Essential Oil from Psidium cattleianum Sabine (Myrtaceae) Fresh Leaves: Chemical Characterization and in vitro Antibacterial Activity Against Endodontic Pathogens

Abstract Endodontic infections result from oral pathogenic bacteria which reach and infect dental pulp, as well as surrounding tissues, through cracks, unrepaired caries and failed caries restorations. This study aims to determine the chemical composition of essential oil from Psidium cattleianum leaves (PC-EO) and to assess its antibacterial activity against endodontic bacteria. Antibacterial activity of PC-EO was evaluated in terms of its minimum inhibitory concentration (MIC) values by the broth microdilution method on 96-well microplates. Bacteria Porphyromonas gingivalis (MIC = 20 µg/mL), Prevotella nigrescens (MIC = 62.5 µg/mL), Fusobacterium nucleatum (MIC = 12.5 µg/mL), Actinomyces naeslundii (MIC = 50 µg/mL), Bacteroides fragilis (MIC = 12.5 µg/mL), Aggregatibacter actinomycetemcomitans (MIC = 6.25 µg/mL) and Peptostreptococcus anaerobius (MIC = 62.5 µg/mL) were evaluated and compared to chlorhexidine dihydrochloride (CDH), the positive control. PC-EO was obtained by hydrodistillation with the use of a Clevenger-type apparatus whereas its chemical composition was analyzed by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Viridiflorol (17.9%), β-caryophyllene (11.8%), 1,8-cineole (10.8%) and β-selinene (8.6%) were the major constituents found in PC-EO, which exhibited high antibacterial activity against all endodontic pathogens under investigation. Therefore, PC-EO, a promising source of bioactive compounds, may provide therapeutic solutions for the field of endodontics.

Inactivation of MarR gene homologs increases susceptibility to antimicrobials in Bacteroides fragilis

ABSTRACT Bacteroides fragilis is the strict anaerobic bacteria most commonly found in human infections, and has a high mortality rate. Among other virulence factors, the remarkable ability to acquire resistance to a variety of antimicrobial agents and to tolerate nanomolar concentrations of oxygen explains in part their success in causing infection and colonizing the mucosa. Much attention has been given to genes related to multiple drug resistance derived from plasmids, integrons or transposon, but such genes are also detected in chromosomal systems, like the mar (multiple antibiotic resistance) locus, that confer resistance to a range of drugs. Regulators like MarR, that control expression of the locus mar, also regulate resistance to organic solvents, disinfectants and oxygen reactive species are important players in these events. Strains derived from the parental strain 638R, with mutations in the genes hereby known as marRI (BF638R_3159) and marRII (BF638R_3706) were constructed by gene disruption using a suicide plasmid. Phenotypic response of the mutant strains to hydrogen peroxide, cell survival assay against exposure to oxygen, biofilm formation, resistance to bile salts and resistance to antibiotics was evaluated. The results showed that the mutant strains exhibit statistically significant differences in their response to oxygen stress, but no changes were observed in survival when exposed to bile salts. Biofilm formation was not affected by either gene disruption. Both mutant strains however, became more sensitive to multiple antimicrobial drugs tested. This indicates that as observed in other bacterial species, MarR are an important resistance mechanism in B. fragilis.

Antimicrobial Susceptibility of Clinical Isolates of Bacteroides fragilis Group Organisms Recovered from 2009 to 2012 in a Korean Hospital

BACKGROUND: Periodic monitoring of antimicrobial resistance trends of clinically important anaerobic bacteria such as Bacteroides fragilis group organisms is required. We determined the antimicrobial susceptibilities of clinical isolates of B. fragilis group organisms recovered from 2009 to 2012 in a tertiary-care hospital in Korea. METHODS: A total of 180 nonduplicate clinical isolates of B. fragilis group organisms were collected in a tertiary care hospital. The species were identified by conventional methods: the ATB 32A rapid identification system (bioMerieux, France) and the Vitek MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (bioMerieux). Antimicrobial susceptibility was determined by the CLSI agar dilution method. RESULTS: Imipenem and meropenem resistance rates were 0-6% for B. fragilis group isolates. The rate of resistance to piperacillin-tazobactam was 2% for B. fragilis and 0% for other Bacteroides species, but 17% for B. thetaiotaomicron isolates. High resistance rates to piperacillin (72% and 69%), cefotetan (89% and 58%), and clindamycin (83% and 69%) were observed for B. thetaiotaomicron and other Bacteroides spp. The moxifloxacin resistance rate was 27% for other Bacteroides spp. The MIC50 and MIC90 of tigecycline were 2-4 microg/mL and 8-16 microg/mL, respectively. No isolates were resistant to chloramphenicol or metronidazole. CONCLUSIONS: Imipenem, meropenem, chloramphenicol, and metronidazole remain active against B. fragilis group isolates. Moxifloxacin and tigecycline resistance rates are 2-27% and 8-15% for B. fragilis group isolates, respectively.

