High level of gentamicin resistance (HLGR) among enterococcus strains isolated from clinical specimens.

BACKGROUND: Enterococci are pathogens that can cause nosocomial infections and acquire resistance properties via several molecular mechanisms. The aac (6')Ie-aph(2″)Ia gene plays a significant role in the emergence of high-level gentamicin-resistant (HLGR) strains. The screening of resistant strains and the provision of appropriate antibiotic therapy can decide the outcome of serious nosocomial infections. METHODS: In the present study, 142 enterococci were isolated from patients, and the species were identified using standard methods. An antimicrobial susceptibility test was performed using the disc diffusion method, and the minimum inhibition concentration (MIC) of gentamicin was determined according to the broth micro-dilution method. Additionally, PCR was utilized to detect the aac(6')Ie-aph(2″)Ia gene, the presence of which was confirmed by digestion with Sca1 and sequencing. RESULTS: Of the 142 isolates, 62 (43.7%) were found to exhibit the HLGR phenotype. All except one of the HLGR isolates contained the aac(6')Ie-aph(2″)Ia gene. The prevalence of resistance to other antibiotics and multi-drug resistance (MDR) was higher among the HLGR isolates compared to the non-HLGR isolates. CONCLUSIONS: Our results indicate that high prevalence rates of MDR and HLGR enterococci are an important problem associated with medical treatment. Furthermore, the presence of the aac(6')Ie-aph(2″)Ia gene was shown to correspond to the presence of the HLGR phenotype among enterococci.

Caffeine alters mitochondrial dehydrogenase and alkaline phosphatase activity of human gingival fibroblasts in vitro.

AIM: Caffeine is one of the most widely consumed behaviorally active substances in the world. Although its effects on the central nervous system and bone metabolism have been documented, as yet there is no report on its effect on tissues in the oral cavity. In this study we analyzed the viability of human gingival fibroblasts (HGF) and alkaline phosphatase (ALP) enzyme activity after exposure to different concentrations of caffeine for different exposure time periods. METHODS: The HGF were cultured with different concentrations of caffeine. Viability of cells exposed to caffeine was analyzed by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay to assess mitochondrial dehydrogenase activity. The activity of ALP was analyzed at specific time intervals after caffeine addition. RESULTS: Our results showed that caffeine of concentrations <1 mm did not affect the viability of HGF and the ALP enzyme activity. Nevertheless, caffeine at 5 and 10 mm dramatically decreased the viability and ALP activity of the cells after 4 days such that, by day 9, the viability of cells declined to near zero in the 10 mm group. CONCLUSION: These results provided evidence that caffeine in high concentrations can decrease cellular viability and ALP activity in HGF.

Serotyping of Streptococcus pneumoniae isolated from Tehran by Multiplex PCR: Are serotypes of clinical and carrier isolates identical?

BACKGROUND AND OBJECTIVES: Streptococcus pneumoniae is the most common cause of invasive infections among both young children and elderly people. Common serotypes causing invasive diseases and the emergence of carriers of Streptococcus pneumoniae in Iran is not yet known. Past-vaccine surveillance studies of serotype prevalence patterns in Iran are necessary to monitor the epidemiology of Streptococcus pneumoniae. Because of variation of pneumococcal serotypes in different geographical regions, in this study we evaluated common serotypes causing pneumococcal infections and healthy carrier children in Tehran by Multiplex PCR. MATERIALS AND METHODS: A total of 150 nasopharyngeal swabs were collected from healthy children in Tehran between December 2011 and August a2012, and 100 clinical samples were collected. Identification was performed by biochemical and molecular tests. Serotyping was done by multiplex PCR. We designed primers based on the sequences available for the routine capsular types and combined them into six multiplex PCR. RESULTS: From 150 nasopharyngeal swabs, 40 isolates of Streptococcus pneumoniae were identified after identification tests. Thirty six clinical isolates were also detected among clinical samples. Four serotypes (19A, 6, 3, 23F) of S. pneumoniae accounted for 55.7% of both sets of strains isolated from nasal carriage and clinical samples. Serotype 19A was the most common serotype among both groups. CONCLUSION: The multiplex PCR approach was successfully adapted to identify serotypes from more than 91% of the isolates tested. Among S. pneumoniae isolates in Tehran, the most prevalent serotypes were similar among carriage and invasive isolates. Continued monitoring of common serotypes of Streptococcus pneumoniae is essential for future vaccine formulation in Iran.

Identification and Characterization of a High Vancomycin-Resistant Staphylococcus aureus Harboring VanA Gene Cluster Isolated from Diabetic Foot Ulcer.

OBJECTIVES: Staphylococcus aureus is a common cause of human infection, and emergence of vancomycin-resistance S. aureus is a great concern for treatment of methicillin-resistant S. aureus,(MRSA) in recent years (MRSA). Here, we report the isolation of high-level VRSA. MATERIALS AND METHODS: S. aureus was isolated from foot ulcer of a diabetic woman in Tehran, Iran. Antibiotic susceptibility was determined according to CLSI guidelines. VanA gene cluster PCR was carried out and PCR amplicon of vanA was sequenced. RESULTS: S. aureus had high-level vancomycin-resistant (MIC 512 ≥ µg/ml). Patient's history revealed that VRSA isolate was acquired through community transmission. Only vanA, vanR and vanS genes were amplified in our isolate. Sequencing revealed that the vanA sequence had high similarity to the vanA sequence of Tn1546. CONCLUSION: Although VRSA infection continues to be rare, isolation of community-acquired VRSA is a significant issue and it needs the efforts of public health authorities.

In-vitro Comparison of the Antimicrobial Properties of Glass Ionomer Cements with Zinc Phosphate Cements.

