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Microbio Block 1 > Neisseria, Haemophilus, & Pasteurella > Flashcards

Neisseria, Haemophilus, & Pasteurella Flashcards

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1
Q

Neisseria - how many species, and which ones are human pathogens?

A

10 species in humans, 8 colonize mucosa

Pathogens: N. gonorrhoeae, N. meningitidis

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2
Q

Morphology of Neisseria spp

A

Gram neg diplococci; intracellular in neutrophils

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3
Q

Transmission of Neisseria spp

A

Non-motile = intimate contact for transmission

*Sensitive to drying = can’t be transmitted on dry contaminated toilet seat

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4
Q

Lab diagnosis of Neisseria

A

Grows on chocolate agar (fastidious growth, non-selective) & on selective Thayer Martin agar (abx + chocolate)

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5
Q

Abx on Thayer-Martin agar

A

Vancomycin, colisitin, TMP-lactate; anti-fungals nystatin & anisomycin or amphotericin B

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6
Q

What is chocolate agar?

A

Heated blood agar = deactivates enzymes that degrade NAD (f V), which is needed with hemin (f X) for fastidious growth of bacteria
Grows Haemophilus, Neisseria, Tularemia

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7
Q

Sugars oxidized by Neisseria human pathogens

A 
Gonococci = Glucose
MeninGococci = Maltose + Glucose
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8
Q

N. meningitidis important wall/membrane features

A

PS capsule* (virulence); outer membrane with porin, Opa, Rmp proteins; cytoplasmic membrane pilli

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9
Q

Most important antigens in PS capsule of N. meningitidis

A

A, B, C, W-135, Y*
Many others
No PS capsule in N. gonorrhoeae

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10
Q

Quellung reaction

A

In encapsulated bacteria, capsule swells when specific anti capsular antisera added
*SHNKSS = Strep pneumo, H. flu B, N. meningitidis, Salmonella, Kleb pneumo, GBS

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11
Q

Pilli structure

A

Originate at cytoplasmic membrane; repeating subunits (pillins) with conserved amino end and highly variable carboxyl end (PilC) = antigenic diversity

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12
Q

Pilli function

A

Virulence (attachment to nonciliated epithelial cells, resistance to neutro killing), transfer of genetic material, motility

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13
Q

Virulence of Por proteins

A

Prevent granulation of neutros (phagolysosome fusion), invasion into epithelial cells, resistance to complement-mediated serum killing
PorA,B in mening; only PorB in gonococci

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14
Q

Virulence of Opa proteins

A

Binds epithelial cells to phagocytic cells = cell-cell signaling
Causes localized disease pathogens to appear opaque on culture; advanced disease = transparent

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15
Q

Virulence of Rmp proteins

A

Reduction modifiable proteins; protects surface antigens from bactericidal antibodies

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16
Q

Why are Neisseria strictly human pathogens?

A

Compete with human hosts for iron by binding host transferrin w/ transferrin binding protein
*Different from siderophores made by other bacteria to scavenge Fe

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17
Q

LOS antigen

A

In cell wall of Neisseria, lipid A endotoxin + core oligosaccharide
*Missing the O-ag PS in LPS in most G- bacilli

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18
Q

Lipid A in Neisseria

A

Endotoxin, stimulates release of proinflam cytokines, like TNF-a
Causes acute vascular damage assc with meningococcus

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19
Q

Extracellular virulence factors of Neisseria

A

IgA1 protease - allows colonization on mucosal surfaces

Beta-lactamase - resistance to abx

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20
Q

Neisseria vaccines

A

No vaccine for gonococci

Vaccine available for meningococci (except B)

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21
Q

N. meningitidis colonization

A

Humans are only natural carriers; asymptomatic in 1-40% (young, crowded)
Disease more common in dry/cold months bc crowding
Carriage transient - cleared with specific IgG

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22
Q

Diseases caused by N. meningitidis

A

Meningitis, meningococcemia, meningococcal pneumonia

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23
Q

N. meningitidis as a cause of meningitis

A

M/c cause of acute bacterial meningitis in children

Second m/c cause in adults (S. pneumo)

