• Assessing Risk: Nonpathogenic Legionella Species

    March 02, 2015

    It's quite common to find Legionella species other than Legionella pneumophila in cooling towers and water distribution systems. To date, fifty-eight Legionella species have been described in published articles. Of these approximately 25 are linked to disease.

    Legionella pneumophila serogroup 1 is the most virulent strain causing the majority of infections. The remaining non-pneumophila species (found in water and soil) are considered nonpathogenic until shown to cause disease. Of the CDC reported cases less than 5% are attributed to these species. Since risk for infection is rare, adjusting your response to an adequate threat level is appropriate.

    For example, there are Legionella species whose colonies exhibit blue-white fluorescence under long-wave UV light and some exhibit red fluorescence. These "blue-white" Legionella species include: L. anisa, L. dumoffii, L. gormanii, L. cherri, L. parisiensis and L. bozemanii. The red fluoresceing species include: L. erythra and L. rubrilucens. Such non-pneumophila species are commonly found in the environment, but rarely cause infection and when they do it is almost exclusively in very immunocompromised individuals.

    In SPL's study, Role of Environmental Surveillance in Determining the Risk of Hospital-Acquired Legionellosis: A National Surveillance Study With Clinical Correlations (ICHE July 2007, Vol 28 No. 7. P 818 - 824) investigators found no infection from species like L. anisa even though it was present in the water systems.

    Take the analogy of bacteria on skin. We know our skin is covered with many bacteria including Staphylococcus aureus, but we only get infections under extreme conditions. Most staph on our skin is inherently not pathogenic but if a patient is immuno-compromised or has a procedure that helps staph gain entry into the body, infection can occur.  This is sometimes referred to as an "opportunistic infection." Like staph other Legionella species are common in the environment but won't cause illness under normal circumstances.

    To say that all Legionella species have the "potential" to cause illness is mere speculation. More than 30 years of research shows few or no reported illnesses from more than half of the known Legionella species. So it's safe to assume the risk of disease is so low as to not to be actionable.

    When assessing risk rely on science rather than speculating about unknowns. When other or new Legionella species are found to contribute significantly to the disease threat, then risk assessments could be adjusted. For now it's appropriate to adjust your response to an adequate threat level as seen is the recent VA Directive that non-pneumophila species only require disinfection in limited circumstances.

  • Legionella Controlled with Monochloramine in Hospital Hot Water System, Says First US Study Published in ICHE

    October 27, 2014

    Legionella is effectively controlled with a new onsite monochloramine generation system in a hospital hot water system, says an SPL study in November’s Infection Control and Hospital Epidemiology available online.

    Evaluation of A New Monochloramine Generation System for Controlling Legionella in Building Hot Water Systems is the first field trial and published study in the US to evaluate the efficacy of a monochloramine generation system to control Legionella in a hospital hot water distribution system. Prior to this technology, monochloramine had been only used at the municipal level in cold water.  

    According to Janet E. Stout, PhD, director of Special Pathogens Laboratory, who led the team of researchers that conducted the 29-month study, “This prospective collaboration provides important objective scientific evidence that demonstrates that onsite generation of monochloramine was effective and that treating only the hot water prevented further cases of Legionnaires’ disease. ”

    Researchers installed the system (Sanikill, a product of Sanipur [Italy]) at a Pittsburgh 459-bed hospital. Early results, publically reported at the Association of Water Technologies annual conference in 2012, reported a rapid and significant reduction of Legionella within the first week of application. Throughout the study, Legionella was controlled. There was no significant increase in microbial population and none of the negative effects associated with monochloramine use in municipal cold water systems.

    “Monochloramine is a promising new technology and viable alternative to historic disinfection methods, especially chlorine, ” says Dr. Stout.

  • Case Study on the Effiicacy of Chlorine Dioxide Published in Journal AWWA

    October 17, 2014

    In 2004, SPL published the first field trial of chlorine dioxide for control of Legionella pneumophila applied to a hospital's secondary water distribution system. (See Keeping Legionella out of Water SystemsSidari, F.P., Stout, J.E., VanBriesen, J.M., Bowman, A.M., Grubb, D., Neuner, A., Wagener, M.M., Yu, V.L., Journal of the American Water Works Association, Vol. 96, No. 1, pp. 111-119, January 2004.) The results of that 18-month study, which appeared in the Journal AWWA, showed chlorine dioxide was effective in controlling Legionella.

    Recently, SPL conducted a case study of that same hospital, which had been using chlorine dioxide since 2000, to validate the conclusions of the 2004 study and evaluate long-term use of this biocide. The article Maintaining Legionella Control in Building Water Systems by Frank P, Sidari III, Janet E Stout. et al., appears in the October issue Journal American Water Works Association

  • Legionella Point of Use Filter Meets Manufacturer’s Claim of 62-Day Efficacy

    October 17, 2014

     A point-of-use (POU) filter meets manufacturer’s claims for controlling Legionella for 62 days according to a study in the October issue of the American Journal of Infection Control released online.

    October 17, 2014 (Pittsburgh)—A Legionella point-of-use (POU) filter meets manufacturer’s claims for controlling the bacteria for 62 days says according to the October issue of the American Journal of Infection Control released online.

    Special Pathogens Laboratory researchers, Janet E. Stout, PhD, and Julianne Baron, PhD, collaborated with a cancer center in Northwestern Pennsylvania to evaluate the next generation faucet filter called Q point (Pall Medical).

    The 17-week study showed the filter controlled Legionella for 62 days—the first to surpass the 30-day life cycle of other POU filters currently on the market.

    According to Dr. Stout, director of Special Pathogens Laboratory, “This new filter could provide a more convenient and cost-effective solution for infection prevention due to exposure to waterborne pathogens like Legionella and Pseudomonas for immune-compromised patients.”

    In addition to controlling Legionella, the filter entirely eliminated heterotrophic plate count bacteria—total bacteria in water used as an indicator for biocide effectiveness and water quality—for the first two weeks.

  • Legionella Disinfection Changes Microbiome in Hospital Hot Water, Study Shows

    October 09, 2014

    Legionella disinfection changes the microbial ecology or microbiome in a hospital hot water system, says a study published in PLOS ONE Journal.

    “As secondary disinfection is becoming more widely used to control Legionella, we need to understand how these chemicals change the bacterial flora in the water and what these changes imply,” says Janet E. Stout, PhD, director of Special Pathogens Laboratory.

    Dr. Stout, principal investigator of the study, and researcher Julianne Baron, PhD, from the University of Pittsburgh Graduate School of Public Health used next generation molecular sequencing methods—high throughput Illumina 16S rRNA region sequencing and 454 sequencing, to evaluate samples from a hospital’s hot water system treated with onsite monochloramine.

    The results in, Shift in the Microbial Ecology of a Hospital Hot Water System Following the Introduction of an On-Site Monochloramine Disinfection System, show an immediate shift in the microbial population or microbiome. These techniques along with traditional culture, showed changes in Legionella, including rebound during a period of ineffective treatment.

    “The microbiome of the built environment is a new frontier of science. As science and medicine are exploring how bacteria can impact health, it only makes sense to look at the changes in our drinking water,” says Stout. “More studies are needed to understand the consequences of Legionella disinfection technologies in water systems.”