Antibiotic Toxicity In Guinea Pig

The intestinal flora of the guinea pig, unlike that of most other animals, is predominantly gram-positive, and coliform organisms are not usually present in significant numbers.

• Narrow-spectrum antibiotics with antibacterial activity against gram-positive bacteria should be avoided, the cause of death is a decreased gram-positive bacterial flora and increased gram-negative flora, with related bacteremia/septicaemia.

• Antibiotics reported to cause enterotoxemia are penicillin, ampicillin, amoxicillin, bacitracin, erythromycin, spiramycin, streptomycin, tetracycline, oxytetracycline, lincomycin, clindamycin, vancomycin, cephalexin, cephalosporins.

• Some medications should never be prescribed; some can be injection but never orally. Topical antibiotics have also cause fatal enterotoxemia. If there are better alternatives, do not risk use of an injected antibiotic but use a safer one

• DeSomer et al. (1955) first clearly postulated that the lethality of penicillin for guinea pig was due to suppression of the normal gram-positive intestinal flora, overgrowth of coliform bacteria, and overwhelming toxaemia caused by absorption of bacteria toxin from the intestine.

• The fatal effect of small doses of penicillin in guinea pigs has been studied by many investigators. Within 12 hours after the parenteral injection of penicillin a 100-fold decrease in the total number of cultivable organisms in the cecum (predominantly anaerobic gram-positive cocci) occurred. Between 24 and 48 hours after penicillin an explosive proliferation of gram-negative coliform organisms occurred in the cecum, and the number of these organisms rapidly rose from insignificant levels. In some animals even larger numbers of gram-negative anaerobic bacteria (bacteroides) were found. Associated with overgrowth of gram-negative organisms was severe inflammation of the cecum and a somewhat less severe ileitis. Acute inflammation and bacteria were present in the regional lymph nodes. Bacteremia occurred in a high percentage of animal that become clinically ill. Thus the shift in intestinal flora was followed by an infection of the intestinal wall which ultimately extended beyond this organ and caused the death of the animal. The mortality following 50,000-unit dose of penicillin had remained in the range of 70-75 per cent. Approximately 25 per cent of animal given 50,000 units of penicillin survived (Farrar and Kent., 1965).

• Erythromycin, spiramycin, and bacitracin are all effective chiefly against gram-positive bacteria, and all kill guinea pig in relatively small doses.

• Streptomycin, a potent agent against both gram-positive and gram-negative organisms, has produced varying result. 

• Oxytetracyclin (tetracyclin) is a bacteriostatic antibiotic that inhibits the growth of many gram-positive and gram negative bacteria. Oral tetracyclin may cause GI disturbances and death in guinea pigs.

• Chloramphenicol, neomycin and polymyxin B, which are highly active against gram-negative bacteria, do not appear to be lethal for guinea pig, and neomycin and polymyxin B provided protection against the effect of penicillin.

• Trimethoprim-sulfamethoxazole, chloramphenicol, and enrofloxacin are safe to use in guinea pigs.

Sign for antibiotic toxicity: acute diarrhea, collapse, death

Diagnosis: history of being given antibiotic such as penicillin, ampicillin, amoxicillin, bacitracin, erythromycin, spiramycin, streptomycin, tetracycline, oxytetracycline, lincomycin, clindamycin, vancomycin, cephalexin, cephalosporins.

Treatment for antibiotic toxicity is primarily supportive. The antibiotic should be stopped immediately. Fluid therapy (IV) and metronidazole (or antibiotics that will be active against gram-negative organism) should be administered. Analgesics should be provided to prevent abdominal discomfort. High fiber diet should be syringe fed to prevent ileus.

Prognosis: poor

References:

DeSomer, P., Van De Voorde, H., Eyssen, H., and Van Dijck, P., 1955. A study on penicillin toxicity in guinea pigs. Antibiot. Chemother. (Wash.) 5:463-469.

Farrar, W.E., and Kent, T., 1965. Eneteritis and coliform bacteremia in guine pigs given penicillin. 47(4):629-642.   

Tennat, B., 2002. BSAVA Small Animal Formulary 4^th edition. Fusion Design, Wareham, Dorset, UK.

Thomas M. Donnelly, BVSc, DVP, DACLAM, DABVP(ECM), 2018. Guinea pigs. https://www.merckvetmanual.com/exotic-and-laboratory-animals/rodents/guinea-pigs

Ramsey, I., 2008. BSAVA Small Animal Formulary 6^th edition. HSW Print, Rhondda, Wales.