Microbiology - Bacteriology

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green ring around colonies on blood agar

alpha-hemolytic streptococcus

S. pneumoniae - optochin sensitive, positive quellung rxn

Strep viridans (S. mutans) - optochin resistant, negative quellung reaction

clear area of hemolysis on blood agar.

List 4 bugs

beta-hemolytic bacteria:

streptotococcus
S. pyogenes - bacitracin sensitive
Group B Strep (S. agalactiae) - bacitracin resistant

S. aureus - catalase and coagulase positive

Listeria monocytogenes
(tumbling motility, meningitis in newborns, unpasteurized milk)

no hemolysis on blood agar, G+ and catalase negative

gamma-hemolytic streptococcus

peptostreptococcus
enterococcus (E. faecalis)

Catalase:

Fxn?
What bugs have it?
What disease lends particular vulnerability to catalase positive bugs?

Degrades hydrogen peroxide before human myeloperoxidase (neut's and monocytes) can convert it to bleach and kill bug

Staphylococcus

Chronic Granulomatous Disease
b/c lack NADPH oxidase, rely on using bacteria-produced hydrogen peroxide to make bleach to kill bacteria

Coagulase:

Fxn?
What bug has it?

Converts fibrinogen to fibrin --> clot
that S. aureus can hid in and evade our immune system!

S. aureus:

virulence factor?

2 MECH's of disease-generation:

In the heart and bones, causes?

Protein A - binds Fc of IgG --> prevents complement fixation, opsonization and phagocytosis

MECH's
1. Inflammatory
(skin/wound infections, organ abscesses, pneumonia, bacteremia, sepsis)

2. Toxins
TSST-1 toxin --> toxic shock syndrome
exfoliative toxin --> scalded skin syndrome
enterotoxins (preformed) --> rapid-onset food poisoning

Acute bacterial endocarditis (even on normal valves)
Osteomyelitis (#1 cause of)

S. epidermidis

algorithm classification
component of?

MECH of infection?

Causes?

catalase-positive, coagulase negative
novobiocin-sensitive

normal skin flora (contaminates blood cultures)

MECH - produces adherent biofilms --> infects prosthetic devices and IV catheters -->

endocarditis, esp in IVDU

Streptococcus pneumoniae:

algorithm classification

most common cause of?

significance of capsule?

catalase-neg, alpha-hemolytic, optochin sensitive

"Most OPtochinin Sensitive"

Most common cause of:
M - Meningitis
O - Otitis media (children)
P - Pneumonia
S - Sinusitis

sepsis in sickle cell anemia and splenectomy

SHiN - Encapsulated. IgA protease. Transformation. Diplococcus
"rusty sputum"

dental caries, subacute bacterial endocarditis

streptococcus viridans

catalase-neg, alpha-hemolytic, optochin resistant

What patients are at risk of subacute baterial endocarditis from s. mutans or s. sanguis?

only those with turbulent flow heart problems / altered valves

prophylactic penicillin before dental procedures

S. pyogenes:

algorithm classification?
3 MECH's of causing disease?

catalase-neg, beta-hemolytic, bacitracin-sensitive

MECH's
1. Pyogenic
(pharyngitis ("strep throat"), cellulitis, impetigo, endocarditis, necrotizing fasciitis, folliculitis

2. Toxigenic
(scarlet fever-erythrogenic toxin --> scarlet fever ("strawberry tongue"), toxic shock syndrome

3. Immunologic
(rheumatic fever, acute glomerulonephritis ("subepithelial humps")

S. pyogenes:

Main virulence factor?
What causes rheumatic fever?
What detects recent S. pyogenes infection?

M protein - prevents phagocytosis

Anti-M protein Ab's! - d/t mimicry/similarity of heart valves to M protein...

ASO titer = anti-streptolysin O

What 3 skin infections are caused by both s. aureus and s. pyogenes?

1. Folliculitis - infected hair follicles

2. Cellulitis - deep skin infection (draw border!)

3. Impetigo - superficial vesicle ruptures --> thick, yellow, weeping crusted lesion "honeycomb lesion,"

S. agalactiae

algorithm classification?
causes?
normal flora where?
prevent transmission how?

catalase-neg, beta-hemolytic, bacitracin-resistant

"B for Babies!"

