The development of penicillin-resistant oral streptococci after repeated penicillin prophylaxis

Oral streptococci may cause infective endocarditis in patients with susceptible cardiac disease after dental treatment. Multiple dental visits, each preceded by penicillin prophylaxis, may result in the unwanted development of resistant oral streptococci. This study was undertaken to determine whether resistant oral streptococci would develop after the repeated use of penicillin prophylaxis in healthy adults. Plaque samples were collected from 20 subjects on each Monday for 5 successive weeks. Each subject was administered 2 gm penicillin V followed by 1 gm 6 hours later (standard prophylaxis regimen of the American Heart Association), on three successive Mondays (weeks 2, 3, and 4). The total cultivable oral streptococci and penicillin-resistant oral streptococci were determined for each plaque sample, and representative colonies of resistant streptococci were speciated. During the study, there was a significant increase in the number of subjects who harbored penicillin-resistant oral streptococci. However, with the exception of one subject who had resistant streptococci throughout the study, the number of resistant strains represented only 0.0003% to 0.41% of the total cultivable oral streptococci.     

Antibiotic prophylaxis for endocarditis in patients with a prosthetic heart valve.

A review of the types of organisms and their sensitivities to antibiotics, as well as the source of infection, was carried out for 11 patients who had late onset infective endocarditis and a prosthetic heart valve. Candida organisms were isolated from two patients. In nine patients with late onset bacterial endocarditis, the organisms isolated were five streptococci and four staphylococci. Their sensitivities to antibiotics were penicillin, five of eight; erythromycin, eight of eight; and cephalothin, six of seven. Two patients with endocarditis had ulcerations beneath their dentures, and one had undergond a prior dental procedure. Of 52 healthy patients with prosthetic valves who were interviewed, only 18 had visited a dentist during the previous year, and six did not receive antibiotic prophylaxis for endocarditis. It is concluded that patients with prosthetic heart valves do not practice good oral hygiene and, if they do visit the dentist, some may not receive antibiotics for endocarditis prevention. An antibiotic regimen for endocarditis is presented that is consistent with the organisms found in the oral cavity and those found in patients with endocarditis who have a prosthetic valve.     

New concept in chemoprophylaxis of bacterial endocarditis resulting from dental treatment

Bacteremia following dental procedures may lead to bacterial endocarditis in susceptible patients. Traditional methods of chemoprophylaxis with a parenteral loading dose of penicillin followed by oral penicillin have proved impractical outside the hospital. In 1978, it was suggested in England that amoxicillin be substituted as the drug of choice in the prophylaxis of bacterial endocarditis. The recommended mode of treatment was a single oral dose of 3 g amoxicillin administered 1 hour before onset of the dental procedure. Amoxicillin is absorbed to a greater extent and more rapidly than penicillin V. It maintains its effectiveness throughout the critical postoperative period at concentrations well over the minimum necessary to combat Streptococcus viridans. Amoxicillin has two mechanisms of protection: bactericidal and inhibition of bacterial adherence to the thrombotic vegetation on injured heart valves. Data obtained from 206 susceptible patients undergoing dental treatment under chemoprophylaxis with amoxicillin showed that in no case did infective endocarditis occur. Only in 13.1% of the patients could very mild side effects of this drug be observed. With this new method, there is a higher incidence of patient compliance and administration is easier to supervise.     

Antimicrobial resistance of Staphylococcus aureus and oral streptococci strains from high-risk endocarditis patients

This study sought to determine the antimicrobial susceptibility of Staphylcoccus aureus and viridans group streptococci strains collected from the forearm skin and saliva of 30 patients at high risk of endocarditis. Agar susceptibility tests of antibiotics routinely utilized in dentistry were used to verify antimicrobial resistance of bacterial strains. Of the Staphylcoccus aureus strains, 50% were resistant to ampicillin, 53.3% to amoxicillin, 60.0% to penicillin G, 13.3% to amoxicillin/clavulanate, 20.0% to azithromycin, 27.6% to clarithromycin, 23.3% to erythromycin, 3.3% to cefazolin, and 6.7% to clindamycin. Regarding streptococci, 16.7% of the strains were resistant to ampicillin, 16.7% to amoxicillin, 23.3% to azithromycin, 23.3% to clarithromycin, 30.0% to erythromycin, 13.3% to cefazolin, 26.7% to clindamycin, 16.7% to penicillin G, and 3.3% to amoxicillin/clavulanate. Pathogens associated with bacterial endocarditis exhibited elevated resistance rates against the antibiotics used for prophylaxis in dentistry.     

