5.2 Flashcards
Gram-negative bacilli part of the normal flora found______. What disease do they cause? How are the divided by?
in the intestine
They also cause gastrointestinal disease.
These organisms are divided into groups based on their biochemical and antigenic properties
What are the 4 major groups of enterics
Enterobacteriaceae (Salmonellae,
Shigellae, E. coli ), Vibrionaceae (Vibrio, Campylobacter)
Pseudomonadaceae (Pseudomonas), Bacterioidaceae
What are the biochemical classification of enterics
- Ability to ferment lactose
*EMB Media:
* Lactose fermenters are dark purple/black
* Inhibits Gram positive bacteria- MacConkey Media:
* Lactose fermenters are pink-purple
* Inhibits Gram positive bacteria
- MacConkey Media:
What are other ways to test for biochemical classification
H2S production
Hydrolysis of urea
Liquefy gelatin
Decarboxylation of amino acids
What are the major surfaces of antigens
O-antigen– most external component of LPS
K- antigen- capsule that covers O antigen
H -antigen- is part of the subunits of the bacterial flagella (only motile bacteria have a H antigen)
3 Types OF DISEASES CAUSED BY GRAM-NEGATIVE BACTERIA
- Diarrhea – with or without systemic invasion
- Diarrhea with invasion of intestinal epithelial cells
- Diarrhea with invasion of lymph nodes and bloodstream
Diarrhea – with or without systemic invasion
a. No cell invasion – bacteria bind intestinal epithelial cells but do not enter the cell
b. Diarrhea caused by release of EXOTOXINS (enterotoxins in the GI tract)
c. ENTERTOXINS cause electrolyte and fluid loss
d. Watery diarrhea (no fever) – example includes Vibrio cholera
Diarrhea with invasion of intestinal epithelial cells
e. Virulence factors allow binding and invasion of cell
f. Toxins released destroy the cells resulting in bloody stool
g. Fever response
e.g Shigella
Diarrhea with invasion of lymph nodes and bloodstream
j. Abdominal pain and diarrhea containing white and red cells
k. Fever, headache and increased white cell counts
l. Examples include Salmonella enterica serovar Typhi, Yersinia enterocolitica,Campylobacter jejuni
Other Enteric Infections
Urinary tract infects, pneumonia, bacteremia and sepsis
The enterics are normal intestinal inhabitants. In hospital settings, nosocomial infections can
arise. Examples include E. coli, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter, Serratia,
and Pseudomonas aeruginosa
gram negative bacteria
opportunistic pathogen, often infects burn patients and can disseminate through body into CNS
Pseudomonas aeruginosa
general properties of salmonella
Member of Enterobacteriaceae family
Unable to ferment lactose
All have animal reservoirs EXCEPT S. enterica
serovar Typhi (humans are only host!!)
Types of infections in humans: enterocolitis, enteric
fever, opportunistic infections, septicemia and
osteomyelitis
What are the two species of salmonella?
S.enterica and S. bongori
What is Salmonella infections of man.
- Enterocolitis (caused by many serotypes of S. enterica)
- Enteric fever (known as typhoid and paratyphoid) caused by S. enterica serovar Typhi and S. enterica serovar Paratyphi
pathogenesis of Enterocolitis (Gastroenteritis)
Severity of infection and disease influenced by:
- dose of ingested organisms (a minimum of 105
is usually required for symptomatic infection) - state of host; highest incidence in young (<5 years), elderly, and in individuals with predisposing conditions such as malnutrition, impaired immunity, underlying infection
- virulence of infecting strain
what is the incubation period for Enterocolitis
6-48 h; usually 8-12 h ; multiplication in the mucosa of small intestine and colon, leading to inflammation with mononuclear response.
Clinical symptoms of enterocolitis
- nausea, vomiting, profuse diarrhoea, abdominal pain
- fever (38-39oC), chills, headache, myalgia
- recovery within 2-3 days
- septicemia, rare complication in susceptible hosts
How is enterocolitis diagnosed
stool culture
What causes the spread of enterocolitis
infection by ingestion of food or drink contaminated by poor handling practices
- animal products (poultry, eggs, meat, milk) and animals are major sources
- person to person spread may occur (e.g., in nurseries)
- most cases occur at home; institutional cases (e.g., nursing homes, schools rank second
- many cases undiagnosed and unreported
What is the treatment of Enterocolitis
Antimicrobials are not recommended in uncomplicated Salmonella enterocolitis. Antibiotic treatment
may prolong excretion of organisms in the stool and does not shorten the illness.
Enteric fever
Enteric fever is a severe generalized infection whose principal feature is multiplication in the lymphoid tissue.
What is the morality rate if enteric fever goes untreated
10% mortality
how long would a convalescent carrier of enteric fever last beign a carrier
3 months worth of shitting bacteria
How long are chronic carriers carriers
(1-2% of cases) lasting over 6 months and occasionally lifelong.
