Interpretation of Bulk Tank Culture Results
(Adapted from C. S. Petersson-Wolfe and J. Currin, 2017)
The reference guide for mastitis-causing bacteria below was developed to provide a succinct yet comprehensive summary of the major classes of bacteria that cause mastitis in dairy cows as a rapid reference for dairy farmers and bovine practitioners. In addition, the guide denotes the environmental or contagious nature of each pathogen, its source in the cow’s surroundings, mechanisms of spread, methods of control, and treatment strategies.
| Classification | Bacteria | Contagious or Environmental | Source | Spread | Control | Treatment* |
|---|---|---|---|---|---|---|
| Staphylococcus spp. | Staph. aureus | Contagious | Infected udders, hands of milkers | Milking time | Post-dip, DCT1, segregation and cull if necessary | Label recommendations for broad-spectrum antibiotics, if early lactation – 5-7 d pirlimycin, do not treat chronic infections |
| Coagulase (-) staph. & S. hyicus | Neither | Skin flora & occasionally environment | Infect teat canal from skin sources | Post-dip, DCT | Treat clinical cases (broad spectrum), DCT | |
| Streptococcus spp. and Enterococcus spp. | Strep. agalactiae | Contagious | Infected udders | Milking time | Milking time hygiene, post-dip, DCT | Label recommendations for broad-spectrum antibiotics |
| Strep. dysgalactiae | Contagious and environmental | Infected udders and environment | Milking time & environmental contact | Milking time hygiene, pre- & post-dip, DCT, teat seal | ||
| Strep. uberis | Environmental | Environment – early dry period | New IMI2during early dry period | Milking time hygiene, pre- & post-dip, DCT, teat seal | ||
| Environmental strep & Enterococcus spp. | Environmental | Environment | Environmental contact | Milking time hygiene, pre- & post-dip, DCT, teat seal | ||
| Gram negatives | Escherichia coli | Environmental | Bedding, manure, soil | Environmental contact | Cows clean & dry, use of sand bedding, pre-dip, a J5 vaccine | Do not treat mild or moderate severity cases. Systemic cases – 2-3 L hypertonic saline IV, followed by oral fluid therapy, NSAID** and injectable antibiotics |
| Klebsiella spp. | Environmental | Organic bedding | Environmental contact | Avoid sawdust & recycled manure, pre-dip, J5 vaccine | ||
| Enterobacter spp. | Environmental | Bedding, manure, soil | Environmental contact | Cows clean & dry, pre-dip (no chlorhexidine products) | ||
| Serratia spp. | Environmental | Soil and plants | Environmental contact | Cows clean & dry, pre-dip (no chlorhexidine products) | 180-300 ml hypertonic saline IMM infusion | |
| Pseudomonas spp. | Environmental | Water & wet bedding | Environmental contact | No water use in parlor, no cooling ponds, sand bedding, a J5 vaccine | ||
| Proteus spp. | Environmental | Bedding, feed & water | Environmental contact | Not much known, use of sand bedding, a J5 vaccine | ||
| Pasteurella spp. | Probably contagious | Upper respiratory tract of mammals and birds | Unknown – likely cow to cow | Prevent teat injuries, remove affected cows from herd | Do not respond to IMM treatment | |
| Other | Yeast & mold | Environmental | Soil, plants, water | Dirty infusions | Aseptic infusions | No treatment |
| Corynebacterium bovis & other coryneforms | Contagious | Infected udders | Cow to cow | Post-dip | Treat clinical cases and DCT | |
| Prototheca | Environmental | Soil, plants, water | Dirty infusions | Aseptic infusions | No treatment | |
| Bacillus spp. | Environmental | Soil, water, air | Dirty infusions | Aseptic infusions | Broad-spectrum antibiotic | |
| Arcanobacterium pyogenes | Contagious/ Environmental | Teat injuries | Flies | Fly control | Kill affected quarter or remove from herd |
Information obtained from NMC Laboratory Handbook on Bovine Mastitis and veterinary consultation for treatment recommendations).
*These are general treatment recommendations; actual recommendations may vary from herd to herd. Please consult your veterinarian.
**Nonsteroidal anti-inflammatory drugs.
1 – DCT, dry cow therapy; 2 – IMI, intramammary infection; 3 – IMM, intramammary.
Adapted from Reference guide for mastitis-causing bacteria authored by C. S. Petersson-Wolfe and J. Currin, Virginia Tech Mastitis & Immunology Laboratory & Virginia Maryland Regional College of Veterinary Medicine (Information obtained from NMC Laboratory Handbook on Bovine Mastitis and veterinary consultation for treatment recommendations).