Emergence of extended-spectrum beta-lactamases and AmpC-type beta-lactamases in human Salmonella isolated in Spain from 2001 to 2005.
OBJECTIVE
To study the resistance to third-generation cephalosporins in Salmonella strains isolated from humans in a 5 year period in Spain, and to identify the responsible genes and their dissemination.


METHODS
Twenty-seven isolates were analysed by PCR and sequencing to identify the genes responsible for the beta-lactamase resistance phenotypes. The transferability of the phenotypes was tested by conjugation to Escherichia coli K12J53, plasmid detection with S1-PFGE, hybridization and PCRs of the transconjugants. The genetic relationship was determined by PFGE.


RESULTS
We found bla(CTX-M-9) and bla(CTX-M-10) in Salmonella Virchow PT19. bla(CTX-M-14) was detected in Salmonella (IV) 44:z(4),z(23):-, Salmonella Enteritidis PT6a, Salmonella Typhimurium DT193 and Salmonella Typhimurium DT104B. bla(CTX-M-1) was found in Salmonella Litchfield. bla(CTX-M-15) and bla(CTX-M-32) were found in Salmonella Enteritidis PT1. bla(SHV-12) was found in Salmonella Blockley, Salmonella Hadar PT2, Salmonella Enteritidis PT21, Salmonella Enteritidis PT1 and Salmonella Bredeney. bla(SHV-2) was found in Salmonella Livingstone. bla(CMY-2) was detected in Salmonella Bredeney, Salmonella Newport, Salmonella Enteritidis PT5b and Salmonella Heidelberg. bla(DHA-1) was detected for the first time in Spain in Salmonella Newport. One strain of Salmonella Senftenberg harboured two extended-spectrum beta-lactamases, bla(SHV-12) and bla(CTX-M-9). We have found a large variety of beta-lactamase families as well as several members of major relevance, such as CTX-M-15, CTX-M-32, CMY-2 and DHA-1. XbaI-PFGE, conjugation assays and S1-PFGE hybridization showed that all these beta-lactamases were mediated by plasmids.


CONCLUSIONS
This study demonstrates the emergence of a public health risk related to resistance to beta-lactams in Salmonella. The resistance trends need to be monitored carefully.
González-Sanz
Rubén
R
Instituto de Salud Carlos III, Centro Nacional de Microbiología, Majadahonda, Madrid, Spain. ruben.gs@isciii.es
Herrera-León
Silvia
S
de la Fuente
Manuela
M
Arroyo
Margarita
M
Echeita
M Aurora
MA
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010957:Plasmids / Q000032:analysis; D016133:Polymerase Chain Reaction / Q000379:methods; D012475:Salmonella / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D012480:Salmonella Infections / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013030:Spain; D055815:Young Adult; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004269:DNA, Bacterial; D001618:beta-Lactamases