bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the Microbiological Efficacy of a Single 2-Gram Dose of Extended-Release Azithromycin by Population Pharmacokinetics and Simulation in Japanese Patients with Gonococcal Urethritis
Authors: Soda Midori , Ito Shin , Matsumaru Naoki , Nakamura Sakiko , Nagase Izumi , Takahashi Hikari , Ohno Yuta , Yasuda Mitsuru , Yamamoto Miho , Tsukamoto Katsura , Itoh Yoshinori , Deguchi Takashi , Kitaichi Kiyoyuki 
Published: October 2017

ABSTRACT

The objective of this study was to analyze the relationship between the pharmacokinetic (PK)/pharmacodynamic (PD) parameters of a single 2-g dose of extended-release formulation of azithromycin (AZM-SR) and its microbiological efficacy against gonococcal urethritis. Fifty male patients with gonococcal urethritis were enrolled in this study. In 36 patients, the plasma AZM concentrations were measured using liquid chromatography-tandem mass spectrometry, the AZM MIC values for the
Neisseria gonorrhoeae
isolates were determined, and the microbiological outcomes were assessed. AZM-SR monotherapy eradicated
N. gonorrhoeae
in 30 (83%) of the 36 patients. AZM MICs ranged from 0.03 to 2 mg/liter. The mean value of the area under the concentration-time curve (AUC), estimated by population PK analysis using a two-compartment model, was 20.8 mg · h/liter. Logistic regression analysis showed that the PK/PD target value required to predict an
N. gonorrhoeae
eradication rate of ≥95% was a calculated AUC/MIC of ≥59.5. The AUC/MIC value was significantly higher in patients who achieved microbiological cure than in patients who achieved microbiological failure. Monte Carlo simulation using this MIC distribution revealed that the probability that AZM-SR monotherapy would produce an AUC/MIC exceeding the AUC/MIC target of 59.5 was 47%. Furthermore, the MIC distribution for strains isolated in this study was mostly consistent with that for strains currently circulating in Japan. In conclusion, in Japan, AZM-SR monotherapy may not be effective against gonococcal urethritis. Therefore, use of a single 2-g dose of AZM-SR either with or without other antibiotics could be an option to treat gonococcal urethritis if patients are allergic to ceftriaxone and spectinomycin or are diagnosed to be infected with an AZM-sensitive strain.
Evaluation of Antifungal Efficacy of Three New Cyclic Lipopeptides of the Class Bacillomycin from Bacillus subtilis RLID 12.1
Authors: Ramachandran Ramya , Shrivastava Manjari , Narayanan Namitha N. , Thakur Ram Lal , Chakrabarti Arunaloke , Roy Utpal 
Published: October 2017

ABSTRACT

New lipopeptide homologues (AF
3
, AF
4
, and AF
5
) with antifungal activities against
Candida
and
Cryptococcus
spp. were purified from a cell-free supernatant of
Bacillus subtilis
RLID 12.1. The lipopeptides AF
3
, AF
4
, and AF
5
were identified with the same peptide sequence Asn-Pro-Tyr-Asn-Gln-Thr-Ser with variations in the fatty acid branching type and chain length (
anteiso
-C
17
,
iso
-C
17
, and
iso
-C
18
, respectively). Upon comparing the three homologues for MICs against 81
Candida
(
n
= 64) and
Cryptococcus
(
n
= 17) clinical isolates and their cytotoxicities, we found that AF
4
was the most promising antifungal lipopeptide, since it demonstrated 100% inhibition at geometric mean MICs of 3.31, 3.41, 3.48, and 2.83 μg/ml against
Candida albicans
,
Candida tropicalis
,
Candida auris
, and
Cryptococcus neoformans
, respectively, with low hemolysis values (<6%) and 50% inhibitory concentrations (13.31 μg/ml). The additive effects among the homologues AF
3
, AF
4
, and AF
5
were evaluated against three
Candida
species, along with the cytotoxicity studies. Five combinations exhibited good additive interaction effects: AF
3
/AF
4
(at corresponding concentrations of 4 and 4 μg/ml [4/4 μg/ml]), AF
3
/AF
5
(4/4 μg/ml), AF
3
/AF
5
(2/4 μg/ml), AF
4
/AF
5
(4/4 μg/ml), and AF
4
/AF
5
(2/4 μg/ml) in planktonic cell inhibition and AF
3
/AF
4
(4/4 μg/ml), AF
3
/AF
5
(4/4 μg/ml), and AF
3
/AF
5
(2/4 μg/ml) in the inhibition of biofilm formation. However, combinations AF
3
/AF
4
and AF
3
/AF
5
, which showed >70% cell survival with low hemolysis (<5%), were found to be comparatively effective. We describe here the additive effects of lipopeptide homologues showing reduced cytotoxicity against mammalian cells; these combinations might serve as a potent antibiofilm-forming substitute.
Severe Infusion-Related Adverse Events and Renal Failure in Patients Receiving High-Dose Intravenous Polymyxin B
Authors: John Josiane F. , Falci Diego R. , Rigatto Maria Helena , Oliveira Renata D. , Kremer Thaysa G. , Zavascki Alexandre P. 
Published: October 2017

