Veterinary Clinical Biochemistry and Laboratory Diagnosis-II

INTRODUCTION

• The chief functions of clinical microbiology laboratory are to examine and culture specimens for microorganisms, to make accurate species identification of important isolates. Identification of bacterium consists of a comparison of unknown bacteria with the known bacteria. Identification of bacteria is based on phenotypic characteristics. All known characteristics are taken into consideration, but certain characteristics are selected and used for identification of bacteria.
• In practice Dichotomous key method is familiar to all microbiologists in identification bacteria. In this the characters are taken and the features are expressed unequivocally as either positive or negative. In 1968 Dybowski and Franklin suggested various theoretical models, using computers in the identification of bacteria. The preliminary identification of unknown bacteria includes
  • Direct microscopic examination of clinical specimens.
  • Colonial characteristics (size, surface,)odour produced and pigment production.
  • Staining reaction – To know either Gram+ve or Gram-ve bacteria and also to study the morphology, arrangement, size, shape of bacteria.
• However, the final characterization of an unknown bacterial isolate to identify it to the genus and species levels is usually accomplished based on
  • Testing certain enzyme systems, metabolic characteristics that are unique to each species and serve as identification markers using various biochemical tests.
  • Rapid method for identification of bacteria using are readily available from commercial source. eg. API system.
  • Molecular techniques based Bacterial Identification
• Accurate and definitive microorganism identification, including bacterial identification and pathogen detection, is essential
  • To know the causative agent and diagnosis of the disease
  • To choose the right antibiotic for therapy.
  • To trace-back of disease outbreaks associated with microbial infections.
  •  Bacterial identification is used in a wide variety of applications including microbial forensics, criminal investigations, bio-terrorism threats and environmental studies.