Respiratory Tract Infections: Bacterial Infections Flashcards
Pneumonia
Infective inflammation and consolidation of the lung
Lower respiratory tract infection
Shadowing present on x ray
Classification of pneumonia
Pathological-> how infections spreads-> broncho, lobar
Microbiological-> causative organism determined by microbiology
Clinical classification-> circumstances surrounding development of e disease-> community acquired, hospital acquired, special environment, immunosuppressed, aspirational
Community acquired pneumonia
Major cause of morbidity and morality
More common in-> males, the elderly, alcoholics, chronic disease
Conventional bacteria cause 60-80%
Atypical 10-20%
Virus 10-20%
Don’t wait for culture treat on basis of what pathogen is likely to be
Bacteria that cause community acquired
Usually gram positive
S. Pneumoniae-> 1/3 of cases, occurs in the previously well, 25% morality rate, resistance to penicillin is becoming common
H.influenzae-> occurs in those with history of resp disorders
capsulated-> primary cause in children who haven’t received HiB vaccine
non capsulated-> disease in COPD
M.pneumoniae-> second most common cause, can cause an epidemic, has characteristic features, can be deadly
C.pneumonia-> neonates and elderly
L.pneumonia-> sporadic and outbreaks, severe disease in immune compromised and smokers
Investigations of CAP
Confirm diagnosis and asses severity-> temperature, FBC, urea, electrolytes, LFTS, chest X-ray, blood gases
Microbiological investigations-> use easily accessed samples. Sputum analysis and culture, immunofluorescense (viral), blood cultures, urinary pneumococcal and legionella antigen-> more severe
Management of CAP
Correction or resp failure
Correction of haemodynamic compromise
Specific anti microbial therapy-> based on likely pathogen, severity, likelihood of drug resistance (low in CAP)
Criteria of severe CAP
Confusion if new
Urea >7mmol/l
Resp rate >30 per minute
Systolic 64 years
Hospital acquired pneumonia
Defined as that which occurs two days or more after admission to hospital
5% of all patients admitted to hospital
Mainly due to gram negative bacteria
Predisposed by-> old age, serious illness, smoking! decreased lung defences (reduced conciousness, anaesthetics), mechanical ventilation
Causes of HAP
E.coli Klebsiella spp Proteus spp S. Pneumonia S.aureus-> MSSA, MRSA
Risk of MRSA
Previous MRSA infection/colonisation
Treated as an in patient within six months
Resident of nursing home with skin breaks
Indwelling line (penetrates skin)
If yes treat as MRSA
Aspiration pneumonia
Inhalation of a foreign body
Usually associated with regurgitation
Gastric acid causes chemical pneumontitis-> adult respiratory distress syndrome
Foreign body excites foreign body histolytic response and organisms from oropharynx cause infection
May develop lung abscesses
Mycoplasma
Atypical pneumonia Young patient Long prodrome Patchy consolidation on CXR Prominent extra pulmonary disease
Legionellosis
Exposure to contain instead water or air conditioning Severe CAP outbreak Multiple lobe involvement on CXR Hyponatraemia Focal neurological disease Check for legionella antigen
S. Aureus
CAP during influenza outbreak may be caused by S. Aureus
Necrotising pneumonia
Abscesses
Cystic fibrosis
Airways chronically infected with bacteria (s.aureus and p.aeruginosa)
Symptoms are persistent and progressive but subjective to acute exacerbations
Diagnosis of exacerbation is made on clinical grounds
Selection of antimicrobials guided by sputum cultures
Should include two agents active against P.aurginosa
