4.3 Flashcards
2 oxidase positive fermentiert
vibrio
aeromonas
brio cholerae ecology
aquatic bacterium found widely in fresh, brackish or salt water
it can persist for long period in bodies of water, this persistence being aided by its ability to live in biofilms, mussels, aquatic crustaceans, amoeba and plankton.
climate and water temperature influence the multiplication of these hosts and thus the levels of V cholerae in water, explaining seasonal epidemics of human disease
cholera is aquired from
consuming contaminated water, seafood or other contaminated food
the organism finds it way back to the water sources in human diarrhoeic stool
vibrio cholerae serotypes
- can be typed into >200 serotypes based on antigenic differences in the O polysaccharide side can of the outer membrane lpopolysaccharide molecule
phenotypic typing of bacteria
- detecting characteristic expressed by the microorganism - shape, size, biochemical properties, antigenic properties
example of phenotypic techniques
- biotyping - based on metabolic activities including biochemical reactions, haemolysis and haemagluttination
- serotyping - based on antigenic variations in surface structures such as lipopolysaccharides, membrane proteins, capsular polysaccharides, flagella and fimbriae
- antimicrobial susceptibility typing (antibiogram) - based on differences in susceptibilities to a range of antibiotics
genotypic techniques
those that involve direct DNA-bassed analysis of chromosomal or extrachromosomal genetic elements
vibrio cholerae disease
cholera is a severe diarrhoea illness which may produce death within a few hours in a host who is weakened
the cause of death is dehydration leading to hypovolaemic shock, resulting from massive loss of water from the bowel
vibrio cholerae
virulence factor - cholera toxin
consists of subunits - bind the toxin to the enterocytes of the small intestinal mucosa and the A subunit enters the enterocyte cytoplasm
it interferes with the function of the transmembrane pump, resulting in increased chloride secretion and decreased sodium absorption, causing massive fluid and electrolyte loss into the intestinal lumen
vibrio cholerae pandemics
serotype 01 has historically been the cause of pandemics (biotype)
most recent epidemic caused by the El Tor biotype
vibrio species other than V cholerae
V alginolyticuss
V parahaemolyticus
V vulnificus
V vulnificus
skin and soft tissue infections related to marine recreational or occupational activities
may be severe in people with liver disease, alcoholism, diabetes or other chronic illnesses
septicaemia from contaminated seafood, with high fatality in individuals with chronic underlying medical conditions as listed above
the septicaemia illness may progress to involve the skin with a typically bulls cellulitis
mortality 30-40%
V alnginolyticus
causes wound infections and otitis media associated with water exposure
rarely may progress to necrotising fascitis and life threatening infection in the immunocompromised
V parahaemolyticus
a common contaminant of seafood eg. oysters and a cause of gastroenteritis
also causes skin and soft tissue infections related to marine activities
may be severe in people with liver disease, alcoholism or diabetes
genus aeromonas
found in freshwater and marine environments
several species cause skin and soft tissue infections following wounds received in aquatic environments
typically cellulitis but may progress to a necrotising infection similar to gas gangrene
aeromonas is also an uncommon cause of gastroenteritis
