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07 Diagnostic results review

You leave the farm after going over the treatment protocol with Charlie.  He is understandably worried, but you manage to sell him on the idea that we can do some things to prevent this problem from happening in his next groups placed.  You ask him to call you in four days with a progress report, and you tell him that the diagnostic results will be back at about the same time.

When the lab results are in, you see that you were right.  It looks like F18.  The jejunal epithelium was covered by rod-shaped bacteria.  The lab cultured predominant hemolytic E. coli.  Genetic analysis showed it to be a toxin-producing F18 strain (Shiga toxin IIe and Stable Toxin A).  A Strep infection would have showed some distinct lesions in the brain, but they weren’t there.  The tissues were negative for PRRS and swine influenza.  F18 is now the definitive diagnosis.

 

“Diagnostic report”


You examine the antibiotic susceptibility profile.  Looks like you picked the right drugs.  You knew that with F18, antibiotic resistance could develop quickly in a population or at a site.  However, just because Gentamicin worked this time, it won’t necessarily work next time.  You run through the list of antimicrobial agents to which this lab screens for susceptibility…

  • Ampicillin
  • Apramycin
  • Ceftiofur
  • Chlortetracycline
  • Clindamycin
  • Danofloxacin
  • Erythromycin
  • Florfenicol
  • Gentamicin
  • Neomycin
  • Oxytetracycline
  • Spectinomycin
  • Sulphachloropyridazine
  • Sulphadimethoxine
  • Sulphathiazole
  • Tiamulin
  • Tilmicosin
  • Trimethoprim/Suphamethoxazole
  • Tylosin


The diagnostic lab has given you a table of antimicrobial agent resistance profiles from Beta-hemolytic E. coli isolations over the years.  This table gives you some confidence in the agents you might want to use.

Beta hemolytic E. coli susceptibility table

 

Resistant

Susceptible

Grand Total

% of isolates susceptible

Amikacin

 

1

1

100%

Imipenem

 

1

1

100%

Orbifloxacin

 

1

1

100%

Enrofloxacin

1

58

59

98%

Ceftiofur

56

283

339

83%

Florfenicol

12

38

50

76%

Apramycin

104

234

338

69%

Gentamicin

108

225

333

68%

Trimethoprim/Sulphamethoxazole

118

236

354

67%

Carbadox

5

10

15

67%

Neomycin

207

146

353

41%

Ampicillin

232

118

350

34%

Sulphachloropyridazine

321

30

351

9%

Spectinomycin

251

14

265

5%

Sulphadimethoxine

328

18

346

5%

Chlortetracycline

336

9

345

3%

Oxytetracycline

343

9

352

3%

Tilmicosin

330

1

331

0%

Clindamycin

354

 

354

0%

Erythromycin

353

 

353

0%

Tiamulin

353

 

353

0%

Tylosin (Tartrate)

353

 

353

0%

Sulphathiazole

311

 

311

0%

Penicillin

60

 

60

0%

Amoxicillin/Clavulanic Acid

1

 

1

0%

Cefazolin

1

 

1

0%

Cefoxitin

1

 

1

0%

Cephalothin

1

 

1

0%

Rifampin

1

 

1

0%

Tetracycline

1

 

1

0%

Ticarcillin

1

 

1

0%

Ticarcillin/Clavulanic Acid

1

 

1

0%



On more than one occasion, you have seen profiles come back showing NO effective antibiotics against F18 E. coli.  You remember the Animal Medicinal Drug Use Clarification Act (AMDUCA).  When the approved swine drugs are not effective according to the algorithm, the law allows for a veterinarian to make appropriate use of this decision-making flow chart.  You review the AMDUCA requirements (see link on next page).

 

 

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