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24 Cards in this Set
- Front
- Back
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3 Types of Gram-Negative Rods |
The Enteric Bacteria (Enterobacteriaceae) The Nonfermenters The Unusual Gram-Negative Bacilli (UBs) |
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1. Enterobacteriaceae |
~120 species, all closely related Straight rods 80-95% of all isolates from a clinical setting will be Escherichia coli, Klebsiella pneumoniae or Proteus mirabilis >99% of clinical isolates will belong to only 23 species |
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Enterobacteriaceae Four Cardinal Characteristics |
1. Ferment glucose 2. Reduce nitrates to nitrites 3. Cytochrome oxidase negative 4. Flagella, if present, are peritrichous |
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Enterobacteriaceae Cont'd |
Normal flora of mouth, oropharynx, genitalia, distal urethra and especially the large bowel Soil or water Can be opportunistic Urinary tract infections, wound infections, pneumonia, meningitis (especially in the neonate and post-neurosurgery) and sepsis Only shared determinant of pathogenicity is lipopolysaccharide (LPS) |
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Escherichia coli |
Three Groups: Commensals, enteric pathogens, and extraintestinal infections Most common cause of UTIs Strains are type using three antigens: - O antigen (LPS) - K antigen (capsule) |
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Enterotoxigenic E. coli (ETEC) |
Major cause of traveler's diarrhea Three toxins: LT, STa, STb |
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Enteroinvasive E. coli |
When the bowel wall gets invaded Bloody diarrhea, fever |
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Verotoxigenic (Enterohemorrhagic) E. coli (VTEC, EHEC) |
Undercooked hamburger, unpasteurized milk, water Bloody diarrhea, hemolytic uremic syndrome most common in children <5 Antibiotics contraindicated - If treated with antibiotics, hemolytic complications and renal failure could follow |
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Salmonella Enterica ssp. Enterica |
~2500 serotypes Food (esp. poultry, eggs), water, pet turtles, African dwarf frogs Diarrhea, extraintestinal disease Antibiotics contraindicated - If given antibiotics, patient will take longer to recover, no hemolytic activity |
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Salmonella Enterica ssp. Enterica Serovar. Typhi |
Food & water contaminated with human waste Duration of illness: 3-5 weeks Enteric fever, headache, prostration, rose spots, initial constipation, later diarrhea Diagnosis by isolation from blood, later from stools Antibiotics indicated |
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Shigella Species |
Nonmotile Food & water, very low inoculum (<200 bacteria) to cause infection Bloody diarrhea, fever, cramps, dysentery Four serotypes |
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Yersinia Enterocolitica |
Pork, cold cuts, water Diarrhea Pseudoappendicitis - something that mimics appendicitis |
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Yersinia Pestic |
Plague - "The Black Death" Bubonic and pneumonic forms Fleas from rats Carried by ground squirrels in the SW USA |
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Klebsiella Pneumoniae |
Nonmotile Pneumonia, particularly in alcoholics, the debilitated and the hospitalized Also causes UTIs, sepsis |
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Serratia Marcescens |
A leading cause of nosocomial infections Tends to be very resistant to antibiotics Some strains produce a blood red pigment - can grow on bread and damp places (toilet) Transubstantiation - in Biblical times, the bread turned red, they wiped it away, and it came back. - People saw this as the blood of Christ coming back |
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2. Nonfermenters |
~ 15% of aerobic Gram-negative isolates from clinical specimens Easily distinguished from enterobacteriaseae by their failure to acidify the butt of KIA or TSI - In a TSI test result, a nonfermenter should be red Difficult to identify often requiring long sets of biochemical tests Hard to treat, very antibiotic resistant Require longer courses of antibiotics then fermentative bacteria |
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Pseudomonas Aeruginosa |
Widely distributed in moist natural environments
Minimal nutritional requirements (Think water)
Encapsulated: outside of their cell wall, they have a polysaccharide or sugar layer that adds protection
Polar flagella
Numermous toxins and extracellular virulence factors
Capable of producing biofilms - Green projections that help them stick to eachother and surfaces |
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Pseudomonas Aeruginosa Cont'd |
Cytochrome oxidase positive Distinctive colonial morphology and characteristic grapelike odour Unique blue pyocyanin pigment which is detected on special medium. Colonies usually green due to pyocyanin plus yellow pyoverdin |
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Pseudomonas Aeruginosa Cont'd |
More commonly found isolated than all other NFB combined Can contaminate "sterile" solutions and even disinfectants Infections mainly nosocomial Highly antibiotic resistant |
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Pseudomonas Aeruginosa Nosocomial Infections |
Very invasive --> blood vessel walls --> vessel wall necrosis Pneumonia UTIs, surgical wound infections, infections of burns Skin & soft tissue gangrene |
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Pseudomonas Aeruginosa Community Acquired Infections |
Malignant otitis externa (glue ear) in diabetics Hot tub folliculitis Endocarditis in IV drug abusers Osteomyelitis of calcaneum after penetrating injury |
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Acinetobacter species |
Can contaminate "sterile" solutions and even disinfectants Nosocomial outbreaks |
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Stenotrophomonas |
Tends to be isolated from patients on broad spectrum antimicrobials, especially carbapenems Unless isolated from a sterile site, clinical significance is doubtful |
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Burkoldaria Cepacia |
Respiratory infections in cystic fibrosis patients CF camps for children discontinued because of B. cepacia cross infection It's a complex, not just a singular bacterial species |
