Fluoroquinolone antimicrobial agents

Use of fluoroquinolones and the risk of aortic and mitral regurgitation: A nationwide case-crossover study

BACKGROUND

Recently, there have been conflicting results reporting an increased risk of AR or MR associated with oral fluoroquinolones (FQs).This study investigated whether the use of FQs increases the risk of mitral regurgitation (MR) or aortic regurgitation (AR).

METHODS

A retrospective cohort study was conducted by using the Taiwan National Health Insurance research database. A unidirectional case-crossover design without selecting controls from an external population was adopted in this study. A total of 26,650 adult patients with new onset of AR or MR between January 1, 2000, and December 31, 2012, were identified. The risk of outcomes was compared between the hazard period and one of the randomly selected referent periods of the same individuals.

RESULTS

Before exclusion of pneumonia diagnosed within 2 months before the index date, patients who took FQs had a significantly greater risk of AR or MR (adjusted odds ratio [aOR] 1.51, 95% confidence interval [CI] 1.30-1.77), any AR (combined AR and MR) (aOR 1.50, 95% CI 1.10-2.04), and any MR (combined AR and MR) (aOR 1.37, 95% CI 1.16-1.62). After exclusion of pneumonia, FQs exposure remained significantly associated with a greater risk of MR (aOR 1.38, 95% CI 1.17-1.62) and any MR (aOR 1.25, 95% CI 1.05-1.48).

CONCLUSIONS

The findings suggested that patients treated with FQs could be warned about the potential risk for MR even after considering the possibility of protopathic bias. Reducing unnecessary FQs prescriptions may be considered to reduce the risk of valvular heart disease.

External carbon source as a viable tool for controlling antibiotics and antibiotic resistance genes (ARGs) in effluent: Influence on antibiotic removal and ARGs dissemination

Fluoroquinolone antibiotics and antibiotic resistance genes (ARGs) regarded as emerging contaminants were poorly removed in conventional wastewater treatment plants (WWTPs). Nitrogen-containing heterocyclic organics were found to be biodegraded through denitrification co-metabolism. The feasibility to enhance antibiotics removal efficiency in WWTPs through denitrification co-metabolism needs to be further verified. Meanwhile, due to significant correlation between ARGs profiles and nitrogen removal that was previously observed, the dissemination of ARGs during denitrification was worthy of in-depth understanding. Herein, the antibiotic removal and ARGs dissemination in denitrification co-metabolism condition were investigated with different denitrifying consortiums that acclimated under different conditions in terms of carbon source and the exposure of Ofloxacin (OFL). The results suggest that the removal of OFL can be enhanced by the denitrification co-metabolism. The tolerance to OFL is different among various denitrifying communities. For the denitrifying consortiums acclimated with methanol, long-term exposure to trace OFL (1 μg/L) could reduce the capabilities of removal and tolerance to OFL. On the contrary, those acclimated with sodium acetate (NaAc), the capabilities of removal and tolerance to OFL, were enhanced by long-term exposure to trace OFL. According to the quantitative determination to 384 target genes with high-throughput quantitative PCR, the abundance of ARGs in consortiums greatly increased when exposed to OFL at the concentration of comparable to sewage, which was also much larger than that acclimated with methanol. It can be confirmed and supported by DNA sequencing results that the antibiotic removal and the dissemination of ARGs were determined by microbial community that could be shaped with carbon source. These conclusions suggest that selecting the right external carbon source can be a useful strategy for WWTPs to control antibiotics and ARGs in the effluent. From a new perspective on mitigating ARGs dissemination, NaAc was not an appropriate carbon source.

In vitro and ex vivo activity of the fluoroquinolone DC-159a against mycobacteria

Antimicrobial resistance is a global health problem. In 2021, it was estimated almost half a million of multidrug-resistant tuberculosis (MDR-TB) cases. Besides, non-tuberculous mycobacteria (NTM) are highly resistant to several drugs and the emergence of fluoroquinolone (FQ) resistant M. tuberculosis (Mtb) is also a global concern making treatments difficult and with variable outcome. The aim of this study was to evaluate the activity of the FQ, DC-159a, against Mtb and NTM and to explore the cross-resistance with the currently used FQs.A total of 12 pre-extensively drug-resistant (XDR) Mtb, 2 XDR, 36 fully drug susceptible strains and 41 NTM isolates were included to estimate the in vitro activity of DC-159a, moxifloxacin (MOX) and levofloxacin (LX), using minimal inhibitory and bactericidal concentration (MIC and MBC). The activity inside the human macrophages and pulmonary epithelial cells were also determined.DC-159a was active in vitro and ex vivo against mycobacteria. Besides, it was more active than MOX/LX. Moreover, no cross-resistance was evidenced between DC-159a and LX/MOX as DC-159a could inhibit Mtb and MAC strains that were already resistant to LX/MOX.DC-159a could be a possible candidate in new therapeutic regimens for MDR/ XDR-TB and mycobacterioses cases.

Photoisomerization and Light-Controlled Antibacterial Activity of Fluoroquinolone-Azoisoxazole Hybrids

Photopharmacology holds a huge untapped potential to locally treat diseases involving photoswitchable drugs via the elimination of drugs' off-target effects. The growth of this field has created a pressing demand to develop such light-active drugs. We explored the potential for creating photoswitchable antibiotic hybrids by attaching pharmacophores norfloxacin/ciprofloxacin and azoisoxazole (photoswitch). All compounds exhibited a moderate to a high degree of bidirectional photoisomerization, long thermal cis half-lives, and impressive photoresistance. Gram-negative pathogens were found to be insensitive to these hybrids, while against Gram-positive pathogens, all hybrids in their trans states exhibited antibacterial activity that is comparable to that of the parent drugs. Notably, the toxicity of the irradiated hybrid 6 was found to be 2-fold lower than the nonirradiated trans isomer, indicating that the pre-inactivated cis-enriched drug can be employed for the site-specific treatment of bacterial infection using light, which could potentially eliminate the unwanted exposure of toxic antibiotics to both beneficial and untargeted harmful microbes in our body. Molecular docking revealed different binding affinity of the cis and trans isomers with the topoisomerase IV enzyme, due to their different shapes.

Fluoroquinolones upregulate insulin-like growth factor-binding protein 3, inhibit cell growth and insulin-like growth factor signaling

Fluoroquinolones (FQs), commonly known for their antibiotic properties, exhibit additional pharmacological potential with anti-proliferative effects on various malignant cell types and immunomodulatory responses. Despite these observed effects, the precise mechanisms of action remain elusive. This study elucidates the biological impact of FQs on insulin-like growth factor-binding protein 3 (IGFBP-3) productions in a p53-dependent manner. Cultured cells and mouse models treated with FQs demonstrated increased IGFBP-3 mRNA expression and protein secretion. The FQ-induced IGFBP-3 was identified to impede cell growth by inhibiting IGF-I signaling and exerting effects through an IGF-independent pathway. Notably, FQ-mediated suppression of cell proliferation was reversed in p53-null and p53 knockdown cells, suggesting the pivotal role of p53 in FQ-induced IGFBP-3 production and IGFBP-3-mediated growth inhibition. Additionally, ciprofloxacin, a clinically used FQ, exhibited the induction of tumor cell apoptosis and attenuation of tumor growth in a syngeneic mouse hepatocellular carcinoma (HCC) model. These findings unveil a novel mechanism through which FQs act as anti-proliferative agents, prompting further exploration of their potential utility or derivative compounds in cancer treatment and prevention.

