Characterization of Multidrug-Resistant Escherichia coli Isolated from Two Commercial Lettuce and Spinach Supply Chains

Genomic Evaluation of Multidrug-Resistant Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli from Irrigation Water and Fresh Produce in South Africa: A Cross-Sectional Analysis

Escherichia coli, both commensal and pathogenic, can colonize plants and persist in various environments. It indicates fecal contamination in water and food and serves as a marker of antimicrobial resistance. In this context, 61 extended-spectrum β-lactamase (ESBL)-producing E. coli from irrigation water and fresh produce from previous studies were characterized using whole genome sequencing (Illumina MiSeq). The Center for Genomic Epidemiology and Galaxy platforms were used to determine antimicrobial resistance genes, virulence genes, plasmid typing, mobile genetic elements, multilocus sequence typing (MLST), and pathogenicity prediction. In total, 19 known MLST groups were detected among the 61 isolates. Phylogroup B1 (ST58) and Phylogroup E (ST9583) were the most common sequence types. The six ST10 (serotype O101:H9) isolates carried the most resistance genes, spanning eight antibiotic classes. Overall, 95.1% of the isolates carried resistance genes from three or more classes. The blaCTX-M-1, blaCTX-M-14, and blaCTX-M-15 ESBL genes were associated with mobile genetic elements, and all of the E. coli isolates showed a >90% predicted probability of being a human pathogen. This study provided novel genomic information on environmental multidrug-resistant ESBL-producing E. coli from fresh produce and irrigation water, highlighting the environment as a reservoir for multidrug-resistant strains and emphasizing the need for ongoing pathogen surveillance within a One Health context.

Whole-Genome Sequencing of Human and Porcine Escherichia coli Isolates on a Commercial Pig Farm in South Africa

Escherichia coli is an indicator micro-organism in One Health antibiotic resistance surveillance programs. The purpose of the study was to describe and compare E. coli isolates obtained from pigs and human contacts from a commercial farm in South Africa using conventional methods and whole-genome sequencing (WGS). Porcine E. coli isolates were proportionally more resistant phenotypically and harbored a richer diversity of antibiotic resistance genes as compared to human E. coli isolates. Different pathovars, namely ExPEC (12.43%, 21/169), ETEC (4.14%, 7/169), EPEC (2.96%, 5/169), EAEC (2.96%, 5/169) and STEC (1.18%, 2/169), were detected at low frequencies. Sequence type complex (STc) 10 was the most prevalent (85.51%, 59/169) among human and porcine isolates. Six STcs (STc10, STc86, STc168, STc206, STc278 and STc469) were shared at the human-livestock interface according to multilocus sequence typing (MLST). Core-genome MLST and hierarchical clustering (HC) showed that human and porcine isolates were overall genetically diverse, but some clustering at HC2-HC200 was observed. In conclusion, even though the isolates shared a spatiotemporal relationship, there were still differences in the virulence potential, antibiotic resistance profiles and cgMLST and HC according to the source of isolation.

Microbiological quality of irrigation water on highly diverse fresh produce smallholder farms: elucidating environmental routes of contamination

AIM

To evaluate the microbiological safety, potential multidrug-resistant bacterial presence and genetic relatedness (DNA fingerprints) of Escherichia coli isolated from the water-soil-plant nexus on highly diverse fresh produce smallholder farms.

