Maryland, December 6, 2004 (ENS): A new study
warns that people could be exposed to bacteria that
are resistant to antibiotics from breathing the air
emitted from concentrated swine feeding facilities.
Researchers detected bacteria resistant to at least
two antibiotics in air samples collected from inside
a large swine operation in the Mid-Atlantic region.
Until now, little research has been conducted regarding
the presence of antibiotic resistant bacteria in the
air within industrial swine facilities.
The study adds to the understanding of various pathways
by which humans can be exposed to antibiotic resistant
bacteria, such as consumption of retail pork products
and contact with or ingestion of soil, surface water
and groundwater near production operations.
The use of antibiotics in industrial animal production
has an impact on the emergence of antibiotic resistant
bacteria that threaten human health.
Using antibiotics in animals can decrease the effectiveness
of the same antibiotics used to combat human infections.
The non-therapeutic use of antimicrobials in livestock
production makes up at least 60 percent of the total
antimicrobial production in the United States.
Non-therapeutic doses of drugs are given to swine to
promote growth and improve feed efficiency - not to
treat actual swine disease.
"These research findings add another piece to
our understanding of human exposure to antibiotic resistant
bacteria," said Dr. Kellogg Schwab, a coauthor
of the study and an assistant professor in the Bloomberg
School of Public Health's Department of Environmental
Health Sciences and the study's corresponding author.
"Finding and documenting the multiple environmental
pathways of exposure are critical to finding solutions
to the growing, serious problem of antibiotic resistant
bacteria in humans," Schwab said.
The airborne bacteria samples that were found to be
resistant to more than one drug were - enterococcus,
coagulase negative staphylococci, and viridans group
These bacteria are associated with a variety of human
The study found that 98 percent of the isolated samples
were resistant to at least two of the following antibiotics:
erythromycin, clindamycin, virginiamycin, and tetracycline.
All of these drugs - or their human drug counterparts
- are important antibiotics in the treatment of human
By contrast, none of the bacterial samples were resistant
to vancomycin - an antibiotic that has never been approved
for use in swine production in the United States.
The researchers believe workers at concentrated animal feeding operations are
at greatest risk for airborne exposure to antibiotic
resistant bacteria. The same workers may also become
reservoirs of drug resistant bacteria that can be spread
to family and the broader community, they said.
The study, published last week online in the journal
"Environmental Health Perspectives" also raises
questions about the spread of drug resistant bacteria
to areas beyond the immediate site through ventilation
fans and by the application of manure from feeding operations
to off-site fields.