Antimicrobial Susceptibility Of Anaerobic Bacteria Research Articles

Clinical Findings and Antimicrobial Susceptibility of Anaerobic Bacteria Isolated in Bloodstream Infections.

The objectives of this study were to report on the antimicrobial susceptibility of 141 clinically significant anaerobic bacteria isolated from bloodstream infections between January 2016 and April 2020 in a tertiary-care hospital in Granada (Spain) and to describe the main clinical features of the patients. Species identification was performed by MALDI-TOF MS (Bruker Daltonics, Billerica, MA, USA). Antimicrobial susceptibility tests were performed against penicillin, amoxicillin-clavulanic acid, imipenem, moxifloxacin, clindamycin, metronidazole, and piperacillin-tazobactam using the gradient diffusion technique and EUCAST breakpoints, except for moxifloxacin (CLSI breakpoints). The most frequent anaerobes were Bacteroides (43.9%, n = 62), Clostridium (24.1%, n = 34) and Gram-positive anaerobic cocci (GPACs) (15.6%, n = 22). Almost all tested anaerobes were susceptible to imipenem and amoxicillin-clavulanic acid, except for Bacteroides. High overall resistance rates to clindamycin were observed, especially for Gram-positive anaerobic cocci (GPACs) (54.5%) and for Bacteroides spp. (45.1%). Overall, low resistance rates to almost all antibiotics were observed for Clostridium. High resistance rates to penicillin were also observed for Gram-positive anaerobic bacilli (GPABs) (44.4%), as well as to metronidazole (22.2%), although only nine isolates were included. Antimicrobial susceptibility testing for anaerobes should always be performed in severe infections, such as those localized in the bloodstream. The information obtained contributes to selecting empirical treatments according with local data on resistance.

Antimicrobial susceptibility of anaerobic bacteria in Australia

Aims: Anaerobic infections cause significant morbidity and mortality.1,2 Periodic testing of anaerobes provides local susceptibility data to guide therapy. This study reports the trend of antibiotic susceptibility of clinically significant anaerobes in Victoria.

The Importance of the Early and Appropriate Treatment of Anaerobic Bacteremia Patients.

In the last decades, antibiotic resistance among anaerobes has increased and resistance patterns vary depending on hospitals and regions [1]. The Clinical and Laboratory Standards Institute recommends susceptibility tests for anaerobic organisms isolated from cases of serious infections such as bacteremia, brain abscesses, and endocarditis [2]. However, currently in Korea, even susceptibility tests for anaerobic organisms isolated from blood are not routinely performed in most laboratories because the clinical significance of inappropriate antimicrobial treatment for anaerobic bacteremia (AB) has not been adequately elucidated and convenient routine test methods for anaerobes are limited. Kim et al. investigated the impact of inappropriate therapy on the mortality of AB [3]. They defined inappropriate therapy as a delay in starting antimicrobials even after objective data confirmed an infection or the use of an antimicrobial agent to which the pathogen was known to be resistant according to susceptibility test results [3]. They reported that the incidence of AB in 2012 was low (2.3%), but the mortality rate among AB patients was as high as 21.4% and it was significantly higher in patients who received inappropriate therapy (hazard ratio, 5.4; 95% confidence interval, 1.7–16.9; P = 0.004) [3]. There have been studies on risk factors associated with mortality due to AB, but recent reports on the impact of inappropriate therapy on the mortality of AB patients, based on bacterial susceptibilities are limited. One recent report indicated that malignancy and susceptibility to clindamycin could be used to identify AB patients at a higher risk of 30-day mortality [4]. There is an old prospective study about the adverse clinical outcomes associated with the treatment of Bacteroides bacteremia with an antibiotic that the organism is not susceptible to, using three endpoints (30-day mortality, cure versus failure, and eradication versus persistence) [5]. In the study by Kim et al, the most frequently isolated organisms were Bacteroides spp. (50/70) [3], which are well known for their high virulence and unpredictable resistance. Recently a study that monitored antimicrobial susceptibility of anaerobic bacteria in Korea reported that the resistance rates of B. fragilis to piperacillin (48%), cefotetan (20%), clindamycin (52%), moxifloxacin (12%), and tigecycline (17%) were considerable, whereas cefoxitin, piperacillin-tazobactam, imipenem, and meropenem, which are generally recommended in suspect of systemic infections, were highly suceptible to B. fragilis [6]. Until now, laboratory resources and efforts have been focused on the early detection and correct identification of the causative agents of AB, but considering its impact on mortality, at least routine antimicrobial susceptibility testing of anaerobic organisms isolated from blood is necessary for the appropriate treatment of AB [3]. The agar dilution technique which uses supplemented Brucella agar and the broth microdilution which uses supplemented Brucella broth for Bacteroides and Parabacteroides spp. are approved susceptibility testing methods for anaerobes that can be used for the periodic monitoring of regional and institutional resistance trends and for guiding empirical antimicrobial therapy of anaerobic infections [7]. For routine tests, E-tests or microdilution (in house method) can be used, but the commercial kits such as Sensititre Anaerobe MIC Plate (Trek Diagnostics, Cleveland, OH, USA) are unavailable at the present time [8]. In conclusion, early and appropriate management is important for survival of AB patients. In addition to early detection and correct identification of causative agents, efficient susceptibility testing methods for anaerobes should be introduced and developed for better clinical outcomes.

