Gram Negative Bacteria Flashcards
What are three kinds of lactose negative enterics?
salmonella, shigella, yersinia
What kind of stain is used for mycobacteria (acid-fast staining)?
carbol fuschin (Ziehl-Neilson)
Are mycobacteria anaerobic?
No, aerobic
Isoniazid, rifampin, pyrazinamide and ethambutol are used to treat ____________
TB
The cytotoxin involved in M. tuberculosis is ….
cord factor (serpentine growth)
Does M. tuberculosis release exo/endo toxins? What are the virulence factors for TB?
No endo/exotoxins, but a cytotoxin (cord factor)
wax D and PPD are virulence factors
Are antibodies important for tb? Where does the TB live?
No, there is no humoral immunity for TB, but cell/ cell-mediated immunity is present. T lymphocytes and cytokines protect against TB. TB lives inside of MACROPHAGES
What is the importance of a granuloma to TB infection? TNF?
Granuloma is aggregation of monocytes and macrophages, important for controlling tb infection in the lung, in tb there is no granuloma infection. So without granuloma the bacteria can spread from lungs to other parts of the body
Tnf- tumor necrosis factor alpha- important for inducing granuloma formation
Describe the pathogenesis of TB
TB enters macrophages, they aggregate and die, creating a caseous center n the tubercle surrounded by macrophages and lymphocytes –>dormant
In disease state, the tubercle ruptures after liquefication and the bacilli spill into the bronchiole and is released to the respiratory system
Why can the M. Tuberculosis be dormant?
Restriction in growth granuloma turns into caseum, low ph, low oxygen so bacteria in dormant phase because unfavorable conditions for growth of tb
In luciferin-luciferase reaction, positive light production means….
bacteria is resistant to antibiotics
Why is streptomycin limited in its action against TB?
It is only active against the etracellular bacilli, and there are strains of bacteria resistant to it
Med that inhibits RNA synthesis for TB
Rifampin
Anti-TB drug that penetrates extra/intracellular environments of lesions and deters selection of resistant mutants
Ethambutol
Bactericidal against organisms in acidic environment of phagosomes
Pyrazinamide
What group of atypical mycobacteria produce yellow-orange pigment in PRESENCE of light and includes M. kansasii and M. marinum? fish tank –>skin infections
Group 1
What group of atypical mycobacteria produce yellow-orange pigment in ABSENCE of light and includes M. scrofulaceum? (in soil and water, leads to removal of lymph nodes)
Group II
What group of atypical mycobacteria produce little or no pigment and includes M. avium-intracellulare, (causes pulmonary infection)
Group III
What is unique about growing M. leprae?
can’t grow on artificial medium and doesn’t grow well above 30 degrees C. It is an obligate intracellular parasite, so needs to be grown in armadillo or mouse
What is the main difference between tuberculoid and lepromatous leprosy?
Immune response is in place and robust for tuberculoid, while there is a low immune response in lepromatous)
Where are nocardia found, and how do they affect the body?
Found in the soil, are opportunistic pathogens causing pneumonia with abesses and necrosis
What bacteria is characterized by:
o Watery diarrhea, mostly in infants and developing countries
o Bundle forming pili attach bacteria to host sell, Type 3 secretion system injects effector proteins into host cell and releases factors for ‘intimate attachment’, making actin pedestals and damage of microvilli. This means there will be bad reabsorption, causing watery diarrhea
o Virulence factor- bundle forming pili, type 3 secretion
EPEC (enteropathogenic e. coli)
What bacteria is characterized by:
o Cause of traveler’s diarrhea, transmission via food and water contaminated with human waste/ direct contact
o ETEC colonize the small intestine, cause prolonged hypersecretion of Cl- ions and water by intestinal mucosal cells, while inhibiting the reabsorption of sodium. Gut becomes full of liquid, making watery diarrhea.
o Not common in US, therapy is fluid replacement, disease is self-limiting
o Toxins: heat stable (ST) causes elevation in cGMP, heat labile (LT) causes elevated cAMP
ETEC (enterotoxigenic e. coli)
What bacteria is characterized by:
o Found in USA, usually O157:H7, humans eat undercooked meat, fluids are not reabsorbed in intestinal tract
o Only need about 100 cells to cause an infection
o Bloody diarrhea/dysentery, no fever (afebrile), self-limiting, few leukocytes
o Associated with HUS=hemolytic uremic syndrome, which is acute renal failure in children 5-10
EHEC- enterohemorrhagic e. coli
What bacteria is characterized by:
o Resembles shigellosis
o Rare in US, need a lot of the bacteria for infection
o Invade and destroy colonic epithelium watery diarrhea, some dysentery, fever
EIEC enteroinvasive e. coli
What bacteria is characterized by:
o Associated with traveler’s diarrhea
o Bacteria stack on top of each other due to fimbriae (aggregative adherence fimbriae) mucous production biofilm formation
EAEC enteroaggressive e. coli
What bacteria is characterized by:o Common case of UTIs
o Pili produced that binds to uroepithelial cells, replicate and destroy the epithelia
o Frequent urination, pain during urination, bloody urine
UPEC- uropathogenice. coli
What is an AB-toxin?
