Extended-spectrum β-lactamase-producing Shigella strains in Israel, 2000–2004

Cluster of cases due to Shigella flexneri producing CTX-M-15 in Spain

The aim of our study was to delineate an outbreak of gastroenteritis caused by Shigella flexneri and affecting sixteen persons between May and June 2014 in Bilbao, Spain. All patients exhibited symptoms after consuming kebab in the same kebab shop.The outbreak is described through the clinical cases, the microbiological and molecular genetic diagnosis, and the epidemiologic investigation. Minimum inhibitory concentrations for ampicillin, amoxicillin plus clavulanic acid, third and fourth generation cephalosporins, carbapenems, monobactams, aminoglycosides, fluoroquinolones, co-trimoxazole, colistin and tigecycline were measured. The S. flexneri strains were screened by PCR for TEM, SHV, CTX-M beta-lactamases and plasmidic AmpCs and aac(6')-Ib gene. Serotyping, pulsed field gel-electrophoresis, conjugation assay, plasmid sizing by S1 enzyme digestion and Southern blot hybridization were accomplished.All the S. flexneri isolates proved to be serotype 2 and produced extended-spectrum beta-lactamase (ESBL). Carbapenems, fluoroquinolones, tigecycline, colistin, and co-trimoxazole remained active antibiotics. All the strains harboured blaCTX-M-15 and blaOXA-1 genes. The strains hosted two high-molecular weight plasmids of 100 and 230 kb, respectively. According to the hybridization assay blaCTX-M-15 was located on the plasmid of 230 kb. The identical pulsotype verified the presence of outbreak.Remarkable, that one of the food handlers has travelled recently to Pakistan, where ESBL-producing Shigella strains had been reported previously. To the best of our knowledge, this is the first outbreak caused by CTX-M-15-expressing S. flexneri in Spain and as well as in Europe.

Shigella: Antibiotic-Resistance Mechanisms And New Horizons For Treatment

Shigella spp. are a common cause of diarrheal disease and have remained an important pathogen responsible for increased rates of morbidity and mortality caused by dysentery each year around the globe. Antibiotic treatment of Shigella infections plays an essential role in reducing prevalence and death rates of the disease. However, treatment of these infections remains a challenge, due to the global rise in broad-spectrum resistance to many antibiotics. Drug resistance in Shigella spp. can result from many mechanisms, such as decrease in cellular permeability, extrusion of drugs by active efflux pumps, and overexpression of drug-modifying and -inactivating enzymes or target modification by mutation. Therefore, there is an increasing need for identification and evolution of alternative therapeutic strategies presenting innovative avenues against Shigella infections, as well as paying further attention to this infection. The current review focuses on various antibiotic-resistance mechanisms of Shigella spp. with a particular emphasis on epidemiology and new mechanisms of resistance and their acquisition, and also discusses the status of novel strategies for treatment of Shigella infection and vaccine candidates currently under evaluation in preclinical or clinical phases.

Comparison of phenotypic and WGS-derived antimicrobial resistance profiles of Shigella sonnei isolated from cases of diarrhoeal disease in England and Wales, 2015

Objectives

Phenotypic and genotypic methods for the detection of antimicrobial resistance (AMR) in Shigella sonnei in England and Wales were compared and evaluated.

Methods

WGS data from 341 isolates of S. sonnei isolated between June 2015 and January 2016 were mapped to genes known to be associated with phenotypic AMR. Antimicrobial susceptibility testing was performed on all viable isolates (n = 335).

Results

Fifteen of 335 isolates had a discrepancy between phenotypic and genotypic testing for 1 of the 10 antimicrobial classes tested, equating to 15 (0.45%) discordant results out of a possible 3350 isolate/antimicrobial combinations. All 15 mismatched results were genotypically resistant but phenotypically susceptible. Eleven of the 15 discrepancies were observed in streptomycin resistance profiles. The most common resistance profile was trimethoprim, sulphonamides, tetracyclines and streptomycin, occurring in 97 (28.4%) isolates. Resistances to ciprofloxacin and the third-generation cephalosporins, not detected in England and Wales prior to 2002, were identified in 18.2% and 12% of isolates, respectively. Three hundred and four (89.1%) isolates were MDR. There was no significant association between any of the AMR determinants tested and recent foreign travel in male or female cases. The number of isolates of S. sonnei harbouring blaTEM-1 and ermB/mphA was significantly higher in men who reported no recent travel outside the UK.

