Other Pyogenics/Diseases of Childhood/Gram Negs Flashcards
Causes of meningitis in neonates
E. coli, Strep group B
Causes of meningitis in adolescents and young adults
N. meningitis
Causes of meningitis in children aged 1-5
H. influenzae type B (before vaccine)
Most common cause of meningitis in all age groups
Streptococcus pneumoniae
Most common causes of sinusitits/AOM
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Staphylococcus aureus
Endothelial cell and macrophage activation by what leads to vascular leakage?
LPS
Encapsulated bacteria evade what?
phagocytosis
What organ eventually cleans encapsulated bacteria?
the spleen
Asplenia increases risk of infection by
encapsulated organisms
Where do encapsulated bacteria find a safe harbor
in CSF (no complement)
Morphology of pneumococcus
gram positive, diplococcus
Morphology of N. meningitidis
gram negative, diplococcus
Morphology of N. gonorrhea
gram negative, diplococcus
Morphology of H. influenzae type b
gram negative, pleomorphic
Pneumococcus virulence factors
polysaccharide capsule
pneumococcal protein C
N. meningitidis virulence factors
polysaccharide capsule
lipopolysaccharide
N. gonorrhea virulence factors
polysaccharide capsule
lipo-oligosaccharide
H. influenzae type b virulence factors
polysaccharide capsule
lipopolysaccharide
Disseminated intravascular coagulation (DIC)
systemic activation of coagulation by intravascular bacteria
DIC results in
systemic microthrombi followed by hemorrhage after coagulation factors are used up
LPS stimulates
toll-like receptors to induce systemic cytokine secretion and endothelial cell activation
Pathogenesis of Corynebacterium diphtheria
local epithelial necrosis (pseudomembrane formation); systemically released exotoxin A
Pathogenesis of Bordetella pertussis
Cell-bound pertussis toxin with local epithelial inflammation
diseases caused by Streptococcus pneumoniae
sinusitis, otitis media, pneumonia in elderly (CA); meningitis
Strep pneumo is the most common cause of which diseases:
sinusitis
otitis media
community-acquired, lobar pneumonia
meningitis (in adults and children 1-10)
Strep pneumo infections are associated with:
impaired immunity, malnutrition, alcoholism, age
Most important strep pneumo virulence factor
pneumococcal capsular protein PspC
other strep pneumo virulence factors
pneumolysin, pspA (inhibits alternate complement pathway)
pathology of strep pneumo
purulent lesions with creamy white pus; in pneumonia, alveoli filled with fluid and neutrophils
General features of Neisseria
gram-negative encapsulated organisms
very susceptible to adverse environmental conditions
complex nutritional requirements including IRON
Location of N. meningitidis in the body
enters nasopharynx and colonizes mucosa; inability to confine the bacteria to the mucosal surface leads to clinical disease states
N. meningitidis invasion leads to
purulent meningitis or bacteremia; dissemination results in metastatic lesions to skin, meninges, joints, eyes, lungs
incubation period of N. meningitidis
less than 1 week
major virulence factor of N. meningitidis
polysaccharide capsule that acts as gram negative endotoxin
LPS leads to
DIC, puerperal rash, microvascular obstruction
microhemorrhages in capillaries results in
petechial rash, particularly on extremities and ear lobes
eventual obstruction of small blood vessels leads to
ischemic necrosis of limbs
Waterhouse-Friderichsen syndrome
hemorrhage into adrenal medulla
Where does N. meningitidis occur most often
in cluster epidemics such as army recruits, college students
Pathologic lesions of N. meningitidis
include vascular damage secondary to action of LPS on endothelial cells, and purulent lesions of the meninges
N. gonorrhea attaches to
columnar and transitional epithelia (pili) - mucosal membranes of the genital tracts, rectum and nasopharynx
Neisseria gonorrhea lacks
true polysaccharide capsule and doesn’t cause many of the vascular/DIC problems that meningococci cause
LOS instead of LPS
Neisseria gonorrhea has
IgA protease
Neisseria gonorrhea causes
gonorrhea, cystitis; can also cause suppurative arthritis (knees, ankles)
Pathology of Neisseria gonorrhea
suppurative inflammation of mucosal surfaces and subepithelial tissues; grossly purulent lesions and discharge
Important points about Haemophilus influenzae
upper respiratory, sinusitis/otitis, meningitis (pneumonia)
severe disease, including meningitis most commonly seen in young children
Non-invasive H. influenzae
upper respitatory, sinusitis/otitis
most forms causing common upper respiratory symptoms are unencapsulated
Which capsule type for H. influenzae is the most common causing invasive disease?
