The Association of Escherichia coli Virulence and Pulmonary Microvascular Damage

Bacterial virulence indicates the degree of pathogenicity of a given strain of microbe for a given host. The effect of Escherichia coli virulence on lung microvascular permeability was studied in sheep with chronic pulmonary lymph fistulas following peritoneal contamination. The study was divided into four groups: (1) wild-type E coli (WT group, 2.5× 10₉ colony-forming units [CFUs]/kg); (2) virulent E coli (PV group, 2.3×10₉CFUs/kg); (3) nonvirulent E coli (PNV group, 2.6× 10₉ CFUs/kg); (4) high-inoculum wild-type E coli (HIWT group, 6.1 × 10₉ CFUs/kg). In the late period (two to six hours), the increase in lung lymph flow in the PV group was significantly greater than the WT, PNV, and HIWT groups, with no difference noted among groups with respect to the pulmonary artery pressure, pulmonary wedge pressure, or albumin lymph/plasma ratio. It was concluded that (1) increased E coli virulence results in increased lung microvascular damage and (2) increased lung microvascular damage as a function of E coli virulence may not be solely due to increased bacterial numbers as a function of time.