Abstract

Background and Objective: Staphylococcus aureus is an important opportunistic pathogen causing a wide range of infections in human .Most clinical isolates of S.aureus are resistant to a number of antibiotics. For appropriate antimicrobial therapy, this study was conducted to determine antibacterial drug resistance patterns of S.aureus isolates obtained from different clinical samples in Rasht.

Material and Methods:  the clinical isolates of S.aureus were collected from different clinical laboratories in Rasht. Thirty coagulase positive S.aureus strains were identified using biochemical tests and amplification of 23SrRNA and coa genes by polymerase chain reaction.  Finally, the resistance pattern of the isolates to 16 selected antimicrobial agents was evaluated by disk diffusion method.

Results:  the S.aureus isolates (75%) were resistant to methicillin and all of them were multidrug resistance. The isolates were high resistance to ampicillin (73%), amoxicillin (60%), cloxacillin (53%) and low resistance to vancomycin (7%) and gentamicin (10%).

Conclusion: given the high prevalence of methicillin resistant, multi drug resistant and presence of vancomycin resistant S.aureus isolates in Rasht, continuously monitoring of drug resistance pattern of S.aureus isolates is recommended for having appropriate therapeutic regime.

Keywords: Staphylococcus Aureus, Coagulase, Drug Resistance, PCR

ABSTRACT
         Background and Objectives: Klebsiella pneumoniae is one of the most important nosocomial pathogens. Its capsular polysaccharide is considered as the first and most important virulence factor of this bacterium. This study aimed to investigate the presence of capsular serotypes K1 and K2 in K. pneumoniae isolates to examine the virulence potency of the isolates.
         Methods: Overall, 65 capsulated K. pneumoniae isolates were collected from patients with urinary tract infections in Rasht, Iran. The isolates were examined using biochemical tests and CPS gene amplification using PCR. Mucoid phenotype of the isolates was determined by the string test. The presence of K1 and K2 genes was evaluated by PCR using specific primers for the genes.
         Results: Of 65 K. pneumoniae isolates, seven (10.77%) were positive for the presence of the K1 gene and four (6.15%) were positive for the presence of the K2 gene. In addition, six serotype K1 isolates (27.27%), four serotype K2 isolates (18.18%), and 12 non-K1/K2 serotype isolates (54.54%) had hypermucoviscosity phenotypes.
          Conclusion: Our results confirm the presence of the capsular serotypes in K. pneumoniae isolates, with a relatively high prevalence for the capsular serotype K1. This study clarifies the importance of rapid diagnosis and suitable treatment of infections caused by K. pneumoniae in prevention of complicated infections.
         Keywords: Klebsiella pneumoniae, Virulence factors, Capsular polysaccharide.

ABSTRACT
        Background and Objective: Campylobacters are infectious zoonotic agents, and among the main bacterial causes of gastroenteritis in humans. Studies have shown that Campylobacter jejuni is of the main causes of infection among humans. Detection of these infectious agents in water resources is of great importance for maintaining the health of humans. Therefore, the aim of this study was molecular detection of C. jejuni strains in surface water samples collected from Rasht, Iran.
       Methods: This cross-sectional descriptive study was performed on 45 surface water samples collected from the city of Rasht. After culture and isolation of bacteria, the molecular detection of C. jejuni was carried out using hipO-specific primers. Presence of cytolethal distending toxin (cdt) gene in positive samples was evaluated by polymerase chain reaction using cdtC-specific primers.
        Results: Of 45 samples, seven (15.5%) were positive for C. jejuni contamination, five of which (71.4%) had the cdtC gene.
Conclusion: The prevalence of toxin-producing C. jejuni in surface waters of Rasht is notable. Therefore, it is recommended to take necessary measures for controlling the spread of this microorganism.
       Keywords: Campylobacter jejuni, Surface water, cdt gene, PCR.

ABSTRACT
       Background and Objectives: Mastitis caused by Staphylococcus aureus is a widely distributed disease in cattle, goats and sheep. The infection is often subclinical in cattle, leading to reduced milk production and quality, but acute catarrhal or even gangrenous inflammation may also occur. The aim of this study was to investigate resistance of S. aureus isolates from bovine subclinical mastitis to a number of antibiotics.
          Methods: Milk samples were collected from 120 cows in different regions of Tabriz, Iran. Milk samples were cultured and bacteriological identification was performed. Antimicrobial susceptibility of the isolates was assessed by determining minimum inhibitory concentration. Plasmid DNA was extracted by an alkaline lysis method. 
         Results: The highest frequency of resistance was observed against gentamicin (100%) and β- lactam antibiotics including amoxicillin (96%), ampicillin (40%) and penicillin (96%). The isolates mostly contained large plasmids, which might harbor acquired antibiotic resistance.
         Conclusion: The results confirm the high frequency of antibiotic resistance among staphylococci isolated from bovine subclinical mastitis.
           Keywords: Anti-infective Agents, Cattle, Staphylococcus Aureus, Mastitis, Plasmids.