Pauline Cordenonsi Bonez

Chlorhexidine activity against bacterial biofilms

BACKGROUND A biofilm is a complex microbiological ecosystem deposited on surfaces. Microorganisms in form of biofilms are of particular clinical concern because of the poor response to antimicrobial treatments. This study aimed to determine whether bacterial and fungal biofilms are able to resist the antimicrobial activity of chlorhexidine, a powerful antiseptic widely used in the hospital environment. METHODS Disk diffusion and susceptibility tests were conducted in accordance with Clinical and Laboratory Standards Institute standards for the determination of biofilm inhibitory concentration. Chlorhexidine was tested first at a minimum inhibitory concentration and then at higher concentrations when it was not able to destroy the biofilm. The plates were developed with a solution of 0.1% crystal violet, and readings were made at an optical density of 570 nm. RESULTS Chlorhexidine demonstrated excellent antimicrobial activity for most microorganisms tested in their free form, but was less effective against biofilms of Acinetobacter baumannii, Escherichia coli, methicillin-resistant Staphylococcus aureus, and Pseudomonas aeruginosa. CONCLUSION This study confirms that microorganisms in biofilms have greater resistance to chlorhexidine, likely owing to the mechanisms of resistance conferred to the structure of biofilms.

Evaluation of antimycobacterial activity of a sulphonamide derivative

Mycobacterial infections including Mycobacterium tuberculosis have been increasing globally. The additional prevalence of multidrug-resistant (MDR-TB) strains and extensively drug-resistant tuberculosis (XDR-TB) stimulate an urgent need for the development of new drugs for the treatment of mycobacterial infections. It is very important to test the antimicrobial activity of novel compounds because they can be used in new with antimycobacterial drug formulation. Studies have shown that Mycobacterium smegmatis can be used in Minimum Inhibitory Concentration (MIC) assays with the advantage of rapidly and safely screen anti-tubercular compounds. This paper presents an evaluation of potential mycobacteriological compounds derived from inorganic synthesis and their microbiological performance along and in conjunction with Trimethoprim. Antimicrobial activity experiments were carried out by using the microdilution technique in broth to evaluate the sensibility against M. smegmatis. MIC values were between 0.153 and 4.88 μg/ml for the compounds tested. Tests of interaction between drugs were made by the method of Fractional Inhibitory Concentration Index (FICI). The compound [Au (sulfatiazolato)(PPh3)] showed synergism FICI = 0.037 and was evaluated by isobols.

Identification of antimicrobial activity among new sulfonamide metal complexes for combating rapidly growing mycobacteria

Mycobacteriosis is a type of infection caused by rapidly growing mycobacteria (RGM), which can vary from localized illness, such as skin disease, to disseminated disease. Amikacin, cefoxitin, ciprofloxacin, clarithromycin, doxycycline, imipenem and sulfamethoxazole are antimicrobial drugs chosen to treat such illnesses; however, not all patients obtain the cure. The reason why the treatment does not work for those patients is related to the fact that some clinical strains present resistance to the existing antimicrobial drugs; thereby, the research of new therapeutic approaches is extremely relevant. The coordination of antimicrobial drugs to metals is a promising alternative in the development of effective compounds against resistant microorganisms. Sulfonamides complexed with Au, Cd, Ag, Cu, and Hg have shown excellent activity against a variety of microorganisms. Considering the importance of fighting against infections associated with RGM, the objective of this study is to evaluate the antimycobacterial activity of metal complexes of sulfonamides against RGM. Complexed sulfonamides activity were individually tested and in association with trimethoprim. The minimum inhibitory concentration (MIC) and time-kill curve of compounds against the standard strains of RGM [Mycobacterium abscessus (ATCC 19977), Mycobacterium fortuitum (ATCC 6841) and Mycobacterium massiliense (ATCC 48898)] was determined. The interaction of sulfonamides with trimethoprim was defined by inhibitory concentration index fractional for each association. The results showed that sulfonamides complexed whit metals have outstanding antimicrobial activity when compared to free sulfamethoxazole, bactericidal activity and synergistic effect when combined with trimethoprim.

