In March 2016, we sampled tap water from 5 homes and 6 small businesses in Flint, with ALL testing culture-negative for Legionella. We used a standard culture-method often used by hospitals to determine if there is a risk of Legionnaire’s Disease outbreak. This is good news. We will be following up with another sampling this summer when the weather is warmer and there is more of a tendency of Legionella bacteria to grow.
We are also examining the water samples we have collected more closely using DNA-based methods. The DNA methods may help us detect lower levels of Legionella that we couldn’t see with culture and also identify different kinds of Legionella, but the trade-off is that we will not be able to tell the difference between live and dead bacteria. That is why the culture method is considered the standard for determining risk of getting Legionnaires’ Disease from tap water.
Using the best available science, the sampling we performed in March 2016 showed that if any living Legionella were present, their levels were low the day of testing. There is always some risk of Legionnaire’s Disease from tap water, but our current results from March suggest the risk was not concerning at any of our sample sites in Flint. We will remain vigilant in our tracking and testing of this potential problem in Flint homes.
We have been getting questions from concerned parents about the Legionella announcement made earlier today and if there is a risk to taking showers.
1. Is it safe for me and my kids to shower in the water now?
A. We agree with DHHS that this problem, is probably behind us all, even it if was caused by the Flint River water. It is safe to shower now whether you are an adult or a child. When we say “safe,” we mean it is no riskier to shower in Flint now than in any other U.S. city.
2. Is this (was this) a risk only in high-rise buildings or plumbing systems in small homes can harbor Legionella pneumophila too?
A. During August of 2015 we focused our Legionella testing on residences and smaller buildings like McDonald’s throughout the city. Despite looking as hard as we could, we could find no trace of the Legionella bacterial strain that causes disease. So in homes and small buildings at least, based on our data, the risk of exposure was relatively low. We published those data on our website earlier in the year, and frankly, we were a little surprised there was not more Legionella.
However, just before the switch back to Detroit, we sampled larger buildings, and we found very high levels of the types of Legionella that cause disease. So we tend to feel, that the risk of exposure, was much higher in the bigger buildings.
3. The water has been “bleachy” in the last few days. Is that a risk?
A. This is actually a good sign that your risk of Legionella very low. The “bleach” or chlorine actually kills Legionella bateria.
Acknowledgements: Dr. Amy Pruden, Dr. Marc Edwards, Siddhartha Roy
During our trip, we collected samples from nine businesses located throughout the city of Flint, including eight of Flint’s designated monitoring sites and a business located in close proximity to the drinking water treatment plant, and seven homes of Flint water consumers. For comparison, we also collected water from four businesses that receive water from Detroit. At each of these sites, we collected both water samples and swabs of bacteria growing on the surface within the faucet, known as the biofilm.
Here we report on our results for several additional OPs, alongside the previous results, based on presence of DNA markers specific to each bacterium. Pathogenic species are indicated in red. Mycobacterium spp. represents a genus of bacteria that includes several pathogenic and non-pathogenic species. Vermamoeba vermiformis is of interest because it is an amoeba that may play an important role in the life cycle of some pathogens, such as Legionella pneumophila. In addition, we attempted to culture pathogenic Staphylococcus species from the samples.
Table 1 demonstrates that we did not detect quantifiable levels of Pseudomonas aeruginosa, Legionella pneumophila, orMycobacterium avium in water or biofilm samples collected from any of the sixteen sites in Flint. Acanthamoeba polyphaga was found in the biofilm at 3 sites in Flint. Acanthamoeba polyphaga is an amoeba that is often associated with eye infections of individuals using tap water for contact lens care rather than sterile saline, but has also been associated with skin and respiratory infections. More information on this amoeba can be found here.
Water from each site was also cultured using methods specific to growing Staphylococcus. Only two sites resulted in Staphylococcus growth. DNA from 10% of the resulting colonies were sequenced to identify the species. All sequences were identified to belong to either Staphylococcus epidermidis or Staphylococcus hominis. Both species are frequently found on the skin of healthy individuals and are not typically pathogenic.