Gentamycin for prophylaxis of bacterial endocarditis: a review for the dentist

New guidelines have recommended that gentamicin in combination with ampicillin be used for prophylaxis of bacterial endocarditis in patients with prosthetic heart valves. This article reviews some of the important and practical considerations for its use by the dentist. Gentamicin is an aminoglycoside antibiotic most exclusively reserved for treatment of serious infections caused by gram-negative bacteria in which less toxic antibacterials are ineffective. It has also been shown to be impressive in combination with penicillin in treating high-risk endocarditis patients. All strains of enterococci that are resistant to penicillin plus streptomycin are almost always sensitive to penicillin plus gentamicin. There is minimal absorption into the bloodstream from the gastrointestinal tract after oral administration but rapid absorption after intramuscular injection. Peak serum concentrations appear 30 to 90 minutes after intramuscular injection. The T1/2 is 2 hours, and in normal kidneys 85% to 95% of the drug is excreted within 24 hours by glomerular filtration. Ototoxicity and nephrotoxicity are the most serious toxic effects resulting from gentamicin therapy. The incidence of ototoxicity is about 2%, with affected patients experiencing vestibular effects rather than hearing loss. Nephrotoxicity is usually not seen before the patient has had 5 to 7 days of frequent dosing for treatment of systemic infections; the incidence is 2% to 4%. There are no data to suggest that ototoxicity or nephrotoxicity will occur in the patient given a single intramuscular injection of gentamicin for the prophylaxis of bacterial endocarditis. A single intramuscular or intravenous injection each of ampicillin and gentamicin should provide adequate blood levels for protection in the endocarditis patient for at least 4 to 5 hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

Azithromycin and dentistry - a useful agent?

OBJECTIVES: Azithromycin has recently replaced clindamycin oral suspension for prop hylaxis of infective endocarditis (IE) in children. It is also currently recommended by the American Heart Association as an alternative to penicillin, along with clindamycin for prophylaxis of infective endocarditis in adults. The objectives of this paper were to firstly, review the current literature on the efficacy of azithromycin as a suitable prophylactic agent in the prevention of infective endocarditis; and secondly, to review its pharmacological properties as a suitable therapeutic agent in the management of odontogenic infections. DESIGN: A review of the literature. CONCLUSIONS: The available evidence from animal models on infective endocarditis supports the efficacy of this drug as a prophylactic agent against oral streptococci. The pharmacological properties of this agent would make it a very promising therapeutic adjunct in the management of odontogenic infections. At present there are only a small number of studies available with valuable data on the efficacy of this relatively new drug. Further investigations comparing this compound with other commonly used adjuncts would be of great benefit.     

Failure of two macrolide antibiotics to prevent post-extraction bacteraemia.

Two macrolide antibiotics, erythromycin and josamycin, were compared in a double-blind trial to examine their efficacy in the prevention of post-dental extraction bacteraemia in a group of healthy patients. An in vitro blood culture system was used. Isolates of streptococci were identified to species level. Minimum inhibitory concentrations (MICs) of erythromycin and of josamycin for each isolate were estimated by an agar dilution technique, with controls. Levels of drug in the serum of volunteers and of patients were assayed after oral doses of the macrolide antibiotics. Levels found achieved early peaks and satisfactory concentrations for activity against streptococci. Within the specified parameters, the results demonstrated that the antibiotics failed to prevent survival in blood culture of various strains of streptococci for up to 24 hours following collection of the blood. It is recommended that an alternative antibiotic to either erythromycin or to josamycin be used to achieve prophylaxis against streptococci in infective endocarditis risk patients who are allergic to penicillin.     

Emergence of antibiotic resistant Streptococcus sanguis in dental plaque of children after frequent antibiotic therapy.

