Mutans Group Research Articles

Strategic Protein Target Analysis for Developing Drugs to Stop Dental Caries

Dental caries is the most common disease to cause irreversible damage in humans. Several therapeutic agents are available to treat or prevent dental caries, but none besides fluoride has significantly influenced the disease burden globally. Etiologic mechanisms of the mutans group streptococci and specific Lactobacillus species have been characterized to various degrees of detail, from identification of physiologic processes to specific proteins. Here, we analyze the entire Streptococcus mutans proteome for potential drug targets by investigating their uniqueness with respect to non-cariogenic dental plaque bacteria, quality of protein structure models, and the likelihood of finding a drug for the active site. Our results suggest specific targets for rational drug discovery, including 15 known virulence factors, 16 proteins for which crystallographic structures are available, and 84 previously uncharacterized proteins, with various levels of similarity to homologs in dental plaque bacteria. This analysis provides a map to streamline the process of clinical development of effective multispecies pharmacologic interventions for dental caries.

Cariogenic bacteria and diet according to nutritional status in pre‐school children

Dental caries is a multifactorial disease, and diet, closely associated with nutritional status (NS), plays an essential role. However, the relation between these factors has not been thoroughly studied to date. To clarify the relationship between NS and cariogenic bacteria, eighty four children aged 59.2 ± 12.8 months, attending a day care center, were examined. They were classified by Body Mass Index Z‐scores (WHO, 2007) in adequate (A), overweight (OW) or obese (O). Carbohydrate consumption frequency between meals/day (CH), cariogenic risk (CR), and colony‐forming unit/ml saliva (CFU) of streptococci and lactobacilli were assessed.NS showed 46% of children A, 30% OW and 18% O. Although CH did not differ significantly among groups (p>0.05), O presented less children with high CR (A:62, OW:77 and O:50%, p<0.05). The number of CFU of Streptococcus mutans group did not differ significantly, but CFU of Lactobacillus acidophilus was reduced in O (O:2241±1586 vs A:3700±1710 and OW:2715±1793, p<0.05).Thus, these results suggest an association among NS, diet and microbiology composition of dental biofilm that leads to a negative relationship between obesity and caries risk.

Polymerase Chain Reaction for detection of Streptococcus mutans and Streptococcus sobrinus in dental plaque of children from Cartagena, Colombia

Objectives: To detect the presence of Streptococcus mutans and Streptococcus sobrinus in dental plaque of children from Cartagena and correlate it to dental caries precavity stages, applying a standardized PCR-based technique for epidemiological purposes.Methods: Descriptive study using a non-probabilistic sample of 50 children between 3 and 5 years of age, preschoolers from a Caribbean population in Colombia. Criteria for selection were that children should exhibit plaque accumulations on the surface of the cervical margins of the rearmost molars, and placed in one of two study groups: carious lesions and sound surfaces. Dental plaque samples from both groups were subjected to molecular analysis and statistical analysis was applied to determine the difference between the two groups using the frequencies of presence of S. mutans, S. sobrinus or both in thetwo groups applying Fisher’s exact test for association between the presence of microorganisms and the state of the tooth surface from where the dental plaque was taken.Results: The frequency of S. mutans in carious lesions was 76% and 24% in healthy surfaces. The frequency of S. sobrinus in carious lesions was 81.9% and 18.1% in caries-free surfaces. There was statistical significance between the presence of S. mutans and the presence of caries (p=0.001) and between the presence of S. sobrinus (p=0.02) and the presence of caries.There was no statistical significance between the presence of caries and the simultaneous presence of both microorganisms (p=0.08).Conclusions: The presence of S. mutans and S. sobrinus in dental plaque samples is highly prevalent and associated to non cavitated carious lesions, being the molecular identification of these microorganisms by PCR a sensitive, fast, and easy to use detection method for the mutans group of oral bacteria.

