Human serum activity of telithromycin, azithromycin and amoxicillin/clavulanate against common aerobic and anaerobic respiratory pathogens

Telithromycin is a new ketolide antimicrobial with a good in vitro activity against both aerobic and anaerobic respiratory pathogens. In this study, we evaluated the antibacterial activity over time of telithromycin (800mg), azithromycin (500mg), and amoxicillin/clavulanate (875/125mg) in serum following single oral doses of these agents to 10 healthy subjects. Inhibitory and bactericidal titers were determined at 2, 6, 12, and 24h after each dose and the median titer was used to determine antibacterial activity. Against two azithromycin-resistant strains of Streptococcus pneumoniae, both telithromycin (MIC=0.25 and 0.5 microg/mL) and amoxicillin/clavulanate exhibited inhibitory and cidal activity for at least 6h. All three antibiotics provided prolonged (>or=12h) inhibitory activity against strains of Hemophilus influenzae (telithromycin MIC=4.0 microg/ml). Both telithromycin and amoxicillin/clavulanate exhibited rapid and prolonged inhibitory activity (>or=12h) against each of the anaerobes studied (Finegoldia [Peptostreptococcus] magna Peptostreptococcus micros, Prevotella bivia, and Prevotella melaninogenica). Moreover, both agents provided bactericidal activity against both Prevotella species. In this ex vivo pharmacodynamic study, we found that telithromycin provided rapid and prolonged antibacterial activity in serum against macrolide-resistant strains of S. pneumoniae, beta-lactamase-positive and -negative strains of H. influenzae, and common respiratory anaerobic pathogens. These findings suggest that telithromycin could have clinical utility in the treatment of community-acquired mixed aerobic-anaerobic respiratory tract infections, including chronic sinusitis and aspiration pneumonia.

Dual role of vitamin C in an oxygen-sensitive system: discrepancy between DNA damage and cell death

Although vitamin C is considered to act both as pro-oxidant and antioxidant, the mechanisms underlying these actions are still unclear. Using the oxygen-sensitive system of a strict anaerobe, Prevotella melaninogenica, we investigated both the pro-oxidant and antioxidant mechanisms of vitamin C. In the presence of vitamin C, the 8-hydroxydeoxyguanosine (8OHdG) formation induced by oxygen exposure was enhanced, probably due to the action of vitamin C on hydrogen peroxide generated during oxygen exposure: while catalase almost completely suppressed the enhancing effect of vitamin C, 8OHdG formation induced by hydrogen peroxide was enhanced by vitamin C. By contrast, the presence of vitamin C inhibited bacterial cell death, membrane damage, and lipid peroxidation induced by oxygen exposure. Sodium azide showed similar effects to vitamin C, thus the antioxidant action of vitamin C may be due to its quenching of the singlet oxygen generated in this system. Both the pro-oxidant and antioxidant effects of vitamin C were observed only in acidic conditions.

Sensitivity of genera Porphyromonas and Prevotella to the bactericidal action of C-terminal domain of human CAP18 and its analogues

This paper reports the effect of the synthesized 27-amino acid sequence in the C-terminal domain of human CAP18 (hCAP18), a human cationic antibacterial protein or cathelicidin, on certain strains belonging to the genera Porophyromonas and Prevotella. The domain binds lipopolysaccharides (LPS) from Porophyromonas gingivalis and Porophyromonas circumdentaria as well as enterobacterial LPS. Two analogues of hCAP18, designated LL/CAP18 and FF/CAP18, were also tested to determine whether additional activity was obtained. The analogue peptides replaced with hydrophobic and cationic amino acid residues showed more potent bactericidal and LPS-binding activities than the original one.

Beta-lactamase production in Prevotella and in vitro susceptibilities to selected beta-lactam antibiotics [corrected]

This study looked for beta-lactamase production in 100 Prevotella isolates. MICs were determined for amoxycillin, ticarcillin, amoxycillin+clavulanate, cephalothin, cefuroxime, cefixime, cefpodoxime and cefotaxime using the reference agar dilution method (standard M11 A4, NCCLS). Beta-lactamase activity was detected in 58 of the 100 isolates, 24 of 46 black-pigmented Provotella and 34 of 54 non-pigmented Prevotella. All beta-lactamase-negative strains were susceptible to all beta-lactam antibiotics with the exception of cefuroxime and cefixime. Overall, resistance rates of Prevotella strains were lower for ticarcillin (8%) and celefotaxime (12%) than for the other cephalosporins. All Prevotella isolates were susceptible to amoxycillin and were all inhibited by 2 mg/l or less amoxycillin [corrected].

