legionella bacteriology
- poorly staining gram -
- facultative intracellular parasite (free-living motile with flagella infectious and intracellular nonmotile during replication)
- accidental opportunistic (recently)
transmission of legionella
biofilms in stagnant freshwater and in HVAC systems where tehy enter human lungs and parasitize alveolar macrophages
is legionella contagious?
no - simultaneously exposed cases
possible outcomes after contaminated water with legionella is inhaled or aspirated
asymptomatic seroconversion, pontiac fever, legionnaires disease
pontiac fever
flulike, symptoms immunogenic as immune system kills live and/or clear dead bacteria
-patient is previously healthy
legionnaires disease
- previously ill patient (elderly, immunosuppressed, diabetic, heart or lung disorder, smoking, alcohol)
- pneumonia with KIDNEY involvement and diarrhea
legionella virulence factors
- dot/icm locus (type IV secretion system)
- pilE and pilD (pilus formation for attachment)
- pep/pro (zinc metalloprotease to escape)
what are the symptoms or legionnaires disease due to?
infection and killing of alveolar macrophages (which engulf the bacteria but lysosomes fail to fuse with the resulting endosomes - bacteria then multiply and kill host cell)and renal failure
risk factors for legionnaires disease
increasing age, immunosuppression, smoking, chronic heart/lung disease, chronic swallowing disorder, male
presentation of legionnaires disease
altered mental status, headache, high fever, pneumonia/chest pain, acute renal failure, pancreatitis, diarrhea
clue is diarrhea and pneumonia together**
diagnosis of legionella infection
-urine antigen test (commercial ELISA kit) - detects LP1 strain
does NOT detect other strains
-culture (difficult)
-silver stained biopsy (gram stain will fail)
treatment of legionella
- pontiac fever resolves without treatment
- LD = antibiotic that penetrates infected cells (levofloxacin and azithromycin)
complications for legionnaires disease
can have fatigue, neurological symptoms, neuromuscular symptoms, cough - usually takes a year to recover
coxiella burnetii bacteriology
Q fever
-proteobacteria (related to legionella - used to be considered rickettsia)
how is coxiella burnetii transmitted
inhalation of aerosols of infected urine, feces, birthing matter (no vector!)
- dander from infected animals is extremely infectious
- zoonosis of asymptomatic infection of ruminants
where is coxiella burnetii common?
Q fever - common in netherlands, france, spain, iraq
c. burnetii virulence factors
- acid phosphatase
2. superoxide dismutase (helps bacteria survive in FUSED lysosome-endosome)
pathogenesis of c. burnetii
multiples iwthin aveolar monocytes and macrophages - travels in them to liver, spleen, bone marrow (not just lung)
presentation of c. burnetii
PNEUMONIA AND HEPATITIS also fever, chills, sweats, severe headache, dry cough, history of travel, pregnancy complications
c. burnetti diagnosis, treatment, prevention
lab: IF, IHC, ELISA available
treatment: doxycycline or fluoroquinolones
prevention: vaccine available
mycoplasma pneumoniae bacteriology
- smallest free living organism
- strictly aerobic
- no cell wall
- contains cholesterol in cell membrane
- fried egg shape in colonies
what does mycoplasma pneumoniae cause in humans?
tracheobronchitis, bronchiolitis, atypical pneumonia “WALKING PNEUMONIA”
how is mycoplasma pneumoniae transmitted?
respiratory droplets - resides on mucosal surfaces of respiratory and genital tract
mycoplasma pathogenesis
- P1 adhesin binds respiratory epithelial cells
- some intracellular penetration
- CARDS exotoxin (ciliostasis, some cell death)
- also has hydrogen peroxide causing tissue damage - from bacterial metabolism
