Isolation and molecular characterization of staphylococcus aureus isolated from clinical cases in broilers

Abstract

Background: Staphylococcus aureus(S. aureus)causes a difficult problem in the poultry industry because it causes diseases thatare difficult to treatdue to the resistance of these bacteria to antibiotics and their possession of a battery of virulence and resistance genes in addition to their ability to producethick biofilms.Method: A cross-sectional studyconducted to collecta total of 53samples from different clinical cases in broilers during the period from August 2019 to February 2020in Al-Najaf and Karbala cities,The clinical isolates were determined by using the conventional standard biochemical tests. All the specimens cultured on blood agar medium supplemented with 5% blood for primary isolation and selected by using selective mediamannitol salt agar(MSA) for confirmation the mannitol fermentation, then subjected to gram’s staining, catalase, oxidase,and further slidecoagulase test, then allS. aureusisolatestested by antibiotic susceptibility test, and screened for the presence of mecA and mecC genes using PCR for the detection of MRSA isolates, then subjected to the detection of virulence genes (pvl and eta), antibiotic resistance gene (cfr), identification of integron class 1, biofilm formation assay, themulti-druge resistance profiles(MDR)and multible antibiotics resistance (MAR)indexes werecalculated.Results: the isolation rate of S. aureusfrom the broilers'clinical samples was 37.7%. The antibiotic susceptibility test revealed that 85%of S. aureusisolateswere resistant to one or moreofthe antibiotic tested. All 53isolates were assessed for the presence of mecA and mecC genes byusingPCR. The mecA gene-specific PCRproductwas seen in 7 (35%)isolates and considered as MRSA. Among all S. aureus isolates,two isolates were positive for the eta gene, and 15 (75%) isolates harboring integron class 1, while the biofilm formation test revealed that 7 (35%) was positive biofilm producers and three of them werestrong producers,consequentlly, 13 (65%) of the isolates wereresisted to three or more antibiotics and considered as MDR strains.While pvl, cfr, and mecC gene werenot detected among S. aureus isolates.Conclusion:the current study revealed thatS. aureuspossessa real threat in the poultry industry reflectingapublic healthproblemdue to the large acquisition of antibiotic resistance genes by these bacteria,the results indicated a high percentage of isolates havingMDR characteristic, and two of them were resistant to all antibiotics tested.In addition to the presence of two MRSA isolates carrying the eta gene, this indicatingthat they are of human origin.