Inhibitory effect of lactoperoxidase-generated hypothiocyanite upon black pigmented anaerobe growth

This study aimed to evaluate the in vitro effect of lactoperoxidase with or without its substrates (hydrogen peroxide, thiocyanate) on the growth of 4 different black pigmented anaerobe (BPA) strains associated with the development and progress of periodontal diseases: Porphyromonas gingivalis ATCC 33277, Prevotella intermedia NCTC 9336, Prevotella loescheii ATCC 15930, and Prevotella melaninogenica NCTC 9338. A 5-min lactoperoxidase-generated OSCN--HOSCN incubation at pH 6.0, 7.0 or 8.0 resulted in a decrease of the growth rate (tested by turbidimetry in liquid cultures) of the 4 BPA strains, whilst lactoperoxidase alone actually promoted bacterial growth.

[Study of bacteriology on local application of Tinidazole stilus in treatment for periodontitis]

OBJECTIVE

The study was designed to evaluate the antiseptic efficacy of Tinidazole stilus against periodontal pathogen.

METHODS

A total of 41 patients with periodontitis were included in this study. 26 of them were treated by Tindazole stilus and other 15 cases were treated by metronidazole stilus as controls. The prevalence of subgingival bacteria from both group were examined.

RESULTS

The eliminate rates for Black pigmented anaerobic rod (Porphyromonas gingivalis, Prevotella intermedius, Prevotella melaninogenicus), Fusobacteriums, Prevotella oris, Prevotella oralis, Eubacterium and Actinomyces were 95.8% 94.1%, 83.3% and 76.5%. The anti-bacterial efficiency of Tinidazole against periodontal pathogen was significantly higher than that of metronidazole (P < 0.05).

CONCLUSION

It appears to be effective to use Tinidazole stilus as local application against periodontal pathogens.

Mechanism of oxidative DNA damage induction in a strict anaerobe, Prevotella melaninogenica

We investigated the mechanism of the oxidative DNA damage induction by exposure to O(2) in Prevotella melaninogenica, a strict anaerobe. Flow cytometry with hydroethidine and dichlorofluorescein diacetate showed that O(2) exposure generated O(2)*-) and H(2)O(2). Results of electron spin resonance with alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone and ethanol showed that O(2) exposure also induced *OH radical generation in P. melaninogenica loaded with FeCl(2) but not in samples without FeCl(2) loading. In P. melaninogenica, O(2) exposure increased 8-hydroxydeoxyguanosine (8OHdG), typical of oxidative DNA damage. Catalase inhibited the increase, but the *OH radical scavengers did not. Phenanthroline, a membrane-permeable Fe and Cu chelator, increased the 8OHdG induction. In FeCl(2)-loaded samples, induction of 8OHdG decreased. Addition of H(2)O(2) markedly increased 8OHdG levels. These results indicate that in P. melaninogenica, exposure to O(2) generated and accumulated O(2)* and H(2)O(2), and that a crypto-OH radical generated through H(2)O(2) was the active species in the 8OHdG induction.

Induction of oxidative DNA damage in anaerobes

We compared oxidative DNA damage in strictly anaerobic Prevotella melaninogenica, aerotolerant anaerobic Bacteroides fragilis, and facultative anaerobic Salmonella typhimurium after exposure to O2 or H2O2. Using HPLC with electrochemical detection, we measured 8-hydroxydeoxyguanosine (8OHdG) as a damage marker. O2 induced 8OHdG in P. melaninogenica but not in B. fragilis, which shows catalase activity, or in S. typhimurium. In P. melaninogenica, with catalase, O2 induced less 8OHdG; superoxide dismutase had no effect; with glucose and glucose oxidase, O2 induced more 8OHdG. H2O2 also markedly increased 8OHdG. O2 was suggested to induce 8OHdG through H2O2. O2 or H2O2 decreased survival only in P. melaninogenica. Highly sensitive to oxidative stress, P. melaninogenica could prove useful for investigating oxidative DNA damage.

Time-kill study of the activity of trovafloxacin compared with ciprofloxacin, sparfloxacin, metronidazole, cefoxitin, piperacillin and piperacillin/tazobactam against six anaerobes

A time-kill method was developed to examine the killing kinetics of trovafloxacin, ciprofloxacin, sparfloxacin, metronidazole, cefoxitin, piperacillin and piperacillin/tazobactam against one strain each of Bacteroides fragilis, Bacteroides thetaiotaomicron, Prevotella melaninogenica, Fusobacterium mortiferum, Peptostreptococcus magnus and Clostridium perfringens. Solutions and suspensions were prepared inside an anaerobic glove box, using syringes and prereduced broth. Bottles were then incubated outside the chamber and viability counts determined after incubation for 0, 6, 24 and 48 h in a shaking water bath, avoiding introduction of air. Bacteriostatic/bactericidal concentrations (mg/L) after 48 h for the six strains were: trovafloxacin, 0.03-1/0.03-1; ciprofloxacin, 0.25-16/0.25-32; sparfloxacin, 0.06-2/0.06-8; metronidazole 1-64/1-64; cefoxitin, 0.125-16/0.125-32; piperacillin, 0.125-64/0.125-64; piperacillin/tazobactam, 0.06-2/0.125-8. Bacteriostatic levels were within two dilutions of broth MICs. By this time-kill method, trovafloxacin had the lowest bacteriostatic concentrations of all compounds tested.