PURPOSE: In the pediatric population, several different antibiotic regimens are currently recommended for the treatment of otitis media. This study investigated whether therapy for otitis media was associated with the emergence of antibiotic-resistant oral bacteria. METHODS: Streptococcus sanguis (S. sanguis) was isolated from supragingival dental plaque of children after a recent course of antibiotic. The isolated strains were tested for resistance to penicillin, amoxicillin, trimethoprim-sulfamethoxazole, and erythromycin and compared to isolated strains from age- and sex-matched control subjects, who had received no antibiotics within two years before sampling. RESULTS: While control subjects harbored no resistant strains of S. sanguis, about 60% of children who had received antibiotics harbored S. sanguis which were resistant to at least one of the tested antibiotics. Nearly half of these strains were resistant to two or more antibiotics. Resistance to penicillin and amoxicillin decreased with the age of the child and with the length of time since exposure to the antibiotic. However, resistance to trimethoprim-sulfamethoxazole or erythromycin showed no relationship to the age of the child or the length of time since exposure to the antibiotic. CONCLUSION: The data show that children who had been treated for otitis media with common antibiotic protocols do harbor antibiotic-resistant oral streptococci which may complicate prophylactic and therapeutic regimens for bacterial endocarditis.     

A comparative study of the effectiveness of metronidazole and penicillin V in eliminating anaerobes from postextraction bacteremias

Recent reports have indicated the serious nature of anaerobic endocarditis and septicemia. As anaerobes can be isolated from postextraction bacteremias, this study was undertaken to evaluate the effectiveness of metronidazole and penicillin V in eliminating anaerobes from postextraction bacteremias. Twenty-five patients were randomly assigned to each of three groups--a placebo group, a metronidazole group, and a penicillin V group--for a total of seventy-five patients. Although penicillin V reduced the occurrence of anaerobes to a greater degree than did metronidazole, it was noted that gram-negative anaerobes were still detected in the blood of four patients in the penicillin V group. In the metronidazole group no gram-negative anaerobes were cultured. Because of the marked effectiveness of metronidazole against gram-negative anaerobes, the use of penicillin V and metronidazole in combination might be effective in the prevention of the sequelae of postextraction bacteremias. However, further studies, using a larger sample size, to investigate specifically gram-negative anaerobes are required.     

Changes in the prevalence of subgingival enteric rods, staphylococci and yeasts after treatment with penicillin and erythromycin

The changes in the balance of microbial flora in the periodontium after antibiotic treatment were investigated in a blind study. The prevalence of gram-negative enteric rods, staphylococci and yeasts was followed before and during penicillin or erythromycin treatment of 72 periodontitis patients without periodontal cleaning. The prevalence of subgingival coagulase-positive staphylococci increased significantly following systemic penicillin therapy. After systemic erythromycin therapy, the prevalence of subgingival gram-negative enteric rods increased. Ten of 24 (42%) patients receiving systemic penicillin therapy developed clinical evidence of periodontal abscesses. In the absence of conventional mechanical cleaning, systemic administration of penicillin and erythromycin antibiotic to patients with preexisting periodontitis may lead to periodontal superinfection with opportunistic organisms.     

In vitro antimicrobial sensitivity of enteric rods and pseudomonads from advanced adult periodontitis

The prevalence and in vitro antimicrobial sensitivity of isolates of enteric rods and pseudomonads was examined in 844 adult periodontitis patients. These organisms were recovered from 13.5% of the study subjects. Ciprofloxacin exhibited the highest inhibitory activity of the 14 oral antimicrobial agents tested. Beta-lactam antibiotics were largely ineffective, and tetracycline failed to inhibit most Pseudomonas species. In vitro sensitivity data suggest that a subgingival microbiota comprising mainly streptococci would result from therapy that combined ciprofloxacin and metronidazole. Since streptococci may inhibit the growth of several putative periodontal pathogens, populations of "beneficial" streptococci in the periodontal pocket might constitute a very attractive therapeutic outcome. Controlled clinical studies are needed to clarify the possible role of ciprofloxacin in the treatment of destructive periodontitis.     

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).     

Effect of Periodontal Therapy With Amoxicillin–Metronidazole on Pharyngeal Carriage of Penicillin‐ and Erythromycin‐Resistant Viridans Streptococci

