Resistance Of Anaerobic Bacteria Research Articles

The European committee on antimicrobial susceptibility testing disc diffusion susceptibility testing method for frequently isolated anaerobic bacteria

ObjectivesAntimicrobial resistance in anaerobic bacteria is increasing and there is a link between inappropriate antimicrobial therapy and poor clinical outcome in the treatment of infections caused by anaerobic bacteria. Accurate and timely antimicrobial susceptibility testing of anaerobic bacteria is therefore of critical importance. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has recently described a disc diffusion susceptibility testing method for anaerobic bacteria using fastidious anaerobe agar (FAA) supplemented with 5% defibrinated horse blood (HB). This method was previously validated for Bacteroides spp. only. The aim of this study was to determine the suitability of FAA-HB for disc diffusion and also for frequently isolated anaerobic bacteria. MethodsClinical isolates, including 54 Bacteroides/Phocaeicola/Parabacteroides spp., 49 Prevotella spp., 51 Fusobacterium necrophorum, 58 Clostridium perfringens, and 54 Cutibacterium acnes were evaluated against six antimicrobial agents. MICs were determined by agar dilution following Clinical and Laboratory Standards Institute methodology, modified to use FAA-HB as recommended by EUCAST, instead of supplemented Brucella agar, and disc diffusion was performed on FAA-HB following EUCAST methodology. ResultsResults for quality control strains were reproducible, with 99.3% of zones within range. Disc diffusion by EUCAST methodology was able to distinguish between susceptible and resistant isolates of anaerobic bacteria for benzylpenicillin, piperacillin-tazobactam, meropenem, clindamycin, and metronidazole (98.7% correct categorization). No isolates resistant to vancomycin were tested, but zone diameters correctly categorized the susceptible isolates, and there was a logical relationship between MICs and inhibition zones. DiscussionThe recently published EUCAST method for disc diffusion for anaerobic bacteria based on FAA-HB is a reproducible and accurate method for susceptibility testing of frequently isolated anaerobic bacteria.

Insertional Inactivation of Prevotella intermedia OxyR Results in Reduced Survival with Oxidative Stress and in the Presence of Host Cells.

One of the most abundant bacteria in the subgingival pockets of patients with bleeding following mechanical periodontal therapy is Prevotella intermedia. However, despite its abundance, the molecular mechanisms of its contribution to periodontal disease are not well known. This is mainly due to the lack of genetic tools that would allow examination of the role of predicted virulence factors in the pathogenesis of this bacterium. Here, we report on the first mutant in the P. intermedia OMA14 strain. The mutation is an allelic exchange replacement of the sequences coding for a putative OxyR regulator with ermF sequences coding for the macrolide–lincosamide resistance in anaerobic bacteria. The mutant is severely impaired in its ability to grow with eukaryotic cells, indicating that it is an important target for interventional strategies. Further analyses reveal that its ability to grow with oxidative stress species, in the form of hydrogen peroxide and oxygen, is severely affected. Transcriptome analysis reveals that the major deregulated genes code for the alkylhydroperoxide reductase system, AhpCF, mediating protection from peroxide stress. Moreover, genes coding for Dps, CydA and Ftn are downregulated in the mutant strain, as further verified using qRT-PCR analysis. In conclusion, we succeeded in generating the first P. intermedia mutant and show that the OxyR-deficient strain is unable to survive with a variety of host cells as well as with oxidative stress.

INFECTIOUS COMPLICATIONS CAUSED BY NON-SPOREFORMING ANAEROBIC BACTERIA IN CANCER PATIENTS. RELEVANCE OF THE PROBLEM

The purpose of the study : to identify the significance of anaerobic bacteria and analyze their role in the development of infectious complications in cancer patients. Material and Methods . The review includes data from clinical and in vitro studies published in Russian and international press for the period from 1989 to 2018. Results . Data analysis has shown that many aspects related to anaerobic non-sporeforming bacteria are insufficiently studied, although they can cause severe hospital infections. This is especially true for patients with immune system defects, including cancer patients. In this category of patients, anaerobic bacteria can cause infections of the maxillofacial region, intra-abdominal infections, lower respiratory tract infections, urinary infections, and blood flow infections. In cancer patients, infectious complications are more severe, and may adversely affect treatment outcomes. A long process of anaerobic cultivation dictates the need for empirical treatment of infection for an average of 6 to 7 days. Since the middle of the last century, metronidazole was the «gold standard» of therapy. However, today the situation has changed dramatically. More than 80 % of anaerobic strains are resistant to metronidazole. The problem of resistance of anaerobic bacteria to other antibacterial drugs has not been sufficiently studied. Conclusion . It is necessary to develop therapeutic approaches based on current data on the resistance mechanisms of non-sporeforming anaerobic bacteria.

