A comparative study on the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa.

These cross-sectional studies reported the occurrence, genetic characteristics, and factors associated with the distribution of Listeria species on cattle farms and beef abattoirs in Gauteng Province, South Africa. A total of 328 samples (faeces, feeds, silage, and drinking water) were collected from 23 cattle farms (communal, cow-calf, and feedlot), and 262 samples (faeces, carcass swabs, and effluents) from 8 beef abattoirs (low throughput and high throughput) were processed using standard bacteriological and molecular methods to detect Listeria species. The factors associated with the prevalence of Listeria species were investigated, and multiplex polymerase chain reaction (mPCR) was used to determine Listeria species, the pathogenic serogroups, and the carriage of eight virulence-associated genes by Listeria monocytogenes. The overall prevalence of Listeria species in cattle farms was 14.6%, comprising Listeria innocua (11.3%), Listeria monocytogenes (3.4%), Listeria welshimeri (0.0%) compared with 11.1%, comprising Listeria innocua (5.7%), Listeria monocytogenes (4.6%), Listeria welshimeri (0.8%) for beef abattoirs. Of the three variables (area, type of farm/abattoir, and sample type) investigated, only the sample types at abattoirs had a significant (P < 0.001) effect on the prevalence of L. innocua and L. welshimeri. The frequency of distribution of the serogroups based on 11 L. monocytogenes isolated from farms was 72.7% and 27.3% for the serogroup 1/2a-3a and 4b-4d-4e, respectively, while for the 12 L. monocytogenes isolates recovered from abattoirs, it was 25%, 8.3%, 50% and 16.7% for the serogroup 1/2a-3a, 1/2b-3b, 1/2c-3c, and 4b-4d-4e respectively (P < 0.05). All (100%) isolates of L. monocytogenes from the farms and abattoirs were positive for seven virulence genes (hlyA, inlB, plcA, iap, inlA, inlC, and inlJ). The clinical and food safety significance of the findings cannot be ignored.

Seroepidemiology of Leptospira infection in slaughtered cattle in Gauteng province, South Africa.

Leptospirosis is an important economical disease of livestock globally, especially in Asia, the Caribbean, and the African continent. Its presence has been reported in a wide range of livestock. However, information on leptospirosis in South Africa is scanty. We conducted a cross-sectional study in 11 randomly selected abattoirs to determine the seroprevalence and risk factors for leptospirosis in slaughtered cattle in Gauteng province, South Africa. During abattoir visits to selected abattoirs, blood samples were collected from 199 cattle and demographic data obtained on the slaughtered animals. The microscopic agglutination test (MAT) was performed on all sera using a 26-serotype panel using cutoff titer ≥ 1:100. Animal- and abattoir-level risk factors were investigated for their association with seropositivity for leptospirosis. The seroprevalence of leptospirosis in the cattle sampled was 27.6% (55/199). The predominant serogroups detected in seropositive cattle were Sejroe (sv. Hardjo) (38.2%) and Mini sv. Szwajizak) (14.5%) but low to Canicola (sv. Canicola) (1.8%) and Pomona (sv. Pomona) (1.8%). The differences were statistically significant (P < 0.05). Of the five variables investigated, only one (abattoirs) had statistically significantly (P < 0.001) differences in the seroprevalence of leptospirosis among abattoirs. The study documented for the first time in South Africa, the occurrence of serogroups Sejroe (Hardjo bovis strain lely 607), Tarassovi, Hebdomadis, and Medanensis in slaughtered cattle. It was concluded that six of the nine serovars (representing seven serogroups) of Leptospira spp. circulating in cattle population in South Africa are not vaccine serogroups. The clinical, diagnostic, and public health importance of the findings cannot be ignored.

Occurrence and genetic relatedness of Listeria spp. in two brands of locally processed ready-to-eat meats in Trinidad.