Background: Previous studies have focused on antibiotic resistance of Gram‐negative bacteria before and after periodontal therapy. The purpose of this analysis is to assess changes in resistance patterns of the commensal Gram‐positive microbiota. The viridans group streptococci (VGS) have been suggested to serve as reservoirs of resistance genes for more pathogenic streptococci and may be implicated in some non‐oral infections. Methods: In this randomized clinical trial, 80 patients with periodontitis are distributed randomly into two groups. In group A, patients received 375 mg amoxicillin and 500 mg metronidazole three times per day for 7 days during the non‐surgical treatment phase (T1). In group B, the antibiotics were administered during the surgical phase (T2). Resistance of VGS to penicillin and erythromycin was determined by the epsilometer test. Results: At baseline, VGS from 12.5% (group A) and 11.8% (group B) of patients had a minimum inhibitory concentration (MIC) >2 μg/mL to penicillin. Three months after T1, VGS from 15.6% and 16.7% of patients had an MIC >2 μg/mL, respectively. Six months after T2 VGS from 5.9% and 5.9% and 12 months after T2 VGS from 6.1% and 6.3% patients had an MIC >2 μg/mL. There was no effect of therapy with antibiotics, administered either in T1 or T2, on the carriage of penicillin‐resistant VGS. Erythromycin resistance was high at baseline and remained unchanged throughout the study. MICs for penicillin and erythromycin were correlated (P <0.05). Conclusion: Amoxicillin plus metronidazole did not significantly affect the resistance pattern of the VGS to penicillin or erythromycin.     

Antibiotic treatment of cervicofacial actinomycosis for patients allergic to penicillin: A clinical and in vitro study

The minimum inhibitory concentrations for erythromycin, clindamycin, lincomycin, tetracycline and minocycline have been determined for 92 clinical and three culture collection isolates of Actinomyces. From a consideration of MIC values and expected serum levels from oral therapy, minocycline was the drug of choice for the treatment of actinomycosis in patients allergic to penicillin. The serum levels of six patients allergic to penicillin, treated with oral minocycline I g/day were monitored and found to exceed the MIC for the Actinomyces species responsible for the condition. In all six Actinomycosis cases resolution was achieved in 8–16 weeks of oral minocycline therapy with no recrudescence for 1 year.     

Oral microbial colonization in children with sickle cell anaemia under long-term prophylaxis with penicillin

Background and objective

Sickle cell anaemia (SCA) is the most frequent haematological hereditary disease. Children with SCA are submitted to long-term prophylactic therapy with penicillin, but little is known about its impact on oral microflora. The aim of this study was to evaluate the oral microbial colonization of paediatric patients with SCA.

Design

Forty children (4–11 yrs old) with SCA (genotype SS) under long-term prophylactic treatment with penicillin were included in the study. Age/gender-matched control group of healthy children was also included. Scores of dmft/DMFT (number of decayed (D), missing (M), or filled (F) teeth; dmft, for primary dentition; DMFT, for permanent dentition) were obtained and stimulated saliva was sampled. Salivary flow rate and buffering capacity were evaluated. Counts of microorganisms (mutans streptococci, lactobacilli and yeasts) were determined by plating method. Yeasts were identified by API 20C AUX and PCR.

Results

Mean dmft/DMFT values were similar in the studied groups (SCA 2.13/1.60 and control 2.38/1.3). Although no significant differences between cariogenic microorganism counts were observed, significantly higher yeasts oral levels were observed in SCA group. Controls showed lower salivary buffering capacity. Candida albicans was the most frequently isolated species in both groups. Candida famata, Candida parapsilosis and Candida tropicalis were also isolated from controls. Candida dubliniensis, Candida rugosa and Candida sphaerica were found only in SCA group.

Conclusions

Based on the results, it could be concluded that paediatric patients with SCA showed significantly higher oral level of yeasts. Uncommon fungal species were found in SCA group. Similar caries prevalence and counts of lactobacilli and streptococci in relation to controls were observed.     

Acute localized exanthematous pustulosis: a cutaneous drug reaction in a dental setting

BACKGROUND: Acute generalized exanthematous pustulosis is a severe cutaneous eruption caused most commonly by antibiotics. Rarely, a localized variant of this pustular reaction called "acute localized exanthematous pustulosis" has been described. CASE DESCRIPTION: A 29-year-old woman sought treatment at the authors' dermatology clinic for an outbreak of numerous superficial, nonfollicular pustules with an underlying erythematous base that was accompanied by subjective fever. The lesions appeared two days after the patient began taking amoxicillin prescribed for endocarditis prophylaxis before she underwent a dental cleaning. Cultures were negative for bacteria, and the eruption resolved within four days after the patient discontinued the drug therapy. CLINICAL IMPLICATIONS: Newly revised guidelines for antibiotic prophylaxis for endocarditis indicate that adverse reactions far outweigh the benefits in most cases. It is important that general dentists and oral surgeons recognize this rare pustular eruption, because antibiotics, particularly amoxicillin, are the primary inciting agents. In addition, health professionals should make clinical choices based on evidence, weigh the risks of any treatment plan against its benefits and practice caution when prescribing any drug.     

