Legionellosis /Legionnaire’s disease/. Ornithosis and Psittacosis. Flashcards
what is the EPIDEMIOLOGY OF LEGIONELLOSIS?
LEGIONELLA PNEUMOPHILA
almost occurs solely in infants
however has a high risk group - such as elderly people
and chronic diseases - such as copd , emphysema , diabetes
immunocompromised
smokers
esp TRANSPLANTATION
what are the CHARACTERISTICS OF LEGIONELLA PNEUMOPHILIA ?
gram negative
obligate aerobic
THEIR natural habitat is water - optimum temperature growth 25-42 degrees
PONTANIC FEVER due to lesser known legionella
what is the TRANSMISSION OF LEGIONELLA PNEUMOPHILIA?
inhalation of contaminated aerosols
- cold and hot water systems - like pipes
hottubs / swimming pools
air conditioning
person to person transmission is UNCOMMON
LOCATION particular risk for outbreak - nursing homes
hospitals - nosocomial
CRUISE SHIP / hotels
what are the PATHOGENESIS LEGIONNAIRES?
legionella enter the respiratory tract where they adhere to the respiratory tract
in damaged epithelium such as smokers or alcoholism - this adherence is more facilitated
bacteria taken up by phagocytosis - replicate very fast intracellularly - host cell bursts
what is the INCUBATION PERIOD OF LEGIONNAIRES DISEASE ?
2-10 days
CLINICAL FEATURES OF LEGIONNAIRES DISEASE ?
fever and chills and headache
severe pneumonia -
unilateral lobar pneumonia
atypical pneumonia - dry cough initially
dyspnea and bilateral crackles (legionnaire disease always considered in atypical PNEUMONIA!!)
fever then transforms into highly febrile with productive cough
DIARRHEA
neurological - confusion , agitation - ataxia , speech difficulties
extra pulmonary legionellosis rare - and in immunocompromised
Failure to respond to beta-lactam monotherapy
what are the clinical features of Pontiac fever ?
mild self limiting course of legionellosis WITHOUT
acute PNEUMONIA so mild fever headache myalgia
what are the clinical features of Pontiac fever ?
mild self limiting course of legionellosis WITHOUT PNEUMONIA
occurs usually in epidemics - with high attack rate
acute PNEUMONIA so mild fever headache myalgia
what is the DIAGNOSIS OF LEGIONNAIRE DISEASE ?
chest x ray
culture - requires specialised media - GOLD STANDARD requires buffered (iron and cysteine) charcoal yeast extract agar (results after 3–5 days)
urine antigen testing - highly specific - legionella soluble antigen testing
PCR and immunofluorescence
serum antibody detection - 4 fold rise in titres considered positive - but the antibody titers have low specificity and sensitivity, and seroconversion can take up to 12 weeks.
what is the the TREATMENT OF LEGIONNAIRE DISEASE ?
if untreated mortality equal to 20 percent
intracellular organisms - - specific antibiotics
fluroquinilones - levofloxacin - alternatively macrolides - azithro(10-14 days for macrolide)
LEGIONELLA are RESISTANT TO CEPHALOSPORINS
what is PSITTACOSIS OR ORNITHOSIS caused by ?
chlamydophila psittaci
what is the TRANSMISSION OF CHLAMYDIA PSITTACI?
airborne - pathogens are from feces or dander of infected birds
Chlamydophila psittaci accumulates
Psittacosis is a notifiable disease and should be reported in most of the states.
what is the INCUBATION PERIOD OF CLAMYDIA PSITTACI?
5-14 days
what are the CLINICAL FEATURES OF CLAMYDIA PSITTACI?
Acute onset of flu-like symptoms, especially fever
Atypical pneumonia with non-productive cough
Headaches
Arthralgia, myalgia
DIAGNOSIS OF CLAMYDIA PSITTACI?
Culture of respiratory specimens (e.g., sputum, pleural fluid)
Polymerase chain reaction (PCR) of respiratory specimens
Serology for Chlamydophila psittaci IgG and IgM with the complement-fixation test (CFT) or micro-immunofluorescence (MIF);
-diagnosis requires either of the following:
Four-fold or greater increase in antibody titer between acute and convalescent sera
A single IgM antibody titer of 1:16 or higher
