James J. Plorde

FOUR-YEAR PROSPECTIVE EVALUATION OF COMMUNITY- ACQUIRED BACTEREMIA: EPIDEMIOLOGY, MICROBIOLOGY, AND PATIENT OUTCOME

The objectives of this study were to (1) describe the epidemiology and microbiology of community-acquired bacteremia; (2) determine the crude mortality associated with such infections; and (3) identify independent predictors of mortality. All patients with clinically significant community-acquired bacteremia admitted to a university-affiliated Veterans Affairs medical center from January 1994 through December 1997 were evaluated. During the study period, 387 bacteremic episodes occurred in 334 patients. Staphylococcus aureus, Escherichia coli, and coagulase-negative staphylococci were the most commonly isolated organisms; the most frequent sources were the urinary tract and intravascular catheters. Approximately 14% of patients died. Patient characteristics independently associated with increased mortality included shock (OR 3.7, p = 0.02) and renal failure (OR 4.0, p = 0.003). The risk of death was also higher in those whose source was pneumonia (OR 6.3, p = 0.03) or an intra-abdominal site (OR 10.7, p = 0.02), or if multiple sources were identified (OR 13.4, p = 0.003). Community-acquired bacteremia is often device-related and may be preventable. Strategies that have been successful in preventing nosocomial device-related bacteremia should be adapted to the outpatient setting.

Survey of plasmids and resistance factors in Campylobacter jejuni and Campylobacter coli.

A total of 688 isolates of Campylobacter jejuni and Campylobacter coli were screened for the presence of plasmid DNA by agarose gel electrophoresis and were tested for susceptibility to ampicillin, chloramphenicol, erythromycin, streptomycin, and tetracycline. Of the isolates examined, 32% were noted to harbor plasmid DNA, ranging in size from 2.0 to 162 kilobases. Only tetracycline resistance was noted to correlate with the presence of plasmids. Plasmids capable of transferring tetracycline resistance via conjugation ranged in size from 42 to 100 kilobases. The Bg/II and Bc/I restriction endonuclease profiles of 31 plasmids examined showed marked diversity in their banding patterns. Although a high degree of DNA-DNA homology was noted among the Campylobacter spp. plasmids, no homology was noted between these plasmids and tetracycline R factors commonly found in the family Enterobacteriaceae. Images

Is the clean-catch midstream void procedure necessary for obtaining urine culture specimens from men?

Abstract To determine whether the results of voided urine cultures in men are affected by meatal cleansing, midstream sampling, or circumcision status, 308 paired (initial and midstream) specimens were collected from 254 urology clinic patients. Half of the patients cleansed their urethral meatus with povidone-iodine prior to voiding. The circumcision status of all patients was noted. The rates of true bacteriuria (growth of 10 4 or greater colony-forming units/ml urine with a single predominant species) and contamination (growth of 10 3 or greater colony-forming units/ml urine with two or more colonial types) were compared in the various collection technique subgroups. Neither the bacteriuria nor contamination rates were significantly different (p > 0.05) in circumcised and uncircumcised patients, or in those who cleansed their meatus and those who did not. Contamination, but not bacteriuria, rates were higher in initial as compared with midstream specimens. These data suggest that the clean-catch midstream void procedure is unnecessary for obtaining routine voided urine culture specimens from men.

Evaluation of four mycobacterial blood culture media: BACTEC 13A, isolator/BACTEC 12B, isolator/middlebrook agar, and a biphasic medium

Four commercially available mycobacterial blood culture systems were compared for sensitivity and time to detection of growth. A 5-ml volume of SPS-anticoagulated blood was cultured in a BACTEC 13A vial and a modified M7H11/BHI biphasic medium. In addition, two aliquots of Isolator concentrates, each derived from 5 ml of blood, were inoculated into a BACTEC 12B vial and onto a pair of Middlebrook 7H11 agar plates (M7H11). Mycobacteria were recovered from 32 of 180 cultured specimens (17.8%). Growth was detected in 30 (93.7%) of the 13A vials, 27 (84.4%) of the M7H11 agar plates, 26 (81.2%) of the 12B vials, and 14 (43.8%) of the biphasic bottles. The mean times to growth detection in the 13A vial (14.2 days) and the 12B vial (13.7 days) were shorter than in either the M7H11 plates (20.8 days) or the biphasic medium (24.1 days). When the Isolator/12B vial-and-M7H11 plates were evaluated as a single system, 29 cultures (90.6%) had a mean time to growth detection of 13.5 days. Colony-forming units per ml were inversely associated with time to growth detection. Delay in transport (greater than 24 h) appeared to reduce viability. The direct inoculation feature makes the 13A vial very suitable for mycobacterial blood cultures.

