[Molecular evaluation of the 2'-aminoglycoside nucleotidyltransferase gene in Escherichia coli isolates that produce hemolysin and are sensitive to mannose type I pili and P]

Aminoglycosides are highly potent, broad-spectrum antibiotics with many desirable properties for the treatment of life-threatening infections. Escherichia coli [E. coli] is the most common cause of urinary tract infection [UTI]. Antibiotic resistance has recently become prevalent. Enzymatic inactivation of aminoglycosides by aminoglycoside-modifying enzymes is the main mechanism of resistance to these antibiotics in E. coli. The main purpose of this research is to evaluate the presence of the 2'-aminoglycoside nucleotidyltransferase [ant[2"]-Ia] gene in E. coli isolates sensitive to mannose and hemolysin production. After collecting 276 E. coli isolates from patients that referred to Tehran Heart Center, we used the disk diffusion method to determine the resistance patterns of isolates toward Gentamicin, Tobramycin, Kanamycin, Amikacin and Netilmicin antibiotics according to the CLSI principles. We evaluated hemolysin production by assessing the ability of the isolates to grow on sheep and human blood agar media. Chromosomal DNA of the isolates was extracted using DNA extraction kits and PCR method used for the detection of the ant[2"]-Ia gene. In order to study mannose sensitivity we used human RBCs. Results obtained from antibiotic resistance determination tests showed that the highest rate of resistance was observed against tobramycin [24/63%]. Of those resistant, 6% could produce hemolysin in both sheep and human blood agar media. Mannose sensitivity was observed in 14% of isolates during agglutination. There were 24.63% of E. coli isolates resistant to Tobramycin, 23.18% resistant to kanamycin, 21.01% resistant to gentamicin, 6.15% resistant to netilmicin and 3.62% resistant to amikacin. ant[2"]-Ia gene was detected in 47.88% of E. coli isolated from urine. Due to the high prevalence of urinary tract infections caused by uropathogenic E. coli [UPEC] strains and the increasing rate of antibiotic resistance, periodic evaluations should be conducted for outbreaks of resistance in order to select the most suitable treatment to prevent routinely increasing antibiotic resistance

[Prevalence of ant[4]-Ia gene among clinical isolates of methicillin-resistant Staphylococcus aureus using Multiplex-PCR method]

Methicillin-resistant Staphylococcus aureus is a major cause of nosocomial and community-acquired infections. Aminoglycosides are potent bactericidal agents that are often used in combination with either a beta -lactam or a glycopeptide, especially in the treatment of staphylococcal endocarditis. The main mechanism of aminoglycoside resistance in staphylococci is drug inactivation by cellular aminoglycoside-modifying enzymes. The main aim of the present study is determining the prevalence of ant[4]-Ia gene encoding one of the most important aminoglycoside-modifying enzymes and simultaneous detection of mecA gene responsible for methicillin resistance in clinical isolates of Staphylococcus aureus by Multiplex-PCR method. A total of 100 clinical S. aureus isolates were collected from Shariati and Baqiatollah hospitals in Tehran, then antibiotic susceptibility pattern of strains were determined by disk diffusion method using penicillin, oxacillin, vancomycin, tetracycline, erythromycin, gentamicin, tobramycin, amikacin, netilmicin and kanamycin disks, considering CLSI principles. Using agar dilution method the MIC for oxacillin, gentamicin, tobramycin and amikacin were also determined. In order to detect resistance genes, ant[4]-Ia and mecA, two pairs of specific primers were used and their prevalence was determined by using a Multiplex-PCR method. All strains were resistant to penicillin [100%] and after that the highest rate of resistance was observed against kanamycin [68%], tetracycline [61%], erythromycin [56%], tobramycin [53%], gentamicin [52%], amikacin and oxacillin [48%] and netilmicin [22%], respectively. All of the strains were also susceptible to vancomycin. In agar dilution method 50% of strains were oxacillin resistant and 49%, 45% and 51% of the strains showed resistance toward gentamicin, amikacin and tobramycin, respectively. Thirty-seven percent of the strains also showed high-level gentamicin resistance with MIC of >/= 128 micro g/ml. In Multiplex-PCR method 53% of the strains possessed mecA gene and 58% of the strains were ant[4?]-Ia positive. Results obtained by phenotypic and genotypic antibiotic susceptibility determination tests show that there is a statistically meaningful relationship between methicillin resistance and aminoglycoside resistance in MRSA strains [P<0.05]