Introduction: Dental caries is an infectious disease mostly associated with streptococcal species, especially Streptococcus mutans, as the main etiologic agent. Zoocin A protein is extracted as a recombinant protein from Streptococcus zooepidemicus and Escherichia coli with high effect on S. mutans. Clove extract has also been shown to have antimicrobial effects on several bacterial species, such as S. mutans. Objectives: The purpose of this study was to isolate and identify common bacteria causing dental caries and their susceptibility to zoocin A and clove extract. Patients and Methods: This study was performed on 133 dental caries samples in Tehran province. The isolates were identified by phenotypic and molecular methods. Molecular identification was performed by 16S rRNA gene sequence. The effects of antibiotics, zoocin A and clove extract were studied.Results: There was no significant difference between men and women regarding dental caries (P = 0.422), but age group of 16-30 years were the most common (P = 0.002). Dominant biofilm forming bacteria identified with 16srRNA analysis including S. mutans, S. mitis, S. sanguinis, S. gordonii, Lactobacillus gasseri, Jemela hemolysin, and Granulicatella adiacens. Zoocin A exhibited a strong inhibitory effect with minimum inhibitory concentration (MIC) range of 2-4 µg/mL mostly against S. mutans. MIC of hydroalcoholic extract of clove was 8-16 µg/mL. Conclusion: Streptococcal species were predominant causes of tooth decay. Zoocin A and clove extract showed antimicrobial activity even on antibiotic-resistant and biofilm-forming species causing tooth decay.

Background The most common clinical manifestations of Staphylococcus aureus strains in the community are skin and soft-tissue infections. S. aureus could colonize the body sites and complicate the pathogenesis of skin diseases. S. aureus colonization is a risk factor for severe conditions such as bone and joint infections, pneumonia, bacteremia, and endocarditis. This study aimed to investigate the prevalence of S. aureus strains in skin and soft tissue infections and other skin disorders in patients referring to dermatology clinics and to evaluate the antibiotic resistance pattern and molecular characteristics of S. aureus isolates. Methods Skin swabs were collected from the lesional sites in 234 outpatients referring to dermatology clinics in three hospitals in Tehran. Antibiotic susceptibility, biofilm formation, and hemolysis tests were performed for isolates. PCR was done for SCCmec typing, agr grouping, and virulence genes detecting. Results The prevalence of S. aureus strains among patients with skin and soft-tissue infections and other skin lesions was 44.77% (30/67) and 44.91% (75/167), respectively. Also, 59 (56.19%) isolates were MRSA, 35.57% were HA-MRSA, and 30.5% were CA-MRSA. The psmα gene was more prevalent (62.8%) among isolates, followed by hlaα (56.1%), tsst-1 (15.2%) eta (13.3%), etb (6.6%), and pvl (2.8%). The agr specificity groups I, II, III, and IV were identified in 49.5, 21.9, 11.4, and 14.2% of S. aureus isolates, respectively. Most (56%) S. aureus isolates produced a moderate biofilm, and 23.8% of them produced strong biofilms. α-hemolysin (46.6%), β-hemolysin (25.7%), γ-hemolysin (19%), and both α and β-hemolysin (5.7%) were also produced by isolates. Conclusion The present study results indicated high colonization of skin lesions by HA-MRSA and CA-MRSA clones; MRSA strains were more resistant to antibiotics, contained various toxin genes, and were able to form biofilms. Therefore, they could play a vital role in the pathogenesis of various skin diseases; also, they could spread and cause infections in other body sites. Eradication and decolonization strategies could prevent recurrent infections and the spread of resistant strains and improve skin conditions.