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THE number of pet reptiles is steadily increasing in some European countries, as well as in the USA, (Mermin and others 1997, Editorial Team and others 2008) and green iguanas (Iguana iguana) are frequently being kept as pets. Green iguanas are native to regions extending from southern Mexico to central Brazil, Paraguay and Bolivia, but imported animals are often bred in captivity on farming operations. The first scientific studies on iguanids examined mostly physiological, biochemical, anatomical and behavioural aspects. However, the increasing popularity of reptiles as pets justifies the increased interest about the microbiological and zoonotic potential of these species. Reptile-associated salmonellosis is being recognised as an emerging zoonosis (Editorial Team and others 2008). Captive green iguanas can harbour multiple Salmonella serotypes in their intestinal tracts (Burnham and others 1998), some of which have been implicated in reptile-associated disease in human beings (Ackman and others 1995). This short communication describes a study carried out to determine the normal conjunctival aerobic bacterial flora of captive green iguanas undergoing a routine ophthalmic examination as part of a general health check.
Fifteen captive green iguanas (eight females and seven males) aged four to 10 years were included in the study. Both eyes in each animal underwent ophthalmic examination, including slit lamp biomicroscopy, ophthalmoscopy, a Schirmer tear test I and conjunctival microbiological tests. Before the examination, all the animals were kept in a similar environment, at the same temperature and humidity levels. The animals were restrained manually and the eyelids were opened gently with sterile blunt forceps to allow the positioning of a sterile Schirmer test strip in the ventral conjunctival fornix of each eye. Following the test, the end of the strip that had been located within the conjunctival sac was cut off and immediately inoculated into 10 ml brain heart infusion (BHI) broth (Becton-Dickinson). After incubation for 24 hours at 37°C in an atmosphere containing 5 per cent carbon dioxide, the BHI broth cultures were plated on to tryptose agar (Oxoid) containing 5 per cent bovine red blood cells and on to MacConkey's agar (Oxoid), and incubated for 24 to 48 hours at 37°C in aerobic and microaerophilic (5 per cent carbon dioxide) environments. Identification of bacterial isolates was based on their growth and colony characteristics, Gram staining, cellular morphology, catalase and oxidase reactions. Species identification was carried out using the API Staph and API 20 E biochemical test systems (bioMérieux), as well as conventional biochemical tests (Quinn and others 1994).
None of the green iguanas included showed evident abnormalities on the ocular inspection. Bacteria were isolated from the conjunctival sacs of all the animals. A wide range of bacterial species were cultured, as listed in Table 1. In 13 of the iguanas, more than one species was isolated, and only one of the 30 eyes tested was sterile. The most common isolates were Staphylococcus aureus, Escherichia coli and Bacillus species.
The survey showed the predominance of Gram-positive species in the normal conjunctival bacterial flora of green iguana, in accordance with data reported for other animal species (Moore and Nasisse 1998, Dubay and others 2000, Silvanose and others 2001, Pinard and others 2002). The bacterial isolates, in particular S aureus, Pseudomonas aeruginosa and E coli, were not involved in clinical disease. However, susceptibility to bacteria may be influenced by a number of factors, including physiological and psychological stresses, and a relationship between the resident normal flora and the aetiology of ocular infections in green iguanas cannot be excluded. Several ocular manifestations of bacterial infections have been reported in reptiles. Holt and others (1979) reported S aureus infection of the eye in one of four tortoises with panophthalmitis, but the disease was considered likely to be due to hypovitaminosis. E coli has been isolated from a lower eyelid abscess in a desert iguana (Millichamp and others 1983). However, skin abscesses are common in all reptiles and can be associated with a wide variety of microorganisms (Holt and others 1979). Aeromonas species were found to be associated with eye infection in laboratory lizards (Cooper and others 1980). Pasteurella species were involved in respiratory disease with ocular clinical signs in desert tortoises (Millichamp and others 1983). Uveitis with hypopyon or subspectacular infections have been described in various reptile species secondary to systemic infection due to Pseudomonas species, Klebsiella pneumoniae or Proteus species (Millichamp and others 1983). Previous reports therefore suggest that ocular manifestations of bacterial infections in reptiles are mostly due to Gram-negative organisms. However, little information is available regarding eye disease in green iguanas or the normal bacterial flora of the conjunctiva of other reptiles. Moreover, it should be considered that many diseases in captive reptiles are a consequence of incorrect husbandry procedures, and that although the eye may be a primary site of disease, it is frequently involved in systemic infections. Further research, comparing the present results with those from diseased animals, could provide evidence of a possible pathogenic role of the normal bacterial flora in the eyes of green iguanas.
Some of the conjunctival isolates have a potential zoonotic risk, in addition to the already known risk of faecal shedding of Salmonella in captive green iguanas (Mermin and others 1997, Burnham and others 1998, Mitchell and Shane 2000). In the present study, bacterial species isolated that are known or suspected human pathogens included Acinetobacter species (Bergogne-Bérézin and Towner 1996), Enterobacter species (Sanders and Sanders 1997), Enterococcus faecium (Sood and others 2008) and P aeruginosa (Hsueh and others 2002). Some of these species have been associated with infections in immunocompromised human patients (Bergogne-Bérézin and Towner 1996, Hsueh and others 2002, Sood and others 2008). Pantoea and Bacillus species infections are uncommon in human beings and are mostly linked to thorn and eye injuries, respectively (Van Rostenberghe and others 2006, Miller and others 2008).
To the authors' knowledge, this is the first report on the normal bacterial flora of the conjunctiva in green iguanas. As the animals in this study were clinically healthy, it is not possible to assign a specific pathogenic role to the bacteria isolated in terms of ocular diseases. However, given the potential role of many of the isolated species in causing disease in human beings, the zoonotic risk associated with keeping green iguanas as pets should not be considered limited only to salmonellosis, especially for immunocompromised people.
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