Dweba Chumisa C, Zishiri Oliver T, El Zowalaty Mohamed E
Discipline of Genetics, School of Life Sciences, College of Agriculture Engineering and Sciences, University of KwaZulu-Natal, Durban 4000, South Africa.
Infectious Diseases and Anti-Infective Therapy Research Group, Sharjah Medical Research Institute and College of Pharmacy, University of Sharjah, Sharjah 27272, UAE.
Pathogens. 2019 Jun 14;8(2):79. doi: 10.3390/pathogens8020079.
is one of the most important pathogens of humans and animals. Livestock production contributes a significant proportion to the South African Gross Domestic Product. Consequently, the aim of this study was to determine for the first time the prevalence, virulence, antibiotic and heavy metal resistance in livestock-associated isolated from South African livestock production systems. Microbial phenotypic methods were used to detect the presence of antibiotic and heavy metal resistance. Furthermore, molecular DNA based methods were used to genetically determine virulence as well as antibiotic and heavy metal resistance determinants. Polymerase chain reaction (PCR) confirmed 217 out of 403 (53.8%) isolates to be . Kirby-Bauer disc diffusion method was conducted to evaluate antibiotic resistance and 90.8% of isolates were found to be resistant to at least three antibiotics, and therefore, classified as multidrug resistant. Of the antibiotics tested, 98% of the isolates demonstrated resistance towards penicillin G. High resistance was shown against different heavy metals, with 90% (196/217), 88% (192/217), 86% (188/217) and 84% (183/217) of the isolates resistant to 1500 µg/mL concentration of Cadmium (Cd), Zinc (Zn), Lead (Pb) and Copper (Cu) respectively. A total of 10 antimicrobial resistance and virulence genetic determinants were screened for all livestock associated isolates. Methicillin-resistant (MRSA) isolates were identified, by the presence of , in 27% of the isolates with a significant relationship ( < 0.001)) with the host animal. This is the first report of positive LA-MRSA in South Africa and the African continent. The gene for tetracycline resistance ( was the most frequently detected of the screened genes with an overall prevalence of 35% and the highest prevalence percentage was observed for goats (56.76%) followed by avian species (chicken, duck and wild birds) (42.5%). Virulence-associated genes were observed across all animal host species. The study reports the presence of , a gene encoding the PVL toxin previously described to be a marker for community acquired-MRSA, suggesting the crossing of species between human and livestock. The high prevalence of from the livestock indicates a major food security and healthcare threat. This threat is further compounded by the virulence of the pathogen, which causes numerous clinical manifestations. The phenomenon of co-selection is observed in this study as isolates exhibited resistance to both antibiotics and heavy metals. Further, all the screened antibiotic and heavy metal resistance genes did not correspond with the phenotypic resistance.
是人和动物最重要的病原体之一。畜牧业生产在南非国内生产总值中占很大比例。因此，本研究的目的是首次确定从南非畜牧生产系统分离出的与家畜相关的[病原体名称未给出]的流行率、毒力、抗生素和重金属抗性。采用微生物表型方法检测抗生素和重金属抗性的存在。此外，基于分子DNA的方法用于从基因上确定毒力以及抗生素和重金属抗性决定因素。聚合酶链反应（PCR）证实403株分离物中有217株（53.8%）为[病原体名称未给出]。采用 Kirby - Bauer 纸片扩散法评估抗生素抗性，发现90.8%的[病原体名称未给出]分离物对至少三种抗生素耐药，因此被归类为多重耐药。在所测试的抗生素中，98%的分离物对青霉素G耐药。对不同重金属表现出高抗性，分别有90%（196/217）、88%（192/217）、86%（188/（217）和84%（183/217）的分离物对1500μg/mL浓度的镉（Cd）、锌（Zn）、铅（Pb）和铜（Cu）耐药。对所有与家畜相关的[病原体名称未给出]分离物共筛选了10种抗菌抗性和毒力基因决定因素。通过检测[基因名称未给出]的存在，在27%的分离物中鉴定出耐甲氧西林[病原体名称未给出]（MRSA），与宿主动物有显著关系（<0.001）。这是南非和非洲大陆首次关于阳性家畜相关MRSA的报告。四环素抗性基因（[基因名称未给出]）是筛选基因中最常检测到的，总体流行率为35%，山羊中的流行率最高（56.76%），其次是禽类（鸡、鸭和野生鸟类）（42.5%）。在所有动物宿主物种中均观察到毒力相关基因。该研究报告了[基因名称未给出]的存在，该基因编码先前被描述为社区获得性MRSA标志物的PVL毒素，表明人与家畜之间存在物种交叉。家畜中[病原体名称未给出]的高流行率表明对粮食安全和医疗保健构成重大威胁。病原体的毒力导致众多临床表现，进一步加剧了这一威胁。本研究中观察到共选择现象，因为分离物对抗生素和重金属均表现出抗性。此外，所有筛选的抗生素和重金属抗性基因与表型抗性均不对应。