ABSTRACT

The use of very high doses of polymyxin B (PMB) against carbapenem-resistant Gram-negative bacilli has been addressed in
in vitro
experiments as a strategy to improve bacterial killing and suppress resistance emergence. However, the toxicities of very high doses in patients are unknown. We conducted a retrospective cohort study assessing patients receiving PMB at >3 mg/kg of body weight/day or a total dose of ≥250 mg/day. The main outcomes were severe infusion-related adverse events according to the Common Terminology Criteria for Adverse Events and the renal failure category of RIFLE criteria for acute kidney injury (AKI) during treatment. A total of 222 patients were included for analysis of infusion-related events. The mean PMB dose was 3.61 ± 0.97 mg/kg/day (median total dose/day = 268 mg). Severe infusion-related adverse events occurred in two patients, resulting in an incidence of 0.9% (95% confidence interval, 0.2 to 3.2%); one was classified as a life-threatening adverse event, and one was classified as a severe adverse event. Renal failure was analyzed in 115 patients, and 25 (21.7%) patients presented renal failure (54 [47.0%] developed any degree of AKI, categorized as risk [27.8%], injury [25.9%], and failure [46.3%]). Treatment with a vasoactive drug, concomitant treatment with nephrotoxic drugs, and baseline creatinine clearance were independent risk factors for renal failure. Neither the PMB daily dose scaled by body weight nor the total daily dose was associated with renal failure. The in-hospital mortality rate was 60% (134 patients): 26% of deaths (57 patients) occurred during treatment, and none occurred during infusion. Our data suggest that high-dose schemes have an acceptable safety profile and could be further tested in clinical trials assessing strategies to improve patient outcomes and minimize the emergence of PMB resistance.
Verapamil Increases the Bioavailability and Efficacy of Bedaquiline but Not Clofazimine in a Murine Model of Tuberculosis
Authors: Xu Jian , Tasneen Rokeya , Peloquin Charles A. , Almeida Deepak V. , Li Si-Yang , Barnes-Boyle Kala , Lu Yu , Nuermberger Eric 
Published: October 2017

ABSTRACT

Drug efflux pumps play important roles in intrinsic and acquired drug resistance. Verapamil, an efflux inhibitor that enhances the activity of bedaquiline, clofazimine, and other drugs against
Mycobacterium tuberculosis
, has been proposed as a potential adjunctive agent for treatment of tuberculosis (TB). However, the extent to which verapamil enhances
in vivo
efficacy by inhibiting bacterial efflux pumps versus inhibiting mammalian drug transporters to improve oral bioavailability has not been delineated. We found that verapamil potentiated the
in vitro
activity of bedaquiline and clofazimine against
M. tuberculosis
clinical isolates, including those harboring
rv0678
mutations. Verapamil increased the efficacy of bedaquiline in a murine TB model by the same extent to which it increased systemic bedaquiline exposure. However, verapamil showed no effect on the oral bioavailability or efficacy of clofazimine in mice. The addition of verapamil increased the sterilizing activity of a regimen composed of bedaquiline, clofazimine, and pyrazinamide. These results confirm that verapamil has adjunctive activity
in vivo
, but they also demonstrate that the adjunctive effect is likely due to enhanced systemic exposure to companion drugs via effects on mammalian transporters, rather than inhibition of bacterial pumps. Therefore, there may be no advantage to administering verapamil versus increasing the doses of companion drugs.
Meropenem-Vaborbactam Resistance Selection, Resistance Prevention, and Molecular Mechanisms in Mutants of KPC-Producing Klebsiella pneumoniae
Authors: Sun Dongxu , Rubio-Aparicio Debora , Nelson Kirk , Dudley Michael N. , Lomovskaya Olga 
Published: October 2017

ABSTRACT

Vaborbactam (formerly RPX7009) is a new β-lactamase inhibitor based on a cyclic boronic acid pharmacophore with potent inhibitory activity against