Fluoroquinolones do not provide added risk of out-of-hospital cardiac arrest: a nationwide study

AIM

Conflicting results have been reported regarding the association between fluoroquinolones (FQs) and the risk of out-of-hospital cardiac arrest (OHCA). In particular, it has not become clear whether OHCA in FQ users is related to the inherent comorbidities or whether there is a direct pro-arrhythmic effect of FQs. Therefore, we studied the relation between FQs and OHCA in the general population.

METHODS

Through Danish nationwide registries, we conducted a nested case-control study with OHCA cases of presumed cardiac causes and age/sex/OHCA date-matched non-OHCA controls from the general population. Conditional logistic regression models with adjustments for well-known risk factors of OHCA were employed to estimate the OR with 95% CI of OHCA comparing FQs with amoxicillin.

RESULTS

The study population consisted of 46 578 OHCA cases (mean: 71 years (SD: 14.40), 68.8% men) and 232 890 matched controls. FQ was used by 276 cases and 328 controls and conferred no increase in the odds of OHCA compared with amoxicillin use after controlling for the relevant confounders (OR: 0.91 (95% CI: 0.71 to 1.16)). The OR of OHCA associated with FQ use did not vary significantly by age (OR≤65: 0.96 (95% CI: 0.53 to 1.74), OR>65: 0.88 (95% CI: 0.67 to 1.16), p value interaction=0.7818), sex (ORmen: 0.96 (95% CI: 0.70 to 1.31), ORwomen: 0.80 (95% CI: 0.53 to 1.20), p value interaction=0.9698) and pre-existing cardiovascular disease (ORabsent: 1.02 (95% CI: 0.57 to 1.82), ORpresent: 0.98 (95% CI: 0.75 to 1.28), p value interaction=0.3884), including heart failure (ORabsent: 0.93 (95% CI: 0.72 to 1.22), ORpresent: 1.11 (95% CI: 0.61 to 2.02), p value interaction=0.7083) and ischaemic heart disease (ORabsent: 0.85 (95% CI: 0.64 to 1.12), ORpresent: 1.38 (95% CI: 0.86 to 2.21), p value interaction=0.6230).

CONCLUSION

Our findings do not support an association between FQ exposure and OHCA in the general population. This lack of association was consistent in men and women, in all age categories, and in the presence or absence of cardiovascular disease.

Fabrication of zwitterionic magnetic microporous organic network for efficient extraction of fluoroquinolone antibiotics from meat samples

A zwitterionic magnetic microporous organic network (MMON-SO3H-NH2) with numerous amino and sulfonic acid ion-pare binding sites was designed and synthesized for efficient magnetic solid-phase extraction (MSPE) of fluoroquinolones (FQs) from meat samples. The core-shell MMON-SO3H-NH2 offered large specific surface area, rapid magnetic responsiveness, good stability, and multiple binding sites for FQs. The density functional theory and independent gradient model evaluations confirmed hydrogen bonding, π-π and ion-pair interactions between MMON-SO3H-NH2 and FQs. Under the optimal conditions, the established MMON-SO3H-NH2-MSPE-HPLC-UV method gave wide linear range (0.15-1000 μg L-1), low limits of detection (0.05-4.5 μg L-1) and limits of quantitation (0.15-13 μg L-1), and high enrichment factors (82.1-99.6) using 3 mg of adsorbent. This work demonstrates that the preparation of zwitterionic MONs is an efficient way to promote the extraction performance of MONs for zwitterionic targets and provides an effective sample pretreatment method for enriching and monitoring FQs in complex food matrices.

Oral fluoroquinolones and risk of aortic aneurysm or dissection: A nationwide population-based propensity score-matched cohort study

STUDY OBJECTIVE

To investigate risk of aortic aneurysm or dissection in patients using oral fluoroquinolones compared to those using macrolides in real-world clinical practice among a large US general population.

DESIGN

Retrospective cohort study design.

DATA SOURCE

MarketScan commercial and Medicare supplemental databases.

PATIENTS

Adults patients with at least one prescription fill for fluoroquinolone or macrolide antibiotics.

INTERVENTION

Fluoroquinolone or macrolide antibiotics.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was estimated incidence of aortic aneurysm or dissection associated with the use of fluoroquinolones compared with macrolides during a 60-day follow-up period in a 1:1 propensity score-matched cohort. We identified 3,174,620 patients (1,587,310 in each group) after 1:1 propensity score matching. Crude incidence of aortic aneurysm or dissection was 1.9 cases per 1000 person-years among fluoroquinolone users and 1.2 cases per 1000 person-years among macrolide users. In multivariable Cox regression, compared with macrolides, the use of fluoroquinolones was associated with an increased risk of aortic aneurysm or dissection (aHR: 1.34; 95% CI: 1.17-1.54). The association was primarily driven by a high incidence of aortic aneurysm cases (95.8%). Results of sensitivity (e.g., fluoroquinolone exposure ranging from 7 to 14 days (aHR: 1.47; 95% CI: 1.26-1.71)) and subgroup analyses (e.g., ciprofloxacin (aHR: 1.26; 95% CI: 1.07-1.49) and levofloxacin (aHR: 1.44; 95% CI: 1.19-1.52)) remained consistent with main findings.

CONCLUSIONS

Fluoroquinolone use was associated with a 34% increased risk of aortic aneurysm or dissection compared with macrolide use among a general US population.

Fluoroquinolones Are Useful as Directed Treatment for Complicated UTI in a Setting with a High Prevalence of Quinolone-Resistant Microorganisms

Fluoroquinolones (FQs) have been widely used for treating urinary tract infections (UTIs); however, the increasing emergence of resistant strains has compromised their use. We aimed to know the usefulness of FQs for the treatment of community-acquired UTI in a setting with a high prevalence of fluoroquinolone-resistant microorganisms. A prospective observational study of patients diagnosed with community-acquired UTI was conducted, in which their outcomes according to whether they had FQs or not in their empirical and directed treatments were compared. A multivariate analysis was performed to identify risk factors for UTIs due to ciprofloxacin-resistant microorganisms. A total of 419 patients were included; 162 (38.7%) patients were treated with FQs, as empirical treatment in 27 (6.4%), and as directed treatment in 135 (32.2%). In-hospital mortality (2.2% vs. 6.6%, p 0.044) and 30-day mortality (4.4 vs. 11%, p 0.028) were both lower in the group of patients directly treated with FQ, while there were no differences when FQs were used as empirical treatment. A total of 37.2% of the cases were resistant to ciprofloxacin, which was associated with healthcare-associated UTI (OR 2.7, 95% CI 2-3.7) and prior exposure to FQs (OR 2.7, 95 % CI 1.9-3.7). In conclusion, our findings show that in a setting with a high prevalence of community-acquired UTI caused by quinolone-resistant microorganisms, FQs as directed treatment for community-acquired UTI were associated with better outcomes than other antibiotics, but their use as empirical treatment is not indicated, even in those cases without risk factors for quinolones resistance.