Antimicrobial activity of Calendula officinalis, Camellia sinensis and chlorhexidine against the adherence of microorganisms to sutures after extraction of unerupted third molars

ObjectiveThe objective of this study was to compare the antimicrobial effect of mouthwashes containing Calendula officinalis L., Camellia sinensis (L.) Kuntze and 0.12% chlorhexidine digluconate on the adherence of microorganisms to suture materials after extraction of unerupted third molars. Material and MethodsEighteen patients with unerupted maxillary third molars indicated for extraction were selected (n=6 per mouthwash). First, the patients were subjected to extraction of the left tooth and instructed not to use any type of antiseptic solution at the site of surgery (control group). After 15 days, the right tooth was extracted and the patients were instructed to use the Calendula officinalis, Camellia sinensis or chlorhexidine mouthwash during 1 week (experimental group). For each surgery, the sutures were removed on postoperative day 7 and placed in sterile phosphate-buffered saline. Next, serial dilutions were prepared and seeded onto different culture media for the growth of the following microorganisms: blood agar for total microorganism growth; Mitis Salivarius bacitracin sucrose agar for mutans group streptococci; mannitol agar for Staphylococcus spp.; MacConkey agar for enterobacteria and Pseudomonas spp., and Sabouraud dextrose agar containing chloramphenicol for Candida spp. The plates were incubated during 24-48 h at 37ºC for microorganism count (CFU/mL). ResultsThe three mouthwashes tested reduced the number of microorganisms adhered to the sutures compared to the control group. However, significant differences between the control and experimental groups were only observed for the mouthwash containing 0.12% chlorhexidine digluconate. ConclusionsCalendula officinalis L. and Camellia sinensis (L.) Kuntze presented antimicrobial activity against the adherence of microorganisms to sutures but were not as efficient as chlorhexidine digluconate.

Effects of silver diamine fluoride on dentine carious lesions induced by Streptococcus mutans and Actinomyces naeslundii biofilms

BACKGROUND. Silver diamine fluoride (SDF) has been shown to be a successful treatment for arresting caries. However, the mechanism of SDF is to be elucidated. AIM. To characterize the effects of SDF on dentine carious induced by Streptococcus mutans and Actinomyces naeslundii. DESIGN. Thirty-two artificially demineralized human dentine blocks were inoculated: 16 with S. mutans and 16 with A. naeslundii. Either SDF or water was applied to eight blocks in each group. Biofilm morphology, microbial kinetics and viability were evaluated by scanning electron microscopy, colony forming units, and confocal microscopy. The crosssection of the dentine carious lesions were assessed by microhardness testing, scanning electron microscopy with energy-dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. RESULTS. Biofilm counts were reduced in SDF group than control (P < 0.01). Surfaces of carious lesions were harder after SDF application than after water application (P < 0.05), in S. mutans group, Ca and P weight percentage after SDF application than after water application (P < 0.05). Lesions showed a significantly reduced level of matrix to phosphate after SDF treatment (P < 0.05). CONCLUSION. Present study showed that SDF posses an anti-microbial activity against cariogenic biofilm of S. mutans or A. naeslundii formed on dentine surfaces. SDF slowed down demineralization of dentine. This dual activity could be the reason behind clinical success of SDF.

Streptococcus mutans et les streptocoques buccaux dans la plaque dentaire

The human oral microbial biota represents a highly diverse biofilm. Twenty-five species of oral streptococci inhabit the human oral cavity and represent about 20 % of the total oral bacteria. Taxonomy of these bacteria is complex and remains provisional. Oral streptococci encompass friends and foes bacteria. Each species has developed specific properties for colonizing the different oral sites subjected to constantly changing conditions, for competing against competitors, and for resisting external agressions (host immune system, physico-chemical shocks, and mechanical frictions). Imbalance in the indigenous microbial biota generates oral diseases, and under proper conditions, commensal streptococci can switch to opportunistic pathogens that initiate disease in and damage to the host. The group of "mutans streptococci" was described as the most important bacteria related to the formation of dental caries. Streptococcus mutans, although naturally present among the human oral microbiota, is the microbial species most strongly associated with carious lesions. This minireview describes the oral streptococci ecology and their biofilm life style by focusing on the mutans group, mainly S. mutans. Virulence traits, interactions in the biofilm, and influence of S. mutans in dental caries etiology are discussed.

