Some in vitro resistance patterns can be predicted based on the organism s identity.This influences the drugs used in susceptibility testing and in treatment. Below is a table of important intrinsic resistances. These resistances should be known byclinicians in order to avoid inappropriate and ineffective therapy.
Most Gram-negative Bacteria (Enterobacteriaceae, Pseudomonas spp.): Penicillin G, Oxacillin, Macrolides (e.g. Azithromycin, Erythromycin, Tylosin), Lincosamides (e.g. Lincomycin, Clindamycin), Streptogramins (e.g. Virginiamycin), Glycopeptides (e.g. Vancomycin), Bacitracin
- Klebsiella spp.: Ampicillin
- Proteus vulgaris: Ampicillin, Cephalosporins I (e.g. Cephalexin), Polymyxins, Doxycycline
- Proteus mirabilis: Tetracycline, Polymyxins, Doxycycline
- Serratia marcescens: Ampicillin, Amoxycillin-Clavulanate (Clavulox), Cephalosporins I, Polymyxins
- Enterobacter sp.: Ampicillin, Amoxycillin-Clavulanate, Cephalosporins I, Cefoxitin
- Pseudomonas aeruginosa: Ampicillin, Amoxycillin-Clavulanate, Cephalosporins I and II (including Cefovecin), Tetracycline (including Doxycycline), Chloramphenicol, Trimethoprim (SXT)
- Haemophilus spp.: Streptomycin, Kanamycin, Macrolides
- Campylobacter jejuni & coli: Cephalosporins I, Trimethoprim
- Most Gram-positive bacteria: Polymyxins, Quinolones/Fluroquinolones (e.g. Enrofloxacin, Ciprofloxacin, Difloxacin, Marbofloxacin)
- Streptococcus spp.: Aminoglycosides (low level)(e.g. Gentamycin, Neomycin, Farmycetin/Soframycin), Polymyxins
- Enterococcus spp.: Cephalosporins, Aminoglycosides (low level), Sulfonamides (in vivo), Trimethoprim (in vivo), Polymyxins, Clindamycin
- Listeria monocytogenes: Cephalosporins, Lincosamides
- Salmonella spp.: 1st and 2nd Generation Cephalosporins and Aminoglycosides (in vivo)
- Pasteurella spp.: Gentamycin
