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Abstract：
The increasing emergence of Staphylococcus aureus as the primary causative agent of otitis externa has been noted; however, detailed information regarding the molecular characteristics of these strains in Iran remains scarce. The current study aims to investigate both genotypic and phenotypic attributes of S. aureus strains implicated in ear infections. In the present work, we analyzed 60 S. aureus strains isolated from cases of otitis externa over a period of 45 months. The resistance patterns were determined using disk diffusion and microbroth dilution methods. All S. aureus isolates were confirmed by the nucA polymerase chain reaction assay, and their biofilm production was assessed by a microtiter plate assay. Molecular characterization of the isolates was performed using the staphylococcal cassette chromosome mec, multilocus sequence typing, and staphylococcus protein A typing methods. Overall, the results indicated that 44 out of 60 S. aureus isolates (73.3 %) were methicillin-resistant Staphylococcus aureus. Resistance to mupirocin and vancomycin was observed in 13.3 % and 1.7 % of the tested isolates, respectively. Furthermore, out of the 60 S. aureus isolates, 56 strains (93.4 %) were classified as positive biofilm strains at different levels. Twelve distinct clonal lineages were identified. The vast majority of S. aureus isolates belonged to CC30/ST30-MRSA IV/t019 (41.7 %). Among the 31 strong biofilm producers, the majority (64.5 %) belonged to CC30/ST30-MRSA IV/t019 clone. Biofilm negative isolates belonged to CC22/ST22 (2 isolates), CC8/ST585 (one isolate), and CC8/ST8 (one isolate). Our result revealed that about three-quarters of PVL-positive strains belonged to CC30/ST30. Our data confirmed the presence of MSSA strains among CC30/ST30 and CC22/ST22 isolates. The mupirocin resistant isolates (n = 8) belonged to CC8/ST585-MRSA III/t713 (37.5 %), CC8/ST239-MRSA III/t030 (25 %), CC8/ST8-MRSA IV/t008 (12.5 %), CC8/ST239-MRSA III/t037 (12.5 %), and CC22/ST22-MRSA IV/t790 (12.5 %) lineages. The VRSA strain belonged to the CC8/ST8-MRSA IV/t008 lineage, carrying the vanA determinant. iMLSB phenotypes (n = 14) were distributed across different lineages, including CC30/ST30-MRSA IV/t019 (21.5 %), CC30/ST30-MSSA/t021 (21.5 %), CC22/ST22-MSSA/t005 (14.3 %), CC8/ST239-MRSA III/t030 (14.3 %), CC22/ST22-MSSA/t1869 (7.1 %), CC22/ST22-MRSA IV/t790 (7.1 %), CC8/ST239-MRSA III/t037 (7.1 %), and CC1/ST772-MRSA IV/t10795 (7.1 %). These findings highlight significant genotypic diversity and high biofilm formation among our isolates. The frequent occurrence of the CC/ST30 clone in S. aureus strains isolated from otitis externa reflects the emergence of these lineages as a predominant clone in Iran, posing a significant public health concern.
摘要：
已注意到金黄色葡萄球菌作为外耳炎的主要病原体的出现；然而，有关这些菌株在伊朗的分子特征的详细信息仍然很少。本研究旨在调查与耳部感染有关的金黄色葡萄球菌菌株的基因型和表型属性。在目前的工作中,我们分析了在45个月内从外耳炎病例中分离出的60株金黄色葡萄球菌.使用圆盘扩散和微量肉汤稀释方法确定电阻模式。所有金黄色葡萄球菌分离物均通过nucA聚合酶链反应测定证实，并通过微量滴定板测定法评估其生物膜的产生。使用葡萄球菌盒染色体mec对分离物进行分子表征，多位点序列分型,和葡萄球菌蛋白A分型方法。总的来说,结果表明,60株金黄色葡萄球菌中44株(73.3%)是耐甲氧西林金黄色葡萄球菌.在13.3％和1.7％的测试分离物中观察到对莫匹罗星和万古霉素的耐药性，分别。此外，在60个金黄色葡萄球菌分离物中，56株(93.4%)被分类为不同水平的阳性生物膜菌株。鉴定了12个不同的克隆谱系。绝大多数金黄色葡萄球菌属于CC30/ST30-MRSAIV/t019(41.7%)。在31个强大的生物膜生产商中，大部分(64.5%)属于CC30/ST30-MRSAIV/t019克隆。生物膜阴性分离株属于CC22/ST22（2株），CC8/ST585（一个隔离），和CC8/ST8（一个分离）。我们的结果表明，约四分之三的PVL阳性菌株属于CC30/ST30。我们的数据证实了CC30/ST30和CC22/ST22分离株中存在MSSA菌株。莫匹罗星耐药分离株(n=8)属于CC8/ST585-MRSAIII/t713(37.5%),CC8/ST239-MRSAIII/t030（25%），CC8/ST8-MRSAIV/t008（12.5%），CC8/ST239-MRSAIII/t037（12.5%），和CC22/ST22-MRSAIV/t790（12.5％）谱系。VRSA菌株属于CC8/ST8-MRSAIV/t008谱系,携带VNA决定因素。iMLSB表型(n=14)分布在不同的谱系，包括CC30/ST30-MRSAIV/t019（21.5%），CC30/ST30-MSSA/t021(21.5%),CC22/ST22-MSSA/t005(14.3%),CC8/ST239-MRSAIII/t030（14.3%），CC22/ST22-MSSA/t1869（7.1%），CC22/ST22-MRSAIV/t790（7.1%），CC8/ST239-MRSAIII/t037（7.1%），和CC1/ST772-MRSAIV/t10795（7.1%）。这些发现突出了我们的分离株中显著的基因型多样性和高生物膜形成。从外耳炎分离的金黄色葡萄球菌菌株中CC/ST30克隆的频繁出现反映了这些谱系在伊朗作为主要克隆的出现。构成重大公共卫生问题。
