Beta-lactam and aminoglycoside resistance rates and mechanisms among Pseudomonas aeruginosa in French general practice (community and private healthcare centres).
OBJECTIVE
The aim of this study was to assess antibiotic resistance rates and mechanisms of beta-lactam and aminoglycoside resistance among isolates of Pseudomonas aeruginosa isolated in the extra-hospital setting (community and private healthcare centres).


METHODS
During a 4 month period, 226 non-repetitive strains of P. aeruginosa were collected from patients residing in private healthcare centres (73.5%) or at home (26.5%). Resistance rates were evaluated by MIC determination, and beta-lactam and aminoglycoside resistance was analysed by phenotypic tests, PCR amplification, cloning and sequencing.


RESULTS
Among the ticarcillin-resistant strains (38.1%), 33.7% overexpressed their chromosomal cephalosporinase, 27.9% produced acquired penicillinases (21 PSE-1, 2 OXA-21 and 1 TEM-2), 4.7% produced extended-spectrum beta-lactamases (ESBLs) (3 TEM-21 and 1 SHV-2a) and 45.3% possessed a non-enzymatic resistance (NER). Thus, 88.4% had a single mechanism of resistance, whereas 11.6% cumulated several mechanisms. No carbapenemases were detected among the 6.6% imipenem-resistant strains. With regard to aminoglycosides, 23.0% of the strains exhibited an acquired resistance to gentamicin (GEN), tobramycin (TOB), amikacin (AMK) or netilmicin (NET). Enzymatic resistance was more frequent (71.2%) than NER (34.6%). Various aminoglycoside modifying enzymes were associated with overlapping phenotypes: 36.5% strains produced AAC(6')-I with either a serine (GEN-TOB-NET) or a leucine (TOB-NET-AMK) at position 119, or both variants (GEN-TOB-NET-AMK); 21.2% expressed ANT(2'')-I (GEN-TOB), 7.7% AAC(3)-II (GEN-TOB-NET), 5.8% AAC(3)-I (GEN) and 1.9% AAC(6')-II (GEN-TOB-NET-AMK) or AACA7 (TOB-NET-AMK).


CONCLUSIONS
Antibiotic resistance rates in P. aeruginosa were globally similar in general practice as in French hospitals. This first analysis of resistance mechanisms showed an unexpectedly high frequency of ESBLs and an unusual distribution of aminoglycoside modifying enzymes.
Dubois
Véronique
V
UMR 5234, CNRS, Université de Bordeaux 2, 146 rue Léo Saignat, 33076 Bordeaux, France. veronique.dubois@bacterio.u-bordeaux2.fr
Arpin
Corinne
C
Dupart
Virginie
V
Scavelli
Aline
A
Coulange
Laure
L
André
Catherine
C
Fischer
Isabelle
I
Grobost
Frédéric
F
Brochet
Jean-Philippe
JP
Lagrange
Isabelle
I
Dutilh
Brigitte
B
Jullin
Jacqueline
J
Noury
Patrick
P
Larribet
Gilberte
G
Quentin
Claudine
C
D000123:Acetyltransferases / Q000096:biosynthesis; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D003151:Community Health Centers; D017714:Community-Acquired Infections / Q000382:microbiology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005260:Female; D005602:France; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009713:Nucleotidyltransferases / Q000096:biosynthesis; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000096:biosynthesis; D047090:beta-Lactams / Q000494:pharmacology*
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D047090:beta-Lactams; D000123:Acetyltransferases; C019681:aminoglycoside acetyltransferase; D009713:Nucleotidyltransferases; C061037:aminoglycoside 6-adenylyltransferase; D001618:beta-Lactamases