Contamination of locally produced, ready-to-eat meats by Listeria spp. has been previously reported at one processing plant in Trinidad. However, the status of this pathogen in locally produced products sold at retail outlets is unknown. This study was conducted to establish whether there is a risk to consumers of locally processed meats caused by the presence of Listeria spp., and whether a link exists between the presence of the pathogen in retail products and the manufacturing plant of one brand (B). Four hundred and eighty ready-to-eat meat products of two popular local brands (A and B) were collected from retail outlets and analysed for the presence of Listeria spp. together with food samples and surfaces from one manufacturing plant (B). Eighty-eight of the retail products (18·3%) were contaminated with Listeria spp., of which, 52·3% were L. innocua, 44·3% were L. monocytogenes and 3·4% belonged to the L. seeligeri-L. welshimeri-L. ivanovii (Siwi) group. L. innocua was found in 15 in-process food samples and on three surfaces of equipment at plant B. Four in-process food samples were also contaminated with Siwi isolates. Repetitive extragenic palindromic PCR DNA fingerprinting showed a possible association between strains of different Listeria spp. and brand as well as with manufacturing plant B.

Serovars of Leptospira isolated from dogs and rodents.

We determined the frequency of isolation of Leptospira from dogs and rodents, the serovars of Leptospira, and the clinical, gross and histological manifestations in dogs with leptospirosis in Trinidad. From dogs, samples of urine, blood and kidney were collected while only kidney and blood samples of trapped rodents were used. Isolates were cultured and serotyped using a panel of 23 international serovars and monoclonal antibodies. The risk factors for leptospirosis were also determined in owned dogs using a standard questionnaire. Of a total of 468 animals investigated for Leptospira, 70 (15.0%) were positive, comprising nine (18.0%) of 50 suspected canine leptospirosis cases, seven (3.4%) of 207 stray dogs and 54 (25.6%) of 211 rodents. The observation that rodents have a statistically (P<0.05, chi2) higher frequency of isolation emphasizes the importance of rodents as reservoirs of leptospirosis in the country. Copenhageni was the predominant serovar found in 100.0% (7/7), 33.3% (2/6) and 68.5% (37/54) of isolates from suspected canine leptospirosis cases, stray dogs and rodents, respectively. Serovars Icterohaemorrhagiae and Canicola, the two serovars present in the commercial vaccines used locally, were detected in one (1.5%) and zero (0.0%) isolates respectively of the 67 tested. Data provided suggest that the apparent vaccine failure may be a consequence of the fact that the predominant serovar (Copenhageni) detected in sick, apparently healthy dogs and in rodents is not contained in the vaccines used locally to protect dogs against canine leptospirosis.

Serological evidence of widespread exposure of Grenada fruit bats to chikungunya virus.

Antibody detection against selected potentially zoonotic vector-borne alphaviruses and flaviviruses was conducted on sera from bats from all six parishes in Grenada, West Indies. Sera were tested for (i) antibodies to flaviviruses West Nile virus, St. Louis encephalitis virus, Ilhéus virus, Bussuquara virus (BSQV), Rio Bravo virus and all four serotypes of dengue virus (DENV) by plaque reduction neutralization test (PRNT); (ii) antibodies to alphaviruses western equine encephalitis virus, Venezuelan equine encephalitis virus and eastern equine encephalitis virus by epitope-blocking enzyme-linked immunosorbent assay (ELISA); and (iii) antibodies to the alphavirus chikungunya (CHIKV) by PRNT. Two species of fruit bats were sampled, Artibeus jamaicensis and Artibeus lituratus, all roosting in or within 1,000 m of human settlements. Fifteen (36%) of the 42 bats tested for neutralizing antibodies to CHIKV were positive. The CHIKV-seropositive bats lived in localities spanning five of the six parishes. All 43 bats tested for epitope-blocking ELISA antibody to the other alphaviruses were negative, except one positive for Venezuelan equine encephalitis virus. All 50 bats tested for neutralizing antibody to flaviviruses were negative, except one that had a BSQV PRNT80 titre of 20. The CHIKV serology results indicate that bats living close to and within human settlements were exposed to CHIKV in multiple locations. Importantly, bats for this study were trapped a year after the introduction and peak of the human CHIKV epidemic in Grenada. Thus, our data indicate that bats were exposed to CHIKV possibly during a time of marked decline in human cases.

