Multidrug-resistant (MDR) bacteria continue to emerge globally and are present in both human and veterinary populations. They can freely move between the populations, and this is particularly significant to the veterinary professional. The clinical presence of an MDR bacterium is difficult to elucidate. Inappropriate and indiscriminate use of antibiotics can result in greater circulating MDR variants, and regular overuse of broad-spectrum antibiotics can contribute significantly. This has further significance due to the potential for zoonoses and interspecies transmission. Many bacteria are currently included in this category. The 2 most significant pathogens include methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant S intermedius/pseudointermedius (MRSI/MRSP). Both are resistant to beta-lactams. MRSA is a significant human pathogen, while MRSI/MRSP can cause staph infections in dogs and opportunistic infections in other animals. Other organisms with varying clinical significance include methicillin-resistant S schleiferi coagulans, methicillin-resistant coagulase-negative Staphylococcus, MDR Enterococcus, vancomycin-resistant Enterococcus, Acinetobacter species, Pseudomonas species, and extended-spectrum cephalosporinase- and beta-lactamase-producing bacteria. All are present in clinical, opportunistic, and nosocomial infections.

COMMENTARY: It is imperative that veterinarians act in the capacity of public health officers in light of the increasing number of circulating MDR pathogens. Veterinarians need to slow and stop the generation of novel MDR variants by exercising judicious antibiotic use and should diagnose current clinical MDR cases by applying appropriate diagnostic techniques and by refraining from administering broad-spectrum empirical therapy. The limited antibiotic choices available for wild-type MDR strains is deeply concerning. Veterinarians must also be aware of the presence of carriers without clinical signs and of MDR zoonotic potential and they must advise pet owners accordingly. We use many drugs in veterinary medicine on an off-label basis, and there is concern about the legal ability to continue this practice with ongoing MDR generation from the veterinary field.

VRE, MRSI, ESBL, MDR, and more: Navigating the emerging problem of multidrug resistant bacteria. Weese JS. NAVC PROC 2009, pp 675-678.