Dose–response algorithms for water-borne Pseudomonas aeruginosa folliculitis

SUMMARYWe developed two dose–response algorithms forP. aeruginosapool folliculitis using bacterial and lesion density estimates, associated with undetectable, significant, and almost certain folliculitis. Literature data were fitted to Furumoto & Mickey's equations, developed for plant epidermis-invading pathogens:Nl = Aln(1 + BC) (log-linear model);Pinf = 1−e(−rcC)(exponential model), whereAandBare 2.51644 × 107lesions/m2and 2.28011 × 10−11 c.f.u./mlP. aeruginosa, respectively;C = pathogen density (c.f.u./ml),Nl = folliculitis lesions/m2,Pinf = probability of infection, andrC = 4·3 × 10−7 c.f.u./mlP. aeruginosa. Outbreak data indicates these algorithms apply to exposure durations of 41 ± 25 min. Typical water quality benchmarks (≈10−2 c.f.u./ml) appear conservative but still useful as the literature indicated repeated detection likely implies unstable control barriers and bacterial bloom potential. In future, culture-based outbreak testing should be supplemented with quantitative polymerase chain reaction and organic carbon assays, and quantification of folliculitis aetiology to better understandP. aeruginosarisks.