Post-exposure serological and bacteriological responses of water buffalo (Bubalus bubalis) to Brucella abortus biovar 1 following vaccination with Brucella abortus strain RB51.

Serological and bacteriological responses to Brucella abortus biovar 1 following vaccination with B. abortus strain RB51 (RB51) were evaluated in thirty domestic water buffalo (Bubalus bubalis) randomly divided into five treatment groups. Groups I to V received, respectively, the recommended dose (RD) of RB51 vaccine once, RD twice 4 weeks apart, double RD once, double RD twice 4 weeks apart, and saline once (control). Vaccination did not result in a serological response. Experimental animals released 27 weeks post initial inoculation (27 PIIW) into a brucellosis-positive herd failed to seroconvert after 29 weeks. Experimental challenge commenced at 57 PIIW. All animals received B. abortus biovar 1 intraconjunctivally at 0, 5 and 9 weeks post experimental exposure (PEEW). Serum samples collected at 4, 8 and 13 PEEW were negative. At 16 PEEW all animals received B. abortus biovar 1 subcutaneously (SC), and all seroconverted by 20 PEEW. Five of twenty-six animals were positive for Brucella infection on bacterial culture. Brucella abortus biovar 1 was isolated from three animals; B. abortus RB51 was isolated from two. Treatment group, age and sex had no effect on the isolation of Brucellae (P>0.05).

Congenital toxoplasmosis in two health institutions in Trinidad.

Toxoplasmosis is the most widespread zoonosis and an important human disease particularly in children where it could cause visual and neurological impairment and mental retardation. This study was conducted to determine the prevalence of toxoplasmosis, especially congenital toxoplasmosis in patients at two health institutions in Trinidad A total of 504 cord blood samples of newborn babies were collected: 174 from a women's hospital and 330 from a general hospital. In order to elicit aternal and prenatal risk factors for toxoplasmosis, mothers of the newborns completed a questionnaire. Enzyme-immuno assay (EIA) was used to detect IgG and IgM to Toxoplasma gondii. Overall, of 504 serum samples tested, 220 (43.7%) were seropositive for IgG while the prevalence of congenital toxoplasmosis as reflected by IgM was 0.4%. The prevalence of IgG and IgM by health institutions was not significantly different (p > 0.05; chi-square). The prevalence of toxoplasmosis using IgG was highest in neonates of mothers who were of East Indian descent (54.1%), had four children (52.9%), kept cats in households (47.7%), practised outdoor gardening (50.8%), consumed raw meat (66.7%), had experienced miscarriage(s) (47.3%), stillbirths (66.7%), or who had eye problem(s) (52.9%) and mental retardation (50.0%). The study prevalence of congenital toxoplasmosis revealed a high seroprevalence oftoxoplasmosis in neonates but there was 0.4% serological evidence of congenital disease. It indicates a need for sensitization of the population and healthcare workers and for follow-up of infected children for clinical evidence of the disease. This would be necessary to fully appreciate the impact of toxoplasmosis in Trinidad and Tobago. The differences from comparison groups were however not statistically significant (p > 0.05; chi-square).

Serologic responses, biosafety and clearance of four dosages of Brucella abortus strain RB51 in 6-10 months old water buffalo (Bubalus bubalis).

