ORIGINAL ARTICLE Consistency in the host specificity and host sensitivity of the Bacteroides HF183 marker for sewage pollution tracking W. Ahmed 1,2 , N. Masters 2 and S. Toze 1,3 1 CSIRO Land and Water, Ecosciences Precinct, Brisbane, Qld, Australia 2 Faculty of Science, Health and Education, University of the Sunshine Coast, Maroochydore DC, Qld, Australia 3 School of Population Health, University of Queensland, Brisbane, Qld, Australia Introduction Library-independent microbial source tracking (MST) methods have been used to detect and quantify sewage and animal wastewater-associated markers in environ- mental waters (Bernhard et al. 2003; McQuaig et al. 2009). These markers include anaerobic bacterial gene markers (Bernhard and Field 2000), bacterial toxin gene markers (Chern et al. 2004) and viral markers (McQuaig et al. 2009). Ideally, a MST marker should have certain characteristics such as: (i) it should be specific to only target host group (known as host specificity (H-SPF)), (ii) it should be present in all members within a target host group (known as host sensitivity (H-SNV)), (iii) it should exhibit temporal and geographical stability within a target host group and (iv) the decay rate should be Keywords faecal pollution, HF183 marker, host specificity, microbial source tracking, polymerase chain reaction. Correspondence Warish Ahmed, CSIRO Land and Water, Ecosciences Precinct, 41 Boggo Road, Brisbane 4102, Qld, Australia. E-mail: warish.ahmed@csiro.au 2012 ⁄ 0801: received 2 May 2012, revised 5 July 2012 and accepted 12 July 2012 doi:10.1111/j.1472-765X.2012.03291.x Abstract Aims: The host specificity (H-SPF) and host sensitivity (H-SNV) values of the sewage-associated HF183 Bacteroides marker in the current study were com- pared with the previously published studies in South East Queensland (SEQ), Australia, by testing a large number of wastewater and faecal DNA samples (n = 293) from 11 target and nontarget host groups. This was carried out to obtain information on the consistency in the H-SPF and H-SNV values of the HF183 marker for sewage pollution tracking in SEQ. Methods and Results: Polymerase chain reaction (PCR) analysis was used to determine the presence ⁄ absence of the HF183 marker in wastewater and faecal DNA samples. Among the human composite wastewater (n = 59) from sewage treatment plants and individual human (n = 20) faecal DNA samples tested, 75 (95%) were PCR positive for the HF183 marker. The overall H-SNV of this marker in target host group was 0Æ95 (maximum of 1Æ00). Among the 214 non- target animal faecal DNA samples tested, 201 (94%) samples were negative for the HF183 marker. Six chicken, five dog and two bird faecal DNA samples, however, were positive for the marker. The overall H-SPF of the HF183 marker to differentiate between target and nontarget faecal DNA samples was 0Æ94 (maximum of 1Æ00). Conclusions: The H-SNV (0Æ95) and H-SPF (0Æ94) values obtained in this study was slightly lower than previous studies (H-SNV value of 1Æ00 in 2007 and 1Æ00 in 2009; H-SPF value of 1Æ00 in 2007 and 0Æ99 in 2009). Nonetheless, the overall high H-SNV (0Æ98) and H-SPF (0Æ97) values of the HF183 marker over the past 4 years (i.e. 2007–2011) suggest that the HF183 marker can be reliably used for the detection of sewage pollution in environmental waters in SEQ. Significance and Impact of the Study: In the current study, the HF183 marker was detected in small number nontarget animal faecal samples. Care should be taken to interpret results obtained from catchments or waterways that might be potentially contaminated with dog faecal matter or poultry litter. Letters in Applied Microbiology ISSN 0266-8254 ª 2012 The Authors Letters in Applied Microbiology 55, 283–289 ª 2012 The Society for Applied Microbiology 283