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24
Q

Meningococcemia symptoms

A

Preceded by pharyngeal infection
Multiorgan failure w bacteremia, small blood vessel thrombosis, petechiae on trunk & lower extremities coalesce to form hemorrhagic lesions
*Waterhouse-Friderichsen syndrome (bilateral adrenal destruction)

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25
Prevalence and complications of meningococcal diseases
1000-1200 people/y in US W/o abx -> almost 100% fatal; w abx, 10-15% fatal If survive: 11-19% lose limbs (thrombosis, necrosis), CNS problems (toxins and inflam), deaf, mental impairment, seizures or strokes
26
Tumbler test for meningococcal disease
If petechiae do not blanch when pressed with a glass, raises concern for meningococcal disease
27
Bacterial latex-ag testing in CSF for N. meningitidis
Low sensitivity for diagnosing acute bact men; useful if individual has received prior abx
28
Bacterial latex-ag testing in CSF for N. gonorrhoeae
No capsule - test can't be done
29
Infection control of N. meningitidis
Transmitted by resp droplets/saliva *Droplet precautions for first 24h abx Chemoprophylaxis: given to close contacts with exposure to secretions w/in 24h identified; rifampin, cipro, ceftriaxone
30
Populations at risk for meningococcal disease
Asplenia (SCD, surgical removal) | Terminal complement deficiency (6000x risk)
31
N. meningitidis immunity
Passive for 6 mos of life d/t maternal Abs Acquired d/t colonization with N. men or bact w cross-rx Ags (non-encapsulated Neisseria, E. coli K1 Ag, etc.) Vaccine
32
2 types of meningococcal vaccines
Meningococcal PS vaccine MPSV4 - over 55 yoa Men conjugate vaccine MCV4 - younger than 55, stronger immune response Both cover A, C, Y, W-135, *NOT B
33
Who gets meningococcal vaccines?
Routine: 11-12 and booster at 16 High risk routine: children >2 mos w asplenia or term comp def, booster 5 y later for unvacc college freshman in dorms, travel/ residence in high-risk area, science/lab techs with routine exposure, unvacc military *During outbreaks for high risk groups
34
Where is the meningococcal belt?
26 countries in sub-Saharan Africa, from Senegal to Ethiopia
35
Men B vaccine
Recommended for individuals
36
How is N. gonorrhoeae transmitted?
1': sexual contact Major reservoir in infected asymptomatic person W -> M, 20% chance M -> W, 50% chance
37
Clinical presentation of gonococcal disease in men
25% asymptomatic Purulent urethral discharge 2-5d post-infxn Rare complications: epididymitis, prostatitis, peri-urethral abscesses
38
Clinical presentation of gonococcal disease in women
50% asymptomatic Vaginal discharge, dysuria, abd pain Complications in 10-20%: salpingitis, tubo-ovarian abscesses, PID, infertility
39
Dx of gonococcal disease
Gram stain of discharge | NAAT: 4 hours rapid test of urine (M,W), cerv/vag (W), urethral (M); no info about abx resistance w/ NAAT
40
Tx and abx resistance of gonococcal disease
2007: quinolones no longer recommended (resistance in Asia -> HI -> US); 2009: ceph-resistant in Japan Ceftriaxone IM x1 (+ azithro for Chlamydia; no oral bc resistance concerns); contact all sexual exposures in past 2m for evaluation/tx
41
Differences in meningococcal and gonococcal treatment regimens
Essentially the same: 3rd gen cephalosporin (usually ceftriaxone) Men: 2gm IV every 12 h Gono: 250 mg IM x1
42
Gonococcal ophthalmia neonatorum
¼ of infants with untreated mothers -> corneal ulceration, permanent blindness *Universal prophylaxis at birth
43
Prevalence and symptoms of disseminated gonococcal infection
1-3% infected individuals | Skin papules -> hemorrhagic pustules, typically on extremities
44
Septic gonococcal arthritis
Two presentations: 1) pustular skin lesions, tenosynovitis (knees, wrists, ankles, fingers), arthralgia w/o purulent arthritis; OR 2) purulent arthritis w/o skin lesions STD = synovitis, tenosynovitis, dermatitis
