Antibiotic Resistance Among Anaerobes: What Does it Mean?

Antibiotic resistance among anaerobes is increasing, with significant resistance to clindamycin, cephalosporins, cephamycins, and penicillins noted at community hospitals and major medical centers. A total of 615 anaerobes isolated from various Chicago area hospitals in 1996 were tested against 13 antibiotics, and the resistance patterns compared with similar data from 1991. For the Bacteroides fragilis group anaerobes, the most effective antibiotics were the β-lactam/β-lactamase inhibitor combination agents, carbapenems, trovafloxacin and metronidazole. High levels of resistance to clindamycin, piperacillin, cefoxitin and ceftizoxime were seen 1996. For non- B. fragilis group anaerobes, resistance was mush lower, and was notable only in Clostridium spp. (clindamycin and cephamycins) and Prevotella spp. (clindamycin and piperacillin). Despite the prevalence of antibiotic resistance among anaerobes, the frequency of antimicrobial susceptibility testing of anaerobes is declining. There are a number of factors that account for this decline, including a general reduction in funding of hospital clinical laboratories, a concomitant loss of expertise at these institutions, a lack of automated testing for anaerobes, and a failure to consider resistance as important to clinicians. The case for increased susceptibility testing is built upon the changing patterns of resistance such as those reported in this paper, the identification and transfer of genetic determinants corresponding to antibiotic resistance, as well as the correlation of resistance and clinical outcome.     

Surveillance and trends of antimicrobial resistance among clinical isolates of anaerobes in Kuwait hospitals from 2002 to 2007

The susceptibility trends for all anaerobes processed by the Anaerobe Reference Laboratory against various antibiotics were determined by using data for 2557 isolates referred by all government hospitals in Kuwait from 2002 to 2007. MIC were determined for the following anti-anaerobic antibiotics: amoxicillin–clavulanic acid, clindamycin, imipenem, meropenem, metronidazole, penicillin, piperacillin, piperacillin–tazobactam and vancomycin (for Gram-positive anaerobes only), using E-test method. The commonest isolates were Bacteroides fragilis (36.8%), followed by Peptostreptococcus spp. (21.9%), Bacteroides ovatus (15.5%) and Prevotella bivia (12.1%). In addition, Prevotella oralis and other Bacteroides spp. represented 8.5% and 8.1% of total number of isolates, respectively. Resistance rate varied among the antimicrobial agents and the species tested. The β-lactams, with the exception of penicillin, were the most active drugs. Piperacillin–tazobactam was the only antimicrobial agent to which all the isolates were uniformly susceptible. Imipenem and metronidazole were highly active with resistance rate of only <5% recorded against most isolates. However, 42.8, 55.8 and 9.3% of Clostridium difficile isolates were resistant to imipenem, clindamycin and meropenem, respectively. It is noteworthy that from 2002 to 2007, there was a gradual increase in resistance rates to clindamycin, amoxicillin–clavulanic acid and piperacillin among B. fragilis. Periodic surveillance of antibiotic resistance among the anaerobic bacteria is recommended as a guide to empiric antibiotic use and formulation of guideline for appropriate choice of antimicrobial therapy in anaerobic infections.     

Use of the Etest method for antimicrobial susceptibility testing of obligate anaerobes]

The aim of this study was to evaluate Etest usefulness for antimicrobial susceptibility testing of obligate anaerobes and to compare the activity of five antibacterial drugs against clinical strains of anaerobes. One hundred strains of obligate anaerobes were tested: 2 reference strains (B. fragilis ATCC 25285 and B. thetaiotaomicron ATCC 29741) and 98 clinical strains isolated from patients of the Infant Jesus Clinical Hospital--Center for Trauma Treatment in Warsaw during the last three years (1997-1999). Strains of seven genera of obligate nonsporeforming anaerobes (Bacteroides, Prevotella, Porphyromonas, Fusobacterium, Peptostreptococcus, Propionibacterium and Actinomyces) and strains of two sporeforming species (C. perfringens and C. difficile) were examined. The MIC values were determined by the gradient diffusion method Etest (AB BIODISK, Sweden). Wilkins-Chalgren solid medium supplemented with 5% of sheep blood was used. Test plates were incubated at 35 degrees C for 48 hours in glove-box (85% N2, 10% H2, 5% CO2). The MIC values for each strain and antimicrobial agent, and the MIC ranges for bacteria of the same species were established. Ten strains resistant to clindamycin, ten resistant to piperacillin, and ten resistant to imipenem were detected. Seven strains were resistant to metronidazole and two strains to piperacillin combined with tazobactam. Tazobactam restored the susceptibility of eight strains to piperacillin. Obtained results confirm that Etest method is useful for antimicrobial susceptibility testing of obligate anaerobes. Older (clindamycin and metronidazole) and newer (piperacillin, piperacillin/tazobactam and imipenem) antimicrobial agents revealed high and comparable activity against clinical strains of obligate anaerobes. The percentage of strains susceptible to tested antimicrobials was > or = 90. These antimicrobials may be still useful in the empiric treatment of infections caused by medically important anaerobes.     