Isolation of Plasmids Encoding Tetracycline Resistance from Campylobacter jejuni Strains Isolated from Simians

Fifteen isolates of tetracycline-resistant Campylobacter jejuni were recovered from stool samples of cynomologous monkeys (Macaca fascicularis) housed at the University of Washington Primate Research Center, Seattle. Resistance was associated with carriage of a 38-megadalton plasmid which was transmissible to other strains of C. jejuni but not to Escherichia coli. Seven isolates also contained a 2.6-megadalton plasmid which was phenotypically cryptic. Images

Laboratory diagnosis of urinary tract infections in men

Summary In order to understand the epidemiology and pathogenesis of urinary tract infections in men, as well as to most effectively treat them, it is important to determine the best collection procedures and the most appropriate diagnostic criteria for bacteriuria. Studies by our group and others have begun to define the ways in which the laboratory diagnosis of bacteriuria in men differs from that in women. Future efforts should be aimed at discovering how men develop bacteriuria, how the prostate gland becomes infected, how to more accurately localize bacteriuria in men, and how such infections are best treated. Meanwhile, we offer the following recommendations: o 1.Recognize that guidelines for the laboratory diagnosis of urinary tract infections are derived almost entirely from studies on women, and that these are not always applicable to men. 2.In obtaining voided specimens for culture, meatal cleansing is not necessary, regardless of the mans circumcision status; midstream sampling is preferable, but not mandatory. 3.Culture of voided urine is extremely sensitive and specific for detecting true bacteriuria; bladder specimens are unnecessary unless the patient is unable to void or the voided urine results are difficult to interpret. 4.When bladder specimens are necessary, suprapubic aspiration is preferable to urethral catheterization. 5.The best definition of bacteriuria for voided urine is growth of ≥10 3 cfu/mL of one or two microbial species. 6.The role of the prostatic localization study is unclear, and therefore it should not be performed routinely on men with bacteriuria. 7.In terms of cost, speed, and sensitivity, the Gram-stained smear remains the primary screening procedure for detecting bacteriuria for most microbiology laboratories. 8.In patients with irritative genitourinary symptoms or a positive Gramstained smear, a specimen should be plated on chocolate agar when standard urine cultures are negative.

Performance characteristics of bioassay, radioenzymatic assay, homogeneous enzyme immunoassay, and high-performance liquid chromatographic determination of serum gentamicin.

We compared the accuracy, precision, and between-method error of the microbiological assay, the radioenzymatic assay, the homogeneous enzyme immunoassay, and the high-performance liquid chromatographic assay for the quantitation of gentamicin in serum. Precision and accuracy were evaluated by reference samples prepared to contain 0.0 to 32.7 micrograms of gentamicin per ml. Correlations between the methods utilized patient sera with gentamicin concentrations ranging from 0.6 to 13.3 micrograms/ml. All methods were reliable within acceptable limits for routine clinical use; intermethod correlation coefficients exceeded 0.96. Relative to the microbiological assay, the alternative methods offer the advantage of rapid analysis. The elapsed times for acquiring data on a set of 10 specimens under routine operating conditions were 0.5 h by the enzyme immunoassay, 4 h by the radioenzymatic assay, 5 h by the high-performance liquid chromatographic assay, and 10 h by the microbiological assay.

Bacterial culture specimens: Categories, collection, and interpretation

An approach to the collection and interpretation of bacterial cultures based on specimen category is presented. The sensitivity and specificity of cultures of material taken from deep closed body areas (category 1), deep communicating body areas (category 2), and superficial body surfaces (category 3) are considered.

Evaluation of the FIAX semiautomatic fluorescent immunoassay system for the detection of IgG antibodies to Toxoplasma gondii

A commercially available solid phase fluoroimmunoassay system (FIAX, International Diagnostic Technology, Santa Clara, CA) was evaluated in parallel with a standard indirect fluorescent-antibody test (IFAT) for the detection of IgG antibodies to Toxoplasma gondii. Titers obtained by the FIAX method on the 101 patient samples correlated well with the standard procedure. Sensitivity of the FIAX system was 96% and specificity was 93%. A method for measuring serum titer reproducibility applicable to both conventional doubling dilution and to automated procedures was employed, allowing a meaningful comparison of precision in the two systems. It was found that titer reproducibility in the FIAX system was better than that of the IFAT and exceeded that expected with most conventional double-dilution serological procedures. The FIAX system will most benefit those laboratories with relatively large numbers of samples which can be batch tested.

Potential Liabilities of Gentamicin Homogeneous Enzyme Immunoassay

We report two potential liabilities of the homogeneous enzyme immunoassay for the determination of serum gentamicin. One is a considerable loss of precision and accuracy at the ends of the calibration curve, and the other is an apparent loss of gentamicin with storage at −60°C.