Study On The Resistance And Molecular Epidemiology In Methicillin-resistant Staphylococcus Haemolyticus

Part I Meticillin Resistance Staphylococcus Haemolyticus and Resistance in Isolates of Staphylococcus HaemolyticusBackground Staphylococcus haemolyticus is common in coagulase-negative Staphylococcus (CNS) and the detection rate is normally second only to Staphylococcus epidermidis, even higher in some areas, ranked No.1. The rapid emergence, evolution, dissemination, epidemic of methicillin-resistant Staphylococcus haemolyticus (MRSH) create great difficulties for clinical treatment. MRSH are resisent to most antimicrobial agents, only sensitive to glycopeptides. The expanded use of these antibiotics has resulted in emergence of S. haemolyticus resistance to glycopeptides. Thus, in order to better guide clinical therapy, we studied the detection of MRSH and resistance in 103 S. haemolyticus isolates in the part hospitals of Anhui Province in 2005.Objective To investigate the prevalence of MRSH and resistance in S. haemolyticus isolates. To provide the basis for rational use of antimicrobial agents.Methods 103 clinical isolates of S. haemolyticus were collected from 14 hospitals in Anhui province, China. MRSH were detected by cefoxifin disc test and mecA-PCR. Susceptibilities were tested by agar dilution method. Results were analyzed according to CLSI 2008. Results 86.4% and 80.6% of isolates were MRSH detected by mecA-PCR and cefoxifin disc test. MRSH were highly resistant to penicillin, cefazolin, cefuroxime, ceftriaxone, tetracycline, ciprofloxacin, and clindamycin. The resistance rates to amikacin, rifampicine, chloramphenicol were 16.9%, 12.0%, 31.3%, respectively. All isloates were susceptible to vancomycin and teicoplanin. Except for tetracycline, amikacin, rifampicine, and chloramphenicol, the resistance rates to other antimicrobial agents were significantly higher in MRSH than in MSSH (P<0.05).Conclusions MRSH were resistant to most of antimicrobial agents, except for amikacin, rifampicine, chloramphenicol, and highly prevalent in S. haemolyticus isolates. All isloates were susceptible to vancomycin, teicoplanin. Detection of MRSH by cefoxifin disc test and mecA-PCR had no significant difference(P>0.05). More attention should be paid to survey and detect those strains. Part II Analysis of Staphylococcal Cassette Chromosome mec (SCCmec) Typing and Homology in Staphylococcus HaemolyticusBackground Recently, with the detection rate of MRSH isolates growing, it had been more than 80% in some areas. MRSH has become an important pathogens in nosocomial infection throughout the world. MRSH are resistant to most of antimicrobial agents, its effective treatment is glycopeptides: vancomycin, teicoplanin, and oxazolidinones: linezolid. The main mechanism for drug-resistant strains is carrying the mecA gene, which is located in a new mobile devices SCCmec (Staphylococcal Cassette Chromosomemec mec). SCCmec not only carry mecA gene, but also bring the other resistance genes, therefore, form the multi-drug resistance. Currently, 5 types of SCCmec have been found, that is, SCCmecâ… ,â…¡,â…¢,â…£andâ…¤. Most of SCCmecâ… ,â…¡,â…¢are hospital-acquired (HA-MRS), while SCCmecâ…£,â…¤are mostly community-acquired (CA-MRS). In order to understand SCCmec types and homology in MRSH isloted from Anhui Province, we conducted related research.Objective 1) To investigate Staphylococcal Cassette Chromosome mec (SCCmec) types and the differences in resistance of different SCCmec types in MRSH. 2) To analysis the homology of different SCCmec types in MRSH.Methods 1) SCCmec types were indentifed by multiplex PCR. 2) Molecular typing was analyzed by Enterobacterial Repetitive Intergenic Consensus polymerase chain reaction ( ERIC-PCR). Results 83 MRSH were detected in isolates and SCCmecâ… ,â…¡,â…¢,â…£, more than one type and nontypable strains were 23, 10, 24, 1, 22, 3, respectively. Patterns of ERIC-PCR were same in many isolates with same SCCmec type. Except for rifampin and amikacin, MRSH were high resistant to most antimicrobial agents, and no vancomycin, teicoplanin-resistant strains were found. Resistance rate of cefazolin, cefuroxime and ceftriaxone was higer in SCCmecâ… ,â…¢thanâ…¡strains, while it of chloramphenicl was lower in SCCmecâ… ,â…¢isolates.Conclusion 1) The prevalence of SCCmecâ… ,â…¢was high in 83 isolates of MRSH. 2) There were some MRSH detected more than one type. 3) Different SCCmec types strains have different resistance profile of some antimicrobial, which further illustrated the relation between the resistance and SCCmec types carrying the different resistance genes. 4) Clone spread was found in some islotes.