[The effect of tinidazole in the treatment of adult periodontitis]

Fifty-two adult periodontitis patients were treated by the tablets of tinidazole (TNZ), and 23 patients treated by metronidazole (MNZ) served as control group. The effective rate of TNZ in adult periodontitis patients was 73.1%, which was significantly higher than that of the control group (43.5%). Antimicrobial studies showed that the capability of TNZ to kill the periodontal dominant anaerobic bacteria, especially B. gingivalis and B. melaninogenicus, was better than that of MNZ. The minimal inhibitory concentration (MIC) of TNZ to Bacteroides, Fusobacterium, Veillonella, Eubacterium, Antinomyces, Peotostreptococus and Anaerobic Streptococus was lower than that of MNZ and actylspiramycine.

Phototoxicity of argon laser irradiation on biofilms of Porphyromonas and Prevotella species

Species of Prevotella (Pr.) and Porphyromonas (Po.) and other microorganisms were cultivated as biofilms on agar medium and examined for their susceptibility to argon laser irradiation (continuous mode; wavelengths, 488-514 nm; fluences, 20-200 J cm(-2)). Fluences of 35 to 80 J cm(-2) inhibited biofilm growth in Po. endodontalis, Po. gingivalis, Pr. denticola, Pr. intermedia, Pr. melaninogenica and Pr. nigrescens. A fluence of 70 J cm(-2) did not affect biofilm growth in species of Bacillus, Candida, Enterobacter, Proteus, Pseudomonas, Staphylococcus and Streptococcus. The phototoxic effects of argon laser irradiation against Prevotella and Porphyromonas species were: (1) caused by the radiation alone; (2) modified by biofilm age; (3) dependent on the presence of atmospheric oxygen; (4) influenced by medium supplements of hemin, hemoglobin and blood; (5) greater when compared with other microbial species; (6) demonstrated without augmentation with an exogenous photosensitizer; and (7) apparently unrelated to the protoporphyrin content of the cells. Overall, these in vitro findings suggest that low doses of argon laser radiation may be effective in the treatment and/or prevention of clinical infections caused by biofilm-associated species of Prevotella or Porphyromonas.

[Study on local huangjiabang delivery device]

This article reports the pharmacological functions of local Huangjiabang delivery device which mainly includes medicinal herbs. The experimental study showed that Huangjiabang could inhibit the predominant cultivable organisms in periodontal disease significantly, and could also inhibit inflammatory swelling caused by xylene. Jiaochacaijiao, egg serum and filter-paper-granuloma significantly. The preliminary clinical observation showed that GI, PLI, SBI and PD were reduced remarkably in Huangjiabang administered pockets after two days and seven days of treatment. It is suggested that this new direct drug delivery system with medicinal herbs has wide prospect in the treatment of periodontal disease.

[Antimicrobial properties of Flos Lonicerae against oral pathogens]

The antimicrobial effect of Flos Lonicerae on oral pathogens was studied. The results showed that 73.9% of the tested pathogens were inhibited at a concentration below 6.25mg/ml. Streptococci mutants, actinomyces viscosus and bacteroides melaninogenicus were comparatively more sensitive to Flos Lonicerae.

Prevention of dry socket with clindamycin. A retrospective study

Clindamycin and other agents were compared for efficacy in preventing the entity "dry socket." A total 765 patients were treated with clindamycin, per os, and 408 patients were treated with other antibiotics or were non-treated controls. All patients underwent surgical removal of impacted mandibular third molars. The incidence of dry socket in untreated control and in non-clindamycin antibiotic-treated patients varied from 15 to 31 percent, while in those patients receiving clindamycin, the incidence was 0.65 percent. The results demonstrate a remarkable effectiveness of clindamycin in reducing the incidence of dry socket following surgical removal of impacted mandibular third molar.