Antimicrobial susceptibility against metronidazole and carbapenem in clinical anaerobic isolates from Pakistan

BackgroundGlobally metronidazole and carbapenem resistance in anaerobic organisms is increasing necessitating continuous surveillance to guide selection of empirical treatment. In this study we have determined metronidazole resistance in anaerobes using MIC Evaluator strips (M.I.C.E strips). Carbapenem resistance was evaluated only in metronidazole resistant isolates.Material and methodsThe study was conducted at the Aga Khan University (AKU) Hospital laboratory, Karachi, Pakistan (2014–2017). Metronidazole and imipenem resistance was evaluated using M.I.C.E strips and minimum inhibitory concentrations (MICs) were interpreted using Clinical Laboratory Standards Institute (CLSI) criteria. Clinical details including demographics, prolonged hospital stay, malignancy, transplant, dialysis, diabetes, site of infection and outcome were analyzed for association with metronidazole resistance.ResultsOf the 223 clinically significant isolates, 39 (17.5%) were metronidazole resistant (excluding the inherently resistant organisms; for example Cutibacterium species). Imipenem resistance was determined in 29 metronidazole resistant isolates and of these 7 (24.1%) were found to be resistant. Proportion of metronidazole resistant strains was highest amongst Bacteroides species. A significant increase in metronidazole resistance from 12.3% in 2010–2011 to 17.5% in the current study was found. Carbapenem resistance also emerged in the period 2014–2017.Isolates from malignancy and transplant patients showed lower odds of developing metronidazole resistance (0.003(95% CI: 1.7–17.9)). Prolonged hospital stay was not associated with metronidazole resistance (1.1((95% CI: 0.5–2.5)).ConclusionThe rising trend of metronidazole resistance and emergence of carbapenem resistance in anaerobic bacteria is alarming. Continued surveillance with strengthening of laboratory capacity regarding anaerobic susceptibility testing is urgently needed in Pakistan.

Propolis, A Hope for the Future in Treating Resistant Periodontal Pathogens.

Introduction: Periodontitis is one of the most common causes of tooth loss worldwide. Recently, special attention has been paid to natural medication for its treatment. For this purpose, propolis (bee glue) activity has also been investigated. Its antibacterial properties are mainly attributed to flavonones pinocembrin, flavonols galangin and to the caffeic acid phenethyl ester. This study is aimed at evaluating the antimicrobial effects of propolis from Pakistan on 35 clinical isolates of pigmented anaerobic periodontal pathogens.Methods: This study was conducted in the Microbiology department, University of Health Sciences, Lahore, Pakistan. Pathogens included were Porphyromonas asaccharolytica (n=9), Porphyromonas gingivalis (n=13), Prevotella intermedia (n=9), Prevotella melaninogenica (n=4). Minimum inhibitory concentration (MIC) to three antibiotics was obtained by E-test method. All strains were sensitive to amoxicillin plus clavulanic acid and metronidazole, but 100% of P asaccharolytica and P melaninogenica strains displayed intermediate resistance to tetracycline while 69.2% P gingivalis and 100% P intermedia strains exhibited complete resistance to tetracycline. Screening for antibacterial activity of propolis extract was done by agar well diffusion assay, and all strains were found sensitive to ethanolic extract of propolis.Results: MIC was obtained by agar incorporation technique with values ranging from 0.064 to 0.512 mg/ml. It was also noticed that percentage yield of ethanolic extract of propolis prepared from ultrasonic extraction method was higher compared to extract obtained with maceration.Conclusion: These results indicate that propolis from this region has potent antimicrobial activity against pigmented anaerobic periodontal pathogens. Taking into consideration the increasing resistance in anaerobic bacteria, this effective antimicrobial activity of propolis gives hope in the treatment of oral cavity diseases.

