Antimicrobial actions of benzimidazoles against oral streptococci

BACKGROUND/AIM: Benzimidazoles, such as lansoprazole and omeprazole, are used extensively as proton-pump inhibitors to control stomach acid secretion and also have antimicrobial actions against Helicobacter pylori. Our objective was to determine whether they are potentially useful antimicrobials against oral bacteria. METHODS: Streptococcus mutans was our main test organism. It was grown in suspension cultures and biofilms. Standard physiologic assays were used to assess inhibitory actions of benzimidazoles. RESULTS: Benzimidazoles inhibited acid production by S. mutans in suspensions or biofilms. In pH-drop experiments, lansoprazole at a level of only 0.025 mm irreversibly inhibited acid production from glycolysis. Cell uptake of lansoprazole was found to be very pH sensitive and occurred mainly at pH values below about 5, indicating that the protonated form was taken up. Lansoprazole inhibition of glycolysis could be blocked by 2-mercaptoethanol, which suggests that disulfide bonds form between benzimidazoles and protein targets. Identified targets for benzimidazole inhibition included the phosphoenolpyruvate : sugar phosphotransferase system, the glycolytic enzymes aldolase, glyceraldehyde-3-phosphate dehydrogenase, and lactic dehydrogenase, and enzymes such as urease and arginine deiminase. Lansoprazole increased proton permeabilities of S. mutans cells but did not inhibit F-ATPases. Although cells in biofilms were somewhat less sensitive to the agents than those in suspensions, biofilm glycolysis was still markedly inhibited by 0.1 mm lansoprazole. Benzimidazoles are bactericidal, and the oral anaerobes Fusobacterium nucleatum and Prevotella intermedia were more sensitive to killing than was S. mutans. CONCLUSION: Benzimidazoles appear to be useful inhibitors of oral bacteria in acid environments such as progressing caries lesions.     

Antimicrobial activity of garlic against oral streptococci

Abstract:  The antimicrobial activity of two garlic clones' (1: purple and 2: white) crude extracts against oral microbiota was evaluated in vitro (study 1) and in vivo (study 2). Study 1 consisted of the evaluation of minimum inhibitory (MIC) and bactericidal (MBC) concentrations against nine streptococci strains. In study 2, a 2.5% garlic (clone 2) solution was used as a mouthwash in a 5-week study by 30 subjects. Blood agar and Mitis Salivarius Bacitracin agar were inoculated with subjects' saliva to quantify oral microorganisms and mutans streptococci. Study 1 showed MIC ranging from 0.5 to 32.0 mg ml⁻¹ for clone 2 and from 8 to 64.0 mg ml⁻¹ for clone 1. MBC ranged from 1.0 to 128.0 mg ml⁻¹ and from 8.0 to 128.0 mg ml⁻¹ regarding clones 2 and 1 respectively. Study 2 showed that 2.5% garlic mouthwash solution had good antimicrobial activity against mutans streptococci and oral microorganisms. Maintenance of reduced salivary levels of streptococci was observed after 2 weeks at the end of mouthwash use. Unpleasant taste (100%), halitosis (90%) and nausea (30%) were reported by subjects after the end of the study. It was concluded that the garlic clones have antimicrobial properties in vitro against streptococci and anticariogenic properties against oral microorganism in spite of its adverse effects.     

Influence of oral conditions on colonization by highly toxigenic Staphylococcus aureus strains

Oral Diseases (2012) 18 , 402–409 Objectives: As the oral cavity is regarded as a relevant site for Staphylococcus aureus colonization and interhuman transmission, this study aimed to investigate whether different oral conditions influence the rates of S. aureus oral carriage and genetic characters of S. aureus isolates. Subjects and methods: Staphylococcus aureus was searched in samples collected from cheek, gingival margin, and anterior nares of 45 healthy subjects, 27 periodontitis affected subjects, and 29 subjects with fixed prosthetic restorations. Isolates were screened for 17 genetic determinants, and Partial Least Square Discriminant Analysis was performed to evaluate whether specific characters correlated with oral condition or site of isolation. Results: The three subject groups showed comparable nasal carriage rates but, both the periodontitis and prosthetic restoration groups showed significantly higher oral carriage rates, as compared to healthy subjects (P = 0.01 and 0.02, respectively). Moreover, periodontitis affected subjects hosted strains possessing a distinct genotypic and phenotypic background, characterized by the presence of a larger number of exotoxins encoding genes. Conclusions: These data confirm that the oral cavity is an important site of S. aureus colonization and demonstrate that conditions modifying the oral environment, as the presence of periodontitis and of fixed prosthetic restorations, promote S. aureus carriage and may favor the spread of more pathogenic strains.     