Causes: pneumonia, meningitis, sepsis
(mainly in babies)

vaginas of 25% of women

prophylactic ampicillin during labor

Enterococci

algorithm classification?
specific bug names?
found?
cause?
can grow in?
very good at acquiring?

catalase-neg, gamma-hemolytic
E. faecalis, E. faecium
normal colonic flora

cause - UTI, subacute endocarditis, biliary tract infections

can grow in 6.5% NaCl

resistance --> VRE

Enterococci - S. bovis

colonizes?
can cause?

the gut

bacteremia and subacute endocarditis in COLON CANCER patients

C. diphtheria:

classification?
toxin -->
S/S?
Dx?
Px

G+ rod

toxin --> ADP ribosylation of EF-2
S/S - grayish-white pharyngitis (pseudomembranous) with lymphadenopathy

Dx - swab it (do NOT scrape it; this will release the toxin!);
metachromic (blue and red) granules

Px - toxoid (antitoxin) vaccine (TDaP)

Diphtheria toxin (mnemonic)

ABCDEFG
A - ADP ribosylation
B - Beta prophage (encoded by)
C - Corynebacterium
D - Diphtheriae
E, F - Elongation Factor 2
G - Granules (metachromic blue and red)

ADP ribosylation of EF-2 inhibits protein synthesis

3 fatal infections in neonates

Group B Strep (S. agalactiae)
Listeria
E. coli

Clostridia

classification?
bugs/toxins?

G+ rods, spore-forming, toxin-producing, obligate anaerobes

tetani - blocks GABA and Gly release --> trismus, risus sardonicus

botulinum - blocks presyn ACh release --> flaccid paralysis

perfringens - alpha toxin / lecithinase --> gas gangrene, hemolysis, myonecrosis

dificile - cytotoxin (an exotoxin), that kills enterocytes

Clostridium dificile

toxin?

cytotoxin - kills enterocytes

S/S - pseudomembranous colitis
often 2'ary to Abx use, esp clincamycin or ampicillin

Dx - stool sample showing C. dif toxin

Tx - metronidazole, or vancomycin (esp oral)

Anthrax

Caused by?
The only bacterium with a?
Disease depends on exposure. Explain

Bacillus anthracis - G+ rod, spore-forming, obligate aerobe

Polypeptide capsule - contains D-glutamate)

Cutaneous:
Contact --> black eschar (painless ulcer); can progress to bacteremia and death
(caused by lethal factor and edema factor - an adenylate cyclase)

Inhalation of spores:
flu-like symptoms, rapidly progress to fever, pulmonary hemorrhage, mediastinitis, shock
"Woolsorter's disease"

Listeria monocytogenes

classification?
acquired via?
how does it move from cell to cell?
the only G+ with?
characteristic _____ _____?
EPI -

G+ rod, facultative intracellular

ingestion of unpasteurized milk/cheese and deli meets

"actin rockets"
endotoxin/LPS/Lipid A
tumbling motility

newborns and immunocompromised

Listeria

Causes?

neonatal meningitis in newborns --> death

amnioinitis, septicemia, and spontaneous abortion in pregnant women

granulomatosis infantiseptica
meningitis in immunocompromised

mild gastroenteritis in healthy individuals

Actinomyces vs Nocardia

classification?
oxygen use?
causes?

Both - G+, branching filaments

Actinomyces:
obligate anaerobe
oral-facial abscesses that may drain through sinus tracts in skin
normal oral flora

Nocardia:
obligate aerobe
pulmonary infection in immunocompromised

Tx for Actinomyces vs. Nocardia?

SNAP

Sufla for Nocardia

Actinomyces use Penicillin

why should pregnant women not eat soft cheeses, deli meets, or unpasteurized milk?

Listeria
it can kill the baby

Infection with M. tuberculosis:

In nonimmune host (child) -->
In partially immune hypersensitized host (adult) -->

primary tuberculosis

reinfection, --> secondary tuberculosis

Primary TB:

characterized by?

Progression - 4 outcomes:

S/S - lymphadenopathy of hilar nodes + Ghon focus (usually LOWER lobes) = Ghon complex

Progression:
1. heals by fibrosis - immunity and hypersensitivity --> TB positive

2. progressive lung dz (HIV) --> death (rare)

3. severe bacteremia --> miliary TB --> death

4. preallergic lymphatic or hematogenous dissemination --> dormant tubercle bacilli in several organs --> reactivation in adult life --> extrapulmonary TB

Secondary TB

aka -
characterized by?
S/S
Progression?

aka - reinfection --> reactivation

Fibrocaseous cavitary lesion - UPPER lobe
S/S - hemoptysis
Extrapulmonary TB

Extrapulmonary TB

Result of?
S/S - 5 organs/areas:

Adult reactivation of primary TB or reinfection causing 2'ary TB

S/S:
1. CNS - meningitis, parenchymal tuberculoma
2. Vertebral body - Pott's dz - psoas abscess, *groin pain
3. Lymphadenitis
4. Renal
5. GI

PPD

What type of hypersensitivity?
Positive result requirement?
PPD+?

