Dataset Information

Fluoroquinolone resistance mechanisms of Shigella flexneri isolated in Bangladesh.

ABSTRACT:

Objective

To investigate the prevalence and mechanisms of fluoroquinolone resistance in Shigella species isolated in Bangladesh and to compare with similar strains isolated in China.

Methods

A total of 3789 Shigella isolates collected from Clinical Microbiology Laboratory of icddr,b, during 2004-2010 were analyzed for antibiotic susceptibility. Analysis of plasmids, plasmid-mediated quinolone-resistance genes, PFGE, and sequencing of genes of the quinolone-resistance-determining regions (QRDR) were conducted in representative strains isolated in Bangladesh and compared with strains isolated in Zhengding, China. In addition, the role of efflux-pump was studied by using the efflux-pump inhibitor carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

Results

Resistance to ciprofloxacin in Shigella species increased from 0% in 2004 to 44% in 2010 and S. flexneri was the predominant species. Of Shigella spp, ciprofloxacin resistant (CipR) strains were mostly found among S. flexneri (8.3%), followed by S. sonnei (1.5%). Within S. flexneri (n?=?2181), 14.5% were resistance to ciprofloxacin of which serotype 2a was predominant (96%). MIC of ciprofloxacin, norfloxacin, and ofloxacin were 6-32 mg/L, 8-32 mg/L, and 8-24 mg/L, respectively in S. flexneri 2a isolates. Sequencing of QRDR genes of resistant isolates showed double mutations in gyrA gene (Ser83Leu, Asp87Asn/Gly) and single mutation in parC gene (Ser80Ile). A difference in amino acid substitution at position 87 was found between strains isolated in Bangladesh (Asp87Asn) and China (Asp87Gly) except for one. A novel mutation at position 211 (His?Tyr) in gyrA gene was detected only in the Bangladeshi strains. Susceptibility to ciprofloxacin was increased by the presence of CCCP indicating the involvement of energy dependent active efflux pumps. A single PFGE type was found in isolates from Bangladesh and China suggesting their genetic relatedness.

Conclusions

Emergence of fluoroquinolone resistance in Shigella undermines a major challenge in current treatment strategies which needs to be followed up by using empirical therapeutic strategies.

SUBMITTER: Azmi IJ

PROVIDER: S-EPMC4100904 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Publications

Fluoroquinolone resistance mechanisms of Shigella flexneri isolated in Bangladesh.

Azmi Ishrat J IJ Khajanchi Bijay K BK Akter Fatema F Hasan Trisheeta N TN Shahnaij Mohammad M Akter Mahmuda M Banik Atanu A Sultana Halima H Hossain Mohammad A MA Ahmed Mohammad K MK Faruque Shah M SM Talukder Kaisar A KA

PloS one 20140716 7

<h4>Objective</h4>To investigate the prevalence and mechanisms of fluoroquinolone resistance in Shigella species isolated in Bangladesh and to compare with similar strains isolated in China.<h4>Methods</h4>A total of 3789 Shigella isolates collected from Clinical Microbiology Laboratory of icddr,b, during 2004-2010 were analyzed for antibiotic susceptibility. Analysis of plasmids, plasmid-mediated quinolone-resistance genes, PFGE, and sequencing of genes of the quinolone-resistance-determining r ...[more]