Thirty water buffalo were obtained from a brucellosis-free farm in order to evaluate antibody responses, bacterial clearance and safety to Brucella abortus strain RB51 vaccine in a dose response study. The animals were randomly divided into five treatment groups. Groups I-V received the recommended dose of RB51 vaccine (RD) once, RD twice 4 weeks apart, double RD once, double RD twice 4 weeks apart and saline once, respectively. Antibody responses to RB51 were monitored at 2, 4, 6, 8, 10, 12, 16 18, 22, 24 and 27 post-initial-inoculation weeks (PIW). Clearance of RB51 from the prescapular lymph node was evaluated at 2, 4, 6, 12, 18 and 24 PIW for groups 1, III and V and at 6, 8, 10, 16, 22 and 27 PIW for groups II and IV. To evaluate shedding of the RB51 strain, nasal, conjunctival, vaginal or preputial swabs were taken from all experimental animals at 1, 2, 3, 4, 6, 8 and 12 PIW. Sera taken at all PIW were negative for field strain B. abortus by both the buffered plate agglutination test (BPAT) and competitive enzyme-linked immunosorbent assay (c-ELISA). Antibody responses to RB51 were demonstrated in all vaccinates but not in the controls, up to 12 PIW, by complement fixation test (CFT) and the dot-blot assay with an 83.7% agreement for both tests. Clearance of RB51 occurred between 6 and 12 PIW in group I but less than 2 weeks after booster vaccinations in groups II and IV and between 4 and 6 PIW in group III. RB51 was not recovered at any time from swabs obtained from either RB51-vaccinates or non-vaccinates. The results of this study indicate that serologic responses to RB51 vaccination can be monitored by both CFT and dot-blot assay in water buffalo. Our data also indicates that RB51 vaccination does not interfere with brucellosis sero-surveillance and is safe (no serological and bacteriological evidence of spread to non-vaccinates, no adverse clinical signs or detectable abnormalities on haematology and serum biochemistry) for use in water buffalo.

Ear-tag retention and identification methods for extensively managed water buffalo (Bubalus bubalis) in Trinidad.

Thirty-two young domestic water buffalo were studied to evaluate ear-tag retention during an epidemiologic field trial. Plastic ear-tags were placed in both ears before the start of the trial, which was implemented in an extensively managed domestic water buffalo herd of approximately 1000 animals in Trinidad from 1999-2001. The presence or absence of ear-tags was recorded at the times of animal handling. The rate of ear-tag loss was modeled using a parametric survival analysis assuming an exponential rate of loss. A gamma distribution was used to estimate the amount of time that each animal would be positively identified based only on the presence or absence of one or more ear-tags. The overall median ear-tag retention was 272 days. The estimated rate of ear-tag loss was 0.0024 ear-tags lost per day. The use of ear-tags alone might not be sufficient for long-term identification of extensively managed animal populations.

Likelihood ratio estimation without a gold standard: a case study evaluating a brucellosis c-ELISA in cattle and water buffalo of Trinidad.

The likelihood ratio (LR) is a measure of association that quantifies how many more times likely a particular test result is from an infected animal compared to one that is uninfected. They are ratios of conditional probabilities and cannot be interpreted at the individual animal level without information concerning pretest probabilities. Their usefulness is that they can be used to update the prior belief that the individual has the outcome of interest through a modification of Bayes' theorem. Bayesian analytic techniques can be used for the evaluation of diagnostic tests and estimation of LRs when information concerning a gold standard is not available. As an example, these techniques were applied to the estimation of LRs for a competitive ELISA (c-ELISA) for diagnosis of Brucella abortus infection in cattle and water buffalo in Trinidad. Sera from four herds of cattle (n=391) and four herds of water buffalo (n=381) in Trinidad were evaluated for Brucella-specific antibodies using a c-ELISA. On the basis of previous serologic (agglutination) test results in the same animals, iterative simulation modeling was used to classify animals as positive or negative for Brucella infection. LRs were calculated for six categories of the c-ELISA proportion inhibition (PI) results pooled for cattle and water buffalo and yielded the following estimations (95% probability intervals): <0.10 PI, 0.05 (0-0.13); 0.10-0.249 PI, 0.11 (0.04-0.20); 0.25-0.349 PI, 0.77 (0.23-1.63); 0.35-0.499 PI, 3.22 (1.39-6.84); 0.50-0.749 PI, 17.9 (6.39-77.4); > or =0.75 PI, 423 (129-infinity). LRs are important for calculation of post-test probabilities and maintaining the quantitative nature of diagnostic test results.

Evaluation of cell-mediated immune responses and bacterial clearance in 6-10 months old water buffalo (Bubalus bubalis) experimentally vaccinated with four dosages of commercial Brucella abortus strain RB51 vaccine.