Multicenter study of antimicrobial susceptibility of anaerobic bacteria in Korea in 2012.

BackgroundPeriodic monitoring of regional or institutional resistance trends of clinically important anaerobic bacteria is recommended, because the resistance of anaerobic pathogens to antimicrobial drugs and inappropriate therapy are associated with poor clinical outcomes. There has been no multicenter study of clinical anaerobic isolates in Korea. We aimed to determine the antimicrobial resistance patterns of clinically important anaerobes at multiple centers in Korea.MethodsA total of 268 non-duplicated clinical isolates of anaerobic bacteria were collected from four large medical centers in Korea in 2012. Antimicrobial susceptibility was tested by the agar dilution method according to the CLSI guidelines. The following antimicrobials were tested: piperacillin, piperacillin-tazobactam, cefoxitin, cefotetan, imipenem, meropenem, clindamycin, moxifloxacin, chloramphenicol, metronidazole, and tigecycline.ResultsOrganisms of the Bacteroides fragilis group were highly susceptible to piperacillin-tazobactam, imipenem, and meropenem, as their resistance rates to these three antimicrobials were lower than 6%. For B. fragilis group isolates and anaerobic gram-positive cocci, the resistance rates to moxifloxacin were 12-25% and 11-13%, respectively. Among B. fragilis group organisms, the resistance rates to tigecycline were 16-17%. Two isolates of Finegoldia magna were non-susceptible to chloramphenicol (minimum inhibitory concentrations of 16-32 mg/L). Resistance patterns were different among the different hospitals.ConclusionsPiperacillin-tazobactam, cefoxitin, and carbapemems are highly active β-lactam agents against most of the anaerobes. The resistance rates to moxifloxacin and tigecycline are slightly higher than those in the previous study.

Isolation, Identification and Antimicrobial Susceptibility of Anaerobic Bacteria: A Study Re-emphasizing Its Role.

Isolation, Identification and Antimicrobial Susceptibility of Anaerobic Bacteria: A Study Re-emphasizing Its Role.

