Three-year assessment of methicillin-resistant Staphylococcus aureus clones in Latin America from 1996 to 1998

Abstract

Four hundred ninety-nine methicillin-resistant Staphylococcus aureus (MRSA) isolates recovered from 1996 to 1998 from 22 hospitals in five countries of Latin America-Argentina, Brazil, Chile, Uruguay and Mexico-were examined for antimicrobial susceptibility and clonal type in order to define the endemic clones in those hospitals. The hybridization of ClaI restriction digests with the mecA- and Tn554-specific DNA probes combined with pulsed-field gel electrophoresis of chromosomal SmaI digests (ClaI-mecA::ClaI-Tn554::PFGE clonal types) documented not only the predominance and persistence of the Brazilian clone (XI::B::B) in Brazil (97%) and Argentina (86%) but also its massive dissemination to Uruguay (100%). Moreover, a close relative of the Brazilian clone (XI::kappa::B) was highly represented in Chile (53%) together with a novel clone (47%) (II::E'::F) resistant to pencillin, oxacillin, ciprofloxacin, chloramphenicol, clindamycin, erythromycin, and gentamicin. A unique clonal type (I::NH::M) was detected in Mexico among pediatric isolates and was resistant to penicillin, oxacillin, and gentamicin only. This study clearly documented the very large capacity for geographic expansion and the persistence of the Brazilian clone, contributing not only to the increasing uniformity of the MRSA in South America but worldwide as well.

FIG. 1

ClaI-Tn554 patterns identified among the Latin American strains. Patterns A, B, E, AA, M (17), κ (18), B′ (7), and ξ (19) were previously described. Patterns E′, η, MM, NN, OO, PP, and QQ correspond to novel patterns described in this study. Lanes 1 and 17, molecular weight markers, 1-kb ladder; lane 2, AGT55 (pattern E); lane 3, CHL5 (pattern E′); lane 4, CHL1 (pattern κ); lane 5, AGT115 (pattern A); lane 6, AGT84 (pattern M); lane 7, BRA131 (pattern AA); lane 8, URU105 (pattern B); lane 9, URU149 (pattern B′); lane 10, AGT27 (pattern PP); lane 11, AGT8 (pattern QQ); lane 12, BRA135 (pattern MM); lane 13, BRA145 (pattern NN); lane 14, BRA162 (pattern OO); lane 15, CHL18 (pattern ξ); lane 16, CHL113 (pattern η).

FIG. 2

(A) SmaI PFGE patterns of the major MRSA clones found in five countries of Latin America (Argentina, Brazil, Uruguay, Chile, and Mexico). Lanes 1 and 18, lambda ladder; lanes 2, 10, and 17, NCTC 8325; lanes 3 to 7 and 11, representatives of the Brazilian clone: lanes 3 and 11 (HU25, XI::B::B, Brazil [35]), lane 4 (BRA10, XI::B::B, Brazil), lane 5 (AGT35, XI::B::B, Argentina), lane 6 (URU1, XI::B′::B, Uruguay), lane 7 (CHL1, XI::κ::B, Chile). Lane 8, representative of the Chilean clone (CHL93, II::E′::F, Chile). Lane 9, representative of the Mexican clone (MEX58, I::NH::M, Mexico). Lanes 12 to 16, MSSA strains from Argentina: ARG38, ARG102, ARG110, ARG111, and ARG119, respectively. (B) SmaI PFGE of Fig. 2A hybridized with a mecA probe. (C) SmaI PFGE of Fig. 2A hybridized with a Tn554 probe.

FIG. 3

Evolution of the major clonal types found in five countries of Latin America through two periods of time: 1996 to 1997 and 1998.

FIG. 4

(A) Comparison of PFGE patterns of the Mexican and Chilean clones with international PFGE patterns stored in the CEM/NET database. Representatives from different countries are shown. Lanes 1 and 21, lambda ladder. Lanes 2, 14, and 20, NCTC 8325. Lane 3, CHL5, II::E′::F (Chile); lane 4, HDE288, II::NH::D (Portugal) (29); lane 5, COB5, II::NH::D (Colombia) (15); lane 6, E2125, II::NH::A1 (Denmark) (7); lane 7, E2213, II::NH::A9 (Denmark) (7); lane 8, PLN49, II::NH::I (Poland); lane 9, ITL262, II::NH::C (Italy); lane 10, ITL370, II::E::E (Italy); lane 11, ARG33, II::E::C (Argentina) (4); lane 12, TUR5, II::ηη::A (Turkey); lane 13, HUR24, II::q::D (Hungary) (22); lane 15, MEX81, I::NH::M (Mexico); lane 16, GRE5, VII′::NH::A (Greece); lane 17, POL1, I::NH::A (Poland) (18); lane 18, JP1, I::A::A (Japan) (1); lane 19, HPV 107, I::E::A (Portugal) (33). (B) Computer-generated dendogram of the PFGE of Fig. 4. Results are from an analysis of similarity by Dice's coeficient; clustering was done by the minimum linkage method (26).