Abstract

Although bats are popular exhibit animals at zoologic institutions, little is known about alimentary tract microflora of these animals. Few studies characterizing bat rectal microbial flora have been performed and oral cavity microflora has not previously been investigated.^1,6,7,9,10 Hence, antimicrobial therapy of bat bites to handlers or other bats is usually empiric and determination of disease status of the alimentary tract may be difficult.

Eight (five male, three female) apparently healthy great Indian fruit bats (Pteropus giganteus) were manually captured and restrained for induction and maintenance of anesthesia with isoflurane in oxygen administered via face mask. After physical examination, bats were sampled to identify oral and rectal microbes. Oral samples were obtained by swabbing the buccal and lingual gingiva, tongue, and hard palate. These samples were cultured for aerobic and anaerobic bacteria and fungi. Rectal samples were collected by insertion of the Culturette into the rectum and were cultured for aerobic bacteria. The diet was also sampled by inserting a Culturette into the diet prior to its removal from the bats’ enclosure on three consecutive days. The diet was composed of oranges, grapes, apples, raisins, spinach, bananas, and monkey chow. Diet samples were cultured for aerobic bacteria and fungi. All samples were transported at ambient temperature to the Louisiana Veterinary Medical Diagnostic Lab.

Aerobic, anaerobic, and fungal isolates were cultured using standard culture techniques and observed for colony and Gram stain or lactophenol blue mount morphology for identification to the generic level. Catalase testing, hemolysis, and lactose fermentation were used to determine whether API staph, API strep, API 20E, or API 20NE biochemical tests (API Analytab Products, Biomerieux, Hazelwood, MO) were used for further characterization of aerobic microbial isolates. Yeast was characterized with API 20CAUX biochemical test kit (Yeast Strip, Biomerieux, Hazelwood, MO).

The eight P. giganteus tested had a mixed oral microbial flora, which was predominantly gram-positive with anaerobic and fungal components. Aerobic oral and rectal microbial isolates found in more than one bat are listed in Table 1. Common anaerobic oral isolates were Fusobacterium spp. (n=4) and Peptostreptococcus spp. (n=5). Common fungal isolates of the oral cavity were Cladosporium spp. (n=5), Candida albicans (n=4), and Trichosporon spp. (n=2). Many of the organisms isolated from the oral cavity of P. giganteus have also been identified in bite wounds inflicted by dogs and cats.^2,4 Wound infections from animal bites are often polymicrobial and P. giganteus appears to be no exception. All bats sampled had greater than one aerobe, at least one anaerobe, and most had fungal isolates in their oral cavity. Aeromonas spp., Citrobacter freundii, and Clostridium spp. were identified as potential pathogens not previously reported in bite wounds.^3,5,8

Table 1. Common oral and rectal aerobic bacterial isolates of the giant Indian fruit bat (Pteropus giganteus) n=8

^aMost oral isolates are gram-positive.

Rectal aerobic isolates from the eight P. giganteus tested were predominantly gram-negative bacteria (Table 1), similar to those previously reported for Pteropodidae.^6,9 The aerobic bacteria most commonly isolated from the diet was Pantoea spp., and the most common dietary fungal isolate was Candida parapsilosis, with each isolate found on two separate days of dietary sampling. Salmonella spp. were not isolated from oral, rectal, or dietary samples. Dietary isolates and oral flora were dissimilar, having only gram-positive streptococcal and staphylococcal organisms in common. However, most bacteria isolated from the diet were also found in the rectal flora.

For empiric bacterial treatment of P. giganteus bite wounds, the clinician should consider therapy targeted toward gram-positive microbes and anaerobic bacteria while culture and susceptibility results are pending. In wounds unresponsive to appropriate antibacterial therapy, fungal culture and antifungal therapy should be considered. Rectal bacterial isolates should be interpreted carefully as they may be influenced by diet.

Acknowledgments

The authors thank the American Zoo and Aquarium Association Bat Taxon Advisory Group Small Grants Program and the Greater Baton Rouge Zoo for their support of this research.

Literature Cited

1.  Cassel-Beraud AM, Richard C. Etude de la flore intestinale aerobie de microcheiropteres Chaerophon pumila a Madagascar [The aerobic intestinal flora of the microchiropteran bat Chaerephon pumila in Madagascar]. Bull Soc Path Exot Filiales. 1988;81:806–810.

2.  Davidson EB. Managing bite wounds in dogs and cats. Comp Cont Ed. 1998;20:811–820.

3.  Flandry F, Lisecki EJ, Domingue GJ, Nichols RL, Greer DL, Haddad RJ. Initial antibiotic therapy for alligator bites: characterization of the oral flora of Alligator mississippiensis. South Med J. 1989;82:262–266.

4.  Goldstein EJ. Bite wounds and infection. Clin Infect Dis. 1992;14:633–638.

5.  Goldstein EJ, Citron DM, Finegold SM. Role of anaerobic bacteria in bite-wound infections. Rev Infect Dis. 1984;6:S177–S183.

6.  Heard DJ, DeYoung JL, Goodyear B, Greiner EA. Comparative rectal bacterial flora of four species of flying fox (Pteropus sp.). J Zoo Wildl Med. 1997;28:471–475.

7.  Moreno G, Lopes CAM, Seabra E, Pavan C, Correa EA. Aspectos bacteriologicos da flora intestinal Desmodus rotundus [Bacterial characterization of the intestinal flora of vampire bats]. Arq Inst Biol. 1975;42:229–232.

8.  Murphey DK, Septimus EJ, Waagner DC. Catfish-related injury and infection: report of two cases and review of the literature. Clin Infec. Dis. 1992;14:689–693.

9.  Pinus M, Muller HE. Enterobakterien bei Fledertieren (Chiroptera)[Intestinal bacteria of bats (Chiroptera)]. Zentralbl Bakteriol A. 1980;247:315–322.

10.  Simpson V. Normal bat flora (letter). Vet Rec. 1994;135:487–488.