Anaerobic Bacterial Flora of Intra-abdominal Infections and their Antimicrobial Susceptibility Pattern in Kuwait

Clinical samples obtained from 200 patients with intra-abdominal infections were investigated for the presence of anaerobic bacteria. The majority of samples were from patients with appendicitis (108, 54%) followed by peritoneal abscess/peritonitis (37, 18.5%). A total of 153 anaerobes were isolated from 83 culture positive specimens with an isolation rate of 1.8 per sample. Ninety (59%) yielded Bacteroides fragilis group and B. fragilis stricto sensu accounted for half of them. Other isolates were 36 (23.5%) Prevotella species and 15 (9.8%)Peptostreptococcus micros . The susceptibility of the 153 isolates against eight antibiotics was determined by the E-test. All the isolates were susceptible to metronidazole, MIC₉₀s varying between 1–2 μg/mL. ThePrevotella spp., Peptostreptococcus spp., Fusobacterium spp. and Porphyromonas spp. were all susceptible to clindamycin (MIC₉₀s=0.25–2 μg/mL respectively), imipenem (MIC₉₀s=0.12–0.5μg/mL respectively) and meropenem (MIC₉₀=0.25 μg/mL each). About 25% of the B. fragilis group were resistant to clindamycin with MIC more than 256 μg/mL. Piperacillin-tazobactam also exhibited excellent in vitro activity against all the isolates (MIC₉₀=0.25 μg/mL).     

The role of anaerobic bacteria in chronic suppurative otitis media in children: Implications for medical therapy

This review describes the microbiology, diagnosis and medical management of chronic suppurative otitis media (CSOM) in children highlighting the role of anaerobic bacteria. In studies that employed adequate method for recovery of anaerobic bacteria polymicrobial aerobic and anaerobic flora was isolated from over half of the children with CSOM. The predominant aerobic isolates were Staphylococcus aureus and Pseudomonas aeruginosa and the most frequently isolated anaerobic organisms were Peptostreptococcus, Fusobacterium spp. and pigmented Prevotella and Porphyromonas spp. Several studies illustrated the efficacy of anti-infective agents effective against anaerobic bacteria in the treatment of CSOM. The medical therapy of CSOM should be directed at the eradication of the pathogenic aerobic and anaerobic organisms.     

Identification and susceptibility to antimicrobial agents of strictly anaerobic bacteria isolated from hospitalized patients

The aim of this study was to identify anaerobic strains isolated in 2001 from clinical specimens obtained from patients of Warsaw hospital and to evaluate a susceptibility of these strains to antimicrobial agents. In 2001 two hundred and twenty five clinical strains of obligate anaerobes were cultured, which were identified in the automatic ATB system (bioMérieux, France) using biochemical tests API 20 A. Drug-susceptibility of strains was determined also in ATB system with the use of ATB ANA strips. C. difficile strains were isolated on selective CCCA medium. Toxins A/B of C. difficile directly in stool specimens were detected by means of ELISA test (TechLab, USA). Fifty four strains of Gram-negative anaerobes (B. fragilis strains dominated) and 171 strains of Gram-positive anaerobes (the greatest number of strains belonged to genus Peptostreptococcus) were cultured from clinical specimens. In the cases of antibiotic-associated diarrhea 28 C. difficile strains were isolated and C. difficile toxins A/B were detected in 39 stool samples. The most active in vitro antimicrobials against Gram-negative anaerobes were metronidazole, imipenem, ticarcillin combined with clavulanic acid and piperacillin with tazobactam. Gram-positive, clinical strains of anaerobes were the most susceptible in vitro to beta-lactam antibiotics combined with beta-lactamase inhibitors (amoxicillin/clavulanate, piperacillin/tazobactam, ticarcillin/clavulanate) and imipenem.     

