bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Subinhibitory Concentrations of Antibiotics on Alpha-Toxin (
hla
) Gene Expression of Methicillin-Sensitive and Methicillin-Resistant
Staphylococcus aureus
Isolates
Authors: Ohlsen Knut , Ziebuhr Wilma , Koller Klaus-Peter , Hell Wolfgang , Wichelhaus Thomas A. , Hacker Jörg 
Published: October 2018

ABSTRACT

Concentrations of antibiotics below the MIC are able to modulate the expression of virulence-associated genes. In this study, the influence of subinhibitory doses of 31 antibiotics on the expression of the gene encoding the staphylococcal alpha-toxin (
hla
), a major virulence factor of
Staphylococcus aureus
, was investigated with a novel gene fusion protocol. The most striking observation was a strong induction of
hla
expression by subinhibitory concentrations of β-lactams and an almost complete inhibition of alpha-toxin expression by clindamycin. Whereas glycopeptide antibiotics had no effect, the macrolide erythromycin and several aminoglycosides reduced and fluoroquinolones slightly stimulated
hla
expression. Furthermore, Northern blot analysis of
hla
mRNA and Western blot (immunoblot) analysis of culture supernatants of both methicillin-sensitive and methicillin-resistant
S. aureus
strains revealed that methicillin-induced alpha-toxin expression is a common phenomenon of alpha-toxin-producing strains. Some methicillin-resistant
S. aureus
isolates produced up to 30-fold more alpha-toxin in the presence of 10 μg of methicillin per ml than in its absence. The results indicate that the novel gene fusion technique is a useful tool for studying the modulation of virulence gene expression by antibiotics. Moreover, the results suggest that the effects of certain antibiotics on virulence properties may be relevant for the management of
S. aureus
infections.
Suppression of Murine Endotoxin Response by E5531, a Novel Synthetic Lipid A Antagonist
Authors: Kobayashi Seiichi , Kawata Tsutomu , Kimura Akifumi , Miyamoto Kaname , Katayama Koichi , Yamatsu Isao , Rossignol Daniel P. , Christ William J. , Kishi Yoshito 
Published: October 2018

ABSTRACTAs a consequence of blood-borne bacterial sepsis, endotoxin or lipopolysaccharide (LPS) from the cell walls of gram-negative bacteria can trigger an acute inflammatory response, leading to a series of pathological events and often resulting in death. To block this inflammatory response to endotoxin, a novel lipid A analogue, E5531, was designed and synthesized as an LPS antagonist, and its biological properties were examined in vitro and in vivo. In murine peritoneal macrophages, E5531 inhibited the release of tumor necrosis factor alpha (TNF-α) byEscherichia coliLPS with a 50% inhibitory concentration (IC50) of 2.2 nM, while E5531 elicited no significant increases in TNF-α on its own. In support of a mechanism consistent with antagonism of binding to a cell surface receptor for LPS, E5531 inhibited equilibrium binding of radioiodinated LPS ([125I]2-(r-azidosalicylamido)-1, 3′-dithiopropionate-LPS) to mouse macrophages with an IC50of 0.50 μM. E5531 inhibited LPS-induced increases in TNF-α in vivo when it was coinjected with LPS into C57BL/6 mice primed withMycobacterium bovisbacillus Calmette-Guérin (BCG). In this model, the efficacy of E5531 was inversely correlated to the LPS challenge dose, consistent with a competitive antagonist-like mechanism of action. Blockade of the inflammatory response by E5531 could further be demonstrated in other in vivo models: E5531 protected BCG-primed mice from LPS-induced lethality in a dose-dependent manner and suppressed LPS-induced hepatic injury inPropionibacterium acnes-primed or galactosamine-sensitized mice. These results argue that the novel synthetic lipid A analogue E5531 can antagonize the action of LPS in in vitro and suppress the pathological effects of LPS in vivo in mice.
In Vitro and In Vivo Activities of Trybizine Hydrochloride against Various Pathogenic Trypanosome Species
Authors: Kaminsky Ronald , Brun Reto 
Published: October 2018

