Vigilancia de resistencia a agentes antimicrobianos en Staphylococcus aureus y Enterococci provenientes de Hospitales en Colombia, Ecuador, Venezuela y Perú (2006-2007)

A variant CA-MRSA USA300 clone has become established in South America and, in some countries, is endemic in hospital settings.
Reyes, J.
Rincón, S.
Díaz, L.
Panesso, D.
Contreras, GA.
Zurita, J.
Carrillo, C.
Merentes, A.
Guzmán, M.
Adachi, J.
Chowdhury, S.
Murray, BE.
Arias, CA.
Grupo de investigación:
Unidad de Genética y Resistencia Antimicrobiana - UGRA

Background.Methicillin-resistant Staphylococus aureus (MRSA) is an important nosocomial and community-associated (CA) pathogen. Recently, a variant of the MRSA USA300 clone emerged and disseminated in South America, causing important clinical problems. Methods.S. aureus isolates were prospectively collected (2006–2008) from 32 tertiary hospitals in Colombia, Ecuador, Peru, and Venezuela. MRSA isolates were subjected to antimicrobial susceptibility testing and pulsed-field gel electrophoresis and were categorized as health care-associated (HA)-like or CA-like clones on the basis of genotypic characteristics and detection of genes encoding Panton-Valentine leukocidin and staphylococcal cassette chromosome (SCC) mec IV. In addition, multilocus sequence typing of representative isolates of each major CA-MRSA pulsotype was performed, and the presence of USA300-associated toxins and the arcA gene was investigated for all isolates categorized as CA-MRSA.

Results: A total of 1570 S. aureus were included; 651 were MRSA (41%)—with the highest rate of MRSA isolation in Peru (62%) and the lowest in Venezuela (26%)—and 71%, 27%, and 2% were classified as HA-like, CA-like, and non-CA/HA-like clones, respectively. Only 9 MRSA isolates were confirmed to have reduced susceptibility to glycopeptides (glycopeptide-intermediate S. aureus phenotype). The most common pulsotype (designated ComA) among the CA-like MRSA strains was found in 96% of isolates, with the majority (81%) having a ⩽6-band difference with the USA300-0114 strain. Representative isolates of this clone were sequence type 8; however, unlike the USA300-0114 strain, they harbored a different SCCmec IV subtype and lacked arcA (an indicator of the arginine catabolic mobile element).