Microbiology - Gram Neg Bacilli
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MaggieMurphy on June 16, 2011
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Terms | Definitions |
|---|---|
 Vibrio cholerae - Gram stain | Gram-negative bacillus, curved Most pathogens are antigenic groups O1 (or O13) |
| Vibrio cholerae - Location & Transmission | Areas of poor sanitation - Asia (esp India), Africa, South/Central America Usually transmit through contaminated water |
| Vibrio cholerae - Disease / SSX / Progression | Cholera (enterocolitis syndrome - gastroenteritis) (1) ingested in large numbers (2) Incubation period -- few hours to five days (3) Non-invasive organisms localize in small intestine (4) Cholera toxin produced (enterotoxic exotoxin) (a) Stimulates hypersecretion of water and chloride (b) Reverses ion transport in gut (alters intestinal permeability) (c) Causes massive diarrhea -- "rice water stools" -- up to 16L/day - severe dehydration (5) Mortality up to 50% if untreated |
| Vibrio cholerae - Treatment and Control | Treatment and Control (1) good hygiene and disinfection (2) Oral replacement of fluid using electrolyte solution with glucose or sucrose (3) Intravenous infusion of multi-electrolyte sol (4) Antibiotics -- Tetracycline and other broad spectrum antibiotics. Limited to the severely compromised patients (5) Immunization ineffective |
| Vibrio cholerae - Lab Dx | Laboratory diagnosis - Special request for culture needed in the USA due to rarity and need for special media (alkaline and selective) |
| Vibrio genus - Gram Stain | Genus: Gram Neg bacillus, curved |
| Vibrio parahemolyticus - Disease/ Disorder / Location | Gastroenteritis due to the ingestion of contaminated shellfish (esp oysters) --a common in Asian costal regions, lower frequency in US. |
| Vibrio vulnificus - Disease/ Disorder / Location | a. Found in warm, coastal seawater b. Etiologic agent of infrequent, acute infection (fewer than 100 cases per year, but probably underreported) (1) Acute gastroenteritis and primary septicemia due to ingestion of raw or undercooked seafood, particularly raw oysters. (fatality rate 50%) (2) Severe cellulitis due to seawater contaminating a break in the skin -- severe skin/tissue infection with hemorrhagic bullae and necrotizing fasciitis. (fatality rate 15%) |
| Campylobacter jejuni - Gram Stain | Gram Neg bacillus, thin curved rods, occasionally "s"/ gull wing shape |
| Campylobacter jejuni - Transmission/ Origin | Generally originates from food, esp undercooked chicken, raw milk (from cattle feces), and non-chlorinated water |
| Campylobacter jejuni - Incubation/ Sx time | Incubation period: 2-5 days Symptoms usually resolve in 3-6 days |
| Campylobacter jejuni - Disease/ Disorder / SSX | Enterocolitis syndrome / Gastroenteritis (#1-#2 cause in US, w Salmonella) Ulceration of intestinal mucosal epithelium causing diarrhea, abdominal pain, fever, nausea, vomiting (a) Diarrhea varies from watery stools to grossly bloody stools (b) Toxins and invasive enzymes probably involved |
| Campylobacter jejuni - Treatment and Control | Generally no antibiotic treatment, only rehydration and electrolyte replacement. [Erythromycin and tetracyclines- carrier state or in severely compromised pt] |
| Campylobacter jejuni - Lab Dx | Laboratory diagnosis -- Special culture media and environmental conditions needed for culture and biochemical ID (1) Selective plating media with antibiotics (2) Microaerophile -- Incubate in reduced oxygen (about 5%) and increased CO2 (3) Incubation of primary isolation media at 42 C |
| Helicobacter pylori - Gram Stain | Gram Neg bacillus, curved |
| Helicobacter pylori - Disease/ Disorder | Peptic ulcers -- causes chronic inflammatory lesions of the gastric mucus layer |
| Helicobacter pylori - Dx | Diagnostic testing (1) Screen: Breath test to detect urease (urea breakdown) (2) Confirm: Endoscopy and biopsy -- Culture requires microaerophilic environment and special growth media; DNA probe |
| Salmonella Genus - Gram Stain | Gram Neg bacillus |
| Salmonella Genus - Taxonomy / Classification | (1) Family Enterobacteriaceae (2) Two major species: S. typhi and S. enteritidis (3) Over 2200 strains characterized by ―O and H antigens (4) In USA, antigenic groups B and D predominate (40% of 50,000 reported cases/yr) |
| Salmonella Genus - Origin / Transmission | Transmission and Source of infection -- (1) Normal flora of poultry, livestock, rodents,reptile esp turtle (2) Transmitted by contaminated food and water, especially: (a) Meat products not properly cleaned or cooked (b) Eggs and dairy (3) Many bacteria are destroyed by stomach acids, so large quantity needed to infect |
| Salmonella enteritidis - Disease / Disorder and Progression / Timeline | Acute gastroenteritis (enterocolitis syndrome) Pathogenicity i. Bacteria invade the intestinal mucous membranes causing an acute inflammatory reaction in the subepithelial tissue ii. Symptoms incl sudden onset of non-bloody diarrhea and vomiting along with fever about 6 to 48 hours after consumption of contaminated food or water; symptoms persist 2 to 7 days |