The Role of Methyl-(Z)-11-tetradecenoate Acid from the Bacterial Membrane Lipid Composition in Escherichia coli Antibiotic Resistance

Background

The bacterial membrane plays a critical role in the survival of bacteria and the effectiveness of antimicrobial peptides in protecting the host. The lipid constituents of the bacterial membrane are not evenly distributed, and they could be affected by clustering anionic lipids with cationic peptides with multiple positive charges. That could be harmful to bacteria because it prevents lipids from interacting with other molecular components of the cell membrane, disrupts existing natural domains, or creates phase boundary defects between the clustered lipids and the bulk of the membrane. This preliminary quantitative study is aimed at assembling a correlation between antibiotic resistance and bacterial lipid composition in E. coli, based on the function and arrangement of the bilipid coating of the bacterial cell, intimately associated with the path of antimicrobials through membranes.

Methods

Fifteen multiresistant E. coli samples are collected from swine with enterocolitis tested for resistance levels using the disc diffusimetric method (Kirby-Bauer disc diffusion). Pathogen identification completed using the API 20E multitest system revealed the E. coli presence in 11 samples. In these samples, bacterial membrane detection of fatty acid methyl esters (FAME) operating a 240 MS Ion Trap (Varian) GC/MS (Agilent Technologies, Santa Clara, CA, USA) was performed, using the MIDI Sherlock recognition software model.

Results

Interpreting the descriptive statistical method, the correlation matrix, and regression curves and after ANOVA analysis, we ascertained that the studied E. coli population statistically confirmed different degrees of resistance in most of the samples analyzed in this test.

Conclusions

In one case, the methyl-(Z)-11-tetradecenoate acid was observed to have a relationship with the susceptibility evaluation by using the disc diffusimetric method, which has revealed the lowest rate of antimicrobial resistance, so it has importance in further resistance evaluation studies.

Fluoroquinolones-Associated Disability: It Is Not All in Your Head

Fluoroquinolones (FQs) are a broad class of antibiotics typically prescribed for bacterial infections, including infections for which their use is discouraged. The FDA has proposed the existence of a permanent disability (Fluoroquinolone Associated Disability; FQAD), which is yet to be formally recognized. Previous studies suggest that FQs act as selective GABAA receptor inhibitors, preventing the binding of GABA in the central nervous system. GABA is a key regulator of the vagus nerve, involved in the control of gastrointestinal (GI) function. Indeed, GABA is released from the Nucleus of the Tractus Solitarius (NTS) to the Dorsal Motor Nucleus of the vagus (DMV) to tonically regulate vagal activity. The purpose of this review is to summarize the current knowledge on FQs in the context of the vagus nerve and examine how these drugs could lead to dysregulated signaling to the GI tract. Since there is sufficient evidence to suggest that GABA transmission is hindered by FQs, it is reasonable to postulate that the vagal circuit could be compromised at the NTS-DMV synapse after FQ use, possibly leading to the development of permanent GI disorders in FQAD.

Resistance-Guided Treatment of Gonorrhea: A Prospective Clinical Study

BACKGROUND

Novel treatment strategies to slow the continued emergence and spread of antimicrobial resistance in Neisseria gonorrhoeae are urgently needed. A molecular assay that predicts in vitro ciprofloxacin susceptibility is now available but has not been systematically studied in human infections.

METHODS

Using a genotypic polymerase chain reaction assay to determine the status of the N. gonorrhoeae gyrase subunit A serine 91 codon, we conducted a multisite prospective clinical study of the efficacy of a single oral dose of ciprofloxacin 500 mg in patients with culture-positive gonorrhea. Follow-up specimens for culture were collected to determine microbiological cure 5-10 days post-treatment.

RESULTS

Of the 106 subjects possessing culture-positive infections with wild-type gyrA serine N. gonorrhoeae genotype, the efficacy of single-dose oral ciprofloxacin treatment in the per-protocol population was 100% (95% 1-sided confidence interval, 97.5-100%).

CONCLUSIONS

Resistance-guided treatment of N. gonorrhoeae infections with single-dose oral ciprofloxacin was highly efficacious. The widespread introduction and scale-up of gyrA serine 91 genotyping in N. gonorrhoeae infections could have substantial medical and public health benefits in settings where the majority of gonococcal infections are ciprofloxacin susceptible.

CLINICAL TRIALS REGISTRATION

NCT02961751.

Oral fluoroquinolones and risk of aortic or mitral regurgitation: a nationwide nested case-control study

AIMS

Reports have suggested an increased risk of aortic and mitral regurgitation associated with oral fluoroquinolones (FQs) resulting in a safety warning published by the European Medicines Agency (EMA). However, these findings have not yet been replicated.

METHODS AND RESULTS

Using Danish administrative registers, we conducted a nested case-control study in a nationwide cohort of individuals between 2005 and 2018. Cases were defined as the first occurrence of aortic or mitral regurgitation. Exposure of interest was the use of oral FQs. Hazard ratios (HRs) with 95% confidence intervals (95% CI) were obtained by fitting time-dependent Cox regression models, with penicillin V as comparator, to assess the association between FQ use and incident valvular regurgitation. We identified 38 370 cases of valvular regurgitation with 1 115 100 matched controls. FQ exposure was not significantly associated with increased rates of aortic or mitral regurgitation (HR 1.02, 95% CI 0.95-1.09) compared with penicillin V users. Investigating the cumulative defined daily doses (cDDD) of FQs yielded similar results with no significant association between increasing FQ use and valvular regurgitation (e.g. HR 1.08, 95% CI 0.95-1.23 for cDDD >10 compared with cDDD 1-5). These results were consistent across several analyses including a cohort of patients with hypertension and using a case definition based on valvular surgical interventions.

CONCLUSIONS

In a nationwide nested case-control study, FQs were not significantly associated with increased rates of valvular regurgitation. Our findings do not support a possible causal connection between FQ exposure and incident valvular regurgitation.

Interaction of Quinolones Carrying New R1 Group with Mycobacterium leprae DNA Gyrase

Background: Leprosy is a chronic infectious disease caused by Mycobacterium leprae and the treatment of choice is ofloxacin (OFX). Specific amino acid substitutions in DNA gyrase of M. leprae have been reported leading to resistance against the drug. In our previous study, WQ-3810, a fluoroquinolone with a new R1 group (6-amino-3,5-difluoropyridin-2-yl) was shown to have a strong inhibitory activity on OFX-resistant DNA gyrases of M. leprae, and the structural characteristics of its R1 group was predicted to enhance the inhibitory activity. Methodology/Principal Finding: To further understand the contribution of the R1 group, WQ-3334 with the same R1 group as WQ-3810, WQ-4064, and WQ-4065, but with slightly modified R1 group, were assessed on their activities against recombinant DNA gyrase of M. leprae. An in silico study was conducted to understand the molecular interactions between DNA gyrase and WQ compounds. WQ-3334 and WQ-3810 were shown to have greater inhibitory activity against M. leprae DNA gyrase than others. Furthermore, analysis using quinolone-resistant M. leprae DNA gyrases showed that WQ-3334 had greater inhibitory activity than WQ-3810. The R8 group was shown to be a factor for the linkage of the R1 groups with GyrB by an in silico study. Conclusions/Significance: The inhibitory effect of WQ compounds that have a new R1 group against M. leprae DNA gyrase can be enhanced by improving the binding affinity with different R8 group molecules. The information obtained by this work could be applied to design new fluoroquinolones effective for quinolone-resistant M. leprae and other bacterial pathogens.

