Human isolates of Staphylococcus caprae: association with bone and joint infections.

Staphylococcus caprae is a coagulase-negative, DNase-positive member of the genus Staphylococcus usually associated with goats, but since 1991 a few laboratories have reported isolating the organism from human clinical specimens. We report on the isolation of 14 strains from human specimens and note that 10 strains were obtained from patients with bone and joint infections. Nine of the 10 infections started with traumatic fractures, and the other was a case of mastoiditis. Seven of these 10 infections were in patients with orthopedic prostheses, which appears to be a risk factor. Three of the 14 strains were from transplant patients. For three of the patients, S. caprae was the only organism isolated. S. caprae may be misidentified because it is not represented in the current MicroScan or Vitek identification systems which are in use in many laboratories, but the organism can be differentiated by a few biochemical tests. S. caprae produces positive results for DNase, pyrrolidonyl aminopeptidase, and acid production from mannitol and maltose; it produces negative results for ornithine decarboxylase and tube coagulase.

Recognition of a Nocardia transvalensis complex by resistance to aminoglycosides, including amikacin, and PCR-restriction fragment length polymorphism analysis.

Amikacin resistance, rare among nocardiae, was observed in 58 clinical isolates of nocardiae. All of these isolates hydrolyzed hypoxanthine, and 75 to 100% utilized citrate, D-galactose, and D-trehalose as sole carbon sources. Based on utilization of I-erythritol, D-glucitol, i-myo-inositol, D-mannitol, and ribitol and susceptibility to amoxicillin-clavulanic acid, the 58 isolates were separable into four groups. One group was negative for I-erythritol and ribitol and included all the isolates belonging to Nocardia asteroides complex antibiogram type IV. The remaining three groups were positive for I-erythritol and ribitol and were grouped within Nocardia transvalensis. The group that included the type strain was designated N. transvalensis sensu stricto, and the other two groups were designated new taxons 1 and 2. PCR-restriction fragment length polymorphism (RFLP) analysis of a 439-bp segment of the 65-kDa heat shock protein gene with XhoI and HinfI produced identical patterns for 53 (91%) and 58 (100%) isolates, respectively, and differentiated them from all other Nocardia taxa. NarI- and HaeIII-derived RFLP patterns clearly differentiated each of the four biochemically defined taxa. These four groups were also distinguishable by using the chromogenic substrates in Dade MicroScan test panels. By high-performance liquid chromatography, these isolates exhibited the same unique mycolic acid-ester elution patterns that differed from those of all other clinically significant nocardiae. Gas-liquid chromatographic analysis of fatty acids also produced similar patterns for all isolates that distinguished them from all other Nocardia taxa, but did not differentiate the four taxa within the complex. We propose the designation N. transvalensis complex for these four groups of nocardiae, pending further genetic evaluation.

Fatty acid characterization of rapidly growing pathogenic aerobic actinomycetes as a means of identification.

The fatty acid compositions of 39 type strains and 529 clinical or reference strains of pathogenic aerobic actinomycetes were analyzed after standardized culture by using the Microbial Identification System (MIS). Library entries for each type strain were created by using the MIS Library Generation Software, and the fatty acid profiles of clinical and reference strains were compared to these library entries. The bacteria separated into two large groups based upon major amounts of branched-chain or of saturated or monounsaturated straight-chain fatty acids. Identification of isolates was possible by using only the type strains for comparison, but fatty acid heterogeneity occurred within most species.

Identification of staphylococci with a self-educating system using fatty acid analysis and biochemical tests.

We characterized all of the 35 aerobic taxa of the genus Staphylococcus by using an objective, self-learning system combining both whole-cell fatty acid (FA) analysis and the results of 35 biochemical tests. Isolates were compared with the type strain for each taxon to generate an FA profile library and a biochemical table of test responses. Isolates were accepted into the system if they had a similarity index of > or = 0.6 for a taxon within the FA profile library and if they were identified as the same taxon by a computer program using a probability matrix constructed from the biochemical data. These stringent criteria led to acceptance of 1,117 strains assigned to legitimate taxa. Additional FA groups were assembled from selected strains that did not meet the inclusion criteria based on the type strains and were added to the system as separate entries. Currently, 1,512 isolates have bee accepted into the system. This approach has resulted in a comprehensive table of biochemical test results and a FA profile library, which together provide a practical system for valid identifications.

Incidence and susceptibility of aerobic Gram-negative bacilli from 20 Canadian intensive care units: 1989-1993.