METHODS AND RESULTS

Irrigation water (n = 44), soil (n = 85), and fresh produce (n = 95) samples from six smallholder farms with different production systems were analysed for hygiene indicator bacterial counts and the presence of shigatoxigenic E. coli and Salmonella spp. using standard microbiological methods. Identities of isolates were confirmed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and the genetic relatedness of the E. coli isolates determined using enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) analysis. Irrigation water E. coli levels ranged between 0 and 3.45 log MPN/100 ml-1 with five farms having acceptable levels according to the World Health Organization limit (3 log MPN/100 ml-1). Fresh produce samples on four farms (n = 65) harboured E. coli at low levels (<1 log CFU/g-1) except for one sample from kale, spring onion, green pepper, onion, and two tomato samples, which exceeded international acceptable limits (100 CFU/g-1). Only one baby carrot fresh produce sample tested positive for Salmonella spp. Of the 224 samples, E. coli isolates were identified in 40% (n = 90) of all water, soil, and fresh produce types after enrichment. Additionally, the DNA fingerprints of E. coli isolates from the water-soil-plant nexus of each respective farm clustered together at high similarity values (>90%), with all phenotypically characterized as multidrug-resistant.

CONCLUSIONS

The clustering of E. coli isolated throughout the water-soil-plant nexus, implicated irrigation water in fresh produce contamination. Highlighting the importance of complying with irrigation water microbiological quality guidelines to limit the spread of potential foodborne pathogens throughout the fresh produce supply chain.

Draft genome sequence of multidrug-resistant Citrobacter freundii MTR_GS_V1777 strain isolated from a spinach (Spinacia oleracea) sample in Gazipur, Bangladesh

We announce a genome sequence of Citrobacter freundii MTR_GS_V1777 strain isolated from a vegetable sample in Bangladesh. This strain had a genome size of 4,997,753 bp (58.7× genome coverage) and contained two plasmids, typed as sequence type ST124, 38 predicted antibiotic resistance genes, and 77 predicted virulence factor genes.

Draft genome sequences of five multidrug-resistant Escherichia coli strains isolated from vegetable samples in Bangladesh

Reports indicate that vegetables are becoming a source of multidrug-resistant (MDR) bacteria, including Escherichia coli. Here, we present genome sequences of five MDR E. coli strains to assist future genomic analysis of this bacterium. These E. coli strains were isolated from vegetable samples of different gardening systems in Dhaka, Bangladesh.

Serotype Distribution, Antimicrobial Resistance, Virulence Genes, and Genetic Diversity of Salmonella spp. Isolated from small-scale Leafy Green Vegetable Supply Chains in South Africa

Salmonella have been implicated in foodborne disease outbreaks globally and is a pressing concern in the South African small-scale sector due to inadequate hygiene standards and limited regulatory oversight, leading to a higher risk of foodborne diseases. By investigating irrigation water and leafy green vegetables produced by small-scale growers and sold through unregulated supply chains, this study was able to determine the presence, serotype distribution, virulence gene profiles, antibiotic resistance, and genetic diversity of Salmonella isolated from these sources. From 426 samples, 21 Salmonella-positive samples were identified, providing 53 Salmonella isolates. Of these, six different Salmonella serotypes and sequence types (STs) were identified, including Salmonella II 42:r: ST1208 (33.96%; n = 18), Salmonella Enteritidis: ST11 (22.64%; n = 12), Salmonella II 42:z29: ST4395 (16.98%; n = 9), Salmonella Havana: ST1524 (15.09%; n = 8), Salmonella Typhimurium: ST19 (9.43%; n = 5), and Salmonella IIIb 47:i:z: ST7890 (1.89%; n = 1). A total of 92.45% of the isolates were found to be multidrug-resistant, showing high rates of resistance to aztreonam (88.68%; n = 47), ceftazidime (86.79%; n = 46), nalidixic acid (77.36%; n = 41), cefotaxime (75.47%; n = 40), cefepime (71.70%; n = 38), and streptomycin (69.81%; n = 37). All isolates possessed the aac(6')-Iaa antimicrobial resistance gene, with a range of between 9 and 256 virulence genes. Eleven cluster patterns were observed from Enterobacterial Repetitive Intergenic Consensus sequence analyses, demonstrating high diversity among the Salmonella spp., with water and fresh produce isolates clustering, suggesting water as a potential contamination source. Plasmid replicon types were identified in 41.51% (n = 22) of the isolates, including Col(pHAD28) in Salmonella Havana (5.66%; n = 3), Col156 in Salmonella II 42:z29:- (1.89%; n = 1) and both IncFIB(S) and IncFII(S) in Salmonella Enteritidis (22.64; n = 12), Salmonella Typhimurium (9.43%; n = 5), and Salmonella Havana (1.89%; n = 1). This study highlights the presence of multidrug-resistant and multivirulent Salmonella spp. in the small-scale leafy green vegetable supply chains, underscoring the need for the development of a "fit-for-purpose" food safety management system within this system.

