Micro Flashcards
Classic signs of leprosy
Loss of sensation on the cool parts of the body associated with granuloma formation from acid fast bacilli
To what would a patient be susceptible if they wre deficient in the C5 complement protein?
Gram-negative bacteria, especially Neisseria species
gram-positive, catalase-negative, alpha-hemolytic diplococcus
streptococcus pneumoniae
viridans streptococci
atypical fungus
pneumocystis jiroveci
gram-negative, catalase-positive bacillus
pseudomonas aeruginosa
gram negative
rod (bacillus)
lactose nonfermenter
oxidase positive
gram-positive, catalase-positive, beta-hemolytic coccus in clusters
staphylococcus aureus
What is a common cause of pneumonia in patients with cystic fibrosis?
pseudomonas
gram + cocci
catalase +
coagulase +
s. aureus
gram+ cocci
catalase +
coagulase -
s. epidermidis (novobiocin sensitive)
s. saprophyticus (novobiocin resistant)
gram + cocci
catalase -
alpha-hemolytic
s. pneumoniae (capsule, optochin sensitive, bile soluble) viridans streptococci (no capsule, optochin resistant, bile insoluble)
gram + cocci
catalase -
beta-hemolytic
s. pyogenes (bacitracin sensitive) (group A)
s. agalactiae (bacitracin resistant) (group B)
gram + cocci
catalase -
gamma-hemolytic
group D (enterococcus, e.g., E. faecalis) - growth in bile and 6.5% NaCl
Nonenterococcus (S. bovis) - growth in bile, not in 6.5% NaCl
gram + bacilli
clostridium (anaerobic) bacillus (aerobic) corynebacterium mycobacterium tuberculosis (acid fast) listeria monocytogenes (beta-hemolytic)
gram + branching filaments
nocardia - aerobic, acid fast
actinomyces - anaerobic, not acid fast
gram - diplococci
Neisseria meningitidis (maltose fermenter) Neisseria gonorrhoeae (maltose nonfermenter)
Both produce IgA protease and ferment glucose
gram - “coccoid” rods
Haemophilus influenza
Bordatella pertussis
gram - rods
lactose fermenters
Fast:
Klebsiella
E. Coli
enterobacter
Slow:
citrobacter
serratia
gram - rods
lactose nonfermenters
oxidase (-): shigella salmonella proteus yersinia
oxidase (+)
pseudomonas
gram (-) comma-shaped
oxidase +
campylobacter jejuni (grows in 42 degrees) helicobacter pylori (produces urease) vibrio cholerae (grows in alkaline media)
Characteristics of Salmonella
- has flagella
- hematogenous spread
- produces hydrogen sulfide
- intestinal epithelial invasion –> monocytic response
- may cause bloody diarrhea
- has many animal reserviors
- antibiotics may prolong duration fecal excretion of organism
- does not ferment lactose
Characteristics of shigella
- no flagella
- cell-to-cell transmission (no hematogenous spread)
- does not produce hydgrogen sulfide
- intestinal epithelial invasion –> neutrophilic response
- often causes bloody diarrhea
- only found in humans and primates
- antibiotics shorten duration of fecal excretion of organism
- does not ferment lactose
Characteristics of N. gonorrhoeae
(1) no pollysaccharide capsule
(2) does not ferment maltose
(3) sexually transmitted
(4) no vaccine (due to rapid antigenic variation in pilus protein
(5) leads to: gonorrhea, septic arthritis, pelvic inflammatory disease, neonatal conjunctivitis, Fitz-Hugh_Curtis Syndrome
(6) condoms prevent sexual transmission; erythromycin ointment prevent neonatal transmission
(7) treatment: ceftriaxone (+ doxycycline or azithromycin for possible chlamydia infection)
(8) often intracellular (in neutrophils)
Characteristics of N. meningitidis
(1) polysaccharide capsule
(2) ferments maltose
(3) respiratory and oral secretions
(4) vaccine available (except for type B)
(5) leads to: meningococcemia, meningitis, Waterhouse-Friderichsen syndrome
(6) rifampin, ciprofloxacin, or ceftriaxone prophylaxis for close contacts
(7) treatment: ceftriaxone or penicillin G
Common characteristics of Neisseria
- -gram negative
- -diplococci
- -ferment glucose
- -produce IgA proteases
Klebsiella characteristics
Four As:
(1) Aspiration pneumonia (lobar)
(2) Abscess formation in lungs and liver
(3) Alcoholics
(4) diAbetics
Patients often produce “red currant jelly” sputum due to abundant polysaccharide capsules
Whats the relationship between penicillin and gram-negative bugs?