Investigation of Supragingival Plaque Microbiota in Different Caries Status of Chinese Preschool Children by Denaturing Gradient Gel Electrophoresis

This study aimed to detect differences in the richness of total supragingival plaque microbiota as well as the species composition of oral streptococci involved in the different stages of dental caries. Forty-five plaque samples were collected from caries-moderate (CM, 4 ≤ dmfs ≤ 6), caries-susceptible (CS, dmfs ≥ 10), and age-matched caries-free children separately. Total DNA was isolated directly from each sample, and polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses using universal and primers specific for oral streptococci were carried out. Using 16S rDNA PCR-DGGE, 34 different species of bacteria were identified in a culture-independent manner and classified into 11 genera according to phylogenetic analysis. Among them, Mitis group streptococci and Campylobacter, which were present in health status, no longer appeared in caries-susceptible samples. In addition, Capnocytophaga, Burkholderia, and Prevotella were found significantly less frequently in the CS group samples (P < 0.05), while there were no significant differences among the prevalence of Neisseria, Leptotrichia, Haemophilus, Mutans group streptococci, Corynebacterium, and Actinomyces in the three groups. Further DGGE analysis of rnpB gene amplicons obtained with oral streptococci species-specific primers showed that a total of 23 species of oral streptococci were identified. Streptococcus sanguinis, Streptococcus mitis, and Streptococcus oralis showed a significantly higher prevalence in healthy children (P < 0.05), while that of Streptococcus mutans and Streptococcus sobrinus did not vary among the three groups. Overall, these results suggest that supragingival plaque microbiota as a whole undergoes a more complicated shift in the caries process.

The viridans group streptococci

The viridans group streptococci (VGS) are an extremely diverse range of organisms within the genus Streptococcus, which are characterized by a greening of the blood in blood agar, on which they are normally grown. Oral streptococci largely comprise members of the VGS, which currently include 20 species, which are commensal inhabitants of the oropharyngeal cavity, and the gastrointestinal and genital tracts of mammals. On the basis of 16S rRNA sequence homology, these bacteria are categorised into four groups: the salivarius rRNA homology group, including Streptococcus thermophilus, Streptococcus vestibularis and Streptococcus salivarius; the mitis group, including Streptococcus cristatus, Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis, Streptococcus pneumoniae, Streptococcus sanguinis and Streptococcus parasanguinis; the anginosus group, including Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius; and the mutans group, including Streptococcus mutans, Streptococcus criceti, Streptococcus downei, Streptococcus ferus, Streptococcus macacae, Streptococcus ratti and Streptococcus sobrinus. This review aims at comparing conventional and molecular detection methods and the emergence of antibiotic resistance within the VGS.

Detection of oral streptococci with collagen‐binding properties in saliva specimens from mothers and their children

Approximately 10-20% of Streptococcus mutans strains have been reported to possess collagen-binding properties, whereas other species in the oral cavity with those properties remain to be elucidated. Aim. To identify strains with collagen-binding properties and analyse their characteristics in comparison with S. mutans. A total of 110 expectorated saliva specimens were collected from 55 pairs of mothers and their children. Bacterial strains with collagen-binding properties were isolated and the species specified. In addition, strains with collagen-binding properties isolated from mother-child pairs were analysed using molecular biological approaches. The detection frequency of strains with collagen-binding properties was shown to be 40.9%, among which S. salivarius was the most frequently detected, followed by S. mutans. The collagen-binding activity of the S. mutans group was the highest, followed by S. salivarius. In addition, S. mutans and S. salivarius strains from 3 and 1 mother-child pairs, respectively, were shown to be the same clones. Our results indicate that S. mutans and S. salivarius are major species with collagen-binding properties in the oral cavity, and that strains with such properties may be related to mother-child transmission.

Atividade de um exaguatório bucal com clorexidina a 0,12% sobre a microbiota sacarolítica da saliva