Anaerobic infections in children

Anaerobic bacteria commonly cause infection in children. Anaerobes are the most predominant components of the normal human skin and mucous membrane bacterial flora, and are therefore a common cause of bacterial infections of endogenous origin. Because of their fastidious nature, they are difficult to isolate from infectious sites and are often overlooked. Anaerobic infections can occur in all body sites, including the central nervous system, oral cavity, head and neck, chest, abdomen, pelvis, skin, and soft tissues. Anaerobic bacteria colonize the newborn after delivery and have been recovered from several types of neonatal infections. These include cellulitis of the site of fetal monitoring, neonatal aspiration pneumonia, bacteremia, conjunctivitis, omphalitis, and infant botulism. The lack of directing adequate therapy against these organisms may lead to clinical failures. Their isolation requires appropriate methods of collection, transportation, and cultivation of specimens. Treatment of anaerobic infection is complicated by the slow growth of these organisms, by their polymicrobial nature, and by the growing resistance of anaerobic bacteria to antimicrobials. Antimicrobial therapy is often the only form of therapy required, whereas in other cases it is an important adjunct to a surgical approach. Because anaerobic bacteria generally are recovered mixed with aerobic organisms, the choice of appropriate antimicrobial agents should provide for adequate coverage of both types of pathogens.

Development of antimicrobial resistance in the normal anaerobic microbiota during one year after administration of clindamycin or ciprofloxacin

Thirty healthy subjects (15 males and 15 females) were randomly assigned in three groups and clindamycin (150 mg qid) or ciprofloxacin (500 mg bid) or placebo was given for a 10-day period. Skin, nasal, saliva, faeces samples were collected at day – 1, day 11, 1 month, 2 months, 4 months and 12 months post administration for microbiological analysis. Ciprofloxacin or clindamycin had no impact on the anaerobic skin microbiota and the proportions of antibiotic resistant anaerobic bacteria were similar as in the placebo group. Ciprofloxacin had impact on the Propionibacterium acnes in the nasal microbiota that normalized after 1 month, however, ciprofloxacin-resistant P. acnes strains increased at month 2 and month 12. Clindamycin had no impact on the nasal microbiota. In the oropharyngeal microbiota, a higher proportion of ciprofloxacin resistant Veillonella was found, it lasting up to 12 months post dosing. In the clindamycin group, clindamycin-resistant Prevotella spp. were found in increased proportions compared to placebo at various time points except month 4 in the saliva samples. The relative proportion of ciprofloxacin-resistant Bifidobacteria increased in the faecal samples on day 11, 1 month, 4 months and 12 months post dosing compared to placebo. The proportion of clindamycin-resistant Bacteroides spp. increased at 1, 2, 4 and 12 months post dosing compared to placebo in the faecal samples. No Clostridium difficile was recovered from any of the samples from any of the volunteers at any visit. The concentrations of ciprofloxacin or clindamycin in the faeces were higher than the MICs for most of the organisms present in the normal microbiota. No obvious correlation between the groups in resistant patterns for anaerobic bacteria was observed. In conclusion, based on the microbiological data of the microbiota as well as the results of the bioassays for ciprofloxacin and clindamycin concentrations in the faecal samples, oral administration of ciprofloxacin and clindamycin has an impact on the anaerobic microbiota and may have a long-term effect on the development and persistence of antibiotic-resistant anaerobes in the normal microbiota.

High prevalence and resistance rates to antibiotics in anaerobic bacteria in specimens from patients with chronic balanitis

Aim of the study was to assess both prevalence and antibiotic resistance in anaerobic bacteria from glans penis skin of 70 adults. Strain susceptibility was determined by breakpoint susceptibility test or E test. In 9 asymptomatic, 48 untreated and 13 treated symptomatic patients, anaerobes were found in 22.2%, 70.8% and 53.3%, respectively. Gram-positive strains (GPAs) were 2.2-fold more common than Gram-negative ones. Prevalent Gram-negative (GNAs) and GPAs were Prevotella spp. and anaerobic cocci, respectively. Clostridium difficile strain was found in an untreated patient. In GNAs, resistance rates to amoxicillin, metronidazole, clindamycin, tetracycline, levofloxacin, and amoxicillin/clavulanate were 42.1, 0, 52.6, 53.3, 86.7 and 5.2%, respectively. In GPAs, the resistance rates to metronidazole, clindamycin, tetracycline, levofloxacin and amoxicillin/clavulanate were 18.2, 34.1, 52.6, 36.8 and 0%, respectively. In conclusion, anaerobes were 1.6-fold more frequent in untreated symptomatic patients compared with other patients, suggesting their participation in development of chronic balanitis. GPAs were more common than GNAs. The resistance rates to amoxicillin, clindamycin, tetracycline, and levofloxacin were high. Most active agents were metronidazole and amoxicillin/clavulanate. Resistance in anaerobes varies according to sites of specimens and years of study.