K
lebsiella
p
neumoniae

c
arbapenemases (KPC). It has been developed in combination with meropenem. The objective of these studies was to identify the concentrations of both agents associated with the selection or prevention of single-step mutations leading to reduced sensitivity to the combination and to characterize the selected mutations. Eighteen strains of KPC-producing
Klebsiella pneumoniae
with various degrees of sensitivity to meropenem (MICs, 8 to 512 μg/ml) and meropenem-vaborbactam (MICs, ≤0.06 to 32 μg/ml) and preexisting resistance mechanisms were selected from a worldwide collection of isolates recovered from surveillance studies, emphasizing strains for which MICs were in the upper range of the meropenem-vaborbactam MIC distribution. Meropenem and vaborbactam at 8 μg/ml each suppressed the drug resistance mutation frequency to <1 × 10
−8
in 77.8% (14/18) of strains, and all strains were inhibited when the meropenem concentration was increased to 16 μg/ml. Mutants selected at lower drug concentrations showed phenotypes associated with previously described carbapenem resistance mechanisms, including
ompK36
inactivation in mutants selected from OmpK36-proficient strains and an increased
bla
KPC
gene copy number in strains with partially functional
ompK36
. No mutations in the coding region of
bla
KPC
were identified. These data indicate that the selection of mutants with reduced sensitivity to meropenem-vaborbactam from KPC-producing
Klebsiella pneumoniae
strains is associated with previously described mechanisms involving porin mutations and the increase in the
bla
KPC
gene copy number and not changes in the KPC enzyme and can be prevented by the drug concentrations achieved with optimal dosing of the combination.
The Genital Tract Virulence Factor pGP3 Is Essential for Chlamydia muridarum Colonization in the Gastrointestinal Tract
Authors: Shao Lili , Zhang Tianyuan , Melero Jose , Huang Yumeng , Liu Yuanjun , Liu Quanzhong , He Cheng , Nelson David E. , Zhong Guangming 
Published: October 2017

ABSTRACTThe cryptic plasmid is essential forChlamydia muridarumdissemination from the genital tract to the gastrointestinal (GI) tract. Following intravaginal inoculation, aC. muridarumstrain deficient in plasmid-encoded pGP3 or pGP4 but not pGP5, pGP7, or pGP8 failed to spread to the mouse gastrointestinal tract, although mice infected with these strains developed productive genital tract infections. pGP3- or pGP4-deficient strains also failed to colonize the gastrointestinal tract when delivered intragastrically. pGP4 regulates pGP3, while pGP3 does not affect pGP4 expression, indicating that pGP3 is critical forC. muridarumcolonization of the gastrointestinal tract. Mutants deficient in GlgA, a chromosome-encoded protein regulated by pGP4, also consistently colonized the mouse gastrointestinal tract. Interestingly,C. muridarumcolonization of the gastrointestinal tract positively correlated with pathogenicity in the upper genital tract. pGP3-deficientC. muridarumstrains did not induce hydrosalpinx or spread to the GI tract even when delivered to the oviduct by intrabursal inoculation. Thus, the current study not only has revealed that pGP3 is a novel chlamydial colonization factor in the gastrointestinal tract but also has laid a foundation for investigating the significance of gastrointestinalChlamydia.
Studies of Pseudomonas aeruginosa Mutants Indicate Pyoverdine as the Central Factor in Inhibition of Aspergillus fumigatus Biofilm
Authors: Sass Gabriele , Nazik Hasan , Penner John , Shah Hemi , Ansari Shajia Rahman , Clemons Karl V. , Groleau Marie-Christine , Dietl Anna-Maria , Visca Paolo , Haas Hubertus , Déziel Eric , Stevens David A. 
Published: October 2017

ABSTRACT

Pseudomonas aeruginosa
and
Aspergillus fumigatus
are common opportunistic bacterial and fungal pathogens, respectively. They often coexist in airways of immunocompromised patients and individuals with cystic fibrosis, where they form biofilms and cause acute and chronic illnesses. Hence, the interactions between them have long been of interest and it is known that
P. aeruginosa
can inhibit
A. fumigatus
in vitro
. We have approached the definition of the inhibitory
P. aeruginosa
molecules by studying 24
P. aeruginosa
mutants with various virulence genes deleted for the ability to inhibit
A. fumigatus
biofilms. The ability of
P. aeruginosa
cells or their extracellular products produced during planktonic or biofilm growth to affect
A. fumigatus
biofilm metabolism or planktonic
A. fumigatus
growth was studied in agar and liquid assays using conidia or hyphae. Four mutants, the
pvdD pchE
,
pvdD
,
lasR rhlR
, and
lasR
mutants, were shown to be defective in various assays. This suggested the
P. aeruginosa
siderophore pyoverdine as the key inhibitory molecule, although additional quorum sensing-regulated factors likely contribute to the deficiency of the latter two mutants. Studies of pure pyoverdine substantiated these conclusions and included the restoration of inhibition by the pyoverdine deletion mutants. A correlation between the concentration of pyoverdine produced and antifungal activity was also observed in clinical
P. aeruginosa
isolates derived from lungs of cystic fibrosis patients. The key inhibitory mechanism of pyoverdine was chelation of iron and denial of iron to
A. fumigatus
.

