BACTERIAL IDENTIFICATION
TESTS
11.1 INTRODUCTION
In the previous chapter we have discussed various methods of isolation of
bacteria. The bacteria thus isolated needs to be further identified to genus and
species level. The identification is required so as to cure the illness or the
infe...
11.1 INTRODUCTION
In the previous chapter we have discussed various methods of isolation of
bacteria. The bacteria thus isolated needs to be further identified to genus and
species level. The identification is required so as to cure the illness or the
infection caused due to the bacteria by using appropriate antibiotics. Identification
also holds significance for epidemiological purposes.
OBJECTIVES
After reading this chapter, you will be able to :
z describe the processes involved in the identification of bacteria.
z explain the significance of microscopy in the process of identification of
bacteria.
z explain the significance of biochemical test in the process of identification
of bacteria.
z describe the significance of serology in the process of identification of
bacteria.
z describe the significance of phage typing in the process of identification of
bacteria.
z explain the significance of antimicrobial susceptibility testing in the process
of identification of bacteria
11.2 BACTERIAL IDENTIFICATION
The isolated bacteria are further processed through one or few of the procedures
mentioned below so as to identify the bacteria
z Staining of the isolated bacteria
z Motility testing
122 MICROBIOLOGY
, Bacterial Identification Tests MODULE
z Biochemical testing Microbiology
z Serological tests
z Phage typing
z Identification disc testing
z Semiautomated and Automated identification systems
z Molecular techniques
Notes
(i) Staining of the isolated bacteria
Staining of the bacteria forms the foremost and the most important step in the
identification of bacteria. The isolated bacteria are stained by various methods
depending upon the bacteria in focus. Various staining techniques are as follow
1. Gram staining: differentiates bacteria into two types
Gram positive and Gram negative bacteria
Gram positive bacteria can be either cocci or bacilli or vibrios. Gram
positive pathogenic bacteria are staphylococci, streptococci, pneumococci,
etc
Gram negative bacteria can be either cocci or bacilli. Gram negative
pathogenic bacteria commonly encountered are E.coli, Klebsiella, Salmonella
spp, shigella, etc
2. Albert staining: is performed in case if one suspects a Corynebacterium
spp.
3. Acid fast staining: is performed in cases suspected of Mycobacterial
infection. Eg. Tuberculosis, leprosy, etc.
4. Special staining is necessary in case of spirochetes and other organisms.
INTEXT QUESTIONS 11.1
1. ......................... of bacteria is the important step in identification of bacteria
2. Gram stain differentiates bacteria as ......................... & .........................
3. ......................... staining is used in Identification of Corynebacterium spp
4. ......................... staining is used in identification of Mycobacterial infection
5. ........................., ......................... & ......................... are examples of Gram
Positive Bacteria
6. ........................., ......................... & ......................... are examples of Gram
Negative Bacteria
MICROBIOLOGY 123
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