Abstract

Bacterial infections are an important cause of morbidity and mortality in marine mammals. The accurate identification of a suspected bacterial pathogen relies on culture followed by time-consuming and subjective phenotypic tests. In human medicine molecular diagnosis is playing an increasingly important role in the rapid detection and identification of pathogenic organisms in clinical samples. The genetic variation of ribosomal genes, which are universally present in bacteria, offers an alternative to culturing for the detection and identification of these organisms. The 16S ribosomal gene is an excellent candidate for molecular bacterial detection since it contains conserved sequence regions ideal for primer targeting as well as regions of variability useful for species identification. We have recently adapted a novel molecular biology technique to differentiate 16S rRNA gene sequences from different mycoplasma strains isolated from California sea lions (Zalophus californianus). This technique involves polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE) and automated DNA sequencing.

This technique has potential as a sensitive, rapid, and reliable alternative to routine culture-based methods for detecting and distinguishing a wide range of bacteria. Empirical antibiotic selection has become increasingly complicated and expensive, particularly since heavy use may contribute to the acquisition of resistance in some bacteria. It is important therefore to continue to improve our ability to accurately, cost-effectively, and rapidly diagnose infectious diseases in marine mammals in captivity or rehabilitation, so that specific, appropriate, and effective antimicrobial therapy can be initiated promptly.