Respiratory Tract Infections: Bacterial Infections Flashcards Preview

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Flashcards in Respiratory Tract Infections: Bacterial Infections Deck (17)

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



Infective inflammation and consolidation of the lung
Lower respiratory tract infection
Shadowing present on x ray


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

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



Atypical pneumonia
Young patient
Long prodrome
Patchy consolidation on CXR
Prominent extra pulmonary disease



Exposure to contain instead water or air conditioning
Severe CAP outbreak
Multiple lobe involvement on CXR
Focal neurological disease
Check for legionella antigen


S. Aureus

CAP during influenza outbreak may be caused by S. Aureus
Necrotising pneumonia


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


Chronic bronchitis

Functional disorder
Cough productive of sputum on most days for 3 months of the year for at least 2 successive years
Excessive mucous secretion-> increased risk of infection



Persistent sputum
Breathless on exertion
Pathology of chronic bronchitis and emphysema
Asthma symptoms
-> life time smoking exposure, child hood asthma
Acute episodes of infection-> decline in lung function
Prophylactic vaccine against pneumococcal and influenza

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