Systematics and evolution of ruminal species of the genus Prevotella

Bacterial species of the genusPrevotella represent a numerically dominant microbial population in the rumen of cattle. They belong to the phylogenetic divisionCytophaga-Flexibacter-Bacteroides (CFB) which is a large group of ecologically diverse bacteria with only a few shared traits. The phylogenetic descent from a common ancestor seems to be unquestionable, however, as judged from the small subunit ribosomal RNA analysis. Only 4 ruminalPrevotella species have been described to date, even though the sequence analysis of directly retrieved 16S rRNA genes indicates a large genetic diversity within this group of rumen bacteria. The closest relatives of ruminalPrevotella spp. are not surprisingly other species of the genusPrevotella, typically inhabiting the gastrointestinal tract, oral cavity and genital areas of other animals and man. The previous phylogenetic analysis showed that species of the genusPrevotella can be split into two groups or superclusters, the “ruminal” and the “non-ruminal prevotellas”. One of 4 currently described ruminalPrevotella spp.,i.e. P. albensis, has been placed outside the supercluster containing ruminalPrevotella spp. and within the supercluster containing the non-ruminalPrevotella spp. However, the number of available small subunit rRNA sequences from this species represents only a fraction of all known ruminalPrevotella sequences.     

A severely symptomatic case of anaerobic chronic bacterial prostatitis successfully resolved with moxifloxacin therapy

It has been demonstrated that patients showing symptoms of chronic bacterial prostatitis but culture-negative prostate-specific specimens can benefit from administration of antibacterial agents. This suggests that organisms that are not isolated in the routine practice may be responsible for prostate infection in an undefined fraction of subjects. Anaerobic bacteria have been proposed to play a pathogenic role in CBP, on the basis of studies describing clinical remission after eradication of pathogens like Peptostreptococcus spp or Bacterioides spp from prostatic secretions of symptomatic patients, or the significant association between prostatic infection by anaerobes and the presence of inflammation markers in prostatic secretions.In this paper, we report in detail a case of severely symptomatic chronic prostatitis in a patient with evidence of infection by Peptostreptococcus. We also report for the first time that treatment with the 3rd generation fluoroquinolone moxifloxacin was successful in eradicating the pathogen and in causing dramatic resolution of signs and symptoms of chronic bacterial prostatitis.The strict association between eradication of Peptostreptococcus and the rapid disappearance of clinical signs/symptoms points to a causative role of this anaerobe in the chronic bacterial prostatitis case described in this report.     

Characteristic of clinical strains of gram-negative obligate anaerobes

The aim of the study was to assess prevalence and antibiotic susceptibility profiles ofGram-negative strictly anaerobic bacteria isolated from clinical specimens taken from hospitalized patients in 2005-2006. Biochemical identification and antibiotic susceptibility were done in an automated system ATB Expression (bioMerieux sa). From 12262 specimens examined 867 strains of obligate anaerobes were isolated. Gram-negative strictly anaerobic bacteria were cultured in number of 138 strains (15,9%). All cultures were performed on Columbia agar and Schaedler agar media (bioMerieux sa) supplemented with 5% sheep blood and incubated at 37 degrees C for 48-120 h in 85% N2, 10% H2, 5% CO2. Most frequently isolated was Bacteroides spp. (41,3%). For this group beta-lactamase activity was evaluated by using nitrocefin disc test (Cefinase BBL, Becton Dickinson and Co., Cockeysville, MD, USA). Production of ESBLs was detected with the use of two disc diffusion methods: the double-disc synergy test (DDST) according to Jarlier et al. and the diagnostic disc (DD) test according to Appleton. ESBLs were produced by 5,3% strains of Bacteroides spp. For all Bacteroides spp. strains MIC values were determined by gradient diffusion method Etest (AB BIODISK, Sweden). ESBLs and MIC were performed on Wilkins-Chalgren solid medium supplemented with 5% sheep blood (Difco Lab., USA) and all plates were incubated at 35 degrees C for 48 hours in 85% N2, 10% H2, 5% CO2. Most Gram-negative obligate anaerobes isolated from clinical specimens are still susceptible to imipenem (100%), metronidazole (99,3%) and beta-lactam antibiotics with beta-lactamase inhibitors: piperacillin/tazobactam (99,3%), ticarcillin/clavulanate (99.3%), amoxicillin/clavulanate (97.8%).     

