Michel Delmée

Virulence of ten serogroups of Clostridium difficile in hamsters.

A slide agglutination technique identifying 10 serogroups of Clostridium difficile (A,B,C,D,F,G,H,I,K and X) has been described previously. In this study, we have used the hamster to compare the ability of the 10 serogroup reference strains to colonise and produce disease. Groups of four hamsters were each given a single intraperitoneal injection of either clindamycin or cefoxitin, and an oral challenge dose of C. difficile. The time taken to establish faecal colonisation and the length of survival after colonisation were monitored. All hamsters treated with cefoxitin became colonised by day 3 and those challenged with the cytotoxigenic strains of serogroups A,C,H and K developed colitis and died. Among those challenged with the non-toxigenic strains of groups B,D,I and X and the toxigenic strains of groups F and G, faecal colonisation was established without signs of disease. This demonstrates that there are differences in virulence even among toxigenic strains of C. difficile. The same phenomenon was observed after treatment with clindamycin but the pattern of colonisation was quite different with some strains. In the hamsters challenged with toxigenic strains of groups C and K and non-toxigenic strains of groups D and I, which are highly resistant to clindamycin, the response was the same as with cefoxitin. The results were different with strains which were susceptible to clindamycin. Some animals became colonised much later than those treated with cefoxitin but the mortality was similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and prevalence of antimicrobial resistance among gram-negative isolates in intensive care units (ICU) in Belgian hospitals between 1996 and 1999.

Abstract Objective : to assess the distribution and prevalence of resistance rates among Gram-negative isolates in Belgian intensive care units (ICUs) between 1996 and 1999. Methods : During 1996-1997 and 1998-1999, over a total period of 10 and 9 months respectively, members of the NPRS Belgian Study group collected, on clinical indications, 3029 consecutive initial isolates of Gramnegative bacteria from patients admitted to 26 Belgian hospitals and performed minimal inhibitory concentration (MIC) determinations by means of the E-test. Breakpoints were defined according to the criteria of the NCCLS. Results : The overall distribution of bacterial species was, in decreasing order of frequency : Pseudomonas aeruginosa >E. coli >E. aerogenes >K. pneumoniae >P. mirabilis >S. marcescens >E. cloacae >K. oxytoca >M. morganii >Stenotrophomonas maltophilia >Acinetobacter spp. All together these species and genera constituted about 90% of all isolates. The frequency of resistance for all the initial Gram-negative isolates in 1998-9 were : amoxicillin-clavulanic acid 60%, piperacillin 31%, piperacillin-tazobactam 20%, cefuroxime 58%, ceftriaxone 31%, ceftazidime 17%, aztreonam 23%, cefepime 10%, imipenem 13%, gentamicin 12%, amikacin 12% and ciprofloxacin 21%. Apart for an increase in multiple drug resistance among P. aeruginosa isolates, no significant trends were observed neither in species distribution nor in the overall prevalence of antimicrobial resistance among Gramnegative isolates from Belgian ICUs between 1996-7 and 1998-9. Conclusions : Among Gram-negative isolates in Belgian ICUs, a very high frequency of resistance was seen to amoxicillin-clavulanic acid and cefuroxime, and rather high frequencies of resistance to piperacillin, ceftriaxone and aztreonam. Taking into account the species distribution and the prevalence of resistance, cefepime, imipenem, amikacin and gentamicin appeared generally suitable for empirical therapeutic use in severe ICU-acquired Gram-negative infections in Belgium. However, the therapeutic strategy should be adapted according to the local ecology of resistance.

A multicentre survey of antimicrobial resistance in gram-negative isolates from Belgian intensive care units in 1994-1995. Belgian Multicenter ICU Study Group.

The aim of this prospective study was to evaluate the distribution and antibiotic susceptibility of aerobic Gram-negative bacilli isolated from patients in intensive care units in 18 Belgian hospitals during 1994 and 1995. A standardised method (i.e. the E-test) was used in each center to determine the minimum inhibitory concentrations of 12 major antibiotics against 1435 consecutive, non duplicate, Gram-negative isolates (close to 100 strains per hospital) during a period of 6 months. The isolates were mainly isolated from the lower respiratory tract (57.4%), urinary tract (17.7%), pus (7.9%) or blood specimens (7.8%) and were mainly P.aeruginosa (20.3%), E.coli (19.9%) and Enterobacter spp. (12.6%). Overall inducible Enterobacteriaceae (IE) accounted for 29.8% of all isolates, and E.aerogenes was the most frequently isolated species in this group (27.6%). The overall susceptibility rate (all species confounded) was about 70% to piperacillin, ticarcillin-clavulanic acid and ceftriaxone, 78% to piperacillin-tazobactam; 87% both to ceftazidime and to ciprofloxacin; and 90% to imipenem. Widespread resistance was observed in several IE species to third generation cephalosporins, broad-spectrum penicillins and to ciprofloxacin. By contrast, imipenem and the aminoglycosides still retained excellent activity against most multiresistant species. Although there were wide differences between hospitals in the frequencies of resistance to most antibiotics, these were not related to the types (general vs. university) of hospitals or to the number of beds. Some variations were however observed in the distribution of bacterial species: the prevalence of inducible Enterobacteriaceae was significantly higher in university than in general hospitals and in hospitals located in Brussels and in Wallonia than in the Flanders. Overall few trends in resistance rates were observed in comparison to a similar survey performed in 1991.

Treatment of Clostridium difficile colitis. Summary of a round table held in Brussels on March, 3rd, 1994.

Due to the growing incidence and the severity of infections due to vancomycin resistant enterococci, it is now recommended to treat mild to moderate cases of Clostridium difficile-associated diarrhoea with metronidazole while maintaining the use of oral vancomycin in serious or life-threatening colitis. Clostridium difficile is a common cause of diarrhoea after antibiotic therapy and induces a spectrum of diseases ranging from mild diarrhoea to pseudomembranous colitis (PMC). It is considered to be the first cause of diarrhoea occurring among hospitalized patients (1).