Treatment Strategies Against Diabetic Foot Ulcer: Success so Far and the Road Ahead

BACKGROUND

Diabetic foot ulcer (DFU) is one of the leading complications of type-2 diabetes mellitus. It is associated with neuropathy and peripheral arterial disease of the lower limb in patients with diabetes. There are four stages of wound healing, namely hemostasis phase, inflammatory phase, proliferative phase and maturation phase. In the case of DFU, all these stages are disturbed which lead to delay in healing and consequently to lower limb amputation. Conventional dosage forms like tablets, creams, ointments, gels and capsules have been used for the treatment of diabetic foot ulcer for many years.

INTRODUCTION

In this review, the global prevalence as well as etiopathogenesis related to diabetic foot ulcer have been discussed. The potential role of various synthetic and herbal drugs, as well as their conventional dosage forms in the effective management of DFU have been discussed in detail.

METHODS

Structured search of bibliographic databases from previously published peer-reviewed research papers was explored and data has been represented in terms of various approaches that are used for the treatment of DFU.

RESULTS

About 148 papers, including both research and review articles, were included in this review to produce a comprehensive as well as a readily understandable article. A series of herbal and synthetic drugs have been discussed along with their current status of treatment in terms of dose and mechanism of action.

CONCLUSION

DFU has become one of the most common complications in patients having diabetes for more than ten years. Hence, understanding the root cause and its successful treatment is a big challenge because it depends upon multiple factors such as the judicious selection of drugs as well as proper control of blood sugar level. Most of the drugs that have been used so far either belong to the category of antibiotics, antihyperglycaemic or they have been repositioned. In clinical practice, much focus has been given to dressings that have been used to cover the ulcer. The complete treatment of DFU is still a farfetched dream to be achieved and it is expected that combination therapy of herbal and synthetic drugs with multiple treatment pathways could be able to offer better management of DFU.

Binocular Diplopia: A Possible Adverse Effect of Fluoroquinolone Therapy

The adverse effects of fluoroquinolones are yet to be fully elucidated. We present an interesting case of a 41-year-old male with binocular diplopia most likely induced by the use of a fluoroquinolone antibiotic.

Use of a magnetic covalent organic framework material with a large specific surface area as an effective adsorbent for the extraction and determination of six fluoroquinolone antibiotics by HPLC in milk sample

A magnetic covalent organic framework material was synthesized with a core-shell structure using a simple solvothermal method. It was prepared with Fe₃ O₄ as the magnetic core, covalent organic framework as the shell, which synthesized from 1,3,5-triformylphloroglucinol and p-phenylenediamine by Schiff base reaction. Transmission electron microscopy, Fourier transform infrared spectroscopy, powder X-ray diffraction, vibrating sample magnetometry, and nitrogen adsorption-desorption were used to characterize magnetic adsorbent. It has showed a large specific surface area (505.6 m² /g), which can provide many adsorption sites. Moreover, the saturation magnetization value was 48.4 emu/g enough to be separated by external magnet. Six kinds of fluoroquinolones (enoxacin, fleroxacin, ofloxacin, norfloxacin, pefloxacin, and lomefloxacin) were extracted by magnetic solid phase extraction with the magnetic adsorbent. High-performance liquid chromatography detects the entire adsorption and desorption process to further evaluate the optimal extraction and desorption conditions. Under the optimal chromatographic conditions, this method showed a low detection limit (0.05 to 0.20 μg/L), good linearity in the range of 0.5 to 200 μg/L, and the enrichment factor reaches 115.5-127.3. The spiked recovery of the fluoroquinolones in milk sample ranged from 90.4 to 101.2%.

The safety of antimicrobials for the treatment of community-acquired pneumonia

Introduction: Community-acquired pneumonia (CAP) is a leading cause of morbidity and mortality worldwide, and its prevalence continues to increase. Despite the efficacy of antimicrobials, their safety and tolerability remain topics of interest and concern for clinicians and patients alike.Areas covered: This review outlines the main antimicrobial classes recommended for the empirical treatment of CAP in current guidelines, together with a potential new class. Each pharmacological group underwent a safety evaluation based on all available data about drug-related toxicities. The authors also present their mechanisms of action, their pharmacokinetic and pharmacodynamic properties, and the main clinical studies.Expert opinion: Overall, antimicrobials currently marketed for the treatment of CAP are well tolerated and generally safe. However, unusual and sometimes serious adverse effects can occur in susceptible populations. Attention should be paid to identifying patients at risk of developing drug-related toxicities because, although most effects are transient, some could be disabling, permanent, or even fatal. Post-marketing surveillance remains crucial for gathering data to overcome the limitations of preclinical and clinical studies in estimating the true prevalence of drug-related adverse events.

Antimicrobial resistance, mechanisms and its clinical significance

Antimicrobial agents play a key role in controlling and curing infectious disease. Soon after the discovery of the first antibiotic, the challenge of antibiotic resistance commenced. Antimicrobial agents use different mechanisms against bacteria to prevent their pathogenesis and they can be classified as bactericidal or bacteriostatic. Antibiotics are one of the antimicrobial agents which has several classes, each with different targets. Consequently, bacteria are endlessly using methods to overcome the effectivity of the antibiotics by using distinct types of mechanisms. Comprehending the mechanisms of resistance is vital for better understanding and to continue use of current antibiotics. Which also helps to formulate synthetic antimicrobials to overcome the current mechanism of resistance. Also, encourage in prudent use and misuse of antimicrobial agents. Thus, decline in treatment costs and in the rate of morbidity and mortality. This review will be concentrating on the mechanism of actions of several antibiotics and how bacteria develop resistance to them, as well as the method of acquiring the resistance in several bacteria and how can a strain be resistant to several types of antibiotics. This review also analyzes the prevalence, major clinical implications, clinical causes of antibiotic resistance. Further, it evaluates the global burden of antimicrobial resistance, identifies various challenges and strategies in addressing the issue. Finally, put forward certain recommendations to prevent the spread and reduce the rate of resistance growth.

Antimicrobial Susceptibility of Campylobacter isolates in the Capital of North Macedonia

BACKGROUND

Campylobacter infections are typically self-limited, but in cases with severe enteritis, immuno-compromised system and bacteremia, an appropriate antimicrobial treatment is demanding. Our study aim was to determine the isolation rate of Campylobacter among patients with acute enteritis in the capital of North Macedonia and its antimicrobial susceptibility.

