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
specific chemical of capsule of B anthracis
B anthracis capsule is made of poly D glutamate.
function of capsule and slime layer
capsule prevents phagocytosis
Slime layer helps adherence to plastic or foreign non living things like catheter
Where is endotoxin situated
In outer membrane of gram Negative organisms
what three chemical together form endotoxin
LIPID A - Induces INF and IL1
O specific polysaccharide - ANTIGEN O
Core oligosaccharide
Only one structure unique to gram Positive cell wall
Lipo teichoic acid
THree structure unique to gram negative organism
Periplasmic space where beta lactamase enz is located.
Outer membrane which contains PORINS and ENDOTOXIN
Cell wall is cross linked by which enz
transpeptidase.
Site of ceftriaxone action.
Immune response in GM negative is from endotoxin which stimulated TNF and IL 1 release. What part of gram positive bacteria is responsible for release of these
Lipoteichoic acid.
PBP and certain transport enz are located in which part of cell
cytoplasmic membrane
ZN stain organisms
Mycobacteria and nocardia
Cryptosporidium ova– DIarrhoea in HIV
examples of aerobic bacteria — use oxygen for ATP generation
Mycobacteria and nocardia
Pseudomonas aeruginosa
Bordetella pertusis
THree prime effects of endotoxin
Macrophage activation by TLR 4 and CD14
Complement activation (C3a and C5a)
DIC causative– tissue factor 12 activation
Macrophage activation in endotoxic shock is because of release of what substances from macrophage
IL1 and IL 6 —- fever
TNF alpha——–Fever and hypotension
Nitric oxide- vasodilator—- hypotension.
biofilm producing bacteria (strep/ staph/ H infl/Pseu) all most imp organism
VGS (dental plaque and IE)
Staph epidermidis– normal flora of skin and forms biofilm of catheters and prosthesis
Unencapsulated non typeable H influenza- Otitis media
PSeudomonas – LEns keratitis, cystic fibrosis cavity lining and ventilator associated pneumonia
Autoclave settings
121 degree celsius
15 min to kill spores.
Two main opsonins for bacteria
C3b and IgG
name the three conjugated vaccine. Why are they conjugated
COnjugated vaccines : when a carrier protein is added to antigen which is a capsular polysaccharide.
Polysaccharide alone cannot mount T cell immune response and class switching.
Hence encapsulated organism vaccines are conjugated vaccines.
Remember the asplenic vaccines – S. Pneumoniae, N meningitis, H influence Type B.
Name the pneumococcal vaccines
There are two available. Conjugated and unconjugated with protein
Conjugated is called PCV 13
Unconjugated is called PPSV 23-pneumococcal PS polysacharide v- vaccine.
basic Enzymes tests in microbiology
Catalase
Coagulase- converts fibrinogen to fibrin
Urease- urea to ammonia
Oxidase- adds hydrogen to oxygen producing Water or H2o2
Enterococci are PYR
Positive
GAS s pyogenes are PYR
positive
GBS S agalactiae is PYR
Negative
Hippurate test positive organisms
Gardenella
Campylobacter
Listeria
S agalactiae (use this test to differentiate with S pyogenes sometimes)
Cryptococcus neoformans is a yeast causing Meningitis in HIV positive patients. Stain used is
Indian ink preparation.
Shows thick polysaccharide capsule
VZV immunity is primarily
Cell mediated immunity
chinese letter bacteria joined by V or Y shaped
Granules staining with aniline dyes (methylene blue, albright stain) at poles.
Corynebacterium diphtheria
growing hyphae are known as germ tubes. They are seen in
Candida albicans when they are inoculated into serum at 37 degree celsius 98.6 F for 3 hrs
It is formation of true hyphae from yeast.
On light Microscopy… candida appears as budding yeast with pseudohyphade. Only albicans when grown at particular temp shows true hyphae. and hence this test is used to differentiate candida albicans from other candidial species.
stains for cryptococcus neoformans
- Methanamine silver stain – identifies yeast form of cryptococcus– round cells with narrow based budding
- Indian iNk stain- thick halo of polysaccharide capsule
- Mucicarmine stain— red colour of capsule.
Only pathogenic fungus that has polysaccharide capsule
Cryptococcus neoformans.
Most common cause of bronchiolitis (wheezes and rales) in less than 2 year old
RSV
Intestinal ulcers with undermining edges (flask shaped) and has trophozoites
Entameba histolytica
two protiens that help entamoeba histolytic in invasion
enz– proteases – lyse host membranes and sec IgA
Protein LECTIN helps in adhesion
introduces amoebic PORIN and causes Contact dependent cytotoxicity.