PMID: 25028972

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Project description:Non-human primates (NHPs) for biomedical research are commonly infected with Shigella spp. that can cause acute dysentery or chronic episodic diarrhea. These animals are often prophylactically and clinically treated with quinolone antibiotics to eradicate these possible infections. However, chromosomally- and plasmid-mediated antibiotic resistance has become an emerging concern for species in the family Enterobacteriaceae. In this study, five individual isolates of multi-drug resistant Shigella flexneri were isolated from the feces of three macaques. Antibiotic susceptibility testing confirmed resistance or decreased susceptibility to ampicillin, amoxicillin-clavulanic acid, cephalosporins, gentamicin, tetracycline, ciprofloxacin, enrofloxacin, levofloxacin, and nalidixic acid. S. flexneri isolates were susceptible to trimethoprim-sulfamethoxazole, and this drug was used to eradicate infection in two of the macaques. Plasmid DNA from all isolates was positive for the plasmid-encoded quinolone resistance gene qnrS, but not qnrA and qnrB. Conjugation and transformation of plasmid DNA from several S. flexneri isolates into antibiotic-susceptible Escherichia coli strains conferred the recipients with resistance or decreased susceptibility to quinolones and beta-lactams. Genome sequencing of two representative S. flexneri isolates identified the qnrS gene on a plasmid-like contig. These contigs showed >99% homology to plasmid sequences previously characterized from quinolone-resistant Shigella flexneri 2a and Salmonella enterica strains. Other antibiotic resistance genes and virulence factor genes were also identified in chromosome and plasmid sequences in these genomes. The findings from this study indicate macaques harbor pathogenic S. flexneri strains with chromosomally- and plasmid-encoded antibiotic resistance genes. To our knowledge, this is the first report of plasmid-mediated quinolone resistance in S. flexneri isolated from NHPs and warrants isolation and antibiotic testing of enteric pathogens before treating macaques with quinolones prophylactically or therapeutically.

Project description:A significant cause of shigellosis in Bangladesh and other developing countries is Shigella flexneri serotype 6. This serotype has been subtyped, on the basis of the absence or presence of a group-specific antigen, E1037, into S. flexneri 6a and 6b, respectively. Here, we provided rationales for the subclassification, using several phenotypic and molecular tools. A set of S. flexneri 6a and 6b strains isolated between 1997 and 2015 were characterized by analyzing their biochemical properties, plasmid profiles, virulence markers, pulsed-field gel electrophoresis (PFGE) results, and ribotype. Additionally, the genomic relatedness of these subserotypes was investigated with global isolates of serotype 6 using publicly available genomes. Both subserotypes of S. flexneri 6 agglutinated with monoclonal antiserum against S. flexneri (MASF) B and type VI-specific antiserum (MASF VI) and were PCR positive for O-antigen flippase-specific genes and virulence markers (ipaH, ial, sen, and sigA). Unlike S. flexneri 6a strains, S. flexneri 6b strains seroagglutinated with anti-E1037 antibodies, MASF IV-I. Notably, these two antigenically distinct subserotypes were clonally diverse, showing two distinct PFGE patterns following the digestion of chromosomal DNA with either XbaI or IceuI. In addition, hybridization of a 16S rRNA gene probe with HindIII-digested genomic DNA yielded two distinguishing ribotypes. Genomic comparison of S. flexneri subserotype 6a and 6b strains from Bangladesh indicated that, although these strains were in genomic synteny, the majority of them formed a unique phylogroup (PG-4) that was missing for the global isolates. This study supports the subserotyping and emphasizes the need for global monitoring of the S. flexneri subserotypes 6a and 6b. IMPORTANCE Shigella flexneri serotype 6 is one of the predominant serotypes among shigellosis cases in Bangladesh. Characterization of a novel subserotype of S. flexneri 6 (VI:E1037), agglutinated with type 6-specific antibody and anti-E1037, indicates a unique evolutionary ancestry. PFGE genotyping supports the finding that these two antigenically distinct subserotypes are clonally diverse. A phylogenetic study based on single-nucleotide polymorphism (SNP) data revealed that these two subserotypes were in genomic synteny, although their genomes were reduced. Interestingly, a majority of the S. flexneri 6 strains isolated from Bangladesh form a novel phylogenetic cluster. Therefore, this report underpins the global monitoring and tracking of the novel subserotype.

Dataset Information

Fluoroquinolone resistance mechanisms of Shigella flexneri isolated in Bangladesh.

Objective

Methods

Results

Conclusions

Publications

Fluoroquinolone resistance mechanisms of Shigella flexneri isolated in Bangladesh.

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