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becky cosgrove our lab supervisor found that blue halo
colonies <.5 mm could be non ent (streptococcus) or ent, and that the strep
colonies were less distinct looking than the ent that were <.5 mm - she also
found that yellow colonies (that grew at an ocean site during dry weather) were
staph (non aureus), probably from marine biofilms in adjacent raritan bay
estuary -
this info may be of interest to some of your lab people
struggling with epa method 1600's inconsistencies
Size Doesn’t Matter
Analysts can identify Enterococcus more accurately via morphological characteristics Elizabeth B. Cosgrove In the 2006 version of Method 1600 for Enterococcus, the U.S. Environmental Protection Agency EPA describes the target bacterial colonies as those that are at least 0.5 mm in diameter and have a blue halo. The 2002 version simply describes the target colonies as any colony with a blue halo. The size distinction was supposed to improve method accuracy, but research shows that it may only increase the rate of false negatives, that is, undetected Enterococcus. Researchers at the Monmouth County (N.J.) Department of Health found that the false negative rate for the 2006 version of Method 1600 was 63%. The analysts found that 24-hour mEI plates of marine water samples often held multiple sizes of blue-haloed colonies. They suspected that the 0.5-mm-diameter criterion excluded too many Enterococcus colonies, leading to reports of false negatives that could endanger public health. Their research confirmed this.
Sincerely
William Simmons Environmental Health Coordinator Monmouth County Health Dept 3435 Rt. 9 Freehold N.J. 07728 Phone (732)431-7456 Fax (732)409-7579 wsimmons@co.monmouth.nj.us CONFIDENTIALITY NOTICE This e-mail, including any attachments, may be intended solely for the personal and confidential use of the sender and recipient(s) named above. The message may include advisory, consultative and/or deliberative material of the County of Monmouth, N.J., and, as such, would be privileged and confidential and not a public document. Access to this message by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution or an action taken, or omitted to be taken in reliance on it is prohibited and may be unlawful. If you have received this e-mail in error, you must not review, transmit, convert to hard copy, copy, use or disseminate this e-mail or any attachments to it and you must delete this message. Please notify the sender by return email. |