Escherichia coli contamination of lettuce sold at markets in Trinidad: A preliminary study

Objective: Historically most foodborne disease outbreaks have been attributed to animal products but recently the number of cases associated with vegetable produce has been increasing. Most of these microbial foodborne pathogens are also part of the resident gut flora of many animals and can be shed asymptomatically in the environment. Leafy greens contamination with these pathogens are of particular concern since they are consumed uncooked. Using Escherichia coli (E. coli) as an indicator of faecal contamination, we evaluated lettuce as a potential source of foodborne disease. Design and Methodology: A cross-sectional study was carried out targeting six retail markets in Trinidad. At each market, a total of 15 lettuce samples were purchased from five retailers. The E. coli colony forming units per gram (CFU/g) of lettuce were then assessed using standard laboratory techniques. Results: All farmers surveyed reported using pipe-borne water as their primary source of irrigation water. E. coli was present in all samples. Overall, the E. coli counts ranged from 0.8 to 80,000 CFU/gram. The lettuce E. coli counts varied with location (p=0.01) and was highest in San Fernando (3.4 ± 1.1 Log10CFU/g) and lowest in Marabella (1.5 ± 0.65 Log10 CFU/g). Interestingly, lettuce farms using manure had lower E. coli counts than those not using manure (2.88 ± 1.3 Log10 CFU/g vs 2.27±1.23 Log10 CFU/g; p=0.07.) Conclusion: These high E.coli counts are indicative of either preharvest or post-harvest faecal contamination of lettuce. The high level of E. coli contamination of lettuce being sold at market should be of serious concern since this a potential risk to public health.

Genetic diversity and relatedness of uropathogenic Escherichia Coli with non-clinical isolates in Grenada

OBJECTIVE: To compare genetic profiles of uropathogenic E.coli (UPEC) to strains isolated from freshwater, seawater and iguanas in Grenada. DESIGN AND METHODS: Eighty-five E. coli strains were isolated using double streak-plating on eosin methylene blue (EMB) and MacConkey agar from human urine, iguanas, fresh and marine water. Species identification was confirmed using API20E. Genomic DNA was extracted from individual pure cultures of E. coli and amplified using the oligonucleotide (GTG5) and BOX primers. The DNA fingerprints were separated by electrophoresis, normalized using reference American Test Culture collection (ATCC) E.coli and compared using DendroUPGMA, the FigTree™, dominance and co-clustering analyses. RESULTS: Both DNA fingerprinting methods targeted extragenic DNA and demonstrated enormous intra-species diversity within the population of studied 85 E. coli isolated from four major eco-habitats. DNA fingerprinting based on BOX-PCR was less discriminating than the (GTG)5-PCR. The BOX analysis correlated better with the ecotype distribution. The combination of dominance and co-clustering analyses allowed us to trace the relatedness of strains among and between the four different ecotypes. CONCLUSIONS: The (GTG5) PCR based co-clustering analysis indicated that the clinical isolates had a closer relationship to iguana E. coli isolates than to fresh and marine water isolates. However, in accordance with the BOX analysis, clinical isolates were most similar to marine, followed by freshwater and iguanas.

Frequency of detection of Escherichia coli, Salmonella spp., and Campylobacter spp. in the faeces of wild rats (Rattus spp.) in Trinidad and Tobago

The study was conducted to determine the frequency of isolation of Salmonella, Campylobacter and E. coli O157 in the faecal samples of rats trapped across the regional corporations in Trinidad and to assess their resistance to antimicrobial agents. A total of 204 rats were trapped for the detection of selected bacteria. Standard methods were used to isolate Salmonella, Campylobacter and E. coli O157. Characterization of E. coli was done on sorbitol MacConkey agar to determine non-sorbitol fermentation, blood agar to determine haemolytic and mucoid colonies and by using E. coli O157 antiserum to determine O157 strain. The disc diffusion method was used to determine resistance to nine antimicrobial agents. Of the 204 rats, 4 (2.0%), 7 (3.4%) and 171 (83.8%) were positive for Salmonella spp., Campylobacter spp. and E. coli, respectively. Of the 171 isolates of E. coli tested 0 (0.0%), 25 (14.6%) and 19 (11.1%) were haemolytic, mucoid and non-sorbitol fermenters, respectively. All isolates were negative for the O157 strain. The frequency of resistance to the 9 antimicrobial agents tested was 75% (3 of 4) for Salmonella, 85.7% (6 of 7) of Campylobacter spp. and 36.3% (62 of 171) for E. coli (P < .05; χ(2)).