Thirty water buffalo, obtained from a brucellosis-free farm, were used to evaluate cell-mediated immune responses and bacterial clearance in response to vaccination with Brucella abortus strain RB51 (RB51) in a dose-response study. The animals were randomly divided into five treatment groups. Groups I--V received the recommended dose (RD) of RB51 vaccine once, RD twice 4 weeks apart, double RD once, double RD twice 4 weeks apart and saline once, respectively. Cell-mediated immune response to RB51 was assessed by the histological examination of haematoxylin and eosin (H&E) stained sections of lymph nodes draining the sites of inoculation and by comparison of stimulation indices (SI) derived from gamma interferon (IFN-gamma) assay. A mixture of cytoplasmic proteins from B. melitensis B115 (brucellergene) was used as a specific antigenic stimulus to peripheral blood mononuclear cells (PBMC) and lymph node mononuclear cells (LNMC) up to 22 post-initial-inoculation week (PIW). Supernatants harvested at 18-24h after the in vitro antigenic stimulus were assayed for their IFN-gamma content by using a commercial sandwich enzyme-linked immunosorbent assay (ELISA) kit. Clearance of RB51 was assessed by the sequential immunohistochemical examination of sections of draining lymph nodes post-inoculation. There was no observable expansion of the deep cortex of lymph nodes on H&E sections indicating poor T-cell stimulation. All group V (control) water buffalo PBMC ELISA values were negative (SI<2.2) at all PIW sampling intervals. Overall PBMC IFN-gamma assay detected vaccinates from treatment groups' I--IV 67% (4/6), 83% (5/6), 33% (2/6) and 67% (4/6), respectively. LNMC IFN-gamma assay was unimpressive and there was a negative correlation (--.08) between the results of PBMC and LNMC of IFN-gamma assay. Clearance of RB51 occurred between 4 and 6 PIW in treatment groups I and III and between 6 and 12 PIW in groups II and IV. RB51 was not detected in any of the control animals at sampling intervals post-inoculation.

Seroprevalence of Legionella pneumophila in pneumonia patients in four major hospitals in Trinidad and Tobago.

Trinidad and Tobago is an island-state in the Caribbean with a size of 5,128 square kilometers and a population of 1.3 million. Pneumonia is a leading cause of death in Trinidad. This project determined the frequency of Legionella pneumophila in patients with pneumonia, investigated the relationship between pneumonia and selected risk factors. Serum and demographic data were collected from 123 patients, diagnosed with pneumonia. Sera were tested for L pneumophila Ig G/M/A and IgM. All analyses were done using the SPSS statistical package. Of a total of 123 serum samples tested, 39 (31.7) were positive for L pneumophila IgM/G/A while 2 (1.6%) were positive for IgM only. Hospitals, gender and ethnicity did not significantly (p > 0.05; chi-squared) affect the seroprevalence of L pneumophila. Overall, the prevalence of L pneumophila assayed was not significantly (p > 0.05, chi-squared) affected by co-morbidities.

Antimicrobial susceptibility of Leptospira isolates from dogs and rats to 12 antimicrobial agents.

This study determined the antimicrobial susceptibilities of 67 isolates of Leptospira from dogs (suspect canine cases: n=7 and stray dogs: n=6) and rodents (n=54) in Trinidad to 12 antimicrobial agents using broth microdilution and macrodilution techniques. Commonly used antimicrobial agents such as the penicillin G and ceftriaxone had relatively low minimal inhibitory concentrations (MICs) while doxycycline displayed a relatively higher value but was still considered to be effective. While imipenem was the most effective with low MIC values in vitro, sulphamethoxazole-trimethoprim had the highest i.e. least effective. Based on these results, the drugs commonly used in the treatment of leptospirosis (penicillin G, penicillin-streptomycin, doxycycline and ceftriaxone) in both humans and animals in Trinidad appear to have similar MICs and MBCs in vitro when compared with published reports. The serovar of Leptospira spp. and in most cases the origin of the isolates did not significantly (P>0.05) influence their susceptibilities to the antimicrobial agents tested.