Prevalence and type distribution of human papillomavirus infection in women from Datong, China

This survey of 931 cervical specimens in women from Datong, China indicates that the overall human papillomavirus (HPV) prevalence was 18.6%, and the most prevalent high-risk HPV types were 16, 58, 18, 52 and 33. This study demonstrates the epidemiology of HPV infection in Datong and the potential impact of vaccination in this region.

Prevalence of Antibiotic Resistance in Anaerobic Bacteria: Worrisome Developments

Antibiotic-resistant anaerobic bacteria have become increasingly recognized as a confounding factor in the selection of therapeutic agents. The use of potent, broad-spectrum antibiotics as empirical therapy, along with appropriate adjunctive measures, has, in some ways, masked the magnitude of the antibiotic resistance problem that parallels that observed for nonanaerobic pathogens. The use of standardized testing methods that recognize resistance and an understanding of resistance mechanisms have become essential for the treatment of patients and the development of new agents.

Mechanism of quinolone resistance in anaerobic bacteria

Several recently developed quinolones have excellent activity against a broad range of aerobic and anaerobic bacteria and are thus potential drugs for the treatment of serious anaerobic and mixed infections. Resistance to quinolones is increasing worldwide, but is still relatively infrequent among anaerobes. Two main mechanisms, alteration of target enzymes (gyrase and topoisomerase IV) caused by chromosomal mutations in encoding genes, or reduced intracellular accumulation due to increased efflux of the drug, are associated with quinolone resistance. These mechanisms have also been found in anaerobic species. High-level resistance to the newer broad-spectrum quinolones often requires stepwise mutations in target genes. The increasing emergence of resistance among anaerobes may be a consequence of previous widespread use of quinolones, which may have enriched first-step mutants in the intestinal tract. Quinolone resistance in the Bacteroides fragilis group strains is strongly correlated with amino acid substitutions at positions 82 and 86 in GyrA (equivalent to positions 83 and 87 of Escherichia coli). Several studies have indicated that B. fragilis group strains possess efflux pump systems that actively expel quinolones, leading to resistance. DNA gyrase seems also to be the primary target for quinolones in Clostridium difficile, since amino acid substitutions in GyrA and GyrB have been detected in resistant strains. To what extent other mechanisms, such as mutational events in other target genes or alterations in outer-membrane proteins, contribute to resistance among anaerobes needs to be further investigated.

Antibiotic regimens for endometritis after delivery.

Post-partum endometritis, which is more common after cesarean section, occurs when vaginal organisms invade the endometrial cavity during labour and birth. Antibiotic treatment is warranted. The effect of different antibiotic regimens for the treatment of postpartum endometritis on failure of therapy and complications was systematically reviewed. We searched the Cochrane Pregnancy and Childbirth Group's trials register and the Cochrane Controlled Trials Register. Date of last search: June 2001. Randomised trials of different antibiotic regimens for postpartum endometritis, after cesarean section or vaginal birth, where outcomes of treatment failure or complications were reported were selected. Data were abstracted independently by the reviewers. Comparisons were made between different types of antibiotic regimen, based on type of antibiotic and duration and route of administration. Summary relative risks were calculated. Forty-seven trials were included. Overall the studies were methodologically poor. In the intent-to-treat analysis, fifteen studies comparing clindamycin and an aminoglycoside with another regimen showed more treatment failures with another regimen (relative risk (RR) 1.32; 95% confidence interval (CI) 1.09-1.60). Failures of those regimens with poor activity against penicillin resistant anaerobic bacteria were more likely (RR 1.53; 95% CI 1.10-2.13). In four studies that compared continued oral antibiotic therapy after intravenous therapy, no differences were found in recurrent endometritis or other outcomes. There was no evidence of difference in incidence of allergic reactions. Cephalosporins were associated with less diarrhea. The combination of gentamicin and clindamycin is appropriate for the treatment of endometritis. Regimens with activity against penicillin resistant anaerobic bacteria are better than those without. There is no evidence that any one regimen is associated with fewer side effects. Once uncomplicated endometritis has clinically improved with intravenous therapy, oral therapy is not needed.

GyrA mutations associated with quinolone resistance in Bacteroides fragilis group strains.

