E-test: a new technique for antimicrobial susceptibility testing for periodontal microorganisms

Carbapenemase producing Gram negative bacteria: Review of resistance and detection methods

Gram negative bacilli that are carbapenem resistant have emerged and are spreading worldwide. Infections caused by carbapenem resistant isolates posses a significant threat due to their high morbidity and mortality rates. Carbapenemases production by multi-drug resistant pathogens severely restricts treatment choices for illnesses caused by bacteria that are resistant to both carbapenems and majority of β-lactam antibiotics. Various phenotypic and genotypic methods for identification can distinguish between different classes of carbapenemase and identify pathogens that are resistant to carbapenems. The establishment of a quick, accurate and reliable test for identifying the clinical strains that produce the carbapenemase enzyme is essential for optimum diagnosis of microbial pathogens and management of the global rise in the prevalence of carbapenemase producing bacterial strains. The aim of this review was to summarize the mechanisms of carbapenem resistance and to provide an overview of different carbapenemase detection methods for carbapenem resistant Gram negative bacilli.

Polydispersity-mediated high efficacy of an in-situ aqueous nanosuspension of PPEF.3HCl in methicillin resistant Staphylococcus aureus sepsis model

Recently, World Health Organization declared antimicrobial resistance as the third greatest threat to human health. Absence of known cross-resistance, new class, new target, and a new mode of action are few major strategies being undertaken by researches to combat multidrug resistant pathogen. PPEF.3HCl, a bisbenzimidazole was developed as highly potent antibacterial agent against ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) pathogens, targeting topoisomerase IA. The present work encompasses a radical on-site generation of In-situ nanosuspension of PPEF.3HCl with enhanced efficacy against methicillin resistant S. aureus in septicemia model. We have generated instantaneously a PPEF.3HCl nanosuspension (IsPPEF.3HCl-NS) by mixing optimized monophasic PPEF.3HCl preconcentrate in propylene glycol into an aqueous medium comprising tween 80 as stabilizer. The IsPPEF.3HCl-NS showed precipitation efficiency of > 90 %, average particle size < 500 nm, retained upto 5 h, a negative zeta potential and bi/trimodal particle size distribution. Differential scanning calorimetry, X-ray diffraction confirmed partial amorphization and transmission electron microscopy revealed spherical particles. IsPPEF.3HCl-NS was non-hemolytic and exhibited good stability in serum. More significantly, it exhibited a ∼ 1.6-fold increase in macrophage uptake compared to free PPEF.3HCl in the RAW 264.7 macrophage cell line. Confocal microscopy revealed accumulation of IsPPEF.3HCl-NS within the lysosomal compartment and cell cytosol, proposing high efficacy. In terms of antimicrobial efficacy, IsPPEF.3HCl-NS outperforms free PPEF.3HCl against clinical methicillin sensitive and resistant S. aureus strains. In a pivotal experiment, IsPPEF.3HCl-NS exhibited over 83 % survival at 8 mg/kg.bw and an impressive reduction of ∼ 4-5 log-fold in bacterial load, primarily in the kidney, liver and spleen of septicemia mice. IsPPEF.3HCl-NS prepared by the In-situ approach, coupled with enhanced intramacrophage delivery and superior efficacy, positions IsPPEF.3HCl-NS as a pioneering and highly promising formulation in the battle against antimicrobial resistance.

Unraveling topoisomerase IA gate dynamics in presence of PPEF and its preclinical evaluation against multidrug-resistant pathogens

Type IA topoisomerases maintain DNA topology by cleaving ssDNA and relaxing negative supercoils. The inhibition of its activity in bacteria prevents the relaxation of negative supercoils, which in turn impedes DNA metabolic processes leading to cell death. Using this hypothesis, two bisbenzimidazoles, PPEF and BPVF are synthesized, selectively inhibiting bacterial TopoIA and TopoIII. PPEF stabilizes the topoisomerase and topoisomerase-ssDNA complex, acts as an interfacial inhibitor. PPEF display high efficacy against ~455 multi-drug resistant gram positive and negative bacteria. To understand molecular mechanism of inhibition of TopoIA and PPEF, accelerated MD simulation is carried out, and results suggested that PPEF binds, stabilizes the closed conformation of TopoIA with -6Kcal/mol binding energy and destabilizes the binding of ssDNA. The TopoIA gate dynamics model can be used as a tool to screen TopoIA inhibitors as therapeutic candidates. PPEF and BPVF cause cellular filamentation and DNA fragmentation leading to bacterial cell death. PPEF and BPVF show potent efficacy against systemic and neutropenic mouse models harboring E. coli, VRSA, and MRSA infection without cellular toxicity.

