Evaluation of culture media for recovery of Staphylococcus aureus from swimming pools

Bacteriological quality of some swimming pools in Alexandria with special reference to Staphylococcus aureus

Swimming pools have been identified as posing some public health risks to users due to either bacterial or chemical contamination. As a result, maintaining good swimming pool water quality is an important issue in preventing health risks for bathers. This study aimed to evaluate the bacteriological quality of some swimming pools in Alexandria and to investigate the prevalence of Staphylococcus aureus (S. aureus) in water samples. A total of 120 water samples from 10 swimming pools were collected. Bacteriological analysis included heterotrophic plate count (HPC) using pour plate method; enumeration of total coliforms (TC), Escherichia coli (E. coli) and S. aureus by membrane filtration technique. Antimicrobial susceptibility testing was performed on isolated S. aureus. Residual chlorine and pH were measured at swimming pools side. HPC was the least complying microbial parameter, followed by TC. S. aureus was recovered from 18 samples; 9 isolates were methicillin resistant S.aureus (MRSA), compared to E. coli that was detected in 7 samples. HPC and TC showed statistically significant correlations with all investigated parameters. In conclusion, the examined pools showed poor quality regarding all examined parameters collectively according to the Egyptian guidelines, which necessitates implementation of proper measures to ensure safer environment in swimming pools.

Predicting likelihood of gastroenteritis from sea bathing: results from randomised exposure

The health effects of bathing in coastal waters is an area of scientific controversy. We conducted the first ever randomised "trial" of an environmental exposure to measure the health effects of this activity. The trial was spread over four summers in four UK resorts and 1216 adults took part. Detailed interviews were used to collect data on potential confounding factors and intensive water quality monitoring was used to provide more precise indices of exposure. 548 people were randomised to bathing, and the exposure included total immersion of the head. Crude rates of gastroenteritis were significantly higher in the exposed group (14.8 per 100) than the unexposed group (9.7 per 100; p = 0.01). Linear trend and multiple logistic regression techniques were used to establish relations between gastroenteritis and microbiological water quality. Of a range of microbiological indicators assayed only faecal streptococci concentration, measured at chest depth, showed a significant dose-response relation with gastroenteritis. Adverse health effects were identified when faecal streptococci concentrations exceeded 32 per 100 mL. This relation was independent of non-water-related predictors of gastroenteritis. We do not suggest that faecal streptococci caused the excess of gastrointestinal symptoms in sea bathers but these microorganisms do seem to be a better indicator of water quality than the traditional coliform counts. Bathing water standards should be revised with these findings in mind.

Health effects of white-water canoeing

There is little quantitative information on the relation between water quality and disease attack rates after recreational activities in fresh water. We conducted a prospective cohort study to measure the health effects of white-water and slalom canoeing in two channels with different degrees of microbial contamination. Site A, fed by a lowland river, showed high enterovirus concentrations (arithmetic mean 198 pfu per 10 litre and moderate faecal coliform concentrations (geometric mean 285/dl); at site B, from an upland impoundment, all samples were free of enteroviruses and the geometric mean faecal coliform concentration was 22/dl. Between 5 and 7 days after exposure canoeists using site A had significantly higher incidences of gastrointestinal and upper respiratory symptoms than canoeists using site B or non-exposed controls (spectators). Like seawater bathers, fresh-water canoeists can be made ill by sewage contamination. The hazard of fresh water may be best measured by counting of viruses rather than bacteria.

Health effects of beach water pollution in Hong Kong

Prospective epidemiological studies of beach water pollution were conducted in Hong Kong in the summers of 1986 and 1987. For the main study in 1987, a total of 18741 usable responses were obtained from beachgoers on nine beaches at weekends. The study indicated the overall perceived symptom rates for gastrointestinal, ear, eye, skin, respiratory, fever and total illness were significantly higher for swimmers than non-swimmers; and the swimming-associated symptom rates for gastrointestinal, skin, respiratory and total illness were higher at 'barely acceptable' beaches than at 'relatively unpolluted' ones. Escherichia coli was found to be the best indicator of the health effects associated with swimming in the beaches of Hong Kong. It showed the highest correlation with combined swimming-associated gastroenteritis and skin symptom rates when compared with other microbial indicators. A linear relationship between E. coli and the combined symptom rates was established. Staphylococci were correlated with ear, respiratory and total illness, but could not be used for predicting swimming-associated health risks. They should be used to complement E. coli. The setting of health-related bathing-water quality standards based on such a study is discussed.

Comparative studies of selective media for recovery of Staphylococcus aureus from natural waters

Several selective media currently used for the enumeration of Staphylococcus aureus from different sources were evaluated in order to establish their quantitative recovery, specificity and degree of selectivity, using different types of water samples. The highest selectivity and reliability in the enumeration of Staph. aureus from the samples was obtained on Borrego-Florido-Romero-0 (BFR-0) and KRANEP agars. The method that produced the highest recovery of Staph. aureus was BFR-0 agar with membrane filter and incubation at 36 degrees C for 48-72 h.