Molecular Detection Of Multidrug-Resistant Salmonella Isolated From Livestock Production Systems In South Africa

Thobeka P Mthembu; Oliver T Zishiri; Mohamed E El Zowalaty

doi:10.2147/IDR.S211618

Molecular Detection Of Multidrug-Resistant Salmonella Isolated From Livestock Production Systems In South Africa

Infect Drug Resist. 2019 Nov 14:12:3537-3548. doi: 10.2147/IDR.S211618. eCollection 2019.

Authors

Thobeka P Mthembu¹, Oliver T Zishiri¹, Mohamed E El Zowalaty^{2

3}

Affiliations

¹ School of Life Sciences, University of KwaZulu-Natal, Durban, 4000, South Africa.
² Virology and Microbiology Research Group, School of Health Sciences, University of KwaZulu-Natal, Durban, 4000, South Africa.
³ Infectious Diseases and Anti-Infective Research Group, College of Pharmacy, University of Sharjah, Sharjah, 27272, UAE.

Abstract

Background: Antibiotic-resistant bacterial pathogens associated with livestock remain a major concern worldwide as they get transmitted from animals to humans and cause foodborne and zoonotic diseases.

Methods: Antimicrobial resistance in livestock-associated Salmonella spp in South Africa was investigated using molecular DNA methods. Three hundred and sixty-one environmental faecal samples were randomly collected from avian (chicken and ducks), cows, pigs, goats, and sheep. Salmonella spp. were isolated on selective media and were confirmed using the polymerase chain reaction. Antimicrobial susceptibility testing against ampicillin, chloramphenicol, ciprofloxacin, ceftriaxone, azithromycin, tetracycline, amoxicillin-clavulanate and trimethoprim-sulfamethoxazole was determined using the Kirby-Bauer disk diffusion method. Isolates were screened for the presence of bla_TEM-1, bla_CMY-2, tetA, tetC, sul2 and dfrA7 resistance genes by PCR.

Results: Most of the isolates were resistant to ampicillin (64%), tetracycline (63%), amoxicillin-clavulanate (49%), trimethoprim-sulfamethoxazole (38%), and ceftriaxone (20%). Eight percent of the tested isolates were ciprofloxacin-resistant Salmonella spp. Multidrug resistance was observed with the mean multiple antibiotic resistance (MAR) index of 0.31. The study demonstrated that 43% of the isolates were multiple drug resistant. The prevalence rates of resistance genes were 44% for bla_TEM-1 , 35% for bla_CMY-2 , 21% for sul2, 18% for tetC, 14% for dfrA7 and 8% for tetA.

Conclusion: Resistance to ceftriaxone, detection of bla_CMY-2 gene and the high level of intermediate susceptibility (33%) against ciprofloxacin suggested that livestock carry problematic Salmonella spp. This study used the global one-health initiative to report the potential public health risks of livestock-associated pathogens and highlights the importance of monitoring the trends of antimicrobial resistance for sustainability of antibiotics.

Keywords: Salmonella; animals; antimicrobial; bacteria; blaCMY-2; blaTEM-1; ciprofloxacin; food-borne pathogens; resistance; zoonotic.