Specimen collection and transport.

The approach to the collection and transport of meaningful and accurate microbiologic specimens depends upon the nature of the suspected infectious entity and upon the location of the pathogenic process, as well as the possession of appropriate instrumentation and containers. New information and newly developed collection-transport materials have improved the potential for the successful collection and isolation of pathogenic micro-organisms.

Evaluation of the rapid hippurate hydrolysis test with enterococcal group D streptococci.

The rapid hippurate hydrolysis test was evaluated with the conventional test, using 17 group A streptococci, 9 non-enterococcal group D streptococci, 108 enterococcal group D streptococci, and 2 strains of Listeria monocytogenes. There was complete correlation between the rapid and conventional tests with all organisms except enterococcal group D. The rapid hippurate hydrolysis method was more sensitive with the enterococci; 95.4% were positive with the rapid method, and 9.3% were positive with the conventional method. Thin-layer chromatography (TLC) was performed on all isolates to determine if the end product of hydrolysis, glycine, was indeed present. The TLC results were in agreement with the rapid and conventional methods for group A streptococci, nonenterococcal group D streptococci, and L. monocytogenes. TLC results were in total agreement with the rapid hippurate hydrolysis test for the enterococcal group D isolates, thus verifying the accuracy of this more sensitive test. Trace amounts of glycine were found in the substrate, indicating the need for including an uninoculated substrate control as well as stock strains of group A and B beta-hemolytic streptococci (negative and positive controls, respectively) each time the rapid hippurate hydrolysis test is performed.

Motility-indole-ornithine medium.

A medium designed for detection of motility, indole, and ornithine decarboxylase production in one tube was devised and evaluated. Results, using 182 strains of Enterobacteriaceae, were the same as obtained with commonly used standard methods, although 11 of 87 positive indole tests were weak with the new medium.

Rapid hippurate hydrolysis method for presumptive identification of group B streptococci.

A rapid test to detect the hydrolysis of sodium hippurate by beta-hemolytic streptococci within 2 h was developed. All group B streptococci tested were positive using this method and all other groups were negative.

Evaluation of bacteriological transport systems.

Seven commercially manufactured bacteriological transport systems, including Culturette, Trans-Cul (with Stuart and Amies), Handiswab, Securline (with Amies and Amies without charcoal) and Culture Caddy, were evaluated to determine whether these systems were capable of maintaining the viability and constant numbers of mixtures of hardy, fastidious and anaerobic organisms over 72 hours at 25C and 4C. The results of the study indicated that if specimens are maintained in transport systems at 25C they should be cultured at four hours to minimize loss of viability and to assure accurate quantitation. No one transport system excelled over the other for maintenance of cultures at room temperature. Most organisms survived well in all of the transport systems for 72 hours when refrigerated.

Simplified fluorescent-antibody staining method for primary plate isolates of group A streptococci.

Beta-hemolytic streptococci were identified from primary plates by using a simplified fluorescent-antibody staining method. There was 100% correlation between this method and standard precipitin grouping.

Rapid detection of yeast enzymes by using 4-methylumbelliferyl substrates.

In a preliminary study with a limited number of isolates, the usefulness of 17 4-methylumbelliferyl substrates for identifying yeast isolates was investigated. Substrates to detect acid phosphatase, glucosidase, and pyrophosphate diesterase showed promise.

Urinary tract infection in patients with spinal cord lesions: antibody-coated bacteria tests as a diagnostic aid.

Urine cultures and antibody-coated bacteria (ACB) tests were performed on urine specimens from 176 spinal cord injured patients at the time of annual renal function follow-up. Sixty-nine percent of the cultures were positive; and of these, 55% were positive for ACB. The highest incidence of positive ACB tests occurred in the specimens from patients with external catheters (67%), ileal diversions (63%) and suprapublic catheters (60%). The organisms which occurred most frequently as a single isolate were Escherichia coli and Pseudomonas aeruginosa; 54% of the E coli and 57% of the P aeruginosa were antibody coated. Proteus rettgeri was recovered less frequently as a single isolate but in these instances the ACB test was always positive. X-ray studies showed that 28% of patients with positive ACB tests had upper tract changes. Thirty-eight patients with positive ACB tests received treatment. After treatment, follow-up cultures from 26 (69%) of these patients showed no growth or a negative ACB test. Patients with roentgenographically abnormal tracts and positive ACB tests were found to be more resistant to treatment. Although additional studies are needed, this test at present can aid clinicians in management of urinary tract infection in spinal cord injured patients.

