Cinnamaldehyde and baicalin reverse colistin resistance in Enterobacterales and Acinetobacter baumannii strains.

Purpose: Colistin is used as a last resort antibiotic against infections caused by multidrug-resistant gram-negative bacteria, especially carbapenem-resistant bacteria. However, colistin-resistance in clinical isolates is becoming more prevalent. Cinnamaldehyde and baicalin, which are the major active constituents of Cinnamomum and Scutellaria, have been reported to exhibit antibacterial properties.

Resistance to 16-Membered Macrolides, Tiamulin and Lincomycin in a Swine Isolate of .

() is an opportunistic pathogen with the ability to disseminate resistance determinants to antibiotics; however, its resistance to macrolides has been less studied. The aim of the present study was to characterize the mechanisms responsible for the resistance to macrolides, tiamulin and lincomycin found in a strain of isolated from a pig with pneumonia. MICs of erythromycin, 15- and 16-membered macrolides, tiamulin and lincomycin were determined by microdilution method with and without reserpine, an inhibitor of ABC efflux pumps and regions of the genome were sequenced.

Biofilm Formation among Isolates Has Clinical Relevance: The ANSELM Prospective Multicenter Study.

The ability to form biofilms is a recognized trait of , but the extent of its clinical relevance is still unclear. The present multicenter prospective study (ANSELM) aims at investigating the association between biofilm formation and clinical outcomes of infections. One hundred and nine isolates were collected from various geographical origins and stratified according to their clinical relevance.

Aspirin, sodium benzoate and sodium salicylate reverse resistance to colistin in Enterobacteriaceae and Pseudomonas aeruginosa.

Background: MDR bacterial infections are currently a serious problem for clinicians worldwide. Klebsiella pneumoniae and Enterobacter spp., among Enterobacteriaceae, and Pseudomonas aeruginosa, are part of the group of ESCAPE pathogens or bacteria that 'escape' from common antibacterial treatments.

Antimicrobial susceptibility profiles of porcine mycoplasmas isolated from samples collected in southern Europe.

Background: Mycoplasma (M.) hyopneumoniae, M. hyorhinis and M.

Interaction of carbapenems and β-lactamase inhibitors towards CTX-M-15 and CTX-M-15 mutant.

Objectives: The aim of this study was to evaluate the role of residue 238 in CTX-M-15 and CTX-M-15 mutant with respect to carbapenems and various β-lactamase inhibitors.

Methods: A CTX-M-15 laboratory mutant was generated by site-directed mutagenesis from CTX-M-15 enzyme by replacing glycine 238 with cysteine. Thiol titration and p-chloromercuribenzoate (PCMB) inactivation assays were used to ascertain the presence of a disulfide bridge in the active site of CTX-M-15.

Mechanisms involved in quinolone resistance in Mycoplasma mycoides subsp. capri.

Mycoplasma mycoides subsp. capri is a causative agent of contagious agalactia in goats. In this study, M.

QnrS1 structure-activity relationships.

Objectives: Loop B is important for low-level quinolone resistance conferred by Qnr proteins. The role of individual amino acids within QnrS1 loop B in quinolone resistance and gyrase protection was assessed.

Methods: qnrS1 and 11 qnrS1 alleles with site-directed Ala mutations in loop B were expressed in Escherichia coli BL21(DE3) and proteins were purified by affinity chromatography.

Resistance to ceftazidime in Escherichia coli associated with AcrR, MarR and PBP3 mutations and overexpression of sdiA.

The mechanisms responsible for the increase in ceftazidime MIC in two Escherichia coli in vitro selected mutants, Caz/20-1 and Caz/20-2, were studied. OmpF loss and overexpression of acrB, acrD and acrF that were associated with acrR and marR mutations and sdiA overexpression, together with mutations A233T and I332V in FtSI (PBP3) resulted in ceftazidime resistance in Caz/20-2, multiplying by 128-fold the ceftazidime MIC in the parental clinical isolate PS/20. Absence of detectable β-lactamase hydrolytic activity in the crude extract of Caz/20-2 was observed, and coincided with Q191K and P209S mutations in AmpC and a nucleotide substitution at -28 in the ampC promoter, whereas β-lactamase hydrolytic activity in crude extracts of PS/20 and Caz/20-1 strains was detected.

Quorum-sensing regulator sdiA and marA overexpression is involved in in vitro-selected multidrug resistance of Escherichia coli.

Objectives: The role of sdiA in the acquisition of low-level multidrug resistance (MDR) was analysed and compared with that of marA and soxS in two Escherichia coli clinical isolates and two in vitro-selected mutants.

Methods: The mutants were developed by growth in lomefloxacin and ceftazidime. The sdiA, marA, soxS, ftsI, tolC and acrB gene transcript levels were determined by RT-PCR.

Review on bacterial stress topics.

A complex network of regulatory systems ensures a coordinated and effective response to different types of stress that can act on a bacterium. Bacterial stress response generates changes that influence efflux system and virulence factor expression. Thus, partial or total loss of pathogenicity islands in uropathogenic Escherichia coli can be induced by SOS-dependent or SOS-independent pathways related to selection of quinolone-resistant mutants.

Ciprofloxacin, salicylate, and 2,4-dinitrophenol decrease production of AmpC-type beta-lactamase in two Citrobacter freundii clinical isolates.

The effect of ciprofloxacin and two mar RAB inducers on the susceptibility to beta-lactam antibiotics in two AmpC beta-lactamase semi-constitutive producer Citrobacter freundii clinical isolates (the DM 1 and DM 2 strains) was studied. Possible changes in outer membrane protein expression, permeability to cephaloridine, active efflux, and hydrolytic activity of beta-lactamase-crude extracts were evaluated under the influence of ciprofloxacin, sodium salicylate, and 2,4-dinitrophenol. Results were compared with those of the effect of the same three chemicals on a normally beta-lactamase-inducible wild-type C.

Overexpression system and biochemical profile of CTX-M-3 extended-spectrum beta-lactamase expressed in Escherichia coli.

An efficient over-expression system was developed for CTX-M-3 extended-spectrum-beta-lactamase. The recombinant enzyme was purified from 1 l of culture to yield 22 mg of pure enzyme. The N-terminal amino acid sequence was determined to be NH2-QTADVQ.

Enhanced active efflux, repression of porin synthesis and development of Mar phenotype by diazepam in two enterobacteria strains.

The aim of this work was to determine whether diazepam could induce the multiple antibiotic resistance (Mar) phenotype in Klebsiella pneumoniae and Escherichia coli strains. The Mar phenotype is characterized by decreased susceptibility to multiple antibiotics due to the loss of porins and/or increased expression of active efflux systems. The effect of subinhibitory concentrations of diazepam on the susceptibility of different antimicrobial agents, outer-membrane protein expression and norfloxacin intracellular accumulation was studied.

Salicylate decreases production of AmpC type beta-lactamases and increases susceptibility to beta-lactams in a Morganella morganii clinical isolate.

The effect of salicylate, a marRAB inducer, on the resistance to beta-lactams was characterized in an AmpC beta-lactamase hyperproducer Morganella morganii clinical isolate (the M1 strain). Results were compared with those of the effect of salicylate in a wild-type M. morganii strain.