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.

Multidrug-resistant extended spectrum β-lactamase (ESBL)-producing Escherichia coli from farm produce and agricultural environments in Edo State, Nigeria

Antimicrobial resistance (AMR) is a major public health concern, especially the extended-spectrum β-lactamase-producing (ESBL) Escherichia coli bacteria are emerging as a global human health hazard. This study characterized extended-spectrum β-lactamase Escherichia coli (ESBL-E. coli) isolates from farm sources and open markets in Edo State, Nigeria. A total of 254 samples were obtained in Edo State and included representatives from agricultural farms (soil, manure, irrigation water) and vegetables from open markets, which included ready-to-eat (RTE) salads and vegetables which could potentially be consumed uncooked. Samples were culturally tested for the ESBL phenotype using ESBL selective media, and isolates were further identified and characterized via polymerase chain reaction (PCR) for β-lactamase and other antibiotic resistance determinants. ESBL E. coli strains isolated from agricultural farms included 68% (17/25) from the soil, 84% (21/25) from manure and 28% (7/25) from irrigation water and 24.4% (19/78) from vegetables. ESBL E. coli were also isolated from RTE salads at 20% (12/60) and vegetables obtained from vendors and open markets at 36.6% (15/41). A total of 64 E. coli isolates were identified using PCR. Upon further characterization, 85.9% (55/64) of the isolates were resistant to ≥ 3 and ≤ 7 antimicrobial classes, which allows for characterizing these as being multidrug-resistant. The MDR isolates from this study harboured ≥1 and ≤5 AMR determinants. The MDR isolates also harboured ≥1 and ≤3 beta-lactamase genes. Findings from this study showed that fresh vegetables and salads could be contaminated with ESBL-E. coli, particularly fresh produce from farms that use untreated water for irrigation. Appropriate measures, including improving irrigation water quality and agricultural practices, need to be implemented, and global regulatory guiding principles are crucial to ensure public health and consumer safety.

Phylogenetic Groups and Antimicrobial Resistance Genes in Escherichia coli from Different Meat Species

Escherichia coli isolated from meat of different animal species may harbour antimicrobial resistance genes and may thus be a threat to human health. The objectives of this study were to define antimicrobial resistance genes in E. coli isolates from pork, beef, chicken- and turkey meat and analyse whether their resistance genotypes associated with phylogenetic groups or meat species. A total number of 313 E. coli samples were isolated using standard cultural techniques. In 98% of resistant isolates, a dedicated resistance gene could be identified by PCR. Resistance genes detected were tet(A) and tet(B) for tetracycline resistance, strA and aadA1 for streptomycin resistance, sulI and sulII for resistance against sulphonamides, dfr and aphA for kanamycin resistance and bla_TEM for ampicillin resistance. One stx1 harbouring E. coli isolated from pork harboured the tet(A) gene and belonged to phylogenetic group B2, whilst another stx1 positive isolate from beef was multi-resistant and tested positive for bla_TEM,aphA, strA–B, sulII, and tet(A) and belonged to phylogenetic group A. In conclusion, the distribution of resistance elements was almost identical and statistically indifferent in isolates of different meat species. Phylogenetic groups did not associate with the distribution of resistance genes and a rather low number of diverse resistance genes were detected. Most E. coli populations with different resistance genes against one drug often revealed statistically significant different MIC values.