Susceptibility to antibiotics of Enterobacter spp. rods isolated from urine

Enterobacter spp. rods are opportunistic microorganisms which cause of urinary tract infections. The aim of this study was the evaluation of the susceptibility to antimicrobial agents antibiotics of Enterobacter spp. rods isolated from urine. The study was carried 50 of Enterobacter spp strains isolated in the Clinical Microbiology Department of dr. A. Jurasz University Hospital. Antibiotic susceptibility was tested by disk diffusion method. All of strains were susceptible to imipenem and meropenem. There was 87,5% of strains sensitive to doripenem, 79,2% to ertapenem, 54,0% to piperacillin/tazobactam and 50,0% to cephepime. The relatively high percentage (62,0%) of Enterobacter spp. was sensitive to fluoroquinolones. Extended spectrum beta-lactamases were produced by 24 (48,0%) strains.     

Antimicrobial resistance among urinary tract infection (UTI) isolates in Europe: results from the SENTRY Antimicrobial Surveillance Program 1997

The SENTRY Antimicrobial Surveillance Program was established to monitor the occurrence and antimicrobial susceptibility of bacterial pathogens via an international network of sentinel hospitals. Twenty European hospitals referred a total of 887 urinary tract infection (UTI) isolates to the European SENTRY reference laboratory during the period October–December 1997. Ninety percent of the referred species were represented by Escherichia coli (52%), Enterococcus spp. (12%), Klebsiella spp. (7%), Proteus spp. (7%), Pseudomonas aeruginosa (7%), and Enterobacter spp. (5%). The susceptibility of E. coli isolates to penicillins was less than 60%, while almost all of the isolates were susceptible to piperacillin/tazobactam (98% susceptibility), cephalosporins (98%), and carbapenems (100%). Amikacin was the best aminoglycoside (99.8% susceptibility). The susceptibility to quinolones was only 88–89%, with highest levels of resistance observed for isolates from Portugal, Italy, England, The Netherlands, and some centers in France, Spain, and Poland. The susceptibility of Klebsiella spp. to the newer generations of cephalosporins was 82–95% and to the carbapenems 100%. Amikacin was again the best aminoglycoside (94% susceptibility). The susceptibility of Enterobacter spp. to any ß-lactam antibiotic was poor, except for the carbapenems (100% susceptibility) and cefepime (90% susceptibility), while the susceptibility to aminoglycosides was 80–89%. Proteus spp. showed complete susceptibility to cefepime, ceftriaxone, the carbapenems, and piperacillin/tazobactam, while the susceptibility of P. aeruginosa isolates was poor, with best results for the carbapenems (susceptibility 89%), piperacillin/tazobactam (susceptibility 84%), and amikacin and ticarcillin (susceptibility to both 80%). Enterococcus spp. showed the highest susceptibility to vancomycin (98%), teicoplanin (98%), and ampicillin (94%).     

Household environmental microbiota influences early-life eczema development

Exposure to a diverse microbial environment during pregnancy and early postnatal period is important in determining predisposition towards allergy. However, the effect of environmental microbiota exposure during preconception, pregnancy and postnatal life on development of allergy in the child has not been investigated so far. In the S-PRESTO (Singapore PREconception Study of long Term maternal and child Outcomes) cohort, we collected house dust during all three critical window periods and analysed microbial composition using 16S rRNA gene sequencing. At 6 and 18 months, the child was assessed for eczema by clinicians. In the eczema group, household environmental microbiota was characterized by presence of human-associated bacteria Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium at all time points, suggesting their possible contributions to regulating host immunity and increasing the susceptibility to eczema. In the home environment of the control group, putative protective effect of an environmental microbe Planomicrobium (Planococcaceae family) was observed to be significantly higher than that in the eczema group. Network correlation analysis demonstrated inverse relationships between beneficial Planomicrobium and human-associated bacteria (Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium). Exposure to natural environmental microbiota may be beneficial to modulate shed human-associated microbiota in an indoor environment.     

