Mahmoudi Shima, Mamishi Setareh, Mohammadi Mohsen, Banar Maryam, Ashtiani Mohammad Taghi Haghi, Mahzari Masoumeh, Bahador Abbas, Pourakbari Babak
Pediatric Infectious Diseases Research Center, Tehran University of Medical Sciences, Tehran, Iran,
Department of Infectious Disease, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Infect Drug Resist. 2019 Jan 3;12:137-143. doi: 10.2147/IDR.S185610. eCollection 2019.
The aim of this study was to evaluate both phenotypic and genotypic determinants of mupirocin resistance among methicillin-resistant (MRSA) and methicillin susceptible (MSSA) strains recovered from different clinical samples of children who were admitted to the Children's Medical Center (CMC) Hospital, Tehran, Iran.
A total of 120 clinical isolates of were collected from the microbiology laboratory of CMC Hospital. Antimicrobial susceptibility of the isolates to different antimicrobial agents was determined by disk diffusion method. The methicillin resistance phenotype (MRSA) was identified using a 30 µg cefoxitin disk. The minimum inhibitory concentration (MIC) of mupirocin was determined by broth microdilution method. Strains with mupirocin MIC between 8 and 256 µg/mL were considered as low-level mupirocin resistant (LLMR), and strains with an MIC≥512 µg/mL were considered as high-level mupirocin resistant (HLMR). The presence of genes encoding HLMR (ie, A and B genes) was evaluated by PCR method.
Four out of 120 isolates (3%) had mupirocin MIC≥512 µg/mL and were HLMR; however, no LLMR isolate was detected. Fifty-two isolates (43%) were MRSA, and there were no differences in the distribution of mupirocin resistance among MRSA and MSSA isolates (>0.05). The PCR method identified A gene in two out of four HLMR isolates, and B gene was not detected in any HLMR isolates.
Because of discrepancies between the phenotypic and genotypic patterns of mupirocin resistance and due to the avoidance of false-negative results, it is better to determine the mupirocin resistance by both antibiotic susceptibility tests and PCR method. Considering the increasing need of mupirocin for the control of infections, continuous checking of its susceptibility status is necessary.
本研究旨在评估从伊朗德黑兰儿童医学中心（CMC）医院收治的儿童不同临床样本中分离出的耐甲氧西林金黄色葡萄球菌（MRSA）和甲氧西林敏感金黄色葡萄球菌（MSSA）菌株中莫匹罗星耐药性的表型和基因型决定因素。
从CMC医院微生物实验室共收集了120株临床分离株。采用纸片扩散法测定分离株对不同抗菌药物的敏感性。使用30μg头孢西丁纸片鉴定甲氧西林耐药表型（MRSA）。采用肉汤微量稀释法测定莫匹罗星的最低抑菌浓度（MIC）。莫匹罗星MIC在8至256μg/mL之间的菌株被视为低水平莫匹罗星耐药（LLMR），MIC≥512μg/mL的菌株被视为高水平莫匹罗星耐药（HLMR）。通过PCR方法评估编码HLMR的基因（即A和B基因）的存在情况。
120株分离株中有4株（3%）莫匹罗星MIC≥512μg/mL，为HLMR；然而，未检测到LLMR分离株。52株分离株（43%）为MRSA，MRSA和MSSA分离株中莫匹罗星耐药性分布无差异（>0.05）。PCR方法在4株HLMR分离株中的2株中鉴定出A基因，在任何HLMR分离株中均未检测到B基因。
由于莫匹罗星耐药性的表型和基因型模式存在差异，且为避免假阴性结果，最好通过抗生素敏感性试验和PCR方法来确定莫匹罗星耐药性。考虑到控制感染对莫匹罗星的需求不断增加，有必要持续监测其敏感性状态。
