Suspected gram-negative pneumonia in patients with VAP

For patients with VAP who have suspected gram-negative pneumonia, consider adding an aminoglycoside. Gram-negative pneumonia may be suspected:

• if gram-negative bacilli are identified on blood culture or culture of lower respiratory tract samples obtained by more invasive methods (eg endotracheal aspirate, bronchoalveolar lavage [BAL], mini-BAL)
• in patients with chronic suppurative lung disease (eg bronchiectasis) who have known respiratory colonisation with gram-negative pathogens, such as Pseudomonas aeruginosa.

The choice of aminoglycoside may be influenced by several factors, including:

• the spectrum of activity
• the availability of aminoglycoside therapeutic drug monitoring
• whether the laboratory reports aminoglycoside susceptibility
• drug cost.

There are limited clinical data to support tobramycin over gentamicin; however, the minimum inhibitory concentration (MIC) for tobramycin is slightly lower than gentamicin in vitro (particularly for P. aeruginosa) and has a greater likelihood of target attainment.

Generally, either gentamicin or tobramycin can be used in patients with VAP who have suspected gram-negative pneumonia but, in some patients, one aminoglycoside may be preferred to another:

• If gram-negative bacilli are identified on culture, either gentamicin or tobramycin is usually preferred to amikacin. However, the antibiotic susceptibility of resistant gram-negative bacteria varies. When choosing aminoglycoside, consider local epidemiology and whether the patient has risk factors for infection with a multidrug-resistant gram-negative bacterium. Also consider whether there is a risk of infection with a pathogen resistant to aminoglycosides – seek expert advice to guide antimicrobial choice but do not delay administration of an aminoglycoside in the interim. For amikacin dosing, see Amikacin initial dose calculator for adults or Initial aminoglycoside dosage for treating infection in children 1 month to younger than 18 years for children.
• For patients with chronic suppurative lung disease who have known respiratory colonisation with P. aeruginosa, tobramycin is preferred to gentamicin.
• For patients in whom infection with P. aeruginosa is considered likely, tobramycin is preferred to gentamicin.

Consider adding an aminoglycoside (gentamicin or tobramycin) to the empirical therapy regimen for VAP. In adults and children, use:

Review therapy at 24 to 48 hours and consider stopping the aminoglycoside based on the results of investigations – see Review of patients with VAP.