Trends in antibiotic resistance in Prevotella species from patients of the University Hospital of Maxillofacial Surgery,Sofia, Bulgaria,in 2003–2009

Head-and-neck infections often involve anaerobes such as Prevotella species. Aim of the present study was to assess the evolution and the factors associated with resistance in Prevotella species to penicillin, clindamycin, metronidazole, tetracycline and β-lactams/β-lactamase inhibitors (BL/BLIs). In total, 192 Prevotella strains, isolated from patients with oral and head-and-neck infections, were evaluated. Common isolates were Prevotella intermedia and Prevotella melaninogenica within the pigmented species as well as Prevotella oris and Prevotella oralis group within the non-pigmented species. Overall resistance was 43.2% for penicillin, 10.9% for clindamycin, 0% for metronidazole. Nonsusceptibility to tetracycline was 29.1% without significant differences in resistance rates between pigmented and other species. Penicillin resistant strains were β-lactamase positive. From 2003–2004 to 2007–2009, penicillin resistance rates increased about four-fold (from 15.4% to 60.6%). Clindamycin resistance did not show evolution, whereas tetracycline nonsusceptibility decreased from 43.3% in 2003–2004 to 20.7% in 2007–2009. Except for one (0.5%) P. oralis strain with intermediate susceptibility to BL/BLIs, the other strains were susceptible to the agents. In conclusion, in Prevotella strains from patients with head-and-neck infections, the resistance rate to penicillin increased, that to clindamycin remained stable and the nonsusceptibility rate to tetracycline decreased during the period. Activity against >99% of Prevotella strains was observed with metronidazole and BL/BLIs. The penicillin resistance and tetracycline nonsusceptibility were associated with the year of study, national antibiotic consumption and possibly with previous treatment (for tetracycline). The evolution of penicillin resistance in Prevotella strains was highly dynamic.     

Inhibition of uropathogens by lactic acid bacteria isolated from dairy foods and cow’s intestine in western Nigeria

A total of 96 lactic acid bacteria (LAB) were isolated from African indigenous fermented products and cow’s intestines to study their inhibitory capability against multi-drug-resistant uropathogens. Escherichia coli accounted for approximately 45% of isolated uropathogens, followed by Staphylococcus spp. (20%). The Gram negative uropathogens were highly resistant to quinolones, co-trimoxazole, teicoplanin and some β-lactams, while the Staphylococcus spp. showed high resistance to aminoglycosides, β-lactams and macrolides. Twenty-four LAB isolates were selected based on their antimicrobial activity against two uropathogenic Staphylococcus aureus strains and bacteriocin production. LAB strains showing antimicrobial activity were grouped into smaller groups through amplified ribosomal DNA restriction analysis (ARDRA). Representative strains were identified as Weissella spp., Enterococcus faecium, Lactococcus lactis and Lactobacillus brevis through sequencing of 16S rDNA. The Weissella spp. and L. brevis strains demonstrated remarkable inhibitory activity against seven strains of Gram negative uropathogens. Two strains of L. lactis produced a bacteriocin-like inhibitory substance active against Lactobacillus sakei. In this study, an unusual high rate of co-trimoxazole, quinolones and macrolides resistance among uropathogens from south west Nigeria was discovered. Based on their sensitivity to Weissella spp., there is a potential for using these LAB as a natural approach for the protection against the uropathogens assayed.     