Seroepidemiology of selected alphaviruses and flaviviruses in bats in Trinidad.

A serosurvey of antibodies against selected flaviviruses and alphaviruses in 384 bats (representing 10 genera and 14 species) was conducted in the Caribbean island of Trinidad. Sera were analysed using epitope-blocking enzyme-linked immunosorbent assays (ELISAs) specific for antibodies against West Nile virus (WNV), Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV), all of which are zoonotic viruses of public health significance in the region. Overall, the ELISAs resulted in the detection of VEEV-specific antibodies in 11 (2.9%) of 384 bats. Antibodies to WNV and EEEV were not detected in any sera. Of the 384 sera, 308 were also screened using hemagglutination inhibition assay (HIA) for antibodies to the aforementioned viruses as well as St. Louis encephalitis virus (SLEV; which also causes epidemic disease in humans), Rio Bravo virus (RBV), Tamana bat virus (TABV) and western equine encephalitis virus (WEEV). Using this approach, antibodies to TABV and RBV were detected in 47 (15.3%) and 3 (1.0%) bats, respectively. HIA results also suggest the presence of antibodies to an undetermined flavivirus(es) in 8 (2.6%) bats. Seropositivity for TABV was significantly (P<0.05; χ2) associated with bat species, location and feeding preference, and for VEEV with roost type and location. Differences in prevalence rates between urban and rural locations were statistically significant (P<0.05; χ2) for TABV only. None of the aforementioned factors was significantly associated with RBV seropositivity rates.

Bacteriological quality and associated public health risk of pre-processed bovine milk in Trinidad.

The bacteriological quality of pre-processed raw milk originating from all 16 milk collection centres in Trinidad was evaluated. The mean total aerobic counts for bacteria, Staphylococcus aureus and Escherichia coli were determined. The pH and presence of somatic cells in milk were also determined. Of the 507 milk samples collected, 454 (89.5%) were California mastitis test (CMT)-positive and the mean pH was 6.50 +/- 0.13. The total aerobic plate count per ml was generally high for all samples ranging from 5.8 x 10(5) +/- 3.1 x 10(5) to 5.7 x 10(8) +/- 1.5 x 10(9). S. aureus was isolated from 478 (94.3%) samples and the mean counts per ml ranged from 1.5 x 10(5) +/- 1.1 x 10(5) to 9.4 x 10(5) +/- 1.3 x 10(6). Nine (7.7%) of 117 strains of S. aureus produced staphylococcal enterotoxins A(SEA), B(SEB), D(SED) or a combination. E. coli was isolated from 105 (20.7%) samples and the mean counts per ml ranged from 6.6 x 10(2) +/- 1.1 x 10(2) to 4.0 x 10(5) +/- 4.6 x 10(5). Twenty-five (23.6%) of the 106 strains of E. coli tested produced verocytotoxin (VT) but none was positive for heat-labile (LT) toxin. It was concluded that pre-processed milk in Trinidad is of poor bacteriological quality. The detection of high counts of S. aureus in milk with some producing heat stable enterotoxins, coupled with the isolation of some verocytotoxigenic E. coli, are of public health significance to consumers.

Microbiological analysis of 'black pudding', a Trinidadian delicacy and health risk to consumers.

