Rapid and widespread dissemination of multidrug-resistant blaCMY-2 Salmonella Typhimurium in Mexico.
OBJECTIVE
We describe the emergence and dissemination of multidrug-resistant (MDR) Salmonella Typhimurium in humans, retail meat and food animals from Yucatan, Mexico.


METHODS
Salmonella Typhimurium isolates were collected through an active surveillance system and tested for susceptibility to 12 antimicrobial agents. Isolates that were non-susceptible to ceftriaxone were tested with 10 additional antimicrobials and assayed by PCR for the presence of CMY, CTX-M, SHV, TEM and OXA beta-lactamase genes. Plasmid-borne phenotypes were identified by transfer to susceptible Escherichia coli. Isolates from humans, retail meat and food animals were compared by PFGE to determine genetic relatedness.


RESULTS
MDR Salmonella Typhimurium containing a plasmid-mediated blaCMY-2 AmpC beta-lactamase rose from 0% (0/27) during 2000 and 2001 to 75% (63/84) in 2004 and 2005 (P<0.0001). MDR blaCMY-2 Salmonella Typhimurium (n=115) was most common in ill children (44.3%) and pork or swine intestine (36.5%). In several cities, MDR blaCMY-2 Salmonella Typhimurium from retail meat or swine intestine exhibited PFGE patterns and antibiograms indistinguishable from those in strains recovered from hospitalized children. The CMY gene was transferred to E. coli by electroporation, along with resistance to three to six other antimicrobials. Children with MDR blaCMY-2 Salmonella Typhimurium infection (n=39) had a higher frequency of systemic infection (13% versus 0%), mortality (8% versus 0%) and hospital re-admission due to protracted diarrhoea (28% versus 17%) than children with non-MDR-Salmonella Typhimurium (n=24), although the difference was not statistically significant.


CONCLUSIONS
The rapid and widespread dissemination of MDR blaCMY-2 Salmonella Typhimurium in Mexico calls for urgent interventions to contain this potentially fatal pathogen.
Zaidi
Mussaret B
MB
Depto. de Investigacion, Laboratorio de Investigación, Hospital General O'Horan, Av. Itzaes x Jacinto Canek, Mérida C.P. 97000, Yucatan, Mexico. mbzaidi@prodigy.net.mx
Leon
Verónica
V
Canche
Claudia
C
Perez
Carolina
C
Zhao
Shaohua
S
Hubert
Susannah K
SK
Abbott
Jason
J
Blickenstaff
Karen
K
McDermott
Patrick F
PF
D000818:Animals; D002511:Cephalosporins / Q000494:pharmacology; D002645:Chickens; D002648:Child; D003967:Diarrhea / Q000209:etiology / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005506:Food Contamination; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008460:Meat / Q000382:microbiology; D008800:Mexico / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D012480:Salmonella Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics*; D012703:Serotyping; D013552:Swine; D001618:beta-Lactamases / Q000235:genetics*
D002511:Cephalosporins; C102789:cephamycinase bla(CMY-1); D001618:beta-Lactamases