The virulence variability of different Acinetobacter baumannii strains in experimental pneumonia.
OBJECTIVE
Our objective was to compare the virulence of 5 strains of Acinetobacter baumannii by using a mouse model of pneumonia.


METHODS
Six-week old female C3H/HeN mice were used. The pneumonia was inducted by intra-tracheal inoculation of 5.10(6) bacteria. Spontaneous outcome was evaluated by mortality, mice weight variations, and a clinical score. Bacterial counts in lungs, spleen and blood, and inflammatory response in lungs (dosages of tumor necrosis factor-alpha and macrophage inflammatory protein-2) were also measured. Lastly, a histological examination of lungs was performed for 3 strains, giving a histological score.


RESULTS
Global mortality varied from 13% to 79% (P<10(-4)). Bacterial counts in lungs within the 4 days following inoculation varied significantly according to different strains. The evolution curves of bacterial counts were also different. There was a significant correlation between the clinical score and mortality (P<0.05) but not between bacterial counts in lungs and mortality. The increase of pro-inflammatory mediator production in lungs and the histological score also varied according to strains.


CONCLUSIONS
These results demonstrate the variability of the virulence between strains, and suggest that bacterial proliferation is not the only virulence factor responsible for the pathogenesis in A. baumannii pneumonia.
Eveillard
Matthieu
M
Groupe d'Etude des Interactions Hôtes-Pathogènes (GEIHP, UPRES EA 3142), UFR Médecine, Université d'Angers, France; Service de Bactériologie-hygiène, CHU Angers, 4 rue Larrey, 49000 Angers, France. MaEveillard@chu-angers.fr
Soltner
Christophe
C
Kempf
Marie
M
Saint-André
Jean-Paul
JP
Lemarié
Carole
C
Randrianarivelo
Catherine
C
Seifert
Harald
H
Wolff
Michel
M
Joly-Guillou
Marie-Laure
ML
D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000302:isolation & purification / Q000472:pathogenicity*; D000818:Animals; D001769:Blood / Q000382:microbiology; D001835:Body Weight; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D005260:Female; D014644:Genetic Variation; D006651:Histocytochemistry; D006801:Humans; D018836:Inflammation Mediators / Q000032:analysis; D008168:Lung / Q000737:chemistry / Q000382:microbiology / Q000473:pathology; D051379:Mice; D008809:Mice, Inbred C3H; D008853:Microscopy; D018410:Pneumonia, Bacterial / Q000382:microbiology*; D012720:Severity of Illness Index; D013154:Spleen / Q000382:microbiology; D016019:Survival Analysis; D014774:Virulence
D018836:Inflammation Mediators