Heavy Metal Tolerance Trend in Extended-Spectrum β-Lactamase Encoding Strains Recovered from Food Samples

Abstract

This study evaluates bacteriological profiles in ready-to-eat (RTE) foods and assesses antibiotic resistance, extended-spectrum β-lactamase (ESBL) production by gram-negative bacteria, and heavy metal tolerance. In total, 436 retail food samples were collected and cultured. The isolates were screened for ESBL production and molecular detection of ESBL-encoding genes. Furthermore, all isolates were evaluated for heavy metal tolerance. From 352 culture-positive samples, 406 g-negative bacteria were identified. Raw food samples were more often contaminated than refined food (84.71% vs. 76.32%). The predominant isolates were Klebsiella pneumoniae (n = 76), Enterobacter cloacae (n = 58), and Escherichia coli (n = 56). Overall, the percentage of ESBL producers was higher in raw food samples, although higher occurrences of ESBL-producing E. coli (p = 0.01) and Pseudomonas aeruginosa (p = 0.02) were observed in processed food samples. However, the prevalence of ESBL-producing Citrobacter freundii in raw food samples was high (p = 0.03). Among the isolates, 55% were blaCTX-M, 26% were blaSHV, and 19% were blaTEM. Notably, heavy metal resistance was highly prevalent in ESBL producers. These findings demonstrate that retail food samples are exposed to contaminants including antibiotics and heavy metals, endangering consumers.

Multiple Antimicrobial Resistance and Heavy Metal Tolerance of Biofilm-Producing Bacteria Isolated from Dairy and Non-Dairy Food Products

“…These organisms carry plasmid-mediated resistance genes and cause community-acquired human infections. However, in this study, no significant difference in prevalence was observed between these bacterial isolates, consistent with the results of previous studies [ 21 , 51 ].…”

“…This study describes the presence of multiple AMR in foodborne bacterial isolates with biofilm formation potential, in combination with heavy metal tolerance. Previous studies have indicated that dairy products made from raw milk could be the main source of antibiotic-resistant bacteria that threaten food safety [ 21 , 36 ]. This problem is pervasive in developing countries because of poor food handling methods and hygiene standards, inadequate food safety rules and regulatory systems, and unsatisfactory education of food handlers [ 37 ].…”

“…Several studies have found that environmental heavy metal contamination also threatens food production [ 20 , 21 ]. Environmental bacteria can adapt to the presence of heavy metals by developing resistance to heavy metal ions, and the control of bacteria with the combination of antibiotic resistance and heavy metal tolerance is highly difficult [ 22 ].…”

Pseudomonas aeruginosa Detection Using Conventional PCR and Quantitative Real-Time PCR Based on Species-Specific Novel Gene Targets Identified by Pangenome Analysis

“…In addition to being frequently found in bottled mineral water and tap water, P. aeruginosa has also been tested positive in ready-to-eat vegetables ( Naze et al, 2010 ; Pelegrin et al, 2021 ; Ruiz-Roldán et al, 2021 ). Studies found the ready-to-eat vegetables that were a potential-although rare-vector for colistin- and carbapenem-resistant P. aeruginosa , the contamination rate of P. aeruginosa has reached 17.5% or 34% ( Cai et al, 2015 ; Hölzel et al, 2018 ; Kapeleka et al, 2020 ; Junaid et al, 2021 ). That is to say, P. aeruginosa is a major contaminant of fresh vegetables, which might be a source of infection for susceptible persons within the community ( Rahman et al, 2022 ).…”

“…This method will lead to wrong judgment in actual inspection: one case is that some strains of P. aeruginosa do not produce this pigment, which leads to missed inspection. Another situation is that P. fluorescens produces the same pigment as P. aeruginosa , which makes it impossible to distinguish and cause false positive ( Schroth et al, 2018 ; Junaid et al, 2021 ). For a long time, scientists have been committed to establishing a rapid and sensitive method for the detection of P. aeruginosa , but each method has its advantages and disadvantages ( Tang et al, 2017 ).…”