**2.2** *Salmonella* **from meats**

A study (Khaitsa et al 2007b) investigated the occurrence of *Salmonella* in raw and ready to eat turkey meat products, and factors associated with its occurrence in 959 turkey meat products (raw, n =614; and ready to eat (RTE), n = 345) purchased from four retail outlets in one city in the Midwestern United States. Another study (Kegode et al, 2008) investigated occurrence of *Salmonella* species, in 456 fresh raw meat products (turkey (n=87, 19.1%) chicken (n=123, 27.0%) chicken, pork (n=113, 24.8%) and beef (n=133, 29.2%)) purchased from five retail outlets in the Midwestern United States during a 12 week period (July 11, 2005 to October 3, 2005). Three stores were visited each week until all the stores had been visited a total of five times. The stores were sampled on different

Antimicrobial Drug Resistance and Molecular Characterization

Cattle

of *Salmonella* Isolated from Domestic Animals, Humans and Meat Products 221

Source Nature/state of the sample Number Percent Humans sick 179 41.2

Chicken retail chicken 4 0.9 Ducks ill/dead 1 0.2 Swine ill/dead 5 1.2

Turkeys ill/dead 3 0.7

Elk ill/dead 1 0.2

Bison fecal samples 1 0.2

Humans sick 179 41.2 Others beddings, linx etc 14 3.2 Total 434 100

Antimicrobial susceptibility of *Salmonella* isolates from the various sources was determined using the National Antimicrobial Resistance Monitoring System (NARMS) panel according to Food and Drug Administration and National Committee for Clinical Laboratory Standards (NCCLS) recommendation (Sensititre®, Trek Diagnostics System, Inc, Westlake, Ohio). Each isolate was screened for resistance using full-range minimum inhibitory concentration. The US National Antimicrobial Resistance Monitoring System (NARMS) panels were used to compare AMR levels between domestic animal and human isolates of the same genotype in order to assess a possible role of domestic animals in transfer of AMR of *Salmonella* isolated from human cases. The antimicrobials tested included ampicillin, apramycin, ceftiofur, chlortetracycline, clindamycin, enrofloxacin, erythromycin, florfenicol , gentamicin, neomycin, oxytetracycline, penicillin, spectinomycin, sulphachloropyridazine, sulphadimethoxime, sulphathiazole, tiamulin, tilmicosin, trimethoprim/ sulphamethoxazole and tylosin. Isolates were defined as resistant according to FDA recommended breakpoints. Breakpoints were defined as minimum drug concentration above which growth of the test

Frozen (-70°C) presumptive *Salmonella* cultures from the above sources were thawed and stabbed into 2ml tryptic soy agar (Difco, Becton Dickinson) deeps and shipped to the

Table 1. Sources of *Salmonella* isolates from clinical cases of humans and animals

**2.4 Antimicrobial resistance (AMR) testing**

isolate should not occur (Logue et al. 2003).

**2.5** *Salmonella* **serotyping and genotyping** 

feedlot (feces) 112 25.8 dairy (feces) 5 1.2 range(feces) 17 3.9 sick or dead cattle 59 13.6

meat 32 7.4

meat 1 0.2

days of the week during subsequent sampling times in order to minimize systematic bias associated with a particular day of the week. On each visit to a store, an average of 18 (range 11 to 23) fresh raw samples of all meat types (turkey, chicken, pork, and beef) and different meat products were obtained. Turkey products sampled included: ground breast, breast, breast cutlets, breast tenderloin, drumstick, and thigh. Chicken products comprised whole, quarter, breast, drumstick, thigh, wing, and kebab; pork products included ground, chops, steak, ribs, neck bones, roast, and stew; beef products consisted of ground beef-store brand, steak, stew, chuck, roast, ribs, round, loin, and kebab. Where available, different brands were selected including in-store packaged products. All products were raw and unfrozen. Samples were immediately transported to the laboratory on ice and processed within one hour of purchase.

For *Salmonella* isolation, meat samples were aseptically placed in a plastic WhirlPak bag (Nasco, Fort Atkinson, WI) with 200-400ml buffered peptone water, depending on the size of the meat sample. Approximately 200 ml and 400 ml of buffered peptone water added to any meat sample that was ≤ 1 Ib and > 1Ib, respectively. The bags were shaken manually for 3 minutes and left on ice for 20 minutes. All samples were subjected to an enrichment procedure. The buffered peptone water (BPW) rinse solution (20ml) was mixed with the same volume of double-concentrated lactose broth and enriched overnight at 35ºC. To culture *Salmonella,* 1.0 ml of the lactose enrichment broth was transferred into 9.0 ml of tetrathionate broth and incubated (42ºC for 24 hr.) The broth culture was then streaked onto XLT4 agar plates and incubated (24h at 37ºC). Suspect colonies (yellow with black centers) were stabbed in Triple Sugar Iron (TSI) agar slants and incubated (37ºC for 24 hr.) Presumptive *Salmonella* isolates, which formed red slants with black butts, were sent for serotyping to the US National Veterinary Services Laboratories (NVSL, Ames, IA).