ABSTRACTTrybizine hydrochloride [O,O′-bis(4,6-diamino-1,2-dihydro-2,2-tetramethylene-s-triazine-1-yl)-1,6-hexanediol dihydrochloride] was active in vitro against the sleeping sickness-causing agentsTrypanosoma bruceisubsp.rhodesienseandT. bruceisubsp.gambiense; against a multidrug-resistant organism,T. bruceisubsp.brucei; and against animal-pathogenic organismsTrypanosoma evansi,Trypanosoma equiperdum, andTrypanosoma congolense; but not against the intracellular parasitesTrypanosoma cruziandLeishmania donovani. Cytotoxic effects against mammalian cells were observed at approximately 106-fold higher concentrations than those necessary to inhibitT. bruceisubsp.rhodesiense. Trybizine hydrochloride was able to eliminateT. bruceisubsp.rhodesienseandT. bruceisubsp.gambiensein an acute rodent model with four intraperitoneal doses of 0.25 mg kg of body weight−1or four doses of 1 mg kg−1, respectively, or with four oral doses of 20 mg kg−1. The compound expressed activity against suramin-resistantT. evansistrains in mice. However, these concentrations were not sufficient to cure mice infected with multidrug-resistantT. bruceisubsp.brucei. A late-stage rodent model with central nervous system involvement could not be cured, indicating that trybizine may not pass the blood-brain barrier in sufficient quantities.
Sordarins: In Vitro Activities of New Antifungal Derivatives against Pathogenic Yeasts,
Pneumocystis carinii
, and Filamentous Fungi
Authors: Herreros E. , Martinez C. M. , Almela M. J. , Marriott M. S. , De Las Heras F. Gomez , Gargallo-Viola D. 
Published: October 2018

ABSTRACT

GM 193663, GM 211676, GM 222712, and GM 237354 are new semisynthetic derivatives of the sordarin class. The in vitro antifungal activities of GM 193663, GM 211676, GM 222712, and GM 237354 against 111 clinical yeast isolates of
Candida albicans
,
Candida kefyr
,
Candida glabrata
,
Candida parapsilosis
,
Candida krusei
, and
Cryptococcus neoformans
were compared. The in vitro activities of some of these compounds against
Pneumocystis carinii
, 20 isolates each of
Aspergillus fumigatus
and
Aspergillus flavus
, and 30 isolates of emerging less-common mold pathogens and dermatophytes were also compared. The MICs of GM 193663, GM 211676, GM 222712, and GM 237354 at which 90% of the isolates were inhibited (MIC
90
s) were 0.03, 0.03, 0.004, and 0.015 μg/ml, respectively, for
C. albicans
, including strains with decreased susceptibility to fluconazole; 0.5, 0.5, 0.06, and 0.12 μg/ml, respectively, for
C. tropicalis
; and 0.004, 0.015, 0.008, and 0.03 μg/ml, respectively, for
C. kefyr
. GM 222712 and GM 237354 were the most active compounds against
C. glabrata
,
C. parapsilosis
, and
Cryptococcus neoformans
. Against
C. glabrata
and
C. parapsilosis
, the MIC
90
s of GM 222712 and GM 237354 were 0.5 and 4 μg/ml and 1 and 16 μg/ml, respectively. The MIC
90
s of GM 222712 and GM 237354 against
Cryptococcus neoformans
were 0.5 and 0.25 μg/ml, respectively. GM 193663, GM 211676, GM 222712, and GM 237354 were extremely active against
P. carinii
. The efficacies of sordarin derivatives against this organism were determined by measuring the inhibition of the uptake and incorporation of radiolabelled methionine into newly synthesized proteins. All compounds tested showed 50% inhibitory concentrations of <0.008 μg/ml. Against
A. flavus
and
A. fumigatus
, the MIC
90
s of GM 222712 and GM 237354 were 1 and 32 μg/ml and 32 and >64 μg/ml, respectively. In addition, GM 237354 was tested against the most important emerging fungal pathogens which affect immunocompromised patients.
Cladosporium carrioni
,
Pseudallescheria boydii
, and the yeast-like fungi
Blastoschizomyces capitatus
and
Geotrichum clavatum
were the most susceptible of the fungi to GM 237354, with MICs ranging from ≤0.25 to 2 μg/ml. The MICs of GM 237354 against
Trichosporon beigelii
and the zygomycetes
Absidia corymbifera
,
Cunninghamella bertholletiae
, and
Rhizopus arrhizus
ranged from ≤0.25 to 8 μg/ml. Against dermatophytes, GM 237354 MICs were ≥2 μg/ml. In summary, we concluded that some sordarin derivatives, such as GM 222712 and GM 237354, showed excellent in vitro activities against a wide range of pathogenic fungi, including
Candida
spp.,
Cryptococcus neoformans
,
P. carinii
, and some filamentous fungi and emerging invasive fungal pathogens.
Display of Functional β-Lactamase Inhibitory Protein on the Surface of M13 Bacteriophage
Authors: Huang Wanzhi , Petrosino Joseph , Palzkill Timothy 
Published: October 2018