The tet(Q) gene in bacteria isolated from patients with refractory periodontal disease

Twenty-two tetracycline-resistant (tetr) anaerobic and facultative anaerobic bacteria isolated from periodontal pockets of 12 patients with refractory periodontitis were examined for the presence of the Tet Q determinant by DNA-DNA hybridization. Dot blots of bacterial DNA were tested with an intragenic digoxigenin-labelled tet(Q) probe consisting of a 1.45 kb EcoRI/PvuII fragment from plasmid pNFD13-2. Southern blots of chromosomal DNA digested with the restriction enzyme EcoRI were also examined. The tet(Q) probe hybridized with DNA from 8 of the 22 tetr strains, including 2 Prevotella intermedia strains and one strain each of Prevotella nigrescens, Prevotella loescheii, Prevotella veroralis and Prevotella melaninogenica. The tetr strains of Mitsuokella dentalis and Capnocytophaga ochracea also hybridized with the probe. The lack of discernible plasmid DNA in all the probe-positive isolates suggests that these tetracycline-resistance genes were chromosomally encoded. The probe hybridized with a different size fragment in all the isolates. This study extends the number of species that carry the tet(Q) gene to include several outside the genera Prevotella and Bacteroides.

Cytotoxicity versus antibacterial activity of some antiseptics in vitro

Through the development of new techniques for bacterial growth and isolation, obligate anaerobes have been shown to be more prevalent than previously thought in the pathogenesis of periapical and pulpal diseases. A follow-up study was conducted to examine the germicidal effect of 0.05% NaOCl, 10 mg/ml metronidazole and supernatant of Ca (OH)2 (0.025 ml) on four anaerobic microorganisms commonly found in root canals, and to compare the toxicity of these substances on cell cultures. In vitro testing revealed that 0.05% NaOCl and Ca (OH)2 were both equally effective on these anaerobes. Also, metronidazole was found to be germicidally effective against Bacteroides melaninogenicus, Bacteroides oralis and Peptostreptococcus anaerobius, but ineffective against Veillonella alcalescens. Furthermore, it was found that NaOCl and Ca (OH)2 had a very destructive effect on cell cultures compared with their antimicrobial effect, whereas metronidazole was less toxic among the agents tested.

Antibacterial action of natural honey on anaerobic bacteroides

Two samples of natural Honey were tested for their antibacterial effect on Bacteroides, mainly the pathogenic black pigmented B. melaninogenicus isolated from ten cases of dental infections (dental abscesses and chronic osteomyelitis). These organisms were subjected to the effect of natural and diluted honey (50%), in broth and solid cultures. The results were compared with those of the same organisms incubated with saturated glucose solution, which showed less inhibition, indicating that the inhibitory effect of honey was not due to its high sugar content nor to its acidic PH, when using Schaedler's broth adjusted to the same PH as control. The local therapeutic value of natural honey was illustrated with an attempt to correlate between the microbial findings and the clinical implications.

Evaluation of antibiotic-supplemented bone allograft in a rabbit model

The use of an antibiotic-supplemented bone allograft (ASBA) as a material for placement in infected mandibular fractures was investigated in a rabbit model. In phase I of this project, fractures were created in the mandibles of 30 New Zealand white rabbits and injected with 5 x 10(6) colony-forming units of Staphylococcus aureus and Bacteroides melaninogenicus. The animals were divided into three treatment groups (A, B, or C) and treated with conventional treatment (CT), CT plus demineralized bone powder, or CT plus ASBA. In phase II, bone defects were created in the mandibles of 17 New Zealand white rabbits and then grafted with ASBA. Assessment of healing and vascular ingrowth was made at 2-day intervals through 3 weeks postoperatively, and then weekly until termination at 60 days postoperatively. Phase I results showed significantly enhanced healing in the ASBA-treated group when compared with the other treatment methods and healed fracture strength, which was comparable to the nonfractured, contralateral mandibular angle. Phase II results demonstrated vascular structures in the ASBA material by 4 days postoperatively and osteogenesis by 12 days postoperatively.

[Empirical antibiotic therapy of wounds complicated by anaerobic non-clostridial infection]

Antibacterial activity of 14 drugs against clinical strains of asporogenic anaerobes causing wound infections in the soft tissues i. e. Bacteroides fragilis and Bacteroides melaninogenicus as well as anaerobic gram-positive++ cocci was assayed with the method of serial dilutions in agar. It was shown that among the investigated species B. fragilis had the most marked resistance since out of the 14 drugs only 8 were sufficiently active against it i.e. carbenicillin, levomycetin, lincomycin, dioxidine, metronidazole, thinidazole, nitrazole and erythromycin. The choice of drugs for treating infections caused by B. melaninogenicus and anaerobic grampositive cocci unlike those caused by B. fragilis offered no difficulty since practically++ all the investigated drugs were highly active against the causative agents. There was observed relationship between the frequency of asporogenic anaerobes and the wound genesis. The characteristic features of the species composition connected with localization of the suppurative foci were indicated. The detected specific antimicrobial profiles of the asporogenic anaerobes causing wound infections and the peculiarity of their participation in development of purulent infections of the soft tissues provided a differential approach to empirical antibacterial therapy prior to the pathogen bacteriological investigation and availability of the antibioticograms.