IMPORTANCE
Interactions between human pathogens found in the same body locale are of vast interest. These interactions could result in exacerbation or amelioration of diseases. The bacterium
Pseudomonas aeruginosa
affects the growth of the fungus
Aspergillus fumigatus
. Both pathogens form biofilms that are resistant to therapeutic drugs and host immunity.
P. aeruginosa
and
A. fumigatus
biofilms are found
in vivo
, e.g., in the lungs of cystic fibrosis patients. Studying 24
P. aeruginosa
mutants, we identified pyoverdine as the major anti-
A. fumigatus
compound produced by
P. aeruginosa
. Pyoverdine captures iron from the environment, thus depriving
A. fumigatus
of a nutrient essential for its growth and metabolism. We show how microbes of different kingdoms compete for essential resources. Iron deprivation could be a therapeutic approach to the control of pathogen growth.
A Bacteriophage Capsid Protein Is an Inhibitor of a Conserved Transcription Terminator of Various Bacterial Pathogens
Authors: Ghosh Gairika , Reddy Jayavardhana , Sambhare Susmit , Sen Ranjan 
Published: October 2017

ABSTRACT

Rho is a hexameric molecular motor that functions as a conserved transcription terminator in the majority of bacterial species and is a potential drug target. Psu is a bacteriophage P4 capsid protein that inhibits
Escherichia coli
Rho by obstructing its ATPase and translocase activities. In this study, we explored the anti-Rho activity of Psu for Rho proteins from different pathogens. Sequence alignment and homology modeling of Rho proteins from pathogenic bacteria revealed the conserved nature of the Psu-interacting regions in all these proteins. We chose Rho proteins from various pathogens, including
Mycobacterium smegmatis
,
Mycobacterium bovis
,
Mycobacterium tuberculosis
,
Xanthomonas campestris
,
Xanthomonas oryzae
,
Corynebacterium glutamicum
,
Vibrio cholerae
,
Salmonella enterica
, and
Pseudomonas syringae
. The purified recombinant Rho proteins of these organisms showed variable rates of ATP hydrolysis on poly(rC) as the substrate and were capable of releasing RNA from the
E. coli
transcription elongation complexes. Psu was capable of inhibiting these two functions of all these Rho proteins.
In vivo
pulldown assays revealed direct binding of Psu with many of these Rho proteins.
In vivo
expression of
psu
induced killing of
M. smegmatis
,
M. bovis
,
X. campestris
, and
E. coli
expressing
S. enterica
Rho indicating Psu-induced inhibition of Rho proteins of these strains under physiological conditions. We propose that the “universal” inhibitory function of the Psu protein against the Rho proteins from both Gram-negative and Gram-positive bacteria could be useful for designing peptides with antimicrobial functions and that these peptides could contribute to synergistic antibiotic treatment of the pathogens by compromising the Rho functions.

IMPORTANCE
Bacteriophage-derived protein factors modulating different bacterial processes could be converted into unique antimicrobial agents. Bacteriophage P4 capsid protein Psu is an inhibitor of the
E. coli
transcription terminator Rho. Here we show that apart from antagonizing
E. coli
Rho, Psu is able to inhibit Rho proteins from various phylogenetically unrelated Gram-negative and Gram-positive pathogens. Upon binding to these Rho proteins, Psu inhibited them by affecting their ATPase and RNA release functions. The expression of Psu
in vivo
kills various pathogens, such as
Mycobacterium
and
Xanthomonas
species. Hence, Psu could be useful for identifying peptide sequences with anti-Rho activities and might constitute part of synergistic antibiotic treatment against pathogens.
Thiol Starvation Induces Redox-Mediated Dysregulation of Escherichia coli Biofilm Components
Authors: Hufnagel David A. , Price Janet E. , Stephenson Rachel E. , Kelley Jesse , Benoit Matthew F. , Chapman Matthew R. 
Published: October 2017