White spot lesions are observed in nearly 50% of patients undergoing orthodontic treatment. Long-lasting antibacterial properties of orthodontic cements can reduce this phenomenon. The aim of this research was to compare antimicrobial activity of three commercial glass ionomer cements with three commercial zinc phosphate cements, over time, against streptococcus mutans and candida albicans. Direct contact test (DCT) was used to evaluate the antibacterial and antifungal activity of products after 48 h and 7 days of incubation. The results demonstrated that all the cements presented antibacterial activity but the antibacterial activity of glass ionomer cements was more than that of zinc phosphate cements. Counts of C. albicans after 48 h were lower and statistically different in the GIC group in relation to the control groups. But no differences were observed between GIC and control groups at 7 days. Based on the results of this study, the antimicrobial and mainly antifungal effects of all the cements were so short.

Mechanistic analysis of drug release from theophylline pellets coated by films containing pectin, chitosan and Eudragit RS.

The objective of this study was to obtain detailed information on the mechanism of drug release from mixed-film of pectin-chitosan/Eudragit RS. Pellets (710-840 microm in diameter) containing 60% theophylline and 40% microcrystalline cellulose were prepared by extrusion-spheronization method. Eudragit L100-55 enteric coating capsules included film-coated pellets of theophylline in theoretical coating weight gains of 10, 15, and 20%, with pectin-chitosan complex contents of 5, 10, 15, and 20% for each level of weight gain were prepared and subjected to in vitro drug release. Drug release from this system showed a bimodal release profile characteristic with the drug release enhancement, being triggered (burst release) in the colonic medium. The reason for burst drug release may be due to the enzymatic degradation of pectin via pectinolytic enzymes in the simulated colonic medium. The mechanism of drug release from each formulation was evaluated in the terms of zero-order, first-order, Higuchi and Korsmeyer-Peppas models. It was observed that none of the enteric coating capsules showed any drug release in the simulated gastric medium (phase I). The analysis of release profiles showed that zero-order kinetics was found as the better fitting model for all formulations in the simulated small intestine (phase II) and it could be due to the pectin-chitosan swelling and subsequent formation of aqueous channels. In the colonic medium (phase III), due to degradation of pectin and its leaching from the mixed-film, there was a modification in drug release kinetics from swelling-controlled at phase II to anomalous at phase III. It also was found that both zero-order and Higuchi models contributed in colonic drug release from most of the formulations.

Preparation and characterization of free mixed-film of pectin/chitosan/Eudragit RS intended for sigmoidal drug delivery.

Polyelectrolyte complex (PEC) film between pectin as an anionic polyelectrolyte and chitosan as a cationic species was prepared by blending two polymer solutions at weight ratio of 2:1 and then solvent casting method. Besides pectin/chitosan PEC film, Eudragit RS, pectin/Eudragit RS and pectin/chitosan/Eudragit RS films were also prepared by aforementioned method. In mixed-film formulations, a fixed weight ratio of 1:5 of pectin or pectin/chitosan complex to Eudragit RS was used. Characterizations of pectin/chitosan interaction in solution were investigated by turbidity and viscosity measurement and in the solid state by Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXRD) and thermogravimetric analysis (TGA). It was observed that the swelling profile of pectin/chitosan film was pH-dependent and its swelling ratio in phosphate buffer solution (PBS) pH 7.4 was about 2.5-fold higher than that of PBS pH 6.0. Formulation containing only pectin/chitosan could not protect free film from high swelling in the aqueous media, therefore, Eudragit RS as a water-insoluble polymer must be included in the mixed-film. The formation of PEC between pectin and chitosan resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. Drug permeation or diffusion studies were carried out using Plexiglas diffusion cell consisting of donor and acceptor compartments. Theophylline was selected as a model drug to measure permeability coefficient. Drug permeation through pectin/chitosan/Eudragit RS showed a sigmoidal pattern; whereas drug diffusion through pectin/Eudragit RS and Eudragit RS films followed a linear characteristic. The drug permeation through the ternary mixed-film showed a burst release upon exposure to PBS pH 6.0. This mixed-film formulation showed the potential for sigmoidal drug delivery with an initial, controllable slow release followed by a burst release immediately after the change in pH. The burst drug permeation might possibly be due to change in film's porosity.

Pectin/chitosan/Eudragit RS mixed-film coating for bimodal drug delivery from theophylline pellets: preparation and evaluation.

Pellets containing theophylline as a model drug and microcrystalline cellulose, in a ratio of 6:4, were prepared by the extrusion-spheronization method. The pellets were coated with Eudragit RS aqueous dispersions, containing various amounts of pectin-chitosan complex and different coating mass gains, using a fluidized-bed apparatus. Twelve formulations were developed, which differed in two factors: coating mass gain (10, 15 and 20%, m/m) and the amount of pectin-chitosan complex (5, 10, 15 and 20%, m/m). Drug release studies were conducted using the USP apparatus I (basket) in dissolution media, mimicking the conditions prevailing in the stomach, small intestine or colon. Studies have shown that the drug release rate and pattern were dependent on both of the two mentioned factors. Some formulations showed bimodal and burst drug release, being triggered in the colonic medium by the action of pectinolytic enzymes. In formulations with 15 or 20% (m/m) of coating mass gain and 5 or 10% (m/m) of pectin-chitosan, the burst drug release was eliminated and replaced by the lag phase of drug release. In the case of burst drug release in the colonic medium, formulations with 20% (m/m) of coating mass gain and 15 or 20% (m/m) of pectin-chitosan were found to be better than the other formulations. Studies on the surface SEMs of uncoated and coated pellets show that after coating, coated pellets become smoother and exposure to pectinolytic enzymes in the colonic medium may result in surface erosion.