Short Course of Antibiotics Insufficient for VAP

February 7, 2012 (Houston, Texas) — Eight days of antimicrobial therapy for ventilator-associated pneumonia (VAP) might not be enough when the infecting pathogens are nonlactose-fermenting Gram-negative bacilli (NLF-GNB), according to research presented here at the Society of Critical Care Medicine 41st Critical Care Congress.

Dr. Gina Shirah

"A shortened antibiotic course will frequently lead to persistent primary infection in patients with NLF-GNB ventilator-associated pneumonia," Gina Shirah, MD, from the Maricopa Medical Center in Phoenix, Arizona, said in an oral presentation.

Such patients need repeat bronchoalveolar lavage (BAL) during therapy to tailor duration of antimicrobial therapy, to reassess the effectiveness of treatment, and to determine changes in resistance profiles, Dr. Shirah explained.

"Half of our patients were found to be not treated, and half of our patients were also found to be not sensitive to the same antibiotics we had them on initially," she told Medscape Medical News after her presentation.

Suspecting that an 8-day course of antibiotics for NLF-GNB infection would be inadequate and result in persistent primary infection, Dr. Shirah and her team did a retrospective review of 77 patients with VAP who had originally been diagnosed with BAL and who underwent subsequent BAL during treatment at their level I trauma center over a 4.5-year time period.

Persistent primary infection was defined as a decrease of less than 2-log₁₀ in the initial species on subsequent BAL.

On average, the second BAL was done on day 7 of antibiotic therapy (range, day 3 to day 14). Forty-eight percent of subsequent BAL was done after more than 8 days of therapy.

The patients were classified into 2 groups. Group A was infected with NLF-GNB, and group B showed infection with Enterobacteriaceae, methicillin-resistant Staphylococcus aureus, and community-acquired pathogens including Haemophilus spp, methicillin-sensitive S aureus, and Streptococcus spp.

The study found persistent primary infection after 8 days of antimicrobial therapy in 69% of NLF-GNB patients. Pathogens identified included Pseudomonas aeruginosa and Acinetobacter baumannii.

In comparison, only 8% of group B patients showed persistent primary infection (P = .0004).

Additionally, in the NLF-GNB patients, 56% of the pathogens obtained on repeat BAL remained sensitive to the antimicrobial treatment.

"This is a very important topic," Todd Rice, MD, from Vanderbilt University Medical Center in Nashville, Tennessee, told Medscape Medical News.

"The literature about shortening duration of antibiotics for VAP suggested that these organisms were different, and the standard care in patients who have these organisms causing VAP is to treat longer," Dr. Rice noted.

"These data suggest that there is persistent infection at day 8, which is when we stop antibiotics in the ventilator-associated pneumonia caused by organisms other than these. The only real issue is that this 'persistent infection' is defined by microbiology 'failure' on bronchoalveolar lavage," he said.

Serial bronchoalveolar lavages are not routinely done in many patients or institutions, and it isn't clear if this microbiological definition of persistent infection is related to clinical outcomes, such as mortality, length of stay in the intensive care unit or hospital, and duration of ventilator support, Dr. Rice continued.

"These things would need to be evaluated and then probably confirmed in a prospective randomized clinical trial."

Dr. Shirah and Dr. Rice have disclosed no relevant financial relationships.

Society of Critical Care Medicine (SCCM) 41st Critical Care Congress: Abstract 44. Presented February 5, 2012.