Effects of beta-lactamases and omp mutation on susceptibility to beta-lactam antibiotics in Escherichia coli

Abstract

omp mutants, MH1160 (MC4100 ompRI) and MH760 (MC4100 ompR2), by transformation. Effects of the combination of the omp mutations and these P-lactamases on the susceptibility of E. coli strains were studied with 15 ,B-lactam antibiotics including cephalosporins, cephamycins, penicillins, imipenem, and aztreonam. The ompRI mutant, MH1160, lacks OmpF and OmpC, and it showed reduced susceptibility to 11 of the 15 P-lactam agents. The reduction in susceptibility to cefoxitin, moxalactam, and flomoxef was much greater than reduction in susceptibility to the other agents. When the ompRI mutant produced the cephalosporinase of C. freundii, the susceptibility of the mutant to 12 of the 15 P-lactam antibiotics decreased. The reduction in susceptibility of MH1160 to 10 of the 12 agents affected by the enzyme was two-to fourfold greater than that observed in MC4100. Such a synergistic effect was also observed with the cephalosporinase of P. vulgaris and ompRI mutation against six cephalosporins, moxalactam, and aztreonam.P-Lactamases of gram-negative bacteria play an important part in bacterial resistance to P-lactam antibiotics. They are mediated by chromosomes or by plasmids. Both expression of P-lactamases, i.e., amount of the enzymes, and substrate profiles of the enzymes are major factors that determine resistance levels. Also, permeability of r-lactam antibiotics through the bacterial outer membrane affects susceptibility to r-lactam agents (21). Since OmpF and OmpC porins of Escherichia coli were found to act as pores for diffusion through the outer membrane, the role of the porin channels in permeation of r-lactams has been studied actively (24, 29). Some P-lactam antibiotics, e.g., cefoxitin, are known to penetrate much more rapidly through the OmpF porin than through the OmpC porin (11). Decreased permeability of the outer membrane and alterations in the outer membrane proteins also have been studied as factors in resistance to P-lactam antibiotics (1,6, 12). Recently, the contributions of 1-lactamases and outer membrane permeability to resistance have been studied simultaneously (15,20,27). Such an approach is more appropriate when both hydrolytic rate and permeation rate are slow (5). In our studies on bacterial resistance to newer cephalosporins by cephalosporinases, a decrease in permeability intensified the reduction in antimicrobial activity by cephalosporinase against cefotaxime and ceftazidime in E. coli (7,8

Mechanism of tonB-dependent transport of KP-736, a 1,5-dihydroxy-4-pyridone-substituted cephalosporin, into Escherichia coli K-12 cells

“…However, pathogenic bacteria can easily develop high levels of resistance to ␤-lactams by both the loss of porin proteins and the high-level production of ␤-lactamases (6,20). Indeed, Hiraoka et al (25) demonstrated that porin-deficient mutants showed high levels of resistance to ␤-lactams compared with the resistance of the wild-type strain when a large amount of active ␤-lactamase existed in the periplasm. However, the activity of KP-736 was less affected by the combined effect of porin loss and ␤-lactamase production.…”

“…MH1160 is an ompR1 mutant of MC4100 and lacks the outer membrane proteins OmpF and OmpC (25), while MC4100 has an osmoregulated production of OmpF and OmpC (25). Transformants of MH1160 and MC4100 with pMS510, pMS509, pMS185-2, or pMS182-5 plasmid DNA (25), which contain cloned ␤-lactamase genes of the types penicillinase group 2b (TEM-1) of Rms212 (57), penicillinase (PCase) group 2d (OXA-1) of Rms213 (57), cephalosporinase (CSase) group 1 of Citrobacter freundii GN346 (52), and oxyimino-cephalosporinase (CXase) group 2e of Proteus vulgaris GN7919 (36), respectively, were maintained as stock cultures in our laboratory (25). pMS363 plasmid DNA (30), which contains the cloned ␤-lactamase gene of CXase group 3 of P. aeruginosa GN17203, was provided by S. Iyobe, Gunma University, Gunma, Japan (30).…”

Resistance to cefoperazone-sulbactam in Klebsiella pneumoniae: evidence for enhanced resistance resulting from the coexistence of two different resistance mechanisms

“…In this scenario, an alteration in the permeability of the outer membrane to the P-lactam or the inhibitor in the presence of a stable level of ,B-lactamase production would be expected to result in an elevation of the in vitro MIC. Such a phenomenon has been described for E. coli in association with the loss of certain porin proteins (6,19).…”

“…The most common mechanism appears to be production of high levels of a 1-lactamase normally susceptible to the inhibitor (10,11,16,20). Increased resistance has also been associated with the loss of expression of certain porin proteins in Escherichia coli (6,19). Other reported mechanisms include the production of a ,B-lactamase normally resistant to the inhibitor, such as the AmpC-type enzymes (3,15), or mutations in a normally inhibited enzyme rendering it resistant to inhibition (3).…”

Increased resistance to multiple drugs by introduction of the Enterobacter cloacae romA gene into OmpF porin-deficient mutants of Escherichia coli K-12

“…In Escherichia coli K-12, the major outer membrane porins are OmpF and OmpC. Mutants lacking OmpF porin have increased resistance to 3-lactams, chloramphenicol, quinolones, and tetracyclines (2, 4-6, 8,10,11,18,27). Moreover, in vitro studies using liposomes revealed that the OmpF porin formed much more efficient pores for the diffusion of 1-lactams than OmpC porin (20,21).…”