Antibiotic-resistant bacteria in lagoon growing worry
A Harbor Branch research team took sediment samples in the lagoon this summer and found a shocking surprise – a higher-than-expected amount of antibiotic-resistant bacteria.
“We began our study in 2011 and the amount of antibiotic-resistant bacteria was stable from 2011 to 2012,” said scientist Peter McCarthy, “but there was a substantial increase this year at both locations we tested.”
The increase is worrying because the water-borne bacteria could pass drug-resistant genes to human pathogens, nasty little squirmers that cause disease and death in people.
“Sometimes these bacteria become an issue in human disease, as with MRSA, the antibiotic-resistant staff germ they have problems with in hospitals,” McCarthy says.
MRSA – short for methicillin-resistant Staphylococcus aureus – has plagued hospitals around the world for more than 40 years.
Earlier this year, health officials in the U.S. and UK issued dire warnings about a new class of drug-resistant bacteria potentially worse than MRSA that could make routine operations fatal for as many as one in six patients.
Sally Davies, the United Kingdom’s chief medical officer, says carbapenem-resistant enterobacteriaceae – CRE for short – pose a “catastrophic risk” to human health.
Tom Frieden, director of the federal Centers for Disease Control and Prevention, calls the rapidly spreading CRE germ, which has been found in 18 percent of hospitals offering long-term critical care, a “nightmare bacteria.”
According to McCarthy, there is no evidence drug-resistant bacteria in the Indian River Lagoon have contributed to human disease, but with increasing levels of the bacteria in the environment, he says the potential for gene-transference exists.
McCarthy and his colleagues take samples at a spot adjacent to Harbor Branch and several miles south.
“We know here at Harbor Branch we have pretty good water exchange and a relatively un-impacted environment,” McCarthy says. “When you get down to the mouth of Taylor Creek in Fort Pierce you have canal input and urban and agricultural runoff coming in.”
Over the three-year testing period, antibiotic-resistant bacteria levels have been consistently higher at the creek outlet than at Harbor Branch, but both areas saw a proportionately similar increase this year.
The testing procedure is straightforward. “We collect samples at both sites the same day,” McCarthy says. “We wade out a little ways and scoop up some sediment in a sterile vessel and bring it back to the lab.”
In McCarthy’s lab, the bacteria-laden sediment is placed on growth medium, some without antibiotics, others with low, medium or high concentrations of antibiotics. When bacteria that flourishes on un-medicated growth medium also multiply on medium infused with antibiotics, it demonstrates drug resistance.
Harbor Branch scientists saw a lot of that this year. “It was a sizable increase over previous years,” says McCarthy, who is seeking funds to continue his research to better understand the sources and significance of antibiotic-resistant bacteria in the lagoon.
“Somewhere in the environment there is a substantial increase of these bacteria and we are looking for additional funding to try and work out where they are coming from. We have some hypotheses – it is likely they are coming from upstream somewhere – but we need to test the hypotheses.”