Dépistage des entérocoques résistants aux glycopeptides: six ans d'étude dans trois services de réanimation au CHU de Montpellier

[Glycopeptide-resistant enterococci carriage: Are actual isolation and identification techniques sufficient?]

The monitoring of infection by glycopeptide-resistant enterococci (GRE) is one of the main elements of hospital hygiene policy. It involves systematic rectal swabs in clinics at risk (asymptomatic carriage).

AIM

We compare two GRE screening methods and evaluate a new kit associating multiplex PCR and hybridization (Génotype(®) Enterococcus, Hain Lifescience) on a panel of 448 samples collected over a 4-month period.

PATIENTS AND METHODS

The first method is based on direct inoculation of the sample; the second one involves a preliminary enrichment phase followed by molecular diagnosis allowing the identification of species of enterococci as well as glycopeptide resistance genes.

RESULTS

All the resistant strains were isolated using the enrichment technique. The incidence of GRE (VanA) carriage was 0,55% (two out of 362 patients, two out of 448 isolates) with two Enterococcus faecium VanA. Six Enterococcus gallinarum VanC1 and two Enterococcus casseliflavus VanC2/C3 were also isolated and identified. The main clinics concerned are intensive care and hematology. The two patients with E. faecium VanA had been previously given glycopeptides for 10 days. For three strains, the molecular method allowed to correct prior erroneous results based on rapid identification (RapidID32Strep V2.0).

CONCLUSION

The method using direct samples inoculation underestimates real incidence of GRE carriage. The performances of Génotype(®) Enterococcus molecular method, evaluated for other parameters using reference strains and DNA sequencing, offer new possibilities applicable to routine laboratory.

[Glycopeptide-resistant Enterococcus outbreak in an ICU with simultaneous circulation of two different clones]

AIM OF THE STUDY

To describe specific difficulties to control a glycopeptide-resistant Enterococcus (GRE) outbreak occurring in an intensive care unit (ICU) during a regional epidemy.

PATIENTS AND METHODS

Following identification of a GRE clinical isolate in ICU, systematic screening was performed on admission and then weekly, by anal swabs. GRE carriers were isolated according to two processes: first (week [W] 2-W8), cohorting of carriers in a dedicated sector of the ICU, with dedicated HCW; this required closing four of the 16 ICU beds. Second (W8-W29), a specific unit was created outside the ICU. VanA-genotypes and pulsed-field gel electrophoresis (PFGE) profiles were analyzed.

RESULTS

During the first outbreak period (102 rectal swabs), two patients were found colonized at admission: the index case transferred from Nancy hospital, carrier of the Nancy epidemy PFGE profile strain, and one patient from the haemodialysis unit, carrier of a GRE strain presenting a different PFGE profile called the Thionville strain. Seven patients were newly identified as GRE colonized (2 by the Nancy strain and 5 by the Thionville strain). Defective running of the ICU was noted. During the second period (442 samples), six ICU patients were found colonized, including four at admission. No other case was identified in 16 weeks. Outbreak extension to other hospital units was checked at W19. The Thionville strain was not found in other regional hospitals.

CONCLUSION

ICUs concentrate GRE colonization risk. This study demonstrates interest of PFGE. These low virulence bacteria have few direct pathological consequences, but they cause organizational problems in ICUs.