Conclusions

The use of WGS for routine public health surveillance is a reliable method for rapid detection of emerging AMR in isolates of S. sonnei.

Characterization of integrons, extended-spectrum β-lactamases, AmpC cephalosporinase, quinolone resistance, and molecular typing of Shigella spp. from Iran

INTRODUCTION

The wide distribution of extended-spectrum β-lactamase (ESBL) producing Shigella spp., along with the emergence of fluoroquinolone resistant isolates, is a serious threat to public health, posing a new challenge for the effective treatment of shigellosis. The purpose of this study was to determine the level of antimicrobial resistance, the presence of genes encoding resistance to cephalosporins, and plasmid-mediated quinolone resistance (PMQR) among the clinical isolates of Shigella spp. in Iran.

MATERIALS AND METHODS

A total of 142 Shigella isolates were collected from different parts of Iran. All of the cephalosporin resistant Shigella strains were selected based on ESBL and AmpC production. The presence of PMQR regions was assessed in ciprofloxacin-resistant isolates, and genetic relatedness in the isolates was determined.

RESULTS

Seventy-eight Shigella isolates were found to be resistant to extended-spectrum cephalosporin (ESC). The bla_CTX-M15 was the most prevalent cephalosporinase. Four ESBL-producing isolates were also resistant to ciprofloxacin. Among the PMQR regions, aac(6')-lb-cr gene was the most prevalent, as it was seen in 83.3% of the ciprofloxacin resistant isolates, while qnrA was positive in 16.7%. Clonal relatedness showed a limited variety of clones was responsible for Shigella infection in the region studied.

CONCLUSION

Overall, our findings indicated that a large number of ESBL producing Shigella spp. were mediated mainly by bla_CTX-M15. This study is the first report on ciprofloxacin-resistant ESBL-producing Shigella isolates from patients in Iran.

Plasmid-encoding extended-spectrum β-lactamase CTX-M-55 in a clinical Shigella sonnei strain, China

AIMS

To characterize a clinical Shigella sonnei strain harboring a conjugatable blaCTX-M-55-borne plasmid.

MATERIALS & METHODS

S. sonnei strain #1081 was isolated from a dysentery patient in China. A CTX-M-55-encoding plasmid harbored in this strain was transformed to Escherichia coli, and then its complete nucleotide sequence was determined by next generation sequencing. The MIC values of bacterial strains were tested by using Vitec(®) 2 (Biomerieux, Marcy l'Etoile, France).

RESULTS

Strain #1081 conferred the resistance to multiple beta-lactam antibiotics. blaCTX-M-55 was the only known antibiotic resistance gene and located in a 3090-bp ISEcp1-blaCTX-M-55-orf477 transposition unit carried by a conjugatable plasmid p1081-CTXM in #1081. The ISEcp1-mediated transposition provided a sole promoter, which was located adjacently upstream of the inverted repeat right element of ISEcp1, to drive the expression of CTX-M-55.

CONCLUSION

Plasmid p1081-CTXM was a close variant of the IncI2-type plasmid pHN1122-1 that was harbored in a faecal E. coli strain recovered from a dog in China, indicating the potential transfer of CTX-M-55-encoding plasmids from faecal flora E. coli to human pathogen S. sonnei.