Mutations in the gyrA gene contribute considerably to quinolone resistance in Escherichia coli. Mechanisms for quinolone resistance in anaerobic bacteria are less well studied. The Bacteroides fragilis group are the anaerobic organisms most frequently isolated from patients with bacteremia and intraabdominal infections. Forty-four clinafloxacin-resistant and-susceptible fecal and clinical isolates of the B. fragilis group (eight Bacteroides fragilis, three Bacteroides ovatus, five Bacteroides thetaiotaomicron, six Bacteroides uniformis, and 22 Bacteroides vulgatus) and six ATCC strains of the B. fragilis group were analyzed as follows: (i) determination of susceptibility to ciprofloxacin, levofloxacin, moxifloxacin, and clinafloxacin by the agar dilution method and (ii) sequencing of the gyrA quinolone resistance-determining region (QRDR) located between amino acid residues equivalent to Ala-67 through Gln-106 in E. coli. Amino acid substitutions were found at hotspots at positions 82 (n = 15) and 86 (n = 8). Strains with Ser82Leu substitutions (n = 13) were highly resistant to all quinolones tested. Mutations in other positions of gyrA were also frequently found in quinolone-resistant and -susceptible isolates. Eight clinical strains that lacked mutations in their QRDR were susceptible to at least two of the quinolones tested. Although newer quinolones have good antimicrobial activity against the B. fragilis group, quinolone resistance in B. fragilis strains can be readily selected in vivo. Mutational events in the QRDR of gyrA seem to contribute to quinolone resistance in Bacteroides species.

Fluoroquinolone resistance in anaerobic bacteria following exposure to levofloxacin, trovafloxacin, and sparfloxacin in an in vitro pharmacodynamic model.

This investigation explored pharmacodynamic characteristics of fluoroquinolones against Bacteroides thetaiotamicron and the potential for development of resistance. An in vitro model was used to generate kill curves with three fluoroquinolones at various area under the concentration-time curve (AUC)/MIC ratios. Concentration-independent killing was observed. Increases in MICs were noted following exposure to fluoroquinolones at AUC/MIC ratios of 6 to 14.

Antimicrobial resistance in anaerobes.

The development of antibiotic resistance in anaerobic bacteria has a tremendous impact on the selection of antimicrobial agents for empirical therapy. Susceptibility studies have documented the emergence of antimicrobial resistance and indicate distinct differences in resistance patterns related to individual hospitals, geographic regions, and antibiotic-prescribing regimens. Resistance to beta-lactam drugs, clindamycin, tetracyclines, and 5-nitroimidazoles (metronidazole) has been observed. The prime mechanism for resistance to beta-lactam agents is the production of beta-lactamases. Resistance to clindamycin is mediated by modification of the ribosome. Tetracycline resistance is mediated by both tetracycline efflux and ribosomal protection. 5-Nitroimidazole resistance appears to be caused by a combination of decreased antibiotic uptake and decreased nitroreductase activity. The level of chloramphenicol susceptibility remains quite high, whereas uniform resistance to aminoglycosides and quinolones is observed. Understanding the mechanisms of resistance is critical for both informed selection of antimicrobial therapy and the design of new antimicrobial agents.

Emerging resistance of anaerobic bacteria to antimicrobial agents in South Korea.

In previous studies, Bacteroides fragilis group organisms isolated from Korean patients were more frequently resistant to various antimicrobial agents, including clindamycin, than were isolates in other countries. A recent report of increased resistance of Peptostreptococcus species prompted us to include such isolates in a study of antimicrobial susceptibility. anaerobes isolated in 1994 at a tertiary care hospital in Seoul were tested by agar dilution method. None of the B. fragilis group organisms were resistant to imipenem, cefoxitin, chloramphenicol, or metronidazole. However, 6.7% were resistant to ampicillin/sulbactam, 20.2% to cefotetan, 30.3% to piperacillin, 48.3% to cefotaxime, and 42.7% to clindamycin. Almost all of the Clostridium perfringens isolates were susceptible to all of the agents tested, except tetracycline. Peptostreptococcus isolates were susceptible to piperacillin, cefotaxime, and imipenem, while 7.4% were resistant to penicillin G, cefotetan, and metronidazole, and 25.9% were resistant to clindamycin. The isolates resistant to penicillin G, cefotetan, and metronidazole were identified as Peptostreptococcus anaerobius. In conclusion, besides the well-known high rate of resistance of B. fragilis group organisms to clindamycin, the emergence of resistance of Peptostreptococcus species isolates to beta-lactam drugs has become obvious in Korea.