Aminopeptidase activity in strains of oral streptococci

Ten strains of oral streptococci were analyzed for aminopeptidase activity by isoelectric focusing and crossed immunoelectrophoresis together with enzyme staining procedures. Substrate specificities were determined using 15 aminoacyl-β-naphthylamides. All 10 strains tested showed enzyme activity with the arginine and leucine substrates. None of the strains exhibited activity with the glycine, cystine, or proline substrates. Some strains had multiple enzyme bands with some of the substrates. All strains had aminopeptidase bands located in the pi range 4.1–4.3, except Streptococcus mutans IB and Streptococcus milleri NCTC 10708. The isoelectric profiles of these strains, having enzyme bands in the range 4.45–4.9, differed markedly from the others. These were also the only strains where no arginine aminopeptidase cross-reactivity occurred with the Streptococcus mitis ATCC 903 antiserum.     

Absorption of fibronectin from human saliva by strains of oral streptococci

Freshly collected human submandibular/sublingual saliva contained between 1.0 and 26.1 micrograms/ml of fibronectin as determined by ELISA. 10(9) organism of 12 oral streptococcal strains tested removed between 2.6 and 89.4% of the fibronectin present in 400 microliters saliva. Fibronectin was retained in bacterial pellets after washings in buffer but could be eluted using 1 M NaCl.     

Absorption of fibronectin from human saliva by strains of oral streptococci

Abstract — Freshly collected human submandibular/sublingual saliva contained between 1.0 and 26.1 μ/ml of fibronectin as determined by ELISA. 10⁹organisms of 12 oral streptococcal strains tested removed between 2.6 and 89.4% of the fibronectin present in 400 μl saliva. Fibronectin was retained in bacterial pellets after washings in buffer but could be eluted using 1 M NaCI     

Experimental endocarditis induced by dental manipulation and oral streptococci.

Circumstantial evidence has strongly implicated dental manipulation as an etiologic factor in the development of infective endocarditis. The introduction of human oral streptococci via the oral cavity in rabbits with vegetative cardiac lesions yields a 94 per cent incidence of infective endocarditis, if the number of inoculated organisms is above a threshold level of 10(7).     

Long-term periodical isolation of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) from Japanese children's oral cavities

IntroductionMethicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen causing nosocomial infections. To control nosocomial infection in a dental hospital, periodical surveillance of MRSA from the oral cavity is very important. Furthermore, this surveillance might reveal any alteration of the incidence of MRSA among healthy children in a particular area, because many children having no systemic disease except for dental problems come to dental offices.MethodsTotally 741 children were participated in the present study; 307 in 1987–88, 103 in 1992–93, 129 in 1997– 98 and 202 in 2002–2003. S. aureus was isolated from the tongues of children without systemic diseases. All isolates were investigated for coagulase types and susceptibilities to five antibiotics.ResultsS. aureus was isolated from 33–44% of children during the examination period. The incidence of MRSA was maximal in 1992–93, and then constant at around 3%. MRSA that have type II or III coagulase were relatively dominant.ConclusionAlthough outbreaks of MRSA in Japan was decreased in the early 90's, more than 3% of children without particular risks are considered positive for MRSA.     

Susceptibility and beta-lactamase-producing strains of methicillin-resistant Staphylococcus aureus

Thirty-three strains of methicillin-resistant Staphylococcus aureus (MRSA, MIC for methicillin greater than or equal to 16.0 micrograms/ml) isolated from sputum were examined for their susceptibilities against 8 antimicrobial agents. Ampicillin (ABPC), methicillin (DMPPC), cefazolin (CEZ), minocycline (MINO), erythromycin (EM), tobramycin (TOB), refampicin (RFP), and ofloxacin (OFLX) were used as the antimicrobial agents. The production of beta-lactamase was also determined. The results are as follows: 1) The highest susceptibility was given by RFP, and followed by MINO, and OFLX. All strains were resistant against EM and TOB. 2) The percentage of beta-lactamase-positive strains was 75.8%, which was distributed nearly identical among each MIC to DMPPC (72.0-77.8%). 3) Since the beta-lactamase-positive strains were found among the sensitive strains to ABPC, it was suggested that the use of beta-lactam antimicrobial agents might bring into the higher MIC value to ABPC. 4) Since there were beta-lactamase-negative strains among the resistant strains to ABPC, it was indicated that penicillin binding protein-2' might be produced by giving beta-lactam antimicrobial agents.     