Este trabalho avaliou a ação de um enxaguatório bucal com gluconato de clorexidina a 0,12% sobre o crescimento e produção de placa in vitro de estreptococos do grupo mutans e de outros microrganismos da saliva. A amostra foi composta por um pool de saliva, fracionada em duas partes, constituindo dois grupos. No grupo 1, adicionou-se 0,1 ml de saliva pura a tubos com caldo tioglicolato com 5% de sacarose e um bastão de vidro. No grupo 2, adicionou-se ao mesmo meio de cultura 0,1 ml de saliva previamente misturada a enxaguatório com gluconato de clorexidina a 0,12%, por 1 minuto. Após incubação a 37ºC, observou-se o aspecto dos meios de cultura e a presença de placa no bastão de vidro, seguindo-se de coloração de Gram e isolamento de estreptococos do grupo mutans. Em 100% dos tubos do grupo 1, observou-se produção de placa in vitro, turbidez e sedimento. Ao Gram, foram visualizados estreptococos, bacilos Gram positivos, bacilos Gram negativos, com alguns fusiformes e leveduras. Na cultura, foram isolados estreptococos do grupo mutans. No grupo 2, não houve produção de placa in vitro na maioria dos tubos (75%), e constatou-se escassez ou ausência de turbidez e sedimento, não sendo isolados estreptococos do grupo mutans. Nesse grupo, onde houve pouco crescimento bacteriano e placa in vitro (25%), foram isolados Streptococcus sp. Os resultados confirmaram a efetividade da clorexidina a 0,12% incorporada a enxaguatórios na redução da microbiota da saliva, inibição do crescimento de estreptococos do grupo mutans, leveduras e formação do biofilme dental.

Effect of an alcoholic diet on dental caries and on Streptococcus of the mutans group: study in rats

The objective of this study was to evaluate the effects of an alcohol diet on Streptococcus of the mutans group and on dental caries in the oral cavity of rats. Forty animals were divided into 3 groups according to the following liquid diets: 20% ethanol solution (Alcohol Group, AG), 27% sucrose solution (Isocaloric Group, IG), and water (Control Group, CG). After 56 days, samples were collected and plated on Mitis Salivarius Bacitracin agar to assess the number of colony forming units (CFU/mL) of Streptococcus of the mutans group. The animals were sacrificed and the jaws were removed in order to assess the occurrence of dental caries on the smooth and occlusal surfaces using stereomicroscopy. The data were submitted to ANOVA and Tukey test. The average numbers of CFU/mL (10(3)) were: 8.17 (AG), 9.78 (IG), and 5.63 (CG). There was no significant difference among the groups for the occurrence of occlusal caries. Regarding smooth surface caries, in the upper jaw, the caries number in the IG (1.58) was similar to that in the AG (2.06) and in the CG (1.14), and the number of caries in the AG was higher than in the CG; in the lower jaw there was significant difference among the 3 groups: AG (1.14), IG (2.00) and CG (0.43). The diets with the alcohol and sucrose solutions presented a tendency of increasing the colonization by Streptococcus of the mutans group and of increasing the occurrence of smooth surface dental caries in rat molars when compared to the control diet.

Streptococcus massiliensis sp. nov., isolated from a patient blood culture

An unidentified strain of the viridans group of streptococci was isolated from a human blood sample. It was distinguished from all other recognized species of the Streptococcus sanguinis group by several biochemical characteristics. Phylogenetic analysis based on 16S rRNA gene sequence comparisons clustered this strain with Streptococcus ferus (mutans group) but phylogenetic analysis based on rpoB and sodA gene sequence comparisons included it in the S. sanguinis group. The isolate showed 95.4 and 95.2 % 16S rRNA gene sequence similarity to S. ferus and S. sanguinis, respectively, confirming it as belonging to a novel taxon, for which the name Streptococcus massiliensis sp. nov. is proposed. The type strain is 4401825T (=CIP 108498T=CCUG 49690T).

The role of Streptococcus mutans group and salivary immunoglobulins in etiology of early childhood caries

Dental caries is a bacterial infective disease modified by carbohydrates from food. Early childhood caries is a special type of primary teeth caries in infants and toddlers. Appearance of early childhood caries (ECC) is related to mistakes in nutrition of infants, but the mechanism of beginning and progression of this disease is very complex. To understand etiology of caries, it is necessary to understand ecology of oral environment and to determine which factors are responsible for conversion of non-pathogenic microorganisms of the oral cavity into pathogenic. Among host factors, salivary immunoglobulin (sIgA) constitutes the main specific immune defense mechanism in saliva and may play an important role in the oral homeostasis. Basic role of salivary immunoglobulins is in control of bacterial oral flora and constitution of balance relationship between oral bacteria and organism as whole.

