Comparison of antimicrobial susceptibility between invasive and non-invasive Shigella organisms

ESBL Producing Escherichia coli in Faecal Sludge Treatment Plants: An Invisible Threat to Public Health in Rohingya Camps, Cox's Bazar, Bangladesh

Introduction: Human faecal sludge contains diverse harmful microorganisms, making it hazardous to the environment and public health if it is discharged untreated. Faecal sludge is one of the major sources of E. coli that can produce extended-spectrum β-lactamases (ESBLs).

Objective: This study aimed to investigate the prevalence and molecular characterization of ESBL-producing E. coli in faecal sludge samples collected from faecal sludge treatment plants (FSTPs) in Rohingya camps, Bangladesh.

Methods: ESBL producing E. coli were screened by cultural as well as molecular methods and further characterized for their major ESBL genes, plasmid profiles, pathotypes, antibiotic resistance patterns, conjugation ability, and genetic similarity.

Results: Of 296 isolates, 180 were phenotypically positive for ESBL. All the isolates, except one, contained at least one ESBL gene that was tested (bla_CTX−M−1, bla_CTX−M−2, bla_CTX−M−8, bla_CTX−M−9, bla_CTX−M−15, bla_CTX−M−25, bla_TEM, and bla_SHV). From plasmid profiling, it was observed that plasmids of 1–211 MDa were found in 84% (151/180) of the isolates. Besides, 13% (24/180) of the isolates possessed diarrhoeagenic virulence genes. From the remaining isolates, around 51% (79/156) harbored at least one virulence gene that is associated with the extraintestinal pathogenicity of E. coli. Moreover, 4% (3/156) of the isolates were detected to be potential extraintestinal pathogenic E. coli (ExPEC) strains. Additionally, all the diarrhoeagenic and ExPEC strains showed resistance to three or more antibiotic groups which indicate their multidrug-resistant potential. ERIC-PCR differentiated these pathogenic isolates into seven clusters. In addition to this, 16 out of 35 tested isolates transferred plasmids of 32–112 MDa to E. coli J53 recipient strain.

Conclusion: The present study implies that the faecal sludge samples examined here could be a potential origin for spreading MDR pathogenic ESBL-producing E. coli. The exposure of Rohingya individuals, living in overcrowded camps, to these organisms poses a severe threat to their health.

Antimicrobial resistance, virulence factors and genetic diversity of Escherichia coli isolates from household water supply in Dhaka, Bangladesh

BACKGROUND

Unsafe water supplies continue to raise public health concerns, especially in urban areas in low resource countries. To understand the extent of public health risk attributed to supply water in Dhaka city, Bangladesh, Escherichia coli isolated from tap water samples collected from different locations of the city were characterized for their antibiotic resistance, pathogenic properties and genetic diversity.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 233 E. coli isolates obtained from 175 tap water samples were analysed for susceptibility to 16 different antibiotics and for the presence of genes associated with virulence and antibiotic resistance. Nearly 36% (n = 84) of the isolates were multi-drug(≥ 3 classes of antibiotics) resistant (MDR) and 26% (n = 22) of these were positive for extended spectrum β-lactamase (ESBL). Of the 22 ESBL-producers, 20 were positive for bla CTX-M-15, 7 for bla OXA-1-group (all had bla OXA-47) and 2 for bla CMY-2. Quinolone resistance genes, qnrS and qnrB were detected in 6 and 2 isolates, respectively. Around 7% (n = 16) of the isolates carried virulence gene(s) characteristic of pathogenic E. coli; 11 of these contained lt and/or st and thus belonged to enterotoxigenic E. coli and 5 contained bfp and eae and thus belonged to enteropathogenic E. coli. All MDR isolates carried multiple plasmids (2 to 8) of varying sizes ranging from 1.2 to >120 MDa. Ampicillin and ceftriaxone resistance were co-transferred in conjugative plasmids of 70 to 100 MDa in size, while ampicillin, trimethoprim-sulfamethoxazole and tetracycline resistance were co-transferred in conjugative plasmids of 50 to 90 MDa. Pulsed-field gel electrophoresis analysis revealed diverse genetic fingerprints of pathogenic isolates.

SIGNIFICANCE

Multi-drug resistant E. coli are wide spread in public water supply in Dhaka city, Bangladesh. Transmission of resistant bacteria and plasmids through supply water pose serious threats to public health in urban areas.

Differential expression of ompC and ompF in multidrug-resistant Shigella dysenteriae and Shigella flexneri by aqueous extract of Aegle marmelos, altering its susceptibility toward beta-lactam antibiotics

Steadily increasing resistance among Shigella to beta-lactams, aminoglycosides, and tetracycline has compromised the utility of these commonly used antimicrobial agents. Also, undesirable side effects of certain antibiotics have triggered immense interest in search of alternative therapies using medicinal plants. One such medicinal plant used since ancient times to cure diarrhea is Aegle marmelos. The present study exemplifies the susceptibility of beta-lactam-resistant Shigella dysenteriae and Shigella flexneri toward beta-lactam antibiotics, when grown in the presence of aqueous extract of A. marmelos (AEAM), by altering porin channels. This was demonstrated by antibiotic sensitivity test using disc diffusion method and MIC test. Susceptibility toward beta-lactam antibiotic is associated with changes in outer membrane porins OmpC (approximately 42 kDa) and OmpF (approximately 38 kDa) and cytosolic proteins of approximately 26 kDa, OmpR, a transcriptional regulator. Expression of ompF is increased in S. dysenteriae and S. flexneri grown in the presence of AEAM due to down-regulation of ompR, which is conformed by reverse transcriptase polymerase chain reaction. In conclusion, AEAM influences susceptibility of beta-lactam-resistant Shigella toward beta-lactam antibiotics by altering porin channels. Hence, AEAM along with beta-lactam can be used for treatment of multidrug-resistant Shigella.

A Schiff base complex of chromium(III): an efficient inhibitor for the pathogenic and invasive potential of Shigella dysenteriae

A Schiff base complex of chromium(III), transdiaqua[N,N'ethylenebis (salicylideneimine)chromium(III)]perchlorate, [Cr(salen)(OH(2))(2)](+), was found to have an inhibitory effect on the growth of Shigella dysenteriae. The chromium(III) complex was found to cure (remove) the invasive plasmid and thereby render the microbe more sensitive to the tested antibiotics. The loss in the catalytic activity of the isolated endo-alpha-N-acetyl galactosaminidase on mucin as a substrate was also observed in the presence of [Cr(salen)(OH(2))(2)](+). This suggests that [Cr(salen)(OH(2))(2)](+) is toxic to the microbe and could make the microbe non-pathogenic and non-invasive, thus establishing its role in microbiological applications to reduce the toxic potentials of a microbe.