Micro - Clinical Bacteriology (Gram - Rods & Comma-Shaped) Flashcards
Pg. 135-137 Sections include: Legionella pneumophila Pseudomonas aeruginosa E. coli Klebsiella Salmonella vs. Shigella Campylobacter jejuni Vibrio cholerae Yersinia enterocolitica Helicobacter pylori
What are the main 2 conditions caused by Legionella pneumophila? What are the signs/symptoms associated with each condition?
(1) Legionnaires’ disease = severe pneumonia, fever, GI, and CNS symptoms (2) Pontiac fever = mild flu-like syndrome
What bacteria causes Legionnaires’ disease? What are the symptoms of Legionnaires’ disease?
Legionella pneumophila; Severe pneumonia, fever, GI, and CNS symptoms
What bacteria causes Pontiac fever? What are the symptoms of Pontiac fever?
Legionella pneumophila; Mild flu-like syndrome
What kind of bacteria is Legionella pneumophila?
Gram-negative rod
What is important to know about the staining of Legionella pneumophila?
Gram stains poorly (negative) - use silver stain
On what type of media does Legionella pneumophila grow?
Grow on charcoal yeast extract culture with iron and cysteine
How is Legionella pneumophila detected clinically?
Presence of antigen in urine
How is Legionella pneumophila transmitted, and from where? How is it not transmitted?
Aerosol transmission from environmental water source habitat; No person-to-person transmission
What is the treatment for Legionella pneumophila?
Macrolide or quinolone
What lab finding (chem-7) is in patients with Legionella pneumophila?
Hyponatremia
With what kind of infections is Pseudomonas aeruginosa associated?
Wound and burn infections
What 7 conditions does Pseudomonas aeruginosa cause?
(1) Pneumonia (espcially in cystic fibrosis) (2) Sepsis (black lesions on skin) (3) External otitis (swimmer’s ears) (4) UTI (5) Drug and DiabetesOsteomyelitis… plus hot tub folliculitis; (6) Malignant otitis externa in diabetics. (7) Ecthyma gangrenosum—rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia. Think: “PSEUDOmonas (plus just remember hot tub folliculitis)”
What kind of bacteria are Pseudomonas aeruginosa? Think in terms of both metabolic and gram-stain classifications.
Aerobic, non-lactose fermenting, oxidase positive, gram-negative rod
What kind of pigment and odor do Pseudomonas aeruginosa make?
Pyocyanin (blue-green) pigment; grape-like odor
What condition(s) can Pseudomonas aeruginosa cause in diabetics?
Diabetic osteomyelitis & malignant otitis externa
What is often a source of Pseudomonas aeruginosa?
Water
What toxins do Pseudomonas aeruginosa make, and what are their effects?
(1) Endotoxin (fever, shock) (2) Exotoxin A (inactivates EF-2)
How is Pseudomonas aeruginosa treated?
Beta-lactam (e.g., piperacillin, ticarcillin, cefepime, imipenem, meropenem) +/- aminoglycoside. Ciprofloxacin if UTI.
What effect does Pseudomonas aeruginosa commonly have on cystic fibrosis patients, and with what is this effect associated?
Chronic pneumonia, associated with biofilm
What are the E. coli virulence factors? With what conditions/diseases is each associated?
(1) Fimbriae - cystitis and pyelonephritis (2) K capsule - pneumonia, neonatal meningitis (3) LPS endotoxin - septic shock
What are the strains of E. coli?
(1) EIEC (Enteroinvasive) (2) ETEC (Enterotoxigenic) (3) EPEC (Enteropathogenic) (4) EHEC (Enterohemorrhagic)
What is the mechanism of EIEC? What is its presentation?
Microbe invades intestinal mucosa & causes necrosis & inflammation; Clinical manifestations similar to Shigella; Invasive, dysentery; Think: “I is for Invasive”
To what other bacteria does EIEC present similarly?
Shigella
What is the toxin/mechanism of ETEC? What is its presentation?
Labile toxin/stable toxin. No inflammation or invasion; Traveler’s diarrhea (watery); Think: “T is for Traveler’s diarrhea”
What is the toxin/mechanism of EPEC? What is its presentation?
No toxin produced. Adheres to apical surface, flattens villi, prevents absorption; Diarrhea usually in children (Pediatrics); “Think: P is for Pediatrics”
What is the toxin/mechanism of EHEC? What is its presentation?
Shiga-like toxin cause hemolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure); Microthrombi form on endothelium damaged by toxin => mechanical hemolysis (schistocytes formed) and decreased renal blood flow; microthrombi consume platelets => thrombocytopenia. Dysentery (toxin alone causes necrosis and inflammation); Think: “H is for Hemolytic-uremic syndrome”
What distinguishes EHEC from other E. Coli?
Does not ferment sorbitol
What syndrome is caused by EHEC? With what symptoms is it associated?