Gram (-) bacilli are resistant to penicillin G but may be susceptible to penicillin derivatives such as ampicillin and amoxicillin.
The gram negative outer membrane layer inhibits entry of penicillin G and vancomycin
Beta-hemolytic bacteria
Form a clear area of hemolysis on blood agar
streptococcus pyogenes
streptococcus agalactiae
staphylococcus aureus
listeria monocytogenes
What microorganism causes syphilis?
Treponema pallidum
Describe primary syphilis.
presentation, serology/diagnosis
- -localized disease
- -presents with painless, non-itchy, nodule (chancre)
- -screen with: VDRL, RPR
- -confirm diagnosis with FTA-ABS
- -can use dark-field microscopy to visualize treponemes in fluid from chancre
What do VDRL, RPR and FTA-ABS stand for?
VDRL - venereal disease research laboratory
RPR - rapid plasma reagin
FTA-ABS - fluorescent treponemal antibody absorption
Describe secondary syphilis.
presentation, screening/diagnosis
–disseminated disease that presents with:
- fever
- lymphadenopathy
- maculopapullar rash, often including palms and soles
- condylomata lata - whitish, wart-like lesion on genitals
VDRL/RPR for screening, FTA-ABS for confirmation
Dark field microscopy to visualize treponemes
*Followed by latent syphilis - (+) serology, asymptomatic
Describe tertiary syphilis
presentation, screening/diagnosis
(1) gummatous syphilis (chronic granulomas)
(2) cardiovascular syphilis (aortitis, vaso vasorum destruction –> increased risk of aortic aneurysm)
(3) late neurosyphilis (tabes dorsalis, Argyll-Robertson pupil)
- ->presents with broad-based ataxia, (+) Romberg sign, stroke without hypertension, Charcot joint
For neurosyphilis: test CSF with VDRL or RPR
What is VDRL?
venereal disease research laboratory
- -detects nonspecific antibody that reacts with beef cardiolipin
- -screening test for syphilis, sensitive, nonspecific, many false positives
Causes of false positives in VDRL test
VDRL:
Viruses (hepatitis, mononucleosis [EBV])
Drugs
Rheumatic fever
Lupus and leprosy
What is congenital syphilis?
syphilis present in utero and at birth
occurs when a child is born to a mother with syphilis
What are the clinical manifestations of neonatal syphilis?
Saber shins Hutchinson teetch (notched incisors) Mulberry molars Saddle nose CNVIII deafness Often results in stillbirth, hydrops fetalis
How should you treat neonatal syphilis?
Treat the mother early in pregnancy, as placental transmission typically occurs after the first trimester.
What are the serological tests for HIV diagnosis?
–ELISA - highly sensitive test used for screening; has a high false positive rate; a positive must be confirmed with: –Western Blot - specific test; high false negative rate, used to “rule in”
What test is used to monitor HIV prognosis and effect of therapy
- -HIV PCR/viral load - used to determine the amount of viral RNA in plasma.
- -High viral load is associated with a poor prognosis
- -Used to also monitor effect of drug therapy
What defines an AIDS diagnosis?
<14% of all lymphocytes
What do the ELISA and Western Blot tests look for?
antibodies produced to viral proteins
Why should ELISA and Western Blot tests be interpreted with caution?
These tests can be falsely negative in the first 1-2 months after HIV infection.
These tests can also be falsely positive initially in babies born to HIV positive mothers because the anti-gp120 antibody (IgG) crosses the placenta
Where does HIV replicate during the latent phase of the infection?
In the lymph nodes (where the CD4+ cells would normally be found)
What are the four general stages of untreated HIV infection?
(1) Flu-like symptoms
(2) Feeling fine (latent)
(3) Falling count (CD4+)
(4) Final crisis
How would you diagnose diphyllobothrium latum?
diagnost by finding operculated eggs or proglottids in feces
