Low G+C Gram Positive Bacteria

Low G+C Gram Positive Bacteria

1. coccus

   • staphylococcus
     • nonmotile, facultative anaerobe, grapelike clusters, salt tolerant, tolerant of dessication, catalase positive
     • staph. aureus
       • more virulent strain
       • coagulase positive
     • staph. epidermidis
       • normal skin microbiota
     • antiphagocytic factors: protein A coat
       • binds to IgG antibodies
       • inhibits opsonization (enhanced phagocytosis)
     • enzymes: bound coagulase, cell free coagulase, slime layer capsule, hyaluronidase, staphylokinase, lipase, beta-lactamas
     • toxins: cytolytic toxin, exfoliative toxin, toxic shock syndrome toxin, enterotoxins
     • noninvasive disease: food poisoning
       • from enterotoxin contaminated food
       • symptoms: nausea, severe vomiting, diarrhea, headache, sweating, abdominal pain
     • cutaneous disease: staphylococcal scalded skin syndrome, impetigo, folliculitis, furuncle, carbuncle
       • symptoms: reddening, blisters, epidermis peels off in sheets, red patches, puss filled vesicle, base of hair folicle becomes red, swollen, pus filled
     • systemic disease: toxic shock syndrome, bacterermia, endocarditis, pneumonia, empyema, osteomyelitis
       • symptoms: fever, vomiting, red rash, extremely low BP, loss of sheets of skin
     • treatment: penicillin for 5%, methicillin, vancomycin for MRSA,
   • streptococcus
     • pairs or chains, catalase negative, facultative anaerobes
     • Group A: strep. pyogenes
       • beta-hemolytic
       • protein M
         • interferes with opsonization and lysis
       • hyaluronic acid capsule
         • found in human body, hides from white blood cells
       • enzymes: streptokinase, deoxyribonuclease, C5a peptidase, hyaluronidase
       • pyrogenic toxins
         • stimulate release of cytokines that cause fever, cause blood vessels near surface to dilate, carried on temperate bacteriophages
       • streptolysins
         • lyse RBC, WBC, platelets
       • diseases: pharyngitis, scarlet fever, pyoderma, erysipelas, streptococcal toxic shock syndrome, necrotizing fasciitis, rheumatic fever, glomerulonephritis
       • treatment: penicillin, erythromycin, cephalosporin, bacitracin
     • Group B: strep. agalactiae
       • beta-hemolytic
       • resistant to bacitracin
       • enzymes: proteases, hemolysins, deoxyribonuclease, hyaluronidase
       • diseases: puerperal fever, neonatal bacteremia, meningitis, pneumonia
       • treament: penicillin G
     • strep. viridans
       • alpha-hemolytic
       • diseases: dental caries, meningitis, endocarditis
       • dextran
         • produced from glucose
         • helps to stick to dental surfaces and colonize enamel
     • strep. pneumoniae
       • microbiota of pharynx
       • polysaccharide capsule required for virulence
       • phosphorylcholine, protein adhesin
       • secretory IgA protease
         • destroys IgA, which protects mucosal membranes
       • pneumolysin
         • binds to cholesterol producing pores through membranes of ciliated epithelial cells
       • diseases: pneumococcal pneumonia, sinusitis, otitis media, bacteremia, endocarditis, pneumococcal meningitis
       • alpha-hemolitic
       • Quellung reaction
         • anticapsular antibodies cause capsule to swell
         • diagnostic
       • treatment: penicillin, cephalosporin, erythromycin, chloramphenicol
   • enterococcus
     • unencapsulated, catalast negative, non-hemolytic, tolerate bile salt, higher temp and pH
     • E. faecalis
       • ubiquitous in colon
       • bacteriocins
         • chemicals that inhibit growth of other bacteria
     • E. faecium
     • can cause serious disease if introduced into other parts of body
     • diseases: bacteremia, endocarditis, wound infections, 10% nosocomial infections
     • treatment: difficult because resistant

2. bacillus

   • endospore forming
     • bacilllus anthracis
       • facultative anaerobe, polyglutamic acid capsule, nonmotile
       • contraction via: inhalation of endospores, inoculation of endospores through break in skin, ingestion of endospores
       • clinical manifestations: gastrointestinal, cutaneous, inhalation
         • symptoms: intestinal hemorrhaging, eschar, fatigue, malaise, fever, aches, cough
       • treatment: penicillin, erythromycin, chloramphenicol
       • toxins: edema factor, protective antigen, lethal factor
     • clostridium
       • anaerobic
       • c. perfringens
         • diseases: food poisoning, gas gangrene
           • symptoms: abdominal cramps, watery diarrhea, intense pain at site of infection, tissue and muscle death, production of foul smelling gaseous waste product, shock, kidney failure, death
         • nonmotile, noninvasive
         • treatment: self limiting, amputation
       • c. difficle
         • because of prolonged antibiotics
         • motile
         • disease: pseudomembranous colitis
           • large sections of colon slough off, massive internal infection by fecal bacteria
         • treatment: discontinuation of antimicrobial drug, oral vancomycin, metronidazole
         • toxins: A and B
       • c. botulinism
         • prevents muscle contraction by preventing secretion of neurotransmitter into synaptic cleft
           • flaccid paralysis
         • clinical manifestations: foodborne, infant, wound
           • symptoms: blurred vision, dizzy, dry mouth, dilated pupils, constipation, abdominal pain, asphyxiation, failure to thrive
       • c. tetani
         • motile, terminal endospore, obligate anaerobe
         • disease: tetanus
           • symptoms: lockjaw, sweating, drooling, grouchiness, constant back spasms
         • toxin: tetanospasmin
           • muscles signaled to contract simultaneously
         • treatment: immunoglobulin, vaccine
   • non-endospore forming
     • listeria monocytogenes
       • facultative intracellular parasite, tumbling motility
       • listeriolysin O
         • punctures phagosome membrane, releasing bacterium into host
       • polymerizes host's actin into tail that pushes bacterium into pseudopod that is endocytized by new host
       • diseases: meningitis, premature delivery, miscarriage, stillbirth
       • treatment: penicillin and erythromycin
     • mycoplasmas
       • no cytochromes, cell wall
       • m. pneumoniae
         • kills epithelial cells causing buildup of mucous
         • disease: primary atypical pneumonia
         • treatment: macrolides
         • spread by nasal secretions
       • m. genitalium, ureaplasma urealyticum
         • disease: nongonococcal urethritis
       • m. hominis
         • disease: pelvic inflammatory disease