Foodborne Outbreak of Extended Spectrum Beta-lactamase Producing Shigella sonnei Associated with Contaminated Spring Onions in the United Kingdom.

Globalization of the food supply chain has created conditions favorable for emergence and spread of multidrug-resistant (MDR) foodborne pathogens. In November 2021, the UK Health Security Agency detected an outbreak of 17 cases infected with the same strain of MDR extended spectrum beta-lactamase (ESBL)-producing Shigella sonnei. Phylogenetic analysis of whole-genome sequencing data revealed the outbreak was closely related to strains of S. sonnei isolated from travelers returning to the UK from Egypt. None of the outbreak cases reported travel and all 17 cases reported eating food from a restaurant/food outlet in the week prior to symptom onset, of which 11/17 (64.7%) ate at branches of the same national restaurant franchise. All 17 cases were adults and 14/17 (82.4%) were female. Ingredient-level analyses of the meals consumed by the cases identified spring onions as the common ingredient. Food chain investigations revealed that the spring onions served at the implicated restaurants could be traced back to a single Egyptian producer. The foodborne transmission of ESBL-producing bacteria is an emerging global health concern, and concerted action from all stakeholders is required to ensure an effective response to mitigate the risks to public health.

Amoxicillin therapy of poultry flocks: effect upon the selection of amoxicillin-resistant commensal Campylobacter spp.

BACKGROUND: The aim of this study was to investigate the effect of amoxicillin therapy of poultry flocks upon the persistence of commensal Campylobacter spp. and the incidence of antibiotic resistance. METHODS: Four poultry flocks naturally colonized with Campylobacter were treated with amoxicillin and monitored before, during and up to 4 weeks post-treatment. The numbers of Campylobacter were determined and the isolates speciated and typed by flaA short variable region (SVR) sequence analysis and PFGE. The susceptibility of the isolates to antibiotics, presence of the Cj0299 gene encoding a beta-lactamase and beta-lactamase production (nitrocefin hydrolysis) were also determined. RESULTS: Amoxicillin-resistant Campylobacter were isolated from Flock 1 before and during treatment, but Campylobacter were not detected afterwards. Flock 2 was colonized by amoxicillin-susceptible strains throughout sampling. No amoxicillin-resistant isolates arose during or after treatment. Flock 3 contained amoxicillin-susceptible and -resistant types pre-treatment. Resistant isolates were detected during treatment, while antibiotic-susceptible isolates re-emerged at 3 weeks post-treatment. All Campylobacter isolates from Flock 4 were amoxicillin resistant, irrespective of sampling time. All but one of the 82 amoxicillin-resistant (MICs 16 to >128 mg/L) Campylobacter jejuni and Campylobacter coli tested for the presence of Cj0299 carried the gene and all of these produced beta-lactamase. Co-amoxiclav remained active against amoxicillin-resistant isolates. CONCLUSIONS: Amoxicillin therapy had little effect on the numbers of amoxicillin-resistant commensal Campylobacter except for one flock where amoxicillin-resistant Campylobacter temporarily dominated. Amoxicillin therapy did not select amoxicillin-resistant isolates from a previous susceptible strain. Co-amoxiclav remained active against amoxicillin-resistant isolates.

Prolonged treatment of Salmonella enterica serovar Typhimurium with commercial disinfectants selects for multiple antibiotic resistance, increased efflux and reduced invasiveness.