Pathogenicity of capsulate and non-capsulate members of Bacteroides fragilis and B. melaninogenicus groups in mixed infection with Escherichia coli and Streptococcus pyogenes

The relationships between capsulate and non-capsulate Bacteroides fragilis strains and Escherichia coli, and between capsulate and non-capsulate strains of the B. melaninogenicus group and Streptococcus pyogenes, were studied in a subcutaneous abscess model in mice. Selective antimicrobial agents directed against either aerobic or anaerobic bacteria were used alone or in combination to explore the effect of eradication of one component of the mixed infection. Single agent therapy effective against both aerobic and anaerobic flora was also employed. Single therapy of mixed infection directed at the elimination of only one organism (S. pyogenes, E. coli or Bacteroides sp.) caused significant reductions in the numbers of sensitive organisms and also smaller yet significant decreases in the numbers of insensitive organisms. However, the abscesses were not eliminated after such therapy. Combination therapy or use of a single agent (cefoxitin) directed against the aerobic and anaerobic components of the infection was more effective. Non-capsulate Bacteroides spp. became capsulate after passage in mice mixed with either S. pyogenes or E. coli. Therapy directed at the elimination of S. pyogenes and E. coli did not prevent the emergence of capsulate Bacteroides spp. These data demonstrate the synergy between all members of the B. fragilis group and E. coli and between the B. melaninogenicus group and S. pyogenes, and reiterate the need to direct antimicrobial therapy at the eradication of the aerobic and anaerobic components of mixed infections.

Activities of Nigerian chewing stick extracts against Bacteroides gingivalis and Bacteroides melaninogenicus

The in vitro activities of extracts of Nigerian chewing sticks against Bacteroides gingivalis and B. melaninogenicus are presented. The greatest inhibitory action was produced by Serindeia werneckei, whereas Fagara zanthoxyloides produced no appreciable inhibitory effect. A generally good correlation was found between the killing curves and MICs. Only extracts of Anogeissus leiocarpus showed acute toxicity in mice.

The antibacterial effect of toothpastes on the salivary flora

Both past and presently available toothpastes contain potential antimicrobial agents which could have a beneficial effect in the prevention of plaque and gingivitis. If these preparations were to be effective clinically, some effect on salivary bacteria would also be expected. This cross-over study measured salivary bacterial counts and the presence or absence of residual antibacterial activity in saliva following tooth brushing with 7 commercially available toothpastes, and moreover, compared their effect with that produced by a chlorhexidine gel. Generally, all toothpaste products produced a reduction in aerobic, anaerobic and streptococcal counts with a hexetidine containing toothpaste producing the largest and longest lasting reduction. In contrast, an enzyme containing toothpaste and an amine fluoride toothpaste, had little effect on bacterial counts. The chlorhexidine gel produced the largest reduction in salivary counts, which was evident for at least 5 h following brushing. Residual antibacterial activity in saliva was only evident immediately following brushing with the hexetidine toothpaste, but for the chlorhexidine gel, was present up to 90 min following brushing. The findings of this study have illustrated the limited antibacterial activity of presently available toothpastes on the salivary flora compared to chlorhexidine, and as such, would tend to question the relative benefit of toothpaste in preventing periodontal disease through an antimicrobial effect.

Anaerobic infections in childhood

Bacteroides melaninogenicus and Bacteroides oralis are predominant anaerobes in orofacial infections and aspiration pneumonia. Fusobacterium species are common pathogens in aspiration pneumonia, brain abscesses and orofacial infections. Clostridium perfringens can cause bacteremia and wound infections. Clostridium botulinum can produce a paralytic toxin that causes a paralytic syndrome in infants. Clostridium difficile can cause diarrhea or antibiotic-associated colitis.

In vitro activity of ticarcillin plus clavulanic acid against bacteria isolated in three centers

Over 10,000 bacterial isolates were tested against ticarcillin alone or combined with clavulanic acid (2.0 micrograms/ml). Of 5,295 Enterobacteriaceae, 72% were susceptible to ticarcillin alone, whereas 91% were susceptible to the combination. Bacteroides fragilis and Bacteroides melaninogenicus isolates were more susceptible to the combination. The activity of ticarcillin against other microorganisms was not profoundly influenced.