The prevalences of Salmonella, Escherichia coli and Staphylococcus aureus in black pudding which originated from local vendors and supermarkets in Trinidad were determined. The enterotoxigenicity of S. aureus strains and occurrence of O157:H7 strains amongst E. coli isolates were also investigated. For the 100 black puddings each sampled from supermarkets and vendors, the mean total aerobic plate count (TAPC) per g was 1.8 x 10(7) +/- 1.5 x 10(7) and 1.5 x 10(8) +/- 2.3 x 10(8), respectively. E. coli was isolated from 56 (56.0%) black pudding samples from supermarkets with a mean count per g of 9.2 x 10(6) +/- 7.9 x 10(6) compared to a prevalence of 79% (79 of 100) and mean count per g of 3.2 x 10(7) +/- 4.7 x 10(7) for samples from local vendors. The difference between prevalences was statistically significant (P < or = 0.001; chi 2). Only 1 (2.2%) of 45 strains of E. coli from supermarket-purchased pudding tested, was an 0157:H7 strain compared to 9 (13.6%) of 66 strains of E. coli from vendor-sold black pudding. The difference was not statistically significant (P > or = 0.05; chi 2). Five (5.0%) of 100 black pudding samples from supermarkets yielded Salmonella, with S. ohio being the predominant serotype. For vendor-sold black pudding however, 11 (11.0%) samples were positive for Salmonella with a new serotype, S. unnamed (4,12:d-) being responsible for 50% (6 of 12) of isolates from this source. Forty samples each of black pudding from supermarkets and vendors were all (100.0%) positive for S. aureus with mean counts per g being 3.1 x 10(5) +/- 8.8 x 10(5) and 3.3 x 10(6) +/- 7.7 x 10(6), respectively. Overall, 27 (33.8%) of 80 strains of S. aureus tested were enterotoxigenic producing staphylococcal enterotoxins A(SEA), SEB, SEC, SED or a combination. It was concluded that black pudding poses a high risk to consumers based on the prevalence, microbial load and toxigenicity of the pathogens detected.

The occurrence of Staphylococcus aureus in fermented milk products (fura and manshanu) in Nigeria.

Ninety-three samples of fermented milk cereal (Fura) and 79 of local butter (Manshanu) were collected from four different markets around Zaria. For Fura the mean content of Staphylococci for each of the four markets ranged from 4.5 x 10(3) to 4.3 x 10(4) cfu/ml and the mean aerobic mesophilic plate count from 5.6 x 10(5) to 2.7 x 10(6) cfu/ml. For Manshanu the mean staphylococcal count and aerobic mesophilic plate count ranged from 3.4 x 10(2) to 2.2 x 10(3) cfu/ml and 6.7 x 10(4) to 1.1 x 10(6) cfu/ml respectively. Significant differences were seen between the different markets.

Microbial quality of domestic and imported brands of bottled water in Trinidad.

A cross-sectional study was conducted to determine the microbial quality of domestic and imported brands of bottled water available in Trinidad, purchased from six geographical regions in Trinidad, and representing the whole island. A sample size of 344 bottles of water was determined by using a precision rate of 2% and a Type 1 error of 5%. The membrane filter technique was used with cultures grown on m-Endo agar and m-FC agar for total coliforms and thermotolerant coliforms, respectively. Aerobic plate count (APC) was determined on nutrient agar; Pseudomonas aeruginosa was detected on MacConkey agar, Escherichia coli was isolated on eosin methylene blue (EMB) and Salmonella spp. was assayed by using standard methods. Of the 344 water samples tested, 262 (76.2%) and 82 (23.8%) were domestic and imported brands, respectively. Eighteen (5.2%) of the 344 samples contained coliforms with a mean count of 0.88+/-6.38 coliforms per 100 ml, while 5 (1.5%) samples contained E. coli. The prevalence of total coliforms in domestic brands of bottled water was 6.9% (18 of 262) as compared with 0.0% (0 of 82) detected in imported brands. The difference was statistically significant (p=0.004). Similarly, the prevalence of aerobic bacteria in domestic brands of bottled water (33.6%) was significantly higher (p=0.001) than was found in imported brands (14.8%). Twenty-six (7.6%) of the total samples of water contained Pseudomonas species, but all were negative for thermotolerant coliforms and Salmonella spp. It was concluded that based on the recommended zero tolerance for coliforms in potable water, 5% of bottled water sold in Trinidad could be considered unfit for human consumption.

Bacteriological quality of raw oysters in Trinidad and the attitudes, knowledge and perceptions of the public about its consumption.

