RESUMEN
Acinetobacter baumannii is a ubiquitous pathogen that has emerged as a major cause of healthcare-associated infections. Acinetobacter baumannii usually causes respiratory tract, urinary tract, blood stream and surgical site infections. They are of increasing importance because of its ability to rapidly develop resistance to the major groups of antibiotics. There are few data available on the antimicrobial susceptibility of A. baumannii in Iran. During the period of study from July 2005 to November 2006, a total of 88 strains of A. baumannii were isolated from clinical specimens obtained from patients hospitalized in an Iranian 1000-bed tertiary care hospital. Conventional bacteriological methods were used for identification of A. baumannii. Susceptibility testing was performed by the method recommended by Clinical Laboratory and Standards Institute (CLSI). The majority of isolates were from respiratory tract specimens. The organism showed high rate of resistance to ceftriaxone (90.9%), piperacillin (90.9%), ceftazidime (84.1%), amikacin (85.2%) and ciprofloxacin (90.9%). Imipenem was the most effective antibiotic against A. baumannii and the rate of resistance for imipenem was 4.5%. The second most effective antibiotic was tobramycin, and 44.3% of A. baumannii isolates were resistant to this antibiotic. In conclusion, our study showed that the rate of resistance in A. baumannii to imipenem was low. There was a significant relationship between demographic features of patients such as age, undergoing mechanical ventilation, length of hospital stay and drug resistance.
RESUMEN
Xanthan gum is a microbial polysaccharide of great commercial importance as it has unusual rheological properties in solution and consequent range of applications. In this study, a series of mutants were isolated from Xanthomonas campestris PTCC 1473 by ethyl methanesulfonate mutagenesis. The polysaccharide yield of one mutant, XC1473E2, was 30% better than that of the parent strain. It also showed higher xanthan formation and glucose consumption rates compared to the parent strain. Xanthan produced by the mutant had enhanced viscosity, higher pseudoplasticity and larger molecular weight. Since mutant XC1473E2 appeared white on agar plates, it underwent pigment extraction with methanol. Contrary to the parent strain, the mutant showed no absorption at 443nm, i.e. the wavelength related to yellow pigment. This finding suggested that yellow pigmentation and normal xanthan biosynthesis are not necessarily concurrent. In general, mutant XC1473E2 seems to be a strain with interesting characteristics for use in commercial production of xanthan