In vivo protection of penicillin-susceptible Bacteroides melaninogenicus from penicillin by facultative bacteria which produce beta-lactamase

We investigated the possibility that beta-lactamase producing strains of Klebsiella pneumoniae and Staphylococcus aureus can protect organisms of the Bacteroides melaninogenicus group from penicillin. A mixed infection was induced in mice in the form of a subcutaneous abscess involving a penicillin-susceptible encapsulated B. melaninogenicus, and a beta-lactamase producing strain of either K. pneumoniae or S. aureus. The infected animals were treated for 7 days with single or combined antimicrobial therapy. The single agents used were penicillin, clavulanic acid, metronidazole, and gentamicin. The antimicrobial combinations were penicillin and clavulanic acid, penicillin and gentamicin, and metronidazole and gentamicin. Administration of a single agent was effective in treating abscesses caused by susceptible organisms. The only effective therapy for mixed infections was by combination therapy of penicillin and clavulanic acid or metronidazole and gentamicin. This study supports the hypothesis that beta-lactamase producing facultative bacteria may shield their anaerobic counterparts from penicillin therapy, thereby contributing to the persistence of the infection.

Synergism between penicillin, clindamycin, or metronidazole and gentamicin against species of the Bacteroides melaninogenicus and Bacteroides fragilis groups

Clinical isolates of the Bacteroides melaninogenicus and Bacteroides fragilis groups were tested for in vitro and in vivo susceptibility to penicillin, clindamycin, and metronidazole, used singly or in combination with gentamicin. The in vitro tests consisted of determinations of minimal inhibitory concentrations (MICs) carried out with or without constant amounts of gentamicin. When used alone, gentamicin had negligible effects on the bacteria but significantly reduced the MICs of penicillin, clindamycin, and metronidazole against 11, 10, and 3, of the 15 strains of the B. melaninogenicus group, respectively. The 15 strains of the B. fragilis group were all beta-lactamase producers and were highly resistant to penicillin or the combination of penicillin and gentamicin. However, gentamicin reduced the MICs of clindamycin and metronidazole against 1 and 7 strains of this group, respectively. The in vivo tests were carried out in mice and consisted of measurements of the effects of the antimicrobial agents on the sizes and bacterial content of abscesses induced by subcutaneous injection of bacterial suspensions. The results of the in vivo tests were generally consistent with those obtained in vitro with strains of the B. melaninogenicus group. Synergism between gentamicin and penicillin, clindamycin, or metronidazole was shown in 13, 10, and 3 strains of this group, respectively. In vivo synergism was not clearly demonstrated with the strains of the B. fragilis group, possibly because clindamycin and metronidazole used alone were highly efficacious. We suggest that the synergistic effect of gentamicin is due to its increased transport into the bacterial cell in the presence of penicillin and, possibly, other antimicrobial agents. The newly recognized in vitro and in vivo synergism between penicillin and other antimicrobial agents and an aminoglycoside in B. melaninogenicus may have clinical implications that deserve to be investigated.

Brain abscess due to penicillin- and clindamycin-resistant Bacteroides melaninogenicus

The case of a patient with severe anaerobic infection, a brain abscess, is presented. The causative organism was a penicillinase-producing, clindamycin-resistant strain of Bacteroides melaninogenicus. Treatment with adequate doses of penicillin G failed. Findings in this case suggest caution when basing therapy on the untested assumption that B. melaninogenicus is routinely susceptible to penicillin and clindamycin therapy.

Aerobic and anaerobic bacteriology of peritonsillar abscess in children

Aspiration of peritonsillar abscess (quinsy) was aseptically performed in 16 children. Patients' median age was 10 years (range 6 to 17 years), and 12 were males. Unilateral abscess was present in all but one child. All aspirates were cultured for aerobes and anaerobes and yielded bacterial growth in all patients. Anaerobes were isolated in all patients; in 3 patients (19%), they were the only organism isolated, and in 13 (81%), they were mixed with aerobes. There were 91 anaerobic isolates (5.7 per specimen): 42 Bacteroides sp. (including 23 B. melaninogenicus, 5 B. oralis and 4 B. ruminicola ss. brevis); 18 anaerobic Gram-positive cocci (including 10 Peptostreptococcus sp., 4 Peptococcus sp. and 4 microaerophilic streptococci); 15 Fusobacterium sp.; and 3 Clostridium sp. There were 32 aerobic isolates (2.0 per specimen): 11 gamma-hemolytic streptococci, 8 alpha-hemolytic streptococci, 4 Group A beta-hemolytic streptococci, 4 Haemophilus sp. and 3 S. aureus. Beta-lactamase production was noted in 13 isolates recovered from 11 patients (68%). These were all isolates of S. aureus (3), 8 of 23 B. melaninogenicus (35%), and 2 of 5 B. oralis (40%). Our findings indicate the major role of anaerobic organisms in the polymicrobial etiology of peritonsillar abscesses in children, and demonstrate the presence of many beta-lactamase-producing organisms in two thirds of the patients.

