Evaluation of the DiversiLab system for detection of hospital outbreaks of infections by different bacterial species

Abstract

Many bacterial typing methods are specific for one species only, time-consuming, or poorly reproducible. DiversiLab (DL; bioMérieux) potentially overcomes these limitations. In this study, we evaluated the DL system for the identification of hospital outbreaks of a number bacterial species. Appropriately typed clinical isolates were tested with DL. DL typing agreed with pulsed-field gel electrophoresis (PFGE) for Acinetobacter (n = 26) and Stenotrophomonas maltophilia (n = 13) isolates. With two exceptions, DL typing of Klebsiella isolates (n = 23) also correlated with PFGE, and in addition, PFGE-nontypeable (PFGE-NT) isolates could be typed. Enterobacter (n = 28) results also correlated with PFGE results; also, PFGE-NT isolates could be clustered. In a larger study (n = 270), a cluster of 30 isolates was observed that could be subdivided by PFGE. The results for Escherichia coli (n = 38) correlated less well with an experimental multilocus variable number of tandem repeats analysis (MLVA) scheme. Pseudomonas aeruginosa (n = 52) showed only a limited number of amplification products for most isolates. When multiple Pseudomonas isolates were assigned to a single type in DL, all except one showed multiple multilocus sequence types. Methicillin-resistant Staphylococcus aureus generally also showed a limited number of amplification products. Isolates that belonged to different outbreaks by other typing methods, including PFGE, spa typing, and MLVA, were grouped together in a number of cases. For Enterococcus faecium, the limited variability of the amplification products obtained made interpretation difficult and correlation with MLVA and esp gene typing was poor. All of the results are reflected in Simpson's index of diversity and adjusted Rand's and Wallace's coefficients. DL is a useful tool to help identify hospital outbreaks of Acinetobacter spp., S. maltophilia, the Enterobacter cloacae complex, Klebsiella spp., and, to a somewhat lesser extent, E. coli. In our study, DL was inadequate for P. aeruginosa, E. faecium, and MRSA. However, it should be noted that for the identification of outbreaks, epidemiological data should be combined with typing results.

FIG. 1.

DL results for E. cloacae complex isolates. The interpretation of the data is given in the cluster number column. The PFGE outbreak type is also indicated.

FIG. 2.

DL results for Klebsiella sp. isolates. The interpretation of the data is given in the cluster number column. The PFGE outbreak type is also indicated.

FIG. 3.

DL results for E. coli isolates. The interpretation of the data is given in the cluster number column. The MLVA outbreak type, including the allele numbers, is also indicated.

FIG. 4.

DL results for P. aeruginosa isolates from CF patients in relation to the STs. The circles indicate different STs (indicated by numbers). The size of each circle reflects the number of isolates. The different types discerned by DL are indicated as follows: light blue, cluster type 001; yellow, cluster type 002; brown, cluster type 003; dark blue, cluster type 004; purple, cluster type 005; pink, cluster type 006; green, closely related cluster types 025 and 026; red, cluster type 033; white, all other cluster types.

FIG. 5.

DL results for Acinetobacter sp. isolates. The interpretation of the data is given in the cluster number column. The PFGE outbreak type is also indicated.

FIG. 6.

DL results for S. maltophilia isolates. The interpretation of the data is given in the cluster number column. The PFGE outbreak type is also indicated.

FIG. 7.

DL results for E. faecium isolates. The interpretation of the data is given in the cluster number column. The types based on MLVA and esp gene analysis and the historic Department of Hospital Hygiene classification are also indicated.

FIG. 8.

DL results for MRSA isolates. The interpretation of the data is given in the cluster number column. The PFGE type, MLVA type, spa type, and historic Department of Hospital Hygiene (HH) classification (O, outbreak with number of outbreak; U, unexpected) are also given.