microbiology 1 Flashcards
enterococcal endocarditis is seen after
GIT or GUT instrumentation or catherisation
What are the characteristics of enterococci
Bowel bacteria— hence can grow in hypertonic saline and bile.
Gram positive cocci
Strepto grp– hence if catalase negative.
Simple bacteria causing no hemolysis– gamma hemolysis.
PYR test positive — red colour
difference between enterococci and S bovis/ gallolyticus
Both are non hemolytic / gamma hemolysis
and both grow in bile
But PYR positive and growth in hypertonic saline is shown only by enterococci
Gallolyticus – does not grow in hypertonic saline and is PYR negative – does not show red colour.
what is the principle of PYR test
detects enz pyroli-donyl arylamidase produced by bacteria.
Product Beta naphthalamine give red colour on reacting with reagent in test.
uses of PYR tests
- distinguishes between enterococci from Strepto galloyticus
- Distinguishes E coli from other indole positive, lactose positive gram negative bacteria
- Distinguishes GABHS (S pyogenes) from GB-BHS (S galactae)
Importance of enterococci
30 % nosocomial endocarditis is from enterococci.
colonoscopy, cystoscopy, vaginal instrumentation, obstretics, pelvic surgery all are predisposing factors.
Most common cause of UTI
Local perineal and abdominal wound infection.
Problem with enterococcal infection
resistant to most antibiotics, difficult to treat.
Cell wall agent like ampicillin +Aminoglycosides are together given.
Largely resistant to these two medications also.
Vancomycin and linezolid resistance is also seen.
dental extraction endocarditis points to remember are
occurs in abnormal heart valves.
caused by VGS— viridans group streptococci
what is bile solubility tests
To differentiate streptococcus pneumoniae from alpha hemolytic streptococci
when bacteria is placed in a solution of bile salts, surface tension is reduced, autolytic enz within the bacteria is released and undergoes autolysis.
That is within few days broth gets cleared. ie bacteria is soluble (dies) in bile salts.
characteristics of VGS viridans (tooth decays)
ie Str. Mutans
Str. Sanguinis
mouth commensal– no growth in bile or hypertonic saline.
bile insoluble. Does not undergo cell lysis
ability to utilise sucrose and produce dextran (insoluble extracellular sugar polysaccharide)
which bacteria can produce dextran from sucrose
VGS viridans
How does VGS viridans cause tooth decay and nosocomial endocarditis after dental extraction
VGS can produce extracellular insoluble sugar – dextran from sucrose which helps in adherence.
ADHERE to TOOTH ENAMEL
ADHERE to FIBRIN-PLATELET aggregates on damaged heart.
pseudomembranous pharyngitis and cervical lymphadenopathy, myocarditis, heart failure and neurotoxicity is seen in
Diphtheria.
Pathogenesis of diphtheria
DT toxin – irreversibly inhibits ADP ribosylation of Elogation factor 2 (EF 2)– inhibits host protein synthesis.
treatment of diphtheria
1– Antitoxin– ie preformed neutralising antibodies that inactivate toxin DT.
Because it cannot inhibit the toxin that has already entered cell. It should be administered ASAP.
2nd line –antibiotics Beta lactam/aminoglycoside (b lactam/ erythromycin)
Organism for epiglottitis
H influenza esp in unvaccinated ppl
Drooling of saliva, stridor, tripod position to feel better.
Interferon gamma is critical in immunity against —- and —
viruses and intracellular bacteria
Interferon gamma functions 3 things
- Activates macrophages
- Increases MHC expression by macophages
- Activates TH1 helper T cells.
What is IGRA test
Interferon Gamma release Assay… detects latent TB.
Measures Cell M Immunity. Ie response of T cell to release Interferon Gamma when cultured with mycobacterial antigens.
cause of severe sepsis in asplenic pts
because 50 percent of bodys total antibody response comes from splenic B cells.
These splenic opsonising antibodies are particular important for encapsulated organism. Because capsulated organisms resists phagocytosis by neutophils and bacteria. They need opsonisation to be killed
Asplenic pts needs vaccination against
NHS ::
Neisseria meningitis
Hemophilus influenza
Strepto Pneumoniae
endocarditis on Right heart
IV drug —staph aureus
Immunity against giardiasis is from
secretory Ig A and helper T cells.
IgA binds to its infective form trophozoites not allowing it to bind to mucosa
what conditions predisposes to chronic giardiasis
Selective IgA deficiency
X linked Agammaglobulinema
CVID combined variable immunodeficiency.
Which intestinal pathogens are intracellular
Cryptosporidium parvum
Toxoplasma gondii
Ceftriaxone/ cephalosporins bind to penicillin binding protein name ____ to cause cell wall instability.
Transpeptidase.
It is a normal enz of streptococci which functions to cross (trans) link peptidoglycans in cell wall.
porin mutations are implicated in
antibiotic resistance in gram negative organisms.
They allow antibiotics to diffuse into the cell from outer membrane to inside.
mechanism of ceftriaxone resistance
structural changes in penicillin binding proteins is one of many mechanisms of ceftriaxone resistance.
why is there no vaccine against Neisseria gonococcal bacteria. and it is important to treat partner
Because antibody response is against gonococcol pili
and Pili gene undergoes large amount of gene recombination giving rise to antigenic variation.
Hence prior infection and antibodies do not offer immunity,
treating partner is important
no vaccine can be developed.
gonococcal antibiotic resistance is from
plasmid conjugation.
where does the fungi grow in mucormycosis
Mucor, rhizopus and absidia species grow in the walls of blood vessels of paranasal sinuses.
Causes ischemic necrosis and black eschar
Morphology of mucormycosis fungi
They exists as mold form only.
Aseptate wide 90 degree branching mold.
single stranded RNA virus leading to loss of brain mass and subcortical calcifications in brain
ZIKA virus. Transmitted by Aedes bite.
Disrupts fetal neural progenitor cells, migration and neural development affected.
Leads to fetal demise. Surviving babies are given supportive treatment only.
Common cause of aseptic meningitis
Enterovirus (Most common)
Arbovirus
HSV 2
What diseases vibrio vulnificus can cause
Like other vibrio– -watery diarrhoea esp severe in chronic liver disease patient
Wound infections
Severe rapid onset sepsis
dipicolinic acid
content of spore
who can form spore
only gram positive bacteria