Lecture 10: Gastrointestinal infections - Cholera (Vibrio cholerae) Antibiotic Resistance

Vibrio

A genus of Gram-negative bacteria possessing a curved rod shape and polar flagellum

Vibro cholerae is transmitted through..

fecal matter in water

Vibrio cholerae animal hosts

There are no known animal host for Vibrio cholerae, but the bacteria can easily attach to chitin-containing shells of crabs, shrimp, and other shellfish to create biofilms

V. cholerae life cycle: reservoir to host and back

V. cholerae biofilm in aquatic reservoirs → oral ingestion → colonization of intestinal epithelium → multiplication → diarrhea → aquatic reservoir

Where is V.cholerae localized in the host?

Intestine

[Fill in blank] are important for Vibrio survival in the reservoir

Biofilms

Cholera

An acute, diarrheal illness caused by infection of the intestine with the bacterium Vibrio cholerae

Mortality of Cholera

5% of infected persons will have severe disease characterized by profuse watery diarrhea (rice water diarrhea) and vomiting

• Rapid loss of body fluids leads to dehydration and shock. Without treatment, death can occur within hours.

*Treatments for Cholera

• Most important: rehydration

• Antibiotic treatment

• There is a vaccine but not available in US

How do antibiotics fight cholera?

Antibiotics will shorten but not remove symptoms due to mechanism of toxin activation

*How are different subtypes of cholera defined?

By their O-antigen (component of outer membrane lipopolysaccharide)

*T/F: All Cholera strains are pathogenic to us.

F

• Only two strains are pathogenic: Vibrio cholerae O-group 1 or 139 (serotypes)

Classes and targets of antibiotics

• Differentiation by target:

  • Inhibition of protein translation

  • Inhibition of cell wall synthesis

  • Disruption of bacterial cell membranes

  • Inhibition of nucleic acid synthesis

  • Disruption of bacterial DNA

  • Inhibition of enzymes in DNA replication

• Differentiation by chemical structure

• Differentiation by spectrum of activity (Gram + vs -)

T/F: Antibiotics are antimicrobial compounds that are drugs against bacteria

T

*Antibiotic Resistance mechanisms (4 MS)

• Limiting access of antibiotics

• Enzymatic inactivation of antibiotics (cleaving/ digest)

• Modification or protection of antibiotic targets

• Failure to activate antibiotics

*Regulation of antibiotic resistant genes (4 MS)

• Repressors

• Translational attenuation

• Activators

• Insertion sequence and promoter mutations

Factors That Allow Antibiotic Resistance

• Resistance mechanisms

• Regulation of antibiotic resistant genes

• Emergence and the spread of antibiotic resistance genes

• Factors contributing to the widespread of antibiotic resistance

What limits access of antibiotics to the cell

• Outer membrane porins

• Reduced uptake across the cytoplasmic membrane

• Active efflux pumps