Phenotypic detection and occurrence of extended-spectrum beta-lactamases in clinical isolates of Klebsiella pneumoniae and Escherichia coli at a tertiary hospital in Trinidad & Tobago.

The incidence and distribution of ESBL producing microorganisms such as E. coli and K. pneumoniae have been demonstrated and varies in different health care facilities and as well as other countries This study was carried out to determine the frequency of occurrence and the antimicrobial susceptibility pattern of ESBL producing E. coli and K. pneumoniae species from clinical isolates at a tertiary hospital in Trinidad & Tobago. Standard microbiological procedures and automated MicroScan System was used to identify, screen for putative ESBL production and determine antimicrobial susceptibility of 1,118 clinical isolates of Enterobacteriaceae species at the microbiology laboratory of the Eric Williams Medical Science Complex, Trinidad & Tobago over a 36 months period. All ESBL producing isolates flagged by the automated system were further confirmed by E-test method. The E-test confirmed a 15.2 per cent ESBL rate among the K. pneumoniae isolates and 9.3 per cent among the E. coli isolates. There was also a 1.8 per cent rate of ESBL production in K. pneumoniae and 0.2 per cent in E. coli isolates from specimens received from community health facilities into the laboratory. Isolates recovered from the intensive care unit of the hospital had 2.1 per cent E. coli and 8.2 per cent K. pneumoniae ESBL producers. Although all ESBL positive isolates were completely susceptible to imipenem and meropenem; and all positive K. pneumoniae isolates were susceptible to amikacin, there was a low susceptibility of ESBL positive E. coli to the aminoglycosides. However, susceptibility of these ESBL producing isolates to the fluoroquinolones varied. There is a high rate of ESBL production among isolates of E. coli and K. pneumoniae at this hospital that is linked to the extensive inappropriate use of third generation cephalosporins in the country. Further molecular studies are needed to characterize the types of these ESBL prevailing in the country.

Isolation of Aerococcus viridans from an outbreak of hepatitis in a broiler flock in Grenada

Five week-old broiler chickens from an outbreak of bacterial hepatitis on a poultry farm in Grenada were examined. The predominant gross lesions included multiple pinpoint light yellow foci in the liver, moderate splenomegaly, and ulcerative pododermatitis. The hepatic lesions were characterised by multifocal necrotising hepatitis with intralesional bacterial colonies. Culture of the liver lesions yielded a heavy growth of Aerococcus viridans and a moderate growth of Escherichia coli. The A. viridans isolates showed typical biochemical properties, susceptibility to vancomycin, and moderate resistance to aminoglycoside antibiotics. It appears that dual infection with A. viridans and E. coli caused hepatitis in these chickens which had earlier history of coccidiosis.

Isolation of Aerococcus viridans from an outbreak of hepatitis in a broiler flock in Grenada

Five week-old broiler chickens from an outbreak of bacterial hepatitis on a poultry farm in Grenada were examined. The predominant gross lesions included multiple pinpoint light yellow foci in the liver, moderate splenomegaly, and ulcerative pododermatitis. The hepatic lesions were characterised by multifocal necrotising hepatitis with intralesional bacterial colonies. Culture of the liver lesions yielded a heavy growth of Aerococcus viridans and a moderate growth of Escherichia coli. The A. viridans isolates showed typical biochemical properties, susceptibility to vancomycin, and moderate resistance to aminoglycoside antibiotics. It appears that dual infection with A. viridans and E. coli caused hepatitis in these chickens which had earlier history of coccidiosis.

Antimicrobial drug resistance and genetic diversity of commensal Escherichia coli from caeca of chickens in Grenada.

