Application of immunoperoxidase staining to more rapid detection and identification of rubella virus isolates

Efforts were made to shorten the time required for detection of rubella virus in clinical materials through the use of immunoperoxidase (IP) staining. Comparative studies were performed in which specimens were inoculated in parallel into BHK-21 hamster kidney cells, which were examined by IP staining at 5 days, and into BK-13 and BS-C-1 cells, which were examined in two ways, viz., by subpassage at 7 days into BHK-21 cells and IP staining 3 days later and by subpassage at 7 days into BS-C-1 cells followed by interference testing and immunofluorescence (IF) staining on positive materials (standard method). Direct inoculation into BHK-21 cells with IP staining at 5 days permitted detection and identification of 59% of the 63 positive specimens. Toxicity of some specimens preserved with sorbitol and of certain tissue specimens reduced the number of satisfactory examinations which could be performed in this system. Virus detection and identification by IP staining on subpassaged RK-13 and BS-C-1 materials, requiring a total of 18 days, was comparable to the longer interference-IF method, requiring 17 days. Results obtained by IP staining and interference-IF showed 98% correlation on RK-13 materials and 97% correlation on BS-C-1 materials. IP staining on inoculated BHK-21 cells can be a useful method for rapid identification of a relatively high proportion of rubella-positive specimens, particularly if sorbitol-preserved specimens are avoided, and IP staining on subpassaged RK-13 and BS-C-1 materials is a highly satisfactory alternative to the longer interference-IF method.

Further observations on infections of guinea pigs with Venezuelan encephalitis virus strains

Guinea pigs from a Guatemalan colony died after subcutaneous inoculating of moderately small doses of equine-benign strains of Venezuelan encephalitis (VE) virus of hemagglutination-inhibition subtype I-E from enzootic habitats in Mexico and Guatemala. Thus these guinea pigs were unlike English short hair and inbred 13 guinea pigs, which usually survive infections with equine-benign VE strains of subtype I-E. We therefore caution others that not all strains of guinea pigs can be used to evaluate the potential equine virulence of VE viruses.

Food and environmental aspects of infant botulism in California

In an effort to identify vehicles by which Clostridium botulinum spores might have reached the intestine of patients with infant botulism, 555 samples of foods, drugs, and environmental specimens were examined. Of the food items, C. botulinum was only found in nine of 90 (10%) honey specimens. Five patients had been exposed to honey that contained C. botulinum, and ingestion of honey was found to be a significant risk factor for type B infant botulism (P = 0.005). In addition, C. botulinum was isolated from five samples of soil (three from case homes, two from control homes) and from vacuum cleaner dust from one case home. In every instance in which C. botulinum was isolated from a specimen of honey, soil, or duct associated with a case of infant botulism, the type of toxin (A or B) in the honey, soil, or dust isolate matched the type of toxin of the organism recovered from the infant. Isolation of C. botulinum from the soil of homes of control infants emphasizes the ubiquitous distribution of and exposure to this organism and suggests that host factors are important in the development of illness. Prevention of infant botulism will depend on the identification of these host factors, as well as on the identification of other vehicles that, like honey, may convey C. botulinum spores to susceptible infants.

The clinical spectrum of infant botulism

Infant botulism is the systemic illness that results when spores of Clostridium botulinum germinate in the infant's intestine and then produce botulinal toxin in vivo. As with other infectious diseases, infant botulism has a spectrum of clinical severity that ranges from a mild, outpatient illness to fulminant, sudden death. Most cases reported to date have been recognized in infants so weak and hypotonic that their need for hospital care was unquestioned; yet even this group of patients displayed a wide range in severity of illness. The outpatients were initially considered to be cases of "failure to thrive," while the fulminant cases were indistinguishable at autopsy from typical instances of the sudden infant death syndrome (SIDS, crib death). This article discusses the observed spectrum of clinical severity, the management of the hospitalized patient, and the manner in which sudden death might result from production of butulinal toxin in the intestine.

Honey and other environmental risk factors for infant botulism

Infant botulism results from the in vivo production of toxin by Clostridium botulinum after it has colonized the infant's gut. Epidemiologic and laboratory investigations of this recently recognized disease were undertaken to identify risk factors and routes by which C. botulinum spores might reach susceptible infants. Clostridium botulinum organisms, but no preformed toxin, were identified in six different honey specimens fed to three California patients with infant botulism, as well as from 10% (9/90) of honey specimens studied. By food exposure history, honey was significantly associated with type B infant botulism (P = 0.005). In California, 29.2% (12/41) of hospitalized patients had been fed honey prior to onset of constipation; worldwide, honey exposure occurred in 34.7% (28/75) of hospitalized cases. Of all food items tested, only honey contained C. botulinum organisms. On household vacuum cleaner dust specimens and five soil specimens (three from case homes, two from control homes) contained Clostridium botulinum. The known ubiquitous distribution of C. botulinum implies that exposure to its spores is universal and that host factors contribute importantly to the pathogenesis of infant botulism. However, honey is now an identified and avoidable source of C. botulinum spores, and it therefore should not be fed to infants.