Fatal Staphylococcus aureus infective endocarditis: The dental implications

Infective endocarditis remains an important and life-threatening infection despite improvements in diagnosis and management. There is currently a greater role for nosocomial acquisition of organisms and immunosuppression in the pathogenesis of this disease and emergence of a broader spectrum of infective organisms including those not commonly isolated from the mouth such as staphylococci. We report a case of infective endocarditis caused by Staphylococcus aureus in which the patient developed disseminated intravascular coagulation and multiple septic infarcts resulting in a frontal lobe brain abscess. Multiple dental extractions were complicated by delayed postextraction hemorrhage and the immediate cause of death was abdominal hemorrhage. The dental management in infective endocarditis should be planned in consultation with the attending physician, and should take into account both the causative organism and the presence of complications. When the oral cavity cannot be proven as the bacterial source for infective endocarditis, the immediate dental management should be directed toward improving the patient's oral hygiene and providing pain relief. Definitive long-term treatment, including any extractions, is ideally delayed until the patient has fully recovered from the infective endocarditis and its attendant complications.     

Fluoride uptake and fluoride resistance in oral streptococci

Fluoride uptake was examined in the highly F-sensitive Streptococcus salivarius strain 25975, the F-resistant mutant Flr103, and the relatively insensitive S. sanguis H7PR3. F was taken up by all strains from media at neutral pH, containing 1 or 10 micrograms F/ml (0.053-0.526 mmol/L), and uptake was directly proportional to the delta pH that was maintained by the cells. The final intracellular concentrations of F in the F-resistant strains were higher than those in the F-sensitive strain. Similar differences in F uptake were observed in buffer at pH 5.5, although both delta pH and F uptake were higher in all strains at the lower pH. These experiments demonstrate that resistance to F does not necessarily involve the exclusion of F from the cells. The lower uptake of F by F-sensitive cells is attributed to the finding that F dissipates the transmembrane pH gradient, and this, in turn, limits the concentration of intracellular F.     

Clonal structure of Streptococcus sanguinis strains isolated from endocarditis cases and the oral cavity

A collection of Streptococcus sanguinis strains from patients with endocarditis (n = 21) and from the oral cavity (n = 34) was subjected to a multi-locus sequence typing analysis using seven housekeeping genes, carbamoyl-phosphate synthetase (carB), Co/Zn/Cd efflux system component (czcD), d-alanyl-d-alanine ligase (ddl), DNA polymerase III (dnaX), glucose-6-phosphate dehydrogenase (gdh), DNA-directed RNA polymerase, beta subunit (rpoB) and superoxide dismutase (sodA). The scheme was expanded by the inclusion of two the putative virulence genes, bacitracin-resistance protein (bacA) and saliva-binding protein (ssaB), to increase strain discrimination. Extensive intra-species recombination was apparent in all genes but inter-species recombination was also apparent with strains apparently harbouring gdh and ddl from unidentified sources and one isolate harboured a sodA allele apparently derived from Streptococcus oralis. The recombination/mutation ratio for the concatenated housekeeping gene sequences was 1.67 (95% confidence limits 1.25-2.72) and for the two virulence genes the r/m ratio was 3.99 (95% confidence limits 1.61-8.72); recombination was the major driver for genetic variation. All isolates were distinct and the endocarditis strains did not form distinct sub-clusters when the data were analysed using ClonalFrame. These data support the widely held opinion that infecting S. sanguinis strains are opportunistic human pathogens.     

Antimicrobial resistance of aerobes and facultative anaerobes isolated from the oral cavity

Objectives

This study evaluated the resistance to antimicrobials of aerobes and facultative anaerobes isolated from patients wearing complete dentures, patients with gingivitis and periodontitis, and periodontally health subjects.

Material and methods

Three hundred and four isolates were tested. The minimal inhibitory concentrations of the drugs were evaluated through the agar dilution method using Mueller-Hinton agar.