MATERIAL AND METHODS

A total number of 3820 patients clinically diagnosed as acute enteritis, were included in the study. Stool samples were collected and Campylobacter was isolated and identified by classical microbiological methods. Antimicrobial susceptibility of all isolates to Ceftriaxone, Amoxicillin-clavulonic acid, Erythromycin, Ciprofloxacin, Tetracycline and Gentamicin was determined by disc-diffusion technique. Additionally, minimal inhibitory concentrations of all Campylobacter isolates against erythromycin, ciprofloxacin and tetracycline were determined by Epsilon gradient tests.

RESULTS

Campylobacter species was isolated in 97 patients. Although the mean isolation rate of Campylobacter spp. during the whole study period was 2.53%, a statistically significant increase was detected in 2016 and 2017, in comparison with the data from previous four years of the study. The isolation rate of Campylobacter spp. didn't reveal statistically significant difference between males and females (p > 0.05). 46.4 % of patients with Campylobacter enteritis were children at the age under 15 years. Forty-three C. jejuni isolates were susceptible to all six antibiotics, but the remaining 44 isolates revealed resistance to at least one antibiotic. C. coli isolates were resistant to 3 antibiotics simultaneously. Two C. coli isolates only, were susceptible to all 6 antibiotics. 40.90% of C. jejuni and 50% of C. coli isolates were resistant to beta-lactams, fluoroquinolones and tetracyclines, simultaneously.

CONCLUSION

The increase of the isolation rate of Campylobacter from patients with acute enteritis indicates the need for permanent isolation and identification of Campylobacter from every clinically diagnosed patient, as acute enteritis. Erythromicin is the most effective antibiotic for treatment of Campylobacter enteritis in our patients. The high level of Campylobacter resistance to beta-lactams, fluoroquinolones and tetracyclines requires more rational approach in the treatment of Campylobacter enteritis.

WQ-3810 inhibits DNA gyrase activity in ofloxacin-resistant Mycobacterium leprae

BACKGROUND

Mycobacterium leprae causes leprosy and ofloxacin is used to control this bacterium. However, specific amino acid substitutions in DNA gyrases of M. leprae interferes with the effect of ofloxacin.

METHODOLOGY/PRINCIPAL FINDINGS

Here we tested the inhibitory effect of WQ-3810 on DNA gyrases in M. leprae, using recombinant gyrases. We theorized that WQ-3810 and DNA gyrases interacted, which was tested in silico. Compared with control drugs like ofloxacin, WQ-3810 showed a better inhibitory effect on ofloxacin-resistant DNA gyrases. The in-silico study showed that, unlike control drugs, a specific linkage between a R1 group in WQ-3810 and aspartic acid at position 464 in the subunit B of DNA gyrases existed, which would enhance the inhibitory effect of WQ-3810. This linkage was confirmed in a further experiment, using recombinant DNA gyrases with amino acid substitutions in subunits B instead.

CONCLUSIONS/SIGNIFICANCE

The inhibitory effect of WQ-3810 was likely enhanced by the specific linkage between a R1 group residue in its structure and DNA gyrases. Using interactions like the one found in the present work may help design new fluoroquinolones that contribute to halt the emergence of antibiotic-resistant pathogens.

Antimicrobial Activity of Quinoline-Based Hydroxyimidazolium Hybrids

Eight quinoline-based hydroxyimidazolium hybrids 7a-h were prepared and evaluated in vitro against a panel of clinically important fungal and bacterial pathogens, including mycobacteria. Hybrid compounds 7c-d showed remarkable antifungal activity against Cryptococcus neoformans with a minimum inhibitory concentration (MIC) value of 15.6 µg/mL. Against other opportunistic fungi such as Candida spp. and Aspergillus spp., these hybrids showed MIC values of 62.5 µg/mL. Regarding their antibacterial activity, all the synthetic hybrids demonstrated little inhibition of Gram-negative bacteria (MIC ≥50 µg/mL), however, hybrid 7b displayed >50% inhibition against Klebsiella pneumoniae at 20 µg/mL and full inhibition at 50 µg/mL. Moreover, this hybrid was shown to be a potent anti-staphylococcal molecule, with a MIC value of 2 µg/mL (5 µM). In addition, hybrid 7h also demonstrated inhibition of Staphylococcus aureus at 20 µg/mL (47 µM). Hybrids 7a and 7b were the most potent against Mycobacterium tuberculosis H37Rv with MIC values of 20 and 10 µg/mL (46 and 24 µM), respectively. The 7b hybrid demonstrated high selectivity in killing S. aureus and M. tuberculosis H37Rv in comparison with mammalian cells (SI >20), and thus it can be considered a hit molecule for mechanism of action studies and the exploration of related chemical space.

Clinical Benefit of Empiric High-Dose Levofloxacin Therapy for Adults With Community-onset Enterobacteriaceae Bacteremia

PURPOSE

Levofloxacin is commonly prescribed to treat varied community-acquired gram-negative infections; knowledge of the therapeutic efficacies of high-dose (HD) administration is helpful to improve patient care.

METHODS

In this 6-year cohort, adults with community-onset Enterobacteriaceae bacteremia were retrospectively studied in 2 hospitals. To overcome the confounding factors in the dosage choice of empiric administration, patients receiving empiric intravenous HD (750 mg/d) therapy were matched with those receiving the conventional dose (CD; 500 mg/d) by using individual propensity scores, calculated by the independent predictors of 30-day crude mortality.

FINDINGS

Initially, more patients with critical illness (Pitt bacteremia score [PBS] ≥4) at bacteremia onset and comorbid malignancies and the higher 15- and 30-day mortality rate were recorded in 136 patients receiving HD therapy, compared to 103 receiving CD therapy. After appropriate matching, differences in patient demographic and clinical characteristics between the HD (n = 103) and CD (n = 103) groups were nonsignificant. Consequently, crude mortality rates at 3, 15, or 30 days after onset of bacteremia did not differ. However, the period of time to defervescence, total intravenous antimicrobial administration, and hospital stay was shorter in the HD group than in the CD group. Similarly, regardless if patients had more critical illness (PBS ≥2) or stabilized illness (PBS <2), the advantage of empiric HD therapy on defervescence remained significant. Within 60 days after discontinuation of intravenous levofloxacin therapy, the proportion of recurrent bacteremia, posttreatment overall infections, and posttreatment crude mortality was similar between the HD and CD groups.

IMPLICATIONS

For adults with community-onset Enterobacteriaceae bacteremia, empiric administration of HD levofloxacin was as effective as CD levofloxacin in reducing mortality and, notably, led to more rapid defervescence compared with CD administration.

Beneficial Effect of Early Intervention with Garenoxacin for Bacterial Infection-Induced Acute Exacerbation of Bronchial Asthma and Chronic Obstructive Pulmonary Disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) and asthma have similar clinical features and are both exacerbated by airway infection.

