Toxins A and B are known to be the primary virulence factors of Clostridium difficile. Other potential virulence factors have been identified such as binary toxin (actin-specific ADP-ribosyltransferase toxin, or CDT). A retrospective case-control study was performed in order to identify clinical features and risk factors of C. difficile-associated diarrhoea due to binary toxin-producing strains. Each case (a patient with diarrhoea due to binary toxin-producing strain) was compared with two controls (patients with diarrhoea due to a C. difficile strain that did not produce binary toxin) matched for ward and date of hospitalization. cdtA and cdtB genes were screened by PCR. Production of CDT was studied by Western blotting using an antiserum against Ia and Ib from the Clostridium perfringens iota toxin, and the activity of the binary toxin was assessed using an ADPribosyltransferase assay. Twenty-six cases (14 males and 12 females) were identified in 1999 and 2000. Cases and controls did not differ significantly for sex, age, previous administration of antibiotics or frequency of endoscopic examination. Diarrhoea was community-acquired more often in cases than in controls (65 . 4 vs 35 . 7 %, P ¼ 0 . 017) and more often represented the cause of hospitalization (61 . 5 vs 26 . 2 %, P ¼ 0 . 003). Moreover, diarrhoea in cases was more frequently associated with abdominal pain (63 . 6 vs 39 . 4 %, P ¼ 0 . 07) and with liquid stools (76 . 9 vs 59 . 5 %, P ¼ 0 . 14) than in controls. These results suggest that there could be a correlation between the production of binary toxin and the severity of diarrhoea.

The incidence of CDAD is low in our hospital, and cross-infection is limited. These results also suggest that strains with binary toxin might be more virulent.

One hundred twenty CTX-M-15-producing Escherichia coli strains isolated in 10 different hospitals from Paris (France), in the Hospital Charles Nicolle in Tunis (Tunisia), and in the Pasteur Institute in Bangui, Central African Republic (CAR), between 2000 and 2004 were studied. Eighty isolates, recovered from the three countries, were clonally related by repetitive extragenic palindromic PCR and pulsed-field gel electrophoresis. Various resistance profiles were identified among these clonal strains. After conjugation or electroporation of plasmids from E. coli strains representative of each profile and each geographic region, we observed seven resistance profiles in the recipient strains. Incompatibility typing showed that all the plasmids transferred from the clonal strains studied, except one, belonged to the incompatibility group FII. They all shared a multidrug resistance region (MDR) resembling the MDR region located in pC15-1a, a plasmid associated with an outbreak of a CTX-M-15-producing E. coli strain in Canada. They also shared the common backbone of an apparent mosaic plasmid, including several features present in pC15-1a and in pRSB107, a plasmid isolated from a sewage treatment plant. This study suggests that although the plasmid-borne bla CTX-M-15 gene could be transferred horizontally, its dissemination between France, Tunisia, and CAR was due primarily to its residence in an E. coli clone with a strong propensity for dissemination.

A total of 198 nonrepetitive clinical strains of Clostridium difficile isolated from different French hospitals in 1991 (n ‫؍‬ 100) and 1997 (n ‫؍‬ 98) were screened for decreased susceptibility to fluoroquinolones by plating onto Wilkins-Chalgren agar containing 16 g of ciprofloxacin per ml. The frequency of decreased susceptibility was 7% (14 of 198) and was identical for the years 1991 and 1997. Serogroups C, H, D, A9, and K accounted for five, four, two, one, and one of the resistant strains, respectively, one strain being nontypeable. Arbitrarily primed PCR typing showed that all resistant strains had unique patterns except two serotype C strains, which could not be clearly distinguished. All isolates with decreased susceptibility carried a mutation either in gyrA (eight mutations, amino acid changes Asp713Val in one, Thr823Ile in six, and Ala1183Thr in one) or in gyrB (six mutations, amino acid changes Asp4263Asn in five and Arg4473Leu in one). These changes are similar to those already described in other species except for Asp713Val, which is novel, and Ala1183Thr, which is exceptional. Attempts to detect the topoisomerase IV parC gene by PCR amplification with universal parC primers or DNA-DNA hybridization under low-stringency conditions were unsuccessful. The susceptibilities of all resistant strains to ciprofloxacin and ethidium bromide were not affected by the addition of reserpine at 20 g/ml. In conclusion, decreased susceptibility to fluoroquinolones in C. difficile is rare in France and is associated with the occurrence of a gyrA or gyrB mutation.Vancomycin and metronidazole are effective antibiotics for the treatment of Clostridium difficile-associated diarrhea (19,24). However, at least 15% of patients relapse after discontinuation of treatment for poorly understood reasons (23, 24). Other treatments may be more effective in preventing relapses.The in vitro activities against C. difficile of older fluoroquinolones like ciprofloxacin and ofloxacin are poor, but those of some new compounds like moxifloxacin are markedly increased (1,3,17,25). Thus, these drugs could become therapeutic alternatives for the treatment of C. difficile-associated diarrhea. Decreased susceptibility to fluoroquinolones in C. difficile has already been described (2, 3, 13, 26), but the data reported are controversial and the genetic mechanisms involved are poorly understood.In the present work, 198 French clinical strains of C. difficile were screened for decreased susceptibility to fluoroquinolones, and the genetic basis of this phenomenon was investigated. MATERIALS AND METHODSBacterial strains. Reference strain ATCC 9689 and 198 nonrepetitive clinical isolates obtained in 1991 (n ϭ 100) and 1997 (n ϭ 98) from 36 French hospitals (7) were studied. Serotyping of the strains had been performed in a previous study (7) by the method of Delmée et al. (12). Serogroups A, C, D, F, G, H, and K accounted for 9, 22, 8, 1, 4, 19, and 14% of the strains, respectively, and 23% of the strains were untypeable. Strains were cultured in...