Results

The most active antimicrobial drugs were the carbapenems (meropenem and imipenem), and resistance to these drugs was restrict to 1.6-2.3% of the isolates, as well as ciprofloxacin and rifampin. Microbial resistance to ampicillin, amoxicillin/clavulanic acid, cefoxitin, cephalothin, amikacin, chloramphenicol and nalidixic acid was particularly high. In most cases, the resistance to β-lactams was mediated by the production of hydrolytic enzymes, especially in gram-negative enteric rods, while enterococci did not evidence production of these enzymes. The association amoxicillin/clavulanic acid was not effective in 28.3% of the tested isolates.

Conclusions

The results of this investigation confirmed that the oral cavity of patients with periodontitis and gingivitis, and particularly edentulous patients wearing complete dentures, could harbor microorganisms with several antimicrobial resistance markers, and these microorganisms are frequently implicated in multiresistant, systemic, oral or nosocomial infections.     

Antibiotic susceptibility of Staphylococcus aureus isolates in oral mucosa and pockets of patients with gingivitis-periodontitis

Both oral cavity and subgingival pocket are ecological niches conducive to hosting microorganisms that may act as opportunistic pathogens, such as Staphylococcus aureus and especially methicillin-resistant Staphylococcus aureus (MRSA). Early detection of MRSA is a matter of concern to Public Health. The aim of our study was to determine phenotypic and genotypic detection of methicillin resistance of S. aureus in oral mucosa and subgingival pocket in 102 patients with gingivitis-periodontitis. The prevalence of S. aureus was 10.8% (n = 11) in subgingival pocket and 19.6% (n = 20) in oral mucosa. We obtained 31 isolates of S. aureus of which 13 were mecA positive and 18 were mecA negative. Detection of mecA gene by PCR was used as the reference method to compare the results of phenotypic methods to determine methicillin resistance. Early, accurate detection of S. aureus through phenotyping and genotyping methods is crucial for assessing the colonization and preventing the spread of MRSA.     

Two cases of oral infection by methicillin-resistant Staphylococcus aureus

Two cases of oral infection with multi-resistant Staphylococcus aureus (MRSA) are described who were found to carry the same MRSA. Both cases were managed without the use of antibiotics. The practitioner was found not to have worn gloves routinely and this may have been the source of the MRSA.     

Comparative cariogenicity of oral streptococci in different strains of gnotobiotic rats

Testing the cariogenicity of specific streptococci in gnotobiotic Sprague-Dawley rats in the U.S.A. and in gnotobiotic Liverpool-hooded and WAG rats in Britain produced very similar results. This suggests that the use of gnotobiotic rats is advantageous for inter-laboratory tests of the cariogenicity of streptococci.     

Antimicrobial resistance with focus on oral beta-lactamases

Over the last 10-15 yr antibiotic resistance has increased in the oral microflora. The beta-lactam antibiotics, i.e., penicillins and cephalosporins, are the most frequently used antimicrobial agents. Unfortunately, the efficiency of these drugs is increasingly being challenged by the emergence of resistant bacteria, which is mainly due to their production of beta-lactamases. In this paper, mechanisms of antibiotic resistance are reviewed, with emphasis on beta-lactamases. This review also discusses how the presence of beta-lactamases in oral microorganisms may affect the treatment of oral diseases. Dentists can influence the emerging global crisis of antibiotic resistance by carefully evaluating the indications for antibiotic treatment. General guidelines for when and how to use antibiotics in dentistry are reviewed.     

Salivary interactions with homologous and heterologous strains of oral streptococci and epithelial cells

Abstract Twenty strains of oral streptococci resembling the species of Streptococcus mitior and Streptococcus salivarius were isolated from four subjects and were incubated with homologous and heterologous whole clarified saliva. Supernatants of bacterially absorbed and control saliva were analyzed in tandem crossed immunoelectrophoresis (TCIE) against a rabbit anti-human saliva antiserum. Six to eight antigens were detected. After incubation with the bacteria, the saliva supernatants showed a decrease in the number of antigens detectable by TCIE. For all four salivas tested, the homologous group of strains absorbed fewer antigens. Some of the antigens could be eluted from bacterial pellets with 1 M NaCl after repeated washings in PBS. Epithelial cells also absorbed fewer antigens from homologous than heterologous saliva.