Non-Enteric Gram Neg Flashcards
1
Q
N meningitidis Morphology Reservoir Transmission Population
A
- Gram neg diplococci w/in CSF = meningococcus
- Human-specific nasopharyngeal colonizer. Part of normal microbiota, but does NOT cause respiratory infections.
- Aerosol transmission
- Most disease occurs in infants, children, and young adults. Rarely a problem in neonates due to maternal Abs
2
Q
N meningitidis virulence factors (7)
A
- Antiphagocytic capsule w/ diff polysaccharides (A, B, C, Y, W-135) is most important. Abs may be made against capsule to aid phagocytosis (host defense). Abs may be passed from mother to infant.
- Pili / adehsins bind nonciliated nasopharyngeal epithelial cells
- LPS (endotoxin) and peptidoglycan damage host mucosal cells → invasion
- Surface proteins such as pilin, Opa, capsule, and LOS (lipo-oligosaccharide) show antigenic variation.
- Meningococcal IgA protease degrades IgA
- Phenotype switching by taking up / releasing free DNA
- Iron acquisition – transferrin and lactoferrin (not siderophores)
3
Q
Diseases caused by N meningitidis (4)
A
- Characterized by disseminated intravascular coagulation (DIC) w/ petechial rash → purpurae. Sequelae may include gangrene, amputation, and adrenal insufficiency.
- Leading cause of acute bacterial meningitis in adolescents / young adults.
- High mortality rates. Survivors often have cranial nerve damage (deafness / blindness), brain damage, and cognitive dysfunction (seizures, learning disorders, speech problems).
- Fulminant bacteremia / septic shock
- Waterhouse-Friderichsen Syndrome – adrenal infarction
4
Q
Protection against N meningitidis (5)
A
Vaccine
Abs from mother
Spleen - protects against encapsulated bacteria
MAC - complement C5-9.
Prophylaxis for close contacts. Rifampin, FQ, and cephalosporins
5
Q
Meningococcus vaccine
2 types and mechanism
Vaccination schedule
A
- Old vaccine has 4 capsular polysaccharides and elicits a short-lived T-independent Ab protection
- Tetravalent (A/C/Y/W-135) capsular polysaccharide conjugate vaccine. Conjugated w/ diptheria toxoid protein, which elicits a stronger T-dependent Ab protection. Does NOT cover serogroup B, which has polysialic acid capsule (same as K1 E coli)
- Vaccinate high risk kids less than 12 y/o (complement deficiency, asplenia, traveling to epidemic areas, etc.) Booster every 5 years.
- Vaccine everyone at age 12
- Universal booster at age 16.
6
Q
Where do outbreaks of N meningitidis usually occur?
A
- Outbreaks are common in close living quarters: dorms, prisons, barracks, cruise ships, households, pilgrimages (Hajj).
- “Meningitis Belt” in Sub-Saharan Africa and Asia. Mainly serogroup A.
7
Q
Tx for N meningitidis
Infection
Prophylaxis
A
Penicillin or cephalosporins
Prophylaxis - Rifampicin, FQ, or cephalosporins.
8
Q
N gonorrhoeae What are #1 and #2 most common bacterial STIs? Morphology More or less common than meningococcus? Capsule or no capsule? Diseases in males, females, newborns? Sequelae Prevention
A
1 = chlamydia
#2 = gonorrhea
• Gram neg diplococci w/in PMNs = gonorrhea.
•Much more common than N meningitidis
•No capsule
•Diseases
• Causes urethritis in males, cervicitis in females (often asymptomatic)
• Rarely invades (septic arthritis or DGI: disseminated gonococcal infection)
• Vaginal delivery may cause ocular infection in newborns
•Sequelae – PID, fallopian tube scarring, infertility, and ectopic pregnancy in women (most of which are asymptomatic beforehand)
•No vaccine. No durable immunity to reinfection (due to antigenic variation).
9
Q
Haemophilus influenzae type B Morphology Agar Population Transmission Virulence factor Diseases (6) Vaccine and schedule
A
- Small Gram Neg coccobacillus.
- Grows on chocolate agar w/ lysed RBCs.
- Mainly affects little kids less than 5 y/o.
- Aerosol transmission, entering via the nasopharynx.
- Antiphagocytic polysaccharide capsule is main virulence factor. Made of polyribosyl ribitol phosphate.
- Diseases – meningitis, sepsis, pneumonia, cellulitis, mastoiditis, epiglottitis
- Cellulitis often includes, face, orbit, or periorbit
- “Thumb sign” seen in epiglottitis. May be lethal by blocking airway. Tx w/ dexamethasone and AB’s
- Hib polysaccharide conjugate vaccine given earlier than mening. Usually given b/w 2-15 months. Rarely given past age 5.
10
Q
What is most common cause of mastoiditis?
A
Pneumococcus
11
Q
Nontypable Haemophilus influenzae (NTHi) Capsule or no capsule Reservoir Diseases (6) 2 most common causes of otitis media and CAP?
A
- No capsule (non-typable)
- Asymptomatic colonization of nasopharynx (80% of people) and vagina
- Diseases – sinusitis, conjunctivitis (especially older kids), otitis media, bronchitis, pneumonia, and perinatal / neonatal infections.
- 2 most common causes of otitis media: H flu and pneumococcus
- 2nd most common cause of community-acquired pneumonia (CAP) in adults. S pneumoniae is #1
- Neonatal infections – May cause premature birth, chorioamnionitis, postpartum sepsis in mother, or pneumonia, sepsis, or meningitis in infant.
12
Q
Moraxella catarrhalis Reservoir Population Transmission Diseases (4)
A
- Colonizes upper respiratory tract (mainly in kids)
- Aerosol transmission
- Diseases (more common in kids)
- Upper respiratory infections in kids. 3rd most common cause of sinusitis and otitis media
- Bronchitis / pneumonia in people w/ underlying lung conditions such as viral URI in kids or COPD in adults.
- Sepsis, meningitis, and other disseminated infections in immunocompromised, such as those w/ CF, neutropenia, lupus, or leukemia
- Nosocomial infections, especially in pulmonary / pediatric ICU’s
13
Q
What are the top 3 causes of sinusitis and otitis media?
A
#1 = pneumococcus #2 = Non-typable H flu #3 = Moraxella catarrhalis
14
Q
Bordetella pertussis Morphology Agar Transmission Reservoir Disease / pathogenesis
A
- Small Gram Neg coccobacillus appearing singly or in pairs.
- Nutritionally fastidious, requiring rich blood agar or synthetic media such as nicotinamide.
- Highly contagious aerosol transmission.
- Obligate human pathogen. Adults are main reservoir, but they have less severe disease than kids.
- Causes tracheobronchitis / whooping cough. Damage to respiratory tract persists long beyond clearance of bacteria. “100 day cough”. Mucosal infection of upper respiratory tract w/ little to no deeper invasion to lungs or blood.
- Tracheal cytotoxin kills mucociliary escalator. Only way to get mucus out is by coughing
15
Q
Bordetella pertussis virulence factors (4)
A
- Adhesins attach to respiratory ciliated epithelial cells: pertactin, filamentous hemagglutinin (FHA), fimbriae / pili
- Tracheal cytotoxin (TCT) – peptidoglycan fragment → cilostasis / ciliated epithelial damage mediated by LPS, IL1, and NO.
- Pertussis toxin (PTx) – A/B subunit exotoxin → disordered phagocyte / lymphocyte function due to disruption of cAMP. Disrupted transit of lymphocytes from blood into lymph nodes causes lymphocytosis.
- Adenylate cyclase toxin – interferes w/ host signaling