ABSTRACT

The display of proteins on the surface of filamentous phage has been shown to be a powerful method to select variants of a protein with altered binding properties from large combinatorial libraries of mutants. The β-lactamase inhibitory protein (BLIP) is a 165-amino-acid protein that binds and inhibits TEM-1 β-lactamase-catalyzed hydrolysis of the penicillin and cephalosporin antibiotics. Here we describe the construction of a new phagemid vector and the use of this vector to display BLIP on the surface of filamentous phage. It is shown that BLIP-displaying phage bind to immobilized β-lactamase and that the binding can be competed off by the addition of soluble β-lactamase. In addition, a two-step phage enzyme-linked immunosorbent assay procedure was used to demonstrate that the BLIP-displaying phage bind β-lactamase with a 50% inhibitory concentration of 1 nM, which compares favorably with a previously published

K
i

of 0.6 nM. A system has therefore been established for protein engineering of BLIP to expand its range of binding to other β-lactamases and penicillin-binding proteins.
Drift in Susceptibility of
Neisseria gonorrhoeae
to Ciprofloxacin and Emergence of Therapeutic Failure
Authors: Ison Catherine A. , Woodford Patricia J. , Madders Helen , Claydon Elizabeth 
Published: October 2018

ABSTRACT

Ciprofloxacin, 500 mg, was introduced as the first-line therapy for gonorrhea at St. Mary’s Hospital, London, in 1989, when a surveillance program was initiated to detect the emergence of resistance. Isolates of
Neisseria gonorrhoeae
from consecutive patients attending the Jefferiss Wing, Genitourinary Medicine Clinic at St. Mary’s Hospital, between 1989 and 1997 have been tested for susceptibility to ciprofloxacin by using an agar dilution breakpoint technique. Isolates considered potentially resistant (MIC, >0.12 μg/ml) were further characterized by determination of the MICs of ciprofloxacin, nalidixic acid, and penicillin, auxotyped and serotyped, and screened for mutations in the DNA gyrase gene,
gyrA
, and the topoisomerase IV gene,
parC
. A total of 4,875 isolates were tested. While the majority of isolates were highly susceptible (MIC, ≤0.008 μg of ciprofloxacin/ml), there was a drift toward reduced susceptibility in
N. gonorrhoeae
isolated between 1993 and 1996 (
P
< 0.001). In 1997 this drift was reduced but remained above pre-1993 levels. Isolates from 18 patients were classed as potentially resistant (MIC, >0.12 μg/ml); all of these belonged to serogroup B, and NR/IB-1 was the most common auxotype/serovar class. The infections in 14 of the 18 patients were known to be acquired abroad, and 5 were known to result in therapeutic failure. The surveillance program has established that ciprofloxacin is still a highly effective antibiotic against
N. gonorrhoeae
in this population. However, it has identified a drift in susceptibility which may have resulted from increased usage of ciprofloxacin. High-level resistance has now emerged, although treatment failure is still uncommon.
The Epstein-Barr Virus Thymidine Kinase Does Not Phosphorylate Ganciclovir or Acyclovir and Demonstrates a Narrow Substrate Specificity Compared to the Herpes Simplex Virus Type 1 Thymidine Kinase
Authors: Gustafson Erik A. , Chillemi Antoinette C. , Sage David R. , Fingeroth Joyce D. 
Published: October 2018

