During a 4-month period, 41 isolates of Enterobacter aerogenes were cultured from different specimens from a 14-bed intensive care unit (ICU1). These were obtained from 12 patients out of a total of 187 patients admitted to the ICU. Sixteen E. aerogenes isolates were cultured from another ICU (ICU2) 6 months later. Six non-outbreak-associated strains were included as controls and all the isolates were compared by random amplification of polymorphic DNA (RAPD), with three different 10-mer oligonucleotide primers. The six non-outbreak-associated strains were distinguishable by RAPD with two of the three primers. RAPD fingerprinting with primer AP12h was as discriminatory as the combined results from all three primers and defined 22 different patterns for the 41 isolates from the ICU1. In nine instances, isolates with indistinguishable RAPD patterns were detected in two-to-five patients over a 3–15-day period, suggesting patient-to-patient transmission. During their stay in ICU1, patients harboured one-to-12 distinguishable isolates. Isolates from ICU2 were indistinguishable by RAPD analysis with the three different primers. These findings suggest that the cluster of colonisations and infections in ICU1 was a “false outbreak”, consisting of successive patient-to-patient transmission of different E. aerogenes strains. In contrast, the outbreak on ICU2 probably involved the extensive spread of a single strain.
De ChampsC.,
SauvantM. P.,
ChanalC. Prospective survey of colonization and infection caused by expanded-spectrum-beta-lactamase-producing members of the family Enterobacteriaceae in an intensive care unit. J Clin Microbiol1989; 27:2887–2890
De ChampsC.,
SirotD.,
ChanalC.,
Poupart, M-C, Dumas, M-P, SirotJ. Concomitant dissemination of three extended-spectrum beta-lactamases among different Enterobacteriaceae isolated in a French hospital. J Antimicrob Chemother1991; 27:441–457
EhrhardtA. F.,
SandersC. C.,
ThomsonK.S.,
WatanakunakomC.,
Trujillano-MartinI. Emergence of resistance to imipenem in Enterobacter isolates masquerading as Klebsiella pneumoniae during therapy with imipenem/cilastatin. Clin Infect Dis1993; 17:120–122
ChowJ. W.,
FineM. J.,
ShlaesD. M.Enterobacter bacteremia: clinical features and emergence of antibiotic resistance during therapy. Ann Intern Med1991; 115:585–590
FlynnD. M.,
WeinsteinR. A.,
NathanC.,
GastonM. A.,
KabinsS. A. Patients’ endogenous flora as the source of “nosocomial” Enterobacter in cardiac surgery. J Infect Dis1987; 156:363–368
De ChampsC.,
HenquellC.,
GuelonD.,
SirotD.,
GazuyN.,
SirotJ. Clinical and bacteriological study of nosocomial infections due to Enterobacter aerogenes resistant to imipenem. J Clin Microbiol1993; 31:123–127
MarkowitzS. M.,
SmithS. M.,
WilliamsD. S. Retrospective analysis of plasmid patterns in a study of bum unit outbreaks of infection due to Enterobacter cloacae
. J Infect Dis1983; 148:18–23
HaertlR.,
BandlowG. Epidemiological fingerprinting of Enterobacter cloacae by small-fragment restriction endonuclease analysis and pulsed-field gel electrophoresis of genomic restriction fragments. J Clin Microbiol1993; 31:128–133
WilliamsJ. G. K.,
KubelikA. R.,
LivakK. J.,
RafalskiJ. A.,
TingeyS. V. DNA polymorphisms amplified by arbitrary primers are useful as genetic markers. Nucleic Acids Res1990; 18:6531–6535
OlsonB.,
WeinsteinR. A.,
NathanC.,
KabinsS. A. Broad-spectrum beta-lactam resistance in Enterobacter: emergence during treatment and mechanisms of resistance. J Antimicrob Chemother1983; 11:299–310
ChowJ. W.,
ShlaesD. M. Imipenem resistance associated with the loss of a 40 kDa outer membrane protein in Enterobacter aerogenes
. J Antimicrob Chemother1991; 28:499–504
HopkinsJ. M.,
TownerK. sJ. Enhanced resistance to cefotaxine and imipenem associated with outer membrane protein alterations in Enterobacter aerogenes
. J Antimicrob Chemother1990; 25:49–55