The main goal of this study was to generate baseline data on resistance to 11 antimicrobial drugs of global importance among commensal Escherichia coli from healthy chicken in Grenada. For this purpose, a total of 183 commensal Escherichia coli isolates from 197 chickens (147 broilers and 50 layers) originating from 11 poultry farms in Grenada were studies using a standard disk diffusion method. The isolates were further studied for their haemolytic properties using sheep blood agar, and genotypes using the enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). Sixty-six isolates were positive for alpha haemolysis, and the remaining were non-haemolytic. There was no difference in antimicrobial susceptibility between haemolytic and non-haemolytic isolates. Resistance was highest against tetracycline (58.5%) followed by streptomycin (44.3%) and lowest to chloramphenicol (0.55%). Only three isolates (1.6%) showed resistance to fluoroquinolones. Resistance rates to tetracycline, streptomycin, and gentamicin were significantly lower among isolates from layers, compared with those from broilers. Multiple resistance to three or more classes of drugs was found in 10.4% of total isolates; the most common R-profile was Amp, Str, Tet. Twenty genotypes were identified among 24 randomly selected isolates that originated from 11 unrelated farms and 5 geographical locations. Isolates sharing similar genomic fingerprints by ERIC-PCR had different resistance profiles, whereas isolates with different genotypes shared similar profiles. In conclusion, this study showed the genetic diversity of chicken isolates from Grenada, and their significance and the epidemiological significance of ERIC-PCR genotypes among poultry isolates need further study.

Antimicrobial drug resistance and genetic diversity of commensal Escherichia coli from caeca of chickens in Grenada.

The main goal of this study was to generate baseline data on resistance to 11 antimicrobial drugs of global importance among commensal Escherichia coli from healthy chicken in Grenada. For this purpose, a total of 183 commensal Escherichia coli isolates from 197 chickens (147 broilers and 50 layers) originating from 11 poultry farms in Grenada were studies using a standard disk diffusion method. The isolates were further studied for their haemolytic properties using sheep blood agar, and genotypes using the enterobacterial repetitive intergenic consensus sequence PCR (ERIC-PCR). Sixty-six isolates were positive for alpha haemolysis, and the remaining were non-haemolytic. There was no difference in antimicrobial susceptibility between haemolytic and non-haemolytic isolates. Resistance was highest against tetracycline (58.5%) followed by streptomycin (44.3%) and lowest to chloramphenicol (0.55%). Only three isolates (1.6%) showed resistance to fluoroquinolones. Resistance rates to tetracycline, streptomycin, and gentamicin were significantly lower among isolates from layers, compared with those from broilers. Multiple resistance to three or more classes of drugs was found in 10.4% of total isolates; the most common R-profile was Amp, Str, Tet. Twenty genotypes were identified among 24 randomly selected isolates that originated from 11 unrelated farms and 5 geographical locations. Isolates sharing similar genomic fingerprints by ERIC-PCR had different resistance profiles, whereas isolates with different genotypes shared similar profiles. In conclusion, this study showed the genetic diversity of chicken isolates from Grenada, and their significance and the epidemiological significance of ERIC-PCR genotypes among poultry isolates need further study.

Microbial load and the prevalence of Escherichia coli, Salmonella spp. and Listeria spp. in Ready-to-Eat products in Trinidad.

This study was designed to determine the prevalence and microbial load of Listeria spp., Escherichia coli O157 and Salmonella spp. in ready-to-eat products in supermarkets across Trinidad. The microbial load was assessed using the total aerobic plate count (TAPC) per g/ml of foods and prevalence of Escherichia coli O157 and Salmonella spp. determined using conventional methods. For Listeria monocytogenes, immunomagnetic separation (IMS), TECRA (enzymelinked immunosorbent assay, ELISA) and conventional methods were used. The log10 mean ñ sd TAPC per g or ml was highest for vegetables (11.0ñ11.6), and lowest for seafood (5.2ñ5.7) (p < 0.05). The prevalence of L. monocytogenes was 1.7 per cent. Sixteen (4.5 per cent) of 153 samples yielded E. coli but all samples were negative for Salmonella spp. and E. coli O157. The high microbial load and isolation of L. monocytogenes and E. coli from popular RTE foods could pose a health risk to consumers in the country.

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.

Enterobacteriaceae from chicken ceca in Grenada and susceptibility of Escherichia coli isolates to fluoroquinolones.

