In vitro activities of vancomycin and linezolid against biofilm-producing methicillin-resistant staphylococci species isolated from catheter-related bloodstream infections from an Egyptian tertiary hospital.

PURPOSE: Catheter-related bloodstream infections (CRBSIs) are among the most common hospital-acquired infections. We aimed to survey methicillin resistance, biofilm production and susceptibility to vancomycin, linezolid and other antibiotics for staphylococci isolated from CRBSIs. METHODOLOGY: Fifty-eight isolates [20 S. aureus and 38 coagulase-negative staphylococci (CoNS; 20 Staphylococcusepidermidis, nine Staphylococcushaemolyticus, three Staphylococcusschleiferi, two Staphylococcuswarneri and four Staphylococcuslugdunensis)] were tested for methicillin resistance by cefoxitin disk diffusion and detection of the mecA gene by PCR; biofilm-forming ability using Congo red agar and tissue culture plate methods; susceptibility to ciprofloxacin, clindamycin, cotrimoxazole, erythromycin, gentamicin, linezolid, rifampicin and tetracycline; and MIC determination for vancomycin.Results/Key findings. Cefoxitin resistance was detected among 40 % (8/20) S. aureus isolates, 70 % (14/20) S. epidermidis isolates and 16.7 % (3/18) of other CoNS, although the mecA gene was detected in 45 % (9/20) S. aureus isolates, 35 % (7/20) S. epidermidis isolates and 16.7 % (3/18) of other CoNS. Biofilm-forming ability ranged from 45 to 75 %. Methicillin-resistant S. aureus and other CoNS were considered to be more virulent than methicillin-resistant S. epidermidis due to the higher biofilm forming abilities of the former. All tested isolates exhibited 100 % sensitivity to vancomycin and linezolid, irrespective of their methicillin resistance or biofilm-forming ability. Rifampicin showed overall sensitivity of 75.9 %. Varying degrees of multi-resistance were found for the other antibiotics. CONCLUSION: Vancomycin, linezolid and rifampicin could be used effectively against methicillin-resistant staphylococci isolated from CRBSIs.

Comparison between the standardized clinical and laboratory standards institute M38-A2 method and a 2,3-Bis(2-Methoxy-4-Nitro-5-[(Sulphenylamino)Carbonyl]-2H-tetrazolium hydroxide- based method for testing antifungal susceptibility of dermatophytes.

In this study, we determined the utility of a 2,3-bis(2-methoxy-4-nitro-5-[(sulfenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT)-based assay for determining antifungal susceptibilities of dermatophytes to terbinafine, ciclopirox, and voriconazole in comparison to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 method. Forty-eight dermatophyte isolates, including Trichophyton rubrum (n = 15), Trichophyton mentagrophytes (n = 7), Trichophyton tonsurans (n = 11), and Epidermophyton floccosum (n = 13), and two quality control strains, were tested. In the XTT-based method, MICs were determined spectrophotometrically at 490 nm after addition of XTT and menadione. For the CLSI method, the MICs were determined visually. With T. rubrum, the XTT assay revealed MIC ranges of 0.004 to >64 mug/ml, 0.125 to 0.25 mug/ml, and 0.008 to 0.025 mug/ml for terbinafine, ciclopirox, and voriconazole, respectively. Similar MIC ranges were obtained against T. rubrum by using the CLSI method. Additionally, when tested with T. mentagrophytes, T. tonsurans, and E. floccosum isolates, the XTT and CLSI methods resulted in comparable MIC ranges. Both methods revealed similar lowest drug concentrations that inhibited 90% of the isolates for the majority of tested drug-dermatophyte combinations. The levels of agreement within 1 dilution between both methods were as follows: 100% with terbinafine, 97.8% with ciclopirox, and 89.1% with voriconazole. However, the agreement within 2 dilutions between these two methods was 100% for all tested drugs. Our results revealed that the XTT assay can be a useful tool for antifungal susceptibility testing of dermatophytes.

Single-step PCR using (GACA)4 primer: utility for rapid identification of dermatophyte species and strains.

Dermatophytes are fungi that belong to three genera: Epidermophyton, Microsporum, and Trichophyton. Identification of dermatophyte species is essential for appropriate diagnosis and treatment of dermatophytosis. Routine identification depends on macroscopic and microscopic morphology, which is time-consuming and does not identify dermatophyte strains. In this study, two PCR-based methods were compared for their abilities to identify 21 dermatophyte isolates obtained from Egyptian patients to the species and strain levels. The first method employed a two-step method: PCR amplification, using ITS1 and ITS4 as primers, followed by restriction enzyme digestion using the endonuclease MvaI. The second method employed a one-step approach employing the repetitive oligonucleotide (GACA)(4) as a primer. Dermatophyte strains were also identified using a conventional culture method. Our results showed that the conventional culture method identified four species: Microsporum canis, Trichophyton mentagrophytes, Trichophyton rubrum, and Trichophyton violaceum. Moreover, both PCR methods agreed with the diagnosis made using the conventional approach. Furthermore, ITS1/ITS4-based PCR provided no strain differentiation, while (GACA)(4)-based PCR identified different varieties among the T. mentagrophytes isolates. Taken together, our results suggest that (GACA)(4)-based PCR has utility as a simple and rapid method for identification of dermatophyte species as well as utility for differentiation of T. mentagrophytes variants.