Minimal phenotypic test for simple differentiation of Xanthomonas campestris from other yellow-pigmented bacteria isolated from soil

Isolation of Xanthomonas campestris from soil has a wide range of applications from monitoring of phytopathogenic populations in soil to screening of improved xanthan-producing strains. Identification of Xanthomonas campestris and its pathovars requires pathogenicity tests in addition to phenotypic and molecular characterization. Thirty phenotypic tests were carried out on 57 yellow-pigmented bacterial isolates obtained from soil of cabbage farms after screening on Selective Xanthomonas [SX] agar and transferring on Yeast Malt agar. Absorption spectra of pigments and capability of biopolymer production were determined for the isolates. Some characteristics of the biopolymer produced and presence of a X. campestris-specific gene marker were investigated for nine putative X. campestris isolates. The present study introduces a set of simple phenotypic tests including urease, acid production from sucrose, mucoid growth on 5% sucrose, starch hydrolysis, growth in 4% NaCl, motility and utilization of asparagine as sole carbon and nitrogen source for quick and inexpensive tentative identification of Xanthomonas campestris. Validation of these tests was confirmed in 100% of the cases by characterization of bacterial exopolysaccharide as xanthan and production of genus-specific xanthomonadin pigment. Moreover, tracking of hrc gene among putative X. campestris isolates gave positive results in 80% of cases. The Minimal simple phenotypic tests facilitate the screening and differentiation of putative X. campestris isolates from other false bacterial strains isolated from soil on semiselective SX agar

[Effects of quinolones on biofilm formed by Staphylococcus epidermidis isolated from patients with urinary tract infection]

Bacterial cells of Staphylococcus epidermidis are naturally occurring on skin and human mucosal membranes. They also cause nosocomial infections. Capability of biofilm formation plays an important role in the bacterial virulence. Quinolones have been used to treat urinary tract infections caused by S. epidermidis for several years. Thus, resistance to this type of antibiotics has emerged among the strains of this organism. Since the bacterial cells residing within biofilm structures are more resistant than those in planctonic stage, we conduct this study to examine the effect of quinolones was the main goal of ones study of higher resistance of native biofilm producing strains is the goal of this project. In this research ten native isolates of S. epidermidis were obtained from patients with urinary tract infection. Also standard strain of S. epidermidis PTCC 1435 was used as a control. Identification of strains was confirmed using morphological and biochemical tests. Challenge tests against the isolated was performed using three quinolone antibiotics including Ciprofluxacin, Ofluxacin, Nalidixic acid, with two different procedures: kirby bauer disk diffusion test, and broth dilution test. Average of MICs of above mentioned antibiotics against ten isolated was obtained as follow: Ciprofluxacin [7/375 micro g /micro l], Ofluxacin [11/53 micro g /micro l], Nalidixic acid [2597 /2 micro g /micro l]. Experimental biofilm model of these bacteria showed much higher resistance to quinolone antibiotic, from 15 times in case of Nalidixic acid to 18 times greater resistance in case of Ciprofluxacin. Average of MICs among ten isolates against the three antibiotics also showed increased resistance as follow: Ciprofluxacin [128/4 micro g /micro l], Ofluxacin [177/8 micro g /micro l], Nalidixic acid [3942/4 micro g /micro l]. S. epidermidis showed increased resistance to different quinolone antibiotics in biofilm structure, comparing to those of planktonic form. Results obtained from this research is in agreement with those of other similar projects; and emphesize on applying of adequate doses of antibiotics against urinary infection caused by biofilmic Staphylococcus epidermidis