Gram (-) Ubiquitous and Intracellular

Question 1

Pseudomonas aeruginosa

Answer 1

Key:

• pyocyanic pigment, grape-like scent on culture
• opportunistic (most common (-) nocosomial)
• (vf) fimbrae, flagella, proteases X fibronectin and immune response
• cystic fibrosis pneumonia
• *ecthyma gangrenosum (bacteremia)- hemorrhagic vesicles with erythema
• swimmer’s ear

Extra:

• aerobic bacillus singly, pairs, in short chains with a single flagella, characteristic green-blue colonies, grow in nearly any environment with a grape-like scent
• doesn’t adhere well to intect epithelium, immunocompromised and physical destruction
• attachment and colonization (pili/fimbrae/flagella < fibronectin protection) -> local invasion (elastase, alkaline phosphatase, phospholipase C lyse fibronectin and destroy Igs, complement) -> systemic dissemination (LPS->DIC, Exotoxin A -> protein synthesis, Exoenzyme S -> cytopathic)
• quorum sensing & mucoid exopolysaccharide (biofilm)
• IV drug endocarditis, self resolving folliculitis, keratitis

Question 2

Acinetobacter baumani

Answer 2

Key:

• coccobacillus strictly aerobic
• increasing resistance with overexpression of efflux pumps, beta-lactamases, carbapenamases
• opportunistic pneumonia - prolonged mechanical ventilation
• bacteremia from catheters

Extra:

• able to survive in dry environments, some have polysaccharide, pili fomite adherence to form biofilms
• resistance in preventing AB from binding to PBPs in cytoplasmic membranes

Question 3

Klebsiella pneumoniae

Answer 3

Key:

• *most clinically important opportorganism
• bacillus, identified by H2S- and indole negative
• *hypermucoviscosity phenotype -> abcess (liver-east Asia)
• both hospital and community acquired pneumonia potential
• *pneumonia “currant jelly sputum”

Extra:

• (vf) K1 & K2 capsular serotypes, protect from macrophage.
  
  • LPS
  • Siderophores- iron uptake
  • type 3 fimbrae (biofilms)
  • ESBL strains (extended spectrum beta-lactamase)
• pneumonia/pulmonary infection, abcesses anywhere, bacteremia, nosocomial meningitis

Question 4

Bartonella species

Answer 4

Key:

• pleiomorphic stain black with Warthin-Starry
• *cat scratch, HIV bacillary angiomatosis, trench fever
• tender lymphadenopathy (cat)
• vascular lesion in HiV
• war time fever & bone pain

Extra:

• flagella allow it to find/attach to cell (erthyrocyte) -> intracellular replication -> lysis
• trench fever (B. quintana)- body louse -> humans, fever + bone pain + malaise + headache
• cat scratch- regional tender lymphadenopathy
• bacillary angiomatosus (B. henselae or B. quintana) - HIV due to low CD4, cutaneous vascular lesion