In Trinidad and Tobago, raw oyster cocktails are a delicacy, but they are generally believed to be responsible for illness in the consumer. The microbial loads of raw oysters, condiments/spices and ready-to-consume oyster cocktails were determined in four sampling areas. Questionnaires were also administered to 72 oyster vendors to determine practices that affect the bacteriological quality of the products. Three hundred members of the public were interviewed to determine the attitudes, knowledge and perceptions of the public about raw oyster consumption. The mean total aerobic plate count (TAPC) per g of 50 samples each, of raw oysters, condiments/spices and ready-to-consume raw oyster cocktails averaged from 1.0 x 10(7)+/-4.3 x 10(7) to 1.4 x 10(8)+/-6.4 x 10(8), 2.0 x 10(5)+/-1.0 x 10(6) to 2.0 x 10(7)+/-1.4 x 10(8), and 4.3 x 10(5)+/-1.0 x 10(6) to 2.2 x 10(6)+/-1.0 x 10(7), respectively. The difference for each product among the four areas was statistically significant (P < or = 0.05; chi2). Using a recommended maximum standard of TAPC per g of 5.0 x 10(5), 115 (57.5%), 27 (13.5%) and 51 (25.5%) of 200 samples each, of raw oysters, condiments/spices and oyster cocktails, respectively, were considered unfit for human consumption. Amongst vendor practices, source of oyster harvest and length of time between separation of oyster meat from shell and sale, significantly affected the mean TAPC per g and the prevalence of unfit oyster cocktail samples. Consumption of raw oyster cocktails was more prevalent amongst males (73.6%) than females (26.4%) (P < 0.002), East Indians (63.2%) as compared with other respondents (36.8%) (P < 0.001), individuals < or = 40 years old (82.1%) than in individuals > 40 years of age (17.9%) (P < 0.01), and in individuals who were aware that raw oysters are considered to be a sexual enhancer (86.8%) as compared to those who did not have this perception (11.3%) (P < 0.03). Fear of falling ill prevented 44 (37.9%) of 116 non-consumers from eating oyster cocktails, while 13 of 106 consumers (12.3%) reported having experienced an oyster-borne illness. The rather high prevalence of raw oyster cocktails found to be unfit for human consumption, coupled with the perceptions and attitudes of the consumers about the product, pose a significant health risk to the public.

Isolation of enterotoxigenic strains of staphylococci from dogs.

The ability of 309 staphylococcal isolates from household dogs to produce enterotoxin, coagulase, thermonuclease and hemolysin was investigated. A total of 52 (16.8%) isolates from 45 out of 150 dogs examined were enterotoxigenic when tested for enterotoxin types A, B and C. Based on sites sampled, 33 (20.5%) out of 161 isolates from the anterior nares were enterotoxigenic while from dorsal skins 19 (12.8%) out of 148 isolates were enterotoxigenic. Staphylococcal enterotoxin C(SEC) was predominantly produced as 21 (6.8%) isolates elaborated it and also accounted for 40.4% of all enterotoxins produced by isolates. Staphylococcal enterotoxins A(SEA) and B(SEB) were produced by 10 (3.2%) and 16 (5.2%) strains, respectively. Mixed enterotoxin types AB, AC and BC were produced by 1,3 and 1 strains, respectively. With human plasma, 17.1% of coagulase-positive and 15.0% of coagulase-negative strains were enterotoxigenic. However, using canine plasma, 19.1% and 6.9% of the coagulase-positive and negative isolates, respectively, were enterotoxigenic. The incidence of enterotoxigenicity was 16.9% amongst thermonuclease-positive isolates and 16.3% for thermonuclease-negative strains. Alpha hemolysin was predominantly produced by 180 (60.2%) isolates and 19.9% of these were enterotoxigenic. Beta hemolysin was produced by 36 (11.7%) isolates with 13.9% enterotoxigenic, while 87 (28.2%) exhibited gamma hemolytic pattern amongst which 11.5% were enterotoxigenic. Based on data provided on coagulation of human and canine plasmas and hemolytic patterns, it is concluded that a large proportion of canine isolates from this environment are not of canine biotypes, but are most probably human biotypes.