Chromosomal beta-lactamase expression and resistance to beta-lactam antibiotics in Proteus vulgaris and Morganella morganii

Abstract

Indole-positive members of the Proteeae usually have inducible expression of chromosomal ,-lactamases.Mutants with stably derepressed P-lactamase expression occur in inducible populations at frequencies in the range of 10-6 to 10-8. The contribution of these P-lactamases to drug resistance was examined in Morganella morganii and Proteus vulgaris. The M. morganii enzyme was a high-molecular-weight (49,000) class I cephalosporinase with low Vm.x rates for ampicillin, carbenicillin, and broad-spectrum cephalosporins. The P.vulgaris enzyme had a lower molecular weight (32,000) and high Vmax rates for ampicillin, cephaloridine, cefotaxime, and ceftriaxone. Imipenem and cefoxitin inactivated the P. vulgaris enzyme but were low-Vmax, low-Km substrates for that of M. morganii. Despite these differences, the two I-lactamases caused similar resistance profiles. Ampicillin and cephaloridine were strong inducers for both species, and ,I-lactamaseinducible strains and their stably derepressed mutants were resistant, whereas basal mutants (those with low-level uninducible P-lactamase) were susceptible to these two compounds. Mezlocillin, cefotaxime, ceftriaxone, and (usually) carbenicillin were almost equally active against P-lactamase-inducible organisms and their basal mutants, but were less active against stably derepressed mutants. This behavior reflected the P-lactamase lability of these drugs, coupled with their weak inducer activity below the MIC. Carbenicillin was a labile strong inducer for a single P. vulgaris strain, and inducible enzyme was protective against the drug in this atypical organism. Cefoxitin and imipenem, both strong inducers below the MIC, were almost equally active against P-lactamase-inducible organisms and their basal and stably derepressed mutants.

Efficacy of neutral and negatively charged liposome-loaded gentamicin on planktonic bacteria and biofilm communities

“…11,12 The clinical isolates of Klebsiella oxytoca is an active K1 β-lactamase enzymes which can cause resistance to cephalosporin and aztreonam antibiotics. 13,14 In addition, Proteus vulgaris has the capacity to resist antibiotic treatment due to the inducible expression of chromosomal β-lactamases, 15 while Listeria monocytogenes showed resistance to antibiotic treatment that could be acquired through self-transferable plasmids, mobilizable plasmids, and conjugative transposons. 16 Biofilm formation is an important factor in bacterial virulence.…”

A Common System Controls the Induction of Very Different Genes

“…This results in hyperinducibility or constitutive overproduction of AmpC Plactamase, and thereby confers high P-lactam resistance to the mutant bacteria. In P. vulgaris, the isolation of cefotaxime-resistant, P-lactamase-overproducing mutants has also been reported (Yang and Livermore, 1988), suggesting a defect in an ampD-like gene in this species.…”

“…The P-lactamase-overproducing mutants B317D and 1753D were isolated from colonies of survivors after plating 1-5 X lo8 cells of l? vulgaris B317 and 1753 on Diagnostic Sensitivity Test Agar (Oxoid; Yang and Livermore, 1988) containing cefotaxime in the range 0.05-0.25 pg m1-I. Mutants B317G and B317R with non-inducible P-lactamase were obtained from B317 bacteria by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine (Adelberg et al, 1965).…”

“…Instead, a chromosomal, inducible p-lactamase is present (Matsubara et al, 1981;Maejima et al, 1987;Cullmann and Seibert, 1986;Aspiotis et al, 1986;Yang and Livermore, 1988;Essig, 1984) which, with its molecular mass of 29 kDa, substrate profile and specific inactivation by clavulanic acid, resembles the molecular class-A plasmid-encoded TEM p-lactamase (Hedges et al, 1974;Sutcliffe, 1978;Fisher et al, 1980) and chromosomal P-lactamases present in a minority of Gram-negative bacteria, such as Klebsiella pneumoniae (Arakawa et al, 1986), K. oxytoca (Arakawa et al, 1989), Citrobacter diversus (Perilli et al, 1991) and Pseudomonas stutzeri (Franceschini et al, 1993). The Z?…”

Prevalence and Genotypic Characteristics of ß-lactamase Negative-Ampicillin-Resistant (BLNAR) Haemophilus Influenzae in a Children's Hospital in Turkey

“…β-lactamase specific activities of TEM-1 positive isolates were determined as defined previously. 9 One unit of enzyme efficiency was determined as the efficiency which hydrolysed 1nmol of cephalotin per min per mg of protein. The total protein content was measured with the Bio Rad DC Protein assay kit.…”