Colleen Trombley

Candida dubliniensis fungemia and vascular access infection.

Candida dubliniensis is a newly recognized species of yeast, which may have been forrmerly identified as Candida albicans, that has been rarely isolated from invasive fungal infections among humans. The authors document a C. dubliniensis fungemia that occurred during the course of a vascular access infection in a 2-year-old who was undergoing active therapy for neuroblastoma. Presumptive C. albicans isolates from an 18-year period were reassessed, and it was found that C. dubliniensis is a rare cause of fungemia among pediatric patients (0.5% of all such isolates).

Oxacillin susceptibility of coagulase-negative staphylococci: role for mecA genotyping and E-test susceptibility testing

For 115 clinical isolates of coagulase-negative staphylococci which were acquired from 100 patients, we compared the results of routine critical agar dilution susceptibility testing (4% NaCl, 6 mg/ml oxacillin) with mecA gene detection by a polymerase chain reaction amplification. Discrepant results were subsequently reassessed with critical agar dilution testing, repeat mecA genotyping, disc radial diffusion susceptibility testing, E-test and determination of beta-lactamase status. For the initial comparisons, 36 isolates were susceptible and lacked mecA whereas 54 isolates were resistant and had evidence of mecA. Among 17 mecA positive/agar dilution susceptible bacteria, four were clearly resistant by E-test, one isolate had borderline resistance (MIC, 2-4 mg/l), and 12 were resistant when E-test was applied to resistant subpopulations. Initial E-tests facilitated the recognition of the heteroresistant isolates. For eight mecA negative/agar dilution resistant isolates, two were confirmed as oxacillin susceptible and six were mecA positive upon retesting. Although 53.9% had been classified initially as resistant by agar dilution, 67.0% were finally deemed resistant. Critical agar dilution underestimates oxacillin resistance among coagulase-negative staphylococci, and accurate detection of resistance is facilitated by mecA genotyping and E-test.

Verification of a PCR-based typing method for Acinetobacter baumannii in a pseudo-outbreak investigation

Acinetobacter spp. isolates were increasingly obtained from clinical specimens and sterility samples, and a subsequent epidemiological investigation implicated an intermittently contaminated supply of commercially acquired enrichment broths. Typing was performed with DNA amplification by the polymerase chain reaction (PCR) using enterobacterial repetitive intergenic consensus sequence primers, ERIC2 and reverse ERIC1R. The reliability of this PCR-based typing method was verified by the ability of the technique to demonstrate homology and differences among isolates from an epidemiologically well-defined pseudo-outbreak.

Correlation of erythromycin agar dilution susceptibility testing with disc diffusion susceptibility for Bordetella pertussis.

Agar dilution and disc diffusion susceptibility testing of erythromycin were performed for contemporary isolates of Bordetella pertussis with the use of charcoal media. Minimum inhibitory concentration (MIC) values ranged from < or = 0.016-0.5 mg/l and the MIC(50) and MIC(95) were 0.125 and 0.25 mg/l respectively. Disc diffusion zone sizes were interpretable after either 48 or 72 h of incubation and all inhibition diameters were > or = 37 mm.

A comparison of IgM anti-P1 immunoblotting and a polymerase chain reaction assay for the diagnosis of acute Mycoplasma pneumoniae respiratory infection in children

A rapid IgM immunoblotting serological test was compared to a polymerase chain reaction (PCR) assay of respiratory specimens for the diagnosis of acute Mycoplasma pneumoniae infection. Among 112 paired specimens, the frequency of a positive diagnosis by any method was 7.1%. Both IgM serology and PCR were positive for only two out of eight infected patients. PCR positive, IgM negative patients (4) were ill for an insufficient period to allow the IgM response to be demonstrable (⩽7 days). PCR negative, IgM positive patients (2) were likely to have had negative amplification assays because of the nature of the respiratory specimens. Nasopharyngeal washings uncommonly inhibited PCR amplification. Both rapid serological and genetic amplification assays have a role, together or alone, in the diagnosis of M. pneumoniae infection and paradigms for cost-effective utilization will be required.

Appraisal of the stability of leukocytes in refrigerated urine.

There is limited evidence that urinary leukocytes are rapidly destroyed in alkaline hypotonic urine. We assessed the stability of leukocytes in urine specimens provided by 90 children with neurogenic bladder who attended a meningomyelocele clinic. No significant correlation was found between urine specific gravity and leukocyte survival after an interval of 4 h in a sample of 30 specimens from these patients. The survival of leukocytes was determined at 2 h and at 4 h in aliquots of these 30 specimens directly, and after adjustment to pH values of 5.0, 7.0, 8.0, 8.5, and 9.0. Statistically significant leukocyte destruction only occurred at pH 9.0 at 2 h (16%), at pH 8.5 at 4 h (19%), and at pH 9.0 at 4 h (57%). Only one of a further sample of 180 routine specimens had both a pH of > or = 8.5 and an interval to laboratory examination of > 2 h. No specimen had a specific gravity of < 1.002, and 93.9% had values of > or = 1.005. Urine pH and tonicity were not therefore important determinants of leukocyte stability in refrigerated samples examined within 4 h from this clinic population.

Markers of virulence among prospectively acquired putative enteropathogenic Escherichia coli serogroups.

We assessed the frequency of proposed enteropathogenic virulence factor genes (eaeA and eaf) by genetic amplification for a series of prospectively collected putative enteropathogenic Escherichia coli serogroup isolates that were acquired from the stool specimens of children. Among 102 isolates, eaeA and eaf markers were determined among 27.5% and 4.9%, respectively. Eaf positivity was found to be coexisting in only a minority of eaeA+ E. coli; the eaeA+/eaf- genotype was most common among strains that had evidence of at least one virulence marker. When clinical variables were compared for two groups of patients whose strains did or did not possess eaeA, the eaeA+ group was more likely to have had an acute diarrheal illness (P = .05) and less likely to have had an underlying chronic illness (P = .03). Localized adherence in vitro was easily recognized for eaeA+/eaf+ E. coli but eaeA+/eaf- isolates were less consistent in manifesting this phenotype. The availability of genetic amplification technologies has the potential to rekindle diagnostic interests in this area, although a rational approach has yet to be defined.