The state of public health laboratories.

Public health laboratories in the United States exist at the federal, state, and local level. The earliest laboratories were created in the late 1800s in the wake of the work of Robert Koch and Louis Pasteur. Currently, these laboratories make up a loosely formed network. The combined state portion of this network employs more than 6,000 staff members, tests more than 20 million specimens each year, and has a combined annual budget of more than $300 million. Public health laboratories are found in a variety of organizational settings. Several efforts have been made to define the roles of public health laboratories. Recently, the Association of Public Health Laboratories adopted a consensus position that has formally set forth the core functions, which include activities such as environmental testing, emergency response, surveillance, and reference services. Public health laboratories are being challenged with funding, new technology, and current issues such as bioterrorism, food safety, and antimicrobial resistance.

Prevalence of cryptosporidiosis in dogs and human beings in San Bernardino County, California.

Fecal specimens from 200 stray dogs impounded at the San Bernardino City and County animal shelters were screened for Cryptosporidium sp oocysts, using the auramine-rhodamine fluorescent staining procedure. The University of California, Los Angeles acid-fast stain was used for confirmation. Only 4 (2%) dogs were passing cryptosporidial oocysts. Likewise, stool specimens from 664 people were submitted to the San Bernardino County Department of Public Health Laboratory for routine parasitologic examination and were screened for Cryptosporidium sp. Cryptosporidial oocysts were detected in 20 human fecal specimens (3.01%). On the basis of these findings, it appears that the human and canine populations of San Bernardino County are at low risk for development of cryptosporidiosis at this time.

Evaluation of the 7-h membrane filter test for quantitation of fecal coliforms in water.

The 7-h fecal coliform (FC) test for detection of FC organisms in water was evaluated to establish its validity and usefulness for emergency and disaster situations. The waters tested consisted of routine samples collected for public health surveillance and enforcement purposes. A total of 984 water samples from throughout California were assayed. These included samples from coastal salt waters, rivers, canals, and reservoirs, in addition to potable and miscellaneous freshwater sources. A portion of each sample was tested concurrently by both the 7-h FC test and the most-probable-number FC five-tube test. The 7-h FC test samples were incubated for 7 to 7.25 h at 41.5 degrees C. Overall, greater than 90% agreement was obtained between the methods in determining whether the water quality was acceptable or unacceptable. Statistical analysis of the 984 samples confirmed that the 7-h FC method was a suitable alternative to the most-probable-number FC method for evaluation of freshwater samples. During emergencies or disasters, the 7-h FC test could provide a means for detection of fecal contamination of water with results available in less than 1 day.

Investigation of cryptosporidial infection in calves in San Bernardino County, California.

Cryptosporidium is a protozoan parasite that inhabits the intestinal epithelium of calves, lambs, foals, pigs, and poultry. Of the 500 calves studied, 95 calves had diarrhea and 20 (21.05%) of those were infected with Cryptosporidium; only 8 (1.9%) of the remaining 405 nondiarrheic calves had Cryptosporidium oocysts in their feces.

Detection of herpes simplex virus in clinical specimens by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) for the detection of herpes simplex virus is described that can be performed in approximately four hours. The test, which does not require specialized equipment and uses relatively inexpensive, commercially available reagents, detected herpes simplex virus in 51% of specimens found to be positive by a time-consuming cell culture technic. The ELISA test compared favorably with a direct immunofluorescence method that detected HSV in only 1% of the cell culture-positive specimens. The ELISA test was readily carried out even with specimens unsuitable for cell culture and did not require cellular material as is the case with immunofluorescence technics. An advantage of the ELISA test for herpes simplex virus over the cell culture method was the detection of nonviable virus.

Isolation of Chlamydia psittaci from naturally infected African clawed frogs (Xenopus laevis).

An inclusion-forming agent was isolated from the livers of commercially raised African clawed frogs (Xenopus laevis) involved in an epizootic of high morbidity and mortality. Original isolation was made in McCoy cells. This agent was identified as Chlamydia psittaci based on the formation of typical intracytoplasmic inclusions which developed within 48 h, were not stained by iodine, and were resistant to sulfadiazine. The isolate from one particular frog (designated as strain 178) was further studied and found to be lethal for 7-day-old embryonated chicken eggs after intra-yolk sac inoculation. This strain was demonstrated not to be pathogenic for mice when inoculated intraperitoneally. The cell culture isolate of C. psittaci was transmitted to uninfected X. laevis, causing disease and death.

Spontaneous and experimental infections of Xenopus laevis with Chlamydia psittaci.

Chlamydial infection was suspected when widespread pyogranulomatous inflammation and large basophilic intracytoplasmic inclusion bodies were evident histopathologically in African clawed frogs (Xenopus laevis) dying of a spontaneous disease of high morbidity and mortality. Organism morphology was determined by electron microscopy of infected hepatic sinusoidal lining cells, and it was characteristic of the unique developmental cycle of a chlamydial agent. Isolation and speciation of the organism was achieved in a McCoy cell culture system. The infected cells were inoculated into disease-free frogs reproducing the disease.

Nonspecific reactions in the hemagglutination inhibition test for detection of rubella antibodies.

Approximately 7% of the sera tested to determine the presence of rubella-specific antibodies by the hemagglutination inhibition test demonstrated abnormal patterns of reactivity, rendering the test unreadable. Another 3% of sera were shown to have false-positive titers as high as 1:128. When these abnormally reacting and false-positive sera were heated at 56 degrees C for 30 min after chemical treatment they always converted to negative, indicating the absence of specific rubella hemagglutination-inhibiting antibody. These results were confirmed by fractionation of the sera after sucrose gradient centrifugation. It was established that manifestation of these nonspecific results was dependent on the concentration of Ca2+ or Mn2+. The heat-labile inhibitor(s) responsible for abnormal and false-positive reactions was found not to be complement. This inhibitor(s) was detected in the light fractions of sera and when added to negative sera was capable of reproducing the abnormal patterns of reactivity. These results emphasize the necessity of heating sera for the rubella hemagglutination inhibition test after the chemical removal of nonspecific inhibitors.

Quantitative evidence of intestinal colonization by Clostridium botulinum in four cases of infant botulism.

Infant botulism is an infectious form of a disease heretofore principally known as food-borne intoxication. Previous epidemiologic and laboratory studies have shown that infant botulism results from the ingestion of spores of Clostridium botulinum that subsequently germinate in the infant intestine and produce botulinal toxin. A quantitative study of the fecal microflora of four infants with infant botulism revealed the presence of C. botulinum in numbers as high as 6.0 x 10(8) colony-forming units (cfu)/g. At various times after the onset of illness, the numbers of C. botulinum that were recovered from feces ranged from 10(3) to 10(8) cfu/g and constituted from 0.01% to 3.3% of the total fecal flora. It was concluded that the large numbers of C. botulinum found in patients' feces could occur only as a consequence of in vivo spore germination and outgrowth.