- AB toxins are two-component protein complexes secreted by pathogenic bacteria. They are type III toxins (virulence facot that releases factors into exgtracellular fluid or host cells, similar to basal body but instead of releasing flagellin can release virulence factors).
- A= Active domain, B= binding domain
What is the importance of S-MAC?
• Type of agar, forments sorbitol, detects e.coli 0157 strains
What are the two major types of pathologies related to Salmonella infection?
- typhi (enteric fever, not seen often in US)
* typhimurium (gastroenteritis)
What are the basic phenotypic characteristics of the Salmonella?
- Gram negative bacilli, lactose negative
* motile, H2S gas production (some exceptions)
What gram negative, lactose negative, motile, H2S gas producting bacilli has the following pathology:
• human intestinal disease due to ingestion of bacteria (contaminated food/water)
o organism gets to small intestines where it enters M cells and then to basolateral surface
o macrophages often ingest bacteria
bacteria protected from host responses (e.g. complement, antibodies, etc)
• Salmonella alters host cells:
o changes actin to allow for “bacteria-mediated endocytosis”
o prevents lysosomal enzymes of macrophage from degrading bacteria
Salmonella tyi/S. paratyphi
What disease is characterized by:
• systemic disease caused by S. Typhi or S. Paratyphi, low infectious dose
• fever, nausea, rash, and other systemic symptoms
• disease from ingesting contaminated food
o humans only known hosts of these strains
o endemic in developing nations
o not common in U.S. (food/water/sewage care)
• after 10-14 days of initial infection, patients have gradually increasing fever, headache, myalgia, malaise
• at around 21 days after infection, GI symptoms present (not seen in all patients) – diarrhea
• see inflammatory reaction in Peyer’s patches/GALT (= necrosis)
Enteric (typhoid) fever
Describe the carrier state of S. typhi
• after recovery of most Salmonella infections, patient still has bacteria within stool
• some become a chronic carrier and produce bacteria for up to a year or more (lifetime)
o often asymptomatic
o women twice as often as men become carriers
o older individuals become carriers at a higher rate than younger people
What “species/strains” of Salmonella are most commonly associated with gastroenteritis?
typimurium
What phase of enteric infection does this describe: Self-limiting diseases (individual will recover on their own without treatment, if immune system is working properly and fights the infection)
Non-inflammatory phase:
nausea, vomiting, diarrhea
What phase of enteric infection does this describe?
bacteria in epithelial layer of GI
inflammatory, dysentery (bloody diarrhea)
What phase of enteric infection does this describe?
Infection goes into capillaries and other parts of the body like the intestinal tract
INvasive=enteric fever
What is the TSI assay?
o Determines 4 features with one inoculation (lactose, glucose, hydrogen sulfide production, gas production)
What is hecktoen agar?
Hecktoen agar- inhibits most gram+, sugars used to judge fermentation, can also distinguish H2S production
what medium/tests are used to isolate gram negative bacteria?
MacConkey or Eosin-Methylene blue agar
What are phenotypic traits of E. coli? (3)
o O antigens- somatic/ cell wall antigens found on LPS
o H antigens- associated with flagella
o K antigen- located in the capsule
Describe Enterobacteriaceae
- Gram negative, have LPS as virulence factor
- most are motile (peritrichous flagella)
- Most have a capsule
- Many have serum resistance (inhibit complement proteins)
- Associated with enteric infections, bacteremia (bacteria in blood that can spread elsewhere in the body), UTIs
In TSI test, yellow means? black means? air bubble means? This is used for gram ____ bacteria
Yellow = sugar fermentation
Black = H2S positive
Air bubble = gas production
gram negative bacteria
There is black on hecktoen agar. This indicates____ is produced and _____ is the bacteria
H2S, salmonella. Shigella is H2S negative
What does E. coli type III secretion do? What is this similar to?
What does type III do? Type III- Introduces toxins into host cell instead of being used for movement of bacteria
What is type III similar to? Basal body of flagella
The following describes what gram negative, lactose negative, H2S negative, non-motile bacillus?
• invasive into M cells and macrophages of Peyer’s patch
o allows for replication of the bacteria and production of virulence proteins
• virulence proteins cause “ruffling” of epithelial cells
o allows for endocytosis of the bacteria
o actin rearrangement allows for cell-to-cell spread
• S. dysenteriae produces shiga toxin (similar to EHEC)
o destruction of intestinal epithelium (and spread of the bacteria)
Shigella
The following describes what group of bacteria?
Gram-negative intracellular diplococcus
coffee-bean shaped or kidney-bean shaped (one end flattened)
infects mucus-secreting epithelial cells
Oxidase positive
evades host response through alteration of surface structures
Neisseria
