Socioeconomic Determinants of Cipro-floxacin-Resistant Shigella Infections in Bangladeshi Children

Multidrug-resistant conjugative plasmid carrying mphA confers increased antimicrobial resistance in Shigella

Shigellosis remains a common gastrointestinal disease mostly in children < 5 years of age in developing countries. Azithromycin (AZM), a macrolide, is currently the first-line treatment for shigellosis in Bangladesh; ciprofloxacin (CIP) and ceftriaxone (CRO) are also used frequently. We aimed to evaluate the current epidemiology of antimicrobial resistance (AMR) and mechanism(s) of increasing macrolide resistance in Shigella in Bangladesh. A total of 2407 clinical isolates of Shigella from 2009 to 2016 were studied. Over the study period, Shigella sonnei was gradually increasing and become predominant (55%) over Shigella flexneri (36%) by 2016. We used CLSI-guided epidemiological cut-off value (ECV) for AZM in Shigella to set resistance breakpoints (zone-diameter ≤ 15 mm for S. flexneri and ≤ 11 mm for S. sonnei). Between 2009 and 2016, AZM resistance increased from 22% to approximately 60%, CIP resistance increased by 40%, and CRO resistance increased from zero to 15%. The mphA gene was the key macrolide resistance factor in Shigella; a 63MDa conjugative middle-range plasmid was harboring AZM and CRO resistance factors. Our findings show that, especially after 2014, there has been a rapid increase in resistance to the three most effective antibiotics. The rapid spread of macrolide (AZM) resistance genes among Shigella are driven by horizontal gene transfer rather than direct lineage.

Increasing trend of antibiotic resistance in Shigella in Bangladesh: a plasmid-mediated transfer of mphA macrolide resistance gene

Shigellosis remains a common gastrointestinal disease mostly in children <5 years of age in developing countries. Azithromycin (AZM), a macrolide, is currently the first-line treatment for shigellosis in Bangladesh; ciprofloxacin (CIP) and ceftriaxone (CRO) are also used frequently. We aimed to evaluate the current epidemiology of antimicrobial resistance (AMR) and mechanism(s) of increasing macrolide resistance in Shigella in Bangladesh. A total of 2407 clinical isolates of Shigella from 2009 to 2016 were studied. Over the study period, Shigella sonnei was gradually increasing and become predominant (55%) over Shigella flexneri (36%) by 2016. We used CLSI-guided epidemiological cut-off value (ECV) for AZM in Shigella to set resistance breakpoints (zone-diameter ≤ 15 mm for S. flexneri and ≤ 11 mm for S. sonnei). Between 2009 and 2016, AZM resistance increased from 22% to approximately 60%, CIP resistance increased by 40%, and CRO resistance increased from zero to 15%. The mphA gene was the key macrolide resistance factor in Shigella; a 63MDa conjugative middle-range plasmid was harboring AZM and CRO resistance factors. Our findings show that, especially after 2014, there has been a rapid increase in resistance to the three most effective antibiotics. The rapid spread of macrolide (AZM) resistance genes among Shigella are driven by horizontal gene transfer rather than direct lineage.

Prevalence of Antibiotic-Resistant Shigella spp. in Bangladesh: A Systematic Review and Meta-Analysis of 44,519 Samples

Shigella is the leading global etiological agent of shigellosis, especially in poor and underdeveloped or developing nations with insufficient sanitation such as Bangladesh. Antibiotics are the only treatment option for the shigellosis caused by Shigella spp. as no effective vaccine exists. However, the emergence of antimicrobial resistance (AMR) poses a serious global public health concern. Therefore, a systematic review and meta-analysis were conducted to establish the overall drug resistance pattern against Shigella spp. in Bangladesh. The databases of PubMed, Web of Science, Scopus, and Google Scholar were searched for relevant studies. This investigation comprised 28 studies with 44,519 samples. Forest and funnel plots showed any-drug, mono-drug, and multi-drug resistance. Any fluoroquinolone had a resistance rate of 61.9% (95% CI: 45.7-83.8%), any trimethoprim-sulfamethoxazole-60.8% (95% CI: 52.4-70.5%), any azithromycin-38.8% (95% CI: 19.6-76.9%), any nalidixic acid-36.2% (95% CI: 14.2-92.4%), any ampicillin-34.5% (95% CI: 25.0-47.8%), and any ciprofloxacin-31.1% (95% CI: 11.9-81.3%). Multi-drug-resistant Shigella spp. exhibited a prevalence of 33.4% (95% CI: 17.3-64.5%), compared to 2.6% to 3.8% for mono-drug-resistant strains. Since resistance to commonly used antibiotics and multidrug resistance were higher, a judicious use of antibiotics, the promotion of infection control measures, and the implementation of antimicrobial surveillance and monitoring programs are required to tackle the therapeutic challenges of shigellosis.