Prevalence and antibiotic susceptibility of Bacteroides fragilis group isolated from stool samples in North Lebanon

Fifty one strains of the Bacteroides fragilis group were isolated from 45 fecal samples. Classical phenotypic identification showed that 16 isolates were B. thetaiotaomicron, 12 B. uniformis, 9 B. eggerthii,7 B. vulgatus,3 B. caccae,2 Parabacteroides distasonis with 1 identified B. ovatus and 1 B. fragilis. The 51 strains were tested for susceptibility against 16 antimicrobial agents and the MICs for metronidazole were determined. The tests showed that imipenem, meropenem and chloram-phenicol were the most effective antibiotics (98%, 98% and 92.16% of susceptibility, respectively) followed by ticarcillin/clavulanic acid, piperacillin/tazobactam, rifampin (88.24% susceptibility), moxifloxacin 86.27% and tigecycline 84.31%. Ofloxacin and cefotaxime were the least effective antibiotics with 27.45% and 0% of activity respectively. Only six of the 51 isolated strains were resistant to metronidazole with MICs = 64 mg/L (1 strain) and > 256 mg/L (5 strains).

Resistance Trends of Bacteroides fragilis Group Over an 8-Year Period, 1997-2004, in Korea / 대한진단검사의학회지

BACKGROUND: Bacteroides fragilis group organisms are the most frequently isolated anaerobes in human infections. Increasing resistance to various antimicrobial agents is a significant problem in choosing appropriate antimicrobial agents to treat anaerobic infections. Periodic monitoring of the regional resistance trends of B. fragilis group isolates is needed. METHODS: A total of 466 nonduplicate clinical isolates of B. fragilis group organisms (276 B. fragilis, 106 Bacteroides thetaiotaomicron, and 84 other B. fragilis group organisms) were collected during the 8-yr period from 1997 to 2004 in a Korean university hospital. Minimum inhibitory concentrations to various antimicrobial agents were determined by the CLSI agar dilution method. RESULTS: Eight isolates were resistant to imipenem. Additionally, the resistance rates to cefotetan were decreased in B. thetaiotaomicron, while those for clindamycin were significantly increased compared to the rates found in previous studies. Depending on species, resistance rates were 1-4% for imipenem, 1-6% for piperacillin-tazobactam, 4-11% for cefoxitin, 33-49% for piperacillin, 14-60% for cefotetan, and 51-76% for clindamycin. No isolates were resistant to chloramphenicol or metronidazole. CONCLUSIONS: Piperacillin-tazobactam, cefoxitin, imipenem, chloramphenicol, and metronidazole are still active against B. fragilis group isolates, while clindamycin no longer has a value as an empirical therapeutic agent in Korea. Furthermore, this study identified the first imipenem-resistant B. fragilis group isolates in Korea.

Determinaçäo da suscetibilidade a antimicrobianos em cepas do grupo Bacteroides fragilis: situaçäo atual e perspectivas / Antimicrobial susceptibility tests for Bacteroides fragilis group strains: current situation and perspectives

Testes de suscetibilidade a antimicrobianos para 44 cepas do grupo Bacteroides fragilis foram realizafos, com o objtivo de comparar os resultados obtidos através de uma modificaçäo da técnica de Wilkins & Thiel e o método de diluiçäo em ágar recomendado pelo NCCLS. As concentraçöes críticas (breakpoints) para o método de eluiçäo do disco no caldo e o de referência foram: cefoxitina, 18 e 16µg/ml, tetraciclina, 6 e 4µg/ml, e clindamicina, 2 e 8µg/ml, respectivamente. Um percentual de concordância de 77,3 por cento foi obtido para cefoxitina, 75 por cento para clindamicina e 63,6 por cento para tetraciclina. Em relaçäo a cloranfenicol e metronidazol, o percentual de concordância obtido, quando comparados os dois métodos, foi de 100 por cento. Estes dados indicam a falta de correlaçäo entre os dois métodos para tetraciclina, cefaloxitina e clindamicina e sugerem a necessidade de cuidados na interpretaçäo, se o teste avaliado for utilizado. O teste de eluiçäo do disco no caldo näo é mais recomendado pelo NCCLS. Encontrar um teste simples, rápido, econômico, reproduzível e facilmente comercializável para testar a suscetibilidade de bactérias anaeróbias estritas a antimicrobianos, é, atualmente, o desafio da microbiologia dos anaeróbios

Susceptibility of clinical isolates of Bacteroides fragilis group strains to cefoxitin, cefoperazone and ticarcillin/clavulanate

A total of 40 strains of the B. fragilis group was isolated from clinical specimens in two hospital centers in Fortaleza from 1993 to 1997. The most frequently isolated species was Bacteroides fragilis (19 strains) and most isolates came from intra-abdominal and wound infections. The susceptibility profile was traced for cefoxitin, cefoperazone and ticarcillin-clavulanate by using the agar dilution reference method. All isolates were susceptible to ticarcillin-clavulanate (128/2mug/ml). Resistance rates of 15 and 70 percent were detected to cefoxitin (64mug/ml) and cefoperazone (64mug/ml), respectively. Such regional results permit a better orientation in choosing this group of antibiotics for prophylaxis and therapy especially in relation to cefoxitin, which is frequently used in the hospital centers studied.