Comparison of Disc Diffusion, Etest, and a Modified CLSI Broth Microdilution Method for In Vitro Susceptibility Testing of Itraconazole, Posaconazole, and Voriconazole against Madurella mycetomatis

For many fungal infections, in vitro susceptibility testing is used to predict if an isolate is resistant or susceptible to the antifungal agent used to treat the infection. For Madurella mycetomatis, the main causative agent of mycetoma, in vitro susceptibility testing currently is not performed on a routine basis. The current in vitro susceptibility testing method is labor-intensive, and sonication must be done to generate a hyphal inoculum. For endpoint visualization, expensive viability dyes are needed. Here, we investigated if the currently used in vitro susceptibility method could be adapted to make it amendable for use in a routine setting which can be used in low-income countries, where mycetoma is endemic. First, we developed a methodology in which hyphal fragments can be generated without the need for sonication, by comparing different bead beating methodologies. Next, in vitro susceptibility was assessed using standard broth microdilution assays as well as disc diffusion, Etest, and VIPcheck methodologies. We demonstrate that after a hyphal suspension is generated by glass bead beating, disc diffusion, Etest, and VIPcheck can be used to determine susceptibility of Madurella mycetomatis to itraconazole, posaconazole, and voriconazole. The MICs found with Etest were comparable to those obtained with our modified CLSI-based broth microdilution in vitro susceptibility assay for itraconazole and posaconazole. Furthermore, we found an inverse relationship between the zones of inhibition and MICs obtained with the Etest and those obtained by the modified CLSI broth microdilution technique.

Role of Synonymous Mutations in the Evolution of TEM β-Lactamase Genes

Nonsynonymous mutations are well documented in TEM β-lactamases. The resulting amino acid changes often alter the conferred phenotype from broad spectrum (2b) conferred by TEM-1 to extended spectrum (2be), inhibitor resistant (2br), or both extended spectrum and inhibitor resistant (2ber). The encoding bla _TEM genes also deviate in numerous synonymous mutations, which are not well understood. bla _TEM-3 (2be), bla _TEM-33 (2br), and bla _TEM-109 (2ber) were studied in comparison to bla _TEM-1 bla _TEM-33 was chosen for more detailed studies because it deviates from bla _TEM-1 by a single nonsynonymous mutation and three additional synonymous mutations. Genes encoding the enzymes with only nonsynonymous or all (including synonymous) mutations plus all permutations between bla _TEM-1 and bla _TEM-33 were expressed in Escherichia coli cells. In disc diffusion assays, genes encoding TEM-3, TEM-33, and TEM-109 with all synonymous mutations resulted in higher resistance levels than genes without synonymous mutations. Disc diffusion assays with the 16 genes carrying all possible nucleotide change combinations between bla _TEM-1 and bla _TEM-33 indicated different susceptibilities for different variants. Nucleotide BLAST searches did not identify genes without synonymous mutations but did identify some without nonsynonymous mutations. Energies of possible secondary mRNA structures calculated with mfold are generally higher with synonymous mutations, suggesting that their role could be to destabilize the mRNA and facilitate its unfolding for efficient translation. In summary, our data indicate that transition from bla _TEM-1 to other variant genes by simply acquiring the nonsynonymous mutations is not favored. Instead, synonymous mutations seem to support the transition to other variant genes with nonsynonymous mutations leading to different phenotypes.

Antimicrobial Resistance Gene Detection Methods for Bacteria in Animal-Based Foods: A Brief Review of Highlights and Advantages

Antimicrobial resistance is a major public health problem and is mainly due to the indiscriminate use of antimicrobials in human and veterinary medicine. The consumption of animal-based foods can contribute to the transfer of these genes between animal and human bacteria. Resistant and multi-resistant bacteria such as Salmonella spp. and Campylobacter spp. have been detected both in animal-based foods and in production environments such as farms, industries and slaughterhouses. This review aims to compile the techniques for detecting antimicrobial resistance using traditional and molecular methods, highlighting their advantages and disadvantages as well as the effectiveness and confidence of their results.

Sensitivity Pattern Of Salmonella typhi And Paratyphi A Isolates To Chloramphenicol And Other Anti-Typhoid Drugs: An In Vitro Study

Purpose

To investigate the antimicrobial sensitivity pattern of commonly prescribed antimicrobials (chloramphenicol, cefixime, ofloxacin, azithromycin, and ceftriaxone) against Salmonella enterica isolates.

