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Micro-Organism Review Part 1
URI Rx
18
Pharmacology
Graduate
10/18/2010
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Term
Enterococcus spp.
(formerly Group D Streptococcus)

• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram positive cocci in pairs and chains
 Lab ID: no distinct blood hemolysis pattern
 Transmission: colonizes gut of humans and animals,
translocation and nosocomial acquisition
 Pathogenesis: no toxins
 Diseases: UTI, endocarditis, bacteremia, wound infections
 Complications: more common in gut pathology,
immunocompromised
 Prevention: isolation, handwashing, proper sanitation
Term
Staphylococcus aureus


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram positive cocci clusters, some w/
capsule
 Lab ID: Golden colonies, rapid growth, coagulase positive
 Transmission: Skin – nares/perineum, spread by
contact/airborne.
 Pathogenesis: Endo- and exotoxins, toxic-shock toxin,
protein A (inactivates complement and IgG)
 Diseases: Boils, skin sepsis, wound infections, scalded skin
syndrome, catheter-associated disease, foodborne
infection, endocarditis, osteomyelitis, toxic
shock syndrome, pneumonia
 Complications: Multi-drug resistant (MRSA) infections
 Prevention: Handwashing, mupiricin to nares, isolation
Term
Staphylococcus epidermidis

• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
Characteristics: gram positive cocci in clusters
Lab ID: golden colonies, coagulase negative
Transmission: same as S. aureus, opportunistic
Pathogenesis: extracellular slime 2 attach to foreign bodies
Diseases: Device-related sepsis, UTI, sternal wound
osteomyelitis, prosthetic vavle endocarditis,
artificial joint infections
Complications: Multi-drug resistant
Prevention: Handwashing, infection control, remove
devices, monitor for device infections
Term
Staphylococcus saprophyticus


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
Characteristics: same as S. aureus
Lab ID: white colonies, coagulase negative
Transmission: skin and GU mucosa colonizer
Pathogenesis: spread to urinary tract
Diseases: UTI in healthy women (associated w/ intercourse)
Complications: rarely pyelonephritis
Prevention: post-coital urination
Term
Streptococcus pyogenes
(Group A Strep or GAS)


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: Gram positive cocci in chains
 Lab ID: Beta-hemolytic activity on blood agar
 Transmission: Colonizes URT and skin – spread by
droplets and contact
 Pathogenesis: enzymes, exotoxins
 Diseases: URI, SSTI, Scarlet fever
 Complications: necrotizing fasciitis, rheumatic fever,
glomerulonephritis
 Prevention: no vaccine
Term
Streptococcus agalactiae
(Group B Strep)


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram positive cocci in chains
 Lab ID: beta-hemolytic on blood agar, group B antigen +
 Transmission: gut and vaginal colonizer, babies acquire
intra-partum or from nursery
 Pathogenesis: unclear
 Diseases: neonatal sepsis, meningitis
 Prevention: handwashing, screening of pregnant women,
prophylactic antibiotics for children of carriers
Term
Streptococcus: Group C, G, bovis


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
Characteristics: gram positive cocci in chains
Lab ID: Lancefield antigen positive for C, G
Transmission: droplet, translocation (bovis)
Pathogenesis:
Diseases: pharyngitis, bacteremia (rarely)
Complications: S. bovis associated with colon pathology
(most often colon cancer)
Prevention: regular colonoscopy
Term
Viridans group Streptococci


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
Characteristics: gram positive cocci in chains, pairs
Lab ID: alpha-hemolytic, microaerophilic
Transmission: oral streptococci, colonize mouth/teeth
Pathogenesis: n/a
Diseases: endocarditis
Prevention: proper dental care / oral health
Term
Streptococcus pneumoniae


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram positive diplococci
 Lab ID: alpha-hemolytic (incomplete) on blood agar,
encapsulated
 Transmission: colonizes upper respiratory tract, droplet
spread
 Pathogenesis: capsule evades phagocytosis
 Diseases: pneumonia, septicemia, meningitis, otitis media,
sinusitis
 Complications: splenectomy predisposes to systemic
infection, also antigenic-specific strains
are more invasive
 Prevention: vaccination in adults and children,
handwashing
Term
Drugs of Choice
Gram Positive Cocci


