[Carbapenemase detection in Acinetobacter baumannii clones resistant to imipenem].
BACKGROUND
The aim of this study was to detect carbapenemases in imipenem-resistant Acinetobacter baumannii isolates obtained in the microbiology department of a Basque Country Public Health Service hospital over a period of 19 months, and to genetically characterize the resistant clones.


METHODS
Susceptibility tests to imipenem, meropenem, ticarcillin, ceftazidime, cefotaxime, cefepime and aztreonam were done by determining the minimum inhibitory concentration on agar plates. A tRNA technique was used for species identification and PCR with primers ERIC2, AP3 and M13 for genetic typing of resistant isolates. Carbapenemase production was detected by the Hodge test and metallo-beta-lactamase by the EDTA test and Etest MBL.


RESULTS
A total of 76 isolates were resistant to imipenem and 49 of these were resistant to all the betalactam antibiotics tested. Genetic typing showed three predominant clones, denominated I (9 isolates), II (48 isolates) and III (8 isolates). Hodge and EDTA tests were positive in 45 and 8 isolates belonging to clone II, 8 and 4 belonging to clone I and 7 and 3 belonging to clone III, respectively. The Etest confirmed 7 results (45% of the 17 positive EDTA test isolates).


CONCLUSIONS
Our results show that one factor contributing to the high level of imipenem resistance in the isolates analyzed is dissemination of a predominant, multiresistant clone able to produce OXA-type carbapenemases and metallo-beta-lactamases.
Gallego
Lucía
L
Departamento de Inmunología, Microbiología y Parasitología, Facultad de Medicina y Odontología, Universidad del País Vasco, Bilbao, Vizcaya, Spain. oipgaan1@lg.ehu.es
Canduela
Miren Josune
MJ
Sevillano
Elena
E
Pujana
Idoia
I
Calvo
Felícitas
F
Umaran
Adelaida
A
Martín
Gloria
G
D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D015780:Carbapenems / Q000378:metabolism / Q000494:pharmacology*; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics / Q000502:physiology; D005838:Genotype; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D015337:Multicenter Studies as Topic; D013030:Spain / Q000453:epidemiology; D013845:Thienamycins / Q000494:pharmacology; D018440:beta-Lactam Resistance / Q000235:genetics / Q000502:physiology; D001618:beta-Lactamases / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D047090:beta-Lactams / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D013845:Thienamycins; D047090:beta-Lactams; D015378:Imipenem; D001618:beta-Lactamases; C488541:beta-lactamase OXA-40, Acinetobacter baumannii; C063912:carbapenemase; D000077731:Meropenem