Penicillin-binding protein 7/8 contributes to the survival of Acinetobacter baumannii in vitro and in vivo.
BACKGROUND
Acinetobacter baumannii is a bacterial pathogen of increasing medical importance. Little is known about genes important for its survival in vivo.


RESULTS
Screening of random transposon mutants of the model pathogen AB307-0294 identified the mutant AB307.27. AB307.27 contained its transposon insertion in pbpG, which encodes the putative low-molecular-mass penicillin-binding protein 7/8 (PBP-7/8). AB307.27 was significantly killed in ascites (P<.001), but its growth in Luria-Bertani broth was similar to that of its parent, AB307-0294 (P=.13). The survival of AB307.27 was significantly decreased in a rat soft-tissue infection model (P<.001) and a rat pneumonia model (P=.002), compared with AB307-0294. AB307.27 was significantly killed in 90% human serum in vitro, compared with AB307-0294 (P<.001). Electron microscopy demonstrated more coccobacillary forms of AB307.27, compared with AB307-0294, suggesting a possible modulation in the peptidoglycan, which may affect susceptibility to host defense factors.


CONCLUSIONS
These findings demonstrate that PBP-7/8 contributes to the pathogenesis of A. baumannii. PBP-7/8 either directly or indirectly contributes to the resistance of AB307-0294 to complement-mediated bactericidal activity. An understanding of how PBP-7/8 contributes to serum resistance will lend insight into the role of this low-molecular-mass PBP whose function is poorly understood.
Russo
Thomas A
TA
Veterans Administration Western New York Healthcare System, The Witebsky Center for Microbial Pathogenesis, Department of Medicine, State University of New York-Buffalo, Buffalo, New York 14214, USA. trusso@acsu.buffalo.edu
MacDonald
Ulrike
U
Beanan
Janet M
JM
Olson
Ruth
R
MacDonald
Ian J
IJ
Sauberan
Shauna L
SL
Luke
Nicole R
NR
Schultz
L Wayne
LW
Umland
Timothy C
TC
D000151:Acinetobacter Infections / Q000276:immunology* / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D000595:Amino Acid Sequence; D000818:Animals; D001770:Blood Bactericidal Activity; D003165:Complement System Proteins / Q000276:immunology; D003198:Computer Simulation; D004251:DNA Transposable Elements; D003627:Data Interpretation, Statistical; D004195:Disease Models, Animal; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D046915:Penicillin-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018410:Pneumonia, Bacterial / Q000276:immunology / Q000382:microbiology; D051381:Rats; D018461:Soft Tissue Infections / Q000276:immunology / Q000382:microbiology; D014556:Urine / Q000382:microbiology
D004251:DNA Transposable Elements; D046915:Penicillin-Binding Proteins; D003165:Complement System Proteins