Antibiotic-resistant bacteria are prevalent in people, wildlife and the water in northeastern Tanzania, but it’s not antibiotic use alone driving resistance.
Instead, researchers at Washington State University found transmission of bacteria in the environment is the most important factor. These conclusions come from a four-year study led by researchers from WSU’s Paul Allen School for Global Animal Health. The results of the study were just published in Nature Communications.
“We were surprised to find these microbes everywhere,” said Douglas Call, a Regents professor and associate director for research at the Allen School, “but it appears that within impoverished communities, there are many opportunities for bacteria to spread between animals and people via contact with waste or through consumption of contaminated food and water.”
The study, funded by the National Science Foundation, began in March 2012 and involved visiting 425 households from 13 villages throughout northeastern Tanzania. At each household, data was collected about people’s daily activities, after which researchers collected fecal samples from people, domestic livestock, chickens, dogs, and when present, wildlife. Water was also sampled.
The methods used by the team were unique from most studies, allowing collection and testing of more than 61,000 bacterial isolates. Depending on the community sampled, over 65% of bacteria from people were resistant to at least one of the nine antibiotics tested.
The prevalence of antibioticresistant bacteria was highest for people, but it was also high for other domestic animals even when those animals were never exposed to antibiotics. For example, in some communities up to 50 per cent of bacteria from dogs were antibiotic-resistant.
“In these communities, no one is treating their dog with antibiotics, and yet they have a high prevalence of resistance,” Call said. “It’s not an antibiotic use problem; they are coming into contact with antibiotic-resistant bacteria in the environment.”
Antibiotic-resistant bacteria were also prevalent in wildlife. More than 50 per cent of wildlife feces contained ampicillin-resistant bacteria, which was higher than the average across people, chickens, livestock, and dogs. The prevalence of resistance to the remaining eight antibiotics was highly correlated with results from domestic samples.
“We’ve got almost as much resistance on the wildlife side as the domestic side,” Call said. “This is one factor that shows how bacterial transmission plays such an important role in this system.” Antibiotic-resistant bacteria were also prevalent in water sources.
The World Health Organisation (WHO) recognises antibiotic resistance as a threat to global health and estimates 10 million deaths worldwide by 2050 if no effective interventions are made. While antibiotic-resistant bacteria are prevalent throughout the study area, these findings are the first step to address potential health risks.
“Hygiene and sanitation have to figure more prominently in efforts to combat antibiotic resistance,” said Mark Caudell, a firstauthor of this work. Caudell, is a former WSU researcher and now the regional social science coordinator for antimicrobial-resistance at the Food and Agriculture Organization of the United Nations.
“Until hygiene and infrastructure improves, and transmission begins to decline, antibiotic stewardship alone is unlikely to have much impact,” he said. In another development, cigarette butts pile up in parks, beaches, streets and bus stops, places where all types of littering are frowned upon.
Best estimates are that over five trillion butts are generated by smokers each year worldwide, and concern about their environmental impact has prompted studies of how they affect water and wildlife habitats. But despite their prevalence, almost no one has studied the airborne emissions coming off these tiny bits of trash.
When Dustin Poppendieck was asked to evaluate them, he was sceptical. As a measurement scientist at the National Institute of Standards and Technology (NIST) he realized there was no standard way of analysing the amounts of chemicals swirling in the air around cigarettes hours and days after they’d been put out, and he was intrigued.
But he also thought there might not be enough chemicals present to make the measurements meaningful. What his team found, however, was that a used butt - one that is cold to the touch - can in one day give off the equivalent of up to 14 per cent of the nicotine that an actively burning cigarette emits.
“I was absolutely surprised,” said Poppendieck. “The numbers are significant and could have important impacts when butts are disposed of indoors or in cars.” The NIST measurements were performed under an interagency agreement with the Food and Drug Administration as part of its analysis of the overall impact of cigarette smoking on people’s lives.
For a long time, most of the health impacts of smoking were misunderstood and often underestimated, in part because the emissions of cigarettes had not been fully assessed. Measurements and epidemiological studies over the last 50 years have improved our understanding of the health impacts of tobacco.
We now know a good deal about how cigarette smoking affects smokers’ own bodies as they inhale and exhale, referred to as mainstream smoking. Work has also been done to establish the health effects of second-hand smoke, which is the emissions from the end of a cigarette, pipe or cigar, and the smoke that is exhaled by smokers.
More recently, research has also examined third hand exposure, which comes from the chemical residue that stays on surfaces such as walls, furniture, hair, clothing and toys after a cigarette has been extinguished.
Like mainstream smoking and second hand smoke, third hand exposure can increase the risk of cancers and cause numerous other health problems, especially in the still-developing bodies and brains of infants and children.
The overall goal of the recent NIST study was to quantify the emissions from extinguished cigarettes and discover what happens to those emissions when the butts are left in different environments. Poppendieck’s team measured eight of the hundreds of chemicals typically emitted from cigarettes, including four that are on the FDA list of harmful and potentially harmful constituents.
They also measured triacetin, a plasticiser often used to make filters stiff. Filters were added to cigarettes in the 1950s. While they do collect part of what comes off a burning cigarette, they don’t fully negate the exposure from inhaling tobacco smoke.
Filters provide a kind of handle for cigarette users who want to avoid burning their lips or fingers, wasting tobacco, or having to pull stray tobacco bits off their tongues.
Triacetin can make up as much as 10 per cent of a filter, and its low volatility means it doesn’t evaporate quickly at normal temperatures, so it could be a good indicator of long-term emissions from a butt, Poppendieck explained.
The question that Poppendieck and his team considered, therefore, was not the impact of filters on smokers themselves. Rather, they focused on emissions from discarded butts, which are largely just used filters.