|1813-1||Influence of B-lactamases on permeability loss in enterobacteria.|
|Autores:||Mónica Pavez (USP - Universidade de São Paulo) ; Camila Vieira (USP - Universidade de São Paulo) ; Lara Mendes de Almeida (USP - Universidade de São Paulo) ; Alvaro Cerda (USP - Universidade de São Paulo) ; Maria Rita de Araujo (HBP - Hospital Beneficiência Portuguesa) ; Nilton Lincopan (USP - Universidade de São Paulo) ; Elsa Mamizuka (USP - Universidade de São Paulo) |
Background: The Outer membrane (OM) permeability contributes to generate a variety of intrinsic resistance. The lack of outer membrane porins (OMPs) in enterobacterias had been related with imipenem resistance, and how the exposition to this antibiotic leading to modify the permeability barrier, but this is not enough to determinate the lack and resistance. We analyzed the lack of OMPs in imipenem resistance and evaluated statistically the influences of B-lactamases presence in the lost of OM permeability.
Methods: Thirty six isolates (18 susceptible and 18 resistant to imipenem without carabapenemases) were selected. MICs for β-lactamics and phenotypic studies and PCR amplification for β-lactamase genes were performed to determinate ESBL and AmpC presence. OMP profile was analyzed using SDS-PAGE and isolates were assigned to the normal permeability (NP, two major porins, n=18) or diminished permeability (DP, loss of one porin, n=18) groups. Frequency distribution of resistance genes between groups by chi-square test and logistic regression analysis were performed using the SSSPS software. Odds ratio (OR) 95% confidence interval (95%CI) were calculated to access the risk for permeability loss.
Results: 67% of imipenem resistant and 38% of imipenem susceptible isolates lack one OMP (χ2=1.829, p=0.176). The frequencies of ESBL enzymes was similar between groups (NP:50%, DP:55%; OR=1.25, 95%CI=0.3369-4.638, p=0.739). Frequency of AmpC was higher in the DP group and bacteria carrying this enzyme have 7 times more chance to present loss of permeability (NP: 22%, DP:67%; OR=7.00, 95%CI=1.590 to 30.81, p=0.007). Further regression analysis demonstrated that bacteria carrying two resistance genes (both AmpC and ESBL) have 30 times increased risk for permeability loss (OR=30.00, 95%CI=1.47-677.83) when compared to those that do not have any enzyme of resistance.
Conclusions: Lack of OMP was not statically associated to imipenem susceptibility. Presence of AmpC is a key factor to increase impermeability barrier in enterobacteria. Although ESBL is not statistically associated to permeability loss, the presence of this enzyme potentiates the influence of AmpC, increasing the risk for impermeability related to AmpC presence
Palavras-chave: B-lactamases, impermeability, Outer membrane protein, carabapenem resistant, enterobacteria