Awad Amal, Ramadan Hazem, Nasr Sherif, Ateya Ahmed, Atwa Samar
Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine, Mansoura University, 35516 Mansoura, Egyp.
Department of Hygiene and Zoonoses, Faculty of Veterinary Medicine, Mansoura University, 35516 Mansoura, Egypt.
Pak J Biol Sci. 2017;20(6):298-305. doi: 10.3923/pjbs.2017.298.305.
Staphylococcus aureus is commonly associated with mastitis in dairy herds with potential public health implications. This study was conducted to investigate the existence of S. aureus in mastitic milk and to determine the antimicrobial resistance profiles of the isolated strains as well as the resistance and virulence associated genes.
Two hundred quarter milk samples were collected from 3 dairy farms at Dakahliya (n = 2) and Damietta (n = 1) Governorates, Egypt from September to December 2016. Conventional culturing and Polymerase Chain Reaction (PCR) assays targeting nuc (thermonuclease) and coa (coagulase) genes were performed. Isolates were tested for its susceptibility against 14 antimicrobial agents using disk diffusion method. All the isolates were screened for the presence of β-lactamases (blaZ, mecA) and virulence associated (pvl and tst) genes by PCR.
The S. aureus was detected in 42% (84/200) of the total examined milk samples. Regarding the antibiogram results, S. aureus revealed a high resistance against ampicillin (95.2%) and penicillin (83.3%) and a lower resistance was observed against gentamicin (23.8%), amikacin (16.7%) and ciprofloxacin (14.3%). Multidrug resistances were detected in 83.3% of the isolated S. aureus. Of the 70 penicillin-resistant S. aureus isolates, blaZ gene was identified in 67 (95.7%) isolates. Fifty percent of S. aureus isolates harbored the specific amplicon of mecA gene. Markedly, all mecA positive strains displayed multidrug resistance and were also positive for blaZ gene. The virulence determinants pvl and tst were detected in 7.1 and 11.9% of the isolated S. aureus, respectively.
Presence of multidrug resistant and toxin producing S. aureus in dairy farms pose a major risk to public health. Therefore, this study highlighted the importance of developing an efficient control program to inhibit the transmission of S. aureus, particularly multidrug resistant strains to humans.
金黄色葡萄球菌通常与奶牛场的乳腺炎有关，对公共卫生有潜在影响。本研究旨在调查患乳腺炎牛奶中金黄色葡萄球菌的存在情况，确定分离菌株的抗菌药物耐药谱以及耐药和毒力相关基因。
2016年9月至12月，从埃及达卡利亚省（2个农场）和达米埃塔省（1个农场）的3个奶牛场采集了200份乳区牛奶样本。进行了针对nuc（耐热核酸酶）和coa（凝固酶）基因的常规培养及聚合酶链反应（PCR）检测。采用纸片扩散法检测分离株对14种抗菌药物的敏感性。通过PCR对所有分离株进行β-内酰胺酶（blaZ、mecA）和毒力相关（pvl和tst）基因的筛查。
在所检测的全部牛奶样本中，42%（84/200）检测到金黄色葡萄球菌。关于抗菌谱结果，金黄色葡萄球菌对氨苄西林（95.2%）和青霉素（83.3%）耐药性高，对庆大霉素（23.8%）、阿米卡星（16.7%）和环丙沙星（14.3%）耐药性较低。83.3%的分离金黄色葡萄球菌检测到多重耐药。在70株耐青霉素金黄色葡萄球菌分离株中，67株（95.7%）鉴定出blaZ基因。50%的金黄色葡萄球菌分离株携带mecA基因的特异性扩增子。值得注意的是，所有mecA阳性菌株均表现出多重耐药，且blaZ基因也呈阳性。毒力决定因素pvl和tst分别在7.1%和11.9%的分离金黄色葡萄球菌中检测到。
奶牛场中存在多重耐药和产毒素的金黄色葡萄球菌对公共卫生构成重大风险。因此，本研究强调了制定有效控制计划以抑制金黄色葡萄球菌，特别是多重耐药菌株向人类传播的重要性。