Mammalian cell mutant requiring cholesterol and unsaturated fatty acid for growth

A mutant requiring both cholesterol and oleate for growth has been isolated from mutagenized Chinese hamster ovary cells. By comparison with wild-type cells, sterol and unsaturated fatty acid biosynthetic activities in the mutant cells grown in fetal calf serum medium appear to be nearly intact. However, whole-cell radioactive acetate, mevalonate, dihydrolanosterol, and stearate incorporation studies show that sterol synthesis from acetate, lanosterol demethylation, and fatty acid desaturation are defective in the mutant cells grown in delipidated serum medium. In vitro enzyme assays with crude cell extracts demonstrated that beta-hydroxy-beta-methylglutaryl-coenzyme A reductase is not induced in the mutant. These experiments were substantiated by gas/liquid chromatographic analyses which showed the sterol content and the percentage unsaturated fatty acids in mutant cells to be drastically reduced when the cells are grown in delipidated serum medium. A spontaneous revertant exhibiting prototrophic growth in lipid-free medium has been isolated from 50 X 10(6) mutant cells. All three defects in this revertant reverted back in parallel, which suggests that these three biosynthetic activities may be controlled by a common regulatory mechanism.

Co-circulation of two influenza A (H3N2) antigenic variants detected by virus surveillance in individual communities

From March through June 1977 a total of 31 influenza A (H3N2) viruses were isolated from students with respiratory disease who were seen at the student health service on the Berkeley campus of the University of California, and 32 influenza A (H3N2) viruses were isolated from persons who participated in a city-wide febrile respiratory disease surveillance program in Seattle. The antigenic specificity of the hemagglutinin was determined for each isolate by hemagglutination inhibition testing with sera from ferrets infected with prototype strains A/Victoria/3/75 and A/Texas/1/77. In each of the three months, April, May and June, A/Victoria/3/75-like and A/Texas/1/77-like viruses were identified among isolates from both communities, and the numbers of isolates of the two antigenic variants from patients seen with influenza-like illnesses were similar. The findings emphasize the need to examine multiple isolates even from within single communities to determine the antigenic specificity of current strains of influenza virus.

Intestinal infection and toxin production by Clostridium botulinum as one cause of sudden infant death syndrome

The spontaneous production of botulinum toxin in the infant gut by ingested Clostridium botulinum organisms is the underlying cause of infant botulism, recognised as an infectious disease only in late 1976. Because of the recognition of the pathophysiology of this disease and because the known potency and action of botulinum toxin can lead to rapid respiratory arrest, it appeared possible that the in-vivo production of botulinum toxin could cause the sudden death of some infants. To test this hypothesis, serum, selected tissues, and bowel contents from 280 dead infants were examined for the presence of C. botulinum toxin and/or organsisms. We found C. botulinum organisms in 10 infants, all of whom died suddenly and unexpectedly. 9 of these deaths were classified by the forensic pathologist as sudden infant death syndrome (S.I.D.S. or crib death). In 2 of these 10 sudden deaths both C. botulinum organisms and botulinum toxin were identified, and from the spleen of 1, C. botulinum organisms were isolated. Faecal specimens from 160 age-matched healthy infants who served as controls in studies of inpatient infant botulism cases were negative for both C. botulinum organisms and toxin, except for one specimen that contained only C. botulinum type A organisms. The 9 S.I.D.S. cases with evidence of C. botulinum infection comprised 4.3% of the 211 S.I.D.S. cases examined over 12 months. These findings suggest that intestinal production of botulinum toxin by C. botulinum is one cause of S.I.D.S. The strikingly similar age-distribution of 62 inpatient infant botulism cases and the 211 S.I.D.S. cases is also consistent with this concept. The possibility that in-vivo production of botulinum toxin may account for a larger proportion of S.I.D.S. cases is discussed.

Testing of hypoxic cell radiosensitizers in vivo

Use has been made of the transplantable KHT sarcoma in C3H mice to test the in vivo effectiveness of some 2-, 4-, and 5-nitroimidazoles as hypoxic cell radiosensitizers. A comparison of the in vivo versus the in vitro sensitizing ability of misonidazole and metronidazole indicates some differences, probably due to drug delivery problems in vivo. The relative sensitizing abilities of eight 2-nitroimidazoles, two 4-nigroimidazoles and two 5-nitroimidazoles are compared on the basis of the amount of drug injected and the plasma levels obtained.

