Direct immunofluorescence for the diagnosis of legionellosis.

Culture and direct immunofluorescent microscopy (DFA) results for Legionella pneumophila were reviewed over a two-year period. In the first year, a positive result was defined as having at least one morphologically typical fluorescing organism. In the second year, a positive was defined as at least five typical fluorescing organisms. Despite these stricter criteria and other measures to reduce the possibility of reagent contamination, there was no statistically significant difference in the sensitivity or specificity of the DFA in the two years for sputa, deep specimens or overall. Of 37 sputum specimens from infected patients, 16 were positive on DFA. Thirty-two of 38 positive patients were detected by sputum culture. DFA can provide rapid diagnostic information but cannot be used to rule out the diagnosis. Sputum is a useful specimen for the initial laboratory investigation of patients with legionellosis.

Plaque assay for virulent Legionella pneumophila.

Methods of assessing virulence of Legionella pneumophila, the etiologic agent of Legionnaires disease, include the infection of guinea pigs, fertile chicken eggs, and mammalian and protozoan cell cultures. Guinea pig assays, in particular, are expensive, laborious, or unsuitable for routine screening of Legionella isolates. We have developed a virulence assay that requires the enumeration of viruslike plaques which are the result of virulent L. pneumophila infecting mouse L929 cells. Each plaque is the consequence of the initial infection of an L cell with a single bacterium. A nonvirulent mutant derived from the serial passage of virulent L. pneumophila on Mueller-Hinton agar fails to survive within L cells and consequently fails to produce plaques.

Nosocomial outbreak of Pseudomonas aeruginosa folliculitis associated with a physiotherapy pool.

Outbreaks of community-acquired Pseudomonas aeruginosa folliculitis have recently been described in association with health spa whirlpools. In February 1984 we detected an outbreak of Pseudomonas folliculitis among hospital staff and patients using a swimming pool in a newly constructed physiotherapy unit. A rash developed in 5 (45%) of the 11 physiotherapists who had used the pool, as compared with 0 of the 17 who had not (p less than 0 005). Pseudomonas folliculitis also developed in 6 (21%) of 29 outpatients and 4 (33%) of 12 inpatients who had used the facility; Pseudomonas infection of a surgical wound also developed in 1 of the 4 inpatients. The epidemic curve was consistent with a continuing common-source outbreak. P. aeruginosa, serotype O:10, was isolated from three physiotherapists, the patient with an infected surgical wound and the pool. A case-control study of pool users did not identify risk factors for infection, although the physiotherapists had spent longer in the pool than had the patients. After hyperchlorination and structural repairs to the pool, no further cases were identified among pool users. This outbreak is the first reported nosocomial outbreak of Pseudomonas folliculitis. Further investigation is needed to determine the risk of serious Pseudomonas infections in hospitalized patients using physiotherapy pools.

Isolation of Legionella pneumophila from the blood of a patient with Legionnaires' disease.

Legionella pneumophila is rarely isolated from blood cultures. Presently most cases of Legionnaires' disease are diagnosed retrospectively from the results of indirect fluorescent antibody tests, which possess inherent disadvantages. An 81-year-old woman with a history of diabetes mellitus presented symptoms of Legionnaires' disease. Five hours before her death 1.5 mL of blood was withdrawn from a scalp vein and seeded to a culture medium. Following incubation for 3 days L. pneumophila serotype 1 was isolated.

A synthetic based medium for the isolation of Listeria monocytogenes.

We have compared two media (Tryptone Soya Nalidixic Acid Agar and Tryptone Soya Gum Base Nalidixic Acid Medium) for the isolation of L. monocytogenes from pathological and environmental specimens. These media were used in conjunction with Henry's Oblique Light System. We found that the gum based medium gave the better results. The medium is uniformly transparent, partially suppressive to unwanted organisms and allows colonies of Listeria to be readily identified.

Assessment of expectorated sputum for bacteriological analysis based on polymorphs and squamous epithelial cells: six-month study.

Samples of sputum were examined microscopically to determine their suitability for routine culture. When the number of squamous epithelial cells per field was less than 10, the number of bacterial species generally fell within the range of one to four. Squamous epithelial cells were not always a true indication because some unmarked transtracheal specimens showing more than 10 squamous epithelial cells also gave a range of isolation falling between one and four. When the presence of 25 or more polymorphs was used as the parameter, the number of bacterial isolates generally fell within the range of one to three, but this resulted in positive overbiasing with consequent rejection of valid specimens. Later it was found that when a differential system using both polymorphonuclear cells and squamous epithelial cells was applied, a significant number of specimens could be salvaged which would otherwise have been discarded.

Comparison of four culture media for the isolation of Mycobacterium tuberculosis: a 2-year study.

Four media, Lowenstein-Jensen, Middlebrook, Petragnani, and ribonucleic acid, were tested for comparative ability to detect Mycobacterium tuberculosis. Specimens used included sputum, urine, tissue, and gastric washings. Three types of comparison were used: (i) comparison derived from randomized specimens; (ii) comparison of cultures from newly diagnosed cases that had received no prior therapy; and (iii) comparison of cultures from specimens whose initial direct smears were negative. Overall, ribonucleic acid medium performed best, but the differences among the four media were small.