PPD-?

Type IV hypersensitivy
> 5mm induration

PPD+
"you have immune response to TB"
indicates current infection, past exposure, or BCG vaccinated

PPD-
no infection or anergic (can't generate response) d/t steroids, malnutrition, immunocompromise, sarcoidosis

Ghon focus

reflects primary infection/exposure

calcified scar in lung

Ghon complex

reflects primary infection/exposure

calcified scar in lung, PLUS lymphadenopathy (lobar, perihilar)

TB symptoms

fever, weight loss, night sweats, hemoptysis

Mycobacterium kansasii

Causes what in whom?

pulmonary TB-like symptoms in COPD pts

Mycobacterium avium-intracellulare

disseminated disease in AIDS pts

Mycobacteria

classification?
stain with?
culture on?

G+ rod
acid fast stain (Ziehl-Neelson)
culture on Lowenstein-Wilson agar

superficial skin --> osteomyelitis in aquarium-handler, shipyard worker, swimming pool

Mycobacterium marinum

most common cause of cervical lymphadenitis in children

Mycobacterium scrofulaceum

Leprosy
aka-

Caused by?
What env does this bug like?
Can it be grown in vitro?
Reservoir in US?

Hansens's disease

Mycobacterium leprae - acid fast rod
cool environments - skin and superficial nerves
No
armadillos

Leprosy

2 types:

2 types:

Lepromatous:
S/S - Leonine facies - loss of eyebrows, nasal collapse, lumpy earlobe.
Loss of sensation in fingers, hands
infectious - LEpromatous can be LEthal
d/t failed cell-mediated immunity

Tuberculoid:
limited to a few hypoesthetic nodules
NOT infectious

Treatment for Leprosy

Screen for:
Tx -

G6PD deficiency:
Dapsone --> hemolysis and methemoblobinemia

Tx - longterm oral dapsone + rifampin + clofazimine

loss of sensation in fingers, hands; loss of eyebrows, nasal collapse

Leprosy

(Mycobacterium Leprae)

pink colonies on MacConkey's agar

Lactose fermenters:

Lactose is KEE (fast)

Klebsiella
E. coli
Enterobacter

MacConKEE'S agar

Citrobacter
Serratia

Why are G- resistant to penicillin?

The G- outer membrane inhibits entry of penicillin G and vancomycin

(may be susceptible to ampicillin)

G- diplococci,
ferment glucose,
produce IgA protease,
transformation

Neisseria
(both meningitidis and gonorrhoeae)

Gonococci:

Capsule?
Maltose fermenter?
Vaccine?
Transmission?
Causes?

Capsule - No
Maltose fermenter - No
Vaccine - No
Transmission - sexually

Causes:
gonorrhea
septic arthritis (most common cause of arthritis in young adults)
neonatal conjunctivitis
PID,
Fitz-Hugh-Curtis syndrome
(ascending infection, ultimately of liver capsule)

Meningocci

Capsule?
Maltose fermenter?
Vaccine?
Transmission?
Causes?

Capsule - Yes
Maltose fermenter - Yes
Vaccine - Yes
Transmission - respiratory and oral secretions

Causes:
meningitis,
sepsis
Waterhouse-Friderichesen syndrome

H. influenzae:

classification?
causes?
does not cause?
virulence factors?
culture on?
tx?
prophylaxis?

G- coccoid

Causes: HaEMOPhilus influenzae
E - Epiglottitis ("cherry red", "thumb sign" on XRay)
M - Meningitis
O - Otitis Media
P - Pneumonia (typical/lobar)

Does NOT cause the flu!

IgA protease, capsule (esp type B)

chocolate agar - with factor V (NAD+) and X (hematin)

H. influenzae meningitis:

tx?
prophylaxis?

tx - ceftriaxone
prophylaxis - rifampin for meningitis

Legionella

classification?
stain with?
culture on?
diagnosis?
transmission?
Tx?

