ABSTRACT
BACKGROUND: Staphylococcus aureus is a human opportunistic pathogen. Its important pathogenicity and the increasingly rate of resistance to methicillin are the main causes of morbidity and mortality. AIM: In order to evaluate the epidemiologic situation of Methicillin Resistant S. aureus (MRSA) at Charles Nicolle hospital. METHODS: A four years retrospective study (January 1999-December 2002) was conducted. RESULTS: 65 non redundant MRSA isolates were collected. Identification was based on morphology, culture and biochemical characters. Antibiotic susceptibility was determined by disk diffusion method. Resistance to methicillin was confirmed by mec A PCR. Molecular typing was performed by Random Amplified Polymorphic DNA using ERIC-IR. Despite a perfect biotypic similarity between strains, ERIC-IR PCR revealed 7 genotypes. CONCLUSION: The combination of phenotypic methods and RAPD fingerprinting were easy to perform routinely for MRSA typing. However, phylogenetic relationship between strains needs more investigations.
Subject(s)
Methicillin-Resistant Staphylococcus aureus/genetics , Genotype , Humans , Phenotype , Retrospective StudiesABSTRACT
Staphylococcal cassette chromosome is a mobile element that carries the gene mecA mediating the methicillin resistance in staphylococci. In Staphylococcus aureus five types of SCCmec have been described, which differs in size and genetic composition among strains. SCCmec typing of 34 non redundant methicillin-resistant S. aureus (MRSA) recovered in 2004 at Charles Nicolle Hospital of Tunis was carried out. The isolates were identified by conventional methods. Methicillin resistance was detected by oxacillin and cefoxitin disks and confirmed by mecA PCR. The SCCmec complex types were determined by using PCR which amplify a sequence overlapping the right SCCmec chromosome junction. Strains were recovered mainly from cutaneous pus (61.7%) and blood cultures (17.64%). They were isolated from different wards: medicine (53.1%) especially from dermatology (41.2%); surgery (40.6%) and pediatrics (3.1%). Only two strains were community-acquired MRSA. Two strains (5.9%) were harboring SCCmec type I; five (14.7%) SCCmec type II and 27 (79.4%) SCCmec type III. The two community-acquired MRSA were harboring type II and III SCCmec, usually found in hospital acquired MRSA. Our findings indicate that there are only three SCCmec types at Charles Nicolle Hospital. However, the existence of SCCmec types II and III in community incite us to investigate more community-acquired MRSA.
