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.
Diagnosis
Isolation of bacteria from blood (1st week)
Stool and urine (2nd-3rd week
Infective dose of
10^6 organisms
what causes enteric fever
- Human carriers are the only known reservoir. Sources are contaminated drinking water, shellfish, milk and milk products
How to reduce the risks of enteric fever
- Clean handling of food, water treatment and safe sewage disposal are essential
- Vaccine available, but only effective against small bacterial load
Gram negative bacteria
Cause acute diarrhea with mucus, pus and blood
* Generally non-lactose fermenters
most commonly seen in Europe and North America (70-80%)
Shigellae
s.dysentriae
found mainly at the tropics causes severe illness
-invasion of the epithelial mucosa of the colon results in watery diarrhoea, cramps and fever
-Infection follows ingestion of small numbers of the organism
epidemiology of shigella. Preventions. Is there a vaccine?
Most commonly seen in children; poor sanitation and
crowding
* Prevention by safe handling of food, treatment of water, safe
disposal of sewage
* NO VACCINE
Gram-negative bacilli, lactose fermenters; most numerous aerobic species of the normal human intestinal flora
ESCHERICHIA COLI
What is the most frequent cause of a UTI
E.coli 85%
3 major surface antigens. How many?q
173 O 56H 103K
enteropathogenic E. coli (EPEC)
- first pathotype to be described
- can cause severe diarrhea in infants, especially in developing countries
- enterotoxigenic E. coli (ETEC)
major cause of infantile diarrhea in developing countries
- most frequent agent responsible for “travelers’ diarrhea
- enteroinvasive E. coli (EIEC)
- bloody diarrhea and dysentery similar to Shigella species
diffuse-adhering E. coli (DAEC)
associated with diarrhea primarily in young children (i.e., from 1-5 years)
enteroaggregative E. coli (EAEEC)
recognized as human pathogens in 1982 in hemorrhagic colitis outbreak
- E. coli O157:H7 most common cause of EHEC-associated disease
Haemorrhagic colitis
* Hamburger disease
* Proper handling of food, safe preparation and
proper cooking practices are essential to prevent
illness
- verotoxins or Shiga toxins (since similar to Shiga toxin from Shigella dysenteriae type 1) associated
to a sever and sometimes fatal condition, known as hemolytic uremic syndrome (HUS)
enterohemorrhagic E. coli (EHEC)
CRONOBACTER SPP
may colonize and infect hospitalized patients
- causes wound infections, bacteremia and hospital-acquired pneumonia
- may be naturally resistant to antibiotics
- Cronobacter sakazakii linked to outbreaks of contaminated powdered infant formula
-comma shaped
-gram negative bacilli
-produce enterotoxin which binds to epithelial cells of small intestine
secrete chlorides to decrease sodium absorption
-water accumulates causing diarrhea
-common in south Asia and Africa
-waterborne
Vibrio cholerae
Campylobacter jejuni/coli
- normal in birds and domestic animals
-some invasive, some toxigenic
-cause fever, abdominal pain, bloody stools
-stool culture on special media (no oxygem losrs of CO2)
What are psudomonas
free living Gram negative rods potential to cause illness in compromised patients
-live in water or moist place
-common from humidifiers, and equipment containing water or other fluids capable of supporting growth
psudeomanas areuginose
most common of pseudomonas
- respiratory pathogen in cysitic fibrosis patients
-infect skin burns
psuedomas cepacia
-multiplies in low nutrient environment
-contaminate saline and water
-respiratory pathogen for cycstic fibrosis
Are Pseudomonas easy to treat
no. diffciult b/c resistant to common antibiotics and may acquire resistance to affitonal antibiotics
What is haemophilus inflenzae
-found in nasopharyngeal flora, including children
-pathogen in 2 situations
1.invasive infection including meningitis, pneuomnia, joint infection, in children >5 (vaccine yasss)
2. Haemophilus influenzae infection in chronic bronchitisis and commonly isolated from sputum from these patients
LEGIONELLA
grows in water and is commonly found in shower heads and water tanks.
-oppurtunistic
-Cell mediated immunity may cause serious form of pneumonia
-exposure by aersol ppl 2 ppl NOT REAL
-cause legionellollis (mock pnuemonia)
Helicobacter pylori
Microaerophillic, spiral bacilli
* Most common cause of stomach ulcers
* In the past, cause was thought to be stress and diet
* 1982-Dr.Robin Warren and Dr. Barry Marshall discovered
link between H. pylori and ulcers
* Medical community slow to accept their theory (1994-
National Institute of Health Conference concludes strong
association between ulcers and H. pylori)
* Urease: protection form low pH
* Triple therapy treatment: antibiotics and H+ pump inhibitors
*Whooping cough VIOLENT COUGH
* 4 Virulence Factors
* Pertussis toxin (A-B)
* Extra cytoplasmic adenylate cyclase (weakens host defense)
* Filamentous hemagglutinin (bronchial attachment and exotoxoin
release)
* Tracheal cytotoxin (destroys ciliated cells poor clearance of
mucous and bacteria)
* Prevention: vaccination with heat-killed organism
Bordetella pertussis