Oral microbial ecology in chronic periodontitis and periodontal health

Our aim was to find out differences between chronic periodontitis (CP) and periodontally healthy subjects with respect to oral lactic acid bacteria (LAB) as well as subgingival microbial relations. Clinical data, salivary levels of lactobacilli and mutans streptococci, and subgingival microbial samples were obtained from 26 CP and 15 periodontally healthy subjects. Antimicrobial activity of LAB against periodontal pathogens was assessed. We found Actinobacillus actinomycetemcomitans , Porphyromonas gingivalis and Prevotella intermedia/nigrescens in 54%, 23% and 73% of CP patients, respectively; the latter was also found in 47% of healthy subjects. The mean proportion of streptococci (27.0 vs 15.2%), particularly S. mutans group (5.7 vs 0.8%) and S. mitis group (18.1 vs 5.0%), as well as aerobic coryneforms (24.7 vs 11.9%) was higher in healthy persons (p< 0.05). An inverse relationship of subgingival streptococci and aerobic coryneforms with periodontal pathogens and deteriorated clinical parameters were seen. Salivary counts of mutans streptococci were higher in healthy persons. Inhibition of periodontal pathogens by LAB was observed. In conclusion, the proportions of oral LAB were significantly lower in CP than in healthy subjects, whilst being important antagonists against periodontal pathogens. These oral commensals may play an important role in the suppression of periodontal pathogens and maintenance of microecological balance in the oral cavity. Key words: Chronic periodontitis, periodontal health, lactic acid bacteria, subgingival microflora, antimicrobial activity, microbial ecology

Species identification of mutans streptococci by groESL gene sequence

The near full-length sequences of the groESL genes were determined and analysed among eight reference strains (serotypes a to h) representing five species of mutans group streptococci. The groES sequences from these reference strains revealed that there are two lengths (285 and 288 bp) in the five species. The intergenic spacer between groES and groEL appears to be a unique marker for species, with a variable size (ranging from 111 to 310 bp) and sequence. Phylogenetic analysis of groES and groEL separated the eight serotypes into two major clusters. Strains of serotypes b, c, e and f were highly related and had groES gene sequences of the same length, 288 bp, while strains of serotypes a, d, g and h were also closely related and their groES gene sequence lengths were 285 bp. The groESL sequences in clinical isolates of three serotypes of S. mutans were analysed for intraspecies polymorphism. The results showed that the groESL sequences could provide information for differentiation among species, but were unable to distinguish serotypes of the same species. Based on the determined sequences, a PCR assay was developed that could differentiate members of the mutans streptococci by amplicon size and provide an alternative way for distinguishing mutans streptococci from other viridans streptococci.

Differentiation of mutans streptococci by intact cell matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

It is difficult to distinguish mutans streptococci on the species level, and even more so on the subspecies level. Intact cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) (ICM) was applied to reference strains of five of the species of the mutans group (Streptococcus criceti, Streptococcus downei, Streptococcus mutans, Streptococcus ratti, Streptococcus sobrinus), nonmutans streptococci (Streptococcus oralis, Streptococcus mitis, Streptococcus salivarius, and Streptococcus sanguinis), and 177 mutans streptococci isolated from saliva of 10 children. From the analysis of the reference strains, readily distinguishable ICM mass spectra were obtained for the different species. Based on multivariate statistical analysis, a correct and unambiguous assignment was made of the spectra of 159 isolated mutans streptococci to S. mutans and 16 isolates to S. sobrinus. Two isolates were sorted out and were identified by sequencing of their 16S rRNA genes as Streptococcus anginosus. In addition, ICM indicated a misclassification for some reference strains (AHT, V 100 and E 49) and re-classified AHT and E 49 as S. ratti and V 100 as S. sobrinus. This was confirmed by 16S rDNA sequencing. Based on a statistical similarity analysis of the spectra of reference strains and a quantitative assessment of the reproducibility of ICM, the isolates identified as either S. mutans or S. sobrinus were phenotyped on the subspecies level. In the population of the clinical isolates, 14 unambiguously different S. mutans and three different S. sobrinus phenotypes were detected. ICM proved to be a powerful tool for a differentiation of mutans streptococci down to the subspecies level.