Analysis of the Antimicrobial Susceptibility of Anaerobic Bacteria Isolated from Endodontic Infections in Brazil during a Period of Nine Years

Introduction The purpose of this study was to analyze the susceptibility of some anaerobic species isolated from a Brazilian population at different periods of time by determining a pattern of development of resistance to frequently prescribed antibiotics in endodontics. Methods Root canal samples were collected from infected teeth at different periods of time (2000–2002, 2003–2005, and 2007–2008) and microbiologically identified with conventional culture techniques. The susceptibility of Prevotella intermedia/nigrescens, P. oralis, Fusobacterium nucleatum, and P. micra isolated strains was determined by the minimum inhibitory concentration (MIC) of amoxicillin, amoxicillin + clavulanate, benzylpenicillin, clindamycin, erythromycin, and metronidazole by using the E-test method. Results Amoxicillin and amoxicillin + clavulanate were effective against the majority of species at the different periods of study. Overall, there were low statistical differences regarding the microbial susceptibility between the experimental periods. However, an increase in the anaerobic resistance to penicillin G and clindamycin was observed. Resistance to erythromycin was observed in all species, and there were statistically significant differences between 2000–2002 and 2003–2005 periods for F. nucleatum ( P < .05) and between 2003–2005 and 2007–2008 periods for P. intermedia/nigrescens and P. oralis ( P < .05). Conclusions The antimicrobial resistance of anaerobes isolated from primary endodontic infections showed an increase throughout a period of time regarding a specific Brazilian population.

99 Antimicrobial susceptibility of anaerobic bacteria cultured from patients with cystic fibrosis (CF) and non-CF bronchiectasis

99 Antimicrobial susceptibility of anaerobic bacteria cultured from patients with cystic fibrosis (CF) and non-CF bronchiectasis

Resistance Trends in Antimicrobial Susceptibility of Anaerobic Bacteria, Part II

Despite the suggestions of both the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Microbiology (ASM) Manual of Clinical Microbiology that hospitals should test individual patient isolates to assist in their care, periodically establish patterns of resistance for certain anaerobes, and include these data in the hospital antibiogram, anaerobic susceptibility studies are performed in only a minority of clinical laboratories and their patterns of susceptibility are obtainable mostly from published surveys conducted by a small number of research centers scattered worldwide. The Bacteroides fragilis group species, the most frequently studied anaerobes, have been reported to vary in their frequencies of resistance to all antimicrobial agents worldwide. Limited data exist about the resistance patterns of other genera and species. Part I of this two-part article reviewed the methods used for anaerobic susceptibility testing and the correlation of in vitro susceptibility test results with clinical outcome, and antimicrobial resistance that has been reported for gram-negative and gram-positive anaerobes. Part II of this article reviews mechanisms of resistance among anaerobes to commonly used antimicrobial agents.

Resistance Trends in Antimicrobial Susceptibility of Anaerobic Bacteria, Part I

Despite the suggestions of both the Clinical and Laboratory Standards Institute (CLSI) and the American Society for Microbiology (ASM) Manual of Clinical Microbiology that hospitals should test individual patient isolates to assist in their care, periodically establish patterns of resistance for certain anaerobes, and include these data in the hospital antibiogram, anaerobic susceptibility studies are performed in only a minority of clinical laboratories and their patterns of susceptibility are obtainable mostly from published surveys conducted by a small number of research centers scattered worldwide. The Bacteroides fragilis group species, the most frequently studied anaerobes, have been reported to vary in their frequencies of resistance to all antimicrobial agents worldwide. Limited data exist about the resistance patterns of other genera and species. Part I of this two-part article reviews the methods used for anaerobic susceptibility testing and the correlation of in vitro susceptibility test results with clinical data and antimicrobial resistance that has been reported for gram-negative and gram-positive anaerobes. Part II of this article will review mechanisms of resistance among anaerobes to commonly used antimicrobial agents.

