8 Flashcards

Question

Treatment - Purpura Fulminans

Answer 1

Most Neisseria sp. are penicillin resistant • Plasmid encoded b-lactamase first identified in 1976 • Resistance to tetracycline was first described in 1986 • Now reported in most parts of the world • Streptococcal derived • Resistance to other antibiotics is increasing • Antimicrobial chemoprophylaxis of close contacts is the primary means of preventing secondary cases of sporadic meningococcal disease.

Answer 2

Behavioral • Condom use, etc. • Partner notification • Early diagnosis and treatment • Vaccines to gonococci difficult to produce • Antigenic and phase variation • Protective intracellular components • Vaccine to meningococci • Quadrivalent (MPSV4) - derived against capsular polysaccharide from 4 serotypes (A, C, Y, and W135) • Tetravalent (MCV4) - polysaccharide-protein conjugate • Children <2 yrs do not respond to polysaccharide vaccines

Answer 3

• Expression of gene product is turned on or off at high frequency • Promoterinversion(E.coliexample)

Answer 4

Slipped strand mispairing • Colony opacity-associated (Opa) genes (10 +) • Encode outer membrane proteins • Opa’s presence results in neutrophil uptake • Some gonococci lack Opa and avoid phagocytosis • Also controls other surface proteins, as well as LPS in gonococci and meningococci

Answer 5

• Changes in composition or structure of surface molecules (e.g., pili – host cell attachment) Reassortment and recombination of pilS loci

Answer 6

Small Gram negative coccobacilli • Aerobic (some anaerobic) • Colonizes upper respiratory tract of most children and adults • Non-typeable strains • H. influenzae probably infects only ~1-2% of healthy children • Note: influenza is caused by a virus, not to be confused with H. influenzae • Thought to be so up until 1933 (co-occurring opportunistic pneumonia)

Answer 7

hemin (X factor) and NAD+ (V factor) for growth • Access to these factors require lysed blood (Chocolate agar) rather than whole-blood (blood agar) for growth Other Haemophilus species require only NAD+ • Growth on Blood agar • Typeable H. influenzae strains • Seven antigenically distinct capsular polysaccharides • a,b,c,d,e,e’,f • Non-typeable H. influenzae strains • Unencapsulated

Answer 8

• Bacteremia (bloodstream) and meningitis in children younger than 2 years

Answer 9

frequently cause respiratory tract disease in infants, children, and immuno-compromised adults

Answer 10

predominant bacterial pathogen of otitis media (middle ear infection

Answer 11

sometimes causes pneumonia or bacterial endocarditis

Answer 12

causes chancroid (a STD)

Answer 13

member of the normal flora of the mouth and | occasionally causes bacterial endocarditis

Answer 14

causes conjunctivitis and Brazilian purpuric fever

Answer 15

Resistance to phagocytosis (as long as antibody not present) | • Basis for Hib vaccine (against H. influenzae type B)

Answer 16

• Autotransporter protein, directs their own secretion out of cell

Answer 17

Play important role in adherence to mucosal surfaces • Pili are involved in twitching motility and required for biofilm formation

Answer 18

* Antibodies against capsule are protective • Immunization of infants (1985) * Pure Hib PRP polysaccharide vaccine is not immunogenic in infants * PRP-conjugated diphtheria toxoid (adjuvant) produces good antibody responses in infants * Unencapsulated strains lack capsular polysaccharides and require development of novel surface targets

Answer 19

Many H. influenzae and non-typeable isolates produce β-lactamase • Resistant to penicillin or ampicillin • Chloramphenicol drug of choice • Third-generation cephalosporins (ceftriaxone or cefotaxime) • Penetrate meninges well • Corticosteroids may reduce complications

Answer 20

* Gram negative bacillus (rod) • Ubiquitous * Found in soil and water * Motile * One or several polar flagella • Polar pili – twitching * Aerobic (this species) * Some strains grow anaerobically by nitrate resipration

Answer 21

Colonies produce water-soluble pigments that function as antibacterials • Pyocyanin (blue-green) • Pyoverdin (green) • Fluorescein (yellow fluorescence) • Fruity or grapelike odor to colonies (or near wounds) * Grow rapidly, very robust * Minimal nutritional requirement * Non fermentative * Indophenol oxidase (just like Neisseria sp.) * Need only acetate and ammonia as carbon and nitrogen sources * Most organic compounds can provide this including petroleum and toxic wastes * Can survive in hand creams, soaps, and dilute antiseptics

Answer 22

* Mucoid polysaccharide capsule (alginate) shields from immune system * Siderophores * Elastase * Exotoxin A * Phospholipase C

