Hospital Diagnostic Laboratory Research Articles

An outbreak of rotavirus gastroenteritis on a pediatric unit

Rotaviruses were first observed by Bishop et al.’ in 1973 by electron microscopic examination of duodenal biopsy tissues from acutely ill infants and young children with diarrhea. Since that time, studies in many countries throughout the world have documented rotaviruses as a major cause of gastroenteritis in infants and young childrenFP4 The incubation period of rotavirus is approximately 1 to 3 days.5 Recently an enzyme-linked immunosorbent assay (ELISA) has become commercially available, making the detection of rotavirus antigen more practical in the hospital diagnostic laboratory.*’ 6 On Oct. 15, 198 1, this test was instituted on a routine basis at our hospital. Shortly thereafter, an increased incidence of community-wide rotavirus infection occurred.7 This led to an increase in the number of children admitted to our hospital with rotavirus diarrhea. During the epidemic a nosocomial outbreak of the disease was also documented.

Standardized Disk-diffusion Susceptibility Test forHaemophilus influenzae

The emergence of ampicillin-resistant strains of Haemophilus influenzae has emphasized the need for an improved practical method for routine susceptibility testing of clinical isolates. We have previously described a simplified medium for quantitative dilution susceptibility testing that is composed of Mueller-Hinton medium plus Supplement C (Difco). In the present study, paired broth-dilution and disk-diffusion susceptibility tests with ampicillin and chloramphenicol were performed on 100 strains of Haemophilus (95 H. influenzae and five H. parainfluenzae), including 30 strains with previously documented ampicillin resistance. Disk-diffusion tests were performed in exactly the same manner as the standardized Kirby-Bauer procedure used for less fastidious organisms, except that supplemented Mueller-Hinton agar plates were incubated in an increased-CO2 atmosphere. Using this method, ampicillin-susceptible strains of Haemophilus produced zone diameters of 22 mm or more, while ampicillin-resistant strains produced zones of 18 mm or less. All strains were chloramphenicol-susceptible and produced zone diameters of 30 mm or more. This method would allow routine disk-diffusion testing of isolates of H. influenzae by hospital diagnostic laboratories, using a clear medium that closely resembles unsupplemented Mueller-Hinton agar.

Bacteria recovered from distilled water and inhalation therapy equipment.

THE PRESENT STUDY was begun as an attempt to describe the species of bacteria which were found in distilled water in inhalation therapy equipment. However, classification of the isolates was difficult, particularly forPseudomonas-like species.1-5Because of the need to improve communication between clinician and bacteriologist, this paper summarizes the taxonomy of these organisms and defines bacterial isolates in terms of techniques simple enough to be available to the routine hospital diagnostic laboratory. The terminology previously used in the medical literature, and generally recognized as indicating a water source is retained in this paper, in spite of considerable disagreement among authorities over the use of the termsMima, Herellea, Achromobacter, andAlcaligenes.6-10 Methods Primary Isolation of Organisms.—Clean, dry surfaces of inhalation therapy equipment were cultured by rubbing with a sterile cotton swab, which was transported in thioglycollate broth, and inoculated on 5% sheep blood agar plates.

Extended study of Serratia in a diagnostic bacteriology laboratory.

The incidence of Serratia in clinical material received in a general hospital diagnostic laboratory was studied. Initially the morphologic features, biochemical characteristics, chromogenesis, and antibiotic susceptibility of 21 isolates were examined. On the basis of these studies certain cultural and biochemical tests were selected for routine identification of Serratia.Serratia isolated from various types of clinical specimens received during a 4-year period (1960–1964) were recorded. Most of the Serratia were nonchromogenic except on a special medium. The cultures were resistant to a number of antibiotic agents, particularly penicillin, polymyxin B, and the tetracyclines. A higher incidence of Serratia in sputum than in throat and nasopharyngeal cultures was observed. There was a noticeable increase in the overall incidence of Serratia isolates over the 4-year period. This may be a reflection of hospital acquired infections.

The Anonymous Mycobacteria in Human Disease

The occurrence of mycobacteria other than the classic tubercle bacilli in apparently etiologic relation to tuberculosis-like disease has received increased attention in the last few years. Of the 23 contributors to this small book, some are concerned with the identification of these mycobacteria and their frequency in specimens submitted to health department and hospital diagnostic laboratories, others with differential diagnosis and treatment. The accompanying discussions have been reported in detail. The anonymous mycobacteria are divided into four groups, two chromogenic and two nonchromogenic. Pulmonary disease apparently caused by these bacteria closely simulates tuberculosis, and it has not been possible to differentiate it in chest films. Endobronchitis seems to be somewhat more common than tuberculosis, in general the lesions are more acute and exudative, and there appears to be somewhat more nonspecific inflammation and fibrosis. Similarly, the lesions of infected lymph nodes closely resemble those of tuberculous infection, including calcification in