Methods

Blood culture positive isolates of S. typhi and S. paratyphi A (N = 251) received at Metropolis Healthcare Limited (Mumbai, India) from four zones of India (North, South, West, and East) between April and August 2018 were tested for antimicrobial susceptibility by E-test method. Based on the minimum inhibitory concentration (MIC), the organism was categorized as sensitive, intermediate, and resistant against the respective antibiotics as per Clinical and Laboratory Standards Institute criteria 2018.

Results

Out of 251 Salmonella isolates, 192 (76.5%) were S. typhi and 59 (23.5%) were S. paratyphi A. All 251 (100%) Salmonella isolates were sensitive to cefixime, ceftriaxone, and azithromycin; 237/251 (94.4%) isolates to chloramphenicol and only 9/251 (3.6%) isolates were sensitive to ofloxacin. Based on average MIC and MIC breakpoints, Salmonella isolates were found to be sensitive to chloramphenicol (MIC: 3.89±6.94 µg/mL), cefixime (MIC: 0.13±0.11 µg/mL), azithromycin (MIC: 3.32±2.19 µg/mL), and ceftriaxone (MIC: 0.11±0.18 µg/mL) and resistant to ofloxacin (MIC: 2.95±6.06 µg/mL). More than 20% of Salmonella isolates had MICs of chloramphenicol as 1.5 µg/mL (27.85% isolates) and 2 µg/mL (29.53% isolates).

Conclusion

Our study confirms the re‑emergence of susceptibility of Salmonella isolates to chloramphenicol. Further, the concern about fluoroquinolone-decreased susceptibility as indicated by the intermediate susceptibility or resistance was reiterated in this study. Though cefixime, azithromycin, and ceftriaxone showed susceptibility, the possibility of antibiotic resistance with the irrational use of these antibiotics cannot be deterred. This study thus emphasizes the need for continuous evaluation and judicious use of antimicrobials, considering the ever-changing landscape.

The First Identification and Antibiogram of Clostridium perfringens Type C Isolated from Soil and The Feces of Dead Foals in South Korea

Clostridium (C.) perfringens was isolated from 25 (11.1%) of 225 sampled horses and from 16 (35.56%) of 45 farms. All of the samples were negative for cpe, etx, itx, NetF genes and cpa gene were detected in 100% (25 of 25) of the samples that were positive for C. perfringens. cpb and cpb2 were detected in 40.0% (10 of 25) and 60.0% (15 of 25) of the samples that were positive for C. perfringens, respectively. Of the 25 C. perfringens isolates, 15 (60%) were type A and 10 (40%) were type C. Type C was observed on all the farms where the foals' deaths occurred. None of the isolates were positive for type B, type D, or type E. The MIC Evaluator strips antimicrobial susceptibility test showed meropenem (96%), ampicillin (92%), amoxicillin/clavulanic acid (84%), and tetracycline (8%) sensitivity.

Ultrasound-activated microbubbles as a novel intracellular drug delivery system for urinary tract infection

The development of new modalities for high-efficiency intracellular drug delivery is a priority for a number of disease areas. One such area is urinary tract infection (UTI), which is one of the most common infectious diseases globally and which imposes an immense economic and healthcare burden. Common uropathogenic bacteria have been shown to invade the urothelial wall during acute UTI, forming latent intracellular reservoirs that can evade antimicrobials and the immune response. This behaviour likely facilitates the high recurrence rates after oral antibiotic treatments, which are not able to penetrate the bladder wall and accumulate to an effective concentration. Meanwhile, oral antibiotics may also exacerbate antimicrobial resistance and cause systemic side effects. Using a human urothelial organoid model, we tested the ability of novel ultrasound-activated lipid microbubbles to deliver drugs into the cytoplasm of apical cells. The gas-filled lipid microbubbles were decorated with liposomes containing the non-cell-permeant antibiotic gentamicin and a fluorescent marker. The microbubble suspension was added to buffer at the apical surface of the bladder model before being exposed to ultrasound (1.1 MHz, 2.5 Mpa, 5500 cycles at 20 ms pulse duration) for 20 s. Our results show that ultrasound-activated intracellular delivery using microbubbles was over 16 times greater than the control group and twice that achieved by liposomes that were not associated with microbubbles. Moreover, no cell damage was detected. Together, our data show that ultrasound-activated microbubbles can safely deliver high concentrations of drugs into urothelial cells, and have the potential to be a more efficacious alternative to traditional oral antibiotic regimes for UTI. This modality of intracellular drug delivery may prove useful in other clinical indications, such as cancer and gene therapy, where such penetration would aid in treatment.

