Hurricane Harvey made landfall in Texas on
August 25, 2017, bringing more than 50 inches of rain and extreme
flooding to the city of Houston. In addition to wreaking havoc on
buildings and infrastructure, urban floodwaters harbor hidden menaces in
the form of bacteria that can cause disease. Now, researchers have
surveyed the microbes that lurked in Houston floodwaters, both inside
and outside of homes. They report their results in Environmental Science & Technology Letters.
One of the most destructive hurricanes to hit the U.S. since Katrina
in 2005, Harvey damaged more than 100,000 homes in the Houston area. In
addition, the storm flooded numerous wastewater treatment plants,
causing widespread discharge of untreated or partially treated sewage.
Raw sewage contains fecal bacteria, like E. coli, and other potential pathogens, such as Salmonella enterica and Clostridium perfringens.
Also, bacteria in sewage can possess elevated levels of
antibiotic-resistance genes, which they can share with other microbes in
the environment. Few studies have examined pathogenic bacterial
exposures and antibiotic resistance in residential communities affected
by urban floodwaters. So, Lauren Stadler and her colleagues wanted to
survey the bacteria in post-Harvey floodwaters on Houston streets,
inside homes and in bayous, as well as in sediments left by the receding
waters.
The researchers found that E. coli levels in two of
Houston's major bayous were significantly elevated in the immediate
aftermath of Harvey compared with numbers obtained before the hurricane,
but gradually decreased over two months after the storm to pre-storm
levels. Similarly, antibiotic-resistance gene levels were highest three
days after the storm. The team next compared microbial communities in
floodwaters both inside and outside homes. The highest levels of fecal
bacteria, human pathogens and antibiotic resistance genes occurred in
homes with stagnant floodwater inside. When Stadler and coworkers
analyzed sediment samples from public parks and residential communities,
they detected abundant possible pathogens, but they were different from
the pathogens found in flood and bayou waters. The study indicates that
residents and relief workers should exercise caution to prevent coming
into contact with harmful microbes in the aftermath of extreme floods,
especially in stagnant indoor waters, the researchers say.
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