Aerobic bacterial flora of the nasal cavity in Gulf of California sea lion (Zalophus californianus) pups
Introduction
In general, the normal bacterial flora in a mammalian host can be considered as either resident or transitory, of which the resident population is constant for a given anatomical area at a specific age of the host animal. When resident microflora ecology becomes disturbed, the initial balance tends to be restored spontaneously. Transitory microflora however comprise microorganisms from the environment that remain for only short periods within the host. The animal’s body is not a uniform bacterial habitat as each organ system differs, creating a selective medium where certain microorganisms are more favoured than others (Sorum and Sunde, 2001, Mcfarland, 2000).
The development of the respiratory tract microflora begins at birth when the animals are exposed to a complex spectrum of microorganisms, of which those capable of adaptation or colonisation of certain mucosal areas predominate. Furthermore, the microflora of those animals that grow up in the same environment will be closely related and will be stable under specific conditions (Cangemi de Gutiérrez et al., 1999).
Bacteria, yeasts and fungi are part of the normal flora of marine mammals and a wide variety is known to be present in their environment, even though their clinical importance is often unknown (Dunn, 1990). The available information on bacterial infections in sea lions is limited and there are only a few reports of infectious diseases and isolates from animals in rehabilitation centres (Gilmartin et al., 1979, Dierauf et al., 1985, Dunn, 1990, Forshaw and Phelps, 1991, Gulland et al., 1996, Thornton et al., 1998). The aim of this work was to identify using standard biochemical tests the aerobic bacteria present in the nasal cavity of clinically healthy sea lion pups living in the wild.
Section snippets
Animals
A total of 57, clinically healthy sea lion pups (Zalophus californianus) aged 1–8 weeks, were examined in six lion reproductive rookeries in the Gulf of California (Fig. 1). Ten animals from each of the rookeries at Islote El Rasito, Isla Granito, Los Cantiles, Isla Angel de la Guarda, and Isla El Coloradito; nine animals from Islote El Partido and eight from Los Machos, also at Isla Angel de la Guarda, were captured and submitted for an evaluation of weight, size, temperature, shoulder,
Bacterial identification
All 114 samples were cultured in both media (blood agar and MacConkey agar). Of these, 47 presented bacterial colonies in blood agar plates and 24 on MacConkey agar plates. Fifteen different bacterial genera were identified, as well as 24 different bacterial species, seven of which were Gram positive and eight Gram negative. The results from the isolation of the aerobic microorganisms from the nasal cavity of sea lions are shown in Table 1.
One hundred bacterial isolates were obtained from both
Discussion
Bacterial infections play an important role in sea lion morbidity and mortality. Bacteria are frequently secondary invaders to other infectious processes or environmental factors. Immediately after birth, the different cavities of the body are colonised by a variety of microorganisms (Ridgway and Harrison, 1981, Howard et al., 1983). This normal flora can act competitively, excluding pathogens, inhibiting their colonisation and consequently, avoiding infections (Mcfarland, 2000). The normal
Acknowledgements
This study was supported by the Dirección Regional en Baja California del APFF, Islas del Golfo de California Monitoring Program (Comisión Nacional de Areas Naturales Protegidas), under the Dirección General de Vida Silvestre of the Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT), permit number DOO. 02-5482 and DOO. 02-1686. The authors would like to thank the Secretaría de Marina-Armada de México, especially the staff and personnel of the ship El Zarco C-81. Also, we wish to thank
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