Gram-negative non-enteric bacteria Flashcards
- Identify the sources of infection and types of infection caused by Neisseria meningitidis, Haemophilus influenza, Moraxella catarrhalis, Bordetella pertussis, and Pseudamonas aeruginosa.
N. meningitides: nasopharyngeal colonization, meningitis, sepsis
H. flu: meningitis, sepsis, cellulits, mastoid tis, epiglottis; non-typable: naspharyngeal colonization, vaginal colonization, sinusitis, conjunctivitis, OM, bronchitis, pneumonia (#2), perinatal and neonatal infections
Moraxella: URI, OM
B. pertussis: tracheobronchitis
- Describe how meningococi cause disease, how is prevented.
gram negative diplococcus
nasopharyngeal colonizer, aerosol transmission, humans are only host
causes fulminant bacteremia and septic shock with high fatality, characteristic disseminated intravascular coagulation (DIC) and petechial rash
sequelae: cranial nerve damage, brain damage, cognitive dysfunction, amputation
available tetravalent capsular polysaccharide conjugate vaccine (does not cover serogroup B- polysialic acid)
- Explain the pathogenesis and clinical features of Haemophilus influenza infection, distinguishing between serotype b encapsulated and nontypable variants.
H. flu: meningitis, sepsis, cellulits, mastoid tis, epiglottis; non-typable: naspharyngeal colonization, vaginal colonization, sinusitis, conjunctivitis, OM, bronchitis, pneumonia (#2), perinatal and neonatal infections
small gram neg. coccobacillus, now relatively rare cause of sepsis, meningitis, pneumonia, periorbital cellulitis, mastoiditis (elephant ear), epiglottitis
vaccine for type B, cases of illness mostly in children under 5
invasive infection as an extension from upper respiratory tract, epiglottis will produce stridor, thumb sign which is very serious (requires IV steroids)
- Identify the infections caused by Moraxella catarrhalis.
URI, OM (#3), sinusitis
usually in younger, immunocompromised, CF
- Describe how Bordetella pertussis infection is transmitted, diagnosed, prevented and treated.
gram negative bacillus, obligate human host
highly contagious via aerosol transmission, damage that persists considerably beyond clearance of bacteria
presents as a cold with worsening cough
prevented with vaccine
prevention: DTaP in infants and children, Tdap booster 11-12 yrs, single booster in adults, Tdap with pregnancy
- Compare and contrast pertussis in adults and children.
children have more potential complications, esp young children, including
respiratory compromise, susceptibility to secondary infections (pneumonia), dehydration from post-tussive vomiting
seizures, encephalopathy
adults usually have a prolonged cough with nocturnal exacerbation, although still transmissible, adults serve as a reservoir (unvaccinated or waned immunity)
- Explain how Pseudomonas aeruginosa acts as an opportunistic pathogen and list common sites of infection.
gram-negative rod with aerobic predilection, not fastidious
opportunistic lung, skin (nail soft tissue, otitis externa), eye (corneal inflammation esp with contacts), burn/wound, blood infection, infective endocarditis
often nosocomial
- Identify the characteristics of Pseudomonas aeruginosa that make it troublesome once infection is established.
secreted exotoxin A (protein synthesis inhibitor)
secreted hydrolytic enzymes (elastase, etc)
mucoid strains from CF patients
destroys vascular supply, diminishing host response
which have a natural resistance to disinfectants and many antibiotics (quinolones, some B-lactams)
- Name the 3 antibiotic classes used to treat Pseudomonas.
4th and 5th gen cephalosporins- cephapime
aminoglycosides- gentamyacin
floroquinolones- ciprofloxicin (except moxi)
- Describe the vaccines for Neisseria meningitidis, Haemophilus influenza and Bordetella pertussis, their target populations and their role in preventing disease.
N. men and H flu are based on a polysaccharide coat of the bacteria
Bordetella comes through the “tetanus” vaccine combo Tdap or TDaP
What is the major virulence factor of N. meningitides and relative host defense?
capsule that is antiphagocytic
capsule specific antibodies
functional spleen (B cells and macrophages)
Functional terminal complement components- MAC for complement-mediated lysis
How is meningitis treated and what are risk factors for development?
Risks: B cell or antibody deficiencies anatomic or functional asplenia deficiency in terminal complement communal living
epidemics in Africa (sub-Saharan) and Asia
on pilgrimage
Prevention: MCV4 (doesnt cover serogroup B), earlier vaccination with at risk groups, universal vaccine at 11-12 and 16 yrs, prophylactic antibiotics: rifampin, quinolones
How are N. meningitides and gonorrhoeae different?
NG seldom invades, and is much more common, NM have capsule, NG do not
What are the major virulence factors of B. pertussis. Explain the pathogenesis of whooping cough.
adhesions: attachment to respiratory ciliated epithelium (pertactin, FHA, fimbriae)
tracheal cytotoxin: epithelial damage
pertussis toxin: endotoxin causing decreased transit of lymphocytes from blood into lymph nodes, resulting in lymphocytosis
adenylate cyclase toxin (cell signaling)
bacterial products damage the respiratory epithelium in the catarrhal stage and spasmodic phase follow ending in the convalescent stage when epithelium is replaced
What is the treatment protocol for pertusis?
erthyromycin and others are only useful in catarrhal stage (may decrease transmission)
tx. <3 weeks since symptoms started, after only supportivee care (maintain respiratory status, nasal suctioning, hydration, nutrition)