Ceca from two hundred and seven chickens in Grenada were examined by culture for the presence of Escherichia coli and Salmonella. The isolates were tested for susceptibility to fluoroquinolone drugs, ciprofloxacin and enrofloxacin, employing the Kirby-Bauer disk diffusion assay. Of a total of 203 isolates od E. coli, 199 isolates including a non lactose fermenting strain were susceptible to both drugs. The four fluoroquinolones-resistant isolates showed multiple resistance, with one strain being resistant to six additional drugs: amplicillin, amoxicillin-clavulanic acid, chloramphenicol, gentamicin, streptomycin, and tetracycline. The lone Salmonella isolate was susceptible to both fluoroquinolone drugs.

Enterobacteriaceae from chicken ceca in Grenada and susceptibility of Escherichia coli isolates to fluoroquinolones.

Ceca from two hundred and seven chickens in Grenada were examined by culture for the presence of Escherichia coli and Salmonella. The isolates were tested for susceptibility to fluoroquinolone drugs, ciprofloxacin and enrofloxacin, employing the Kirby-Bauer disk diffusion assay. Of a total of 203 isolates od E. coli, 199 isolates including a non lactose fermenting strain were susceptible to both drugs. The four fluoroquinolones-resistant isolates showed multiple resistance, with one strain being resistant to six additional drugs: amplicillin, amoxicillin-clavulanic acid, chloramphenicol, gentamicin, streptomycin, and tetracycline. The lone Salmonella isolate was susceptible to both fluoroquinolone drugs.

Occurrence and characterization of verocytotoxigenic Escherichia coli (VTEC) strains from dairy farms in Trinidad.

A cross-sectional study was conducted to determine the prevalence and characteristics of verocytotoxigenic Escherichia coli (VTEC) on 25 dairy farms each located in Waller field and Carlsen field farming areas in Trinidad. On each selected farm, faecal samples were collected from milking cows, calves and humans; rectal swabs were obtained from pet farm dogs; bulk milk was sampled as well as effluent from the milking parlour. Escherichia coli was isolated from all sources on selective media using standard methods. Isolates of E. coli were subjected to slide agglutination test using E. coli O157 antiserum, vero cell cytotoxicity assay to detect verocytotoxin (VT) and heat labile toxin (LT) production, the polymerase chain reaction (PCR) to detect VT genes, and the dry spot test to screen for E. coli O157 and non-O157 strains. In addition, faecal samples from animal and human sources were tested for VT genes using PCR. Of a total of 933 E. coli isolates tested by the slide test, eight (0.9 per cent) were positive for the O157 strain. The vero cell cytotoxicity assay detected VT-producing strains of E. coli in 16.6 per cent, 14.6 per cent, 3.2 per cent and 7.1 per cent of isolates from cows, calves, farm dogs and humans respectively (P < 0.05; chi(2)). For LT production, the highest frequency was detected amongst isolates of E. coli from calves (10.8 per cent) and the lowest (0.0 per cent) amongst isolates from humans and bulk milk (P < 0.05; chi(2)). Of the 61 VT-producing isolates by vero cell cytotoxicity assay tested by PCR, the VT, LT and eae genes were detected in 62.3 per cent, 4.9 per cent and 1.6 per cent respectively (P < 0.05; chi(2)). Amongst the 45 E. coli isolates that were VT positive (vero cell) or VT-gene positive by PCR, 2.2 per cent, 2.2 per cent, 4.4 per cent and 6.7 per cent belonged to non-O157 strains O91, O111, O103 and O157, respectively, as determined by the Dry spot test...

Antimicrobial susceptibility patterns of urinary pathogens in Trinidad, 1996-1999

The prevalence of antimicrobial resistance among urinary pathogens has been increasing worldwide. Laboratory diagnosed urinary tract infections were retrospectively evaluated for the years 1996 through 1999, to document the common pathogens and their changing antimicrobial profiles. From 14,853 hospital specimens, an isolation rate of 6.1% was found; and from 5330 community specimens, the isolation rate was 27.9%. E. coli was the predominant cause of urinary tract infections in both hospital and community practices. The rate of isolation of the other pathogens was relatively stable except for citrobacter species, which increased from 1.3% in 1996 to 20.1% in 1999 (p < 0.001) among community isolates. Significant changes in the susceptibility patterns of uropathogens also were observed. E. coli strains from hospitals were significantly more resistant to cefuroxime than community strains (p < 0.001), while resistance to ampicillin and nalidixic acid was high in both practices. No substantial changes in susceptibility to gentamicin and tetracycline were noticed during the four-year period compared to the 99% resistance to tetracycline in 1995. In relation to nitrofurantoin, no significant changes were noted in both practices where resistant rates remained low, but susceptibility to augmentin showed much improvement among all isolates, including E. coli. Urinary isolates were more commonly recovered from the paediatric age group (1-10 years) and those older than 50 years of age, and males were the predominant gender in both age groups. The study showed that the antibiotics useful in the treatment of UTI in decreasing order of effectiveness in community practice were gentamicin, norfloxacin, nitrofurantoin and cefuroxime. For nosocomial UTI, the drugs most effective include norfloxacin, nitrofurantoin, gentamicin, co-trimoxazole and amoxicillin-clavulanic acid.

