Pörnull K J, Rodrigo G, Dornbusch K
Department of Clinical Microbiology, Karolinska Hospital, Stockholm, Sweden.
J Antimicrob Chemother. 1994 Dec;34(6):943-54. doi: 10.1093/jac/34.6.943.
A septicaemia Klebsiella pneumoniae isolate from Greece (Ath1) was shown to be resistant to third generation cephalosporins, aztreonam and cefoxitin and this resistance was not decreased in the presence of clavulanic acid. The gene coding for the resistance phenotype, associated with a beta-lactamase showing cephalosporinase activity and a pI of 8.6, could be transferred into Escherichia coli K-12 by conjugation and transformation. DNA-hybridisation showed that this gene was located on two different plasmids, 7.8 and 80 kb respectively. The larger, conjugative plasmid also carried genes coding for another beta-lactamase (pI 6.6) and resistance to aminoglycosides, tetracycline, chloramphenicol and trimethoprim. Under highly stringent conditions the gene coding for the pI 8.6 beta-lactamase hybridised with chromosomal DNA from Citrobacter freundii OS60 but not from E. coli or Enterobacter cloacae. Furthermore, the restriction map of this beta-lactamase gene corresponded to that of ampC from C. freundii OS60. The regulatory ampR gene could not be detected in the plasmid DNA from the Ath1 K. pneumoniae by DNA hybridisation. The relationship between a plasmid-mediated extended spectrum beta-lactamase in a K. pneumoniae septicaemia isolate and chromosomal AmpC beta-lactamase from C. freundii was demonstrated.
从希腊分离出的一株肺炎克雷伯菌败血症菌株（Ath1）对第三代头孢菌素、氨曲南和头孢西丁耐药，且在克拉维酸存在的情况下这种耐药性并未降低。编码该耐药表型的基因与一种显示头孢菌素酶活性、等电点为8.6的β-内酰胺酶相关，可通过接合和转化转移到大肠杆菌K-12中。DNA杂交显示该基因分别位于两个不同的质粒上，大小分别为7.8 kb和80 kb。较大的接合性质粒还携带编码另一种β-内酰胺酶（等电点6.6）以及对氨基糖苷类、四环素、氯霉素和甲氧苄啶耐药的基因。在高度严格的条件下，编码等电点8.6的β-内酰胺酶的基因与弗氏柠檬酸杆菌OS60的染色体DNA杂交，但不与大肠杆菌或阴沟肠杆菌的染色体DNA杂交。此外，该β-内酰胺酶基因的限制性图谱与弗氏柠檬酸杆菌OS60的ampC基因的图谱一致。通过DNA杂交在肺炎克雷伯菌Ath1的质粒DNA中未检测到调控性ampR基因。证实了肺炎克雷伯菌败血症菌株中质粒介导的超广谱β-内酰胺酶与弗氏柠檬酸杆菌染色体AmpCβ-内酰胺酶之间的关系。