Transfer of clindamicyn resistance between Bacteroides fragilis group strains isolated from clinical specimens

Clindamycin resistance was trasferred by a conjugation-like from Bacteroides thetaiotaomicron 52, a multiple antibiotic-resistant strain isolated from clinical specimens, to other Bacteroides species. A possible association between a plasmid detected in the donor strain and clindamycin resistance in discussed

Nitroimidazoles, Part XXIII--activity of satranidazole series against anaerobic infections.

A large number of nitroimidazoles have been examined for in vitro activity against three anaerobes - Bacteroides fragilis (Bf), a strain of Bf resistant to metronidazole (16a) and Clostridium perfringens and many found to be active. Among these may be mentioned 1-methyl-5-nitroimidazoles carrying N - bound hetetocycles at position 2, such as satranidazole 1a, 1b, 1c, 1k, 1n and 1v which are at least twice as active as metronidazole (16a), ornidazole (16b) and tinidazole (16c). Even more active are 5-nitroimidazolyl benzimidazole 5d, -thiazolidinone 6b and thiadiazolidine dioxide 8a. Many other types of compounds derived from 1-methyl-2-amino-5-nitroimidazole are feebly active. Among 5-nitroimidazoles with a carbon substituent at position 2, 16a, 16b and 16c are equiactive while dimetridazole 14f is more active than 16a against Bf. Some 2-vinyl derivatives are very potent, with 18f and 18i being outstanding. Activity better than that of metronidazole is seen for nitroimidazooxazepines, e.g. 29d. 5-Nitroimidazoles are more active against anaerobes than 4-nitro isomers. Antianaerobic and antiamoebic activities generally run parallel in these classes of compounds. The study has led to the elaboration of the antianaerobic profile of satranidazole 1a.

Teste de sensibilidade a antimicrobianos: técnica de difusäo em ágar para Bacteroides resistentes à bile / Antimicrobial susceptibility testing: disk diffusion method for bile-resistance Bacteroides

Uma modificaçäo da técnica de difusäo em ágar de BARRY et al. (1970), para testar a sensibilidade de Bacteroides bile-resistentes a antimicrobianos, é sugerida neste trabalho. Foram utilizadas 101 amostras de bactérias anaeróbicas estritas isoladas de espécimes fecais e de nateriais clínicos de pacientes provenientes do Hospital Universitário Walter Cantídio da Universidade Federal do Ceará. Após caracterizaçäo a nível de gênero, a sensibilidade das cepas isoladas frente a penicilina G e clorafenicol foi determinada através da técnica da camada sobposta e da técnica de referência de diluiçäo em ágar. Os resultados encontrados foram comparados utilizando-se a análise de regressäo linear pelo método da "percentagem de erro ligada" de METZLER e DEHAAN. Uma boa correlaçäo entre as CIMs e os diâmetros dos halos de inibiçäo para pencilinaG foi encontrada. Para o cloranfenicol, a correlaçäo näo pode ser estabelecida, visto näo terem sido isoladas cepas resistentes a este antimicrobiano. A técnica proposta mostrou-se reproduzível para os antibióticos testados

Susceptibility to current antimicrobial agents of Bacteroides fragilis.

Agar dilution technique susceptibility test of isolated Bacteroides fragilis from the normal healthy women's and infected gynecological patients' cervical areas were studied with current antimicrobial agents. Among the N H W group, imipenem had the lowest MIC90 while cefoxitin had the highest value. Metronidazole, chloramphenicol, imipenem and piperacillin had differentiated-lower values of MIC90 and MIC90 than the others. In the I G P group, imipenem also had the lowest value of MIC90 while benzylpenicillin had the highest value. The different values of MIC90 and MIC50 less than "1" were seen in metronidazole, chloramphenicol and imipenem. The significant role of MIC90 and MIC50 was discussed in this article. Although the isolated strains had beta-lactamase enzymes, the antimicrobials resistances were not correlated with the specific enzymes. Also in this article, the significant role of anaerobic component in mixed infection was also discussed.

Teste alternativo de sensibilidade de bactérias anaeróbias estritas a agentes antimicrobianos / Alternative susceptibility test of anaerobic bacteria to antimicrobial agents

Um total de 25 amostras de bactérias anaeróbias, Bacteroides fragilis, Clostridium perfringens e Clostridium difficile foram avaliadas quanto a sensibilidade a vários antimicrobi anos pelo método de eluiçäo do disco em caldo BHI pré-reduzido esterilizado em anaerobiose (PRAS) e os resultados foram comparados com aqueles obtidos por uma metodologia de BHI näo-PRAS. Uma grande correlaçäo entre os dois métodos justifica a indicaçäo desta alternativa como procedimento satisfatório em rotina bacteriológica