OBJECTIVE

To determine whether garenoxacin mesylate hydrate (GRNX) added to the standard care for bacterial infection-induced acute exacerbation of asthma or COPD in adults has clinical benefits.

METHOD

This single-arm clinical trial was conducted from January 2015 to March 2016. Adults with a history of asthma or COPD for more than 12 months were recruited within 48 h of presentation with fever and acute deterioration of asthma or COPD requiring additional intervention. Participants were administered 400 mg GRNX daily for 7 days without additional systemic corticosteroids or other antibiotics. The primary outcome was efficacy of GRNX based on clinical symptoms and blood test results after 7 days of treatment. Secondary outcomes were: (1) comparison of the blood test results, radiograph findings, and bacterial culture surveillance before and after treatment; (2) effectiveness of GRNX after 3 days of administration; (3) analyzation of patient symptoms based on patient diary; and (4) continued effectiveness of GRNX on 14th day after the treatment (visit 3).

RESULTS

The study included 44 febrile patients (34 asthma and 10 COPD). Frequently isolated bacteria included Moraxella catarrhalis (n = 6) and Klebsiella pneumoniae (n = 4). On visit 2, 40 patients responded, and no severe adverse events were observed. All secondary outcomes showed favorable results.

CONCLUSION

GRNX effectively treated asthma and COPD patients with acute bacterial infection without severe adverse events. Further research with a larger study population is needed.

Fluoroquinolones and the Risk of Achilles Tendon Disorders: Update on a Neglected Complication

OBJECTIVE

To evaluate the current evidence and to identify associated risk factors that increase the incidence of this complication. Fluoroquinolone (FQ) has been considered the first-line therapy for uncomplicated urinary infections. FQ has been associated with Achilles tendon disorders, especially during the first month of treatment.

METHODS

Data sources searched included PubMed, MEDLINE, and Scopus from January 1988 to June 2017.

RESULTS

A total of 79 articles were used, with ciprofloxacin representing the most common drug.

CONCLUSION

We found that male gender, advanced age, normal body mass index, chronic renal failure, and concurrent use of corticosteroids increase the risk of Achilles tendon disorders.

Early postoperative fluoroquinolone use is associated with an increased revision rate after arthroscopic rotator cuff repair

PURPOSE

To evaluate the association of postoperative fluoroquinolone use following arthroscopic primary rotator cuff repair with failure requiring revision rotator cuff repair.

METHODS

An insurance database was queried for patients undergoing rotator cuff repair from 2007 to 2015. These patients were divided into three groups: (1) patients prescribed fluoroquinolones within 6 months postoperatively (divided into 0-2, 2-4, and 4-6 months), (2) a matched negative control cohort of patients not prescribed fluoroquinolones, and (3) a matched positive control cohort of patients prescribed fluoroquinolones between 6 and 18 months following rotator cuff repair. Rates of failure requiring revision rotator cuff repair were compared within 2 years.

RESULTS

A total of 1292 patients were prescribed fluoroquinolones within 6 months after rotator cuff repair, including 442 within 2 months, 433 within 2 to 4 months, and 417 within 4 to 6 months, and were compared to 5225 matched negative controls and 1597 matched positive controls. The rate of revision rotator cuff repair was significantly higher in patients prescribed fluoroquinolones within 2 months (6.1 %) compared to matched negative (2.2 %, P = 0.0009) and positive controls (2.4 %, P = 0.0026). There were no significant differences in the rate of revision rotator cuff repair when fluoroquinolones were prescribed >2 months after rotator cuff repair.

CONCLUSIONS

Early use of fluoroquinolones following rotator cuff repair was independently associated with significantly increased rates of failure requiring revision rotator cuff repair. This is the first clinical study examining the association of postoperative fluoroquinolone use with failure following arthroscopic rotator cuff repair.

LEVEL OF EVIDENCE

III.

Molecular and Pharmacologic Properties of the Anticancer Quinolone Derivative Vosaroxin: A New Therapeutic Agent for Acute Myeloid Leukemia

Vosaroxin is a first-in-class anticancer quinolone derivative that targets topoisomerase II and induces site-selective double-strand breaks in DNA, leading to tumor cell apoptosis. Vosaroxin has chemical and pharmacologic characteristics distinct from other topoisomerase II inhibitors due to its quinolone scaffold. The efficacy and safety of vosaroxin in combination with cytarabine were evaluated in patients with relapsed/refractory acute myeloid leukemia (AML) in a phase III, randomized, multicenter, double-blind, placebo-controlled study (VALOR). In this study, the addition of vosaroxin produced a 1.4-month improvement in median overall survival (OS; 7.5 months with vosaroxin/cytarabine vs. 6.1 months with placebo/cytarabine; hazard ratio [HR] 0.87, 95 % confidence interval [CI] 0.73−1.02; unstratified log-rank p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}= 0.061; stratified log-rank p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}=0.024), with the greatest OS benefit observed in patients ≥60 years of age (7.1 vs. 5.0 months; HR 0.75, 95 % CI 0.62−0.92; p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}=0.003) and patients with early relapse (6.7 vs. 5.2 months; HR 0.77, 95 % CI 0.59−1.00; p\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document}= 0.039), two AML patient groups that typically have poor prognosis. Here we review the chemical and pharmacologic properties of vosaroxin, how these properties are distinct from those of currently available topoisomerase II inhibitors, how they may contribute to the efficacy and safety profile observed in the VALOR trial, and the status of clinical development of vosaroxin for treatment of AML.

Clinical Benefit of Appropriate Empirical Fluoroquinolone Therapy for Adults with Community-Onset Bacteremia in Comparison with Third-Generation-Cephalosporin Therapy

Both fluoroquinolones (FQs) and third-generation cephalosporins (3rd-GCs) are commonly prescribed to treat bloodstream infections, but comparative efficacies between them were rarely studied. Demographics and clinical characteristics of 733 adults with polymicrobial or monomicrobial community-onset bacteremia empirically treated by an appropriate FQ (n = 87) or 3rd-GC (n = 646) were compared. A critical illness (respectively, 8.0% versus 19.0%; P = 0.01), an initial syndrome with severe sepsis (33.3% versus 50.3%; P = 0.003), or a fatal outcome at 28 days (4.6% versus 10.5%; P = 0.08) was less common in the FQ group. A total of 645 (88.0%) patients were febrile at initial presentation, and the FQ group with (FQ group versus 3rd-GC group, respectively, 7.6 days versus 12.0 days; P = 0.04) and without (3.8 days versus 5.4 days; P = 0.001) a critical illness had a shorter time to defervescence than the 3rd-GC group. By the propensity scores, 87 patients with appropriate FQ therapy were matched with 435 treated by 3rd-GC therapy at a ratio of 1:5, and there were no significant differences in terms of bacteremia severity, comorbidity severity, major comorbidities, causative microorganisms, and bacteremia sources between groups. Moreover, crude mortality rates at 28 days (FQ group versus 3rd-GC group, respectively, 4.6% versus 7.8%; P = 0.29) did not differ significantly. However, the time to defervescence was shorter in the FQ group (4.2 ± 3.6 versus 6.2 ± 7.6 days; P < 0.001). Conclusively in the adults with community-onset bacteremia, appropriate empirical FQ therapy was related to shorter time to defervescence than with 3rd-GC therapy, at least for those without a critical illness.