G- rod, poor Gram stain
silver stain
charcoal yeast extract with iron and cysteine
dx - Ag in urine
transm - aerosol from environmental water source (air conditioning)
NO person-person transmission!
Tx - erythromycin

Pseudomonas aeroginosa

classification?
causes?

G- rod, aerobic
non-lactose fermenter, oxidase-positive

PSEUDOmonas:
P - Pneumonia (esp in CF pts)
S - Sepsis (black lesions on skin)
E - External otitis (swimmer's ear)
U - UTI
DO - Drug use and Diabetic Osteomyelitis

+ burn victims, contact lens infection

Pseudomonas aeroginosa

virulence factor?
pigment?
tx?

endotoxin (fever, shock)
exotoxin A (inactivates EF-2, just like diphtheria toxin)

pyocyanin (blue green pigment)

Tx - 2 abx = gentamycin + piperacillin

COFFEe

Enterobacteriaceae

All G- rods:
Klebsiella, E. coli, Enterobacter
Serratia, Salmonella, Shigella
Proteus

C - Capsular (K) antigen - virulence factor
O - O antigen (the polysaccharide of endotoxin)
F - Flagellar antigen - all motile
F - Ferment glucose
E - Enterobacteriaceae

E. coli

classification?
4 categories?

G- rod, fast lactose fermenter

4 categories:
EIEC - invades intestinal mucosa --> dysentery
EHEC - hemorrhagic diarrhea (dysentery)
ETEC - traveler's diarrhea (rice-water)
EPEC - pediatrics

Tx - TMP-SMX, fluoroquinolones

Explain the difference btwn the dysentery of EIEC and EHEC

BOTH
have shiga-like toxin - cleaves 60S rRNA
cause necrosis and inflammation of GI mucosa

EIEC - microbe AND toxin invade mucosa
EHEC - only toxin invades (O157:H7)

HUS

E. coli O157:H7

What is ETEC similar to?
Why?

Vibrio cholera.

labile toxin stimulates Gs
(while stabile toxin stim guanylate cyclase)

Both cause voluminous rice-water traveler's diarrhea

What is EPEC similar to?

Rotavirus

No toxin produced
Adheres to apical surface, flattens villi, prevents absorption

Also, mainly seen in children
(EPEC - Pediatrics)

Salmonella and Shigella

algorithm?
MECH?
Cause?
Transmission?

Major difference?

G- rod, non-lacose fermenters

MECH - invade intestinal mucosa
Cause - bloody diarrhea and fever
Transm - "Food, Fingers, Feces, Flies"

Difference - MOTILITY!
Salmonella - swim! -> hematogenous spread
Shigella - don't

Salmonella:

algorithm?
produce?
what cell type responds?
causes?
tx?

G-rod, non-lactose fermenter, motile

hydrogen sulfide (H2S)
monocytic response

Causes:
1. Typhoid fever - fever, diarrhea, headache, rose spots on abdomen, near umbilicus
2. osteomyelitis in sickle cell pt
3. food assoc diarrhea (most common cause)

Tx - do NOT give abx - will prolong the infection!

Shigella:

algorithm?
causes?
tx?

G- rod, non-lactose fermenter, nonmotile

1. bacterial dysentery
2. Shigella flexneri --> Reiter's syndrome

2 bugs that move via actin

Listeria monocytogenes:
"actin rockets" - intercellular movement

Shigella
actin polymerization - intracellular movement

Yersinia enterocolitis

Gram?
transmission?

G-
transm - puppy feces, contaminated milk or pork
daycare centers

H. pylori

Classification?
Causes?
What env does urease create?
Dx?
Tx?

G- rod, urease positive

Gastritis, duodenal ulcers, gastric adenocarcinoma, lymphoma (MALToma)

alkaline
Dx - urea breath test

Tx - triple therapy:
1. metro, omeprazole, clarithromycin
2. metro, bismuth, tetracycline/amoxicillin

Spirochetes:

List them.
How are they each visualized?
Tx?

BLT. B is Big

Borrelia - aniline dyes / Giemsa stain
Leptospira
Treponema - dark-field microscopy

Tx - doxycycline

Leptospira

classification?
found in?
most prevalent in?