Detection of arginine dihydrolase in nonfermentative gram-negative bacteria by use of thin-layer chromatography.

Thin-layer chromatography was used to detect the presence of the arginine dihydrolase system in nonfermentative gram-negative bacteria. The test was positive for the fluorescent pseudomonads as well as Pseudomonas maltophilia, whereas other Pseudomonas sp., Mima, and Herellea were negative. This procedure can be completed in a few hours and may be useful in the clinical laboratory.

Rapid test for urease and phenylalanine deaminase production.

A rapid urea-phenylalanine medium was effective for the identification of Proteus and, with one exception, Providencia. Most Klebsiella and a few Enterobacter were urease-positive with this method.

Evaluation of a new incubation-type indole strip test.

A total of 189 of Enterobacteriaceae and three strains of Clostridium perfringens were tested with a new incubation-type indole paper strip. This 4-hr incubation test gave the same results as a standard 48-hr indole test, except with some strains of Proteus rettgeri. Results with P. rettgeri varied somewhat according to the medium upon which the organisms had been grown.

Evaluation of an adenosine 5'-triphosphate assay as a screening method to detect significant bacteriuria.

The bioluminescent reaction of adenosine 5'-triphosphate (ATP) with luciferin and luciferase has been used in conjunction with a sensitive photometer (Lab-Line's ATP photometer) to detect significant bacteriuria in urine. This rapid method of screening urine specimens for bacteriuria was evaluated by using 348 urine specimens submitted to the clinical microbiology laboratory at the University of Minnesota Hospitals for routine culture using the calibrated loop-streak plate method. There was 89.4% agreement between the culture method and the ATP assay, with 7.0% false positive and 27.0% false negative results from the ATP assay using 10(5) organisms/ml of urine or greater as positive for significant bacteriuria and less than 10(5) organisms/ml as negative for significant bacteriuria.

Particle size distribution analysis as a rapid method to detect significant bacteriuria.

Particle size distribution analysis (PSDA) was evaluated as a rapid screening method for detecting significant bacteriuria by linking a C1000 Channelyzer to a Coulter Counter. Colony counts and PSDA screening results were compared for 800 urine specimens. The PSDA method proved to be 92% specific, but only 64% sensitive, for detecting at least 10(5) colony forming units (CFU)/ml. By performing serial dilution colony counts on 109 culture-positive specimens (greater than or equal to 10(5) CFU/ml), it was determined that the low level of sensitivity (64%) was due to culture-positive specimens that had between 10(5) and less than 10(7) CFU/ml. The sensitivity of the PSDA method increased to 90% and 100% when culture-positive specimens had 10(7) or more and 10(8) or more CFU/ml, respectively. The low level of sensitivity demonstrated in this investigation makes the introduction of this method into clinical usage unacceptable at this time.

Rapid extraction method with pronase B for grouping beta-hemolytic streptococci.

The enzyme, Pronase B, was used to extract the C carbohydrates of betahemolytic streptococci for serological grouping. Reference strains of streptococci, groups A through N, were accurately grouped by using this extraction method. Of the beta-hemolytic streptococci isolated from patients' cultures, 1,197 were classified as either group A or not group A by this method. There was 100% correlation with the reference Lancefield method. In contrast, false reactions occurred with the presumptive bacitracin disc method in 4.1% of the group A and 12.7% of the non-group A cultures. The Pronase method proved simple, accurate, and readily adaptable to the clinical laboratory routine.

Motility-indole-lysine-sulfide medium.

A medium designed for the detection of motility, indole, lysine decarboxylase and deaminase reactions, and H2S production was devised and evaluated. Results, using 157 strains of enteric pathogens, were in agreement with reference methods. When 300 isolates from fecal cultures were screened using this medium, Shigella was easily differentiated from Escherichia and more of the Proteus species, especially P. morganii, could be eliminated from further study.