Bacterial diseases in reptiles (Proceedings)


Bacterial diseases in reptiles (Proceedings)

Apr 01, 2009

It has been well established that the majority of bacterial pathogens affecting reptile patients are of the gram negative type. However, proper isolation and evaluation of the resulting laboratory data can often times be somewhat confusing. The practice of treating all gram negative isolates is no longer acceptable as it is now realized that many reptiles harbor gram negatives as part of their normal flora, and are either commensals or opportunists.

The decision to treat or not to treat depends on many factors. The source of the isolate, the type of animal patient, its physical or clinical condition, the pharmaceuticals available, owner compliance, experience of the clinician, and of course, the isolate itself.

Proper sample collection for bacterial culture and sensitivity data is a critical step in initiating appropriate clinical care. It is often the practice to collect bacterial culture samples, and then while waiting for the results, start the patient on an empirically selected antibiotic. This practice is wise as it gives the clinician a head start in treatment while waiting for results. Improperly collected samples will offer little information towards tailoring antibiotic therapy.

A common practice is to collect a combo culture from the oral cavity and cloaca in a sick animal as a screening tool. While this may be easy, it does not always give very specific information regarding bacterial pathogens. The oral cavity contains a garbage can of bacteria from the environment. Although the actual pathogen might be included in the culture sample, it is often dwarfed by a myriad of other microorganisms. A similar problem is encountered when randomly culturing the cloacal region.

Site specific bacterial sampling is preferable to random sampling. Snakes presenting with infectious stomatitis, or mouth rot, will benefit from appropriate antimicrobial therapy based on proper bacterial isolation. However, as mentioned, a sample collected by swabbing a culturette over the affected gingiva will usually yield a mixed-bag of oral cavity and environmental flora. Some sort of gram negative isolate is almost always found, but its significance is nebulous at best. A better technique would be to prep the area with alcohol, make a small stab incision through the infected area with #11 scalpel blade, and then using a micro-culturette swab, sample the affected tissue from within the incision. An isolate here will have far greater clinical significance.

Cloacal cultures can be used in patients with diarrhea or other gastrointestinal disturbances. Proper diagnostics and rule-outs should be executed prior to the testing. Fecals for ova and parasites, including protozoal pathogens, is a must. Interpretation of the culture results can be confusing since many different bacterial are normally present. However, certain isolates should be cause for immediate concern. These will be discussed later in the manuscript.

Patients displaying respiratory signs should be cultured. Again, random culturing of the saliva or tracheal exudate within the mouth will be non-diagnostic. If time and cost restraints are imposed, a preferable sampling site would be high within the choanal slit. Since, anatomically, this is the area where the glottis opens, you are more likely to identify a real pathogen. An even better technique would be to perform a tracheal wash. An appropriately sized sterile, red-rubber catheter is inserted transglottally and directed into the lung region. Sterile saline (approximately one percent of the animal's body weight) is infused through the catheter. The patient is then gently inverted, rolled side to side, or in some way rocked to allow mixing and washing of the saline within the lung. After this, as much fluid as possible is withdrawn. It is not uncommon to only get back a small portion of the infused saline. Do not let this alarm you. Any remaining fluid will be readily absorbed through the lungs. Occasionally, in cases of severe pneumonia, quantities greater than the amount infused will be retrieved. The fluid collected can now be used for both cytology and bacterial culture and sensitivity testing.

Open abscesses should be debrided and the cultures taken from deep within the lesion. Closed abscesses can be sampled by aspirating material using sterile techniques. Cystic and vesicular fluid can cultured in a similar fashion.

Cultures can be taken from body fluids such as blood and urine using standard techniques. Properly collected samples, either via cystocentesis or direct venipuncture, yield invaluable diagnostic information.