Hemolytic-uremic syndrome; Triad of anemia, thrombocytopenia, & acute renal failure
What is the most common serotype of EHEC?
O157:H7
Where is Klebsiella normally found?
Intestinal flora
How do Klebsiella colonies appear, and why?
Very mucoid colonies caused by abundant polysaccharide capsule
What is a clinically relevant sign of Klebsiella?
Red “currant jelly” sputum
What major disease does Klebisella cause, in what populations, and under what circumstances?
Causes lobar pneumonia in alcoholics and diabetics when aspirated; Think: “4 A’s: (1) Aspiration pneumonia (2) Abscess in lungs and liver (3) Alcoholics (4) di-A-betics”
Besides lobar pneumonia in alcoholics and diabetics, what other category of disease/condition is associated with Klebsiella?
Also cause of nosocomial UTIs
Compare/Contrast Salmonella and Shigella in terms of motility.
SALMONELLA - have flagella; SHIGELLA - no flagella; Think: “SALMONella swim”
What is the method of dissemination (once inside the body) for Salmonella versus Shigella?
SALMONELLA - can disseminate hematogenously; SHIGELLA - cell to cell transmission, no hematogenous spread
What is the reservoir for Salmonella versus Shigella?
SALMONELLA - have many animal reservoirs ; SHIGELLA - only reservoirs are humans and primates
Do Salmonella and/or Shigella produce hydrogen sulfide?
SALMONELLA - Produce hydrogen sulfide; SHIGELLA - NOT produce hydrogen sulfide
What effects do antibiotics have on Salmonella versus Shigella?
SALMONELLA - Antibiotics may prolong fecal excretion of organism; SHIGELLA - Antibiotics shorten the duration of fecal excretion of organism
What is the response caused by Salmonella versus Shigella upon affecting the human body?
SALMONELLA - Invades intestinal mucosa & causes a monocytic response; SHIGELLA - Invades intestinal mucosa & causes PMN infiltration
Compare/Contrast the possibility/likelihood of Salmonella versus Shigella causing blood diarrhea.
SALMONELLA - can cause bloody diarrhea; SHIGELLA - OFTEN causes bloody diarrhea
Do Salmonella and/or Shigella ferment lactose?
Neither ferments lactose
What causes typhoid fever? What characterizes it?
Salmonella typhi; Rose spots on abdomen, fever, headache, and diarrhea
In what reservoir is Salmonella typhi found?
Only in humans
What is important to know about the potential for latency/dormancy in Salmonella typhi infections?
Can remain in gallbladder and cause a carrier state
Of what condition is Camplyobacter jejuni a major cause, and in what population?
Major cause of bloody diarrhea, especially in children
How is Campylobacter jejuni transmitted?
Fecal-oral transmission through foods such as poultry, meat, unpasteurized milk.
What are important things to know about Campylobacter jejuni in order to classify/identify it?
Gram-negative, comma or S-shaped, oxidase positive, grows at 42C
To what conditions is Campylobacter jejuni a common antecedent?
(1) Guillian-Barre syndrome (2) Reactive arthritis
What are important things to know about Vibrio cholerae in order to classify/identify it?
Gram-negative, comma shaped, oxidase positive, grows in alkaline media
In general, where is Vibrio cholerae endemic?
Developing countries
What major symptom does Vibrio cholerae produce, and how?
Produces profuse rise-water diarrhea, via Toxin that permanently activates Gs, increasing cAMP
What is the necessary response to Vibrio cholerae infection?
Prompt oral rehydration is necessary
How is Yersinia entercolitica usually transmitted?
Usually transmitted from pet feces (e.g., puppies), contaminated milk, or pork
What condition does Yersinia enterocolitica cause? What other condition(s) does this condition mimic?
Causes mesenteric adenitis, that can mimic Crohn’s or appendicitis
What condition(s) does Helicobacter pylori cause?
Helicobacter pylori - causes gastritis and peptic ulcers (especially duodenal)
For what 3 condition(s) is Helicobacter pylori a risk factor?
(1) Peptic ulcer (2) Gastric adenocarcinoma (3) Gastric Lymphoma
What are the gram stain, morphology, and metabolic characteristics of Helicobacter pylori? Which of these is most clinically relevant, and why?
Curved gram-negative rod that is catalase, oxidase, and urease (+) (can use urea breath test or fecal antigen test for diagnosis)
What kind of environment does Helicobacter pylori create?
Creates alkaline environment
What is the most common initial treatment for Helicobacter pylori?
Triple therapy: (1) Proton pump inhibitor (2) Clarithromycin (3) Amoxicillin or Metronidazole
What bacteria causes ecthyma gangrenosum? What characterizes it? In what patient population is it seen?
Ecthyma gangrenosum—rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia.
What is another name for EHEC bacteria?
Enterohemorrhagic E. coli (EHEC) = Also called STEC (Shiga toxin-producing E. coli)
How is H. pylori diagnosed?
Can use urea breath test or fecal antigen test for diagnosis