OHIO and MISSISIPI river valleys
HISTOPLASMOSIS
causes of genital ulcer dieases
- Herpes – painful multiple vesicular ulcers
- syphillis– PAINLESS single non vesicular clean base heaped up margins with non tender rubbery nodes
- Chancroid– painful deep ulcers with pus and matted and suppurative nodes
- Granuloma inguinale – PAINLESS multiple SERPINGINOUS ulcers without nodes.
Granuloma inguinale is also known as —- cause by organism —-
Granuloma inguinale is also known as DONOVANOSIS cause by organism KLEIBSELLA GRANULOMATOSIS
genital chancroid is caused by organism———–
genital chancroid is caused by organism HEMOPHILUS DUCREYI
Presentation of Lymphogranuloma venerum and primary syphilis is same. Where is the difference in clincal characteristics
Both have single painless ulcer
Ulcer in syphillis has heaped up margins
nodes are painless in sypillis and painful in chlamydia
where do animals harbour leptospira
in proximal renal tubule and secrete them in urine
Flu like illness with lymphadenapathy, liver and renal failure and end organ damage with bilateral non inflammatory conjunctival suffusion is seen in
leptospirosis.
Bilateral conjunctival suffusion is an important diagnostic clue.
Donovan bodies and donovani bodies are different
DONOVAN – kleibsella granulomatis– granuloma inguinale. Rod shaped gram negative organism in macrophages
DONOVANI– amastigotes within macrophages– leishmaniasis kala-azar
Asymmetric LMN type flaccid paralysis
signs of meningitis
ANd /or rash fever
And / or parkinsons disease
west nile neuroinvasive disease.
Bite of culex mosquitoes
summer florida warm climates
Intermediate host- birds
elevated erythrocytes with lymphocytic pleocytosis in CSF
herpes simplex encephalitis
filamentous gram positive anaerobic to microaerophilic organism responsible for causing dental caries and orofacial abscesses with draining sinuses
Actinomyces
Dz is called actinomycosis.
Multiple interconnected abscesses.
PID in a female patient with uterine IUD
pelvic actinomycosis
which cephalosporins are used for pseudomonas
3rd gen- ceftazidime
4th gen– cefepime
Bactrim– TMP + SMX is used against which organisms
- Pneumocystis jerovecii
- Toxoplasma gondii
- Stenotrophomonas Maltophilia
- Nocardia.
Cold agglutinins which causes clumping of blood RBC when placed in ICE and then whn brought to room temp disappears is seen in which infection
Mycoplasma pneumoniae.
Cold agglutinins are formed in mycoplasma infection because
Adhesive protein L surface antigen leads to development of Ig M type antibodies
Which are pentameric in form
Cross react with antigens on the surface of RBC and in cold areas of body like periphery or pinna cause complement activation and intravascular hemolysis (Cf Ig G warm antibodies cause extravascular hemolysis)
diseases leading to formation of cold agglutinins
mycoplasma pneumoniae infection
hematological malignancies
Infectious mononucleosis EBV
High fever with relative bradycardia
Cruise travel
neuro and GI symptoms
chest lung insterstitial patchy infiltrates
Little or no micro-organisms on sputum only neutrophils
hyponatremia
Legionella
Only pneumonia with hyponatremia
Legionella
grows of BYCE medium
urinary antigen testing positive.
what microbiology concept is seen as predisposing factor in ankylosing spondyltitis
ALTERED GUT MICROBIOME AND DEFECTS IN MUCOSAL BARRIER.
induces Th1 and Th17 helper cells to release interleukin 17
this is due to altered antigen presentation which is due to HLA b27 genetics.
IL 17 causes release of TNF alpha and prostaglandins
causing systemic bony erosions and abnormal bone growth.
What drugs are used in treatment of anklyosing spondyltiis
It is IL-17 induced release of TNF alpha and PGs which is causing damage.
Drugs like NSAIDS and antiTNF alpha are thus used.
Bacteria responsible for acute suppurative parotitis
Staph aureus
mixed oral anaerobes
Causative organism for cellulitis
NON PURULENT CELLULUTIS – Beta hemolytic streptococci OF THESE GAS - S PYOGENES majorly responsible
PURULENT CELLULITIS- pus- staph aureus (because of virulence factor– kn as panton valentine leukocidin causes skin abscess)
aversion to smoking is caused by which viral infection
hepatitis A
