AmpC- and Extended-Spectrum β-Lactamase-Producing Enterobacteriaceae Detected in Fresh Produce in Central Ohio

A Multidrug-Resistant Extended-Spectrum Beta-Lactamase (ESBL)-Producing Enterobacter hormaechei Strain from Mixed Sprouts

Fresh vegetables can harbor antibiotic-resistant bacteria, including extended-spectrum β-lactamase (ESBL)-producing Enterobacterales. Enterobacter hormaechei is a bacterium belonging to the Enterobacterales order and the most commonly identified nosocomial pathogen of Enterobacter cloacae complex. The purpose of this study was to characterize a multi-drug resistant ESBL-producing E. hormaechei strain isolated from a sample of mixed sprouts. Vegetable samples were pre-enriched in buffered peptone water, followed by enrichment in Enterobacteria Enrichment Broth, and isolation on Chromagar™ ESBL plates. One isolate from a sprout sample was confirmed to produce both ESBL and AmpC β-lactamases through the combination disk diffusion assay using antibiotic disks containing cefotaxime and ceftazidime with or without clavulanate, and with or without cloxacillin, respectively. The isolate was also resistant to multiple antibiotics, including cefotaxime, ceftazidime, chloramphenicol, trimethoprim-sulfamethoxazole, tetracycline, gentamicin, ampicillin, and amoxicillin-clavulanate, as determined by antimicrobial susceptibility testing. Through whole genome sequencing, the isolate was identified as E. hormaechei 057-E1, which carried multiple antibiotic resistance (AR) genes and a sul2-aph(3″)-Ib-aph(6)-Id-blaTEM-1-ISEcp1 -blaCTX-M-15 gene cluster. Our results further demonstrate the important role of fresh vegetables in AR and highlight the need to develop strategies for AR mitigation in fresh vegetables.

Prevalence of Campylobacter spp., Salmonella spp., and Listeria monocytogenes, and Population Levels of Food Safety Indicator Microorganisms in Retail Raw Chicken Meat and Ready-To-Eat Fresh Leafy Greens Salads Sold in Greece

The presence of microbial pathogens in foods compromises their safety resulting in foodborne illnesses, public health disorders, product recalls, and economic losses. In this work, 60 samples of chilled raw chicken meat and 40 samples of packaged ready-to-eat (RTE) fresh leafy greens salads, sold in Greek retail stores (butchers and supermarkets), were analyzed for the presence of three important foodborne pathogenic bacteria, i.e., Campylobacter spp., Salmonella spp., and Listeria monocytogenes, following the detection protocols of the International Organization for Standardization (ISO). In parallel, the total aerobic plate count (APC), Enterobacteriaceae, total coliforms, Escherichia coli, and staphylococci were also enumerated as hygiene (safety) indicator organisms. When present, representative typical colonies for each pathogen were biochemically verified, following the ISO guidelines. At the same time, all the Campylobacter isolates from chicken (n = 120) were identified to the species level and further phylogenetically discriminated through multiplex and repetitive sequence-based (rep) polymerase chain reaction (PCR) methods, respectively. Concerning raw chicken, Campylobacter spp. were recovered from 54 samples (90.0%) and Salmonella spp. were recovered from 9 samples (15.0%), while L. monocytogenes was present in 35 samples (58.3%). No Campylobacter was recovered from salads, and Salmonella was present in only one sample (2.5%), while three salads were found to be contaminated with L. monocytogenes (7.5%). The 65% of the Campylobacter chicken isolates belonged to C. jejuni, whereas the rest, 35%, belonged to C. coli. Alarmingly, APC was equal to or above 106 CFU/g in 53.3% and 95.0% of chicken and salad samples, respectively, while the populations of some of the other safety indicators were in some cases also high. In sum, this study unravels high occurrence percentages for some pathogenic and food safety indicator microorganisms in raw chicken meat and RTE fresh leafy greens salads sold in Greek retail, highlighting the need for more extensive microbiological control throughout the food production chain (from the farm/field to the market).

Resistance to β-lactams in Enterobacteriaceae isolated from vegetables: a review

Vegetables are crucial for a healthy human diet due to their abundance of essential macronutrients and micronutrients. However, there have been increased reports of antimicrobial-resistant Enterobacteriaceae isolated from vegetables. Enterobacteriaceae is a large group of Gram-negative bacteria that can act as commensals, intestinal pathogens, or opportunistic extraintestinal pathogens. Extraintestinal infections caused by Enterobacteriaceae are a clinical concern due to antimicrobial resistance (AMR). β-lactams have high efficacy against Gram-negative bacteria and low toxicity for eukaryotic cells. These antimicrobials are widely used in the treatment of Enterobacteriaceae extraintestinal infections. This review aimed to conduct a literature survey of the last five years (2018-2023) on the occurrence of β-lactam-resistant Enterobacteriaceae in vegetables. Research was carried out in PubMed, Web of Science, Scopus, ScienceDirect, and LILACS (Latin American and Caribbean Health Sciences Literature) databases. After a careful evaluation, thirty-seven articles were selected. β-lactam-resistant Enterobacteriaceae, including extended-spectrum β-lactamases (ESBLs)-producing, AmpC β-lactamases, and carbapenemases, have been isolated from a wide variety of vegetables. Vegetables are vectors of β-lactam-resistant Enterobacteriaceae, contributing to the dissemination of resistance mechanisms previously observed only in the hospital environment.

Vegetables and Fruit as a Reservoir of β-Lactam and Colistin-Resistant Gram-Negative Bacteria: A Review

Antibacterial resistance is one of the 2019 World Health Organization’s top ten threats to public health worldwide. Hence, the emergence of β-lactam and colistin resistance among Gram-negative bacteria has become a serious concern. The reservoirs for such bacteria are increasing not only in hospital settings but in several other sources, including vegetables and fruit. In recent years, fresh produce gained important attention due to its consumption in healthy diets combined with a low energy density. However, since fresh produce is often consumed raw, it may also be a source of foodborne disease and a reservoir for antibiotic resistant Gram-negative bacteria including those producing extended-spectrum β-lactamase, cephalosporinase and carbapenemase enzymes, as well as those harboring the plasmid-mediated colistin resistance (mcr) gene. This review aims to provide an overview of the currently available scientific literature on the presence of extended-spectrum β-lactamases, cephalosporinase, carbapenemase and mcr genes in Gram-negative bacteria in vegetables and fruit with a focus on the possible contamination pathways in fresh produce.