Antimicrobial susceptibility of anaerobic bacteria in Bulgaria

Objectives The antimicrobial susceptibility of anaerobic bacteria isolated from clinical specimens in the referent for Bulgaria anaerobic laboratory was studied in a period of 25 years/1983–2007/. Methods NCCLS – recommended agar dilution methods were used. β-lactamase activity was determined with nitrocefin discs. Results The 29 antimicrobial agents included in the study were divided according to their in vitro activity against the anaerobic isolates into 4 main groups for guiding empirical treatment: 1st group of metronidazole, chloramphenicol, meropenem, imipenem and combinations of β-lactam antibiotics with sulbactam – with high activity and drugs of choice for treatment; 2nd group – clindamycin, cefoxitin, carbenicillin/and azlocillin, piperacillin/ – with a good activity and low percent of resistant strains; 3rd group – of tetracycline and erythromycin with higher percent of resistant strains including the new macrolides as josamycin, clarithromycin, roxithromycin and azithromycin; 4th group – penicillins/ampicillin, amoxicillin, penicillin/and cephalosporins/cefamandole, cefazolin, cefotaxime and cefoperazone/ – not suitable for treatment of infections including Bacteroides fragilis group strains, with a very high percent of resistant strains, probably due to β-lactamase activity in most of the strains. Conclusion A continued updating and a follow-up in the changes of antibiotic susceptibility are necessary in every country as resistance patterns vary not only between geographical regions but also even among medical centers and hospitals which may be connected with differences in antibiotic usage in man and animals.

Antimicrobial susceptibility of anaerobic bacteria in Belgium as determined by E-test methodology

The objective was to collect recent data on the antibiotic susceptibility of clinically significant anaerobes in Belgium. A total of 333 anaerobic clinical isolates from various body sites were prospectively collected between 2005 and 2007 at two tertiary care hospitals in Belgium. The minimal inhibitory concentrations (MICs) were determined using the E-test method for nine anti-anaerobic antibiotics. Sixty-one percent of the isolates were beta-lactamase producers, which explains the poor activity of penicillin. Amoxicillin/clavulanic acid, piperacillin/tazobactam, metronidazole and meropenem were very active against most anaerobes, but around 10% of the Bacteroides fragilis group strains were non-susceptible to the two beta-lactam/beta-lactamase inhibitors. No resistance was observed to metronidazole, while 3% of the Bacteroides spp. had decreased susceptibility to meropenem (MIC > or = 4 mg/L). Cefoxitin, clindamycin and moxifloxacin were less active, with 33%, 52% and 57% of the B. fragilis group being non-susceptible respectively. Tigecycline showed consistently good activity against most anaerobes with MIC(50) and MIC(90) of 0.25 and 2 mg/L. Metronidazole, amoxicillin/clavulanate, piperacillin/tazobactam and meropenem remain good empirical choices when anaerobes are expected in our setting. Because of the occurrence of resistance to most classes of current anti-anaerobic antibiotics, it is recommended that the antimicrobial resistance patterns be monitored regularly in order to guide empirical therapy.

In vitro antimicrobial susceptibility of anaerobic bacteria isolated from caprine footrot

The in vitro antimicrobial susceptibility of Gram-negative anaerobic bacilli commonly isolated from footrot in goats was studied. A total of 97 isolates belonging to the genera Dichelobacter, Fusobacterium, Prevotella, Porphyromonas and Bacteroides, obtained from clinical cases of footrot in south-western Spain between March 2000 and May 2001, were tested against 25 antimicrobial agents comprising beta-lactams, aminoglycosides, macrolides, chloramphenicol, quinolones, lincosamides, sulphonamides and tetracyclines in order to optimise antibiotic treatment of this disease in goats. beta-lactams, tetracyclines and metronidazole displayed the highest in vitro efficacy against the species involved in the pathogenesis of footrot.

