Clinical Bacteriology I Flashcards
Describe characteristics of S. aureus
Gram +
Catalase +
Coagulase +
Describe characteristics of Clostridium
Gram +
bacilli
anaerobe
Describe characteristics of Listeria
Gram +
bacilli
aerobe
Describe characteristics of Mycobacterium
acid fast
Describe characteristics of Strep. pneumoniae
Gram + Cocci catalase - capsule alpha hemolysis optochin sensitive bile soluble (lysed by bile)
Describe characteristics of Strep. pyogenes
Gram + cocci catalase - beta hemolysis bacitracin sensitive
Describe characteristics of Strep. agalactiae
Gram + cocci catalase - beta hemolysis bacitracin resistant
Is Staph. epidermidis or Staph. saprophyticus resistant to novobiocin?
Staph. saprophyticus - resistant
Staph. epidermidis - sensitive
Is Strep. pneumoniae or Strep. viridans resistant to optichin?
Strep. pneumoniae - sensitive
Strep. viridans - resistant
Is group B strep or group A strep resistant to bacitracin?
group B strep - resistant
group A strep - sensitive
Which bacteria are alpha-hemolytic?
Streptoccocus pneumoniae
Viridans streptococci
What do alpha-hemolytic bacteria look like on blood agar?
green
What do beta-hemolytic bacteria look like on blood agar?
clear area of hemolysis on blood agar
Which bacteria are beta-hemolytic?
staph. aureus
Strep. pyogenes
Strep. agalactiae
Listeria monocytogenes
What is MRSA and why is it important?
Methicillin resistant S. aureus
important cause of serious nosocomial and community-acquired infections
resistant to methicillin and nafcillin because of altered penicillin-binding protein
What is TSST from S. aureus and what symptoms does it cause?
Toxin shock syndrome toxin
Binds to MHC II and T-cell receptor –> polyclonal T-cell activation
Presentation: fever, vomiting, rash, desquamation, shock, end-organ failure
What predisposes individuals to toxic shock syndrome?
vaginal or nasal tampons
Where does St. aureus commonly colonize in the body?
nose
How does Staph. epidermidis infect?
infects prosthetic devices and IV catheters by producing adherent BIOFILMS
What is the 2nd MCC of uncomplicated UTIs in young women?
Staph. saprophyticus
What are the diseases that S. pneumoniae commonly causes?
Meningitis
Otitis media (in children)
Pneumonia
Sinusitis
What is the characteristic shape of S. pneumoniae?
Gram + lancet-shaped diplococci
Where are viridans streptococci normally located?
normal flora of the oropharynx
What diseases do viridans streptococci cause?
dental caries (Strep. mutans) subacute bacterial endocarditis (S. sanguinis)
How does Strep. sanguinis cause subacute bacterial endocarditis?
makes dextran –> bind to fibrin-platelet aggregates on damaged heart valves
What is the JONES Criteria for rheumatic fever?
MAJOR CRITERIA
Joints - polyarthritis
O - carditis (O should be shaped like a heart…)
Nodules (subcutaneous)
Erythema marginatum
Sydenham chorea (face, tongue, upper limbs)
MINOR CRITERIA fever arthalgias increased ESR (or CRP) increase PR interval
What are physical symptoms of Scarlet Fever?
scarlet rash (starting on trunk and neck but SPARES the face) with sandpaper-like texture
strawberry tongue
circumoral pallor
What location does Strep. agalactiae (group B strep) colonize in the body?
vagina
If a women screens + for a group B strep culture before delivery, what should be done?
intrapartum penicillin prophylaxis
What location does enterococci (group D strep) colonize in the body?
normal colonic flora
What diseases are caused by enterococci (group D strep)?
UTI
biliary tract infections
subacute endocarditis (following GI/GU procedures)
What diseases are caused by Strep. bovis?
bacteremia
subacute endocarditis in colon cancer patients
What are symptoms on Diphtheria?
pseudomembranous pharyngitis
lymphadenopathy
myocarditis
arrythmias
What type of agar is used to detect c. diphtheriae?
black colonies on cystine-tellurite agar
What are examples of spore-forming Gram + bacteria found in soil?
Bacillus anthracis
Clostridium perfringens
C. tetani
How can spores be killed?
steaming at 121 degrees Celsius for 15 minutes
What is unique about Bacillus anthracis compared to other bacteria?
only bacterium with a polypeptide capsule (contains D-glutamate)
What are the two types of anthrax infections?
Cutaneous anthrax
Pulmonary anthrax
What is the pathogenesis of a cutaneous anthrax infection?
boil-like lesion –> ulcer from black eschar (painless, necrotic) –> uncommonly progresses to bacteremia and death
What is the pathogenesis of a pulmonary anthrax infection?
inhalation of spores –> flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinhtis, and shock
Why is the pulmonary anthrax infection also called Woolsorters’ disease?
inhalation of spores from contaminated wool
In what food is bacillus cereus usually found?
reheated rice
What disease does Bacillus cereus cause?
emetic type food poisoning
diarrheal type food poisoning
Where does Listeria monocytogenes like to live?
intracellularly
How is Listeria monocytogenes acquired?
ingestion of unpasteurized dairy products and deli meats
What is unique about Listeria monocytogenes?
only gram + organism to produce LPS
What is the treatment for Listeria monocytogenes infection?
gastroenteritis is usually self limiting
infants, IC pts, and elderly w/ symptoms of meningitis - AMPICILLIN
Actinomyces vs. Nocardia
Gram + anaerobe —– Gram + aerobe
Not acid fast ————- acid fast (weak)
normal oral flora ——– found in soil
causes oral/facial abscesses that drain through sinus tracts, forms yellow “sulfur granules” ——– causes pulmonary infections in IC pts and cutaneous infections after trauma in IC pts
Treat w/ penicillin ——– Treat with sulfonamides
BOTH form long, branching filaments resembling fungi
What will result in positive PPD test?
current infection
past exposure
BCG vaccination
What will result in a negative PPD test?
no infection
anergic (steroids, malnutrition, IC pts)
sarcoidosis
What is a more specific test than PPD?
