[Extended-spectrum beta-lactamases-producing Stenotrophomonas maltophilia strains: CTX-M enzymes detection and virulence study].
OBJECTIVE
To study the beta-lactamases content of Stenotrophomonas maltophilia strains and to evaluate the virulence potential of these strains with the in vivo Caenorhabditis elegans model.


METHODS
From 1st January 2006 to 31st December 2006, a monitoring programme to study multidrug resistant Gram-negative bacteria including extended-spectrum beta-lactamases (ESBL)-producing S. maltophilia was conducted at Nîmes University Hospital and Perpignan Hospital. The ESBL production was confirmed by the double-disk synergy test using ceftazidime, cefotaxime and cefepime disks associated with clavulanic acid disk. The strains were characterized phenotypically (beta-lactamase[s] identification) and genotypically (pulsed-field gel electrophoresis, plasmid analysis) and evaluated for their virulence with the in vivo nematode C. elegans model (establishment of survival curves [LT50]).


RESULTS
Twelve ESBL-producing S. maltophilia strains were isolated in eight patients (median age: 65 years+/-19) mainly during skin infections (41.7%). The ESBL content revealed the presence of four CTX-M-15-producing strains at the same patient. The analysis by ECP confirmed that the four strains were identical. The plasmid analysis demonstrated that the plasmid carrying CTX-M-15 in the worldwide clonal Escherichia coli O25-ST131 strain and S. maltophilia were different. The C. elegans model confirmed that S. maltophilia strains presented a low virulence potential (LT50=4.5days+/-0.5 according to the strains and nematode death in 10days+/-1) whatever their resistance.


CONCLUSIONS
For the first time in France, a CTX-M-15-producing S. maltophilia strain has been identified. The in vivo model confirmed that these bacteria have a low potential virulence. However, these strains were isolated from "immunocompromised" and multihospital patients demonstrating the necessary monitoring of these patients. The CTX-M after diffusing in hospitals and community in E. coli strains seem to spread in other Gram-negative bacteria.
Espri 26, Inserm, UFR de médecine, Institut national de la santé et de la recherche médicale, université Montpellier-I, Nîmes, France. jean.philippe.lavigne@chu-nimes.fr
J-P
JP
Lavigne
J-B
JB
Gaillard
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G
Bourg
C
C
Tichit
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E
Lecaillon
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A
Sotto
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017173:Caenorhabditis elegans / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D005260:Female; D005602:France / Q000453:epidemiology; D005798:Genes, Bacterial; D005838:Genotype; D016905:Gram-Negative Bacterial Infections / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D011815:R Factors / Q000235:genetics; D013045:Species Specificity; D020615:Stenotrophomonas maltophilia / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D013379:Substrate Specificity; D014774:Virulence / Q000235:genetics; D018440:beta-Lactam Resistance / Q000235:genetics; D001618:beta-Lactamases / Q000032:analysis* / Q000145:classification / Q000235:genetics
C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases
Etude de souches de Stenotrophomonas maltophilia sécrétrices de BLSE : détection de CTX-M et étude de la virulence.