ABSTRACT

The Epstein-Barr virus (EBV) thymidine kinase (TK) was expressed in mammalian 143B TK
−
cells to investigate its substrate specificity. The herpes simplex virus type 1 (HSV-1) TK was similarly expressed for comparison. Both viral TKs conferred a TK
+
phenotype on 143B TK
−
cells. The nucleoside analog ganciclovir (GCV) did not affect the growth of 143B EBV TK or 143B TK
−
cells but effectively killed 143B HSV-1 TK cells. Furthermore, lysates of 143B EBV TK cells could not phosphorylate GCV, which was confirmed by high-performance liquid chromatography. EBV TK, HSV-1 TK, and EBV TK N
−
, a truncated EBV TK missing 243 N-terminal amino acids, were purified as fusion proteins expressed in bacteria, and all had TK activity. In addition, EBV TK was observed to have a thymidylate kinase activity but could not phosphorylate GCV, acyclovir, or 2′-deoxycytidine. In competition assays, only nucleoside analogs of thymidine significantly inhibited thymidine phosphorylation by EBV TK, with the following rank order: 5-bromodeoxyuridine > zidovudine > stavudine > sorivudine. These results demonstrate that EBV TK substrate specificity is narrower than those of alphaherpesvirus TKs and that thymidine analogs may be the most suitable nucleoside antivirals to target the enzyme. Clinical implications for gammaherpesviruses are discussed.
Fluconazole versus
Candida albicans
: A Complex Relationship
Authors: Graybill John R. , Montalbo Eleanor , Kirkpatrick William R. , Luther Michael F. , Revankar Sanjay G. , Patterson Thomas F. 
Published: October 2018

ABSTRACT

A murine model of systemic candidiasis was used to assess the virulence of serial
Candida albicans
strains for which fluconazole MICs were increasing. Serial isolates from five patients with 17 episodes of oropharyngeal candidiasis were evaluated. The MICs for these isolates exhibited at least an eightfold progressive increase from susceptible (MIC < 8 μg/ml; range, 0.25 to 4 μg/ml) to resistant (MIC ≥ 16 μg/ml; range, 16 to ≥128 μg/ml). Virulence of the serial isolates from three of five patients showed a more than fivefold progressive decrease in the dose accounting for 50% mortality and was associated with development of fluconazole resistance. Low doses of fluconazole prolonged survival of mice infected with susceptible yeasts but failed to prolong survival following challenge with a resistant strain. In addition, a decreased burden of renal infection was noted in mice challenged with two of the three resistant strains. This was consistent with reduced virulence. Fluconazole did not further decrease the level of infection. In the isolates with a decrease in virulence, two exhibited overexpression of
CDR
, which encodes an ABC drug efflux pump. In contrast, serial isolates from the remaining two patients with the development of resistance did not demonstrate a change in virulence and fluconazole remained effective in prolonging survival, although significantly higher doses of fluconazole were required for efficacy. Resistant isolates from both of these patients exhibited overexpression of
MDR
. This study demonstrates that decreased virulence of serial
C. albicans
isolates is associated with increasing fluconazole MICs in some cases but not in others and shows that these low-virulence strains may not consistently cause infection.
Activities of New Fluoroquinolones against Fluoroquinolone-Resistant Pathogens of the Lower Respiratory Tract
Authors: Piddock Laura J. V. , Johnson M. , Ricci V. , Hill S. L. 
Published: October 2018

