Virtually all methicillin-resistant Staphylococcus aureus (MRSA) infections in the largest Portuguese teaching hospital are caused by two internationally spread multiresistant strains: the ‘Iberian’ and the ‘Brazilian’ clones of MRSA

Abstract

OBJECTIVE: To determine the nature (clonal type and antibiotic resistance pattern) of methicillin-resistant Staphylococcus aureus (MRSA) strains recovered from the largest teaching hospital in Portugal and to detect temporal trends in clonal types during three consecutive surveillance periods in 1992--93, 1994--95 and 1996. METHODS: MRSA strains were characterized by chromosomal SmaI macrorestriction patterns using pulsed-field gel electrophoresis (PFGE) and by DNA fingerprints---applied to ClaI digests---capable of probing two specific areas of the staphylococcal chromosome: (1) the vicinity of the mecA gene, and (2) the attachment site(s) and copy number of transposon Tn554. The combination of these methods can generate 'clonal types' useful for epidemiological tracking of MRSA strains. RESULTS: During the 1992--93 collection period, 65% of MRSA strains carried the mecA polymorph I, Tn554 pattern E and PFGE pattern A (I::E::A)---a clonal type that was used to define the 'Iberian MRSA', which is widely spread throughout southern Europe. The representation of this clone decreased to 42% in 1994--95 and to 20% in 1996. At the same time, a second multiresistant MRSA strain carrying mecA polymorph XI, Tn554 type B and PFGE pattern B (XI::B::B)---a clonal type characteristic of the so-called 'Brazilian MRSA'---increased from 5% in 1992--93 to 36% in 1994--95 and 29% in 1996. CONCLUSIONS: Throughout the four years of surveillance, the Iberian and Brazilian MRSA types and their single subtype variants together have been responsible for the overwhelming majority (close to 90%) of all MRSA infections in the largest teaching hospital of Portugal. The mechanism of epidemicity of these two multiresistant international MRSA clones remains to be elucidated.

Three-Year Assessment of Methicillin-Resistant Staphylococcus aureus Clones in Latin America from 1996 to 1998

“…Recently, Gales et al (14) reported an identical observation, among multidrug-resistant MRSA collected during 1997 to 1998 in Brazil, Chile, and Argentina which exhibited an identical ribotype and similar SmaI PFGE pattern to a representative of the Brazilian MRSA clone. Besides the ability to acquire new genes, including highlevel mupirocin resistance (25), the Brazilian clone seems to spread alarmingly fast and have a great capacity for displacement of other very epidemic clones, as seen in Portugal (2,23) and the Czech Republic (20).…”

Update on the Major Clonal Types of Methicillin-Resistant Staphylococcus aureus in the Czech Republic

“…One of these clones was the pandemic Iberian MRSA (10,18,29,31), which represented 12% of the Czech MRSA isolates. The other distinct multiresistant clone, the Brazilian MRSA, widely spread in South America (3,8,34) and Portugal (4,25), represented 80% of the Czech isolates of 1996-1997.…”

Staphylococcus aureus bacteremia: comparison of two periods and a predictive model of mortality

“…In Brazil, the SP genotype profile, determined by pulsed field gel electrophoresis, is the most common, and it was the most prevalent isolated MRSA clone in our study (86%) [34]. This clone may have specific virulence characteristics that are different from those of other clones.…”