Detection of extended spectrum beta-lactamase (ESBL)–production in Salmonella Typhimurium isolated from poultry birds in Nasarawa State, Nigeria

Abstract

Salmonella Typhimurium is an important zoonotic food borne pathogen and the second most widely studied pathogen in relation to antimicrobial resistance studies in Nigeria. Its resistance to β-lactam antibiotics is on the rise globally due to persistent exposure and production of Extended Spectrum Beta-lactamase enzymes (ESBLs) which is barely reported to occur among food producing animals in Nigeria. This poses a threat to the successful therapy of salmonellosis infections and raises concern on food safety. Further complicating these challenges is the lack of strict laws mitigating antibiotic usage in Nigeria. The study was conducted in the Microbiology laboratory of Nasarawa State University, Keffi, Nigeria. A total of 300 samples each of poultry droppings, flesh, feeds, human hand swabs and stool were randomly collected following ethical approval and screened for ESBL- producing S. Typhimurium using standard Microbiological methods of isolation and identification. Antibiotic susceptibility testing, phenotypic ESBL detection and interpretation were carried out as described by the Clinical Laboratory and Standard Institute (CLSI) guideline. The bla genes were identified using polymerase chain reaction (PCR) method. A total of 106 S.Typhimurium were isolated with the following resistance profile; Ampicillin 99(93.4%), Augmentin 104(98.1%), Ceftriaxone 74(69.8%), Ceftazidime 50(47.2%), Imipenem 1(1.0%). The antibiotic resistance of S. Typhimurium in the study is significant (P = 0.01). The Multiple Antibiotic Resistance (MAR) Index was > 0.2. Out of 106 isolates, 32 distinct antimicrobial resistant phenotypes were observed and 62 (81.6%) were confirmed ESBL producers having 19 distinct phenotypes. The bla genes were identified among 38.7% (24/62) isolates; 100% blaSHV (24/24), 87.5 %(21/24)blaTEM with 54.2% (13/24) co-carriage of blaTEM-SHV. The blaCTX-M was not detected. Poultry is therefore an important reservoir and source of transmission of ESBL- producing S.Typhimurium, which is a major public health concern. The high MAR index suggests frequent antibiotic usage within our study area, thus calls for antibiotic stewardship in animal production in Nigeria.