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35 Cards in this Set

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Clostridium spp.
Basic characteristics
- Anaerobic, gram positive rod, "boxcar-shaped"
- Spore-former can survive hostile environments
- Soil - natural habitat
- Most rapidly growing organism (every 12 minutes)
Clostridium dificile
Basic Characteristics
- Disease: nosocomial diarrhea -> pseudomembranous colitis
- Predisposing factor = antimicrobial therapy
-Pathogenesis:
Toxin A - enterotoxin, more important
Toxin B - cytotoxin
- Treatment: metronidazole p.o.
Clostridium dificile
Characteristics of Disease
- Organism is obtained from hospital environment
- Gut flora is altered by antimicrobial therapy
- Alteration in gut flora reduces its capacity to inhibit the growth of C. difficile
- C. dificile grows and produces toxins in gut
- Toxin mediates diarrhea and more severe manifestations such as non-specific and pseudomembranous colitis
Clostridium perfringens
Basic Characteristics
- Disease: gas gangrene, food poisoning
- Normal bowel flora
- Predisposing factor = traumatic wound, post-surgery
- Virulence: histotoxic
- Treatment: debridement (amputation), leave wound open to air, Pen G
Clostridium perfringens
Characteristics of Disease
- Inoculation of tissue during trauma
- Tissue damage restricts blood flow and oxygenation of tissue
- Organism either germinates from spores introduced into wound or vegetative organisms begin to grow in tissue
- Very rapid growing organism
- Gas is a metabolic by-product
- Produces proteolytic and other toxins that degrade tissue
- There is no pus b/c WBC’s recruited by immune response are quickly degraded
Clostridium botulinum
- Disease – flaccid paralysis leading to respiratory arrest
- Three forms of disease:
- Infant botulism - most common, honey/dirt ingestion, constipation, poor feeding, consume organism
- Food-borne botulism - improperly canned vegetables, soups, fish (home-canned), consume toxins
- Wound botulism organism in wound
- Inhalational – a bioterrorism agent
- Pathogenesis: neurotoxin - blocks Ach release -> flaccid paralysis -> difficulty swallowing, talking, suckling -> death by respiratory arrest
- Tx: respiratory support plus antitoxin (from CDC)
Clostridium tetani
- Disease: tetanus
- Predisposing factor: trauma, usually stepping on nail
- Virulence: neurotoxin that blocks inhibition -> spastic paralysis -> lockjaw or "trismus" -> respiratory failure
- Treatment: antitoxin, vaccine, respiratory support, pen G or metronzidazole
D cycloserine
- A D-Ala analogue=
- inhibits L-Ala racemase D-Ala and also D-Ala synthetase D-Ala-D-Ala
Vancomycin
- binds D-Ala-D-Ala precursor blocking polymerization
- Also injures cytoplasmic membrane
Bacitracin
- blocks regeneration of C55-isoprenol phosphate carrier.
β-lactams (penicillins, cephalosporins)
- block transpeptidation in crosslinking side chains
- Sonly formed by growing cells, so only act on growing cells - may be sufficient to "kill" some organisms
Aminoglycosides
- streptomycin, kanamycin, gentamicin, tobramycin
- bind to 30S subunit -> misreading of code, release of ribosome from mRNA
- irreversible, cidal
Tetracyclines
- act on 30S ribosome, inhibit aa-t-RNA binding to A site
- static, reversible
Macrolides
- erythromycin, clindamycin clarithromycin, azithromycin
- act on 50S ribosome, block transfer and translocation
- static, reversible
Oxazolidinones
- Linezolide - for resistant enterococcal and staph
- only against gram positives
- binds to 23S RNA on 50S, so no 70S
- static for staphy and enterococci,
- cidal for strep
Sulfonamides
- antibacterials - dye derivs, not microbial products
- Inhibition (PABA) into FA b/c they are structural analogues of PABA
Trimethoprim
inhibits DHT to THF
Rifamycins
- aromatic ring w/ long aliphatic bridge
- Rifampin binds to β subunit of RNA poly, no transcription
- high rates of mutation of target site is a problem
Quinolones
- interfere with gyrase α, reformation of phosphodiester bond (rejoining DNA after ds cleavage by gyrase)
Novobiocin
- blocks binding of ATP to gyrase/DNA complex, interfering with gyrase β - decreased DNA supercoiling
Peptostreptococcus
- Gram positive cocci, anaerobe
- microflora in oropharynx and intestinal tract
Actinomyces
- Gram positive non-spore- forming rods - anaerobes
- oropharynx - some microaerophilic
- resistant to metronidazole
Lactobacillus
- Gram positive non-spore- forming rods - anaerobes
- female genital tract
- vancomycin resistant
Propionibacterium
- Gram positive non-spore- forming rods - anaerobes
- microflora of skin
- common contaminant of CSF and blood cultures
bacteriods
- Gram negative rods, anaerobes
- oropharynx and GI
- in female genital tract - the most common isolated in human infections - most produce beta-lactamse
- treated with a beta-lactam /beta lactamase inhibitor such as the combination of ampicillin and sulbactam or metronidazole.
Porphyromonas
- Gram negative rods - anaerobes
Prevotella
- Gram negative rods - anaerobes
Fusobacterium
- Gram negative rods - anaerobes
Brain abscess
Prevotella, Porphyromonas, and Peptostreptococcus
Device related meningitis
Propionibacterium
Deep fascial space infections
Bacteroides, Prevotella, Porphyromonas, Peptostreptococcus, and Fusobacterium
Lung abscess
Bacteroides, Prevotella, Porphyromonas, Fusobacterium, and Peptostreptococcus
Peritonitis
Bacteroides fragilis
Escherichia coli
Peptostreptococcus
Prevotella
Female genital tract infections
Peptostreptococcus, Prevotella, and Porphyromonas
B. fragilis if abscess
Foot infections
Bacteroides and Peptostreptococcus