Chapter 20, Problem 2SA

Summary Introduction

To determine:

The differences between the pathogenicity of coliform, noncoliform, and truly pathogenic enteric bacteria.

Introduction:

The pathogenicity in Enterobacteria is affected by various factors like: Exotoxins, which leads to symptoms like diarrhea. Fimbriae and adhesion, which help the bacteria to adhere to host cells. A polysaccharide capsule prevents the cell from phagocytosis and antibodies. Iron binding compounds. Type III secretion system, synthesizes polypeptides. Lipooligosaccharides in the outermost membrane of the cell wall, which consists of Lipid A that causes symptoms like fever and dilation of blood vessels. Hemolysin breaks down red blood cells in the host.

Pathogenic members of the family Enterobacteriaceae are categorized into three groups:

Coliforms: These are pathogens which are opportunistic and can ferment lactose at a very fast rate. They are found in the usual microbial habitat. For example: E. coli, Klebsiella, and Citrobacter.

Noncoliforms: These too are pathogens which are quite opportunistic and do not ferment lactose. They are also found in the usual microbial habitat. For example: Proteus, Morganella, and Providencia.

True pathogens: These bacteria do not ferment lactose and don’t live in the usual habitat of microbes. They have many virulent factors which make them always pathogenic. For example: Salmonella, Shigella, and Yesinia.