Efficiency of Biosynthesized Silver and Zinc Nanoparticles Against Multi-Drug Resistant Pathogens

Biosynthesis of metallic nanoparticles has acquired particular attention due to its economic feasibility, low toxicity, and simplicity of the process. In this study, extracellular synthesis of silver and zinc nanoparticle was carried out by Pseudomonas hibiscicola isolated from the effluent of an electroplating industry in Mumbai. Characterization studies revealed synthesis of 40 and 60 nm nanoparticles of silver (AgNP) and zinc (ZnNP), respectively, with distinct morphology as observed in TEM and its crystalline nature confirmed by XRD. DLS, zeta potential, NTA, and FTIR studies further characterized nanoparticles giving data about its size, stability, and functional groups. Considering the toxicity of nanoparticles the evaluation of antimicrobial activity was studied in the range of non-toxic concentration for normal cell lines. Silver nanoparticles were found to be the most effective antimicrobial against all tested strains and drug-resistant clinical isolates of MRSA, VRE, ESBL, MDR, Pseudomonas aeruginosa with MIC in the range of 1.25–5 mg/ml. Zinc nanoparticles were found to be specifically active against Gram-positive bacteria like Staphylococcus aureus including its drug-resistant variant MRSA. Both AgNP and ZnNP were found to be effective against Mycobacterium tuberculosis and its MDR strain with MIC of 1.25 mg/ml. The synergistic action of nanoparticles assessed in combination with a common antibiotic gentamicin (590 μg/mg) used for the treatment of various bacterial infections by Checker board assay. Silver nanoparticles profoundly exhibited synergistic antimicrobial activity against drug-resistant strains of MRSA, ESBL, VRE, and MDR P. aeruginosa while ZnNP were found to give synergism with gentamicin only against MRSA. The MRSA, ESBL, and P. aeruginosa strains exhibited MIC of 2.5 mg/ml except VRE which was 10 mg/ml for both AgNPs and ZnNPs. These results prove the great antimicrobial potential of AgNP and ZnNP against drug-resistant strains of community and hospital-acquired infections and opens a new arena of antimicrobials for treatment, supplementary prophylaxis, and prevention therapy.

Population Pharmacokinetic Study of Amoxicillin-Treated Burn Patients Hospitalized at a Swiss Tertiary-Care Center

The objective of this study was to investigate the population pharmacokinetics (PK) of amoxicillin in ICU burn patients and the optimal dosage regimens. This was a prospective study involving 21 consecutive burn patients receiving amoxicillin. PK data were analyzed using nonlinear mixed-effects modeling. Monte-Carlo simulations assessed the influence of various amoxicillin dosage regimens with identified covariates on the probability to achieve a target (PTA) value of time during which free amoxicillin concentrations in plasma exceeded the MIC (fT>MIC). A two-compartment model best described the data. Creatinine clearance (CL_CR) and body weight (BW) influenced amoxicillin CL and central volume of distribution (V₁), respectively. The median CL_CR (Cockcroft-Gault formula) was high (128 ml/min), with 25% of patients having CL_CRs of >150 ml/min. The CL, V₁, and half-life (t_1/2) values at steady state for a patient with a CL_CR of 110 ml/min and BW of 70 kg were 13.6 liters/h, 9.7 liters, and 0.8 h, respectively. Simulations showed that a target fT>MIC of ≥50% was achieved (PTA > 90%) with standard amoxicillin dosage regimens (1 to 2 g every 6 to 8 h [q6-8h]) when the MIC was low (<1 mg/liter). However, increased dosages of up to 2 g/4 h were necessary in patients with augmented CL_Rs or higher MICs. Prolonging amoxicillin infusion from 30 min to 2 h had a favorable effect on target attainment. In conclusion, this population analysis shows an increased amoxicillin CL and substantial CL PK variability in burn patients compared to literature data with nonburn patients. Situations of augmented CL_CR and/or high bacterial MIC target values may require dosage increases and longer infusion durations. (This study has been registered at ClinicalTrials.gov under identifier NCT01965340.).

Repositioning of 8-hydroxyquinoline derivatives as a new promising candidate for combating multidrug resistant Neisseria gonorrhoeae

The multidrug resistance of Neisseria gonorrhoeae becomes a public health problem worldwide, especially the strain H041 that showed the decrease susceptibility to ceftriaxone which is the last resort for gonorrhea treatment. Therefore, the simultaneous discovery and development of a new compound to fight this pathogen is urgently required. In this study, 8-hydroxyquinoline (8HQ) and derivatives were evaluated for their antimicrobial activities against the gonococcal pathogen using spectinomycin as the reference drug. The results showed that 8HQ derivatives gave an excellent antimicrobial potency. Particularly, the dihalogenated 8HQ (iodoquinol, clioquinol and 5,7-diCl-8HQ) exerted the high activity with MIC range of 0.08-0.15 μM, 0.10-0.20 μM and 0.28-0.56 µM, respectively, compared with the reference drug (MIC = 16 μg/mL or 48.14 μM). Moreover, these compounds were also shown to be non-cytotoxic/very high safety index. The findings reveal that these three compounds could be further developed as a new antimicrobial agent for fighting the gonorrheal disease.