Additionally, Tumuhairwe et al (2007) reviewed the temporal and spatial distribution of 1465 human salmonellosis cases associated with consumption of turkey meat in the US during the period 1990 to 2003 involving 49/50 states. Tumuhairwe et al (2007) also described the distribution of salmonellosis cases by vehicle and serotype. Trends in the outbreak numbers over time, and major serotypes across vehicles were tested by Cox-Stuart and chi-square test, respectively. Also, a study (Tumuhairwe et al, 2008) characterized 386 non-typhoidal salmonellosis cases in North Dakota from 2000 to 2005. Salmonellosis cases were extracted from the enteric disease investigation database of the North Dakota Department of Health (NDDoH) for the period 2000 to 2005.

#### **2.3** *Salmonella* **from clinical cases of humans and animals (cattle, chicken, ducks, swine, turkeys, elk and bison)**

A total of 434 frozen presumptive *Salmonella* isolates were included in the study. The isolates were previously obtained from 4 different sources comprising; 1) feces from apparently healthy feedlot, range and dairy cattle in an ongoing surveillance program in ND; 2) Clinical isolates from sick or dead cattle, chicken, ducks, swine, turkeys, elk and bison submitted to North Dakota State University-Veterinary Diagnostic Laboratory (NDSU-VDL) (2000-2005); 3) Frozen isolates from S*almonella* data bank in the NDSU-Veterinary and Microbiological Services (VMS) Department from previous food surveillance studies involving turkey, chicken and bison meat sold at the grocery stores at ND; and 4) 183 S*almonella* isolated from stools of human patients in ND (2000-2005) and stored at North Dakota Department of Health (NDDoH) (Table 1).


days of the week during subsequent sampling times in order to minimize systematic bias associated with a particular day of the week. On each visit to a store, an average of 18 (range 11 to 23) fresh raw samples of all meat types (turkey, chicken, pork, and beef) and different meat products were obtained. Turkey products sampled included: ground breast, breast, breast cutlets, breast tenderloin, drumstick, and thigh. Chicken products comprised whole, quarter, breast, drumstick, thigh, wing, and kebab; pork products included ground, chops, steak, ribs, neck bones, roast, and stew; beef products consisted of ground beef-store brand, steak, stew, chuck, roast, ribs, round, loin, and kebab. Where available, different brands were selected including in-store packaged products. All products were raw and unfrozen. Samples were immediately transported to the

For *Salmonella* isolation, meat samples were aseptically placed in a plastic WhirlPak bag (Nasco, Fort Atkinson, WI) with 200-400ml buffered peptone water, depending on the size of the meat sample. Approximately 200 ml and 400 ml of buffered peptone water added to any meat sample that was ≤ 1 Ib and > 1Ib, respectively. The bags were shaken manually for 3 minutes and left on ice for 20 minutes. All samples were subjected to an enrichment procedure. The buffered peptone water (BPW) rinse solution (20ml) was mixed with the same volume of double-concentrated lactose broth and enriched overnight at 35ºC. To culture *Salmonella,* 1.0 ml of the lactose enrichment broth was transferred into 9.0 ml of tetrathionate broth and incubated (42ºC for 24 hr.) The broth culture was then streaked onto XLT4 agar plates and incubated (24h at 37ºC). Suspect colonies (yellow with black centers) were stabbed in Triple Sugar Iron (TSI) agar slants and incubated (37ºC for 24 hr.) Presumptive *Salmonella* isolates, which formed red slants with black butts, were sent for

serotyping to the US National Veterinary Services Laboratories (NVSL, Ames, IA).

Additionally, Tumuhairwe et al (2007) reviewed the temporal and spatial distribution of 1465 human salmonellosis cases associated with consumption of turkey meat in the US during the period 1990 to 2003 involving 49/50 states. Tumuhairwe et al (2007) also described the distribution of salmonellosis cases by vehicle and serotype. Trends in the outbreak numbers over time, and major serotypes across vehicles were tested by Cox-Stuart and chi-square test, respectively. Also, a study (Tumuhairwe et al, 2008) characterized 386 non-typhoidal salmonellosis cases in North Dakota from 2000 to 2005. Salmonellosis cases were extracted from the enteric disease investigation database of the North Dakota

**2.3** *Salmonella* **from clinical cases of humans and animals (cattle, chicken, ducks,** 

A total of 434 frozen presumptive *Salmonella* isolates were included in the study. The isolates were previously obtained from 4 different sources comprising; 1) feces from apparently healthy feedlot, range and dairy cattle in an ongoing surveillance program in ND; 2) Clinical isolates from sick or dead cattle, chicken, ducks, swine, turkeys, elk and bison submitted to North Dakota State University-Veterinary Diagnostic Laboratory (NDSU-VDL) (2000-2005); 3) Frozen isolates from S*almonella* data bank in the NDSU-Veterinary and Microbiological Services (VMS) Department from previous food surveillance studies involving turkey, chicken and bison meat sold at the grocery stores at ND; and 4) 183 S*almonella* isolated from stools of human patients in ND (2000-2005) and stored at North Dakota Department of

laboratory on ice and processed within one hour of purchase.

Department of Health (NDDoH) for the period 2000 to 2005.

**swine, turkeys, elk and bison)** 

Health (NDDoH) (Table 1).

Table 1. Sources of *Salmonella* isolates from clinical cases of humans and animals
