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

Virulence factors and susceptibility patterns of candida species isolated from patients with obstructive uropathy and bladder cancer

Candiduria is a common and high risk event in patients with uropathies and cancer. In this study we investigated the distribution of 3 virulence factors namely: biofilm formation [BF], secreted aspartyl proteinase [SAP] and phospholipase activity [PLA] among different Candida species isolated from inpatients with candiduria. The susceptibility patterns of Candida isolates to antifungal agents, including the new voriconazole, were evaluated in vitro and the association of these virulence factors with resistance was studied. Urine specimens from 250 patients divided into 3 groups were examined: Group1 [n=50] cancer bladder; Group2 [n=100] obstructive uropathy and Group 3 [n=100] simple recurrent urinary tract infection [UTI]. Candida isolates were identified by CHROM-agar, and by Candifast Es Twin test. Susceptibility testing to antifungal agents was evaluated by disc diffusion test using fluconazole [FCZ] 30microg discs and E test strips for Minimum inhibitory concentration [MIC] determination of FCZ, voriconazole [VCZ] and Amphotericin B [AMB]. Assessment of BF was performed by tube and spectrophotometric plate adherence methods and quantitated by crystal violet staining and XTT reduction assays. PLA was screened using Sabouraud egg yolk agar and SAP was detected using bovine serum albumin agar [BSA]. The overall prevalence of candiduria was 24% with highest incidence among obstructive uropathy patients [67.2%]. Isolation rate of Candida [C]. nonalbicans species [C. tropicalis ,C. krusei and C. glabrata] was significantly higher than C. albicans [73.1% versus 26.8%; p256microg/ml]. Voriconazole, the new triazole antifungal agent, was active against all isolated Candida species with a sensitivity rate of 82%-100% and low MIC values [0.064-1microg/ml] except in C. glabrata species [22%]. All isolated Candida species were more sensitive to VCZ compared to FCZ; particularly C. krusei isolates [90% versus 9%]. AMB remained to be an effective drug with absolute sensitivity and low MIC

Hepatitis B virus [HBV] genotypes in Egyptian pediatric cancer patients with acute and chronic active HBV infection

Background: There are eight genotypes of hepatitis B virus [A-H] and subgenotypes are recognized. Genotyping can be accomplished based on a partial sequence of HBV genome such as the pre-S or S gene. Several methods have been developed and used for HBV genotyping. This study was undertaken to determine the HBV genotypes in Egyptian pediatric cancer patients with acute and chronic liver disease

Methods: HBV genotypes were determined in 22 patients who had acute forms of liver disease [AH] and in 48 patients with chronic active hepatitis [CAH]. A type-specific primer based on the nested-PCR method was employed in the HBV genotyping

Results: This study showed that HBV infections in pediatric cancer patients are attributed predominantly to viral genotypes D and B that constituted 37.1% and 25.7%, respectively of the total infections. In addition, there was a relatively high prevalence of mixed infections of 15.7% among the studied group especially mixed A/D genotype infections. Genotype D was found significantly more often in patients with CAH than in patients with AH [P<0.05]

Conclusion: These findings show the distribution of HBV A-D genotypes in pediatric cancer Egyptian patients. Furthermore, our results indicate a markedly high prevalence of mixed A/D genotype infections in subjects with CAH and a possible association of mixed infections with the severity of liver diseases