Airborne Multidrug-Resistant Bacteria Isolated from a Concentrated Swine Feeding Operation

Abstract

The use of nontherapeutic levels of antibiotics in swine production can select for antibiotic resistance in commensal and pathogenic bacteria in swine. As a result, retail pork products, as well as surface and groundwaters contaminated with swine waste, have been shown to be sources of human exposure to antibiotic-resistant bacteria. However, it is unclear whether the air within swine operations also serves as a source of exposure to antibiotic-resistant bacterial pathogens. To investigate this issue, we sampled the air within a concentrated swine feeding operation with an all-glass impinger. Samples were analyzed using a method for the isolation of Enterococcus. A total of 137 presumptive Enterococcus isolates were identified to species level using standard biochemical tests and analyzed for resistance to erythromycin, clindamycin, virginiamycin, tetracycline, and vancomycin using the agar dilution method. Thirty-four percent of the isolates were confirmed as Enterococcus, 32% were identified as coagulase-negative staphylococci, and 33% were identified as viridans group streptococci. Regardless of bacterial species, 98% of the isolates expressed high-level resistance to at least two antibiotics commonly used in swine production. None of the isolates were resistant to vancomycin, an antibiotic that has never been approved for use in livestock in the United States. In conclusion, high-level multidrug-resistant Enterococcus, coagulase-negative staphylococci, and viridans group streptococci were detected in the air of a concentrated swine feeding operation. These findings suggest that the inhalation of air from these facilities may serve as an exposure pathway for the transfer of multidrug-resistant bacterial pathogens from swine to humans.

Antibiotic Resistance in the Environment, with Particular Reference to MRSA

“…Despite the move towards automated milking practices, reducing contact between humans and untreated milk, the production of aerosols in milking parlors may put workers, as well as other cows, at risk from contamination (Roberson et al, 1994). Similarly, aerial contamination has been noted in pig barns (Gibbs et al, 2004), and in aerosols produced by confined swine-feeding operations (Chapin et al, 2005;Sapkota et al, 2006), and pig feeds have been implicated as potential sources of contamination of tetracycline-resistant S.…”

Molecular Analysis of Bacterial and Circovirus Bioaerosols in Concentrated Animal Feeding Operations

“…CAFO workers, particularly those working with swine and poultry, are at the forefront of risk for emerging zoonotic diseases of substantial public health concern, including avian influenza (Nicholson et al 2003;Koopmans et al 2004), swine influenza (Olsen et al 2002;Myers et al 2006), and multidrug resistant pathogens (Chapin et al 2005;Scott et al 2005). Consequently, a better understanding of CAFO airborne microbiology and development of sensitive surveillance protocols are needed.…”

Impact of antibiotics used as growth promoters on bacterial resistance

“…Penicillins and tetracyclines were the first to be used as feed supplements in swine, poultry and beef cattle in concentrations which correspond to 10% or 1% of therapeutic doses (EMEA, 1999; Marshall and Levy, 2011). Tetracycline, chlortetracycline and oxytetracycline are most frequently used in poultry, and ampicillin, bacitracin, erythromycin, lincomycin, virginiamycin and tetracycline in swine production (Chapin et al, 2005; Abrožič Avguštin, 2012).…”

“…This practice has been maintained in many countries despite the fact that repeated exposure of bacteria to subminimum inhibitory concentrations was identified as a key factor which induces resistance (Kemper, 2008; EMEA, 1999; Ambrožič Avguštin, 2012). More than half of the total annual antibiotic production in the US and some other countries is spent in food-animal production (Wang and Yu, 2012), and as much as 60-80% of the total is used for non-therapeutic purposes (Chapin et al, 2005). Excessive use of antibiotics in animal husbandry is connected to high risks of the selection, spread and the persistence of antimicrobial-resistant bacteria.…”