Detailed studies on Quercus infectoria Olivier (nutgalls) as an alternative treatment for methicillin-resistant Staphylococcus aureus infections

Aims:  To investigate the antimethicillin-resistant Staphylococcus aureus (MRSA) mechanism of Quercus infectoria (nutgalls) extract and its components.
Methods and Results:  Ethanol extract, an ethyl acetate fraction I, gallic acid and tannic acid could inhibit the growth of clinically isolated MRSA strains with minimum inhibitory concentration values between 63 and 250  μ g ml⁻¹. Clumps of partly divided cocci with thickened cell wall were observed by transmission electron microscopy in the cultures of MRSA incubated in the presence of the ethanol extract, the ethyl acetate fraction I and tannic acid. Because cell wall structure of the organism structures seemed to be a possible site for antibacterial mechanisms, their effect with representative β-lactam antibiotics were determined. Synergistic effects with fractional inhibitory concentration index ranged from 0·24 to 0·37 were observed with 76% and 53% of the tested strains for the combination of the ethanol extract with amoxicillin and penicillin G, respectively.
Conclusions:  The appearance of pseudomulticellular bacteria in the treated cells and the synergistic effect of the plant extract with β-lactamase-susceptible penicillins suggest that the extract may interfere with staphylococcal enzymes including autolysins and β-lactamase.
Significance and Impact of the Study:  Our results provide scientific data on the use of the nutgalls, which contain mainly tannin contents up to 70% for the treatment of staphylococcal infections.     

Methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci: epidemiological and molecular aspects

Infections caused by the genus Staphylococcus are of great importance for human health. Staphylococcus species are divided into coagulase-positive staphylococci, represented by S. aureus, a pathogen that can cause infections of the skin and other organs in immunocompetent patients, and coagulase-negative staphylococci (CNS) which comprise different species normally involved in infectious processes in immunocompromised patients or patients using catheters. Oxacillin has been one of the main drugs used for the treatment of staphylococcal infections; however, a large number of S. aureus and CNS isolates of nosocomial origin are resistant to this drug. Methicillin resistance is encoded by the mecA gene which is inserted in the SCC mec cassette. This cassette is a mobile genetic element consisting of five different types and several subtypes. Oxacillin-resistant strains are detected by phenotypic and genotypic methods. Epidemiologically, methicillin-resistant S. aureus strains can be divided into five large pandemic clones, called Brazilian, Hungarian, Iberian, New York/Japan and Pediatric. The objective of the present review was to discuss aspects of resistance, epidemiology, genetics and detection of oxacillin resistance in Staphylococcus spp., since these microorganisms are increasingly more frequent in Brazil.