PCR-based DNA fingerprinting (REP-PCR, AP-PCR) and pulsed-field gel electrophoresis characterization of a nosocomial outbreak caused by imipenem- and meropenem-resistant Acinetobacter baumannii.
OBJECTIVE
To demonstrate the usefulness of REP-PCR and AP-PCR on molecular typing of A. baumannii isolates.


METHODS
From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid-23 in five intensive care units (ICUs) and six at two different medical departments-were either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs of 64-256 mg/L). A wide antibiotic multiresistance profile was observed with IMRAB strains, and only tobramycin, sulbactam and colistin displayed valuable activity. For typing IMRAB isolates, repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) and arbitrary primer sequence-based polymerase chain reaction (AP-PCR) methods were used and compared with pulsed-field gel electrophoresis (PFGE) as reference technique. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during and after the outbreak were included in this study.


RESULTS
The molecular typing results showed that the outbreak was caused by a single IMRAB strain (genotype 1). On the other hand, seven different genotypes were observed in the pre-, at- and post-outbreak strains tested by REP-PCR. Regarding AP-PCR, three of four at-outbreak IMSAB strains were indistinguishable from the IMRAB profile. Thus, with AP-PCR, only six genotypes were obtained, apart from the IMRAB genotype.


CONCLUSIONS
Under our experimental conditions, REP-PCR had a higher discriminatory power than AP-PCR, with PFGE as reference technique. The REP-PCR technique is a useful and expeditious method for the epidemiologic characterization of A. baumannii nosocomial outbreaks, the results being comparable to those obtained with the PFGE technique.
Bou
G
G
Servicio de Microbiología, Hospital Ramón y Cajal, Madrid, Servicio de Microbiología, Hospital de Bellvitge, CSUB, Barcelona, Spain. bou.german@mayo.edu
Cerveró
G
G
Domínguez
M A
MA
Quereda
C
C
Martínez-Beltrán
J
J
D000150:Acinetobacter / Q000145:classification* / Q000187:drug effects / Q000235:genetics; D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D003428:Cross Infection / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D016172:DNA Fingerprinting / Q000379:methods*; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D016521:Electrophoresis, Gel, Pulsed-Field; D006801:Humans; D015378:Imipenem / Q000494:pharmacology* / Q000627:therapeutic use; D000077731:Meropenem; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D013030:Spain / Q000453:epidemiology; D013845:Thienamycins / Q000494:pharmacology* / Q000627:therapeutic use
D004269:DNA, Bacterial; D013845:Thienamycins; D015378:Imipenem; D000077731:Meropenem