Molecular epidemiology and antimicrobial susceptibility profiles of methicillin-resistant Staphylococcus aureus blood culture isolates: results of the Quebec Provincial Surveillance Programme.

The objectives of this study were to characterize methicillin-resistant Staphylococcus aureus (MRSA) blood culture isolates and to determine their relative importance in both nosocomial and community-acquired infections. A total of 535 MRSA blood culture isolates were analysed. In vitro susceptibility to 14 agents was determined. The genes nuc, mecA and coding for PVL toxin were identified by PCR. All isolates were characterized by PFGE or spa typing to assess their genomic relationships. Most MRSA isolates were retrieved from nosocomial bloodstream infections (474, 89%) and were of the CMRSA2 genotype. Healthcare-associated (HA)-MRSA bloodstream infections were associated with older age (70-89 years, P = 0·002) and most often secondary to central line infections (P = 0·005). Among MRSA strains associated with community-acquired (CA)-MRSA, 28·8% were isolated in intravenous drug users. CA-MRSA genotypes were more frequently found in young adults (20-39 years, P < 0·0001) with skin/soft tissue as the primary sources of infection (P = 0·006). CMRSA10 genotype was the predominant CA-MRSA strain. All MRSA isolates were susceptible to doxycycline, tigecycline, trimethoprim/sulfamethoxazole and vancomycin. Both the presence of the genes coding for PVL toxin (89·8%) and susceptibility to clindamycin (86·5%) were predictive of CA-MRSA genotypes. Whereas in the USA, HA-MRSA have been replaced by USA300 (CMRSA10) clone as the predominant MRSA strain type in positive blood cultures from hospitalized patients, this phenomenon has not been observed in the province of Quebec.

An unusual case of hepatic abscess.

A case of recurring primary hepatic actinomycosis is reported. A 50-year-old man presented with fever, weight loss and multiple hepatic masses. A diagnosis was obtained by cytological examination of a biopsy sample taken from the largest hepatic mass, which revealed the presence of Actinomyces species. The patient was treated with penicillin for 12 months and did well. Seven years later, he presented with similar symptoms but with a single large liver mass and a pulmonary infiltrate in the right lower lobe. Liver biopsy showed an inflammatory pseudotumour, and lung biopsy showed the presence of Actinomyces species. Again, the patient was treated with penicillin. Five months later, the patient was doing well, and a follow-up computed tomography scan showed partial regression of the hepatic pseudotumour. This case indicates that hepatic actinomycosis can recur several years after an appropriate treatment and stresses the need for careful follow-up in such patients.

Prevalence and antifungal susceptibility of 442 Candida isolates from blood and other normally sterile sites: results of a 2-year (1996 to 1998) multicenter surveillance study in Quebec, Canada.

During a 2-year surveillance program (1996 to 1998) in Quebec, Canada, 442 strains of Candida species were isolated from 415 patients in 51 hospitals. The distribution of species was as follows: Candida albicans, 54%; C. glabrata, 15%; C. parapsilosis, 12%; C. tropicalis, 9%; C. lusitaniae, 3%; C. krusei, 3%; and Candida spp., 3%. These data, compared to those of a 1985 survey, indicate variations in species distribution, with the proportions of C. glabrata and C. parapsilosis increasing by 9 and 4%, respectively, and those of C. albicans and C. tropicalis decreasing by 10 and 7%, respectively. However, these differences are statistically significant for C. glabrata and C. tropicalis only. MICs of amphotericin B were > or =4 microg/ml for 3% of isolates, all of which were non-C. albicans species. Three percent of C. albicans isolates were resistant to flucytosine (> or =32 microg/ml). Resistance to itraconazole (> or =1 microg/ml) and fluconazole (> or =64 microg/ml) was observed, respectively, in 1 and 1% of C. albicans, 14 and 9% of C. glabrata, 5 and 0% of C. tropicalis, and 0% of C. parapsilosis and C. lusitaniae isolates. Clinical data were obtained for 343 patients. The overall crude mortality rate was 38%, reflecting the multiple serious underlying illnesses found in these patients. Bloodstream infections were documented for 249 patients (73%). Overall, systemic triazoles had been administered to 10% of patients before the onset of candidiasis. The frequency of isolation of non-C. albicans species was significantly higher in this group of patients. Overall, only two C. albicans isolates were found to be resistant to fluconazole. These were obtained from an AIDS patient and a leukemia patient, both of whom had a history of previous exposure to fluconazole. At present, it appears that resistance to fluconazole in Quebec is rare and is restricted to patients with prior prolonged azole treatment.

Epidemiology of enterococcal bacteremia in a referral center for hepatobiliary diseases.