Antimicrobial susceptibilities of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis strains from periodontitis patients in Morocco

BACKGROUND AND OBJECTIVE

Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis have been frequently isolated in periodontitis patients in Morocco. Its persistence after the subgingival debridement of the biofilm has been correlated with worse clinical outcomes. The aim of this study was to evaluate the antimicrobial susceptibilities of A. actinomycetemcomitans and P. gingivalis, to amoxicillin, amoxicillin plus clavulanate, metronidazole, and azithromycin. In addition, microbiological profiles of patients harbouring A. actinomycetemcomitans, P. gingivalis, or both were compared.

MATERIAL AND METHODS

In 45 consecutive periodontitis Moroccan patients, subgingival samples were taken and processed by culture. Twenty-four A. actinomycetemcomitans and 30 P. gingivalis colonies were isolated (54 strains) and susceptibility tests, using the epsilometric method, were run for amoxicillin, amoxicillin plus clavulanate, metronidazole, and azithromycin. Minimum inhibitory concentrations for 50 (MIC50) and 90% (MIC90) of the organisms were calculated.

RESULTS

The prevalence of A. actinomycetemcomitans and P. gingivalis was 79.5 and 84.4%, respectively. A. actinomycetemcomitans showed susceptibility to amoxicillin, amoxicillin plus clavulanate, while 28% of the isolated strains were resistant to azithromycin and 61.7% towards metronidazole. No P. gingivalis resistance towards amoxicillin, amoxicillin plus clavulanate, metronidazole, and azithromycin was found.

CONCLUSION

A. actinomycetemcomitans and P. gingivalis were frequently detected in Moroccan patients with periodontitis, while antimicrobial resistance was only detected for A. actinomycetemcomitans to metronidazole and azithromycin.

CLINICAL RELEVANCE

A. actinomycetemcomitans resistance against some antimicrobials in periodontitis patients in Morocco can influence the selection of the therapeutic approaches.

Antimicrobial profiles of Prevotella spp. and Fusobacterium nucleatum isolated from periodontal infections in a selected area of southern Italy

In view of the increasing antibiotic resistance of anaerobic Gram-negative bacteria, we determined the antimicrobial profile of 55 periodontal anaerobic Gram-negative bacteria correlated with human infections, comprising 16 strains of Fusobacterium nucleatum and 39 strains of Prevotella spp. isolated from periodontal pockets of 26 adults suffering from chronic periodontitis. All the strains of F. nucleatum were susceptible to amoxicillin/clavulanic acid, doxycycline, metronidazole, moxifloxacin and levofloxacin, whilst 2/16 strains were both resistant to amoxicillin and beta-lactamase-positive and 11/16 were resistant to clarithromycin. All of the Prevotella strains were susceptible to amoxicillin/clavulanic acid, doxycycline and metronidazole, whereas 7/39 strains were beta-lactamase-positive and resistant to amoxicillin, 5/39 were resistant to clarithromycin and 3/39 were resistant to both moxifloxacin and levofloxacin. Our findings confirm that there is an increasing need to encourage practitioners to use laboratory investigations to limit the risk of an incorrect therapeutic approach and to avoid the overuse of antimicrobial agents.

Susceptibility of Prevotella intermedia/Prevotella nigrescens (and Porphyromonas gingivalis) to propolis (bee glue) and other antimicrobial agents

Black-pigmented gram-negative anaerobes such as Porphyromonas gingivalis and Prevotella intermedia are suspected pathogens in adult periodontitis, whereas Prevotella nigrescens has been associated with health. Antimicrobial resistance among bacteria from this group has been reported in the past decade. This research aimed to evaluate and compare the susceptibility profile of 17 P. intermedia/P. nigrescens isolates recovered from patients with periodontitis and three reference strains to six antimicrobials, prescribed in dentistry in Brazil, and propolis (bee glue). The antimicrobial agents tested were tetracycline, penicillin, clindamycin, erythromycin, metronidazole, meropenem and six ethanolic extracts of propolis (EEPs) from Brazil. The reference strains P. gingivalis ATCC 33277 and P. intermedia ATCC 25611 were used for determination of minimum bactericidal concentration (MBC) and for time-kill assay to the EEPs. All of the strains were susceptible to penicillin, erythromycin, meropenem, metronidazole and 95% of them (n=19) to tetracycline. Thirty six percent (n=7) of the P. intermedia/P. nigrescens strains tested were resistant to clindamycin. As for propolis activity, all strains were susceptible and the minimum inhibitory concentration values ranged from 64 to 256 microg/mL. For the reference strains P. gingivalis ATCC 33277 and Prevotella intermedia ATCC 25611 the MBC was 256 microg/mL and death was observed within 3 h of incubation for P. gingivalis and within 6 h for P. intermedia. The action of propolis (bee glue) against suspected periodontal pathogens suggests that it may be of clinical value.