Susceptibilidad in vitro de bacterias anaeróbicas en infecciones pleuropulmonares

Aspirative pleuropulmonary infections are usually caused by anaerobic flora of the mouth, mainly Prevotella, Fusobacterium and Peptostreptococcus spp. Penicillin in high doses is the traditional treatment for this type of infections but the rising resistance developed in recent years has induced the empiric use of clindamycin, increasing treatment costs. To study antimicrobial susceptibility of anaerobic bacteria isolated from pleuropulmonary infections. Thirty two strains obtained from bronchoalveolar lavage and 15 strains isolated from pleural effusions between 2000 and 2002, were studied. The phenotype of strains was identified using the semiautomated API 20 A method and their susceptibility to penicillin (PNC), clindamycin (CM) and chloramphenicol (CAF) was tested using the E test methods. All the strains were susceptible to CAF, 95% to CM and 74.4% to PNC. The predominant genus was Prevotella, which also exhibited the higher resistance. As CM and CAF are active "in vitro", high rates of clinical response should be expected. In contrast, PNC is less effective, especially against pigmented Prevotella.

Antimicrobial susceptibility of anaerobic bacteria in New Zealand: 1999–2003

Routine susceptibility testing of all anaerobic organisms is not advocated, but it is useful for laboratories to test periodically for anaerobic organisms and provide local susceptibility data to guide therapy. This study reports the national trend of antibiotic susceptibility of clinically significant anaerobes in New Zealand. Clinical isolates were tested using standardized methods against a range of antibiotics commonly used to treat anaerobic infections. Susceptibility was determined using NCCLS criteria. The change in susceptibility trends between this study and earlier studies was measured by comparing the geometric mean of the MIC. A total of 364 anaerobes were tested. Penicillin had poor activity against Bacteroides spp., Prevotella spp., Eubacterium spp., Clostridium tertium and Veillonella spp. In general, Fusobacterium spp., Bacteroides ureolyticus, Propionibacterium spp., Clostridium perfringens and anaerobic streptococci isolates, with the exception of Peptostreptococcus anaerobius, were penicillin susceptible. Amoxicillin/clavulanate showed good activity against most anaerobes, but resistance was seen with Bacteroides fragilis group and P. anaerobius isolates. Cefoxitin was more active than cefotetan, particularly against non-B. fragilis species, Eubacterium spp. and P. anaerobius. Meropenem and imipenem showed good activity against all anaerobes, with only 2 and 4% of Bacteroides spp., respectively, showing resistance. With the exception of Propionibacterium acnes isolates, which are predictably resistant, metronidazole was active against all anaerobes tested. There has been little change in susceptibility since 1997. Metronidazole, cefoxitin, piperacillin/tazobactam and amoxicillin/clavulanate remain good empirical choices when anaerobes are expected in our setting. No clinically relevant changes in susceptibility over time were found.

Antimicrobial susceptibility of anaerobic bacteria in Australia.

The susceptibilities of 900 clinical isolates of anaerobic bacteria to 14 antimicrobial agents were determined by an agar dilution technique. Chloramphenicol, imipenem and metronidazole were found to be active against virtually all of the strains; only a single Bacteroides fragilis isolate was resistant to both imipenem and metronidazole. The addition of clavulanic acid to amoxycillin and ticarcillin potentiated the activities of these agents against all anaerobes including members of the B. fragilis group. Ampicillin/sulbactam and clindamycin were the next most active agents, 91 and 89% of isolates respectively being susceptible. Seventy-three per cent of the bacteria tested were susceptible to cefoxitin and 65% to cefotetan, with the MICs of almost 50% of the isolates clustering between 16 and 32 mg/L. There was also clustering around the breakpoint (64 mg/L) of piperacillin. Azithromycin exhibited poor activity against the B. fragilis group; only 18% of isolates were susceptible to < or = 4 mg/L. However, 92% of non-B. fragilis Bacteroides group strains were susceptible to this agent. We conclude that imipenem, metronidazole, chloramphenicol, ticarcillin/clavulanate, co-amoxiclav and, to a lesser extent, ampicillin/sulbactam are suitable as empirical therapy for infections caused by anaerobic bacteria.

Recent experience with antimicrobial susceptibility of anaerobic bacteria : Edson RS, Rosenblatt JE, Lee DT, et al. Mayo Clin Proc 57:737, 1982

Recent experience with antimicrobial susceptibility of anaerobic bacteria : Edson RS, Rosenblatt JE, Lee DT, et al. Mayo Clin Proc 57:737, 1982

The antimicrobial susceptibility of anaerobic bacteria in a London teaching hospital.

