Gram Negative Bugs Flashcards
HaEMOPhilus Causes
Epiglottitis (cherry red in children), Meningitis, Otitis Media (Nontypeable strains), and Pneumonia
Most invasive disease caused by capsular type B, it is a small gram-neg (coccobacillary) rod that produces IgA protease and is transmitted by aerosols.
Haemophilus Influenza
What type of agar do you culture H. Flu on?
- Chocolate agar with factors V(NAD+) and X (hematin).
- Can also be grown with Staph Aureus which will lyse the cells giving H. flu access to V and X.
H. Flu vaccine contains what?
Type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to dphtheria toxoid or other protein.
Treat meningitis with? Give what as prophylaxis to close contacts?
Treat with ceftriaxone and give Rifampin to close contacts.
Pt presents as a child that has to hunch over in order to breathe and drools like a zombie, what do they have and what is the cause?
Epiglottitis and most often Strep Pneumo but if the kid is not vaccinated then it would be H. Flu.
Gram neg diplococci that ferments glucose, produces IgA proteases and is Oxidase Positive.
Neisseria (Gonococci and Meningococci)
What does N. Meningococci Ferment?
Maltose and Glucose
What does N. Gonococci Ferment?
Glucose
What’s so special about N. Meningococci?
- Polysaccharide capsule
- Maltose fermentation
- Vaccine (none for type B)
- Respiratory and Oral Secretions.
- Causes meningococcemia, meningitis, and Waterhouse-Friderichsen syndrome.
What’s so special about N. Gonococci?
- No capsule, no maltose fermentation, No vaccine (due to antigenic variation)
- Sexually Transmitted
- Causes gonorrhea, septic arthritis, neonatal conjuntivitis, PID, and Fitz-Hugh-Curtis Syndrome.
- Presents with Severe Pneumonia, Fever, GI issues (diarrhea), and CNS symptoms (Mental Confusion)
- Typically in smokers >55 yrs with high alcohol intake or in immunosuppressed.
- Legionnaires’ Disease (Legionella Pneumophila)
- Think of a French Legionnaire with his silver helmet, sitting around a campfire (charcoal) with his iron dagger - he is no sissy (cysteine).
Mild flu-like syndrome with no fatalities. Related to Legionnaires’.
Pontiac Fever
- Gram neg rod that stains poorly, use a silver stain.
- Transmitted by Aerosol WATER DROPLETS FROM ENVIRONMENTAL WATER SOURCE HABITAT. (Could come from a lake, river, shower, drinking fountain, misters at the store, etc).
- NO PERSON TO PERSON SPREAD.
Legionella Pneumophila (Legionnaires’ Disease)
- Grows on charcoal yeast extract with iron and cysteine.
- Diagnosed by presence of antigen in urine.
- Facultative Intracellular = Granulomas.
- Treat with macrolide or quinolone.
Legionnaires’ Disease
- Associated with wound/burn infections, Pneumonia (especially in cystic fibrosis), sepsis (black lesions on skin), External Otitis (swimmer’s ear), UTI, Drug use, Diabetic Osteomyelitis, and hot tub folliculitis (healthy pts)
- Also Malignant otitis externa in diabetics, eye ulcers from prolonged contact lens wear, and erythema gangrenosum.
Pseudomonas Aeruginosa
Aerobic, encapsulated gram-neg rod, non-lactose fermenting, oxidase positive (granulomas), and produces pyocyanin (blue-green) pigment that has a grape-like odor.
Pseudomonas Aeruginosa
- Produces endotoxin (fever, shock) and exotoxin A (ribosylates EF-2 to inactivate it)
Pseudomonas Aeruginosa
Treat Pseudomonas Aeruginosa with….
Aminoglycoside with extended spectrum penicillin (piperacillin/ticarcillin)
Virulence Factors:
- Fibriae: cystitis and pyelonephritis
- K capsule: pneumonia, neonatal meningitis
- LPS endotoxin: septic shock
E. coli
- Mech: Invades intestinal mucosa and causes necrosis and inflammation (clinically like Shigella) but NO toxin produced.
- Presents as Invasive, dysentery
EIEC
Mech: Labile toxin/stable toxin. No inflammation or invasion.
- Presents as Traveler’s diarrhea (watery)
ETEC
Mech: No toxin produced. Adheres to apical surface, flattens villi, prevents absorption.
- Presents as diarrhea usually in children.
EPEC
Mech: Produces Shiga-like toxin and Hemolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure).
- Endothelium swells and narrows lumen, leading to mechanical hemolysis and reduced renal blood flow; damaged endothelium consumes platelets.
EHEC
Most common serotype of EHEC
O157:H7
Presents as Dysentery (toxin alone causes necrosis and inflammation).
- Does not ferment sorbitol (distinguishes it from other E. coli.
EHEC
- Intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated.
- Very mucoid colonies caused by abundant polysaccharide capsule –> Red “currant” jelly sputum.
- Also cause of nosocomial infections.
Klebsiella
4 A’s of Klebsiella
- Aspiration pneumonia
- Abscess in lungs and liver
- Alcoholics
- di-A-betics
- No flagella, cell to cell transmission with NO heme spread.
- Humans and primates are only reservoirs.
- Does NOT produce hydrogen sulfide and Antibiotics prolong excretion in feces.
Shigella
- Has flagella, can disseminate hematogenously, and has many animal reservoirs.
- Produces hydrogen sulfide and antibiotics may prolong symptoms.
Salmonella
- Invades intestinal mucosa and causes a monocytic response –> can cause bloody diarrhea.
- No lactose fermenting.
Salmonella
- Invades intestinal mucosa and causes PMN infiltration –> OFTEN causes bloody diarrhea but does not ferment lactose.
Shigella
- Found only in humans, characterized by rose spots on abs, fever, headache, and diarrhea.
- Can remain in gallbladder and cause a carrier state.
Salmonella Typhi (Typhoid Fever!)
- Major cause of bloody diarrhea, esp in children.
- Fecal/oral through foods like poultry, meat, unpasteurized milk.
Campylobacter Jejuni
Comma or S-shaped, oxidase positive, grows at 42 degrees C and is common antecedent to Guillain-Barre syndrome and reactive arthritis.
Campylobacter Jejuni (Campylobacter likes the hot CAMPfire)
- Produces profuse rice-water diarrhea via toxin that permanently activates Gs, increases cAMP.
- Comma shaped, oxidase pos, grows in alkaline media. Endemic to developing countries.
- Prompt oral rehydration necessary.
Vibrio Cholera
- Usually transmitted from pet feces, contaminated milk, or pork. Causes mesenteric adenines that can mimi Crohn’s or appendicitis.
- Gram neg w/ toxins called Yops.
Yersinia Enterocolitica
- Transmitted by rodents by aerosols or flea bites.
- Gram neg causes Buboes: massive lymph node enlargement, pneumonia and sepsis.
Yersinia Pestis (Black Plague)
- Curved, gram neg rod that causes gastritis and up to 90% of duodenal ulcers.
- Urease positive, creates alkaline environment.
H. pylori
What do you treat H. pylori with?
Triple Therapy: Proton Pump Inhibitor, Clarithromycin, and amoxicillin or metronidazole.
Found in water contaminated with animal urine.
- Causes flu-like symptoms, jaundice, and photophobia with conjunctivitis. Prevalent among surfers and in tropics.
Leptospira Interrogans (Leptospirosis)
Severe form of jaundice and azotemia from liver and kidney dysfunction; fever, hemorrhage, and anemia.
Weil’s Disease
What is Lyme Disease caused by?
Borrelia Burgdorferi
