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

• Main Authors: Kashaf Junaid, Hasan Ejaz, Iram Asim, Sonia Younas, Humaira Yasmeen, Abualgasim Elgaili Abdalla, Khalid Omer Abdalla Abosalif, Ayman Ali Mohammed Alameen, Naveed Ahmad, Syed Nasir Abbas Bukhari, Abdul Rehman
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: processed food; food contaminants; heavy metals; beta-lactamase; ESBL
• Online Access: https://www.mdpi.com/1660-4601/18/9/4718
• ISSN: 1661-7827; 1660-4601

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 <i>Klebsiella pneumoniae</i> (<i>n</i> = 76), <i>Enterobacter cloacae</i> (<i>n</i> = 58), and <i>Escherichia coli</i> (<i>n</i> = 56). Overall, the percentage of ESBL producers was higher in raw food samples, although higher occurrences of ESBL-producing <i>E. coli</i> (<i>p</i> = 0.01) and <i>Pseudomonas aeruginosa</i> (<i>p</i> = 0.02) were observed in processed food samples. However, the prevalence of ESBL-producing <i>Citrobacter freundii</i> in raw food samples was high (<i>p</i> = 0.03). Among the isolates, 55% were <i>bla</i>_CTX_-M, 26% were <i>bla</i>_SHV, and 19% were <i>bla</i>_TEM. 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.