Although the number of samples collected has been small and were collected from each site on a single date, our results do not indicate the presence of pathogenic OPs in Flint water, with the exception of sporadic detection of Acanthamoeba polyphaga in biofilm samples. Overall, this limited sampling, indicates that from a microbiological perspective Flint water does not seem to pose a health risk worse than many other U.S. cities that we have sampled. However, the chronically low chlorine residuals throughout the distribution system, suggest that this issue should be the subject of continued scrutiny.
Additional Notes: The method we used to quantify the pathogens is called quantitative polymerase chain reaction (qPCR). It works by detecting DNA specific to the target microorganisms, making the method very specific, but also very sensitive, as an organism does not necessarily need to be alive or culturable for us to identify that it is present. The minimum threshold of target bacteria, or more accurately the bacteria’s DNA that must be present in the 1-liter samples that we collected is 10 DNA copies per mL or 104 copies in the entire swabbed biofilm. This is the best available and most sensitive method of OPs detection.
Analysis and write-up: Emily Garner
Acknowledgements: Dr. Marc Edwards and Dr. Amy Pruden
We have long known about the dangers associated with waterborne pathogens. Fecal contamination of drinking water sources can lead to gastrointestinal illness and deaths caused by a variety of waterborne pathogens. We control for these risks by 1) selecting clean water sources for treatment, 2) treating the water to remove particles and bacteria by filters, and 3) disinfecting water with chlorine. Treatment plants have to prove they are meeting very high standards in protecting the public from this danger, by frequently measuring filter efficiency and chlorine levels at the treatment plant. In addition, utilities also have to double-check their control of this threat, by sampling their water pipelines for indicator bacteria which are present at very high concentrations in feces, such as coliforms and E. coli, and also maintaining significant levels of chlorine as water is transported to homes.
In recent decades, we have also come to recognize that fecal contamination is not the only source of waterborne pathogens in our drinking water. These other bacteria do not come from fecal contamination, but rather they grow in pipes and homes themselves, and are commonly referred to as Opportunistic Pathogens, or OPs for short. The presence of OPs in drinking water is a danger that is not directly addressed by existing Federal Regulations, despite the fact that an OP, Legionella pneumophila is now known to be the most frequently reported causative agent of waterborne disease outbreaks (and deaths) in the United States.
The impacts that OPs can have on human health are numerous, and they generally do not come from drinking the water. For example, Legionella pneumophila (the bacterium which causes Legionnaire’s disease) and Mycobacterium avium live in pipes, and human exposure occurs when consumers breath tiny water droplets in the air from showers or washing hands. Staphylococcus aureus can lead to skin infections when it contacts open cuts or existing irritations. Pseudomonas aeruginosa can lead to a variety of infections: lung and blood stream infections, skin irritations, and infections of the eye or ear.
Most OPs are not regulated or routinely measured in drinking water. Legionella is only regulated in water as it leaves the treatment plant, which is the location that is least likely to have high levels of Legionella, and the regulation does not do enough for public health protection. However, the conditions which are associated with a typical building’s plumbing, can create ideal conditions for these bacteria to take hold, such as warm water, so Legionella can be present at very high levels in homes even when it is not detected at the treatment plant.
Residents of Flint have also reported many symptoms (see, here, here and here) which are consistent with those associated with some infections caused by waterborne OPs, such as skin irritations. However, it is unclear whether OPs may be contributing to this problem due to a lack of water testing, and difficulties in linking human health problems to water exposure. There is some indication that in March 2015, the Health Department was exploring possible links between drinking water and cases of Legionnaire’s disease in Genesse County.
Additional water testing targeting OPs, particularly of samples collected at the point of use within homes, could offer valuable information regarding the microbial water quality of the drinking water available to residents of Flint.
Primary Author: Emily Garner
Acknowledgements: Dr. Marc Edwards, Dr. Brandi Clark and William Rhoads