OBJECTIVES: To study how disinfectants affect antimicrobial susceptibility and phenotype of Salmonella enterica serovar Typhimurium SL1,344. METHODS: Wild-type strain SL1,344 and its isogenic gyrA mutant were passaged daily for 7 days in subinhibitory concentrations, and separately for 16 days in gradually increasing concentrations of a quaternary ammonium disinfectant containing formaldehyde and glutaraldehyde (QACFG), an oxidizing compound blend (OXC), a phenolic tar acids-based disinfectant (TOP) and triclosan. The MICs of antimicrobials and antibiotics for populations and representative isolates and the proportion of cells resistant to the MICs for the wild-type were determined. Expression of acrB gene, growth at 37 degrees C and invasiveness of populations in Caco-2 intestinal epithelial cells were assessed. RESULTS: QACFG and triclosan showed the highest selectivity for variants with reduced susceptibility to chloramphenicol, tetracycline, ampicillin, acriflavine and triclosan. Populations treated with the above biocides had reduced invasiveness in Caco-2 cells, and altered growth kinetics. Resistance to disinfectants was observed only after exposure to gradually increasing concentrations of triclosan, accompanied with a 2000-fold increase in its MIC. Growth in OXC and TOP did not affect the MICs of antibiotics, but resulted in the appearance of a proportion of cells resistant to the MIC of acriflavine and triclosan for the wild-type. Randomly selected stable variants from all populations, except the one treated with TOP, over-expressed acrB. CONCLUSIONS: In vitro exposure to QACFG and triclosan selects for Salmonella Typhimurium cells with reduced susceptibility to several antibiotics. This is associated with overexpression of AcrAB efflux pump, but accompanied with reduced invasiveness.

Prevalence and subtypes of ciprofloxacin-resistant Campylobacter spp. in commercial poultry flocks before, during, and after treatment with fluoroquinolones.

Five commercial broiler chicken flocks were treated with either difloxacin or enrofloxacin for a clinically relevant infection, as instructed by a veterinarian. Campylobacters were isolated from individual fecal samples and from samples associated with the broiler environment before, during, and after treatment. Ciprofloxacin-resistant Campylobacter jejuni and/or C. coli strains were detected pretreatment in four flocks, but they constituted a very small proportion of the campylobacters present. When the broilers were treated with a fluoroquinolone, a rapid increase in the proportion of ciprofloxacin-resistant campylobacters was observed. During treatment nearly 100% of campylobacters were resistant, and in some flocks a high proportion of resistant strains persisted for up to 4 weeks after treatment. Prior to treatment a variety of campylobacter subtypes were present. During and after treatment considerable changes in both species and subtype prevalence were observed, but no single fluoroquinolone-resistant clone became dominant. Instead, resistant C. coli strains or a mixture of resistant C. coli and C. jejuni strains became dominant, whereas susceptible C. jejuni strains had usually been dominant prior to treatment. The resistant subtypes which emerged and became dominant were not always the same as those detected pretreatment. The persistence of resistant strains for up to 4 weeks posttreatment has important implications for any strategy designed to avoid the introduction of such strains into the food chain.

Incidence and mechanism of ciprofloxacin resistance in Campylobacter spp. isolated from commercial poultry flocks in the United Kingdom before, during, and after fluoroquinolone treatment.

Five commercial broiler flocks were treated with a fluoroquinolone for a clinically relevant infection. Fresh feces from individual chickens and environmental samples were cultured for campylobacters before, during, and weekly posttreatment until slaughter. Both Campylobacter jejuni and C. coli were isolated during all treatment phases. An increased proportion of quinolone-resistant strains was seen during treatment, and these strains persisted posttreatment. One quinolone-resistant isolate of each species, each serotype, and each phage type from each sample at all treatment phases was examined for its phenotype and mechanism of resistance. Two resistant phenotypes were isolated: Nal(r) Cip(r) and Nal(r) Cip(s). The majority (269 of 290) of fluoroquinolone-resistant isolates, whether they were C. jejuni or C. coli, had a mutation in gyrA that resulted in the substitution Thr-86-->Ile. The other gyrA mutations detected were Thr-86-->Ala (n = 17) and Asp-90-->Asn (n = 10). The genotypic variation, based on the silent mutations in gyrA identified by the denaturing high-performance liquid chromatography pattern and DNA sequencing, was used to supplement typing data and provided evidence for both the spread of preexisting resistant strains and the selection of spontaneous resistant mutants in treated flocks. Multidrug resistance was significantly (P < 0.01) associated with resistance to ciprofloxacin. Twenty-five percent (73 of 290) of ciprofloxacin-resistant isolates but only 13% (24 of 179) of susceptible isolates were resistant to three or more unrelated antimicrobial agents. In conclusion, quinolone-resistant campylobacters were isolated from commercial chicken flocks in high numbers following therapy with a veterinary fluoroquinolone. Most ciprofloxacin-resistant isolates had the GyrA substitution Thr-86-->Ile. Resistant isolates were isolated from the feces of some flocks up to the point of slaughter, which may have consequences for public health.