| Salmonella enteritidis - Treatment and Control | Treatment and Control — Generally no antibiotic , only rehydration and electrolyte replacement. [Ciprofloxacin, ampicillin, chloramphenicol, or trimethoprim/sulfamethoxazole are used in infants, elderly, and compromised patient.] |
| Salmonella typhi - Disease / Disorder and Progression / Timeline | Typhoid fever i. Bacteria invade epithelial cells of terminal portion of small intestine and then into the lymphoid follicles where they multiply ii. Bacteria migrate to the blood stream, the fever period begins, rose spots appear on skin. Local necrosis can lead to hemorrhage and lesions a.] Fever begins 10-14 days after ingestion of bacteria b.] Headache, myalgia, malaise persist for about 5-10 days c.] Gastrointestinal symptoms begin about 15-20 days after ingestion iii. Localization of bacteria in gallbladder, spleen, liver, and sometimes bones iv. Carrier state (excretion for 3 months) develops in about 5% of patients --Gallbladder |
| Salmonella typhi - Treatment and Control | i. Antibiotics useful -- [Chloramphenicol (14 days), amoxicillin, or ceftriaxone (5 days), or trimethoprim/sulfamethoxazole] ii. Vaccine is only moderately effective |
| Salmonella typhi - Lab Dx | (1) Culture ID with antigenic identification (2) Antimicrobic susceptibility testing needed |
| Shigella Genus - Gram Stain | Gram Neg bacillus, Family Enterobacteriaceae |
| Shigella Genus - 4 Species | (1) S. dysenteriae - Antigenic group A -- Least frequently in U.S. -- more severe dysentery (2) S. flexneri - Antigenic group B -- 25% of Shigella in the U.S. (3) S. boydii - Antigenic group C -- Rare in U.S., only 0.6% (4) S. sonnei - Antigenic group D -- Most frequent isolate (74% of isolates) |
| Shigella Genus - Transmission | (1) Transmitted by fecal-oral route (2) Contaminated food and water (3) Infection by low # bacteria (200) (4) Children under 10 years of age account for over 2/3 of all cases - even more than other oral-fecal bacterial infections |
| Shigella Genus - Disease/ Disorder / SSX / Progresssion | Shigellosis Dysentery --enterocolitis syndrome "bacillary dysentery" Symptoms: Diarrhea, lesions in the colon producing pus and blood in feces (dysentery), and fever Incubation: 12-48 hours depending on dose of microbes (10-100 bacteria) with symptoms lasting 1-3 days Disease progression (a) Organisms attach to & penetrate intestinal mucosal epithelial cells (b) Bacteria multiply intracellularly causing mucosal epithelial cells to die and slough off with some bleeding (c) Bacteria release an endotoxin that stimulates fever and an inflammatory response causing local damage (ulcerations, pus, and bleeding) (d) Exotoxin causes fluid loss (diarrhea) |
| Shigella Genus - Virulence Factors | Toxin production (a) Endotoxin - potent and is present in all strains (b) Exotoxin i.Neurotoxin and enterotoxin produced by S. dysenteriae type I ii. Some strains of S. flexneri produce enterotoxins |
| Shigella Genus - Treatment and Control | Rehydration and electrolyte replacement is accompanied by treatment with antimicrobics such as ciprofloxacin, ampicillin, trimethoprim/sulfamethasoxazole |
| Shigella Genus - Lab Dx | Laboratory diagnosis (1) Culture ID and ―O antigenic group designation (2) Antimicrobic susceptibility test needed |
| Escherichia coli - "esh-er-ee-sha" - Gram Stain | Gr-Neg bacillus, member of Enterobacteriaceae Taxonomy based on O and H antigen combinations. Very easily grown in labratory. |
| Escherichia coli - Normally found | Normal flora of intestinal tract; a Coliform (therefore not regularly checked for in US lab) Primary antigenic type: O157:H7, 80% |
| Escherichia coli - Disease / Disorders | 1. UTI / Cystitis - 75-85%, female pt, an anatomical issue, short urethra. Flank pain, dysuria, fever. 2. Enterotoxic E.coli (ETEC) - cause Traveler's Diarrhea, cholera-like enterotoxin. SSX cramps, fever, dehydration, diarrhea w/o boold or mucus. 3. Enterohemorrhagic E.coli (EHEC)- Hemorrhagic colitis. Invasive. Shiga Toxin (ST) / (shigellla-like). Many types. Watery AND bloody diarrhea / inflammation. No fever. Progress to Hemolytic Uremic Syndrome (HUS) w/ hemorrhage of kidney tissue |
| Pseudomonas aeruginosa - Gr Stain and Virulence Factors | Gr-Neg bacillus. Protein inhibitors, exotoxins, capsule (CF strains). (Naturally) resistant to most antibiotics. |
| Pseudomonas aeruginosa - D/D | -Nosocomial infections (abt 10%); debilitated/compromised patients. -Infrequently- wound infec and UTI -Mucoid strains- repeatedly colonize respiratory tract of cystic fibrosis pts (thick capsule) |
| Pseudomonas aeruginosa (compared to) Acinetobacter baumannii | Both Gr-Neg bacillis. Both Can be nosocomial infections. Both known for very HIGH antibiotic resistance. -Pseudomonas aeruginosa- esp cystic fibrosis pt -Acinetobacter baumannii- esp traumatic would pt / wounded soldiers, opportunistic |
| Acinetobacter baumannii - D/D | From soil/water. Opportunistic. Post-traumatic wound abscess & septicemia - VietNam, Iraq, Afghan. Wounded soldiers. Natural & Nosocomial VERY HIGH antibiotic resistance. ~35% susceptible to 1 only, ~4% resistant to ALL |
| Yersinia pestis - D/D, Transmission | Biological threat agent! - Bubonic & Pneumonic Plague, all over world Transmit by fleas or direct contact w animal |
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