Infant botulism. Epidemiological, clinical, and laboratory aspects

Clostridium botulinum organisms and toxin were identified in the feces of six infants, aged 5 to 20 weeks, who had illnesses clinically consistent with botulism. Five of the infants lived in California and became ill within a six-month period in 1976; one infant became ill in New Jersey in 1975. Three cases were type A botulism, and three were type B. No source of ingested botulinal toxin could be found in any case. However, one infant with type B botulism had ingested a food containing C botulinum type B organisms, and no toxin was found in it. The clinical findings in these cases include constipation, weak sucking and crying ability, pooled oral secretions, cranial nerve deficits, generalized weakness, and, on occasion, sudden apnea. A characteristic electromyographic pattern termed "brief, small, abundant, motor-unit action potentials" (BSAP) was observed. The sources of C botulinum toxin for these six infants is thought to have been in vivo (gastrointestinal) production following ingestion of C botulinum organisms. Studies are underway to determine the full clinical spectrum, incidence, and potential public health importance of this infectious disease newly recognized in infants.

Responses of guinea pigs to infections with strains of Venezuelan encephalitis virus, and correlations with equine virulence

Five equine-virulent strains of Venezuelan encephalitis (VE) virus consistently killed guinea pigs (strain English short hair) inoculated subcutaneously, whereas ten equine benign strains did not. Two enzootic eastern Panamanian and Colombian strains of hemagglutination-inhibition antigenic subtype I-D and of undetermined virulence for equine animals also killed guinea pigs. This subtype of VE virus may represent an excpetion to a positive correlation between equine virulence and guinea pig lethality since another strain of ts subtype has been reported to be benign in horses inoculated subcutaneously. Within the strains tested, viruses of subtypes I-ABC and I-D were lethal for guinea pigs, and viruses of other subtypes were benign. There was no correlation between guinea pig and human virulence of VE strains.

Stimulation of erythroblast maturation in vitro by sphingolipids

A lipid factor previously isolated from leukocytes and found to stimulate basophilic erythroblast formation in an in vitro system of incubated rabbit bone marrow cells has been analyzed by thin-layer chromatography, gas-liquid chromatography, and gas-liquid chromatography-mass spectrometry. The biologically active components are sphingosine ceramides of tetracosanoic and dehydrotetracosanoic acids. Tests of a series of related ceramides show a high degree of structural specificity for the C(24)-V-acyl compounds with significant but markedly lower activity of the C(22) analog. Commercially available sphingomyelin shows activity comparable to that of the tetracosanoic acid ceramide. Sphingosine and tetracosanic acid supplied in equimolar amounts have negligible activity. The results, in the context of other findings, suggest a possible supportive role of plasma ceramides and sphingomyelins in red cell maturation.

The epidemiology of influenza in California, 1968-1973

Influenza is one of the most common acute febrile respiratory diseases in adults. Epidemics caused by influenza viruses occur every few years. When such epidemics are in progress, the medical community, the general public and the news media seek information regarding the presence, spread and severity of influenza. The methods and findings of the Influenza Surveillance System in California for the years 1968 through 1973 should be of interest generally. This period spans the total California experience with the type A Hong Kong variant (A/Hong Kong/1/68 [H(3)N(2)]), and the first appearance of the English strain of type A influenza virus (A/England/42/72 [H(3)N(2)]). The surveillance of influenza during this period showed that there were major epidemics in Calfornia only during the state's first experience with the type A Hong Kong variant in 1968-69, and with the English strain in 1972-73. Problems and limitations in influenza surveillance do exist. Nonetheless, the major surveillance indices used (school absenteeism, laboratory data and deaths from pneumonia and influenza) are reliable and sensitive indicators of general trends of influenza virus activity. These indices are most useful in comparing the relative severity of influenza epidemics. However, since these indices usually lag several weeks behind the occurrence of disease, this lag must be considered in making estimates of current incidence trends based on these indices.

Botulism--diagnosis, management and public health considerations

Botulism is an uncommon but often fatal disease associated with ingestion of a potent neurotoxin present in improperly preserved foods. Exposures to commercially preserved foods with an odd or peculiar taste almost never represent exposure to botulism toxin. Improperly prepared home-canned products which are tasted or consumed without heating are more likely to be associated with botulism. The management of suspect and confirmed cases of botulism is presented by medical epidemiologists in the State Department of Public Health, Bureau of Communicable Disease Control, to provide physicians in California with a practical approach to this problem.