DC-159a Shows Inhibitory Activity against DNA Gyrases of Mycobacterium leprae

BACKGROUND

Fluoroquinolones are a class of antibacterial agents used for leprosy treatment. Some new fluoroquinolones have been attracting interest due to their remarkable potency that is reportedly better than that of ofloxacin, the fluoroquinolone currently recommended for treatment of leprosy. For example, DC-159a, a recently developed 8-methoxy fluoroquinolone, has been found to be highly potent against various bacterial species. Nonetheless, the efficacy of DC-159a against Mycobacterium leprae is yet to be examined.

METHODOLOGY/PRINCIPAL FINDINGS

To gather data that can support highly effective fluoroquinolones as candidates for new remedies for leprosy treatment, we conducted in vitro assays to assess and compare the inhibitory activities of DC-159a and two fluoroquinolones that are already known to be more effective against M. leprae than ofloxacin. The fluoroquinolone-inhibited DNA supercoiling assay using recombinant DNA gyrases of wild type and ofloxacin-resistant M. leprae revealed that inhibitory activities of DC-159a and sitafloxacin were at most 9.8- and 11.9-fold higher than moxifloxacin. Also the fluoroquinolone-mediated cleavage assay showed that potencies of those drugs were at most 13.5- and 9.8-fold higher than moxifloxacin. In addition, these two drugs retained their inhibitory activities even against DNA gyrases of ofloxacin-resistant M. leprae.

CONCLUSIONS/SIGNIFICANCE

The results indicated that DC-159a and sitafloxacin are more effective against wild type and mutant M. leprae DNA gyrases than moxifloxacin, suggesting that these antibacterial drugs can be good candidates that may supersede current fluoroquinolone remedies. DC-159a in particular is very promising because it is classified in a subgroup of fluoroquinolones that is known to be less likely to cause adverse effects. Our results implied that DC-159a is well worth further investigation to ascertain its in vivo effectiveness and clinical safety for humans.

High Throughput Screen for Inhibitors of Bacterial DNA Topoisomerase I Using the Scintillation Proximity Assay

We report the development of a rapid method to detect binding of supercoiled DNA to Escherichia coli topoisomerase I using the scintillation proximity assay (SPA). Streptavidin-SPA beads were coated with biotinylated topoisomerase I produced in vivo as a chimeric fusion protein. The hybrid biotinyl-fusion protein was overproduced in E. coli and purified in a single step by monomeric avidin affinity chromatography. The assay signal originates from both covalent and noncovalent binding of [3H]DNA to the SPA bead-immobilized enzyme. About 20-30% of the total [3H]DNA bound to the bead-immobilized enzyme remains associated with the bead in the presence of 0.5% SDS. The residual signal arises from the trapping of covalent [3H]DNA-enzyme complexes. The assay was employed in a high throughput screen that identified two general classes of topoisomerase inhibitors: agents that (1) inhibit DNA binding or (2) stabilize a covalent enzyme-DNA intermediate.

A systematic review and meta-analysis of the association between systemic fluoroquinolones and retinal detachment

PURPOSE

Several pharmacoepidemiologic studies have been carried out evaluating the risk of retinal detachment associated with systemic fluoroquinolones. This meta-analysis aims to investigate such association, in the light of the best scientific evidence available.

METHODS

A literature search was conducted to identify relevant studies evaluating the risk for retinal detachment associated with systemic fluoroquinolones. A meta-analysis was performed to pool rate ratios (RRs). Meta-regressions were conducted aiming to evaluate the influence of time interval between fluoroquinolones use and retinal detachment diagnosis or treatment risk estimates.

RESULTS

Ten observational studies from seven publications were included. Overall, fluoroquinolones were not associated with an increased risk for retinal detachment [RR 1.47 (95% CI 0.95-2.27): p = 0.09; I(2)  = 92.8%]. When the analysis was stratified according to different study designs, the result was statistically significant for retrospective cohort studies [RR 1.87 (95% CI 1.36-2.58); p < 0.001; I(2)  = 0.0%] and for past users of fluoroquinolones, based on data from case-control studies [RR 1.07 (95% CI 1.01-1.12); p = 0.01; I(2)  = 0.0%]. According to meta-regressions, the risk for retinal detachment did not vary due to different time intervals between fluoroquinolones prescription and retinal detachment occurrence. No statistically significant results were identified among studies evaluating only rhegmatogenous retinal detachments, as well as among studies that evaluated patients not requiring a prior ophthalmologist visit to be included.

CONCLUSIONS

In light of the current available evidence, systemic fluoroquinolones do not seem to be associated with retinal detachment.

(68) Ga-labeled Ciprofloxacin Conjugates as Radiotracers for Targeting Bacterial Infection

With an aim of developing a bacteria-specific molecular imaging agent, ciprofloxacin has been modified with a propylamine spacer and linked to two common bifunctional chelators, p-SCN-Bz-DOTA and p-SCN-Bz-NOTA. The two ciprofloxacin conjugates, CP-PA-SCN-Bz-DOTA (1) and CP-PA-SCN-Bz-NOTA (2), were radiolabeled with (68)Ga in >90% radiochemical yield and were moderately stable in vitro for 4 h. The efficacy of (68)Ga-1 and (68)Ga-2 has been investigated in vitro in Staphylococcus aureus cells where bacterial binding of the radiotracers (0.9-1.0% for (68)Ga-1 and 1.6-2.3% for (68)Ga-2) could not be blocked in the presence of excess amount of unlabeled ciprofloxacin. However, uptake of radiotracers in live bacterial cells was significantly higher (p < 0.01) than that in non-viable bacterial cells. Bacterial infection targeting efficacy of (68)Ga-1 and (68)Ga-2 was tested in vivo in rats where the infected muscle-to-inflamed muscle ((68)Ga-1: 2 ± 0.2, (68)Ga-2: 3 ± 0.5) and infected muscle-to-normal muscle ratios ((68)Ga-1: 3 ± 0.4, (68)Ga-2: 6.6 ± 0.8) were found to improve at 120 min p.i. Fast blood clearance and renal excretion was observed for both the radiotracers. The two (68)Ga-labeled infection targeting radiotracers could discriminate between bacterial infection and inflammation in vivo and are worthy of further detailed investigation as infection imaging agents at the clinical level.

Ciprofloxacin-Photoswitch Conjugates: A Facile Strategy for Photopharmacology

Photopharmacology aims to locally treat diseases and study biological processes with photoresponsive drugs. Herein, easy access to photoswitchable drugs is crucial, which is supported by simple and robust drug modifications. We investigated the possibility of creating drugs that can undergo remote activation and deactivation with light, by conjugating molecular photoswitches to the exterior of an existing drug in a single chemical step. This facile strategy allows the convenient introduction of various photochromic systems into a drug molecule, rendering it photoresponsive. To demonstrate the feasibility of this approach, two photoswitch-modified ciprofloxacin antibiotics were synthesized. Remarkably, for one of them a 50-fold increase in activity compared to the original ciprofloxacin was observed. Their antimicrobial activity could be spatiotemporally controlled with light, which was exemplified by bacterial patterning studies.