OBJECTIVE: To assess the prevalence of antibiotic resistance in Canadian intensive care units. DESIGN: The antimicrobial profiles of 1939 Gram-negative bacilli isolated in 20 Canadian intensive care units were analyzed using a custom designed MicroScan panel. SETTING: The majority of the hospitals were tertiary care institutions, but some community hospitals were included. PATIENTS: Adult intensive care unit patients were the sources of isolates. MAIN RESULTS: Pseudomonas aeruginosa was the most frequently isolated microorganism overall, with Escherichia coli the most common initial isolate. Comparison of initial and repeat isolates showed that P aeruginosa readily acquired resistance to all antibiotic classes except the aminoglycosides. Enterobacter aerogenes developed resistance to ciprofloxacin and Enterobacter cloacae demonstrated resistance to all beta-lactam antibiotics except for imipenem on repeat isolation. Other Enterobacteriaceae remained susceptible. Historical comparison with data derived four years previously from 15 of the centres showed increased resistance of P aeruginosa and Acinetobacter species to ciprofloxacin while other susceptibility patterns remained stable. CONCLUSIONS: The prevalence of Gram-negative resistance in Canadian hospitals is less than that reported in surveys done in some other countries, and was relatively stable over four years.

The impact of formulary reservations on drug utilization: a controlled trial.

A controlled trial was conducted in two teaching hospitals (A and B), with similar case mixes to determine the impact of reservations, which were educational in nature, on the utilization of oral ciprofloxacin. Over a two-month period the health records of all the patients who received the drug were reviewed, and information on utilization and demographics of patients receiving the drug was recorded. As well, the number of admissions to the two hospitals over this period were compared. If culture and sensitivity (C & S) results were available, appropriateness was assessed in accordance with criteria for use established at site A; in the absence of C & S information, consensus by two microbiologists was used. Over the two-month period a total of 136 patients received ciprofloxacin at the two institutions. At site A, which had reservations, the number of patients who continued to receive ciprofloxacin upon admission was significantly decreased relative to site B, which did not have reservations (14% vs. 36% respectively, p = .029). As well, when assessed by total number of admissions to the institutions, the number of patients receiving ciprofloxacin at site A was less than site B (1.5% vs. 2.6% respectively, p = .003)). While the utilization was decreased at site A vs. site B, the proportion of patients with therapy deemed to be appropriate was not different between the two sites. Educationally based reservations are an effective formulary tool for optimizing drug utilization.

Staphylococcus lugdunensis endocarditis.

Staphylococcus lugdunensis is a recently described coagulase-negative species which has been associated with human infections, including infective endocarditis. A case of native valve endocarditis caused by this organism is described. The initial laboratory detection of S. lugdunensis is facilitated by a positive test for ornithine decarboxylase. The identification of such isolates should not cause difficulty unless undue reliance is placed upon a small number of tests.

Isolation of Nocardia asteroides from respiratory specimens by using selective buffered charcoal-yeast extract agar.

Nocardiosis is difficult to diagnose clinically and by laboratory methods. A patient presented with disease compatible with pulmonary malignancy, but Nocardia asteroides was isolated on buffered charcoal-yeast extract agar. Investigation revealed that this medium may be a suitable selective primary isolation medium for Nocardia species from respiratory specimens.

Treating Syphilis: Examining therapeutic approaches to this STD.

Background information on treating syphilis indicates that some currently recommended approaches to therapy are not optimal. There is no perfect drug schedule available, but penicillin remains the drug of choice. The author's recommendations for treatment and follow up are presented.

Immunological tolerance of the mouse IgE system: dissociation between T cell tolerance and suppressor cell activity.

Immunological tolerance was induced in CBA mice with respect to both anti-hapten and anti-carrier IgE antibody production, following pretreatment of the animals with deaggregated ovalbumin. IgG antibody production was also affected. The tolerance was antigen-specific, was stable upon adoptive transfer to irradiated syngeneic recipients, but was reversed following booster. The extent and duration of the tolerant state depended on the dosage and number of tolerogen injections. Tolerogen administered after the initiation of the primary response was without effect. The pattern and duration of this tolerance suggested that T suppressor cells were not involved. The adoptive transfer of spleen cells from tolerogen-treated donors while being themselves unresponsive, failed to interfere with the induction of an immune response in the recipient. Evidence of T suppressor cell function was found in adoptive transfers, only after prolonged pretreatment of donors with a combination of tolerogenic and immunogenic forms of the carrier. These results suggested that T cell-dependent tolerance of the IgE antibody response operates via two distinct mechanisms, of which only one is provided by suppressor cell function.