Journal Article The antimicrobial susceptibility of anaerobic bacteria in a London teaching hospital Get access Ian Phillips, Ian Phillips Department of Microbiology, St Thomas's Hospital Medical SchoolLondon, England Search for other works by this author on: Oxford Academic PubMed Google Scholar Christine Warren, Christine Warren Department of Microbiology, St Thomas's Hospital Medical SchoolLondon, England Search for other works by this author on: Oxford Academic PubMed Google Scholar Elisabeth Taylor, Elisabeth Taylor Department of Microbiology, St Thomas's Hospital Medical SchoolLondon, England Search for other works by this author on: Oxford Academic PubMed Google Scholar Roger Timewell, Roger Timewell Department of Microbiology, St Thomas's Hospital Medical SchoolLondon, England Search for other works by this author on: Oxford Academic PubMed Google Scholar Susannah Eykyn Susannah Eykyn Department of Microbiology, St Thomas's Hospital Medical SchoolLondon, England Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Antimicrobial Chemotherapy, Volume 8, Issue suppl_D, 1981, Pages 17–26, https://doi.org/10.1093/jac/8.suppl_D.17 Published: 01 August 1981

Antimicrobial susceptibility of anaerobic bacteria isolated from clinical specimens by using an agar dilution procedure

An agar dilution procedure was used to evaluate the antimicrobial susceptibility of 2,126 anaerobic bacteria isolated from a broad spectrum of properly obtained clinical specimens. Significant numbers ofBacteroides species,Fusobacterium species, anaerobic Gram-positive cocci, and anaerobic nonsporeforming Gram-positive bacilli would not grow on Wilkins-Chalgren agar used in the procedure. The failure to obtain growth from theBacteroides species was of special concern since these organisms generally show a higher degree of resistance to antibiotics than the other anaerobic bacteria, which failed to grow or grew poorly on that medium. When compared to other investigations, the data indicated an emerging resistnace to clindamy a forB. thetaiotaomicron andB. distasonis. IndividualClostridium species showed a wide divergence in susceptibility.

Broth-dilution method for determining the antibiotic susceptibility of anaerobic bacteria.

A broth-dilution method for performing antimicrobial susceptibility tests on anaerobic bacteria has been proposed. The medium used in the test was Schaedler broth, with incubation in a glove box with an atmosphere of 5% CO(2), 10% H(2), and 85% N(2), or in the GasPak system. Minimal inhibitory concentrations for selected antibiotics were determined, under these conditions, by using a conventional twofold dilution scheme for the antibiotics and a "categorization three-tube method" in which two or three clinically significant concentrations of each antibiotic were used. Minimal inhibitory concentrations obtained by both methods were very similar. The categorization method could be used routinely to test the antimicrobial susceptibility of anaerobic bacteria.

Effects of medium and inoculum on antimicrobial susceptibility of anaerobic bacteria.

Inhibitory activities of twofold dilutions of penicillin, chloramphenicol, tetracycline, and clindamycin were determined against two different inocula (104, 105) in parallel in supplemented brain-heart infusion agar, Brucella agar, and Mueller-Hinton agar. Incubation was in an anaerobic chamber for 48 hours. To compare MIC values of each antibiotic by medium and inoculum size, ![Graphic][1] was determined and averages were calculated. In general, MIC values in brain-heart infusion agar were almost twice as great as those in Mueller-Hinton agar; in general, MIC values in Mueller-Hinton agar with inocula of 105 were almost twice those with 104. Results with Brucella agar generally were intermediate between results with the other media. These differences, however, were not sufficiently great to alter the clinical interpretation of the results in terms of resistance or susceptibility of the strains tested. [1]: /embed/inline-graphic-1.gif