Patho-L13-Infectious Diseases-Gram (-) Bacterial Infections

What are Neisseria spp.

Aerobic, gram-negative diplococci.

What is unique about pathogenic Neisseria spp.

They can secrete single-stranded DNA for transformation of other Neisseria spp.

What is a significant cause of bacterial meningitis

Neisseria meningitidis, common among adolescents and young adults.

What is Neisseria gonorrhoeae

An important cause of sexually transmitted infection (STI).

What are the symptoms of N. gonorrhoeae in men

Urethritis.

What are the symptoms of N. gonorrhoeae in women

Usually asymptomatic, but untreated can lead to pelvic inflammatory disease, infertility, or ectopic pregnancy.

Who is more likely to have disseminated N. gonorrhoeae infection

People lacking complement proteins that form the membrane attack complex.

What is another name for pertussis

Whooping cough.

What bacterium causes pertussis

Bordetella pertussis, a gram-negative coccobacillus.

What is a characteristic symptom of pertussis

Paroxysms of violent coughing followed by a loud inspiratory "whoop."

Which group is at the highest risk of death from pertussis

Infants under 1 year of age.

How long can children with pertussis have coughing spells

Up to 10 weeks.

How does B. pertussis cause disease

It colonizes the brush border of bronchial epithelium, invades macrophages, and binds to epithelial cell carbohydrates and CR3 integrins on macrophages.

What are the major virulence factors of B. pertussis

Pertussis toxin, adenylate cyclase toxin, dermonecrotic toxin, and tracheal cytotoxin.

What does adenylate cyclase toxin do in B. pertussis infection

It converts ATP to supraphysiologic levels of cAMP, inhibiting phagocytosis, oxidative burst, and nitric oxide-mediated killing.

What is the effect of elevated cAMP in B. pertussis infection

It inhibits phagocytosis, oxidative burst, nitric oxide killing, and formation of neutrophil extracellular traps.

What is the effect of Bordetella spp. on the respiratory system

They cause laryngotracheobronchitis, with severe cases showing bronchial mucosal erosion, hyperemia, and mucopurulent exudate.

What is a common systemic laboratory feature in infants with pertussis

Lymphocytosis.

How does pertussis toxin contribute to lymphocytosis in pertussis

It increases the mobilization of lymphocytes and inhibits their recirculation from blood to lymph.

What can be observed in a peripheral smear of infants with pertussis

Small mature lymphocytes with deep nuclear clefts, which may serve as a diagnostic clue.

What is associated with increased lymphocytosis in pertussis

Pulmonary hypertension, pneumonia, and death.

What bacterium causes pseudomonas infections

Pseudomonas aeruginosa, an opportunistic aerobic gram-negative bacillus.

Who are at high risk for Pseudomonas aeruginosa infections

People with cystic fibrosis, severe burns, or neutropenia.

Why are Pseudomonas aeruginosa infections difficult to treat

The bacterium is often very resistant to antibiotics.

What is a common complication of Pseudomonas aeruginosa in burn patients

It can infect extensive skin burns, leading to sepsis.

What is Pseudomonas aeruginosa a common cause of

Hospital-acquired infections.

What is the function of Exotoxin A produced by Pseudomonas aeruginosa

It inhibits protein synthesis by ADP-ribosylating the ribosomal protein EF-2, leading to host cell death.

How does Pseudomonas cause necrotizing pneumonia

It distributes through the terminal airways in a fleur-de-lis pattern, with pale necrotic centers and red, hemorrhagic peripheral areas.

What is observed on microscopic examination of Pseudomonas infections in lungs

Masses of organisms concentrated in blood vessel walls, with host cell coagulative necrosis (gram-negative bacterial vasculitis).

What is a characteristic skin lesion in Pseudomonas infections of burn patients

Well-demarcated necrotic and hemorrhagic oval skin lesions called ecthyma gangrenosum.