Evaluation of augmentin and cotrimoxazole against 276 pathogens in community acquired urinary tract infections [abstract]

OBJECTIVE: Augmentin and cotrimoxazole are the front-line drugs in the therapy of community acquired urinary tract infections. This report examines the in vitro efficacy of these two drugs against 276 urinary pathogens encountered from patients attending outpatient clinics at the University Hospital of the West Indies. METHODS: The urines collected from outpatients in 3 months (March to May, 2001) were cultured semi-quantitatively. The isolates (o 10 cfu/ml) were identified by routine methodology and antimicrobial susceptibilities were determined by the standard disc-diffusion technique. RESULTS: Of the 276 isolates, 190 (68.8 percent) were gram negative and 86 (31.2 percent ) were gram positive pathogens. The common isolates in order of frequency were: Escherichia coli 89 (32.2 percent), Enterococci/Group D Streptocci 33 (12.0 percent, Proyteus mirabilis 28 (10.1 percent), Klebsiella sp 25 (9.1 percent) and coagulase negative Staphulococci 20 (7.2 percent). These five organisms together accounted for over two-thirds (70.7 percent of all isolates. Augmentin was effective against 71.0 percent of all, 68.9 percent of gram negative and 75.6 percent of gram positive pathogens and cotimoxazole was effective against 63.0 percent of all, 58.4 percent gram negative and 73.3 percent of gram-positive isolates. CONCLUSION: Despite decades of their usage, augmentin and cotrimoxazole continue to be effective in community acquired urinary tract infections. (AU)

Prevalence of resistance to antimicrobials of Escherichia coli isolates from clinical sources at a private hospital in Trinidad

Antimicrobial susceptibility patterns of strains of Escherichia coli isolated between 1994 and 1998 were studied. Of the 1,283 strains examined, 75% were recovered from urine, 8.7% from wounds, 3.2% from blood, 2.6% from pus, and 10.5% from other sources. Isolates from inpatients and outpatients accounted for 46.1% and 53.9%, respectively. Gentamicin and nalidixic acid showed the greatest efficacy against isolates from both inpatients and outpatients, revealing a >90% sensitivity. Drugs with the lowest efficacies were ampicillin and amoxicillin-clavulanic acid, which showed a >45% resistance. Tetracycline showed a significant decline in resistance from 1994 to 1998 among strains from both inpatients and outpatients (P < 0.001). This decline may be related to a policy of restrictive antibiotic reporting by the Microbiology Laboratory and seminars for general practitioners, subsequent to an island-wide survey an antibiotic resistance. A similar pattern of declining resistance was also observed for cefuroxime. E. coli sensitivity to co-trimoxazole was relatively stable during the study period. Although the overall prevalence of resistance among E. coli strains is relatively low, on-going surveillance of bacterial resistance must continue. The microbial antibiogram can provide general practitioners and clinicians with data essential for optimum empiric choices. Further, the introduction of a policy of restrictive reporting may act "synergistically" with the education of doctors on resistance patterns, to effect island-wide reduction of antimicrobial resistance.

