Study On The Antimicrobial Susceptibility And Homology Of Methicillin-resistant Staphylococcus Aureus

1. BackgroundMethicillin-resistant staphylococcus aureus (MRSA) was found firstly in England. Today it becomes one of the important pathogens in nosocomial infection. It is usually multiresistant to many antibacterial agents included methicillin. There exits sporadic occurance or epidemic outbreak. The mortality of the infection caused by MRSA is high. The infection may be spreaded widely and difficult to be controlled. How to use antibacterial agents reasonably is the key to treat MRSA infection.In orter to demonstrate the susceptibility and the epidemiology of MRSA, we investigated the susceptibility of 50 strains of MRSA to 18 kinds of antibacterial agents and analyzed the homology among these strains.2. Materials and methodsWe collected 50 strains of MRSA from clinical specimens in the First Affiliated Hospital, College of Medicine, Zhejiang University. Kerby-Bauer disk diffusion testwas used to ditect the susceptibility of 50 strains of MRSA to 18 kinds of antibacterial agents, and Pulsed-field gel electrophoresis( PFGE ) was used to analyze the homologyof the strains.3. ResultsThe susceptible rates of 50 strains of MRSA to vancomycin, teicoplanin, linezolid, streptogramin are all 100%, while the ones to rifampicin and phosphomycin are 92% and 72% respectively. The susceptible rate to other antibacterial agents are 0-42%.Six different PFGE types ( A-F ) were found among 50 strains of MRSA, most of MRSA were type A ( 27 strains ) , type B ( 10 strains ) and type C( 10 strains). Type A and type B spread from Jun. 2001 to Apr. 2002. Type C spread from Jul. 2001 to Apr. 2002. 34% of strains were related with ICU. The epidemic strains spread over different wards.4. ConclusionThe prevalent strains were multiresistant. Vancomycin, teicoplanin, linezolid, streptogramin have good antibacterial activity, and was the first choice to control MRSA infection. We also can choose the susceptible antibacterial agents according to the results of drug sensitivity test.MRSA spread in our hospital from Jun. 2001 to Apr. 2002. ICU ward is the high incident region of MRSA infection. Neuro-surgical wardliver-gallbladder-pancreas-surgical ward and VIP ward are the relatively high incidentregion of MRSA infection. The strains isolated from the same patient may be differenttypes.