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United States Department of Agriculture

Agricultural Research Service

Title: Antimicrobial Resistance and Serotype Prevalence of Salmonella Isolated from Dairy Cattle in the Southwestern United States

Authors
item Edrington, Thomas
item Schultz, Carrie
item Bischoff, Kenneth
item Callaway, Todd
item Looper, Michael
item Genovese, Kenneth
item Jung, Yong Soo
item McReynolds, Jackson
item Anderson, Robin
item Nisbet, David

Submitted to: Microbial Drug Resistance
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 18, 2003
Publication Date: May 3, 2004
Citation: Edrington, T.S., Bischoff, K.M., Callaway, T.R., Looper, M.L., Genovese, K.J., Jung, Y., Anderson, R.C., Nisbet, D.J. 2004. Antimicrobial resistance and serotype prevalence of Salmonella isolated from dairy cattle in the southwestern United States. Microbial Drug Resistance. 10(1):51-56.

Interpretive Summary: Dairy cattle may contain the bacteria Salmonella that may cause human food related illness. There are many different types of Salmonella. Antibiotics (drugs) used to treat these bacteria may not always work because some of the bacteria are resistant to them. The purpose of the present study was to look at the different types of Salmonella in dairy cattle and examine if these types of Salmonella are killed by antibiotics used by veterinarians and physicians. We examined almost 400 Salmonella samples and found 22 different types. Some antibiotics are not effective against these bacteria, however the most common types of Salmonella were killed by all the antibiotics tested. The drugs that did not kill the Salmonella were the kind used by veterinarians, not the drugs used in humans that were able to kill the Salmonella.

Technical Abstract: Mature dairy cattle were sampled over a two-year period (2001 - 2002) on six farms in New Mexico and Texas. Fecal samples were collected via rectal palpation, cultured for Salmonella, and one isolate from each positive sample serotyped. Three isolates of each serotype, with the exception of Salmonella Newport (n = 12), were examined for antimicrobial susceptibility using the broth micro-dilution technique. Twenty-two different serotypes were identified from a total of 393 Salmonella isolates. Montevideo was the predominant serotype (27%) followed by Mbandaka (15%), Senftenberg (11.4%), Newport (6.4%), Anatum (4.8%) and Give (4.8%). Salmonella Typhimurium and Dublin, two frequently reported serotypes, accounted for only 1% of the observed serotypes in this study. Sixty-four percent of the serotypes were susceptible to all of the antimicrobials, 14% were resistant to a single antibiotic, and 22% were multi-resistant (2 to 11 types of resistance). All isolates tested were susceptible to amikacin, apramycin, imipenem, ceftriaxone, nalidixic acid, and ciprofloxacin. The most frequent types of resistance were to sulfamethoxazole, tetracycline, streptomycin, kanamycin, chloramphenicol, and ampicillin (ranging from 8.9 to 22.4%). Serotypes demonstrating multiple resistance included Dublin and Give (resistant to 3 or more antibiotics), Typhimurium (resistant to 5 antibiotics) and Newport (4 and 2 isolates resistant to 6 and 9 antibiotics, respectively). Class 1 integrons were present in only three isolates, two Salmonella Dublin and one Salmonella Newport. The most prevalent resistance patterns observed in this study were for antimicrobial agents commonly used in cattle, while all Salmonella isolates were susceptible to ceftriaxone and ciprofloxacin, antibiotics used in human medicine.

Last Modified: 7/24/2014