Microbial quality of water in rural communities of Trinidad

A cross-sectional study was conducted in four rural communities of northeastern Trinidad to determine the microbial quality of water supply to households and that quality's relationship to source and storage device. Of the 167 household water samples tested, total coliforms were detected in 132 of the samples (79.0 percent), fecal coliforms in 102 (61.1 percent), and E. coli in 111 (66.5 percent). There were significant differences among the towns in the proportions of the samples contaminated with coliforms (P <0.001) and E. coli (P <0.001). Of 253 strains of E. coli studied, 4 (1.6 percent) were mucoid, 9 (3.6 percent) were hemolytic, and 37 (14.6 percent) were nonsorbitol fermenters. Of 69 isolates of E. coli tested, 10 (14.5 percent) were verocytotoxigenic. Twenty-eight (14.0 percent) of 200 E. coli isolates tested belonged to enteropathogenic serogroups. Standpipe, the most common water source, was utilized by 57 (34.1 percent) of the 167 households. Treated water (pipeborne in homes, standpipes, or truckborne) was supplied to 119 households (71.3 percent) while 48 households (28.7 percent) used water from untreated sources (rain, river/stream, or well) as their primary water supply. The type of household storage device was associated with coliform contamination. Water stored in drums, barrels, or buckets was more likely to harbor fecal coliforms (74.2 percent of supplies) than was water stored in tanks (53.3 percent of samples), even after controlling for water source (P=0.04). Compared with water from other sources, water piped into homes was significantly less likely to be contaminated with total coliforms (56.9 percent versus 88.8 percent, P <0.001) and fecal coliforms (41.2 percent versus 69.8 percent, P <0.01), even when the type of storage device was taken into account. However, fecal contamination was not associated with whether the water came from a treated or untreated source. We concluded that the drinking water in rural communities in Trinidad was grossly unfit for human consumption, due both to contamination of various water sources and during household water storage (AU)

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)

Microbial quality of oysters sold in Western Trinidad and potential health risk to consumers

The prevalence and characteristics of Escherichia coli and Salmonella spp. as well as counts of E. coli in raw oysters, condiments/spices, and raw oyster cocktails sampled from 72 vendors across Western Trinidad were determined. The microbial quality of the water used in the preparation of raw oysters was also investigated. Of 200 samples each of raw oysters, condiments/spices and oyster cocktails tested, 154 (77.0 percent), 89 (44.5 percent) and 154 (77.0 percent) respectively yielded E. coli. The differences were statistically significant (P= <0.001; chi square = 62.91). The mean E. coli count per g in the ready-to-eat oyster cocktail ranged from 1.5 x 10(3) +/- 2.7 x 10(3) in Couva to 8.7 x 10(6) +/- 4.9 x 10(7) in San Fernando. One hundred and forty six (73.0 percent) oyster cocktails contaminated with E. coli had counts that exceeded the recommended standard of 16 per g. Of a total of 590 E. coli isolates from various sources tested, 24 (4.1 percent0, 20 (3.4 percent) and 69 (11.7 percent) were mucoid, haemolytic and non-sorbitol fermenters respectively. Twelve (2.0 percent) isolates of E. coli were O157 strains, while 92 (46.0 percent) of 200 E.coli isolates tested belonged to enteropathogenic serogroups. Ninety (45.0 percent) and 73 (36.5 percent) of 200 water samples contained total coliforms and faecal coliforms respectively, with counts that exceeded 2.2 coliforms per 100 ml. Salmonella spp. were isolated from 7 (3.5 percent), 1 (0.5 percent) and 2 (1.0 percent) of 200 samples each, of raw oysters, condiments/spices and oyster cocktails respectively. Oysters pose a health risk to consumers in Trinidad, particularly from colibacillosis and salmonellosis, and the need for increased public awareness of this hazard cannot be over-emphasized. (AU)

Enteroaggregative Escherichia coli as a cause of traveler's diarrhea: clinical response to ciprofloxacin

The purpose of this study was to determine the role of enteroaggregative Escherichia coli (EAEC) in the development of traveler's diarrhea and the clinical response of patients with EAEC diarrhea following treatment with ciprofloxacin. Sixty-four travelers with diarrhea and no other recognized enteropathogen were enrolled in treatment studies in Jamaica and Mexico from July 1997 to July 1998. EAEC was isolated from 29 travelers (45.3 percent). There was a significant reduction in the duration of posttreatment diarrhea in the 16 patients treated with ciprofloxacin, as compared with that in the 13 patients who received placebo (mean of 35.3 versus 55.5 hours; P= .049). There was a nonsignificant reduction in the mean number of unformed stools passed during the 72 hours after enrollment in the ciprofloxacin-treated group (7.5) (P= .128). This study provides additional evidence that EAEC should be considered as a cause of antibiotic-responsive traveler's diarrhea. (AU)