ABSTRACT

The activities of six new fluoroquinolones (moxifloxacin, grepafloxacin, gatifloxacin, trovafloxacin, clinafloxacin, and levofloxacin) compared with those of sparfloxacin and ciprofloxacin with or without reserpine (20 μg/ml) were determined for 19
Streptococcus pneumoniae
isolates, 5
Haemophilus
sp. isolates, and 10
Pseudomonas aeruginosa
isolates with decreased susceptibility to ciprofloxacin from patients with clinically confirmed lower respiratory tract infections. Based upon the MICs at which 50% of isolates were inhibited (MIC
50
s) and MIC
90
s, the most active agent was clinafloxacin, followed by (in order of decreasing activity) trovafloxacin, moxifloxacin, gatifloxacin, sparfloxacin, and grepafloxacin. Except for clinafloxacin (and gatifloxacin and trovafloxacin for
H. influenzae
), none of the new agents had improved activities compared with that of ciprofloxacin for
P. aeruginosa
and
H. influenzae
. A variable reserpine effect was observed for ciprofloxacin and
S. pneumoniae
; however, for 9 of 19 (47%) isolates the MIC of ciprofloxacin was decreased by at least fourfold, suggesting the presence of an efflux pump contributing to the resistance phenotype. The laboratory
parC
(Ser79) mutant strain of
S. pneumoniae
required eightfold more ciprofloxacin for inhibition than the wild-type strain, but there was no change in the MIC of sparfloxacin and only a 1-dilution increase in the MICs of the other agents. For efflux pump mutant
S. pneumoniae
the activities of all the newer agents, except for levofloxacin, were reduced. Except for clinafloxacin, all second-step laboratory mutants required at least 2 μg of all fluoroquinolones per ml for inhibition.
Prospective Randomized Comparison of Imipenem-Cilastatin and Piperacillin-Tazobactam in Nosocomial Pneumonia or Peritonitis
Authors: Jaccard C. , Troillet N. , Harbarth S. , Zanetti G. , Aymon D. , Schneider R. , Chiolero R. , Ricou B. , Romand J. , Huber O. , Ambrosetti P. , Praz G. , Lew D. , Bille J. , Glauser M. P. , Cometta A. 
Published: October 2018