Answer 23

``` Toxin A • Collagenase • Elastase • Exoenzymes • Flagella • Heat stable hemolysin • Tissue damage by proteases and toxins ```

Answer 24

Siderophores, • Phospholipase C:

Answer 25

Compete with transferrin for iron • Iron limitation causes increased production of elastase and exotoxin A • Damages tissues or creates conditions that make iron more accessible

Answer 26

Hydrolyzes phospholipids (lecithin) in the eukaryotic membrane, releasing usable phosphate

Answer 27

* Encounter * Adheres to vegetables and plant matter • In water taps, drains, wet surfaces * Otitis externa – swimmer’s ear • Hot tubs! (folliculitis, dermatitis) * “Hot Tub Rash” * 108 organisms/mL * Opportunistic pathogen * Local or systemic breach of immune system • Immunocompromised patients * Organism does not adhere well to healthy epithelium • Can enter through abrasions, cuts, etc. * Usually they don’t get far unless in large numbers * After entry, ability to spread and multiply depends on two things: * Avoiding phagocytosis * Successful adherence to a surface * Adherence to epithelia is mediated by flagella and pili * Interactions with glycolipid (cleaves sialic acid to create asialo GM1; receptor for Type 4 pili) on host cells and toll like receptor (TLR5)

Answer 28

``` • Frequent cause of nosocomial infections Regional incidence (%) of pathogens isolated from patients with hospital- acquired pneumonia (HAP) ```

Answer 29

* Polysaccharide capsule (alginate) * Mucoid phenotype * Major adhesin and component of biofilm in cystic fibrosis patients * Production is highly regulated * Numerous cytolytic exotoxins

Answer 30

LPS • Adhesin • Lipid A = endotoxin • Interacts with host TLR4 to initiate inflammatory response • Fever, hypotension (low blood pressure), Gram-negative sepsis • Less inflammatory than E. coli or S. typhimurium • Core oligosaccharide interacts with CFTR (an ATP-binding cassette transporter; cystic fibrosis transmembrane conductance regulator) • Bacterial internalization, initiation of immune resistance • Long O-antigen side chains • Responsible for resistance to human serum, antibiotics, detergents * Exotoxins (cause local inflammation) • Some kill host cells (Exotoxin A) * ADP-ribosylation of EF-2 (similar to diptheria toxin) • All are tightly regulated * Multifunctional enzymes (proteases) • Elastase * Cleaves elastin and collagen – direct tissue damage * Cleaves proteinase inhibitors * Cleaves immune system components • Complement and immunoglobulins * LasA * Serine protease that works with elastase to degrade elastin

Answer 31

Delivers virulence factors directly into host cells • Transfer from bacterial cytosol to host cytoplasm • Some components are similar to flagella • Targets specific proteins on host cells • Induced by host cell contact or low calcium levels • Secretion effectors include ExoS, ExoT, ExoU, and ExoY which are transcriptionally controlled by ExsA.

Answer 32

P. aeruginosa does not adhere well to normal intact epithelium • Piliated strains adhere better than non-piliated strains • Cystic fibrosis respiratory cells bind more P. aeruginosa than those of normal cells

Answer 33

• Located on human chromosome 7

Answer 34

* Loss of Cl- transport * Hereditary * ΔF508 most common mutation * Can be rescued with normal copy of gene

Answer 35

decreased sialylation of surface glycolipids • P. aeruginosa binds to these asialo-glycolipids * Dehydration of respiratory secretions * Thick mucus produced which impairs mucociliary system * Mucoid exopolysaccharide (alginate) shields organism from immune system * However, these alginate strains produce less protease and toxins

Answer 36

P. aeruginosa forms biofilms within the lungs • Communities of bacterial cells that reside within a extracellar matrix • Bacteria within biofilms are recalcitrant to antibiotic treatments and more resistant to host defenses. • Biofilm formation contributes to chronic nature of Pseudomonas infections

Answer 37

* LPS (endotoxin) mediated * Specifically lipid A moiety * Triggers production of Tumor Necrosis Factor (TNF) * TNF stimulates macrophages to produce interleukin-1β (IL-1)

Answer 38

Severe systemic illness marked by hemodynamic derangements and organ malfunction brought about by the interaction of certain microbial products with host reticuloendothelial cells. • MODS (Multi-Organ Dysfunction Syndrome) • High cardiac output, lowered blood pressure • Distributive shock (lack of perfusion of selected vascular beds) • Three Requirements 1. Large population of infecting/colonizing organisms 2. Presence of bacterial products that stimulate release of host cytokines 3. Widespread dissemination of microbial products to host’s reticuloendothelial system

Answer 39

Depends on: • Nature and severity of infection • Host defense state • Promptness and efficacy of treatment • Neutropenic patients: 50-70% mortality • Pseudomonas endocarditis: up to 50% mortality • Sepsis that reaches shock stage: >50% mortality