Characterization of biofilm formation, antimicrobial resistance, and staphylococcal cassette chromosome mec analysis of methicillin resistant Staphylococcus hominis from blood cultures of children

Abstract INTRODUCTION: Methicillin resistant Staphylococcus hominis (MRSHo) has been recognized as an important human pathogen, particularly in immunocompromised patients. METHODS: A total of 19 S. hominis isolates were collected from children at the Children’s Medical Centre, Tehran, Iran, from March 2012 to February 2013. MRSHo susceptibility against 13 antimicrobial and 3 antiseptic agents was determined using disk diffusion (DAD) and minimum inhibitory concentration (MIC), respectively. All isolates were subjected to polymerase chain reaction (PCR) assay for 15 distinct resistance genes, staphylococcal cassette chromosome mec (SCCmec), and arginine catabolic mobile elements (ACMEs). Biofilm production of the isolates was determined using a colorimetric microtiter plate assay. RESULTS: Of the 19 isolates, 16 were resistant to oxacillin and harbored mecA. High resistance was also observed against trimethoprim/sulfamethoxazole (81.2%). All MRSHo isolates were susceptible to the three disinfectants tested (Septicidine-PC, Septi turbo, and Sayacept-HP). In total, 15 (78.9%) isolates produced biofilms. Three isolates had SCCmec types (V and VIII), 13 were untypable (UT), and 5 had ACME type II. CONCLUSIONS: The results indicate that MRSHo with high antibiotic resistance and unknown SCCmec might become a serious problem in the future for the treatment of patients such as children.

摘要：
引言：耐甲氧西林人葡萄球菌（Methicillin resistant Staphylococcus hominis, MRSHo）是一类重要的人类致病菌，尤其对免疫功能低下患者威胁显著。
方法：2012年3月至2013年2月，从伊朗德黑兰儿童医学中心的患儿体内分离得到19株人葡萄球菌菌株。分别采用纸片扩散法（disk diffusion, DAD）和最低抑菌浓度（minimum inhibitory concentration, MIC）试验，检测MRSHo对13种抗菌药物及3种消毒剂的敏感性。采用聚合酶链式反应（polymerase chain reaction, PCR）检测所有菌株的15种不同耐药基因、葡萄球菌盒式染色体mec（staphylococcal cassette chromosome mec, SCCmec）以及精氨酸分解移动元件（arginine catabolic mobile elements, ACMEs）。采用比色微量板试验检测菌株的生物膜形成能力。
结果：19株菌株中16株对苯唑西林耐药且携带mecA基因。对甲氧苄啶/磺胺甲噁唑的耐药率高达81.2%。所有受试MRSHo菌株均对3种检测消毒剂（Septicidine-PC、Septi turbo、Sayacept-HP）敏感。总计15株（78.9%）菌株可形成生物膜。3株菌株可分型为SCCmec V型和VIII型，13株无法分型（untypable, UT），5株携带ACME II型。
结论：研究结果表明，携带高耐药性且SCCmec分型未知的MRSHo未来可能成为儿童等患者临床治疗中的严峻问题。