Dilution factor of quantitative bacterial cultures obtained by bronchoalveolar lavage in patients with ventilator-associated bacterial pneumonia

George L. Drusano*, Michael L. Corrado, Gino Girardi, Evelyn J. Ellis-Grosse, Richard G. Wunderink, Helen Donnelly, Kenneth V. Leeper, Mona Brown, Tasnova Malek, Robert Duncan Hite, Michelle Ferrari, Danijela Djureinovic, Marin H. Kollef, Lisa Mayfield, Ann Doyle, Jean Chastre, Alain Combes, Thomas J. Walsh, Krisztina Dorizas, Hassan AlnuaimatBrooks Edward Morgan, Jordi Rello, Cristopher Alan Mazo Torre, Ronald N. Jones, Robert K. Flamm, Leah Woosley, Paul G. Ambrose, Sujata Bhavnani, Christopher M. Rubino, Catharine C. Bulik, Arnold Louie, Michael Vicchiarelli, Colleen Berman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Ventilator-associated bacterial pneumonia (VABP) is a difficult therapeutic problem. Considerable controversy exists regarding the optimal chemotherapy for this entity. The recent guidelines of the Infectious Diseases Society of America and the American Thoracic Society recommend a 7-day therapeutic course for VABP based on the balance of no negative impact on all-cause mortality, less resistance emergence, and fewer antibiotic treatment days, counterbalanced with a higher relapse rate for patients whose pathogen is a nonfermenter. The bacterial burden causing an infection has a substantial impact on treatment outcome and resistance selection. We describe the baseline bronchoalveolar lavage (BAL) fluid burden of organisms in suspected VABP patients screened for inclusion in a clinical trial. We measured the urea concentrations in plasma and BAL fluid to provide an index of the dilution of the bacterial and drug concentrations in the lung epithelial lining fluid introduced by the BAL procedure. We were then able to calculate the true bacterial burden as the diluted colony count times the dilution factor. The median dilution factor was 28.7, with the interquartile range (IQR) being 11.9 to 53.2. Median dilution factor-corrected colony counts were 6.18 log 10 (CFU/ml) [IQR, 5.43 to 6.46 log 10 (CFU/ml)]. In a subset of patients, repeat BAL on day 5 showed a good stability of the dilution factor. We previously showed that large bacterial burdens reduce or stop bacterial killing by granulocytes.

Original languageEnglish (US)
Article numbere01323
JournalAntimicrobial agents and chemotherapy
Volume62
Issue number1
DOIs
StatePublished - Jan 2018

Keywords

  • Bacterial burden
  • Bronchoalveolar lavage
  • Ventilator-associated bacterial pneumonia

ASJC Scopus subject areas

  • Pharmacology
  • Pharmacology (medical)
  • Infectious Diseases

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