Effect of linezolid alone and in Combination with other antibiotics, on methicillin-resistant staphylococcus aureus

The prevalence of methicillin-resistant Staphyloccoccus aureus [MRSA] strains has presented a new challenge in antimicrobial medication. Linezolid is a new drug with potent activity on Grampositive pathogens such as MRSA. The aim of the study was to investigate the in vitro activity of linezolid alone and in combination with imipenem, vancomycin or rifampicin to determine the most active therapy against MRSA strains. Twenty clinical MRSA strains were isolated from patients admitted to inpatient departments and outpatient clinics of Theodor Bilharz Research Institute. Standard strain MRSA ATCC 43300 was included as a control. The MICs of MRSA strains to linezolid, vancomycin, imipenem and rifampicin were evaluated using E test. Time-kill curve were used to assess the in vitro activity of linezolid [at 8x MIC] alone and in combination with imipenem [at 32x MIC], vancomycin or rifampicin [at 8x MIC]. Scanning and transmission electron microscopy were performed to compare bacterial morphological alterations owing to the different combinations. Time-kill studies showed synergistic effect when linezolid combined with imipenem was tested against all the MRSA strains. Linezolid plus vancomycin or rifampicin combinations did not display any synergism or antagonism. Scanning and transmission electron microscopy observations confirmed the interactions observed in time kill experiments. Linezolid in combination with subinhibitory concentrations of imipenem can be bactericidal against MRSA strains and appears to be a promising combination for the treatment of MRSA infections. No synergistic activity was seen when the linezolid and vancomycin or rifampicin were combined. Linezolid could prevent the emergence of mutants resistant to rifampicin

Microbiological study of eikenella corrodens isolated from patients and healthy individuals

A total of 99 strains of E. corrodens were isolated in this research. Seventy strains were isolated as flora from 392 normal individuals [17.85%] and 29 strains from 539 in pure form in 2 of the 29 clinical specimens [6.8%], otherwise It was mixed with other bacteria. Most of the isolations were from the mouth [74] but the organism was also recovered from 11 wounds, 7 abscesses and 7 samples of sputum, fluid and transtracheal aspirate. The most common form of E. corrodens infection was the clenched first injuries [33.3%] followed by human bite wounds [20%] and periodontitis [20%]. It is found that colonies of only 71.7% of our isolates were pitting the surface. A comparative growth was studied on 10 media incubated in 3 atmospheres. Chocolate and blood agar found to be the best media using 5% CO[2], Fifty strains tested for 9 biochemical reactions, gave typical results as found by other authors. MIC has been done for 20 strains by the agar dilation and microtiter broth dilution methos E. corrodens found highly susceptible to penicillin and cefoxitin but fairly resistant to clindamycin

Morphotyping: a simple method for differentiation of candida albicans

Fifty strains of C. Albicans were isolated from specimens obtained from 3 various anatomical sites; vagina [20 strains], fingernails [10 strains] and oral cavity [20 strains]. All of them caused clinical illness except for 10 vaginal strains, which were isolated from clinically free females. The identification of C. albicans was done by the germ tube test. Each strain was cultured on malt extract agar plates in the form of streaks for strain differentiation by morphotyping using the modified simplified scheme of Hunter et al. This coding system depends mainly on the fringe characters which are more conspicuous, more consistent and more readily coded than those associated with the streak surface. Fifteen different morphotypes were described. The morphotypes most frequently isolated were those showing discontinuous narrow fine fringes [26%], those lacking any fringes [24%] and those giving discontinuous narrow coarse fringes [18%]. There was a significant difference in the distribution of fringe characters between the 3 categories of superficial infections. The main differences were the predominance of discontinuous fringes among oral isolates and narrow coarse fringes among vaginal cases. The combination of simplicity and reproducibility of morphotyping make it an ideal typing method for first line use