Identification of mycobacteria isolated at University Hospital of Santa Maria, Rio Grande do Sul, Brazil

This study evaluated the prevalence of nontuberculous mycobacterium (NTM) in relation to the total number of cases of mycobacterial infections detected in patients admitted at the University Hospital of Santa Maria from 2008 to 2010. From the positive samples for the genus Mycobacterium, 67% belonged to the Mycobacterium tuberculosis complex (MTBC) and 33% of them were classified as NTM. This investigation aims to contribute to the epidemiology of mycobacterioses, inasmuch as patients infected by NTM require distinctive treatment and monitoring in comparison with those infected by MTBC.

Antibiofilm activity of nanoemulsions of Cymbopogon flexuosus against rapidly growing mycobacteria

Rapidly growing mycobacteria (RGM) are opportunistic microorganisms that can cause both local and disseminated infections. When in biofilm, these pathogens become highly resistant to antimicrobials used in clinical practice. Composed abundantly of polymeric substances, biofilms delay the diffusion of antimicrobials, preventing the drug from penetrating the deeper layers and having an effective action. Therefore, the search for new and alternative therapeutic options has become of fundamental importance. Natural products fall into these options, especially essential oils. However, these oils present problems, such as low miscibility in water (which decreases its bioavailability) and degradation by light and temperature. Thus, the objective of this work was to explore the action of free essential oil and nanoemulsions of Cymbopogon flexuosus on strains of RGM, in planktonic and sessile forms. In this work, standard strains of Mycobacterium fortuitum (ATCC 6841), Mycobacterium massiliense (ATCC 48898) and Mycobacterium abscessus (ATCC 19977) were used. The susceptibility of the microorganisms in planktonic form was obtained by conventional microdilution techniques and by cell viability curve. The analysis of the antibiofilm activity was performed by a semi-quantitative macrotechnique. The nanoemulsion exhibited significant antimicrobial activity, with minimum inhibitory concentration values lower than those presented by the free essential oil, against strains in the planktonic state. However, both were efficient in destroying the already formed biofilm, whereas only the free oil inhibited the formation of mycobacterial biofilm. This study demonstrated the therapeutic potential of C. flexuosus essential oil, especially in its nanostructured form, which can be demonstrated against infections caused by rapidly growing mycobacteria.

Molecular characterization of Enterobacteriaceae resistant to carbapenem antimicrobials

The present study aimed to genotypically and phenotypically characterize clinical isolates of carbapenem-resistant Enterobacteriaceae collected from inpatients at the University Hospital of Santa Maria, during seven months. Among the clinical isolates subjected to the modified Hodge test (MHT), 62.5% were positive, indicating possible production of carbapenemase. Polymerase chain reaction (PCR) demonstrated that blaKPC was the most frequently found gene (31%), followed by blaIMP (12.5%). Combined use of the methods is needed to identify carbapenem resistance in enterobacteria to prevent their spread and control the infections caused by these organisms.

Detection of Staphylococcus aureus with an intermediate profile to vancomycin (VISA) isolate from Santa Maria, RS

Twenty-three isolates of Staphylococcus aureus resistant to methicillin have been analyzed, being found a clinical isolate of VISA through microdilution technique. The others techniques were unable to detect such isolates. This is the first study that shows the presence of VISA in clinical isolates in the city of Santa Maria-RS.

The antibacterial and anti-biofilm activity of gold-complexed sulfonamides against methicillin-resistant Staphylococcus aureus

The drug-resistant strains of Staphylococcus aureus have been considered as one of the serious health threats, which are related to high patient hospitalization rates. Besides, Staphylococcus aureus biofilm formation exhibits a drug-tolerant nature and shows nonspecific resistance against a broad-spectrum of antibiotics. The emergence of drug-resistant bacteria stimulated the development of novel medicines as a strategy to control infections. In this study, we evaluated the antibacterial and anti-biofilm activity of gold-complexed sulfonamides against Staphylococcus aureus strains such as methicillin-resistant S. aureus and clinical isolates. Our data showed that the exposure of gold-complexed sulfonamides promoted a remarkable reduction in the bacterial adhesion. Also, confocal microscopy displayed the effects of the compounds on in the bacterial cell biofilm, revealed that the compounds decreased the biofilm formation. Our results also demonstrated that gold-complexed sulfonamides exhibited potent antibacterial activity against Staphylococcus aureus strains. Besides, all compounds presented a synergic antibacterial activity when were associated with classical antibiotics. Gold-complexed sulfonamide compounds did not promote toxic effects on Caenorhabditis elegans. Thus, our results showed that the coordination of sulfonamide with gold is a promising alternative in the development of safe and active compounds against methicillin-resistant and clinical isolates S. aureus.