Population-based laboratory assessment of the burden of community-onset bloodstream infection in Victoria, Canada.

Although community-onset bloodstream infection (BSI) is recognized as a major cause of morbidity and mortality, its epidemiology has not been well defined in non-selected populations. We conducted population-based laboratory surveillance in the Victoria area, Canada during 1998-2005 in order to determine the burden associated with community-onset BSI. A total of 2785 episodes were identified for an overall annual incidence of 101·2/100,000. Males and the very young and the elderly were at highest risk. Overall 1980 (71%) episodes resulted in hospital admission for a median length of stay of 8 days; the total days of acute hospitalization associated with community-onset BSI was 28 442 days or 1034 days/100,000 population per year. The in-hospital case-fatality rate was 13%. Community-onset BSI is associated with a major burden of illness. These data support ongoing and future preventative and research efforts aimed at reducing the major impact of these infections.

Disk diffusion versus broth microdilution susceptibility testing of Haemophilus species and Moraxella catarrhalis using seven oral antimicrobial agents: application of updated susceptibility guidelines of the National Committee for Clinical Laboratory Standards.

Susceptibility testing of Haemophilus species and Moraxella catarrhalis is medium and inoculum dependent. Seven oral agents, ampicillin, amoxicillin-clavulanic acid, cefaclor, loracarbef, cefuroxime-axetil, cefixime, and erythromycin, were tested against 400 beta-lactamase-positive and -negative clinically significant respiratory strains of Haemophilus species and 100 strains of M. catarrhalis. Sources of the strains included teaching and regional hospitals and a private laboratory. All strains were tested by broth microdilution and disk diffusion in haemophilus test medium for Haemophilus species and Mueller-Hinton broth and agar for M. catarrhalis. Appropriate National Committee for Clinical Laboratory Standards (NCCLS) standards were followed. For Haemophilus species, by disk diffusion and broth microdilution, respectively, 27 and 27% of strains were resistant to ampicillin, 37 and 5% were resistant to erythromycin, 3 and 0.5% were resistant to cefaclor, 2 and 0.5% were resistant to loracarbef, and 0% were resistant to cefuroxime-axetil, cefixime, and amoxicillin-clavulanic acid. beta-Lactamase-negative ampicillin-resistant strains were not observed. Of M. catarrhalis strains, 56% were resistant to ampicillin by disk diffusion and 95% were resistant by broth microdilution. This species was susceptible to all other agents tested by either method. The disagreements between disk diffusion results and MICs for cefaclor, ampicillin, cefuroxime, and loracarbef that occurred with use of the 1990 NCCLS tables were resolved when the 1992 NCCLS tables were used.

Comparison of BACTEC Plus 26 and 27 media with and without fastidious organism supplement with conventional methods for culture of sterile body fluids.

We compared the BACTEC Plus 26/27 culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) with and without fastidious organism supplement with conventional centrifugation preparation and plating for the recovery and speed of detection of microorganisms. A total of 1,101 sterile body fluid specimens were collected and processed at five hospital laboratories, yielding 234 (21%) positive cultures. Of the 176 isolates considered clinically significant, 133 (76%) were recovered by both the BACTEC system and conventional culture, while 28 (16% [P < 0.005]) were recovered by BACTEC only and 11 (6%) were recovered by conventional culture alone. There were no statistically significant differences in the speed of detection of microbial growth. It was found that BACTEC, with or without the addition of fastidious organism supplement, exhibited improved sensitivity for the recovery of microorganisms, including fastidious bacteria.

Epidemiology of infections with Pseudomonas aeruginosa in burn patients: the role of hydrotherapy.

Pseudomonas aeruginosa remains a cause of serious wound infection and mortality in burn patients. By means of restriction fragment length polymorphism analysis and a DNA probe for the pilin gene of Pseudomonas, a lethal strain of nosocomial P. aeruginosa was identified as the cause of an outbreak of wound infections among burn patients. Environmental surveys suggested an association of the outbreak with hydrotherapy provided to many patients in a common facility. In a trial of burn wound care without hydrotherapy, overall mortality was reduced significantly, mortality associated with pseudomonas sepsis was eliminated, and the strain of P. aeruginosa associated with earlier mortality was eradicated. Moreover, fewer nosocomial pseudomonas infections, lower levels of pseudomonas resistance to aminoglycoside antibiotics, significantly fewer pseudomonas infections of skin graft donor sites, and later appearance of Pseodomonas species in burn patients were found during the period when hydrotherapy was not used.

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.

Epidemiological studies of nosocomial infections with Pseudomonas aeruginosa using a DNA probe.

A DNA probe encoding the Pseudomonas aeruginosa pilin gene has been developed in the authors' laboratory and has been shown to be a useful epidemiological tool. In the present study this technology, together with other typing methods, has been used to define relatedness and possible transmission routes of P aeruginosa strains isolated in several hospital wards. Clusters of P aeruginosa infections, suspected to be the result of nosocomial transmission, developed in a general intensive care unit (ICU) and a neurosurgical ward/ICU, as well as in a burn unit, were studied using antibiograms, lipopolysaccharide-serotyping, and gene probe analysis. Results of these studies demonstrated that each of the general and neurosurgical ICU isolates were different, making nosocomial transmission very unlikely. However, within the burn unit, patient isolates had identical profiles, suggesting that spread between patients was occurring or that a common source of infection was present. Changes in infection control measures within the unit were introduced and may have contributed to eradication of the outbreak. DNA probe studies were valuable in clarifying epidemiological relatedness of isolates that was not evident with the other typing strategies and identified a possible burn-associated strain.

Comparison of a DNA probe with culture for detecting Chlamydia trachomatis directly from genital specimens.

A study was conducted to compare results between culture methods and the Gen-Probe (Gen-Probe Inc. San Diego, California) chemiluminescent technique of nucleic acid hybridization to identify Chlamydia trachomatis from genital specimens from 117 females and 70 males. Specimens collected from sexually transmitted diseases (STD) and infertility clinics were randomized as to whether probe or culture swabs were collected first. The Gen-Probe demonstrated a sensitivity of 83% and a specificity of 75% in the female population and a sensitivity of 68% and a specificity of 75% in the male population when compared to the reference culture method using cycloheximide-treated McCoy cells. Gen-Probe had an overall sensitivity of 74% and specificity of 75% when the two groups were combined. Chlamydiazyme (Abbott Labs) results were obtained on 135 specimens; 90 of which correlated with probe and culture. The remaining 45 specimens had varying combinations of probe, culture and Chlamydiazyme results. MicroTrak (Syva) was done on 49 specimens; 35 of which correlated with probe and culture. The remaining 14 specimens had varying combinations of probe, culture and MicroTrak results. The apparent lack of sensitivity of the DNA probe is a major drawback of this system.