Antimicrobial Resistance and Molecular Investigation of H2S-Negative Salmonella enterica subsp. enterica serovar Choleraesuis Isolates in China

Salmonella enterica subsp. enterica serovar Choleraesuis is a highly invasive pathogen of swine that frequently causes serious outbreaks, in particular in Asia, and can also cause severe invasive disease in humans. In this study, 21 S. Choleraesuis isolates, detected from 21 patients with diarrhea in China between 2010 and 2011, were found to include 19 H₂S-negative S. Choleraesuis isolates and two H₂S-positive isolates. This is the first report of H₂S-negative S. Choleraesuis isolated from humans. The majority of H₂S-negative isolates exhibited high resistance to ampicillin, chloramphenicol, gentamicin, tetracycline, ticarcillin, and trimethoprim-sulfamethoxazole, but only six isolates were resistant to norfloxacin. In contrast, all of the isolates were sensitive to cephalosporins. Fifteen isolates were found to be multidrug resistant. In norfloxacin-resistant isolates, we detected mutations in the gyrA and parC genes and identified two new mutations in the parC gene. Pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and clustered regularly interspaced short palindromic repeat (CRISPR) analysis were employed to investigate the genetic relatedness of H₂S-negative and H₂S-positive S. Choleraesuis isolates. PFGE revealed two groups, with all 19 H₂S-negative S. Choleraesuis isolates belonging to Group I and H₂S-positive isolates belonging to Group II. By MLST analysis, the H₂S-negative isolates were all found to belong to ST68 and H₂S-positive isolates belong to ST145. By CRISPR analysis, no significant differences in CRISPR 1 were detected; however, one H₂S-negative isolate was found to contain three new spacers in CRISPR 2. All 19 H₂S-negative isolates also possessed a frame-shift mutation at position 760 of phsA gene compared with H₂S-positive isolates, which may be responsible for the H₂S-negative phenotype. Moreover, the 19 H₂S-negative isolates have similar PFGE patterns and same mutation site in the phsA gene, these results indicated that these H₂S-negative isolates may have been prevalent in China. These findings suggested that surveillance should be increased of H₂S-negative S. Choleraesuis in China.

Identification of chebulinic acid as potent natural inhibitor of M. tuberculosis DNA gyrase and molecular insights into its binding mode of action

Drug resistant tuberculosis has threatened all the advances that have been made in TB control at the global stage in the last few decades. DNA gyrase enzymes are an excellent target for antibacterial drug discovery as they are involved in essential functions like DNA replication. Here we report, a successful application of high throughput virtual screening (HTVS) to identify an inhibitor of Mycobacterium DNA gyrase targeting the wild type and the most prevalent three double mutants of quinolone resistant DNA gyrase namely A90V+D94G, A74S+D94G and A90V+S91P. HTVS of 179.299 compounds gave five compounds with significant binding affinity. Extra presicion (XP) docking and MD simulations gave a clear view of their interaction pattern. Among them, chebulinic acid (CA), a phytocompound obtained from Terminalia chebula was the most potent inhibitor with significantly high XP docking score, -14.63, -16.46, -15.94 and -15.11 against wild type and three variants respectively. Simulation studies for a period of 16 ns indicated stable DNA gyrA-CA complex formation. This stable binding would result in inhibition of the enzyme by two mechanisms. Firstly, binding of CA causes displacement of catalytic Tyr129 away from its target DNA-phosphate molecule from 1.6 Å to 3.8-7.3 Å and secondly, by causing steric hindrance to the binding of DNA strand at DNA binding site of enzyme. The combined effect would result in loss of cleavage and religation activity of enzyme leading to bactericidal effect on tuberculosis. This phytocompound displays desirable quality for carrying forward as a lead compound for anti-tuberculosis drug development. The results presented here are solely based on computations and need to be validated experimentally in order to assert the proposed mechanism of action.

Origin and Dissemination of Antimicrobial Resistance among Uropathogenic Escherichia coli

Antimicrobial agents of various types have important bearing on the outcomes of microbial infections. These agents may be bacteriostatic or –cidal, exert their impact via various means, originate from a living organism or a laboratory, and appropriately be used in or on living tissue or not. Though the primary focus of this chapter is on resistance to the antimicrobial agents used to treat uropathogenic Escherichia coli (UPEC)-caused urinary tract infections (UTIs), some attention will be given to UPEC’s resistance to silver-containing antiseptics, which may be incorporated into catheters to prevent foreign body-associated UTIs.

Fluoroquinolone Resistance in Salmonella and the Utility of Pefloxacin Disk Diffusion [corrected]

Fluoroquinolone resistance is a serious and increasingly common problem in Salmonella. Two companion studies in this issue of the Journal of Clinical Microbiology (E. Deak, R. Skov, J. A. Hindler, and R. M. Humphries, J Clin Microbiol 53:3405-3410, 2015, http://dx.doi.org/10.1128/JCM.01393-15; R. Skov, E. Matuschek, M. Sjölund-Karlsson, J. Åhman, A. Petersen, M. Stegger, M. Torpdahl, and G. Kahlmeter, J Clin Microbiol 53:3411-3417, 2015, http://dx.doi.org/10.1128/JCM.01287-15) provide data to support the use of pefloxacin disk diffusion as a convenient and inexpensive surrogate laboratory method to detect fluoroquinolone resistance in Salmonella when the direct measurement of fluoroquinolone MICs is not feasible [corrected]. Recently updated CLSI and EUCAST susceptibility breakpoints will help to optimize clinical outcomes and reduce the likelihood of emergent resistance.

Photochemical properties of gemifloxacin: a laser flash photolysis study

The photochemical properties of gemifloxacin (GEFX), a fluoroquinolone antibacterial drug that exhibits phototoxicity toward biological substrates, were studied in aqueous solutions by laser flash photolysis (LFP) and pulse radiolysis. GEFX triplet state ((3)GEFX(∗)) absorption spectra showed maximum absorption at 510nm. (3)GEFX(∗) was quenched by naproxen (NAP) via energy transfer with a rate constant of 1.2×10(8)dm(3)mol(-1)s(-1). The energy of (3)GEFX(∗) was 266kJmol(-1) and the transient absorption spectra showed direct evidence of electron transfer from 2'-deoxyguanosine-5'-monophosphate, N,N,N',N'-tetramethyl-p-phenylenediamine, and tryptophan to (3)GEFX(∗) with bimolecular reaction rate constants of 4.1×10(6), 2.0×10(7), and 2.2×10(7)dm(3)mol(-1)s(-1), respectively. The rate constants for reactions of GEFX with OH, eaq(-) were found to be 1.5×10(10) and 1.4×10(10)dm(3)mol(-1)s(-1), respectively. The mechanisms and products of the photosensitive damage of lysozyme were related to the GEFX concentration, irradiation time, and ambient conditions.