Antibiotic susceptibility and mechanisms of beta-lactam resistance among clinical strains of Pseudomonas aeruginosa: first report in Algeria.
OBJECTIVE
Pseudomonas aeruginosa is a major causative agent of hospital infections. Studies on this subject being rare in Algeria, we determined the antibiotic susceptibility of P. aeruginosa and investigated the mechanisms of beta-lactam resistance and the spread of multidrug resistant strains in the university affiliated Hospital of Tlemcen (Algeria).


METHODS
One hundred and ninety-nine consecutive strains of P. aeruginosa were collected between November 2005 and February 2007. MICs of antibiotics were measured by the agar dilution method. The resistance mechanisms to beta-lactams were identified phenotypically or by molecular methods (isoelectrofocusing, PCR and sequencing). Strains expressing a secondary beta-lactamase were serotyped and genotyped (Random Amplified Polymorphic DNA).


RESULTS
The proportion of susceptible isolates were: ticarcillin (56%), piperacillin-tazobactam (81%), ceftazidime (88%), cefepime (80%), aztreonam (64%), imipenem (65%), amikacin (83%), tobramycin (81%) and ciprofloxacin (97%) according to the French CASFM breakpoints. Resistance to beta-lactams was linked to the production of transferable beta-lactamases (16%), overproduction of cephalosporinase AmpC (12%) and/or non-enzymatic mechanisms such as the loss of porin OprD (35%) and overproduction of the active efflux system MexAB-OprM (24%). High level resistance to ticarcillin was due to the expression of beta- lactamase OXA-10 alone or associated with TEM-110. A genotypic analysis revealed the spread of a multidrug resistant epidemic clone expressing these two acquired beta-lactamases in the surgical ICU.


CONCLUSIONS
This study shows that resistance to antibiotics, in particular to imipenem of P. aeruginosa, is becoming a cause of concern in the Hospital of Tlemcen.
Drissi
M
M
Laboratoire << Antibiotiques-Antifongiques >>, université Abou Bekr Belkaïd, B.P. 119, Tlemcen 13000, Algeria.
Ahmed
Z Baba
ZB
Dehecq
B
B
Bakour
R
R
Plésiat
P
P
Hocquet
D
D
D000462:Algeria; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006748:Hospital Departments; D006785:Hospitals, University; D007769:Lactams / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D011550:Pseudomonas aeruginosa / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D012703:Serotyping
D007769:Lactams