type b
characteristics of (H. influenzae) type b capsule
endotoxin characteristics, causing DIC
more resistant to complement cytotoxicity
H. influenzae infects through
respiratory route - inhalation of infected droplets from active cases and carriers
H. influenzae noninvasive local disease due to
local overgrowth of colonizing non-encapsulated forms secondary to other pathologic conditions (viral obstruction)
Invasive (type b) H.influenzae disease causes
meningitis, pneumonia, epiglottitis
Invasive (type b) disease likely secondary to
dissemination through blood stream
window of susceptibility for invasive disease (type b)
3 mos to 3 years
during this time, young children are unable to make a good protective antibody response to the type b capsular antigens
why is the H. influenzae vaccine conjugated?
infants make poor antibody responses to the capsule polysaccharides; however, by conjugating the polysaccharides with protein, the conjugated vaccine is effective in infants
H. parainfluenzae
normal flora of the mouth
may result in endocarditis
H. ducreyi
chancroid
M. catarrhalis ithe 3rd most common cause of
secondary bacterial infections such as sinusitis and otitis media
What does Moraxella catarrhalis have?
lipopolysaccharide exotoxin similar to Neisseria; rarely causes septicemia and meningitis
Infections of childhood often associated with?
unprotected window between loss of maternal IgG and self IgG/IgA production
Bordetella pertussis has a strong tropism for
brush border; exotoxin leads to local ciliary paralysis with secondary inflammation
Whooping Cough vaccine
DTP vaccine; immunization leads to production of antibody to the exotoxin
Pathology of Corynebacterium diphtheria
ulcerative lesions of the respiratory mucosa; leads to coagulative exudate and formation of “pseudomembrane”
Corynebacterium diphtheria extoxin leads to
fatty myocardial changes, myofiber necrosis, and polyneuritis
causes toxicity by inhibiting protein synthesis
General characteristics of gram negative rods
- endotoxins: lipopolysaccharides
- frequent drug resistance
- has replaced pyogenic cocci as bulk of hospital-acquired and opportunitistic infections
When does E. Coli cause disease
when they gain access to tissues (peritoneum, urinary tract, sepsis) or secondary to tissue inflammation in abdomen (appendicitis, obstruction)
Types of infection caused by E. Coli
- urinary tract infections/cystitis
- suppurative infections of the abdominal cavity
- gram negative hemorrhagic bronchopneumonia in debilitated patients
- gram negative sepsis: DIC/shock
Suppurative infections of the abdominal cavity can be:
secondary to obstruction: appendicitis, cholecystitis, diverticulitis
performation, trauma (including surgery)
Klebsiella pneumonia associated with
aspiration in a hospital setting
Proteus mirabilis
UTI/pyelonephritis; pneumonia (debilitated patients)
Serratia marcescens
pneumonia (debilitated patients)
Pseudomonas aeruginosa
rod-shaped gram negative; motile, flagellum, aerobic, non-spore forming
Pseudomonas aeruginosa contains
fluoroscein pigment - pyocyanin and pyoverdin
Where is pseudomonas
ubiquitous in hospitals - cultured extensively from surfaces in hospitals
What immune response protects from an pseudomonas infection?
phagocytosis
Pseudomonas is a frequent deadly pathogen in patients with
cystic fibrosis, severe burns, or neutropenia
psuedomonas is characterized by
necrotizing inflammation
vasculitis with abundant organisms
BLUE HAZE
Pseudomonas virulence factors
endotoxin - LPS extotonix A similar to diphtheria protective exopolysaccharide (biofilms) phospholipases Fe-containing compounds toxic to endothelial cells leukocidin
Pseudomonas lung infections
fulminant pneumonias
Other forms of pseudomonas infections
corneal keratitis in wearers of contact lenses
endocarditis and osteomyelitis in IV drug users
external otitis
severe external otitis in diabetics
Anaerobic gram-negative bacterial infections
Bacteroides
Fusobacterium
Peptococcus
Peptostreptotoccus (gingival infections)
foul-smelling pus and mixed-infections associated with
anaerobic gram-negative bacterial infections
Legionella
- small gram-neg. flagellate rod
- community outbreaks associated with contaminated aerosolized water supplies
- most common inindividuals with pre-disposing lung/heart disease, including organ transplant
- fibrinopurulent necrosis leads to scarring of pulmonary tissues
Helicobacter pylori
spiral/helical gram negative, motile, urease
commonly found in antrum
