Carbenicillin‐Hydrolyzing Penicillinases of Proteus mirabilis and the PSE‐Type Penicillinases of Pseudomonas aeruginosa

Abstract

Three carbenicillin-hydrolyzing penicillinases were found in Proteus mirabilis strains, N-3, N-29, and GN79. The former two strains were isolated in 1978, but strain GN79 was one of our stock cultures isolated in 1965. These penicilIinases closely resembled each other, and the PSE-l and PSE-4 enzymes produced by Pseudomonas aeruginosa, in their substrate profiles and kinetic properties for hydrolyzing various tJ-lactams. However, differences were found in their molecular weights and isoelectric points which ranged from 22,000 to 27,000 and from 6.0 to 6.9, respectively. The antiserum against the purified penicillinase of N-29 cross-reacted with the enzyme of N-3 and inhibited its activity by more than 80%. The antiserum also reacted with the PSE-l and PSE-4 enzymes. The antiserum did not react with the penicillinase from strain GN79 and the PSE-2 and PSE-3 enzymes of P. aeruginosa, Enzyme production in N-3 and N-29 was mediated by R plasmids.Many .B-lactamases [EC 3.5.2.6] mediated by chromosomal gene(s) or those carried on plasmids have been extensively studied by many workers (4,23). These enzymes have been classified according to such properties as substrate specificity, interaction with inhibitors and inactivators, isoelectric point, molecular weight, and immunochemical properties. There are two major groups of .B-lactamases, i.e. the penicillinase type and cephalosporinase type. In gram-negative rod bacteria, most of the penicillinases are genetically governed by R plasmids. Among these, penicillinases mediated by R plasmids occurring predominantly in Pseudomonas aeruginosa are known to effectively hydrolyze carbenicillin (11). The enzymes were termed PSE (Pseudomonas-specific enzymes), and were divided into four subgroups, i.e., PSE-l, PSE-2, PSE-3, and PSE-4, by Hedges and Matthew (10). However, recently, Medeiros et al (16) demonstrated that PSE-l enzymes mediated by R plasmids were spread among enteric bacteria such as Escherichia coli, Salmonella enteritidis, and Shigella sonnei, and Katsu et al (12) have reported PSE-l enzymes mediated by R plasmids in Proteus mirabilis.We also found that the penicillinase of P. mirabilis GN79 had the same characteristics as carbenicillin-hydrolyzing penicillinase (carbenicillinase). This strain was isolated in 1965 (26) and the penicillinase was considered to be a species-specific 995

Nucleotide sequence and characterization of a carbenicillin-hydrolyzing penicillinase gene from Proteus mirabilis

“…As shown in Table 1, the E. coli strains carrying the recombinant plasmids showed high resistance to ampicillin and carbenicillin but were susceptible to cephalosporins. This susceptibility pattern is similar to that found for E. coli cells producing an R-plasmid-mediated carbenicillinase (30). The cephalosporin resistance of P. mirabilis GN79 is believed to be intrinsic, because we did not find detectable cephalosporin hydrolysis activity in the * Corresponding author.…”

“…The pPM79P1 enzyme and the GN79 enzyme showed identical isoelectric point values, 6.6, this value being obviously different from those of carbenicillinases mediated by naturally occurring R plasmids in P. mirabilis, pCS203 (30) and pCS229 (30) (Fig. 1).…”

“…Strain GN79 produces a constitutive P-lactamase with the characteristics of a carbenicillinase, and the enzyme could be distinguished from the PSE-1, -3, and -4 enzymes by its substrate profile and its nonreactivity with the antiserum against a plasmidmediated carbenicillinase (30). The enzyme production by the GN79 strain is hereditarily stable, and progeny lacking the enzyme could not be isolated even though many possible treatments for plasmid elimination were tried, suggesting that the enzyme may be mediated by a chromosomal gene.…”

Nucleotide Sequence of the bla RTG-2 (CARB-5) Gene and Phylogeny of a New Group of Carbenicillinases

“…However, despite their sequence identities, the ␤-lactamase neutralization assay for CARB-5 with anti-CARB serum gave results in conflict with those obtained for GN79 in the original study. The P. mirabilis GN79 ␤-lactamase was not neutralized by serum raised against the P. mirabilis N29 ␤-lactamase, which fully neutralized PSE-1 and PSE-4 (27). In contrast, CARB-5 was inhibited by anti-CARB-3 serum that also reacts with other CARB enzymes, including PSE-1 and PSE-4.…”

Novel β-Lactamase Genes from Two Environmental Isolates of Vibrio harveyi

“…A phylogenetic tree was also constructed by using the Treecon for Windows version 1.3b software package (33). Deduced amino acid sequences for pVHA1 and pVHA4 were compared to 13 other class A ␤-lactamases: PSE-1, PSE-4, CARB-3 from Pseudomonas aeruginosa (3,13,14), CTX-M-5, CTX-M-3 from Salmonella enterica serovar Typhimurium (4; M. Gazouli, unpublished data), AER-1 from Aeromonas hydrophila (25), CARB-6 from Vibrio cholerae (6), ROB-1 from Actinobacillus pleuropneumoniae (5), Bacillus thuringiensis ␤-lactamase (36), Streptomyces fradiae Y59 ␤-lactamase (20), OXY-2 from Klebsiella oxytoca (8), Serratia marcescens S5 ␤-lactamase (20), and ␤-lactamase from Proteus mirabilis N-29 (31). The identification of signal peptides was carried out with the program SignalP V1.1 at the Center for Biological Sequence Analysis over the Internet (http://www .cbs.dtu.dk/services/SignalP/) (19).…”