Antimicrobial treatment of Capnocytophaga infections

Capnocytophaga spp. are normal inhabitants of the oropharyngeal flora. They are also involved in periodontal diseases or animal bites, complicated by septicaemia with dissemination to a great variety of sites, both in immunocompetent and immunocompromised hosts. This review will focus on their pathogenesis, spectrum of clinical infections and susceptibility to disinfectants and antibiotics. The spread of beta-lactamase-producing strains limits the use of beta-lactams as first-line treatments, underlying the necessity to test the in vitro susceptibility of clinical strains. Many antimicrobial treatments have been used, despite an absence of randomised studies and guidelines regarding the duration of treatment according to infected sites. Imipenem/cilastatin, clindamycin or beta-lactamase inhibitor combinations are always effective and their use can be recommended in all infections.

Incidence and antimicrobial susceptibility of Porphyromonas gingivalis isolated from mixed endodontic infections

AIM

To investigate the prevalence of Porphyromonas gingivalis in root canals of infected teeth with periapical abscesses and to investigate the antimicrobial susceptibility of this species to some frequently prescribed antibiotics.

METHODOLOGY

Samples were obtained from 70 root canals of abscessed teeth. Microbial sampling, isolation and bacterial identification were accomplished using appropriate culture methods for anaerobic species. The antimicrobial susceptibility of the 20 strains of P. gingivalis isolated was determined by using the E-test. The antimicrobial agents tested were amoxicillin, amoxicillin + clavulanate, azythromycin, benzylpenicillin, cephaclor, clindamycin, erythromycin, metronidazole and tetracycline.

RESULTS

A total of 352 individual strains, belonging to 69 different species, were isolated. Eighty three percent of the strains were strict anaerobes and 47.5% of the isolated bacteria were Gram-negative. Porphyromonas gingivalis was found in 20 root canals and was most frequently found in symptomatic cases. Statistically, the presence of P. gingivalis was related to purulent exudates and pain on palpation (both P < 0.05). All P. gingivalis strains were sensitive to amoxicillin, amoxicillin + clavulanate, cephaclor, clindamycin, benzylpenicyllin, metronidazole and tetracycline. The lowest range of minimum inhibitory concentration (MIC) (0.026-0.125 microg mL(-1)) was observed against amoxicillin + clavulanate and clindamycin. The lowest MIC 90 was observed against clindamycin (0.064 microg mL(-1)). One strain was resistant to erythromycin and eight strains were resistant to azythromycin.

CONCLUSION

Porphyromonas gingivalis pathogen is isolated with frequency from root canals of infected teeth with periapical abscesses. Amoxicillin, as well as amoxicillin-clavulanic acid and benzylpenicillin were effective against P. gingivalis.

Antimicrobial profiles of periodontal pathogens isolated from periodontitis patients in the Netherlands and Spain

BACKGROUND AND AIM

Antimicrobial resistance of periodontal pathogens towards currently used antibiotics in periodontics has been investigated in a previous study. Microbial resistance in the periodontal microflora was more frequently observed in Spanish patients in comparison with Dutch patients. The aim of the present study was to compare antimicrobial susceptibility profiles of five periodontal bacteria isolated from periodontitis patients in Spain and in The Netherlands.

MATERIAL AND METHODS

Subgingival plaque samples from adult patients with periodontitis were collected and cultured on selective and non-selective plates. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum and Micromonas micros were isolated and used for minimal inhibitory concentration tests using the Epsilometer (E-test) technique. Eight different antibiotics were tested on all bacterial isolates. MIC50 and MIC90 values for each antibiotic and each species were determined and the percentage of resistant strains was calculated.