Environmental monitoring of bacterial contamination and antibiotic resistance patterns of the fecal coliforms isolated from Cauvery River, a major drinking water source in Karnataka, India

The present study focuses prudent elucidation of microbial pollution and antibiotic sensitivity profiling of the fecal coliforms isolated from River Cauvery, a major drinking water source in Karnataka, India. Water samples were collected from ten hotspots during the year 2011-2012. The physiochemical characteristics and microbial count of water samples collected from most of the hotspots exhibited greater biological oxygen demand and bacterial count especially coliforms in comparison with control samples (p ≤ 0.01). The antibiotic sensitivity testing was performed using 48 antibiotics against the bacterial isolates by disk-diffusion assay. The current study showed that out of 848 bacterial isolates, 93.51% (n = 793) of the isolates were found to be multidrug-resistant to most of the current generation antibiotics. Among the major isolates, 96.46% (n = 273) of the isolates were found to be multidrug-resistant to 30 antibiotics and they were identified to be Escherichia coli by 16S rDNA gene sequencing. Similarly, 93.85% (n = 107), 94.49% (n = 103), and 90.22% (n = 157) of the isolates exhibited multiple drug resistance to 32, 40, and 37 antibiotics, and they were identified to be Enterobacter cloacae, Pseudomonas trivialis, and Shigella sonnei, respectively. The molecular studies suggested the prevalence of bla TEM genes in all the four isolates and dhfr gene in Escherichia coli and Sh. sonnei. Analogously, most of the other Gram-negative bacteria were found to be multidrug-resistant and the Gram-positive bacteria, Staphylococcus spp. isolated from the water samples were found to be methicillin and vancomycin-resistant Staphylococcus aureus. This is probably the first study elucidating the bacterial pollution and antibiotic sensitivity profiling of fecal coliforms isolated from River Cauvery, Karnataka, India.

Cephalosporin-resistant Shigella flexneri over 9 years (2001-09) in India

OBJECTIVES

To determine the pattern and antimicrobial resistance genes of cephalosporin resistance in Shigella flexneri and Shigella dysenteriae over 9 years.

METHODS

Isolates of Shigella (S. flexneri, n = 119 and S. dysenteriae, n = 24) were tested for resistance to ceftriaxone and cefepime by disc diffusion, for MIC by Etest and for extended-spectrum β-lactamase (ESBL) and AmpC production. The presence of antimicrobial resistance genes was investigated by PCR using specific primers for bla(TEM), bla(OXA-1), bla(CTX-M-15), bla(SHV) and bla(CMY-2) for all the isolates.

RESULTS

Twenty (16.8%) S. flexneri isolates were resistant/intermediately susceptible to ceftriaxone/cefepime, while all S. dysenteriae were susceptible. In S. flexneri isolates, the MIC(50) values of ceftriaxone and cefepime were found to be 0.032 and 0.125 mg/L, respectively, while their MIC(90) values were 12 and 8 mg/L, respectively. The MIC(50) and MIC(90) for S. dysenteriae were below 1 mg/L for ceftriaxone; however, for cefepime the MIC(90) was found to be 4 mg/L. Of the 20 resistant/intermediately susceptible S. flexneri isolates, 9 were positive for ESBL production and 4 for AmpC production by phenotypic tests. All 20 isolates were found to be positive for bla(TEM), 10 for bla(CTX-M-15), 8 for bla(OXA) and 7 for bla(CMY-2); none was positive for bla(SHV).

CONCLUSIONS

We report a high level of cephalosporin resistance with high MICs and ESBL- and AmpC-mediated antibiotic resistance in Shigella from north India.

Molecular characterization of multidrug-resistant Shigella species isolated from epidemic and endemic cases of shigellosis in India

Shigella species represent one of the growing numbers of antimicrobial-resistant bacteria in developing countries. Fluoroquinolone-resistant strains of Shigella dysenteriae type 1 and Shigella flexneri type 2a emerged in India during 2002 and 2003, respectively. Sixty strains of Shigella from different parts of India were analysed for antimicrobial susceptibility, the presence of the qnr plasmid, mutations in the quinolone resistance determining regions (QRDRs), fluoroquinolone accumulation, and the presence of other genes encoding resistance to various antimicrobials. Fluoroquinolone-resistant strains had mutations in gyrA and parC genes and had an active efflux system. They were also resistant to several other antimicrobials but were susceptible to azithromycin and ceftriaxone. The majority of the strains harboured genes encoding resistance to ampicillin (97 %), tetracycline (95 %), streptomycin (95 %) and chloramphenicol (94 %). PFGE analysis revealed clonality among strains of S. dysenteriae types 1 and 5, S. flexneri type 2a and Shigella boydii type 12.