A kinetic analysis of the inhibition of FOX-4 β-lactamase, a plasmid-mediated AmpC cephalosporinase, by monocyclic β-lactams and carbapenems.

Objectives: Class C β-lactamases are prevalent among Enterobacteriaceae; however, these enzymes are resistant to inactivation by commercially available β-lactamase inhibitors. In order to find novel scaffolds to inhibit class C β-lactamases, the comparative efficacy of monocyclic β-lactam antibiotics (aztreonam and the siderophore monosulfactam BAL30072), the bridged monobactam β-lactamase inhibitor BAL29880, and carbapenems (imipenem, meropenem, doripenem and ertapenem) were tested in kinetic assays against FOX-4, a plasmid-mediated class C β-lactamase (pmAmpC).

Methods: The FOX-4 β-lactamase was purified.

Expression of OXA-type and SFO-1 β-lactamases induces changes in peptidoglycan composition and affects bacterial fitness.

β-Lactamases and penicillin-binding proteins (PBPs) have evolved from a common ancestor. β-Lactamases are enzymes that degrade β-lactam antibiotics, whereas PBPs are involved in the synthesis and processing of peptidoglycan, which forms an elastic network in the bacterial cell wall. This study analyzed the interaction between β-lactamases and peptidoglycan and the impact on fitness and biofilm production.

Involvement of the AcrAB-TolC efflux pump in the resistance, fitness, and virulence of Enterobacter cloacae.

Multidrug efflux pumps have emerged as important mechanisms of antimicrobial resistance in bacterial pathogens. In order to cause infection, pathogenic bacteria require mechanisms to avoid the effects of host-produced compounds, and express efflux pumps may accomplish this task. In this study, we evaluated the effect of the inactivation of AcrAB-TolC on antimicrobial resistance, fitness, and virulence in Enterobacter cloacae, an opportunistic pathogen usually involved in nosocomial infections.

Distant and new mutations in CTX-M-1 beta-lactamase affect cefotaxime hydrolysis.

The CTX-M β-lactamases are an increasingly prevalent group of extended-spectrum β-lactamases (ESBL). Point mutations in CTX-M β-lactamases are considered critical for enhanced hydrolysis of cefotaxime. In order to clarify the structural determinants of the activity against cefotaxime in CTX-M β-lactamases, screening for random mutations was carried out to search for decreased activity against cefotaxime, with the CTX-M-1 gene as a model.

Role of changes in the L3 loop of the active site in the evolution of enzymatic activity of VIM-type metallo-beta-lactamases.

Objectives: The new metallo-beta-lactamase VIM-13 has been recently characterized. In comparison with the VIM-1 enzyme, VIM-13 showed 19 amino acid differences, 2 of which were located in the active site centre. The main objective of the present study was to assess whether differences between VIM-1 and VIM-13 beta-lactamases in the active site, at His224Leu and Ser228Arg, are necessary and sufficient to explain the microbiological and biochemical differences between the two enzymes.

A tripeptide deletion in the R2 loop of the class C beta-lactamase enzyme FOX-4 impairs cefoxitin hydrolysis and slightly increases susceptibility to beta-lactamase inhibitors.

Objectives: A natural variant of the AmpC enzyme from Escherichia coli HKY28 with a tripeptide deletion (Gly-286/Ser-287/Asp-288) was recently described. The isolate produced an inhibitor-sensitive AmpC beta-lactamase variant that also conferred higher than usual levels of resistance to ceftazidime in the E. coli host.

Associating growth-phase-related changes in the proteome of Acinetobacter baumannii with increased resistance to oxidative stress.

Acinetobacter baumannii is an opportunistic pathogen that has been associated with severe infections and outbreaks in hospitals. At present, very little is known about the biology of this bacterium, particularly as regards mechanisms of adaptation, persistence and virulence. To investigate the growth phase-dependent regulation of proteins in this microorganism, we analyzed the proteomic pattern of A.

Structure-function studies of arginine at position 276 in CTX-M beta-lactamases.

Objectives: In order to assess whether or not the Arg-276 of CTX-M-type enzymes is equivalent to the Arg-244 of IRT-TEM-derivative enzymes, we replaced the former with six different amino acids, some of them previously described as involved in resistance to beta-lactamase inhibitors in TEM-IRT derivatives. We also investigated the role of Arg276 in cefotaxime hydrolysis.

Methods: By site-directed mutagenesis and by use of the bla(CTX-M-1) gene as template, Arg-276 was replaced with six different amino acids (Trp, His, Cys, Asn, Gly and Ser).

Cloning, nucleotide sequencing, and analysis of the AcrAB-TolC efflux pump of Enterobacter cloacae and determination of its involvement in antibiotic resistance in a clinical isolate.

Enterobacter cloacae is an emerging clinical pathogen that may be responsible for nosocomial infections. Management of these infections is often difficult, owing to the high frequency of strains that are resistant to disinfectants and antimicrobial agents in the clinical setting. Multidrug efflux pumps, especially those belonging to the resistance-nodulation-division family, play a major role as a mechanism of antimicrobial resistance in gram-negative pathogens.

Molecular characterization of the gene encoding a new AmpC beta-lactamase in Acinetobacter baylyi.

Objectives: The main objective of the present study was to demonstrate the presence of a beta-lactamase ampC gene in the chromosome of the non-pathogenic bacterium Acinetobacter baylyi ADP1.

Methods: beta-Lactam MICs were determined by Etest. The ampC gene was amplified by PCR, with specific oligonucleotides, then cloned into pBGS18 and pAT-RA plasmids and transformed into Escherichia coli TG1 and parental A.

Interspecies spread of CTX-M-32 extended-spectrum beta-lactamase and the role of the insertion sequence IS1 in down-regulating bla CTX-M gene expression.

Objectives: To characterize the extended-spectrum beta-lactamases (ESBLs) as well as their genetic environment in different isolates of Enterobacteriaceae from a patient with repeated urinary tract infections.

Methods: Two isolates of Escherichia coli and one Proteus mirabilis, all with ESBL phenotypes, were studied. Conjugation experiments and restriction fragment length polymorphisms (RFLPs) were performed.

Langerhans cell histiocytosis of vulva.

Cutaneous involvement of the vulva by Langerhans cell histiocytosis in women older than 70 is a rare phenomenon. A tendency of the disease to involve genital areas, has been described. We present a case of a 72-year-old woman, who had cutaneous vulvar involvement by Langerhans-cell histiocytosis, diagnosed by biopsy.

[Autosomal dominant punctate palmoplantar keratoderma].

Hereditary punctate palmoplantar keratoderma or Buschke-Fisher-Brauer disease is a rare form of keratoderma that follows a pattern of autosomal dominant inheritance with variable penetrance. The age of onset is usually between 12 and 30 years of age. Clinically, it is characterized by the gradual appearance of multiple punctate hyperkeratotic papules, irregularly distributed on the palms and soles, as well as by its possible association with several diseases, primarily with malignant processes.

[Kindler syndrome: presentation of a case].

Kindler syndrome is a very rare disease caused by mutations resulting in defects in the extracellular matrix-actin link. It usually presents with acral blistering from birth in trauma-prone areas, pronounced photosensitivity that improves with age and the development of poikiloderma and cutaneous atrophy. Mucosal involvement and degeneration have been described with relative frequency.