VLD 421: Veterinary Clinical Biochemistry and Laboratory Diagnosis-II (0+1)

RAPID METHOD FOR IDENTIFICATION OF BACTERIA

• Rapid multi test micro methods have firmly established in diagnostic microbiology. The pioneering work of Buissiere and Nardon on single substrate multi test methods evolved development of several method for bacterial identification.
  • The Analytical Profile Index (API) developed shelf kits with dehydrated substrates in plastic wells
  • The other micro test identification system was in 96 well microplates containing different substrate.
  • Absorbent paper disc impregnated with substrate.
• The majority of micro methods were developed for the Enterobacteriaceae, but more recently special methods have been introduced for non fermentous, anaerobes, Streptococus, and Staphylococci.
• The micro ID systems depends on the presence of performed constitutive enzymes in the bacterial suspensions and give a result in 4 hours. The API have a wide range of tests for many groups of medical bacteria. The API 20E was designed for identifying Enterobacteriaceae and consists of 20 special compartments containing combination of several dehydrated substrates in a plastic strip. It is inoculated with suspension of the test organisms and incubated. After incubation for 18-24 hrs and the addition of appropriate reagents, it provides a set of results or profile which can be compared with  profile index or referred to manufacturer for computer assisted identification. The API 50 test kits are for the identification of Bacillus sp. AP1 20NE for staphylococci and AP1 20 STREP for streptococci.

Monoclonal antibodies

• Monoclonal antibodies produced against bacterial antigens from single cloned hybridoma B cells, has considerable potential for bacterial identification, even at the bedside of patient or in surgery e.g., commercial kits to detect group A Streptococci in throat swab.

DNA probes

• The single strand DNA is attracted to complementary strand to form double strand hybrids. Single strand radiolabelled bacterial DNA can thus be used to seek out complementary DNA strand in materials such as culture preparations and even clinical specimens directly. The procedure is usually carried out on a solid phase such as nitrocellulose filter. This technique can be used for rapid screening of large number of samples effectively and economically