Dar Javid A, Thoker Manzoor A, Khan Jamal A, Ali Asif, Khan Mohammed A, Rizwan Mohammed, Bhat Khalid H, Dar Mohammad J, Ahmed Niyaz, Ahmad Shamim
Microbiology Division, Institute of Ophthalmology, J, N, Medical College, Aligarh Muslim University, Aligarh, India.
Ann Clin Microbiol Antimicrob. 2006 Sep 14;5:22. doi: 10.1186/1476-0711-5-22.
The study was conducted between 2000 and 2003 on 750 human subjects, yielding 850 strains of staphylococci from clinical specimens (575), nasal cultures of hospitalized patients (100) and eye & nasal sources of hospital workers (50 & 125 respectively) in order to determine their epidemiology, acquisition and dissemination of resistance genes.
Organisms from clinical samples were isolated, cultured and identified as per the standard routine procedures. Susceptibility was measured by the agar diffusion method, as recommended by the National Committee for Clinical Laboratory Standards (NCCLS). The modified method of Birnboin and Takahashi was used for isolation of plasmids from staphylococci. Pulsed-field gel electrophoresis (PFGE) typing of clinical and carrier Methicillin resistant Staphylococcus aureus (MRSA) strains isolated during our study was performed as described previously.
It was shown that 35.1% of Staphylococcus aureus and 22.5% of coagulase-negative staphylococcal isolates were resistant to methicillin. Highest percentage of MRSA (35.5%) was found in pus specimens (n = 151). The multiple drug resistance of all MRSA (n = 180) and Methicillin resistant Coagulase-negative Staphylococcus aureus (MRCNS) (n = 76) isolates was detected. In case of both methicillin-resistant as well as methicillin-sensitive Saphylococcal isolates zero resistance was found to vancomycin where as highest resistance was found to penicillin G followed by ampicillin. It was shown that the major reservoir of methicillin resistant staphylococci in hospitals are colonized/infected inpatients and colonized hospital workers, with carriers at risk for developing endogenous infection or transmitting infection to health care workers and patients. The results were confirmed by molecular typing using PFGE by SmaI-digestion. It was shown that the resistant markers G and T got transferred from clinical S. aureus (JS-105) to carrier S. aureus (JN-49) and the ciprofloxacin (Cf) and erythromycin (E) resistance seemed to be chromosomal mediated. In one of the experiments, plasmid pJMR1O from Staphylococcus aureus coding for ampicillin (A), gentamicin (G) and amikacin (Ak) resistance was transformed into Escherichia coli. The minimal inhibitory concentrations (MICs) for A and G were lower in E. coli than in S. aureus. However, the MIC for Ak was higher in E. coli transformants than in S. aureus.
There is a progressive increase in MRSA prevalence and multi-drug resistance in staphylococci. Vancomycin is still the drug of choice for MRSA infections. The major reservoir of methicillin resistant staphylococci in hospitals is colonized/infected inpatients and colonized hospital workers. Resistance transfer from staphylococci to E. coli as well as from clinical to carrier staphylococci due to antibiotic stress seemed to be an alarming threat to antimicrobial chemotherapy.
该研究于2000年至2003年期间对750名人类受试者进行，从临床标本（575份）、住院患者的鼻腔培养物（100份）以及医院工作人员的眼部和鼻腔样本（分别为50份和125份）中获取了850株葡萄球菌，以确定其流行病学特征、耐药基因的获得和传播情况。
按照标准常规程序从临床样本中分离、培养和鉴定微生物。药敏试验采用美国国家临床实验室标准委员会（NCCLS）推荐的琼脂扩散法。采用改良的Birnboin和Takahashi方法从葡萄球菌中分离质粒。对研究期间分离出的临床和携带耐甲氧西林金黄色葡萄球菌（MRSA）菌株进行脉冲场凝胶电泳（PFGE）分型，方法如前所述。
结果显示，35.1%的金黄色葡萄球菌分离株和22.5%的凝固酶阴性葡萄球菌分离株对甲氧西林耐药。在脓液标本（n = 151）中发现的MRSA比例最高（35.5%）。检测了所有MRSA（n = 180）和耐甲氧西林凝固酶阴性金黄色葡萄球菌（MRCNS）（n = 76）分离株的多重耐药性。对于耐甲氧西林和对甲氧西林敏感的葡萄球菌分离株，发现对万古霉素均无耐药，而对青霉素G耐药性最高，其次是氨苄西林。结果表明，医院中耐甲氧西林葡萄球菌的主要储存宿主是定植/感染的住院患者和定植的医院工作人员，这些携带者有发生内源性感染或将感染传播给医护人员和患者的风险。通过SmaI酶切的PFGE分子分型证实了该结果。结果显示，耐药标记G和T从临床金黄色葡萄球菌（JS - 105）转移到携带的金黄色葡萄球菌（JN - 49），环丙沙星（Cf）和红霉素（E）耐药性似乎是由染色体介导的。在其中一项实验中，将编码氨苄西林（A）、庆大霉素（G）和阿米卡星（Ak）耐药性的金黄色葡萄球菌质粒pJMR1O转化到大肠杆菌中。大肠杆菌中A和G的最低抑菌浓度（MIC）低于金黄色葡萄球菌。然而，大肠杆菌转化体中Ak的MIC高于金黄色葡萄球菌。
MRSA的患病率和葡萄球菌的多重耐药性呈逐渐上升趋势。万古霉素仍然是MRSA感染的首选药物。医院中耐甲氧西林葡萄球菌的主要储存宿主是定植/感染的住院患者和定植的医院工作人员。由于抗生素压力导致的葡萄球菌向大肠杆菌以及从临床葡萄球菌向携带葡萄球菌的耐药性转移似乎对抗菌化疗构成了令人担忧的威胁。