Virulence genes expression profiling of different Shigella flexneri serotypes in response to sub-inhibitory concentrations of azithromycin and ciprofloxacin

Background

Shigellosis is a self-limiting disease that antibiotic therapy could decrease its complications and duration. However, sublethal levels of antibiotics, may lead to alteration in disease state, besides its role in the emergence of resistant variants. To understand this link, we investigated diversity of Shigella serogroups in children with diarrhea, diversity of S. flexneri serotypes, cytotoxic potential, resistance patterns to antibiotics, and alteration in transcriptional expression of main virulence genes in response to sub-inhibitory concentrations of azithromycin and ciprofloxacin.

Results

The most frequently isolated serogroups were S. sonnei (70.3%), followed by S. flexneri (29.1%) and S. boydii (0.6%). Ten serotypes were characterized among the S. flexneri isolates, including 2b, 1b, 2a, 1c, 4a, 3a, 3b, 6 and X and/or Xv. Antimicrobial susceptibility testing showed low frequency of multi-drug resistance phenotype among S. flexneri isolates with minimum inhibitory concentrations (MIC) of 0.5–64 and 0.25–8 µg/mL for azithromycin and ciprofloxacin, respectively. Gene expression analysis showed upregulation of icsA in serotype 4a after exposure with azithromycin, whereas other genes in the VirF pathway were downregulated, and downregulation of virB in serotypes 2a and 3a after exposure with ciprofloxacin, while upregulation of noted genes was detected.

Conclusions

Alteration in transcription of key virulence genes of S. flexneri serotypes was shown in response to sublethal concentration of antibiotics. The detected incongruency in the extent of gene transcription proposed that diverse regulatory pathways are possibly mediating response to sub-MIC concentrations of antibiotics in S. flexneri.

Multidrug-resistant enteric pathogens in older children and adults with diarrhea in Bangladesh: epidemiology and risk factors

BACKGROUND

Antimicrobial resistance (AMR) is a global public health threat and is increasingly prevalent among enteric pathogens in low- and middle-income countries (LMICs). However, the burden of multidrug-resistant organisms (MDROs) in older children, adults, and elderly patients with acute diarrhea in LMICs is poorly understood. This study's aim was to characterize the prevalence of MDR enteric pathogens isolated from patients with acute diarrhea in Dhaka, Bangladesh, and assess a wide range of risk factors associated with MDR.

METHODS

This study was a secondary analysis of data collected from children over 5 years, adults, and elderly patients with acute diarrhea at the International Centre for Diarrhoeal Disease Research, Bangladesh Dhaka Hospital between March 2019 and March 2020. Clinical, historical, socio-environmental information, and a stool sample for culture and antimicrobial susceptibility testing were collected from each patient. Univariate statistics and multiple logistic regression were used to assess the prevalence of MDR among enteric pathogens and the association between independent variables and presence of MRDOs among culture-positive patients.

RESULTS

A total of 1198 patients had pathogens isolated by stool culture with antimicrobial susceptibility results. Among culture-positive patients, the prevalence of MDR was 54.3%. The prevalence of MDR was highest in Aeromonas spp. (81.5%), followed by Campylobacter spp. (72.1%), Vibrio cholerae (28.1%), Shigella spp. (26.2%), and Salmonella spp. (5.2%). Factors associated with having MDRO in multiple logistic regression included longer transport time to hospital (>90 min), greater stool frequency, prior antibiotic use prior to hospital presentation, and non-flush toilet use. However, pseudo-R2 was low 0.086, indicating that other unmeasured variables need to be considered to build a more robust predictive model of MDR.

CONCLUSIONS

MDR enteric pathogens were common in this study population with clinical, historical, and socio-environmental risk factors associated with MDROs. These findings may help guide clinical decision-making regarding antibiotic use and selection in patients at greatest risk of complications due to MDROs. Further prospective research is urgently needed to determine what additional factors place patients at greatest risk of MDRO, and the best strategies to mitigate the spread of MDR in enteric pathogens.

Clinical and socio-environmental determinants of multidrug-resistant vibrio cholerae 01 in older children and adults in Bangladesh

Objectives:

Few studies have evaluated determinants of multidrug-resistant (MDR) Vibrio cholerae O1 in older children and adults. This study aimed to characterize the prevalence of MDR V. cholerae O1 and associated risk factors among patients over five years of age in Bangladesh.

Methods:

Stool culture and antimicrobial susceptibility testing were performed as a part of a larger study at Dhaka Hospital in Bangladesh from March 2019–March 2020. Univariate statistics and multiple logistic regression were used to assess the association between a range of variables and MDR V. cholerae O1.

Results:

MDR was found in 175 of 623 (28.1%) V. cholerae O1 isolates. High levels of resistance were found to erythromycin (99.2%), trimethoprim-sulfamethoxazole (99.7%), and ampicillin (88.9%), while susceptibility was high to tetracyclines (99.7%), azithromycin (99.2%), ciprofloxacin (99.8%), and cephalosporins (98.6%). MDR was associated with prior antibiotic use, longer transport time to hospital, higher income, non-flush toilet use, greater stool frequency, lower blood pressure, lower mid-upper arm circumference, and lower percent dehydration.

Conclusions:

MDR V. cholerae O1 was common among patients over five in an urban hospital in Bangladesh. Significant factors associated with MDR may be actionable in identifying patients with a high likelihood of MDR.