Pathogenicity and antibiotic sensitivity of Escherichia coli isolates from non-diarrhoeic dogs.

E. coli isolated from dogs in Trinidad were tested for their susceptibility to antimicrobial agents using the disk diffusion method. Antimicrobial agents and concentrations included cephalothin (KF, 30 ug), ampicillin (AMP, 10ug), kanamycin (K, 30 ìg), neomycin (N, 30 ug), gentamicin (CN, 10 ug), sulphamethoxazole/ trimethoprim (SXT, 23.25 ug/1.75 ug), nalidixic acid (NA, 30 ug) and norfloxacin (NOR, 10 ug). The overall prevalence of resistance to one or more antimicrobial agents for E. coli isolated from dogs was 47.9 per cent. The difference in prevalence across the various sources of the isolates from dogs was statistically significant (P<0.001; x2). Overall, resistance was highest to cephalothin (30.1 per cent). A total of 45 resistance patterns were observed from dogs from all sources and the predominant pattern was KF (25.6 per cent). It was concluded that the relatively high prevalence of resistance to antimicrobial agents amongst E. coli isolates from non-diarrhoeic dogs in Trinidad may pose zoonotic and therapeutic problems.

Occurrence of selected foodborne pathogens on poultry and poultry giblets from small retail processing operations in Trinidad

We conducted a study to determine quantitatively and qualitatively the presence of Campylobacter spp., Escherichia coli, staphylococci, total coliforms, total aerobic bacteria, and Salmonella on broiler carcasses from selected small retail processors in Trinidad. We used standard media and procedures for detection and quantification. All carcass and weep samples were positive for aerobic bacteria, E. coli, total coliforms, and staphylococci. Significant differences in the mean counts of aerobic bacteria were observed for samples of carcass (P = 0.001), weep (P = 0.038), and liver and heart (P = 0.017). There was a significant difference (P < 0.05) in the prevalence of E. coli and Campylobacter for liver and heart samples and gizzard samples across various areas (health divisions) in Trinidad and for Campylobacter jejuni and Campylobacter coli for offal samples. The prevalence of Salmonella in carcass, drip, gizzard, and liver and heart samples was 7.3, 3.1, 2.1, and 1.0%, respectively, and three serotypes, Salmonella Kiambu (53.8%), Salmonella Kentucky (38.5%), and Salmonella Mbandaka (7.7%) were isolated. Of the six groups of microbes considered with respect to sale activity, the differences in the prevalence of Campylobacter in medium-activity sale shops (95.8%) and low-activity sale shops (83.3%) and the mean counts of staphylococci for medium-activity sale shops (5.5 ñ 0.9) and low-activity sale shops (5.1 ñ 0.8) were statistically significant (P < 0.05). Carcasses rinsed in a stagnant system had a significantly higher (P < 0.05) prevalence (92.3%) and mean count per milliliter (3.1 ñ 0.7) for Campylobacter compared with 77.8% and 2.7 ñ 0.7 for shops that rinsed with constantly running water. The frequency of rinse water change significantly (P = 0.04) affected the prevalence of Salmonella on carcasses. It is recommended that a quality control system be introduced for these shops, particularly with respect to evisceration and rinsing practices.

An experimental mouse model to study the pathogenicity of Prevotella bivia and investigations of possible virulence

Induction of subcutaneous abscesses in mice was used to study the pathogenicity of Prevotella bivia both in mono-infection and in mixed cultures with Escherichia coli and Peptostreptococcus spp. Virulence factors such as coaggregation and aggregate formation of cells, haemagglutination activity and tolerance to serum bactericidal activity were investigated for their possible role in P bivia pathogenicity. Monocultures of P bivia, E coli and Peptostreptococcus spp did not induce subcutaneous abscess at concentrations as high as 10 9 colony forming units/millilitre (cfu/ml). Only E coli persisted at the infection site for up to 7 days post infection but with a marked decline in cell count (8.0x10 squaredcfu/ml). The anaerobic organisms did not persist at the infection sites beyond the fifth day. In contrast, mixed cultures of P bivia and E coli or all three organisms potentiated for infective abscess two weeks after infection. Viable cells were recovered from abscesses in greater numbers as the infection progressed. Prevotella bivia was the predominant organism in chronic abscesses while E coli predominated in abscesses in the acute stage of the infection. Prevotella bivia lacked haemagglutination activity against human and sheep erythrocytes and showed marked susceptibility to 50 percent human serum. These may limit its haematogenous spread. Its ability to form aggregates in molar salt solutions and coaggregate with facultative organisms may account for its persistence in pathological sites.(Au)

Search for subtype I strains of Venezuelan encephalitis virus among isolates from Trinidad, W.I., during 1960-1972

Twenty-one strains of Venezuelan encephalitis (VE) virus isolated from three habitats in Trinidad, W. I. during 1960 to 1972, were subtype III (Mucambo) VE cirus by plaque-reduction neutralization tests. Like prototype Mucambo virus, each strain killed 8- to 15-week-old mice inoculated intraperitoneally. If the subtype I strain of VE virus that caused a major outbreak in Trinidad during 1943 to 1944 persisted on the island into the 1960s and early 1970s, it did not become the dominant VE virus in these three enzootic foci (AU)

