Characteristics of quinolone and beta-lactam antibiotic resistance in Salmonella isolated from raw meat in Ho Chi Minh City

Abstract

In this study, a total of 380 raw meat samples (pork, beef, and chicken) were collected randomly from traditional markets in Ho Chi Minh City (Vietnam). Salmonella strains were isolated by cultivation methods according to ISO 6579-1:2017, and subsequently confirmed by PCR method (TCVN 8342:2010). These strains were used to test antibiotic susceptibility in six kinds of antibiotics belonging to two groups of quinolones (nalidixic, ciprofloxacin, and ofloxacin), and β-lactam antibiotics (ampicillin, amoxicillin, cephalexin) together with the detection of their resistant genotypes was estimated by Kirby-Bauer method and multiplex PCR. It was noted that the proportion of Salmonella spp. contaminated samples was 42.37% (161/380). Specifically, Salmonella spp. strains found in 50.00 % (63/126), 49.62% (65/131), and 26.83% (33/123) of pork, chicken, and beef samples, respectively. It was noticed that all isolated strains were resistant to six types of antibiotics. The highest proportion was 22.98% for ampicillin (AM), followed by 10.56% for nalidixic acid (NA). The proportions of amoxicillin/acid clavulanic (AMC), ceftazidime (CAZ), ciprofloxacin (CIP), and ofloxacin (OPX) resistant strains were remarkably low (< 10%). There were 37/161 (22.98%) Salmonella strains carrying TEM genes and 5/161 (3.11%) carrying CTX genes. On the other hand, there was no strain carrying SHV genes. Four quinolone-resistant genes including gyrA, gyrB involved in nalidixic acid resistance, and parC, parE involved in ofloxacin and ciprofloxacin resistance were detected in all Salmonella strains that also carried β-lactamase encoding genes. It is important to note that blaTEM-gyrA/B-parC/E genes were simultaneously found in all tested strains. While the proportion of strains containing blaCTX-gyrA/B-parC/E genes was 40.54%, the proportion of strains carrying blaTEM/CTX-gyrA/B-parC/E genes was 5.41%. The results revealed that raw meat might be contaminated with Salmonella spp. that are highly resistant to β-lactam antibiotics and quinolones. Henceforth, it is necessary to establish monitoring and surveillance programs on Salmonella spp. contamination and their antibiotic sensitivity in Vietnam to protect consumers’ health. The study also provided direct evidence for Salmonella contamination and antibiotic resistance situation in Ho Chi Minh City.