Causes:

question-mark shaped spirochete

found in water contaminated by animal urine
tropics

Causes:

1. Leptospirosis - jaundice, photophobia with conjunctivitis
2. Weil's disease - jaundice, azotemia, fever, hemorrhage, anemia

Lyme disease
geographic location?
caused by?
transmitted by?
presentation?
S/S?
treatment?

Borrelia burgdorferi, a spirochete
NE United States
Ixodes tick

Presentation: erythema chronicum migrans:
expanding "bull's eye" red rash with central clearing

S/S - BAKE a Key Lyme Pie

B - Bell's palsy (can be bilateral)
A - Arthritis (mono- or migratory poly-)
K - Kardiac block (AV node)
E - Erythema chronicum migrans

Tx - doxycycline, or ceftriaxone (for chronic arthritis)

Syphilis

Caused by?
MECH
Tx -

Primary
Secondary
Tertiary
Congenital

Treponema pallidum - a spirochete
MECH - small vessel disease
Tx - penicillin G (IV, IM)

Primary (localized):
painless chancre

Secondary (systemic):
Palms/soles rash, condylomata lata, alopecia areata (patch of complete balding)

Tertiary:
gummas (chronic granulomas)
aortitis, aortic regurg (vasa vasorum destruction)
tabes dorsalis
Argyll Robertson pupil

Congenital:
saber shins, saddle nose, CN VIII deafness, frontal bossing, notched incisors, blood-tinged sputum

VDRL and FTA positive

Treponemal infection.

Treat with penicillin G

VDRL false positives

V - viruses (EBV, hepatitis)
D - drugs
R - rheumatic fever
L - lupus and leprosy

Rickettsiae

where can they live?
why?
classic triad of S/S?
transmission?
Dx?

Queer rickettsiae?

obligate intracellular
need CoA and NAD+

Classic triad: headache, fever, rash
transmission - arthropod vector
Dx - positive Weil-Felix rxn

Coxiella; causes Q fever, transmitted by aerosol, causes pneumonia, neg W-F rxn

Rickettsial diseases and vectors:

RMSF
Endemic typhus
Epidemic typhus
Ehrlichiosis
Q fever

Tx?

RMSF - (tick) - Rickettsia rickettsii

Endemic typhus - (fleas) - R. typhi
Epidemic typhus - (human body louse) - R. prowazekii
Ehrlichiosis - (tick) - Ehrlichia
Q fever (inhaled aerosols) - Coxiella burnetii

Tx - tetracycline for all!

Difference btwn R. typhi and R. prowazekii?

Similarity?

Difference:
R. typhi (fleas) - endemic typhus - (constant in population)
R. prowazeckii - (human body louse) - epidemic typhus (sudden increase in population)

BOTH:
rash that starts on trunk, spreads outward but does NOT involve palms and soles

Coxiella burnetii

kind of bug?
causes?
why queer?

Rickettsial

Q fever - interstitial pneumonia, fever

Queer - in contrast to other Rickettsial bugs, transmitted by aerosol, causes pneumonia, neg Weil-Felix rxn, forms spores

Explain Weil-Felix rxn.

Notably negative in:

Pts w Rickettsial infection have anti-Rickettsial Ab's.

Pt serum mixed with Proteus Ag's, Ab's cross react ->
agglutination

Coxiella burnetii / Q fever

cell wall lacks muramic acid

stain needed to detect it?

Tx?

Chlamydia

Geimsa

Erythromycin or tetracyline

There are 2 forms of chlamydia.
Which is infectious?
Which replicates in cell by fission?

Elementary body is Enfectious and Enters cells via endocytosis

Reticulate body Replicates in cell by fission

Which chlamydial species cause interstitial pneumonia?

C. pneumoniae
C. psittaci

Chlamydia trachomatis serotypes:

ABC?
D-K?
L1-L3?

ABC serotypes:
Africa, Blindness, Chronic infection

D-K:
(standard S/S - PID, urethritis, reactive arthritis, ectopic pregnancy, neonatal pneumo, neonatal conjunctivitis

L1, L2, L3:
Lymphogranuoma venereum - ulcers, unguinal lymphadenitis, rectal dz
(often mistaken for Chron's or UC)

only bacterial membrane containing cholesterol

Tx?
Epi?

Mycoplasma pneumonia

Tx - erythromycin or tetracycline
NOT penicillin - no cell wall!

Pt's under 30 yo, military recruits, prisons

high titer of cold agglutinins

Mycoplasma pneumoniae

cold agglutinins = IgM
can agglutinate or lyse rbc's

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