Approach

Start empirical intravenous antibiotics while cultures are pending in patients with typical clinical presentations and radiological findings of lung abscess, regardless of whether the presentation is acute, sub-acute, or chronic.[40]​ Antibiotic therapy should start immediately. Given the difficulties in detecting anaerobes, most patients should receive empirical antibiotics that cover mixed microbial flora. Chest physiotherapy and postural drainage may help with treatment. Surgical intervention is reserved for cases with non-resolving abscesses (particularly if associated with empyema), resistance to medical treatment, significant haemorrhage, or large abscesses.[10]

Antibiotics

There is no clear consensus on the preferred antibiotic regimen or duration for lung abscesses, with few controlled comparisons in the literature and wide variations in local protocols. In clinical practice, however, the choice of antibiotic often depends on whether a gram-negative or multi-drug resistant organism is suspected, with treatment usually given for at least 6 to 8 weeks.

Gram-negative organisms are likely in lung abscesses that follow pneumonia, immunosuppression, or necrotising pneumonia (after oropharyngeal colonisation), or if the abscess is hospital-acquired.

Multi-drug resistant organisms are likely if broad-spectrum antibiotic use or colonisation by resistant bacteria have been documented, or if the local epidemiology is suggestive. Local susceptibility patterns and microbiology sensitivities (when received) are key to their treatment.

Empirical antibiotics

  • Ampicillin/sulbactam or amoxicillin/clavulanate: ampicillin/sulbactam is reported to be equivalent to clindamycin with or without a cephalosporin in terms of tolerance and efficacy.[41][42]

  • Clindamycin plus a second- or third-generation cephalosporin: clindamycin is probably superior to penicillin, but as the spectrum of clindamycin is restricted to gram-positive microbes, combination with a second- or third-generation cephalosporin is required.[43][44][45]​ Such combinations are useful when gram-negative organisms are expected (e.g., Pseudomonas aeruginosa). Due to limited data in lung abscesses, this recommendation is based on experience gained from the treatment of aspiration pneumonia and the reported changing epidemiology of adult community-acquired lung abscess.[5][41]

  • Piperacillin/tazobactam or ticarcillin/clavulanate: Piperacillin/tazobactam is highly active against mixed bacterial flora, and is more potent against P aeruginosa than ticarcillin/clavulanate.

  • Carbapenems: imipenem/cilastatin, meropenem, and ertapenem are effective in treating mixed microbial flora. Their use should be reserved for cases where microbial multi-resistance is expected. They are particularly useful for the treatment of infections due to Acinetobacter species. Ertapenem is not appropriate if P aeruginosa or Acinetobacter species are suspected.

  • Penicillin plus metronidazole: resistance patterns seen in lung abscess mean that this regimen should not be given to patients at high risk of microbial multi-resistance. Metronidazole is added due to the observed failure of penicillin when treating penicillin-resistant Prevotella melaninogenica, Porphyromonas asaccharolytica, and Bacteroides species. Metronidazole should never be given alone because it is inactive against micro-aerophilic strains, aerobic streptococci, and Actinomyces species.[17] Note that disulfiram-like reactions may occur if metronidazole is given to alcoholic patients. 

  • Patients allergic to penicillin and cephalosporins may be treated with clindamycin plus aztreonam, ciprofloxacin, or levofloxacin to cover of gram-negative pathogens. Although there are no specific data on the use of these combinations in lung abscess, they are effective against infections due to mixed bacterial flora.[46]

Targeted antibiotics

  • Once culture results are available, antibiotics should be tailored to the reported sensitivities of the grown culture.

Chest physiotherapy and postural drainage

Patients with a large lung abscess should be placed in the lateral decubitus position with the abscess side down. This may prevent the sudden discharge of abscess content causing asphyxiation or spread of the infection to other lung segments. Chest physiotherapy and postural drainage may improve clearance of the purulent and necrotic abscess contents, but, as published evidence is scarce, this remains debatable.

Surgical intervention

Perform interventional drainage in patients with non-resolving abscesses (particularly if associated with empyema), resistance to medical treatment, significant haemorrhage, or large abscesses (>6 cm).[10][47][48][49][50]​​ All procedures should be performed by an appropriately trained consultant in a properly equipped facility.

  • Video-assisted thoracoscopy: a less invasive approach than resection.[51]

  • Resection of the affected lobe or segment: reserve for patients not responding to antibiotics and other therapies. More likely to be needed for patients with large cavities, massive haemorrhage, concomitant pleural empyema, obstructive neoplasms, or infections caused by multi-drug resistant bacteria or fungi.[52] Survival rates after lung resection range from 89% to 95%.

  • Percutaneous CT scan or ultrasound-guided drainage: this procedure has superior outcomes but similar complication rates compared with conservative management.[53]​ One meta-analysis revealed that drainage appears both effective (success rate, 86.5%) and safe (major complication rate, 8.1%).[54]​ Failure mainly occurred due to major complications, which themselves arose from an inability to traverse the normal lung parenchyma (e.g., in malignancy).[54]​ Indications include clinical suspicion of infected fluid or a fistula, a need to characterise the fluid, concern that the collection is responsible for sepsis or other symptoms, and when needed for additional therapy or interventions.[55]​ No absolute contraindications exist, but relative contraindications include significant coagulopathy, severely compromised cardiopulmonary function, lack of safe access, patient non-compliance, and an inability to position the patient correctly.[32][33][55]​​[56][57]​​​​

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