ABSTRACT

Nosocomial pneumonia and acute peritonitis may be caused by a wide array of pathogens, and combination therapy is often recommended. We have previously shown that imipenem-cilastatin monotherapy was as efficacious as the combination of imipenem-cilastatin plus netilmicin in these two settings. The efficacy of imipenem-cilastatin is now compared to that of piperacillin-tazobactam as monotherapy in patients with nosocomial pneumonia or acute peritonitis. Three hundred seventy one patients with nosocomial pneumonia or peritonitis were randomly assigned to receive either imipenem-cilastatin (0.5 g four times a day) or piperacillin-tazobactam (4.5 g three times a day). Three hundred thirteen were assessable (154 with nosocomial pneumonia and 159 with peritonitis). For nosocomial pneumonia, clinical-failure rates in the piperacillin-tazobactam group (13 of 75 [17%]) and in the imipenem-cilastatin group (23 of 79 [29%]) were similar (
P
= 0.09), as were the numbers of deaths due to infection (6 in the imipenem-cilastatin group [8%], 7 in the piperacillin-tazobactam group [9%]) (
P
= 0.78). For acute peritonitis, clinical success rates were comparable (piperacillin-tazobactam, 72 of 76 [95%]; imipenem-cilastatin, 77 of 83 [93%]). For infections due to
Pseudomonas aeruginosa
, 45 patients had nosocomial pneumonia (21 in the piperacillin-tazobactam group and 24 in the imipenem-cilastatin group) and 10 had peritonitis (5 in each group). In the patients with nosocomial pneumonia, clinical failure was less frequent in the piperacillin-tazobactam group (2 of 21 [10%]) than in the piperacillin-cilastatin group (12 of 24 [50%]) (
P
= 0.004). Bacterial resistance to allocated regimen was the main cause of clinical failure (1 in the piperacillin-tazobactam group and 12 in the imipenem-cilastatin group). For the patients with peritonitis, no difference in clinical outcome was observed (five of five cured in each group). The overall frequencies of adverse events related to treatment in the two groups were similar (24 in the piperacillin-tazobactam group, 22 in the imipenem-cilastatin group). Diarrhea was significantly more frequent in the piperacillin-tazobactam group (10 of 24) than in the imipenem-cilastatin group (2 of 22). This study suggests that piperacillin-tazobactam monotherapy is at least as effective and safe as imipenem-cilastatin monotherapy in the treatment of nosocomial pneumonia or peritonitis. In
P. aeruginosa
pneumonia, piperacillin-tazobactam achieved a better clinical efficacy than imipenem-cilastatin, due to reduced development of microbiological resistance. Tolerance was comparable, with the exception of diarrhea, which was more frequent with piperacillin-tazobactam.
Antimicrobial Susceptibilities of
Porphyromonas gingivalis
,
Prevotella intermedia
, and
Prevotella nigrescens
spp. Isolated in Spain
Authors: Andrés María T. , Chung Whasun O. , Roberts Marilyn C. , Fierro José F. 
Published: October 2018

ABSTRACT

The susceptibilities of 143
Porphyromonas gingivalis
,
Prevotella intermedia
, and
Prevotella nigrescens
isolates to 18 antimicrobial agents were tested. All
P. gingivalis
isolates were susceptible. In contrast, some
Prevotella
spp. (17%) were resistant to β-lactams, erythromycin, clindamycin, or tetracycline and carried resistance genes,
ermF
or
tetQ
, or β-lactamases.
Activity of HMR 3647 Compared to Those of Five Agents against
Haemophilus influenzae
and
Moraxella catarrhalis
by MIC Determination and Time-Kill Assay
Authors: Pankuch Glenn A. , Hoellman Dianne B. , Lin Gengrong , Bajaksouzian Saralee , Jacobs Michael R. , Appelbaum Peter C. 
Published: October 2018

ABSTRACT

The microdilution MICs of HMR 3647, erythromycin A, azithromycin, clarithromycin, roxithromycin, and pristinamycin against 50/90% of 249
Haemophilus influenzae
and 50
Moraxella catarrhalis
isolates were 2/4, 0.06/0.125; 8/16, 0.25/0.25; 2/4, 0.06/0.125; 16/16, 0.25/0.25; 32/>32, 1/2; and 2/4, 0.5/0.5 μg/ml. Azithromycin was bactericidal against all 10
H. influenzae
and 3 of 5
M. catarrhalis
isolates and HMR 3647, erythromycin A, clarithromycin, roxithromycin, and pristinamycin were bacteriostatic, against all 15 strains after 24 h at the MIC.
Evaluation of Once-Weekly Therapy for Tuberculosis Using Isoniazid plus Rifamycins in the Mouse Aerosol Infection Model
Authors: Brooks Jason V. , Orme Ian M. 
Published: October 2018

ABSTRACTOnce-weekly therapy with combinations of isoniazid plus a rifamycin was tested in the mouse low-dose aerosol infection model against two strains ofMycobacterium tuberculosis. Combinations of isoniazid and rifalizil and isoniazid and rifapentine were both highly effective. These animal model data thus support the evaluation of these regimens under clinical conditions.