 Streptococcus pneumoniae:
 Group A, B, C, G Streptococcus:
 Viridans Streptococcus:
 Staphylococcus spp.:
 Enterococcus spp.:
 Definition
 Streptococcus pneumoniae: penicillin, ampicillin
I – high dose penicillin, 3rd gen. cephalosporin(3GC)
R – vancomycin or linezolid
 Group A, B, C, G Streptococcus: penicillin, ampicillin
 Viridans Streptococcus: Penicillin (+ gentamicin)
 Staphylococcus spp.: nafcillin
R-vancomycin, TMP/SMX, linezolid, or daptomycin
 Enterococcus spp.: ampicillin (+ gentamicin)
R-vancomycin (+ gentamicin), VRE – linezolid or
daptomycin
Term
Corynebacterium diphtheriae


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram-positive, un-encapsulated, non-
motile rods without spores
 Lab ID: black colonies on enriched agar
 Transmission: nasopharynx, occasionally skin (mainly
non-toxigenic strains), aerosol spread
 Pathogenesis: exotoxin-mediated
 Diseases: URI diphtheria, endocarditis, sepsis in non-
toxigenic strains (immunocompromised)
 Complications: 2-3 months as carrier
 Prevention: toxoid vaccination, handwashing
Term
Bacillus cereus


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: large gram-positive rod, spore-former
 Lab ID: special medium req’d
 Transmission: spores on food, toxin/organism causes
disease
 Pathogenesis: toxin-mediated
 Diseases: food poisoning, sepsis in immunocompromised
 Complications: infections usually self-limited
 Prevention:hygienic food preparation and storage
Term
Listeria monocytogenese


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: short gram-positive rods, cocco-bacillary
 Lab ID: motile tumbling movement, hemolytic, cold-
enrichment
 Transmission: survives in cold, food-chain transmission,
cow’s milk, may be normal gut flora, in utero
transmission
 Pathogenesis: can survive in phagocytes, produces
hemolysins and motility protein
 Diseases: meningitis and sepsis in very young and very
old
 Prevention:properly cooked food, avoid soft cheeses,
pate, coleslaw
Term
Clostridium perfringes


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: anaerobic gram positive rods, spore-
forming
 Lab ID: hemolytic, alpha-toxin producing
 Transmission: spores widespread in soil and normal flora,
contact either endogenous or exogenous
 Pathogenesis: up to 12 toxins and tissue-destroying
enzymes, causing necrosis in wounds; food –
large inoculum of vegetative cells ingested
release endotoxin
 Diseases: gas gangrene in ischemic wounds, food
poisoning (toxin-producing strains)
 Prevention: good wound care, proper food preparation
Term
Clostridium tetani


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: gram-positive spore-forming rod with
terminal spore, anaerobic
 Lab ID: find the toxin
 Transmission: soil into wounds by contact, may be major
or minor wound; no person-person spread
 Pathogenesis: neurotoxin (tetanospasmin) in wounds
spreads into bloodstream and to muscles
 Diseases: lockjaw (tetanus), opisthonos, convulsions,
tonic muscle spasms
 Prevention: toxoid vaccine
Term
Clostridium difficle


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: slender gram positive anaerobic rod,
spore-forming and motile
 Lab ID: difficult to culture, toxin assays of feces
 Transmission: gut flora commensal, grows under antibiotic
selective pressure, spread by contact
 Pathogenesis: Toxin-mediated gut wall damage (A and B)
 Diseases: Pseudomembranous colitis (antibiotic-
associated diarrhea)
 Complications: may be rapidly fatal, colectomy
 Prevention: handwashing, isolation, avoid antibiotics! (or
withdraw)
Term
Actinomycetes spp.


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: branching filamentous gram positive rods,
anaerobic, non-spore forming
 Lab ID: israelii species produces sulphur granules in pus
 Transmission: mouth, gut, vagina normal flora –
endogenous infection, no contact spread
 Pathogenesis: unknown
 Diseases: actinomycosis post-local trauma and invasion –
leads to tense, non-tender swellings with draining
sinus tracts
 Complications: may complicate IUD, post-abdominal
surgery; also may be confused with fungal
infection
 Prevention: proper wound and surgical care
Term
Nocardia spp.


• Characteristics
• Lab ID
• Transmission
• Pathogenisis
• Diseases
• Complications
• Preventions
 Definition
 Characteristics: aerobic gram positive rods with thin
branching filaments
 Lab ID: no sulfur granules, weakly acid-fast
 Transmission: widespread in environment, airborne via
soil to wounds or hospital construction
 Pathogenesis: progressively destroys skin, bone, fascia,
and muscle – avoids host defenses, does well in
cell-mediated deficiency states
 Diseases: opportunistic infections, primarily pulmonary,
may form brain and/or kidney abscesses.
 Prevention: isolation, proper HVAC filters/air exchange
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