Beta-hemolytic streptococci in advanced periodontitis

The distribution of serotypes of beta-hemolytic streptococci was examined in 718 periodontitis patients. Subgingival samples were obtained with paper points from the 3 deepest lesions in each patient, transported in VMGA III, plated onto brucella agar with 5% sheep blood and incubated anaerobically for 7 days. Serotyping and speciation were performed with Meritec^TM-Strep Beta-Hemolytic Streptococcus Grouping Set and the Analytab 20S^TM Streptococcus System. Beta-hemolytic streptococci were recovered from 33.7% of patients and averaged 10.5% of the total viable counts in culture-positive subjects. The organisms occurred with higher prevalence in patients 35 years or older than in younger patients. The predominant serotypes were F (62.9%), non-typeable (18.1%), B (6.9%), C (6.9%) and G (5.2%). 100% of beta-hemolytic streptococci were sensitive to penicillin, but less than 5% were sensitive to tetracycline, metronidazole or ciprofloxacin. Beta-hemolytic streptococci may contribute to inflammatory periodontal disease and may interfere with healing after therapy.     

Bacteriologic features and antimicrobial susceptibility in isolates from orofacial odontogenic infections

OBJECTIVE: The aim of this study was to obtain information for an effective antimicrobial therapy against orofacial odontogenic infections; such information was obtained from recent bacteriologic features and antimicrobial susceptibility data. STUDY DESIGN: The bacteriology and antimicrobial susceptibility of major pathogens in 163 patients with orofacial odontogenic infections to 7 antibiotics was examined. RESULTS: Mixed infection of strict anaerobes with facultative anaerobes (especially viridans streptococci) was observed most often in dentoalveolar infections, periodontitis, and pericoronitis. Penicillin (penicillin G) was effective against almost all pathogens, although it did not work well against beta-lactamase-positive Prevotella. Cefmetazole was effective against all test pathogens. Erythromycin was ineffective against viridans streptococci and most Fusobacterium. Clindamycin exerted a strong antimicrobial activity on anaerobes. Minocycline was effective against almost all the test pathogens. The antimicrobial activity of levofloxacin against viridans streptococci was not strong. CONCLUSIONS: An antibiotic that carries out antimicrobial activity against both viridans streptococci and oral anaerobes should be suitable for treatment of dentoalveolar infection, periodontitis, and pericoronitis. Penicillin remains effective as an antimicrobial against most major pathogens in orofacial odontogenic infections. Cefmetazole, clindamycin, and minocycline may be effective against most pathogens, including penicillin-unsusceptible bacteria.     

Antibiotic prophylaxis in a patient with penicillin allergy and recurrent bacterial endocarditis: A case report

Bacterial endocarditis (BE) is a rare and life-threatening heart infection that can be caused by oral microorganisms. Patients with specific cardiac valvular abnormalities as well as those with a history of recurrent episodes of endocarditis are considered to be at high-risk for developing BE. Antibiotic prophylaxis is recommended for high-risk individuals when bleeding is anticipated during dental procedures. Penicillins are the antibiotics of choice in preventing endocarditis, while other medications are indicated for patients with penicillin allergies. This case presentation outlines antibiotic prophylaxis prior to restorative care for a 44-year-old man who had a prosthetic heart valve, history of recurrent infective endocarditis and penicillin allergy. Intravenously administered van-comycin and gentamicin were prescribed due to the patients' level of risk and bleeding propensity. This article was written to raise the awareness of dental practitioners to the antibiotic prophylaxis options available for the treatment of patients with cardiac and associated systemic conditions.     

Penicillin-resistant bacteroides melaninogenicus infection of the mandible

Oral infections caused by gram-negative anaerobes are now recognized more frequently than in the past because of improved culturing techniques. A case of B melaninogenicus infection secondary to a fractured mandible, in which the organisms were both clinically resistant and insensitive on culture to penicillin, is presented. The organism was also shown to produce beta-lactamase. Clindamycin is appropriate dosage resulted in diarrhea, which precluded its continuation. Erythromycin therapy was curative in this case. In all cases in which the clinical course does not reflect the expected reasonable response to the appropriate antibiotic therapy, bacterial resistance to a drug should be considered, and laboratory testing for resistance and sensitivities should be performed.