Oral microbial ecology in chronic periodontitis and periodontal health

Our aim was to find out differences between chronic periodontitis (CP) and periodontally healthy subjects with respect to oral lactic acid bacteria (LAB) as well as subgingival microbial relations. Clinical data, salivary levels of lactobacilli and mutans streptococci, and subgingival microbial samples were obtained from 26 CP and 15 periodontally healthy subjects. Antimicrobial activity of LAB against periodontal pathogens was assessed. We found Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia/nigrescens in 54%, 23% and 73% of CP patients, respectively; the latter was also found in 47% of healthy subjects. The mean proportion of streptococci (27.0 vs 15.2%), particularly S. mutans group (5.7 vs 0.8%) and S. mitis group (18.1 vs 5.0%), as well as aerobic coryneforms (24.7 vs 11.9%) was higher in healthy persons (p < 0.05). An inverse relationship of subgingival streptococci and aerobic coryneforms with periodontal pathogens and deteriorated clinical parameters were seen. Salivary counts of mutans streptococci were higher in healthy persons. Inhibition of periodontal pathogens by LAB was observed. In conclusion, the proportions of oral LAB were significantly lower in CP than in healthy subjects, whilst being important antagonists against periodontal pathogens. These oral commensals may play an important role in the suppression of periodontal pathogens and maintenance of microecological balance in the oral cavity.

Inhibition of Cariogenic Factors of Mutans Streptococci by Persimmon Tannin

Persimmon tannin is especially known well as a fruit polyphenol. It inhibited the growth of streptococci of the mutans group. It also exhibited a strong inhibitory effect on glucosyltransferase-1(GTase-1) activity. The sucrose-dependent adherence of the bacterial cells was examined with persimmon tannin in vitro. The tannin inhibited the production of adherent materials at the lowest concentration among the polyphenols tested. Persimmon tannin exhibited an inhibitory effect on cariogenic factors at the steps of tooth-decaying bacterial growth, insoluble glucan synthesis, and dental plaque formation, and is expected to be a used for the prevention of dental caries.

Method for rapid identification of oral streptococci by PCR using 16S-23S ribosomal RNA intergenic spacer gene

Mutans group streptococci play an important role in the formation of dental caries, while mitis group streptococci are considered to be associated with subacute bacterial endocarditis. Both mitis and salivarius group streptococci, which are early colonizers in the human oral cavity, have an effect on the infection and colonization of mutans streptococci. In the present study, a rapid and exact PCR method to detect those oral streptococci was developed using the 16S-23S ribosomal RNA intergenic spacer gene, which is present between 16S rRNA and 23S rRNA within the RNA operon. The PCR analysis was able to correctly identify mutans and mitis group streptococcal species. Our results indicate that the combined PCR analysis method established in the present study is useful for detecting oral streptococcal species, as well as in clinical applications to predict and prevent dental caries and etiological studies of streptococcal infective endocarditis.

Bactericidal effects of a fusion protein of llama heavy-chain antibodies coupled to glucose oxidase on oral bacteria.

Enzymes such as lactoperoxidase and glucose oxidase (GOx) are used as antimicrobial agents in oral care products. Their low specificities and substantiveness can be reduced by covalent coupling of antimicrobial molecules to antibodies. Variable domains (V(HH)) derived from llama heavy-chain antibodies are particularly suited for such an approach. The antibodies are composed solely of heavy-chain dimers; therefore, production of active fusion proteins by using molecular biology-based techniques is less complicated than production by use of conventional antibodies. In this study, a fusion protein consisting of V(HH) and GOx was constructed and expressed by Saccharomyces cerevisiae. A llama was immunized with Streptococcus mutans strain HG982. Subsequently, B lymphocytes were isolated and cDNA fragments encoding the V(HH) fragments were obtained by reverse transcription-PCR. After construction of a V(HH) library in Escherichia coli and screening of the library against mutans group streptococci and Streptococcus sanguinis strains, we found two V(HH) fragments with high specificities for S. mutans strains. A GOx gene was linked to the two V(HH) genes and cloned into S. cerevisiae yeasts. The yeasts expressed and secreted the recombinant proteins into the growth medium. The test of binding of fusion proteins to oral bacteria through their V(HH) fragments showed that S. mutans had been specifically targeted by GOx-S120, one of the fusion protein constructs. A low concentration of the fusion protein was also able to selectively kill S. mutans within 20 min in the presence of lactoperoxidase and potassium iodide. These findings demonstrate that the fusion protein GOx-V(HH) is potentially valuable in the selective killing of target bacteria such as S. mutans.