RESULTS

Significantly higher MIC values were noted in Spanish strains of F. nucleatum for penicillin, ciprofloxacin, of P. intermedia for penicillin, amoxicillin and tetracycline, of M. micros for tetracycline, amoxicillin and azithromycin, and of P. gingivalis for tetracycline and ciprofloxacin. Based on breakpoint concentrations, a higher number of resistant strains in Spain were found in F. nucleatum for penicillin, amoxicillin and metronidazole, in Prevotella intermedia for tetracycline and amoxicillin, and in A. actinomycetemcomitans for amoxicillin and azithromycin. Resistance of P. gingivalis strains was not observed for any of the antibiotics tested both in Spain and The Netherlands.

CONCLUSIONS

Differences exist in the susceptibility profiles of periodontal pathogens isolated from periodontitis patients in Spain and in The Netherlands. This implicates that antibiotic susceptibility testing is necessary to determine efficacy of antimicrobial agents. Also, clinical studies with antibiotics should take these differences into account. The information from the present study indicates that it may not be possible to develop uniform protocols for usage of antibiotics in the treatment of severe periodontitis in the European Union.

Microbiological analysis of infected root canals from symptomatic and asymptomatic teeth with periapical periodontitis and the antimicrobial susceptibility of some isolated anaerobic bacteria

The purpose of the present study was to investigate the correlation between the composition of the bacterial flora isolated from infected root canals of teeth with apical periodontitis with the presence of clinical signs and symptoms, and to test the antibiotic susceptibility of five anaerobic bacteria mostly commonly found in the root canals of symptomatic teeth against various substances using the E-test. Microbial samples were taken from 48 root canals, 29 symptomatic and 19 asymptomatic, using adequate techniques. A total of 218 cultivable isolates were recovered from 48 different microbial species and 19 different genera. Root canals from symptomatic teeth harbored more obligate anaerobes and a bigger number of bacterial species than the asymptomatic teeth. More than 70% of the bacterial isolates were strict anaerobes. Statistical analysis used a Pearson Chi-squared test or a one-sided Fisher's Exact test as appropriate. Suggested relationships were found between specific microorganisms, especially gram-negative anaerobes, and the presence of spontaneous or previous pain, tenderness to percussion, pain on palpation and swelling amoxicillin, amoxicillin + clavulanate and cephaclor were effective against all the strains tested. The lowest susceptibility rate was presented by Prevotella intermedia/nigrescens against Penicillin G. Our results suggested that specific bacteria are associated with endodontic symptoms of infected teeth with periapical periodontitis and the majority of the anaerobic bacterial species tested were susceptible to all antibiotics studied.

Change of antibiotic susceptibility following periodontal therapy. A pilot study in aggressive periodontal disease

BACKGROUND

The hypothesis was tested that bacterial susceptibilities in aggressive periodontitis change upon administration of systemic antibiotics as adjuncts to periodontal therapy.

METHODS

In 23 subjects (average age 38.9+/-6.7 years) with aggressive periodontitis, microbial parameters were assessed prior to and 1 year after completion of comprehensive mechanical/surgical and systemic antimicrobial therapy. Following identification of five selected pathogens with the Rapid ID 32 A system, their susceptibilities towards amoxicillin/clavulanate potassium, metronidazole, and tetracycline were examined with the E-test. Antibiotics were administered according to the test results, and the minimal inhibitory concentrations (MIC90) were reevaluated after 1 year. Statistical analysis was performed on a patient basis, with the site data used for evaluation of the MIC levels.

RESULTS

Bacterial MIC levels remained constant among the three antibiotic treatment groups compared with baseline. Mean MIC90 values ranged from <0.02 to 0.11 microg/ml (amoxicillin/clavulanate potassium), <0.02 to 0.27 microg/ml (metronidazole), and <0.02 to 0.11 microg/ml (tetracycline). Observed changes in susceptibility were attributed to the elimination of single bacterial taxa in the subgingival environment after antibiotic therapy. There were no statistically significant differences in clinical parameters among the treatment groups. Single tetracycline MICs were 1.5- to 6-fold enhanced compared to amoxicillin/clavulanate potassium and metronidazole.

CONCLUSION

The periodontal pathogens investigated prior to and 1 year after periodontal therapy are tested sensitive to the antimicrobial agents. In aggressive periodontitis, changes in bacterial susceptibility upon the administration of systemic antibiotics are associated with the limited number of isolates tested following therapy.

In vitro antimicrobial susceptibility of oral strains of Actinobacillus actinomycetemcomitans to seven antibiotics

BACKGROUND/AIMS

Periodontal infections with Actinobacillus actinomycetemcomitans seem to be refractory to conventional therapy. The aim of the present study was to test the in vitro susceptibilities of A. actinomycetemcomitans strains to a panel of seven orally administrable antibiotics.