BACKGROUND: Enterococcus faecium (EFM) and Enterococcus faecalis (EFL) account for most infections which predominantly originate in the abdomen or the urinary tract. The objectives of this study were to compare the risk factors associated with EFM and EFL bacteremia Patients and Method: Retrospective study of 64 EFL and 27 EFM bacteremia cases that occurred between January 1993 and December 1996 in a referral center for hepatobiliary diseases. RESULTS: Univariate predictors of EFM bacteremia, compared to EFL, were an orthoptic liver transplantation (OLT), use of steroids, admission in the hepatology service, a central vascular catheter and an abdominal source. Forward regression models identified OLT as the only independent risk factor for EFM bacteremia (odds ratio, OR = 4.320; p = 0.0064), and septic shock as the only predictor of a fatal enterococcal bacteremia (OR = 13.152; p = 0.0003). Molecular typing of EFM isolates identified four small nosocomial clusters (of two to seven patients each) of EFM bacteremia, involving primarily patients admitted to the intensive care unit or on the hepatology ward. CONCLUSION: Strategies are needed to prevent enterococcal bacteremia in patients with severe liver disease, especially those undergoing OLT.

Trends in antimicrobial resistance among clinical isolates of the Bacteroides fragilis group from 1992 to 1997 in Montreal, Canada.

The objective of the present study was to analyze the susceptibility profiles of 911 clinical strains of the Bacteroides fragilis group isolated from 1992 to 1997 in our institution in order to monitor susceptibility changes over time. Whereas the rates of resistance to metronidazole, imipenem, piperacillin-tazobactam, ticarcillin-clavulanic acid, penicillin, piperacillin, and cefoxitin remained essentially unchanged, there was a significant increase in the rates of resistance to clindamycin, which rose from 8.2% in 1992 to 19.7% in 1997 (P < 0.0004).

Multicenter evaluation of the fully automated COBAS AMPLICOR PCR test for detection of Chlamydia trachomatis in urogenital specimens.

The fully automated COBAS AMPLICOR CT/NG test for the detection of Chlamydia trachomatis was evaluated in a multicenter trial. Test performance was evaluated for 2,014 endocervical swab and 1,278 urine specimens obtained from women and for 373 urethral swab and 254 urine specimens obtained from men. Culture served as the reference test. Culture-negative, COBAS AMPLICOR-positive specimens that tested positive in a confirmatory PCR test for an alternative target sequence within the C. trachomatis major outer membrane protein gene were resolved as true positives. The overall prevalence of chlamydia was 4.3% in cervical swabs and 11.0% in urethral swabs from men. When the results for each specimen type were considered separately, the resolved sensitivities were 96.5% (83 of 86) for endocervical swab specimens, 95.1% (39 of 41) for urine specimens from women, 100.0% (41 of 41) for urethral swab specimens from men, and 94.4% (17 of 18) for urine specimens from men; the resolved specificities were 99.4% (1,912 of 1,924) for endocervical swab specimens, 99.8% (1,204 of 1,207) for urine specimens from women, 98. 5% (325 of 330) for urethral swab specimens from men, and 100.0% (236 of 236) for urine specimens from men. For the subset of patients from whom both swab and urine specimens were collected, the combined results for both specimen types were used to identify all infected patients. Using these combined reslts as criteria, the resolved sensitivities for the COBAS AMPLICOR test were 82.6% (38 of 46) for endocervical swab specimens, 84.4% (38 of 45) for urine specimens from women, 84.2% (16 of 19) for urethral swab specimens from men, and 89.5% (17 of 19) for urine specimens from men. In comparison, the sensitivity of culture was only 56.5% (26 of 46) for endocervical specimens and 63.2% (12 of 19) for urethral specimens from men. The internal control provided in the COBAS AMPLICOR test revealed that 2.9% of specimens were inhibitory when they were initially tested. Nevertheless, valid results were obtained for 99. 1% of specimens because 68.7% of the inhibitory specimens were not inhibitory when a second aliquot of the original sample was tested. Two additional COBAS AMPLICOR-positive specimens were detected by retesting inhibitory specimens. The COBAS AMPLICOR CT/NG test for the detection of C. trachomatis exhibited equally high sensitivities and specificities with both urogenital swab and urine specimens and, thus, is well-suited for use in screening.

A complication of BCG vaccine: A case of localized cutaneous abscess due to Mycobacterium bovis.

