reactivity of less than 0.016% with a wide variety of other nucleoside analogs. The limit of quantitation of the assay for intracellular 3TC-TP was 0.195 ng/ml (0.212 pmol/10
6
cells), and a cell sample of only 4 million cells was ample for the assay. This procedure, combined with our previously developed method for measuring zidovudine (ZDV) metabolite levels, proved capable of measuring 3TC-TP, ZDV monophosphate (ZDV-MP) and ZDV triphosphate (ZDV-TP) in human immunodeficiency virus (HIV)-infected subjects treated with combination 3TC and ZDV therapy. In seven subjects, intracellular 3TC-TP levels ranged from 2.21 to 7.29 pmol/10
6
cells, while intracellular ZDV-MP and ZDV-TP levels ranged from <0.01 to 1.76 and 0.01 to 0.07 pmol/10
6
cells, respectively. Concentrations of 3TC in plasma determined in these subjects ranged from 0.34 to 9.40 μM, which was about fivefold higher than ZDV levels in plasma of 0.04 to 1.4 μM. This is the first study to determine the intracellular levels of the active metabolites in HIV-infected subjects treated with this combination. These methods should prove very useful for in vivo pharmacodynamic studies of combination therapy.
A New Approach to In Vitro Comparisons of Antibiotics in Dynamic Models: Equivalent Area under the Curve/MIC Breakpoints and Equiefficient Doses of Trovafloxacin and Ciprofloxacin against Bacteria of Similar Susceptibilities
Authors: Firsov Alexander A. , Vostrov Sergey N. , Shevchenko Alexander A. , Portnoy Yury A. , Zinner Stephen H.
Published: October 2018

Time-kill studies, even those performed with in vitro dynamic models, often do not provide definitive comparisons of different antimicrobial agents. Also, they do not allow determinations of equiefficient doses or predictions of area under the concentration-time curve (AUC)/MIC breakpoints that might be related to antimicrobial effects (AMEs). In the present study, a wide range of single doses of trovafloxacin (TR) and twice-daily doses of ciprofloxacin (CI) were mimicked in an in vitro dynamic model. The AMEs of TR and CI against gram-negative bacteria with similar susceptibilities to both drugs were related to AUC/MICs that varied over similar eight-fold ranges [from 54 to 432 and from 59 to 473 (μg · h/ml)/(μg/ml), respectively]. The observation periods were designed to include complete bacterial regrowth, and the AME was expressed by its intensity (the area between the control growth in the absence of antibiotics and the antibiotic-induced time-kill and regrowth curves up to the point where viable counts of regrowing bacteria equal those achieved in the absence of drug [
I
E
]). In each experiment monoexponential pharmacokinetic profiles of TR and CI were simulated with half-lives of 9.2 and 4.0 h, respectively. Linear relationships between
I
E
and log AUC/MIC were established for TR and CI against three bacteria:
Escherichia coli
(MIC of TR [MIC
TR
] = 0.25 μg/ml; MIC of CI [MIC
CI
] = 0.12 μg/ml),
Pseudomonas aeruginosa
(MIC
TR
= 0.3 μg/ml; MIC
CI
= 0.15 μg/ml), and
Klebsiella pneumoniae
(MIC
TR
= 0.25 μg/ml; MIC
CI
= 0.12 μg/ml). The slopes and intercepts of these relationships differed for TR and CI, and the
I
E
-log AUC/MIC plots were not superimposed, although they were similar for all bacteria with a given antibiotic. By using the relationships between
I
E
and log AUC/MIC, TR was more efficient than CI. The predicted value of the AUC/MIC breakpoint for TR [mean for all three bacteria, 63 (μg · h/ml)/(μg/ml)] was approximately twofold lower than that for CI. Based on the
I
E
-log AUC/MIC relationships, the respective dose (
D
)-response relationships were reconstructed. Like the
I
E
-log AUC/MIC relationships, the
I
E
-log
D
plots showed TR to be more efficient than CI. Single doses of TR that are as efficient as two 500-mg doses of CI (500 mg given every 12 h) were similar for the three strains (199, 226, and 203 mg). This study suggests that in vitro evaluation of the relationships between
I
E
and AUC/MIC or
D
might be a reliable basis for comparing different fluoroquinolones and that the results of such comparative studies may be highly dependent on their experimental design and datum quantitation.
Effect of Interleukin-10 on Gut-Derived Sepsis Caused byPseudomonas aeruginosain Mice
Authors: Matsumoto Tetsuya , Tateda Kazuhiro , Miyazaki Shuichi , Furuya Nobuhiko , Ohno Akira , Ishii Yoshikazu , Hirakata Yoichi , Yamaguchi Keizo
Published: October 2018

We evaluated the protective effect of interleukin-10 (IL-10) against murine gut-derived sepsis caused byPseudomonas aeruginosa. Gut-derived sepsis was induced by administering cyclophosphamide and ampicillin while feedingP. aeruginosato specific-pathogen-free mice. Treating mice with recombinant human IL-10 (rhIL-10) at 1.0 or 5.0 μg/mouse twice a day following the second cyclophosphamide administration significantly increased the survival rate compared to that of control mice treated with saline; however, treatment with rhIL-10 at 0.1 μg/mouse did not result in significant protection. Bacterial counts in the liver, spleen, and blood were all significantly lower in mice treated with rhIL-10 than in saline-treated control mice. Treatment with rhIL-10 significantly suppressed tumor necrosis factor alpha, interleukin-1β, interleukin-6, and gamma interferon levels in the serum of mice following induction of gut-derived sepsis. We also studied the effect of IL-10 on leukocyte recovery after cyclophosphamide treatment of mice. Administration of rhIL-10 intraperitoneally at 1.0 μg/mouse significantly accelerated the recovery of leukocytes in comparison with that of the group of saline-treated controls. These results indicate that IL-10 shows a protective effect against gut-derivedP. aeruginosasepsis. We suspect that the mechanism of this effect is that IL-10 regulates in vivo production of inflammatory cytokines. Furthermore, acceleration of leukocyte recovery by IL-10 after cyclophosphamide-induced depression may also play an important role in this protection.