Role of DNA gyrase and topoisomerase IV mutations in fluoroquinolone resistance of Capnocytophaga spp. clinical isolates and laboratory mutants

Genomic alterations involved in fluoroquinolone resistance development in Staphylococcus aureus

AIM

Fluoroquinolone (FQ) is a potent antibiotic class. However, resistance to this class emerges quickly which hinders its application. In this study, mechanisms leading to the emergence of multidrug-resistant (MDR) Staphylococcus aureus (S. aureus) strains under FQ exposure were investigated.

METHODOLOGY

S. aureus ATCC 29213 was serially exposed to ciprofloxacin (CIP), ofloxacin (OFL), or levofloxacin (LEV) at sub-minimum inhibitory concentrations (sub-MICs) for 12 days to obtain S. aureus -1 strains and antibiotic-free cultured for another 10 days to obtain S. aureus-2 strains. The whole genome (WGS) and target sequencing were applied to analyze genomic alterations; and RT-qPCR was used to access the expressions of efflux-related genes, alternative sigma factors, and genes involved in FQ resistance.

RESULTS

A strong and irreversible increase of MICs was observed in all applied FQs (32 to 128 times) in all S. aureus-1 and remained 16 to 32 times in all S. aureus-2. WGS indicated 10 noticeable mutations occurring in all FQ-exposed S. aureus including 2 insdel mutations in SACOL0573 and rimI; a synonymous mutation in hslO; and 7 missense mutations located in an untranslated region. GrlA, was found mutated (R570H) in all S. aureus-1 and -2. Genes encoding for efflux pumps and their regulator (norA, norB, norC, and mgrA); alternative sigma factors (sigB and sigS); acetyltransferase (rimI); methicillin resistance (fmtB); and hypothetical protein BJI72_0645 were overexpressed in FQ-exposed strains.

CONCLUSION

The emergence of MDR S. aureus was associated with the mutations in the FQ-target sequences and the overexpression of efflux pump systems and their regulators.

Purpura fulminans secondary to Capnocytophaga canimorsus bacteraemia following a dog bite: A case report and review of literature

Introduction

Infection due to Capnocytophaga canimorsus may result in a wide variety of clinical presentations. We present a case of life-threatening Capnocytophaga canimorsus infection with evolution of ecchymosis to purpura fulminans.

Case description

We present a case of a 43-year-old male with a history of excessive alcohol consumption who presented with features of sepsis following a dog bite. This was associated with a striking, widespread purpuric rash. A causative pathogen, C. canimorsus was identified through blood culture and 16S RNA sequencing. His initially purpuric rash underwent bullous transformation and was diagnosed clinically as purpura fulminans, confirmed on skin biopsy. He made a full recovery with prompt antimicrobial therapy, initially with co-amoxiclav but escalated to clindamycin and meropenem due to clinical deterioration and concerns of beta-lactamase resistance.

Discussion

β-Lactamase producing Capnocytophaga strains are of increasing concern. This particular concern is reflected in our case as 5 days into treatment with β-lactamase inhibitor combination therapy the patients clinical condition deteriorated but demonstrably improved on switching to a carbapenem.The development of biopsy proven purpura fulminans in this immunocompetent case is a rare severe manifestation of the previously reported manifestation of disseminated intravascular coagulation (DIC) in Capnocytophaga bacteraemia. The case reported describes characteristics common with other DIC presentations such as the presence of clinical risk factors (history of excessive alcohol consumption) and symmetrical involvement. However, an unusual feature in that initial purpuric lesions were followed by the development of a bullous appearance and peripheral necrotic features concerning for purpura fulminans and confirmed with skin biopsy.

Jadomycins: A potential chemotherapy for multi-drug resistant metastatic breast cancer

Breast cancer causes the most cancer fatalities in women worldwide. Approximately one-third of breast cancers metastasize, or spread from primary tumors to other tissues, and have a 70% 5-year mortality rate. Current breast cancer treatments like doxorubicin and paclitaxel become ineffective when breast cancer cells develop multi-drug resistance and overexpress ATP-binding cassette transporters, as the transporters cause a substantial efflux of the chemotherapies. Jadomycins, a group of molecules isolated from Streptomyces venezuelae ISP5230, are shown to be cytotoxic against a variety of cancers, especially breast cancer. Furthermore, jadomycins retain their cytotoxic properties in multi-drug resistant breast cancer cells, as they are not expelled through ATP-binding cassette transporters. Here, we describe the research that supports the potential use of jadomycins as a novel chemotherapy in the treatment of multi-drug resistant, metastatic breast cancer. We present the supportive findings, as well as the mechanisms of action investigated thus far. These include copper-mediated reactive oxygen species generation, aurora B kinase inhibition, and topoisomerase IIα and IIβ inhibition. We also suggest future directions of jadomycin research, which will help to determine if jadomycins can be used as a breast cancer chemotherapy in clinical practice.

DNA Gyrase and Topoisomerase IV Mutations and their effect on Quinolones Resistant Proteus mirabilis among UTIs Patients

Objective:

This study aimed to highlight the importance of mutations within Proteus mirabilis genome that are related to fluoroquinolone resistance.

Methods:

This is a cross sectional study performed in different teaching hospitals in Khartoum State from June 2016 to May 2017. A total of (120) P mirabilis isolates from patients with symptoms of UTIs attending different hospitals in Khartoum State were examined. First, modified Kurby Bauer method was performed for phenotypical detection of resistant isolates. Then polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) followed by sequencing were applied for detection of mutations in GyrA, GyrB, ParC and ParE genes of isolates.