The attenuated bacille Calmette-Guérin (BCG) vaccine is administered to prevent tuberculosis. Complications of vaccination are uncommon. A case of cutaneous abscess due to BCG is presented in a 24-year-old woman. The abscess developed at the inoculation site four weeks after vaccination. Routine Gram stain and bacterial cultures of the pus were negative. The auramine stain was positive. Mycobacterial cultures were positive after 14 and 18 days, using the BACTEC 12B bottle and Löwenstein-Jensen media, respectively. The mycobacteria were identified as Mycobacterium bovis, vaccinal strain by high-performance liquid chromatography and DNA probe assays.

Risk factors for early recurrent Clostridium difficile-associated diarrhea.

Recurrence is a common sequela of Clostridium difficile-associated diarrhea (CDD) and may increase morbidity, costs, and treatment-related antimicrobial resistance. Because recurrent CDD (RCDD) frequently occurs very soon after an initial episode, our goal was to determine the risk factors for early RCDD (occurring < or = 45 days after the initial episode). We conducted a case-control study, comparing 13 patients with early RCDD (case patients) with 46 patients who had only one CDD episode (control patients) at Centre Hospitalier Angrignon (Québec) during January 1993 through November 1994. Risk factors for early RCDD included a history of chronic renal insufficiency, a white blood cell count of > or = 15 x 10(3)/mm3, and community-acquired diarrhea with the first CDD episode. For seven of eight case patients, C. difficile strains from the first and second CDD episodes were identical, suggesting that relapse is more common than reinfection. These results suggest that treatments should be directed at preventing relapses in patients at high risk for early RCDD.

Multicenter evaluation of the COBAS AMPLICOR HCV assay, an integrated PCR system for rapid detection of hepatitis C virus RNA in the diagnostic laboratory.

The benefits shown by the recent introduction of PCR for the in vitro diagnosis of hepatitis C virus (HCV) infection has prompted the development of standardized, ready-to-use assays that can be implemented in routine clinical laboratories. We have evaluated the clinical performance of COBAS AMPLICOR HCV (COBAS), the first instrument system that allows the automation of HCV RNA amplification and detection, to determine its performance in the routine laboratory setting. More than 2,000 specimens collected at five centers were analyzed in parallel by the COBAS and the manual AMPLICOR HCV (AMPLICOR) tests, and the results were compared with the results for biochemical and serological markers of HCV. In this study the two PCR systems showed the same accuracy, with a concordance rate of 99.8%. As expected, the correlation between serology and PCR was not absolute because the presence of anti-HCV antibodies may be associated with a latent or past infection. On the other hand, if the presence of confirmed anti-HCV antibodies and elevated alanine aminotransferase levels are taken as the "gold standard," indicating an active, ongoing infection, the COBAS and AMPLICOR tests show high and comparable sensitivities (100%) and specificities (98%), with positive and negative predictive values of 100 and 97%, respectively. During the study no false-positive reactions were detected. The use of an internal control allowed the identification of inhibitory substances that prevented amplification for 0.3 and 0.4% of samples tested by the COBAS and AMPLICOR tests, respectively. Compared to the manual system, the COBAS system allowed a significant reduction of hands-on time and could improve the overall laboratory work flow. In conclusion, these results support the use of the COBAS and AMPLICOR tests for the molecular diagnosis of active HCV infections.

Update on Pan-American activities in the field of anaerobes: Canada.

During the past 15 years, important contributions have been made to the field of anaerobes in Canada. Studies on the importance of the intestinal flora as a source of vitamin K for humans, investigations of the mechanisms of synergy in polymicrobial infections, and extensive research on the field of immunocompetence of surgical patients have provided interesting and valuable information. Several clinical and epidemiological studies of anaerobic infections have been carried out. Rapid methods have been developed for the identification and susceptibility testing of clinical isolates. National and regional surveys have been conducted on the susceptibility patterns of the Bacteroides fragilis group. Studies on the mechanism of action of metronidazole and on the mechanisms of resistance of Bacteroides species have also been carried out. The Canadian Infectious. Disease Society has published position papers on therapy with cefotetan, ceftizoxime, and imipenem and on antimicrobial prophylaxis in surgical patients.

Clindamycin resistance in the Bacteroides fragilis group: association with hospital-acquired infections.

