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Several recombinant cowpox viruses were constructed and used to identify a viral gene that controls the production of hemorrhage in lesions caused by the Brighton Red strain of cowpox virus (CPV-BR). This gene is located in the KpnD fragment of CPV-BR DNA, between 31 and 32 kilobases from the end of the genome. This position corresponds well with that predicted from analyses of the DNA structures of spontaneously generated deletion mutants. The gene responsible for hemorrhage encodes a 38-kDa protein that is one of the most abundant early gene products. The 11-basepair sequence GAAAATATATT present 84 base pairs upstream of its coding region is also present upstream of three other early genes of vaccinia virus; therefore, this sequence may be involved in the regulation of transcription. There is extensive similarity between the predicted amino acid sequence of the 38-kDa protein and the amino acid sequences of several plasma proteins that are inhibitors of various serine proteases involved in blood coagulation pathways. This suggests that the viral protein may possess a similar biological activity, which may enable it to effect hemorrhage by inhibiting one or more of the serine proteases involved in the host's normal processes of blood coagulation and wound containment.The inoculation of cowpox virus (CPV) into the skin of various mammals (guinea pigs, rabbits, humans) results in lesions that exhibit edema, hypertrophy ofthe epidermis, and hemorrhage. Similar effects are produced in CPV lesions (pocks) in the chorioallantoic membrane of developing chicken embryos; there is extensive proliferation of ectodermal and mesodermal cells, edema, and localized hemorrhage that gives the pocks a deep red color (1).CPV variants that do not produce hemorrhage have been isolated from the white pocks that usually comprise up to 1% of the pocks present on chorioallantoic membranes infected with wild-type CPV (2, 3). The existence of these white-pock variants demonstrates that a viral function controls the production of the hemorrhage.Studies of the structures of the DNAs of these white-pock variants have shown that their genomes are generated from the genome of the wild-type virus by large deletions and duplications of sequences (4, 5). Similar results have been obtained from studies of the DNAs of white-pock variants of rabbitpox virus and monkeypox virus (6-8). The rearrangements of DNA that generate the white-pock variants of CPV typically involve the replacement of up to 39 kilobases (kb) of one end of the genome with an inverted copy of up to 50 kb of DNA from the other end (4, 5). The mechanisms by which these rearrangements proceed are unknown; but it is clear that there are no identifiable homologous sequence elements at the sites of the duplication/deletion end points (5). This result suggests that it is the location of essential genes rather than DNA sequence content that limits where rearrangements may occur. The position ofgenes that encode markers, such as production of hemorrhage, will place a further cons...

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We investigated the mechanisms involved in imipenem resistance in 23 clinical strains of Acinetobacter baumannii. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the presence of a 30-kDa protein in imipenem-intermediate A. baumannii (IIAB) and imipenem-resistant A. baumannii (IRAB) strains; this protein was almost undetectable in imipenem-susceptible A. baumannii (ISAB) strains. The 30-kDa protein was identified as an OXA-51-like carbapenemase using two-dimensional gel electrophoresis and mass spectrometry. Similar to other recent findings, bla OXA-51-like genes were found to exist in all 23 clinical strains; however, the transcript levels of bla OXA-51-like in the IIAB and IRAB were higher than in the ISAB strains using reverse transcriptase PCR (RT-PCR) and real-time RT-PCR assays. This change was due to the presence of an insertion sequence, ISAba1, upstream of bla OXA-51-like in the IIAB and IRAB strains that was not present in the ISAB strains. The introduction of bla OXA-66 (a bla OXA-51-like gene), identified in ISAB ab1254 and IRAB ab1266, into Escherichia coli TOP10 cells resulted in 3.95-fold and 7.90-fold elevations in resistance to imipenem, respectively. Furthermore, when ISAB ab8 and ISAB ab1254 and their in vitro-selected imipenem-resistant mutants ISAB ab8(r) and ISAB ab1254(r) were compared, the results showed no change in the bla OXA-66 /bla OXA-51-like gene sequences, in expression of the gene, and in the outer membrane protein profiles. However, there was a four-to eightfold reduction in imipenem resistance upon adding carbonyl cyanide m-chlorophenylhydrazone. Taken together, these results suggest that the OXA-66/OXA-51-like carbapenemase contributes to intrinsic resistance to imipenem; however, drug export by an efflux pump may be more important and/or occur more frequently in imipenem-resistant A. baumannii. Furthermore, this is the first report of a Taiwanese strain of an OXA-66/OXA-51-like carbapenemase that confers imipenem resistance in A. baumannii.Acinetobacter baumannii accounts for a large percentage of nosocomial infections including pneumonia, bacteremia, skin infections, wound infections, and urinary tract infections (2, 19). Increasingly, multidrug resistance strains of A. baumannii have become common in hospitals worldwide and especially in intensive care units (10, 12, 30) and burn units (2,31,32,40). The types of resistance include many commonly used antibiotics such as aminoglycosides, fluoroquinolones, and ␤-lactams, although carbapenems are the most used antimicrobial drugs. However, an increasing number of recent studies reported the emergence of clinical A. baumannii strains that are resistance to imipenem (7,9,27).The mechanism of resistance to carbapenems in A. baumannii has mostly been ascribed to the acquisition of carbapenemases (1, 26) or to synergistic effects between ␤-lactamases with an ability to hydrolyze carbapenems and decreased expression of certain penicillin-binding proteins (13,14). The carbapenemases in A. baumannii ...