METHODS

A total of 60 isolates of A. actinomycetemcomitans recovered from 43 individuals with gingivitis or periodontitis were tested. In addition, laboratory strains UP-6 and JP2 were analysed. The E-test was employed in order to determine minimal inhibitory concentrations (MIC) of antibiotics ampicillin/sulbactam, roxithromycin, azithromycin, doxycycline, metronidazole, ciprofloxacin, and moxifloxacin.

RESULTS

A. actinomycetemcomitans was highly susceptible to both fluoro-quinolones (MIC90 of 0.006 microgram/mL of ciprofloxacin and 0.032 microgram/mL of moxifloxacin). Good susceptibilities were found for ampicillin/sulbactam and doxycycline (MIC90 of 0.75 microgram/mL and 1 microgram/mL, respectively), and moderate susceptibilities for azithromycin (MIC90 of 3 microgram/mL). Most strains were resistant to metronidazole and roxithromycin. Cluster analysis revealed two larger clusters of A. actinomycetemcomitans strains with the smaller cluster assembling isolates with significantly higher MICs of most antibiotics.

CONCLUSIONS

Due to reported favourable pharmacokinetics, the fluoro-quinolone moxifloxacin appeared to be a promising candidate for adjunctive systemic antibiotic therapy in periodontal infections with A. actinomycetemcomitans.

Local metronidazole application in maintenance patients. Clinical and microbiological evaluation

The purpose of this investigation was to evaluate the clinical and microbiological effect of local antibiotic therapy in comparison with subgingival scaling and root planing in a randomized semi-masked study. Forty-six recall patients who completed systematic periodontal therapy 6 to 24 months prior to the study were enrolled. The inclusion requirements were at least one site with probing depth > or = 5 mm in each quadrant, no scaling, and no antibiotic therapy during the last 6 months. After randomization each patient received 2 different treatments: in 2 quadrants metronidazole 25% dental gel was applied subgingivally to the pockets at day 0 and day 7; scaling and root planing was carried out in the 2 other quadrants, one at day 0 and in the remaining quadrant at day 7. Subgingival microbiological samples were taken from each patient before treatment and on days 21, 91, and 175 after the treatment. The analyses were carried out by indirect immunofluorescence assay. At all treated sites probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP) were recorded on days 0, 21, 91, and 175. Both treatments resulted in PD reduction and CAL gain. PD reduction was statistically significant (P < 0.01) for both treatment modalities after 6 months. The CAL gain was not significant for either treatment. There was no statistical significance between scaling and antibiotic therapy. Treponema denticola, Porphyromonas gingivalis, and Prevotella intermedia were significantly reduced after therapy; however, there were no statistically significant differences between treatments. If Actinobacillus actinomycetemcomitans was present before therapy, it was also present after treatment in both groups. The conclusion is that, in recall patients, local application of metronidazole and scaling and root planing showed similar clinical and microbiological effects without statistically significant differences.

A beta-lactamase belonging to group 2e from oral clinical isolates of Prevotella intermedia

A beta-lactamase in oral clinical isolates of Prevotella intermedia that hydrolyzed cefuroxime and cephalothin with rates of 600 and 53.3 respectively, relative to that for cephaloridine (100), was characterized as a 2e-cephalosporinase. Inhibition was observed by clavulanic acid (IC50 0.72 microM), tazobactam (IC50 0.21 microM) and sulbactam (IC50 0.07 microM) and was not inhibited by cloxacillin, EDTA, NaCl or p-CMB. The pI and pH optima were 4.7 and 5.4, respectively.

Treatment of periodontal disease based on microbiological diagnosis. Relation between microbiological and clinical parameters during 5 years

The purpose of this study was to assess the clinical effect of treatment aimed to suppress Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis below detection level and Prevotella intermedia below 5% of the cultivable periodontal pocket flora. Sixteen patients and a total of 111 periodontal pockets with probing depth > or = 6 mm were included in the study. Twelve patients and a total of 77 sites completed the 5-year study. The results demonstrated clinical improvement of probing depth and gain of clinical attachment level of 3.4 mm and 1.2 mm, respectively. Treatment to eliminate indicator bacteria continued for 3 years before the aim was fulfilled. In order to eliminate A. actinomycetemcomitans from a majority of the sites, a combination of surgery and generalized tetracycline treatment was performed. A recolonization or regrowth of the indicator bacteria exceeding detection levels took place in several sites. The presence of A. actinomycetemcomitans. P. gingivalis, and P. intermedia, alone or in combination, correlated with attachment level change on the individual level. No such correlation was obtained by using presence of plaque, bleeding on probing, or three other bacteria (Campylobacter rectus, Eikenella corrodens, and Fusobacterium nucleatum) not used as treatment goal markers.