Results:

P. mirabilis showed 30% resistance to ciprofloxacin. All samples revealed mutation at (serine 83) of GyrA and (serine 84) of ParC by Hinf1 restriction endonuclease digestion. Sequencing was performed for 12 samples. For each gene, two resistant and one susceptible strains were randomly selected. The mutations associated with ciprofloxacin resistant P. mirabilis were as follows; (1/3) GyrA (Ser 83 to Ile) and (2/3) ParC (Ser 81 to Ile). Also it revealed silent mutations at codons of GyrB 474 leucine (3/3), 585 valine (2/3), 612 histidine (1/3) and 639 asparagine (1/3) and ParE 469 isoleucine (2/3), 531 aspartic (2/3) and 533 glycine (1/3).

Conclusions:

Ciprofloxacin resistance in P. mirabilis could be monitored through detection of mutations within DNA gyrase (encoded by gyrA and gyrB) and topoisomerase IV (encoded by parC and parE).

Screening for prevalence and abundance of Capnocytophaga spp by analyzing NGS data: A scoping review

BACKGROUND

Capnocytophaga spp. are commensal bacteria of the oral cavity and constitute a genus of the core microbiome.

OBJECTIVE

This genus is responsible for many local and systemic conditions in both the immunocompetent and immunocompromised patients, but its beneficial or deleterious role in the microbiota has been little explored.

DESIGN

Online databases were used to identify papers published from 1999 to 2019 based on next-generation sequencing (NGS) data to study comparative trials. Work using other identification methods, case reports, reviews, and non-comparative clinical trials was excluded.

RESULTS AND CONCLUSION

We selected 42 papers from among 668 publications. They showed a link between the abundance of Capnocytophaga spp. in the oral microbiota and various local pathologies (higher for gingivitis and halitosis; lower in active smokers, etc.) or systemic diseases (higher for cancer and carcinomas, IgA nephropathy, etc.). After discussing the limits inherent to the NGS techniques, we present several technical and biological hypotheses to explain the diversity of results observed between studies, as well as the links between the higher or lower abundance of Capnocytophaga spp and the appearance of local or systemic conditions and diseases.

Quinolone antibiotics

The quinolone antibiotics arose in the early 1960s, with the first examples possessing a narrow-spectrum of activity with unfavorable pharmacokinetic properties. Over time, the development of new quinolone antibiotics has led to improved analogues with an expanded spectrum and high efficacy. Nowadays, quinolones are widely used for treating a variety of infections. Quinolones are broad-spectrum antibiotics that are active against both Gram-positive and Gram-negative bacteria, including mycobacteria, and anaerobes. They exert their actions by inhibiting bacterial nucleic acid synthesis through disrupting the enzymes topoisomerase IV and DNA gyrase, and by causing breakage of bacterial chromosomes. However, bacteria have acquired resistance to quinolones, similar to other antibacterial agents, due to the overuse of these drugs. Mechanisms contributing to quinolone resistance are mediated by chromosomal mutations and/or plasmid gene uptake that alter the topoisomerase targets, modify the quinolone, and/or reduce drug accumulation by either decreased uptake or increased efflux. This review discusses the development of this class of antibiotics in terms of potency, pharmacokinetics and toxicity, along with the resistance mechanisms which reduce the quinolones' activity against pathogens. Potential strategies for future generations of quinolone antibiotics with enhanced activity against resistant strains are suggested.

Capnocytophaga sputigena bacteremia in a neutropenic host

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Capnocytophaga belong to the oral microbiota.

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Capnocytophaga bacteremia is uncommon.

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Capnocytophaga identification has evolved with the advent of MALDI TOF-MS.

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Capnocytophaga treatment is uncomplicated, although further insights into drug resistance development has been reported and need to be considered in the treatment.

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Capnocytophaga treatment may be complicated by drug resistance development.

Capnocytophaga species belong to the oral microbiota but are not a common cause of infection in febrile neutropenia. Nevertheless, neutropenia can cause bacteremia associated with mucositis, with lower rates of mortality. While empirical therapy with beta-lactams is generally effective, there is concern about the emergence of bacterial resistance. We present a case of a febrile neutropenic patient with mucositis presenting with C. sputigena bacteremia.

Lung abscess following bronchoscopy due to multidrug-resistant Capnocytophaga sputigena adjacent to lung cancer with high PD-L1 expression

Lung abscess following flexible bronchoscopy is a rare and sometimes fatal iatrogenic complication. Here, we report the first case of a lung abscess caused by multidrug-resistant Capnocytophaga sputigena following bronchoscopy. A 67-year-old man underwent bronchoscopy to evaluate a lung mass. Seven days after transbronchial lung biopsy, he presented with an abscess formation in a lung mass. Empirical antibiotic therapy, including with garenoxacin, ampicillin/sulbactam, clindamycin and cefepime, was ineffective. Percutaneous needle aspiration of lung abscess yielded C. sputigena resistant to multiple antibiotics but remained susceptible to carbapenem. He was successfully treated by the combination therapy with surgery and with approximately 6 weeks of intravenous carbapenem. Finally he was diagnosed with a lung abscess with adenocarcinoma expressing high levels of programmed cell death ligand 1. The emergence of multidrug-resistant Capnocytophaga species is a serious concern for effective antimicrobial therapy. Clinicians should consider multidrug-resistant C. sputigena as a causative pathogen of lung abscess when it is refractory to antimicrobial treatment.