A retrospective study was conducted to assess the relationships between clindamycin resistance in members of the Bacteroides fragilis group, previous antimicrobial therapy, and the context for the development of infection, whether in the community or during hospitalization. Eighty-five clindamycin-resistant clinical strains (one isolate per patient) isolated from January 1988 to October 1994 were matched (one to one) with clindamycin-susceptible isolates recovered during the same period, and the charts of the patients from whom the isolates were recovered were reviewed retrospectively. Of the clindamycin-resistant strains, 65% were recovered from patients with hospital-acquired infections compared with 40% of the clindamycin-susceptible strains (odds ratio [OR], 2.75; 95% confidence interval [CI], 1.41-5.38; P = .002). Prior antimicrobial therapy for > or = 48 hours was also associated with clindamycin resistance (OR, 2.33; 95% CI, 1.16-4.70; P = .02). However, clindamycin resistance remained associated with hospital-acquired infections independent of prior antimicrobial therapy (Mantel-Haenszel weighted average OR, 2.22; 95% CI, 1.03-4.89; P = .04). Clinicians should consider the risks for clindamycin resistance when treating hospital-acquired infections caused by members of the B. fragilis group.

Meningitis in a Canadian adult due to high level penicillin-resistant, cefotaxime-intermediate Streptococcus pneumoniae.

Invasive penicillin-resistant pneumococcal (PRSP) infections are increasing worldwide. In Canada, the incidence of penicillin resistance among Streptococcus pneumoniae isolates is estimated at greater than 6%. In Quebec, only one case of PRSP meningitis has been reported and involved an infant. An adult patient is described who presented with meningitis caused by high level penicillin-resistant, cefotaxime-intermediate S pneumoniae.

Survey of Bacteroides fragilis group susceptibility patterns in Canada.

The in vitro activities of penicillin, clindamycin, chloramphenicol, metronidazole, piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillin-clavulanate, ampicillin-sulbactam, cefoxitin, ceftizoxime, cefotetan, moxalactam, and imipenem against 348 Bacteroides fragilis group isolates collected from six Canadian cities during 1990 were determined by the National Committee for Clinical Laboratory Standards (NCCLS) agar dilution technique. All isolates were susceptible to chloramphenicol, metronidazole, piperacillin-tazobactam, and imipenem. For the other antibiotics tested, the following resistance rates were observed: penicillin, 97%; clindamycin, 9%; piperacillin, 19%; ticarcillin, 31%; ticarcillin-clavulanate, 0.28%; ampicillin-sulbactam, 0.85%; cefoxitin, 26%; ceftizoxime, 15%; cefotetan, 53%; and moxalactam, 17%. Susceptibility profiles to beta-lactam antibiotics varied among the different species tested: B. fragilis and Bacteroides vulgatus demonstrated lower resistance rates than Bacteroides distasonis and indole-positive Bacteroides thetaiotaomicron and Bacteroides ovatus. Ceftizoxime results should be interpreted cautiously, because the MICs obtained with the recommended NCCLS control strain were lower than expected.

Thiamine deficiency and Wernicke's encephalopathy in AIDS.

Several neuropathological reports in the last 5 years have described brain lesions characteristic of Wernicke's Encephalopathy in patients with AIDS. Using the erythrocyte transketolase activation assay, we now report biochemical evidence of thiamine deficiency in 9/39 (23%) of patients with AIDS or AIDS-related complex. In no cases was there history of alcohol abuse nor were there clinical signs of Wernicke's Encephalopathy. Thiamine deficiency in these patients most likely results from the cachexia and catabolic state characteristic of AIDS. In view of (i) the confirmed neuropathological evidence of Wernicke's Encephalopathy in AIDS patients, (ii) the significant thiamine deficiency in these patients and (iii) the difficulties of clinical diagnosis of Wernicke's Encephalopathy, it is recommended that dietary thiamine supplementation be initiated in all newly diagnosed cases of AIDS or AIDS-related complex.

Usefulness of semi-quantitative cultures in the diagnosis of Clostridium difficile associated disease.

Semi-quantitative stool cultures on CCFA were compared to cytotoxic assays for the diagnosis of Clostridium difficile associated disease (CAD). There was a significant correlation between the amount of Clostridium difficile growth on CCFA, the presence of cytotoxin and a clinical diagnosis of CAD in the 541 initial stool specimens tested.

Multilaboratory evaluation of an agar diffusion disk susceptibility test for rapidly growing anaerobic bacteria.

A multilaboratory collaborative study was undertaken to determine whether the anaerobic disk diffusion test of Horn et al. could be performed reproducibly and accurately. Tests with nine different antimicrobial disks were evaluated. Reproducibility of the agar diffusion disk method was similar to that of the reference agar dilution test procedure. The anaerobic disk diffusion procedure was found to be a potentially useful method for testing some antimicrobial agents against rapidly growing anaerobes belonging to the Bacteroides fragilis group. These promising results warrant further investigations and validations.

Ghost mycobacteria on Gram stain.

The Gram stain is a key tool in diagnostic microbiology. Its usefulness with respect to mycobacteria is undefined. The neutrality of mycobacteria other than Mycobacterium tuberculosis on Gram staining of various clinical specimens is described.