Immunologic diagnosis of schistosomiasis. III. The effects of nutritional status and infection intensity on intradermal test results in St. Lucian children

The question of the insensitivity of immediate and delayed skin testing in children was studied with respect to both nutritional status and intensity of infection. Ninety-seven children on the island of St. Lucia, 5 to 11 years of age, with almost equal male:female distribution, all excreting eggs of Schistosoma mansoni were tested as follows: qualitatively and quantitative stool examinations; anthropometric measurements (height, weight, mid-arm circumference and triceps skinfold thickness); hematocrit; fluorescent antibody test; and skin tests with control material, S. mansoni adult worm antigen (both Puerto Rican and St. Lucian strains), and intermediate strenght PPD tuberculin. The anthropometric measurements revealed marginal malnutrition among the children. The overall positive intradermal response rate for each of the two antigens was similar, being 56 percent for the immediate and 37 percent for the delayed test. There was no relationship discernible between relative over- and under-nutrition and the skin test responses. A striking and highly significant positive association was revealed, however, between the intensity of infection, as shown by quantitative egg counts, and the sensitivity and extent of both the immediate and delayed skin test reactions.(AU)

A revision of trypanosoma (schizotrypanum) cruzi strains from British Honduras, and the importance of strain characteristics in experimental chemotherapy of Chagas' disease

The characteristics of 10 strains of Trypanosoma cruzi from British Honduras are reviewed and discussed. The strains were isolated from the faeces of wild-caught Triatoma dimidiata and all proved to be highly pathogenic to white mice and rats and to certain species of wild rodents. All the strains were characterized by a high cardiotropism, which did not diminish even after prolonged passage in further animals. A variable degree of neurotropism, characterized by parlysis of the limbs, produced by the strains was observed in many laboratory animal as well as in some of the experimentally infected wild rodents. Histological studies of organs from several of the paralized animals failed to provide definitive clues as to the origin of the paralysis. A wide range of dimorphism was observed in the blood-forms of T. cruzi from each of the isolated strains; this dimorphism and the mean nuclear index number changed during each passage. The morphogenisis of the parasites in tissues, in the insect vector, and in NNN culture medium, was found to include amastigote, sphaeromastigote, epimastigote and transitional trypomastigote forms, all leading to the formation of the infective trypanosome form. The importance of co-ordinated studies on the biological and physiological characteristics of T. cruzi strains from man, animal reservoirs, and triatomine insect vectors, from the regions where Chagas' disease is endemic, is emphasized as one of the fundamental requirements for the experimental chemotherapy of Chagas' disease (AU)

A comparitive study of virulences, plaque morphologies and antigenic characteristics of Venezuelan encephalitis virus strains

Virulences of VE virus strains from tropical regions of the North and South American continents were studied in adult Syrian hamsters, Swiss albino mice and cotton rats. Virulence profiles were based on frequency and time of illness and death following subcutaneous inoculation of small doses of virus as collected in nature or after only a few passages in laboratory hosts. Forty-one strains from Mexico, USA-Florida, Panama, Colombia, and Venezuela uniformity killed hamsters inoculated s.c. with 4-1000 PFU; incubation periods were usually 3-6 days, but some Panamanian and USA-Florida strains had incubation periods 1-2 days longer than strains from other countries. All of 37 strains from these countries regularly produced illness in adult mice, but killed only 71-82 percent; in adult cotton rats, signs of illness were not recognized, but death occurred in 18-30 percent. Variations in virulence profiles for mice and cotton rats among 28 Mexican strains were ogten as great as those seen among 9 strains from USA-Florida, Panama, Colombia and Venezuela. Virus strains from the Bush Bush areas of Trinidad, however, had distinctive virulence profiles. All 5 of these strains killed hamsters only after prolonged incubation periods of more than 5 days, and killed only 1 of 25 mice; neither of two strains killed cotton rats. Young and Johnson reported (Amer. J. Epid., 1969, 89 286-307) that these Trinidad strains should antigenically be classified as Mucambo rather than VE virus. The TC 83 attenuated strain of VE virus in a dose of 500 PFU given s.c. killed no hamsters, mice or cotton rats, but in some experiments employing larger doses, up to 20 percent hamsters became ill and 5-10 percent died without apparent relationship to dose. Plaque sizes and morophologies of 19 VE and 5 Trinidad Mucambo virus strains in primary chicken embryonic cell cultures did not correlate with virulence for hamsters, mice, cotton rats or man, nor with geographic, host or tissue source or year of collection. In sera of cotton rats and mice 3-4 weeks after s.c. inoculation, titers of VE virus HI antibody measured with hemagglutinin from a Mexican virus strain were similar for strains from Mexico, Colombia and Venezuela. However they were lower with USA-Florida and TC 83 virus strains and with Trinidad Mucambo virus strains, suggesting that these viruses differ antigenically from Mexican, Colombian and Venezuelan strains. Nevertheless the attenuated TC 83 vaccine virus protected adult mice against s.c. challenge by 28 Mexican and 8 other VE virus strains from USA-Florida, Panama, Colombia and Venezuela, suggesting that immunologically distinct types of VE virus based on cross-protection do not exist in these countries. (AU)