| Journal of Applied Microbiology
Volume 101 Page 828 - October 2006 doi:10.1111/j.1365-2672.2006.02983.x |
| Volume 101 Issue 4 |
| ORIGINAL ARTICLE |
| Efficacy of solar disinfection of Escherichia coli, Shigella flexneri, Salmonella Typhimurium and Vibrio cholerae |
| M. Berney, H.-U. Weilenmann, A. Simonetti and T. Egli |
| Abstract
Aims: To determine the efficacy of solar disinfection (SODIS) for enteric pathogens and to test applicability of the reciprocity law. Methods and Results: Resistance to sunlight at 37°C based on F99 values was in the following order: Salmonella Typhimurium > Escherichia coli > Shigella flexneri > Vibrio cholerae. While F90 values of Salm. Typhimurium and E. coli were similar, F99 values differed by 60% due to different inactivation curve shapes. Efficacy seemed not to be dependent on fluence rate for E. coli stationary cells. Sensitivity to mild heat was observed above a temperature of 45°C for E. coli, Salm. Typhimurium and Sh. flexneri, while V. cholerae was already susceptible above 40°C. Conclusions: Salmonella Typhimurium was the most resistant and V. cholerae the least resistant enteric strain. The reciprocity law is applicable for stationary E. coli cells irradiated with sunlight or artificial sunlight. Significance and Impact of the Study: Escherichia coli might not be the appropriate indicator bacterium to test the efficacy of SODIS on enteric bacteria and the physiological response to SODIS might be different among enteric bacteria. The applicability of the reciprocity law indicates that fluence rate plays a secondary role in SODIS efficacy. Stating inactivation efficacy with T90 or F90 values without showing original data is inadequate for SODIS studies. |
| Volume 101 Issue 4 |
| ORIGINAL ARTICLE |
| Survival of Escherichia coli O157:H7 in wastewater from dairy lagoons |
| S.V. Ravva1, C.Z. Sarreal1, B. Duffy2 and L.H. Stanker1 |
| Abstract
Aim: To determine the survival of Escherichia coli O157:H7 in dairy wastewater from on-site holding lagoons equipped with or without circulating aerators. Methods and Results: Survival was monitored in dairy lagoon microcosms equipped with or without scale-size circulators. Both laboratory strains of E. coli O157:H7 and an isolate of E. coli H7 from wastewater had poor survival rates and none proliferated in water from waste lagoons with or without circulators. Furthermore, the decline of E. coli O157:H7 was not enhanced in those microcosms equipped with circulators. Strain variation in survival was observed in both circulated and settling waters. The decline rate of E. coli O157:H7 Odwalla strain increased proportionately with the inoculum load. Escherichia coli failed to establish itself in wastewater even after four sequential inoculations simulating continuous faecal input into the lagoon. The native aerobic bacteria survived longer with a decimal reduction time of 21·3 days vs either introduced or native E. coli, which declined rapidly with decimal reduction time of 0·5–9·4 days. Conclusions: Escherichia coli O157:H7 failed to establish and proliferate in dairy wastewater microcosms equipped with or without circulating aerators. Significance and Impact of the study: This study furthers our knowledge of pathogen survival in wastewater, and suggests that proper management of wastewater before its use in irrigation is essential to reduce pathogen transfer to crops. |
| Volume 101 Issue 4 |
| ORIGINAL ARTICLE |
| A nucleic acid sequence-based amplification assay for real-time detection of norovirus genogroup II |
| S.S. Patterson1, M.W. Smith2, E.T. Casper1, D. Huffman1, L. Stark2, D. Fries3 and J.H. Paul1 |
| Abstract
Aims: To use molecular beacon based nucleic acid sequence-based amplification (NASBA) to develop a rapid, sensitive, specific detection method for norovirus (NV) genogroupII (GII). Methods and Results: A method to detect NV GII from environmental samples using real-time NASBA was developed. This method was routinely sensitive to 100 copies of target RNA and intermittent amplification occurred with as few as 10 copies. Quantitative estimates of viral load were possible over at least four orders of magnitude. Conclusions: The NASBA method described here is a reliable and sensitive assay for the detection of NV. This method has the potential to be linked to a handheld NASBA device that would make this real-time assay a portable and inexpensive alternative to bench-top, lab-based assays. Significance and Impact of the Study: The development of the real-time NASBA assay described here has resulted in a simple, rapid (<1 h), convenient testing format for NV. To our knowledge, this is the first example of a molecular beacon based NASBA assay for NV. |