Epidemiological and clinical features associated with colonisation/infection by Acinetobacter baumannii with phenotypic heterogeneous resistance to carbapenems.
The objective of this study was to identify risk factors for the acquisition of Acinetobacter baumannii with phenotypic heterogeneous resistance (PHR) to carbapenems and to determine whether these factors are similar to those associated with A. baumannii not showing this phenotype. Microbiological and clinical data from 211 patients included in the GEIH-Ab 2000 project were used. Isolates of A. baumannii were studied for their susceptibility to imipenem (IPM) by microdilution and for PHR to IPM as determined by the presence of colonies growing within the inhibition zone of IPM disks. Isolates were divided into three groups: (i) IPM-PHR isolates, i.e. susceptible and non-susceptible A. baumannii displaying PHR to IPM; (ii) non-IPM-PHR isolates, i.e. susceptible A. baumannii showing an inhibition halo but no colonies growing within it; and (iii) IPM-FR isolates, i.e. fully resistant A. baumannii displaying no halo of inhibition. IPM-PHR isolates of A. baumannii were more commonly isolated from respiratory tract samples and less commonly from urine, and were more frequently causes of infection than were IPM-FR isolates. Independent risk factors identified in patients with IPM-PHR isolates were Intensive Care Unit admission, surgery, and previous use of piperacillin/tazobactam or carbapenems, whilst risk factors for IPM-FR and IPM-PHR were previous use of cephalosporins and isolation from a urine sample. In conclusion, risk factors associated with colonisation/infection by isolates of A. baumannii with PHR to carbapenems are similar to those previously described for isolates resistant to carbapenems.
Infectious Diseases and Clinical Microbiology Unit, University Hospital Virgen Macarena, University of Seville, Avda. Sánchez Pizjuán s/n, 41009 Sevilla, Spain. felipefc@us.es
Felipe
F
Fernández-Cuenca
M
M
Gómez-Sánchez
Jesús
J
Rodríguez-Baño
Luis
L
Martínez-Martínez
Jordi
J
Vila
Germán
G
Bou
Alvaro
A
Pascual
D000151:Acinetobacter Infections / Q000453:epidemiology* / Q000382:microbiology / Q000473:pathology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D018440:beta-Lactam Resistance
D000900:Anti-Bacterial Agents; D015780:Carbapenems; D015378:Imipenem