Characterization of volatile sulphur production by pathogenic and non-pathogenic strains of oral Bacteroides

Marked differences were observed in intermediate sulphur metabolism between non-pathogenic strains of Bacteroides melaninogenicus var melaninogenicus (CP-) and pathogenic Bacteroides melaninogenicus asaccharolyticus (CP+). The CP+ strains, which produced collagenase and protease and caused formation of abscesses when injected subcutaneously into groins of guinea pigs, produced copious amounts of volatile sulphur compounds (VSC) which consisted predominantly of CH3SH and (CH3S)2. Hydrogen sulphide occurred in considerably lesser amounts. CP+ cultures yielded 8-fold more total volatile S, 15-fold more CH3SH and 260-fold more (CH3S)2 during 24 h of incubation in trypticase-yeast extract medium. Whereas H2S accounted for 60 per cent of the total volatile S content of the head-space of CP- cultures, it represented only 8 per cent of the volatile S in CP + systems. Although the CP-organisms did not grow as well as CP +, the differences in concentration of VSC may be only partly related to the disparity in growth rates. When the VSC concentrations were calculated on the basis of equivalent optical density of 1.0, the CP + strains still produced over 3-fold more total volatile S, 6-fold more CH3SH and 100-fold more (CH3S)2. A similar allowance for growth rate suggests that CP-strains may possess a greater potential to produce H2S. Both groups metabolized S-containing amino acids and serine, resulting in appreciable increases in H2S production by CP-. However, the two groups appeared to metabolize the carbon moiety of cystine an cysteine by different pathways. The addition of glucose to the medium depressed total volatile S production by both CP+ and CP-strains, attributable mostly to lower H2S levels. Whereas the omission of yeast extract and charcoal treatment of trypticase did not adversely effect the activity of CP+, it further markedly reduced the capacity of CP-cultures to produce VSC. These results suggest that VSC analysis offers a convenient means of assessing strain differences and pathogenic potential of B. melaninogenicus.

Antimicrobial effect of fluorides on Bacteroides melaninogenicus subspecies and Bacteroides asaccharolyticus

This study was undertaken to determine whether the suspected periodontopathogens Bacteroides melaninogenicus ss melaninogenicus and intermedius and Bacteroides asaccharolyticus are killed by clinically used topical fluorides. The viability of each organism was examined after exposure to three fluoride compounds, stannous (SnF2), acidulated phosphate (APF), and neutral sodium (NaF), for 1 and 8 h. Stannous fluoride was found to be effective at lowest fluoride concentrations with APF next in effectiveness. NaF required the highest concentrations of fluoride to kill test organisms. Longer exposure times were found to be more effective at lower concentrations. Data obtained in this study with gram-negative organisms support and extend previous information regarding the antibacterial effect of fluorides against gram-positive periodontopathogens.

The effect of intensive antibacterial therapy on the sulcular environment in monkeys. Part I. Changes in the bacteriology of the gingival sulcus

The changes induced in the bacteriology of the gingival sulcus were evaluated as part of a study considering the keratinizing potential of the sulcular epithelium when bacterial plaque was essentially eliminated. Two Rhesus monkeys were scaled and placed on a daily therapeutic regimen which included a prophylaxis, systemic tetracycline, and topical chlorhexidine. Over the 40 day experimental period and 74 days post-therapy, subgingival plaque samples were taken periodically. The plaque samples were cultured anaerobically and aerobically to determine the predominant bacterial flora. The total cultivable bacterial flora decreased from initial levels by greater than 99.9% with the antibacterial therapy. The flora shifted with therapy from one dominated by anaerobic organisms, including Bacteroides melaninogenicus (18%) and Fusobacterium species (13.9%), to a flora dominated by organisms growing aerobically. During treatment B. melaninogenicus and Fusobacterium species were not detected in any sample. After cessation of all therapy the anaerobes increased to dominance again, but B. melaninogenicus remained undetectable through 74 days post-therapy.

Clinical and microbiological aspects of chemotherapeutic agents used according to the specific plaque hypothesis

Certain forms of dental decay and periodontal disease appear to be due to specific bacterial infections following overgrowth of certain indigenous plaque bacteria, i.e., the specific plaque hypothesis, If so, then antimicrobial treatment based on a diagnosis of elevated levels or proportions of these organisms should be considered. Such treatment cannot be administered according to concepts of the non-specific plaque hypothesis. A treatment philosophy is presented which is based upon considerations long established in medical infections following overgrowth of certain indigenous plaque bacteria, i.e., the specific plaque hypomicrobial to the site of the infection for periods long enough to suppress or destroy the pathogenic agent. Examples of this treatment philosophy are given.

Sphingolipid biosynthesis and vitamin K metabolism in Bacteroides melaninogenicus

B. melaninogenicus provides a unique system for the study of the biosynthesis of an important group of lipids, the phosphosphingolipids. Sphingolipid biosynthesis can be repressed and induced by depletion and restoration of vitamin K. At least one enzyme involved in sphingolipid biosynthesis from the microorganism can be solubilized and so purified by conventional methods. Pathways involved in biosynthesis may differ from hitherto postulated pathways, for example, the incorporation of NH4+ into ethanolamine residue of ceramide phosphorylethanolamine. Moreover, the derivation of mutants defective in steps in sphingolipid biosynthesis would be of great value in these studies.