ABSTRACT

A hallmark of bacterial biofilms is the production of an
e
xtra
c
ellular
m
atrix (ECM) that encases and protects the community from environmental stressors. Biofilm formation is an integral portion of the
u
ro
p
athogenic

E
scherichia
c
oli

(UPEC) life cycle. Approximately 2% of UPEC isolates are cysteine auxotrophs. Here, we investigated how cysteine homeostasis impacted UPEC UTI89 strain biofilm formation and, specifically, the production of the ECM components curli and cellulose. Cysteine auxotrophs produced less cellulose and slightly more curli compared to wild-type (WT) strains, and cysteine auxotrophs formed smooth, nonrugose colonies. Cellulose production was restored in cysteine auxotrophs when YfiR was inactivated. YfiR is a redox-sensitive regulator of the diguanylate cyclase, YfiN. The production of curli, a temperature-regulated appendage, was independent of temperature in UTI89 cysteine auxotrophs. In a screen of UPEC isolates, we found that ∼60% of UPEC cysteine auxotrophs produced curli at 37°C, but only ∼2% of cysteine prototrophic UPEC isolates produced curli at 37°C. Interestingly, sublethal concentrations of amdinocillin and trimethoprim-sulfamethoxazole inhibited curli production, whereas strains auxotrophic for cysteine continued to produce curli even in the presence of amdinocillin and trimethoprim-sulfamethoxazole. The dysregulation of ECM components and resistance to amdinocillin in cysteine auxotrophs may be linked to hyperoxidation, since the addition of exogenous cysteine or glutathione restored WT biofilm phenotypes to mutants unable to produce cysteine and glutathione.

IMPORTANCE
Uropathogenic
Escherichia coli
(UPEC) bacteria are the predominant causative agent of urinary tract infections (UTIs). UTIs account for billions of dollars of financial burden annually to the health care industry in the United States. Biofilms are an important aspect of the UPEC pathogenesis cascade and for the establishment of chronic infections. Approximately 2% of UPEC isolates from UTIs are cysteine auxotrophs, yet there is relatively little known about the biofilm formation of UPEC cysteine auxotrophs. Here we show that cysteine auxotrophs have dysregulated biofilm components due to a change in the redox state of the periplasm. Additionally, we show the relationship between cysteine auxotrophs, biofilms, and antibiotics frequently used to treat UTIs.
Stress Introduction Rate Alters the Benefit of AcrAB-TolC Efflux Pumps
Authors: Langevin Ariel M. , Dunlop Mary J. 
Published: October 2017

ABSTRACTStress tolerance studies are typically conducted in an all-or-none fashion. However, in realistic settings—such as in clinical or metabolic engineering applications—cells may encounter stresses at different rates. Therefore, how cells tolerate stress may depend on its rate of appearance. To address this, we studied how the rate of stress introduction affects bacterial stress tolerance by focusing on a key stress response mechanism. Efflux pumps, such as AcrAB-TolC ofEscherichia coli, are membrane transporters well known for the ability to export a wide variety of substrates, including antibiotics, signaling molecules, and biofuels. Although efflux pumps improve stress tolerance, pump overexpression can result in a substantial fitness cost to the cells. We hypothesized that the ideal pump expression level would involve a rate-dependent trade-off between the benefit of pumps and the cost of their expression. To test this, we evaluated the benefit of the AcrAB-TolC pump under different rates of stress introduction, including a step, a fast ramp, and a gradual ramp. Using two chemically diverse stresses, the antibiotic chloramphenicol and the jet biofuel precursor pinene, we assessed the benefit provided by the pumps. A mathematical model describing these effects predicted the benefit as a function of the rate of stress introduction. Our findings demonstrate that as the rate of introduction is lowered, stress response mechanisms provide a disproportionate benefit to pump-containing strains, allowing cells to survive beyond the original inhibitory concentrations.IMPORTANCEEfflux pumps are ubiquitous in nature and provide stress tolerance in the cells of species ranging from bacteria to mammals. Understanding how pumps provide tolerance has far-reaching implications for diverse fields, from medicine to biotechnology. Here, we investigated how the rate of stressor appearance impacts tolerance. We focused on two distinct substrates of AcrAB-TolC efflux pumps, the antibiotic chloramphenicol and the biofuel precursor pinene. Interestingly, tolerance is highly dependent on the rate of stress introduction. Therefore, it is important to consider not only the total quantity of a stressor but also the rate at which it is applied. The implications of this work are significant because environments are rarely static; antibiotic concentrations change during dosing, and metabolic engineering processes change with time.