Hospital-Acquired Pneumonia

Hospital-acquired or nosocomial pneumonia refers to a new episode of pneumonia occurring at least 2 days after admission to hospital #Older people are particularly at risk #patients in intensive care units, especially when mechanically ventilated

Etiology (early-onset) HAP occurs within 4-5 days of admission ;the organisms involved are similar to those involved in CAP; (late-onset HAP) is more often attributable to Gram-negative bacteria (e.g. Escherichia, Pseudomonas and Klebsiella species), Staph. aureus (including methicillin-resistant Staph. aureus (MRSA)) and anaerobes.

Factors predisposing to hospital-acquired pneumonia Reduced host defenses against bacteria: (e.g. corticosteroid treatment, diabetes, malignancy) - Reduced cough reflex (e.g. post-operative) -Disordered mucociliary clearance (e.g. anaesthetic agents) Bulbar or vocal cord palsy Aspiration of nasopharyngeal or gastric secretions: Immobility or reduced conscious level -Vomiting, dysphagia, achalasia or severe reflux Nasogastric intubation

Bacteria introduced into lower respiratory tract Endotracheal intubation/tracheostomy- Infected ventilators/nebulizers/bronchoscopes Dental or sinus infection Bacteremia Abdominal sepsis I.v. cannula infection Infected emboli

Clinical features of suppurative pneumonia Symptoms Cough productive of large amounts of sputum which is sometimes blood-stained Pleural pain common Clinical signs High remittent pyrexia Profound systemic upset Digital clubbing may develop quickly (10-14 days) Chest examination usually reveals signs of consolidation; signs of cavitation rarely found Pleural rub common

INVESTIGATION Sputum CXR CBP @Invasive investigations such as bronchoscopy, BAL, trans bronchial biopsy or surgical lung biopsy are often impractical,. @HRCT is useful in differentiating the likely cause.

Management 1-a third-generation cephalosporin (e.g. cefotaxime) with an aminoglycoside (e.g. gentamicin) 2-meropenem or a monocyclic β-lactam (e.g. aztreonam) and flucloxacillin. 3-MRSA is treated with intravenous vancomycin, @ If an anaerobic bacterial infection is suspected (e.g. from fetor of the sputum), oral metronidazole 400 mg 8-hourly should be added.. @Prolonged treatment for 4-6 weeks may be required in some patients with lung abscess Physiotherapy is important in those who are immobile or old. Adequate oxygen therapy, fluid support, monitoring.

Prevention Despite appropriate management, the mortality from HAP is high at approximately 30%, Good hygiene including both hand washing and equipment. Steps should be taken to minimize the chances of aspiration and limit the use of stress ulcer prophylaxis with proton pump inhibitors. Oral antiseptic (chlorhexidine 2%) may be used to decontaminate the upper airway

Suppurative pneumonia, aspiration pneumonia and pulmonary abscess Suppurative pneumonia is characterized by destruction of the lung parenchyma by the inflammatory process and, although micro abscess formation is a characteristic histological feature, 'pulmonary abscess'

Pneumonia in the immunocompromised patient @Patients immunocompromised by drugs or disease are at high risk of pulmonary infection. @The majority of infections are caused by the same pathogens that cause pneumonia in non- immunocompromised individuals, but in patients with more profound immunosuppression, unusual organisms, or those normally considered to be of low virulence or non-pathogenic, may become 'opportunistic' pathogens @In addition to the more common agents, the possibility of Gram-negative bacteria, especially Pseudomonas aeruginosa, viral agents, fungi, mycobacteria,

Causes of immune suppression-associated lung infection  Defective phagocytic function Acute leukemia Gram-positive bacteria, including Staph. aureus Cytotoxic drugs Gram-negative bacteria Agranulocytosis Fungi, e.g. Candida albicans and Aspergillus fumigatus Defects in cell-mediated immunity Immunosuppressive drug-Lymphoma ( Cytomegalovirus-Herpes virus- Adenovirus-Influenza-Fungi -Pneumocystis jirovecii (formerly carinii)Candida albicans-Aspergillus fumigatus)) Defects in antibody production Multiple myeloma-Chronic lymphocytic leukemia ((Haemophilus influenza- Mycoplasma pneumonia)

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