Writer: Kathleen Davis Phillips, (979) 845-2872, ka-phillips@tamu.edu
Contact: Dr. Suresh Pillai, (915) 859-9111
EL PASO — Disease-causing microbes lurking in water, soil and food now may be more easily found, says a scientist who developed new molecular detection methods.
Dr. Suresh Pillai, an environmental microbiologist at the Texas Agricultural Experiment Station, devised methods to genetically examine suspected microbes, using soil and water samples from more than 90 colonia wells along the heavily populated El-Paso-Mexico border. His methods also can be used on foods such as poultry.
“The risks (for human health in water sources) are real, but lacking was the science,” said Pillai, who arrived at the Texas A&M University System facility in El Paso 16 months ago from the Naval Medical Research Institute in Bethesda, Md. “We need to understand where the pathogens are and how they survive in order to know how to kill them.”
The immediate application was in the El Paso area where more than 100 colonias have inadequate water and sewage systems. That, coupled with the exploding urban population on both sides of the border, appeared to be culprits in causing human disease.
Pillai began with some facts: globally, about 60 percent of human disease is caused by microbes such as bacteria and viruses; the incidence of hepatitis A in El Paso County is five times the U.S. average; there is no clear information on the sources and routes of microbial infection in the El Paso area.
The normal method of identifying bacteria in soil or water has been to treat a culture medium with the sample and see what grows. That method takes as much as 12 times longer — two days compared to 4 hours — and often gives false positive and false negative results, he said.
Tests for contamination are further delayed by the culture medium method because the first run usually looks for indications of contamination such as fecal coliform. If that is found, additional tests are run to determine exact pathogens present.
“I hope that eventually we can go directly to looking for the pathogen so that effective preventive measures can be initiated immediately,” he said.
He said genetic methods of detecting and identifying the pathogens are a crucial step in decreasing the rate of infectious diseases that derive from substandard water and sewage systems.
“Usually, at least 1 percent of a community already would have been infected before the pathogen could be found in the water,” Pillai said. “With the genetic method, the specific pathogen could be detected, the source positively identified and a disinfection program could be started before a lot of people have been exposed.”
Pillai’s work has attracted the attention of the El Paso City County Health and Environmental District, according to Dr. Laurance Nickey, director.
Testing a grossly contaminated lake and tracking the source of a high rate of dysentery cases are two possible uses in El Paso for Pillai’s molecular analyses, Nickey said.
“We would like to be able to use such tests. We would have the capability then of being able to track down an outbreak, and we could do it quickly,” he said, noting that informal discussions on the possibility of such tests already have taken place.
For Pillai, understanding the impact of the population on water has been difficult because there is no database, that is, an assessment of what the water and soil was like around El Paso-Juarez historically in order to determine how or whether it has changed.
His first effort was to screen groundwater from about 30 wells in the colonias for specific bacterial pathogens and indicator bacterial species, then to determine their distribution and persistence in the groundwater.
He found a variety of bacterial populations, most of them natural and harmless, in the shallow aquifer along the El Paso-Juarez border. No strong correlation could be drawn between the bacterial diversity and depth of well. None of the bacteria that have been detected so far could be conclusively identified as of septic/sewage origin.
Nevertheless, the molecular tests gives community water managers the first jump at tracking quality.
“If the test shows even a single organism, that will force us to investigate the situation at a greater depth to determine possible human health risk,” Pillai said.
The same should be true with tests on food, according to Dr. Steven Ricke of College Station, a food microbiologist with the Experiment Station.
“Salmonella is a huge public health problem right now,” Ricke said. “Some of the probes Dr. Pillai has developed to use on salmonella in soils also work on poultry.”
Ricke said current tests for salmonella in poultry take as many as seven days whereas Pillai’s methods find results in six hours. The methods can be used to find salmonella at the poultry hatchery, which could help stop the pathogen before entire flocks are infected.
“Early detection is best, because salmonella is harder to control at the slaughter plant,” Ricke said. He said a cost-effective kit with easy to use, easy to interpret information now could be developed for use by the poultry industry to curb the salmonella problem.
“But this says the first step is possible, and with a little more thinking, a test could be made for commercial use,” Ricke said.
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