Metronidazole in the prophylaxis and treatment of anaerobic infection

The influence of prophylactic metronidazole on vaginal carriage rates of anaerobes and the development of postoperative anaerobic infection was studied in 104 women who underwent abdominal hysterectomy. Metronidazole prophylaxis in 54 patients led to a decrease in the anaerobe vaginal carriage rate from 65% pre-operatively to 17% and 28% on the 3rd and 7th postoperative days respectively. In the control group (50 patients) no significant decrease in anaerobe yield was noted, corresponding percentages being 72%, 64%, and 74%. Postoperative infection occurred in 36 patients (28 controls; 8 on prophylactic metronidazole). Wound swabs from all 8 patients in the latter group yielded aerobes, and in 1 patient mixed infection (aerobes/anaerobes) occurred. In 7 of these patients (including the patient with mixed infection), the infection resolved spontaneously, while the 8th patient responded to therapy with metronidazole, kanamycin and ampicillin. In the control patients, 21 cases of postoperative wound infection and 4 of vault infection were seen; wound swabs from patients in the former group yielded aerobes in only 6 cases, and mixed growth of aerobes/anaerobes in 10 cases. Postoperative wound/vault infections in control patients cleared spontaneously in 18 cases and responded to imidazole therapy, with or without ampicillin and kanamycin, in 7 cases.

Penicillin resistance and penicillinase production in clinical isolates of Bacteroides melaninogenicus

The minimum inhibitory concentrations (MIC) of penicillin and six other antimicrobials were determined for 50 clinical isolates of Bacteroides melaninogenicus. Agar dilution susceptibilities were performed using supplemented brucella blood agar and the proposed National Committee for Clinical Laboratory Standards standard method for anaerobes; results with the two methods were comparable. A penicillin concentration >/=0.8 mug/ml was needed to inhibit 56% of the isolates, whereas 100% were susceptible to 0.1 mug of clindamycin per ml. All isolates with penicillin MIC values >/=0.8 mug/ml produced beta-lactamase using a slide method. A micro-iodometric assay was used to quantitate beta-lactamase production in six isolates. The beta-lactamase activity of B. melaninogenicus was comparable to that of a Staphylococcus aureus isolate but was not inducible, and the specific amount produced correlated only partially with penicillin MIC values. A clinical review of patients from whom the beta-lactamase-producing strains of B. melaninogenicus were isolated did not suggest any increased virulence in these strains or an unexpectedly poor clinical response to appropriate therapy.

Characterization of bacteroides melaninogenicus

Fifty-eight human isolates of Bacteroides melaninogenicus, 42 from a variety of clinical infections and the rest from normal flora, were studied for pigment production and ultraviolet light fluorescence and by forty biochemical and other tests, including end-product analysis by gas-liquid chromatography. In a number of instances, tests were repeated several times and the results were reproducible. Agar plate dilution susceptibility tests were also performed to 12 antimicrobial agents. These 58 strains could be reliably placed into three groups, corresponding to the three subspecies described, based on seven characteristics. These included acid production in peptone-yeast-glucose medium, production of n-butyric acid from peptone-yeast-glucose medium, esculin hydrolysis, starch hydrolysis, indole production, effect on milk, and lipase production. Production of hydrogen gas in peptone-yeast-fructose medium may be another distinguishing characteristic. In general there was not much difference in the susceptibility of the three groups to the various antimicrobial agents tested. Two strains had a minimal inhibitory concentration of penicillin G of 16 and 32 U/ml, respectively. Three strains did not produce a black pigment in spite of prolonged incubation on blood-containing media.

Should fiberoptic bronchoscopy aspirates be cultured?

The reliability of fiberoptic bronchoscopy as a method to study the bacteriology of the lower respiratory tract was tested. The procedure used was suction aspiration through the inner channel after topical anesthesia with lidocaine. To detect contamination by oropharyngeal bacteria, the aspirates were cultured in patients with no evidence of active infection, comparison was made with results of transtracheal aspiration cultures, and the aspirate was tested for the presence of an oral dye marker. Results with all 3 methods of analysis indicated contamination with oropharyngeal bacteria that were presumably introduced during instrumentation through the upper airways. An additional factor studied was the effect of topical anesthetics. Analysis of aspirates showed that as much as 96 per cent of the specimen was anesthetic solution. Lidocaine also proved toxic to lower respiratory tract pathogens, although there were significant differences between bacterial species. It was concluded that fiberoptic bronchoscopy as performed in this study does not reliably reflect the bacteriology of the lower respiratory tract.