45
Typical arthritis of gonococcal disease
Monoarticular, migratory, asymmetric; swollen joint, painful, red
46
Fitz-Hugh-Curtis syndrome
Adhesions bt liver capsule and parietal peritoneum = RUQ pain Fibrosis of hepatic capsule in females, d/t gonorrhea or chlamydia
47
Morphology of Haemophilus
Small pleomorphic gram neg bacilli (coccobacillus); facultative anaerobes, fastidious growth requiring fV (NAD) or fX (Hemin), nonmotile
48
Structure of Haemophilus
Cell wall with LPS | PS capsule with 6 antigenic serotypes (A-F)
49
Virulence factors of Haemophilus
``` PS capsule (avoid phago) Colonization by pilus, adhesions, IgA protease LPS, cell wall components impair ciliary function -> damaged resp epithelium ```
50
Other species of Haemophilus and their diseases
H. parainfluenzae & non-encapsulated H. influenzae -> upper resp tract in almost everyone w/in few mos of life Local spread -> OM, sinusitis, bronchitis, pneumonia Disseminated dz (rare): usually in non-vacc, d/t encapsulated H. flu type B
51
H. flu type B vaccine
``` Uses PRP (found on PS capsule) conjugated to protein Given b/t 2-18 mos ```
52
Transmission of Haemophilus
Resp droplets; droplet precautions for 24h of abx for kids w/ pneumonia d/t H. spp; standard precautions for adults Droplet precautions if epiglottis/ meningitis
53
Progression of dz in Haemophilus
Nasopharynx infxn -> bacteremia -> metastases to meninges (low mortality w treatment), and rarely: epiglottitis, cellulitis (cheek/ periorbital), arthritis (single large jt)
54
Dx of Haemophilus
NEVER CULTURE EPIGLOTTIS Culture: 1-2 mm opaque colonies; satellite phenomenon *Alert lab if suspect H. ducreyi (STI)
55
Satellite test
Streak S. aureus -> lyses RBCs, releasing NAD for Haemophilus sp. H. flu will only grow around S. aureus on blood agar
56
Tx of Haemophilus
Broad-spectrum ceph in severe disease Less severe: ampicillin (30% strains resistant, check culture) Chemoprophylaxis in kids at high risk to eliminate carriage: rifampin
57
H. ducreyi disease
STI primarily in Africa, Asia, with cycles in US | Buboes, chancroid ulcer
58
Buboes & chancroid
Classic for H. decreyi Buboes: inguinal lymphadenopathy, may suppurate Chancroid ulcer: ragged w/ raised edges, sharply demarcated without induration; purulent, dirty/gray base; base is friable
59
Morphology of Pasteurella sp.
Small, facultative anaerobes, G- coccobacilli, bipolar staining
60
Location and transmission of Pasteurella
Normal commensal in oropharynx of healthy animals; transmission by direct contact with saliva of animals (bite, scratch, lick, share food)
61
Most common species of Pasteurella and animals hosting them
P. multocida - m/c; cats, dogs P. canis - dogs Others assc with animal bites but less common
62
3 clinical presentations of Pasteurella
M/c: local cellulitis/ lymphadenitis after bite or scratch Exacerbation of chronic resp dz if underlying lung dz; ? reflects colonization or oropharynx -> aspiration of oral secretions -> consolidated pneumonia; RARE Systemic infxn in immunocompromised pts (esp underlying liver dz) -> fulminant dz w fever, rigors, vom, shock, coagulopathy; RARE
63
Most common presentation of Pasteurella infection
Following animal bite/scratch -> rapid inflam (1-2 h) w excruciating pain at lesion Septic phlegmon (diffuse inflam w purulent exudate), mod-high fever +/- n/v, HA, diarrhea Can develop septic arthritis (more common in jt replacements)
64
Dx & tx of Pasteurella
Grows well on blood agar, chocolate agar, poorly on MAC and other G- rod-selective media "Mouse-like" odor Tx: susc to many abx (not semisynthetic pens, 1st g ceph, or AGs), penicillin is DOC (often amox/clav acid; may use more broad spectrum)

Microbio Block 1 (14 decks)

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