Resistance of anaerobic bacteria to antimicrobial agents in Spain

As a consequence of antibiotic consumption, the entire microbial ecosystem attached to man is evolving towards resistance. In Spain, penicillin resistance (MIC > 0.5 mg/l) is found in about 10% of Peptostreptococcus, Clostridium perfringens and Eubacterium, and in 50% of Veillonella. Cefoxitin resistance ( > 2 mg/l) is present in 10 to 20% of Peptostreptococcus and Clostridium, and in 50% of Eubacterium; 21% of Bacteroides (fragilis group) strains are resistant to 16 mg/l. A very low rate of imipenem resistance (> or = 128 mg/l) is found among Bacteroides (1%), but for 5% of the isolates MICs of imipenem are 2 to 4 mg/l. Metronidazole resistance ( > 8 mg/l) is found in 5 to 10% of Peptostreptococcus, Clostridium and Veillonella, and in less than 1% of the Bacteroides fragilis group. Erythromycin resistance ( > 2 mg/l) is present in over two-thirds of the Peptostreptococcus, Veillonella and Fusobacterium isolates, and in 27% of the Clostridium perfringens strains. Clindamycin resistance ( > 4 mg/l) is found in 10 to 20% of the Peptostreptococcus, Clostridium and Eubacterium isolates, and in 20% of the Bacteroides of the fragilis group, this rate being higher (30%) among faecal isolates.

Activity of amoxycillin/clavulanic acid against anaerobes isolates from hospital infections

The activity of the association Amoxycillin/Clavulanic acid against anaerobic bacteria recently isolated from hospital infections was determined by agar dilution method. The results have shown a very good susceptibility in vitro of the strains tested. MIC were generally 8 mg/l or less. The most important mechanism of betalactam resistance in anaerobic bacteria is betalactamase production (cephalosporinases and penicillinases) so the interest in compounds like Clavulanic Acid, an inhibitor of this enzyme as a method of overcoming bacterial resistance due to a betalactamase production. For instance Bacteroides fragilis strains one the most important anaerobic pathogenic bacteria regularly (near 90%) produce a clavulanic-susceptible type VI betalactamase (Richmond & Sikes) and other Bacteroides produce different types of clavulanic-susceptible betalactamase. The association Amoxycillin/Clavulanic Acid has an extended activity against a large variety of anaerobic bacteria including the majority of the pathogenic species. We have studied the susceptibility of 200 strains of anaerobic bacteria recently isolated of clinical cases, by the agar dilution method. L'activité de l'association amoxicilline-acide clavulanique contre des bactéries anaérobies récemment isolées d'infections hospitalières a été déterminée par la méthode de la dilution en gélose. La sensibilité in vitro des souches étudiées s'est révélée très bonne. La CMI était généralement inférieure ou égale à 8 mg/l. Le principal mécanisme de la résistance aux béta-lactamines chez les bactéries anaérobies est la production de béta-lactamases (céphalosporinases et pénicillinases), d'où l'intérêt des composés comme l'acide clavulanique, qui inhibent cette enzyme, pour surmonter les résistances de ce type. Par exemple, les souches de Bactéroides fragilis , l'une des plus importantes bactéries pathogènes anaérobies, produisent régulièrement (dans près de 90% des cas) une béta-lactamase type VI sensible à l'acide clavulanique (Richmond & Sikes); d'autres Bactéroides produisent divers types de béta-lactamases également sensibles à l'acide clavulanique. L'association amoxicilline-acide clavulanique est active sur un large éventail de bactéries anaérobies comprenant la plupart des espèces pathogènes. Nous avons étudié la sensibilité de 200 souches de bactéries anaérobies récemment isolées dans des cas cliniques par la méthode de la dilution en gélose.

Resistance to β-Lactam Antibiotics in Anaerobic Bacteria

The known mechanisms of beta-lactam resistance in anaerobic bacteria involve production of beta-lactamases, alteration of penicillin-binding proteins, and blocked penetration of beta-lactam antibiotics through bacterial outer membranes. The most important factor in beta-lactam resistance is production of beta-lactamases, which have been found in various Bacteroides, Fusobacterium, and Clostridium species. beta-Lactam resistance in Bacteroides fragilis is commonly mediated by beta-lactamases that are mainly cephalosporinase in character. B. fragilis strains can also produce penicillinases and enzymes inactivating cefoxitin and imipenem. The non-fragilis species of Bacteroides produce beta-lactamases that are mainly penicillinase in character. Penicillinases are also isolated from Fusobacterium nucleatum. Among the clostridia, Clostridium butyricum, Clostridium clostridioforme, and Clostridium ramosum have been shown to produce penicillinases.

Resistance of Anaerobic Bacteria to Antimicrobial Agents

Resistance of Anaerobic Bacteria to Antimicrobial Agents