The most prevalent and worldwide oral disease is dental caries that affects a significant proportion of the world population. There are some classical approaches for control, prevention and treatment of this pathologic condition; however, the results are still not completely successful. Therefore new methods are needed for better management of this important challenge. Chitosan is a natural and non-toxic polysaccharide with many biological applications, particularly as an antimicrobial agent. Chitosan nanoparticle is a bioactive and environment friendly material with unique physicochemical properties. The aim of the present study was to investigate the antimicrobial effect of chitosan and nano-chitosan on the most important cariogenic streptococci. For evaluation of antimicrobial effect of chitosan and nano-chitosan against oral streptococci broth micro-dilution method was carried out for four bacterial species; Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguis and Streptococcus salivarius. Also the effect of these materials on adhesion of above bacteria was evaluated. One-way ANOVA and post hoc Tukey test were used for statistical analysis. The MICs of chitosan for S. mutans, S. sanguis, S. salivarius and S. sobrinus were 1.25, 1.25, 0.625 and 0.625 mg/mL, respectively. The MIC of chitosan nanoparticle for S. mutans, S. salivarius and S. sobrinus was 0.625 mg/mL and for S. sanguis was 0.312 mg/mL. Chitosan and chitosan nanoparticles at a concentration of 5 mg/mL also reduced biofilm formation of S. mutans up to 92.5% and 93.4%, respectively. The results of this study supported the use of chitosan and chitosan nanoparticles as antimicrobial agents against cariogenic Streptococci.

Characterization of Resistance to Aminoglycosides in Methicillin-Resistant Staphylococcus aureus Strains Isolated From a Tertiary Care Hospital in Tehran, Iran - Jundishapur Journal of Microbiology - - Kowsar

Background: Staphylococcus aureus is associated with different infections ranging from skin and soft tissue infections to endocarditis and fatal pneumonia. S. aureus is still the most common bacterial species isolated from inpatient specimens and the second most common from outpatient specimens. Today, methicillin resistant S. aureus (MRSA) isolates are present in the hospitals of most countries and are often resistant to several antibiotics. Objectives: This study was conducted from 2007 to 2011 to detect prevalence and antibiotic resistance patterns among MRSA and methicillin sensitive S. aureus (MSSA) isolated from hospitals in Tehran, Iran. Materials and Methods: Totally 726 isolates of S. aureus were collected from three referral hospitals in Tehran. All isolates were identified at the species level by standard biochemical tests. Susceptibility to eighteen antibiotics was determined by disc diffusion method. Then oxacillin and vancomycin minimum inhibitory concentration (MIC) of resistant isolates was also determined using Etest. mecA gene was detected using specific primers. Results: A total of 216 (30%) strains were found to be MRSA isolates. The highest antibiotic resistance was to penicillin, clindamycin, tobramycin and tetracycline respectively. Ninety three and 61% of MRSA and MSSA isolates were multidrug resistant (MDR) respectively. However, no strain was resistant to vancomycin, synercid, linezolid and chloramphenicol. Sixty nine percent of MRSA isolates showed high level of resistance to oxacillin (MIC ≥ 256 µg/ml). mecA gene was detected among all MRSA isolates. Conclusions: Although the frequency of MRSA isolates in the current study was low, resistance to other antibiotics was high and most of the isolates were found to be MDR. Regular surveillance of hospital-associated infections and monitoring of their antibiotic sensitivity patterns are required to reduce MRSA prevalence. High frequency of MDR isolates of S. aureus could be considered as an urgent warning for public health. Keywords: Staphylococcus aureus; Vancomycin; Iran

Staphylococcus aureus is a leading cause of hospital-acquired (HA) and community-acquired (CA) infections worldwide. Recently, S. aureus strains resistant to meticillin (MRSA) have become established within both communities. We isolated 314 isolates of MRSA from hospitalized patients in a referral hospital (HA isolates) and 268 isolates from its outpatient clinic (CA isolates) in Tehran, Iran, between February 2008 and December 2010. These isolates were tested for their susceptibility to 17 antibiotics and typed using the PhPlate system. The diversity in the structures of staphylococcal cassette chromosome mec (SCCmec) elements and ccr types was also detected using a multiplex-PCR assay and isolates were examined for the presence of different classes of prophages. Whilst all isolates were resistant to penicillin, the HA isolates were significantly more resistant to all other antibiotics tested than the CA isolates. Isolates carrying only SCCmec type III and ccr type 3 were dominant (91%), but 20% of the CA isolates belonging to less prevalent types carried only SCCmec types IVa, c and ccr type 2. These isolates also carried pvl genes and contained SGA prophage type. Our results indicate that whilst the dominant clonal groups of HA- and CA-MRSA belong to SCCmec type III and carry ccr type 3 genes, several distinct but less prevalent types of CA-MRSA carrying SCCmec type IVa, c and type 2 ccr are also found in Tehran. These strains carry pvl genes and the SGA prophage type, a characteristic that might be used as a marker for detection of CA-MRSA in this country.