Interferon- gamma release assay (IGRA)
What are symptoms of TB?
fever, night sweats, weight loss, and hemoptysis
What are the strains of mycobacteria and what diseases do they cause?
Mycobacterium TB - TB
M. kansasii - pulmonary TB-like symptoms
M. avium- intracellulare - causes disseminated, non-TB disease in AIDS
What inhibits macrophage maturation and induces release of TNF-alpha in virulent TB strains?
cord factor
What inhibit phagolysosomal fusion on mycobacteria?
sulfatides (surface glycolipids)
What microorganism causes Leprosy (Hansen disease)?
Mycobacterium leprae
What are characteristic findings seen in lepromatous Hanson Disease?
presents diffusely over the skin
leonine (lion-like) facies
communicable
low cell-mediated immunity with a HUMORAL TH2 response
What are characteristic findings seen in tuberculoid Hanson Disease?
limited to a few hypothetic, hairless skin plaques
high cell-mediated immunity with a largely TH1-TYPE immune response
What is the treatment for Leprosy?
Tuberculoid Form: Multi drug therapy consisting of dapsone and rifampin for 6 months
Lepromatous Form: dapsone, rifampin, and clofazimine for 2-5 years
What is a signature finding of Leprosy?
“glove and stocking” loss of sensation
Which microorganisms are lactose-fermenting enteric bacteria?
Grow PINK COLONIES on MACCONKEY agar
Test with MacConKEE’S agar
Citrobacter Klebsiella E. coli Enterobacter Serratia
Are Gram - bacilli susceptible to penicillin G?
NO
But they may be susceptible to ampicillin and amoxicillin
What are the characteristics of Neisseria?
Gram - diplococci
ferment glucose
IgA proteases
often intracellular
What are the differences between N. gonococci and N. meningococci?
No polysaccharide capsule ——— polysaccharide capsule
No maltose fermentation ———— maltose formation
no vaccine ——————————– vaccine (none for type B)
sexually transmitted ——————- respiratory and oral secretions
gonorrhea, septic arthritis, neonatal conjunctivitis, PID, and Fitz-Hugh-Curtis Syndrome ——— meningococcemia and meningitis, Waterhouse-Friderichsen Syndrome
Condoms prevent transmission. Erythromycin ointments prevents neonatal transmission —— rifampin, ciprofloxacin, and ceftriaxone prophylaxis in close contacts
Tx: ceftriaxone + (azithromycin or doxycycline) for possible chlamydia coinfection ———— Tx: ceftriaxone or penicilin G
What are diseases caused by Haemophilus influenzae?
HaEMOPhilus
Epiglottitis* (“cherry red” in children)
Meningitis
Otitis media
Pneumonia
What is the treatment for H. influenzae infections?
mucosal infections - amoxicillin +/- clavulanate
meningitis - ceftriaxone (rifampin for prophylaxis in close contacts)
What stain is used best to detect Legionella pneumophila?
silver stain
Or can also grow on charcoal yeast extract culture with Fe and cysteine
How can you clinically detect Legionella pneumophila?
presence of Ag in urine
What are signs of Legionnaire’s Disease?
severe pneumonia
fever
GI and CNS symptoms
What is the treatment for Legionella pneumophila infection?
macrolide or quinolone
What are notable characteristics of Pseudomonas aeruginosa?
produces pyocyanin (blue-green pigment) grape-like odor
What diseases are associated with Pseudomonas aeruginosa infection?
PSEUDOmonas
Pneumonia Sepsis External otitis UTI Drug use Diabetic Osteomyelitis hot tub folliculitis
What is the treatment for Pseudomonas aeruginosa infections?
aminoglycoside + extended-spectrum penicillin (e.g. piperacillin, ticarcillin, cefepime, imipenem, meropenem)
When you think of Pseudomonas you should think of two things…
- WATER
2. BURNS
Ecthyma gangrenosum is a rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas bacteremia. It is commonly seen in which patients?
IC pts
What are E. coli virulence factors and which diseases do they help cause?
fimbriae - cystitis and pyelonephritis
K capsule - pneumonia, neonatal meningitis
LPS endotoxin - septic shock
What are the strains of E. coli and which diseases do they cause?
EIEC - dysentery (invasive)
ETEC - traveler’s diarrhea (watery)
EPEC - diarrhea usually in children
EHEC - dysentery, can cause HUS and thrombocytopenia
What distinguishes EHEC from the other forms of E. coli?
EHEC does NOT ferment sorbitol
What is notable about sputum from a Klebsiella infection?
looks like “currant jelly”
What are the 4 A’s to remember for Klebsiella?
4 A's: Aspiration pneumonia Abscess in lungs and liver Alcoholics di-A-betics
Compare Salmonella and Shigella
have flagella ——— no flagella
can disseminate hematogenously ——- cell to cell transmission; no hematogenous spread
many animal reservoirs ——- only reservoirs are humans and primates
antibiotics may prolong fecal excretion ——– antibiotics shorten duration of fecal excretion
invades intestinal mucosa and causes a monocytic response ——– invades intestinal mucosa and causes a PMN response
can cause bloody diarrhea —— OFTEN causes bloody diarrhea
BOTh do NOT ferment lactose
What disease is characterized by rose spots on the abdomen, fever, HA, and diarrhea?
Typhoid fever from salmonella typhi