VEB-1 Extended-spectrum beta-lactamase-producing Acinetobacter baumannii, France

Abstract

VEB-1 extended-spectrum beta-lactamase-producing Acinetobacter baumannii was responsible for an outbreak in hospitals in France. A national alert was triggered in September 2003 when 4 hospitals reported clusters of A. baumannii infection with similar susceptibility profiles. Case definitions and laboratory guidelines were disseminated, and prospective surveillance was implemented; strains were sent to a single laboratory for characterization and typing. From April 2003 through June 2004, 53 hospitals reported 290 cases of A. baumannii infection or colonization; 275 isolates were bla(VEB-1)-positive and clonally related. Cases were first reported in 5 districts of northern France, then in 10 other districts in 4 regions. Within a region, interhospital spread was associated with patient transfer. In northern France, investigation and control measures led to a reduction of reported cases after January 2004. The national alert enabled early control of new clusters, demonstrating the usefulness of early warning about antimicrobial drug resist.

Figure 1

Number of VEB-1–producing Acinetobacter baumannii cases, by month of report, France, July 2003–May 2004 (N = 255).

Figure 2

A) Hospitals reporting VEB-1–producing Acinetobacter baumannii, by district, France, April 2003–May 2004 (N = 53). Each district is identified with a number (same numbers used in Table 1). B) Interhospital spread in northern France. Circles represent affected hospitals; the sizes are proportional to the number of reported cases.

Figure 3

Extended-spectrum β-lactamase (ESBL) laboratory identification. Usefulness of double-disk synergy test with bla_VEB-1-positive Acinetobacter baumannii strain on Mueller-Hinton agar plates with clavulanate as inhibitor. The disks tested contained ticarcillin + clavulanate (TCC), amoxicillin + clavulanate (AMC), moxalactam (MOX), ceftazidime (CAZ), and cefepime (FEP). A) Standard disk diffusion as recommended by Clinical and Laboratory Standards Institute at 37°C (98°F). B) Standard disk diffusion on cloxacillin-containing Mueller-Hinton plates at 37°C (98°F). Cloxacillin inhibits partially the naturally occurring cephalosporinase (AmpC) from A. baumannii, thus enabling easier detection of possible ESBL phenotypes. C) Standard disk diffusion at 25°C (77°F). D) Standard disk diffusion at 25°C (77°F) when AMC and FEP disks were brought closer. The presence of ESBL was shown by a synergy image, as indicated with the arrows. ESBL presence was best seen on cloxacillin-containing (B) plates or at reduced growth temperature (D).

Figure 4

Digitized pulsed-field gel electrophoresis (PFGE) patterns and phylogenetic tree of 183 VEB-1–producing Acinetobacter baumannii isolates. Half of A. baumannii isolates from the 4 largest hospitals of 2 districts (59 and 62) were randomly selected over the entire epidemic period; all isolates from smaller hospitals or from other districts were included. The PFGE pattern of the A. baumannii AYE reference strain previously described is indicated in brackets (16). ApaI macrorestriction patterns were digitized and analyzed with Taxotron software (Institut Pasteur, Paris, France) to calculate Dice coefficients of correlation and to generate a dendrogram by the unweighted pair-group method using arithmetic averages clustering. The scale indicates the level of pattern similarity. PFGE results were interpreted according to the criteria of Tenover et al. (25). For a given PFGE pattern, the districts, along with the number of times a given PFGE pattern was found, are also indicated.