**3.1.2** *Salmonella* **from dairy cattle**

224 Salmonella – A Dangerous Foodborne Pathogen

I-1 isolate

a

b

c

d

e

f

g

II-1 isolate

III-1 isolate

IV-4 isolates

V-28 isolates

VI-17 isolates

VII- 2 isolates

VIII-3 isolates

IX-1 isolate

Fig. 1. Dendogram generated from the *Xbal* patterns of the 58 *Salmonella* isolates using UPGMA clustering analysis with the BioNumerics software. A positive tolerance of 1.5 %

Of the 212 cattle (115 adult cattle, 97 calves) investigated by Theis et al (2007), 15 (7%) tested positive for *Salmonella*. The prevalence of *Salmonella* among adult cattle and calves was 9/115 (7.8%) and 6/97 (6.2%), respectively. The 15 cattle that tested positive to *Salmonella* were distributed in three of the four counties with the majority originating from Billings county and no animal from Mercer county as follows: Stark (7/92, 7.6%), Billings (5/30, 6.6%), Dunn (3/60,5.0%), and Mercer (0/30, 0.0%). Thirteen (87%) of the 15 *Salmonella* isolates recovered were *Salmonella* Typhimurium (Copenhagen) and the rest (2/15, 13%) were *Salmonella* Worthington. All 15 *Salmonella* isolates from healthy cattle were susceptible to Apramycin, Ceftiofur, Entrofloxacin, Gentamicin, and Neomycin. All samples were resistant to Chlortetracycline, Clindamycin, Erythromycin, Florfenicol, Oxytetracycline,

Percent similarity

was chosen.

**3.1.1** *Salmonella* **from ranch cattle** 

In a study of Salmonella occurrence in dairy cattle (Khaitsa et al, 2004), 5 out of 30 cows (17%) tested positive for *Salmonella.* A sensitivity test to 20 antibiotics was performed on the 5 *Salmonella* isolates and the results were similar for all the 5 isolates except for only one isolate that was sensitive to Sulphachloropyridazine and Sulphadimethoxime and gave an intermediate result to Sulphathiazole (Table 4).


S = Sensitive, I = Intermediate. \*These 3 antimicrobials are the only ones that gave a different result (sensitive or intermediate) to 1 of the 5 isolates; the other 4 isolates were all resistant to them). For all other antimicrobials the results were the same for all 5 Salmonella isolates.

Table 4. Antimicrobial Sensitivity Results to 5 *Salmonella* Isolates from dairy cattle. R = Resistant,
