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Stool samples of 616 asymptomatic and 296 diarrhoeic school children were compared for the recovery rate of Aeromonas spp. on ampicillin (10 micrograms/ml) sheep blood agar. Culture filtrates of isolates were tested for haemolysin production with 1% freshly washed rabbit erythrocytes. Stools of 9 (3.0%) diarrhoeic children yielded five strains of A. hydrophila and four of A. veronii (two each of biotypes sobria and veronii), compared to 12 (1.9%) (p > 0.01) asymptomatic children who harbored seven A. hydrophila and five A. caviae strains. Isolates from-diarrhoeic stools were exclusively from children < or = 5 years, while all infected asymptomatic children were > or = 6 years. Culture filtrates of all nine diarrhoeic strains were uniformly enterotoxigenic (intestinal weight ratio > 0.083) and produced haemolysin titres > 128. These phenotypes where variable in carriage strains of A. hydrophila but were not detected in A. caviae. The recovery of A. hydrophila, and A. veronii biotypes from diarrhoeic stools of children < or = 5 years may suggest their involvement in diarrhoea causation in the absence of other diarrhoeagenic agents.

In 1991 a cholera epidemic occurred in Nigeria. The features of this cholera outbreak in a single hospital in Cross River, Nigeria, were examined. Microbiologic techniques included the use of thiosulphate citrate bile-salts sucrose (TCBS) medium for culture of all stool specimens. Vibrio isolates from diarrheic patients included V. cholerae-O1 (75), V. cholerae non-O1 (10) and V. parahaemolyticus (21). The illnesses were diverse, ranging from mild to severe, and in most instances requiring hospitalization, rehydration as well as antibiotic treatment. Eighty patients were hospitalized and six died mainly from hypovolemic shock and acute renal failure arising from excessive fluid loss. The low vibrio-associated mortality observed in this outbreak may have been influenced by the proximity and easy transit access to the health care facilities offered by the teaching hospital. This contrasts with the high mortality figures reported by Health Centers in the rural areas during the same period. Some features of vibrio diarrheas were comparable with those of other enteric pathogens. Poorly developed water and sewage disposal systems, contact with sea water, consumption of fishery products and leftover foods were the main risk factors identified.

The clinical and epidemiological features of acute vibrio diarrhoeal disease were studied in 881 patients seen at the University of Calabar Teaching Hospital (UCTH), Calabar, Nigeria, between January and December 1989. Stools and rectal swabs of patients and randomly-selected control subjects were microscopically and culturally examined for the presence of enteric pathogens. Households of vibrio diarrhoea cases and matched controls were visited for ecologic studies. Of a total of 108 (12.3%) culturally-confirmed bacterial diarrhoeas, 47 (43.5%) were due to Escherichia coli, 33 (30.6%) to Vibrio cholerae-01 (classical and El Tor biotypes) and V. parahaemolyticus, while shigellae and salmonellae accounted for 29 (26.9%) and 9 (8.3%) cases, respectively. Most cholera case households clustered within the ancient neighbourhood of the inner city, characterized by poorly developed water and sewage disposal systems. A preponderance of vibrio diarrhoea patients were children < or = 10 years. Adult cases involved mostly females. The only case of diarrhoea-related death involved an eight-month old child with kwashiorkor and V. parahaemolyticus infection. Incidence of vibrio diarrhoeas was seasonal, with most cases occurring during the dry season followed by subsidence at the onset of rainy season. Bimodal peaks of vibrio diarrhoeal episodes observed over the period appeared to coincide with periods of acute water scarcity, high temperature, increased fishing activities and trade traffic on the Calabar River estuary. Of the environments sampled, only clam shells from a case household and river sediments yielded vibrio pathogens on culture. Ecological factors that are capable of stabilizing a focus of vibrio diarrhoea endemicity in this area are highlighted.

The prevalence, clinical profiles and virulence factors of Plesiomonas shigelloides were determined in patients attending the University of Calabar Teaching Hospital, Microbiology Laboratory. P. shigelloides was isolated from 12 (1.4%) of 880 patients with diarrhoea and from none of the controls (P less than 0.05). Isolates were mostly from febrile children less than or equal to 10 years with most of the infections occurring during the rainy months. Although our findings suggest the significance of Plesiomonas in acute diarrhoea in this environment, our isolates did not seem to show any of the proxy indicators of virulence usually associated with other enteric pathogens.

The microbiological and morbidity profiles of acute diarrhoeal episodes were studied in 881 patients seen at the Out-Patients Department of the University of Calabar Teaching Hospital (UCTH), Calabar, between January and December, 1988. Of a total of 108 (12.3%) culturally confirmed bacterial diarrhoeas, 47 (43.5%) were due to Escherichia coli, 33 (30.6%) to vibrios (Vibrio cholerae-01; classical and E1 Tor biotypes and V. parahaemolyticus), while shigella spp. and salmonella. spp. accounted for 29 (17.7%) and 9 (8.3%) episodes respectively. Twenty (64.5%) of the patients with vibrio diarrhoeas were children less than or equal to 10 years. The only case of diarrhoea-associated death observed, involved an 8-month old infant with kwashiorkor and V. parahaemolyticus infection. Bimodal peaks of cholera episodes occurred during the dry season and appeared to coincide with acute water shortage periods in the municipality. The significance of some prevailing ecological factors in stabilizing a focus of cholera and halophilic vibrio diarrhoea endemicity in this region is discussed.

The prevalence of Aeromonas spp. and other enteric pathogens in stool specimens from diarrheic and non-diarrheic patients was studied over a 12 month period (January to December, 1986). Except for the absence of fever, all the clinical features in Aeromonas diarrhea were comparable to those associated with other diarrheagenic agents. These features included abdominal pain (30%), vomiting (24.5%), fever (31.5%), dehydration (9.5%) and hematochezia (19.5%). Aeromonas spp. were more frequently isolated from patients with gastroenteritis (2.5%) than from control patients (1.0%) (P less than 0.05). Isolates were recovered more often during the dry months (66.7%), than during the wet months (33.3%). Among the enteric pathogens isolated, Aeromonas spp. (2.5%) ranked next to Esch. coli (14.5%) and Shigella spp. (6.3%) in prevalence. Other bacterial isolates included Plesiomonas shigelloides (1.5%) Vibrio spp. (1.0%), Yersinia enterocolitica (1.0%) and Salmonella spp. (1.8%).

During a 12-month study period (January-December 1986), 12 Aeromonas strains (eight A. hydrophila and four A. sobria) were isolated from the 400 diarrhoeic and 200 non-diarrhoeic stools examined. Isolates were characterized for frequency of phenotypic properties associated with virulence using the suckling mouse test for enterotoxin assay; haemolysis of rabbit erythrocytes for haemolysin production, and haemagglutination of human group A cells (HA) for presence of colonization factor antigens (CFA). All seven A. hydrophila and three A. sobria strains isolated from diarrhoeic stools produced enterotoxin. All, except one A. sobria strain from a diarrhoeic stool, produced haemolysin in titres greater than 4. Fifty per cent of strains from diarrhoeic stools and 100% of strains from non-diarrhoeic stools were HA positive. All HA reactions were sensitive to mannose and galactose. The frequency of enterotoxin-producing aeromonads was significantly higher (P less than 0.05) in diarrhoeic patients than in non-diarrhoeic controls. There was no significant difference (P greater than 0.05) in the frequency of haemolysin and HA production between diarrhoeic and non-diarrhoeic strains.