Dissemination of methicillin-resistant Staphylococcus aureus USA300 sequence type 8 lineage in Latin America.
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 < or =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).


CONCLUSIONS
A variant CA-MRSA USA300 clone has become established in South America and, in some countries, is endemic in hospital settings.
Reyes
Jinnethe
J
Molecular Genetics and Antimicrobial Resistance Unit, Universidad El Bosque, Bogota, Colombia.
Rincón
Sandra
S
Díaz
Lorena
L
Panesso
Diana
D
Contreras
Germán A
GA
Zurita
Jeannete
J
Carrillo
Carlos
C
Rizzi
Adele
A
Guzmán
Manuel
M
Adachi
Javier
J
Chowdhury
Shahreen
S
Murray
Barbara E
BE
Arias
Cesar A
CA
D016521:Electrophoresis, Gel, Pulsed-Field; D007843:Latin America; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity; D010641:Phenotype; D011446:Prospective Studies