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A fifteen-month fortnightly survey of microbial health risk indicators and pathogens has been carried out at 25 freshwater recreational and water supply sites distributed throughout New Zealand, for: E. coli, Clostridium perfringens spores, F-RNA bacteriophage, somatic coliphage, human enteroviruses, human adenoviruses, Cryptosporidium oocysts, Giardia cysts, Salmonella and Campylobacter. Sites were selected to represent five geographical areas covering New Zealand and five categories of predominant environmental impact: birds, dairy farming, forestry/undeveloped, municipal, and sheep/pastoral farming. Six of the sites were also source waters for treated drinking-water supplies. Of the indicators, E. coli was detected in 99 % of all samples, with somatic coliphage being detected most of the time (89 %). Of the pathogens tested, Campylobacter and human adenoviruses were inferred to be the most likely to cause human waterborne illness to recreational freshwater users. Using data from all sites, an estimated 5 % of notified campylobacteriosis cases in New Zealand could be attributable to water contact recreation. The critical value for E. coli as an indicator of increased Campylobacter infection is in the range of 200 -500 E. coli per 100 ml. This result has been used to derive new national water quality guidelines for recreational fresh water in New Zealand.

Prospective epidemiolog ical studies on the possible health effec ts from sea bathing w ere carried out at seven popular New Zealand bathing beaches ov er the 1995 summer. The association of gastrointes tinal/ respiratory symptoms or other infections w ith human or animal faecal contamination of the beach w ater w as examined. Beach users w ere interview ed at the beach and then follow ed up w ithin 5 days to ascertain any illness symptoms. On each of the 107 interv iew day s multiple samples of the beach w ater w ere examined for three faecal indicators (faecal coliforms , E. coli, enterococci). Of the usable responses, 2307 users did not enter the w ater; 1577 did. Log-linear modelling show ed that enterococci w as most strongly and consistently associated w ith illness risk for the exposed groups, particularly for respiratory illness among paddlers and long-duration sw immers. Crude risk differenc es for these tw o groups w ere 7 and 33 per 1000 indiv iduals, rising to 62 and 87 per 1000 indiv iduals for the hig hest enterococci quartile. No substantial differences in illness risks w ere found betw een the human and animal w aste impacted beaches, thoug h both w ere markedly different from the control beaches. The results are being used to dev elop recommendations for sampling design and use of single-sample maxima in new bathing -w ater guidelines.

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An international comparative study, undertaken by six laboratories to assess the performance of four selective media commonly used for the enumeration of Staphylococcus aureus in foods, revealed that Baird-Parker agar performed most satisfactorily. There was no significant difference among milk salt, tellurite polymyxin egg yolk, and kalium rhodanid - actidione - natriumazid - eigelb - pyruvat (KRANEP) agars. The type of food examined appeared to influence the performance of the media, but no specific patterns could be determined. Cultures yielding 3+ and 4+ coagulase reactions are most likely to possess thermostable nuclease activity, and are therefore most likely to be S. aureus.