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.

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Shigella: Antibiotic-Resistance Mechanisms And New Horizons For Treatment.

As a growing threat to human and animal health, antimicrobial resistance (AMR) has become a central public-health topic. Largescale surveillance systems, such as the National Antimicrobial Resistance Monitoring System (NARMS), are now established to monitor and provide guidance regarding AMR, but comprehensive literature on AMR among NHP is sparse. This study provides data regarding current antimicrobial use strategies and the prevalence of AMR in zoonotic bacteria recovered from NHP within biomedical research institutions. We focused on 4 enteric bacteria: Shigella flexneri, Yersinia enterocolitica, Y. pseudotuberculosis, and Campylobacter jejuni. Fifteen veterinarians, 7 biomedical research institutions, and 4 diagnostic laboratories participated, providing susceptibility test results from January 2012 through April 2015. Veterinarians primarily treated cases caused by S. flexneri, Y. enterocolitica, and Y. pseudotuberculosis with enrofloxacin but treated C. jejuni cases with azithromycin and tylosin. All isolates were susceptible to the associated primary antimicrobial but often showed resistance to others. Specifically, S. flexneri isolates frequently were resistant to erythromycin (87.5%), doxycycline (73.7%), and tetracycline (38.3%); Y. enterocolitica isolates to ampicillin (100%) and cefazolin (93.6%); and C. jejuni isolates to methicillin (99.5%) and cephalothin (97.5%). None of the 58 Y. pseudotuber-culosis isolates was resistant to any tested antimicrobial. Notably, resistance patterns were not shared between this study's NHP isolates and human isolates presented by NARMS. Our findings indicate that zoonotic bacteria from NHP diagnostic samples are broadly susceptible to the antimicrobials used to treat the clinical infections. These results can help veterinarians ensure effective antimicrobial therapy and protect staff by minimizing occupational risk.

Antimicrobial Use for and Resistance of Zoonotic Bacteria Recovered from Nonhuman Primates.

Background The aim of this study was to longitudinally investigate the prevalence and characterization of Campylobacter spp. from non-human primates primate (NHP) with a history of endemic diarrhea housed at Como Park Zoo. Methods Fecal samples from 33 symptom-free NHP belonging to eight different species were collected weekly for 9 weeks. Species-level characterization and phylogenetic analysis of isolates included biochemical testing and 16S rRNA sequencing. Results Campylobacter spp. were isolated from the feces of 42% (14/33) of the primates. Three Campylobacter spp. (C upsaliensis, C jejuni, and novel Campylobacter sp.) were identified from three NHP species. A possible positive host Campylobacter species-specificity was observed. However, no statistical association was observed between the isolation of Campylobacter spp. and age and sex of the animal. Conclusions The study revealed the value of conducting repeated fecal sampling to establish the overall prevalence of Campylobacter in zoo-maintained NHP; it also importantly identifies a novel Campylobacter sp. isolated from white-faced saki monkeys.

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Characterization of Campylobacter jejuni, Campylobacter upsaliensis, and a novel Campylobacter sp. in a captive non-human primate zoological collection.

The purpose of this study was to find out the mechanism of quinolone resistance in Shigella sp. isolated from environmental water samples from various parts of Kolkata, India. Out of 196 Shigella sp. isolated from 2014 to 2017, we selected 32 Shigella isolates for antimicrobial susceptibility tests. The minimum inhibitory concentrations (MIC) for quinolones ranged from 30 to 50 μg ml-1 for ofloxacin, 5-20 μg ml-1 for ciprofloxacin and 20-30 μg ml-1 for norfloxacin. A few amino acid changes were found in quinolone resistance determining region (QRDR) of gyrA. Mutations in gyrA lead to a higher increment of MIC of quinolones. Among the plasmid-mediated (PMQR) quinolone resistance genes investigated, qnrB and aac(6')-lb-cr genes were found in all isolates. qnrA and qnrS were found in 25% and 62% of the isolates, respectively. ipaH gene was found in all of the isolates followed by the presence of other virulence genes ial, sen and stx1. Almost all the isolates having high MICs showed efflux pump activity in drug accumulation assay. All the mechanisms may or may not be present in a single strain. Several types of efflux pumps, presence of PMQR genes and mutations in drug target site of QRDR region may play the crucial role for resistance in our isolates.

Development of quinolone resistance and prevalence of different virulence genes among Shigella flexneri and Shigella dysenteriae in environmental water samples

Cotton-top tamarins (CTTs) are an ideal model of human inflammatory bowel disease (IBD) because these animals develop multigenerational, lower bowel cancer. We previously isolated and characterized a novel enterohepatic Helicobacter species, Helicobacter saguini, from CTTs with IBD and documented that H. saguini infection in germfree C57BL IL-10-/- mice recapitulates IBD, suggesting that H. saguini influences IBD etiopathogenesis. In this study, we utilized a germfree IL-10-/- model to illustrate that H. saguini infection can naturally transmit and infect four generations and cause significant intestinal inflammatory pathology. Additionally, whole-genome sequencing of representative H. saguini isolates from each generation of IL-10-/- mice revealed gene mutations suggestive of multigenerational evolution. Overall, these results support that specific bacterial species with pathogenic potential, like H. saguini, are transmissible microorganisms in the etiopathogenesis of IBD in CTTs and reinforces the importance of specific microbiota in the pathogenesis of IBD in humans.IMPORTANCE While family history is a significant risk factor for developing inflammatory bowel disease (IBD), it is unclear whether the microbiome from parents is a transmissible influence on disease in their offspring. Furthermore, it is unknown whether IBD-associated microbes undergo genomic adaptations during multigenerational transmission and chronic colonization in their hosts. Herein, we show that a single bacterial species, Helicobacter saguini, isolated from a nonhuman primate species with familial IBD, is transmissible from parent to offspring in germfree IL-10-/- mice and causes multigenerational IBD. Additionally, whole-genome sequence analysis of H. saguini isolated from different mouse generations identified microevolutions in environmental interaction, nutrient metabolism, and virulence factor genes that suggest that multigenerational transmission may promote adaptations related to colonization and survival in new hosts and chronic inflammatory environments. The findings from our study highlight the importance of specific bacterial species with pathogenic potential, like H. saguini, as transmissible microorganisms in the etiopathogenesis of IBD.

https://journals.asm.org/doi/pdf/10.1128/mSphere.00011-20

Natural Transmission of Helicobacter saguini Causes Multigenerational Inflammatory Bowel Disease in C57/129 IL-10 -/- Mice

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.

Ellen Marie Buckley Jordan

Papers

Plasmid-Mediated Quinolone Resistance in Shigella flexneri Isolated From Macaques