Anaerobic bacteria colonizing the lower airways in lung cancer patients

Anaerobes comprise most of the endogenous oropharyngeal microflora, and can cause infections of airways in lung cancer patients who are at high risk for respiratory tract infections. The aim of this study was to determine the frequency and species diversity of anaerobes in specimens from the lower airways of lung cancer patients. Sensitivity of the isolates to conventional antimicrobial agents used in anaerobe therapy was assessed. Respiratory secretions obtained by bronchoscopy from 30 lung cancer patients were cultured onto Wilkins-Chalgren agar in anaerobic conditions at 37°C for 72-96 hours. The isolates were identified using microtest Api 20A. The minimal inhibitory concentrations for penicillin G, amoxicillin/clavulanate, piperacillin/tazobactam, cefoxitin, imipenem, clindamycin, and metronidazole were determined by E-test. A total of 47 isolates of anaerobic bacteria were detected in 22 (73.3%) specimens. More than one species of anaerobe was found in 16 (53.3%) samples. The most frequently isolated were Actinomyces spp. and Peptostreptococcus spp., followed by Eubacterium lentum, Veillonella parvula, Prevotella spp., Bacteroides spp., Lactobacillus jensenii. Among antibiotics used in the study amoxicillin/clavulanate and imipenem were the most active in vitro (0% and 2% resistant strains, respectively). The highest resistance rate was found for penicillin G and metronidazole (36% and 38% resistant strains, respectively). The results obtained confirm the need to conduct analyses of anaerobic microflora colonizing the lower respiratory tract in patients with lung cancer to monitor potential etiologic factors of airways infections, as well as to propose efficient, empirical therapy.     

Synergistic effect of polyethylenimine plus piperacillin/tazobactam on clinicalPseudomonas aeruginosa isolates resistant to piperacillin/tazobactam

We investigated thein vitro susceptibility of piperacillin/tazobactam in association with polyethylenimine (PEI), a synthetic polycation polymer, against 24 clinical isolates ofPsedomonas aeruginosa resistant to piperacillin/tazobactam. The strains were isolated from patients with respiratory tract infections. MIC of piperacillin/tazobactam was determined by agar dilution method in accordance with NCCLS methodology. An inoculum of 10⁴ CFU/spot with or without PEI (250 nM final concentration) was used. Killing curves were performed for 3 piperacillin/tazobactam resistant strains chosen for their different range of MIC values to piperacillin/tazobactam (128, 256 and 512 mg/L, respectively). Analyses were performed in duplicate using a concentration of antibiotic of 16 mg/L. The addition of PEI (250 nM) increased the susceptibility of piperacillin/tazobactam (from 8 to 32 folds) in all the strains tested. Moreover, in all the strains tested piperacillin/tazobactam in association with PEI showed a bactericidal activity before 6 h. Intrinsic resistance ofP. aeruginosa affects susceptibility to penicillins and is believed to entail broad spectrum impermeability. Different theories suggest that some degree of structure or organization exists in the periplasm ofP. aeruginosa and that this modulates both the level of intrinsic, impermeability-determined resistance expressed by a strain and the efficiency with which the β-lactamase can contact and destroy the incoming β-lactamase molecules. The explanation of this behaviour could be that PEI determines an increased permeability of the outer membrane ofP. aeruginosa; tazobactam inhibits β-lactamase allowing the antibacterial activity of piperacillin. In conclusion our data suggest that PEI can be expected to act as a vehicle for experimental drug delivery into cells, and as a potentiating agent for antibacterial agents that are normally excluded by Gram-negative bacteria.     

In vitro Activity of Moxifloxacin Against 179 Strains of Anaerobic Bacteria Found in Pulmonary Infections

The activity of moxifloxacin (BAY 12-8039), a new 8-methoxyquinolone, was determined using the NCCLS-approved Wadsworth brucella laked blood agar method and compared to the activities of metronidazole, penicillin G, piperacillin/tazobactam and trovafloxacin. Breakpoints used to define susceptible and resistant categories were, respectively: ≤ 8 and ≥ 32 μg/mL for metronidazole, ≤ 2 and ≥ 8 μg/mL for moxifloxacin and trovafloxacin, ≤ 0.5 and ≥ 2 μg/mL for penicillin G and ≤ 32 and ≥128 μg/mL for piperacillin/tazobactam. A total of 179 anaerobic isolates from pulmonary infections were tested. Piperacillin/tazobactam was the most active antimicrobial, inhibiting 99% of strains at the susceptible breakpoint. Ninety-seven percent of these isolates were susceptible to moxifloxacin; 96% to trovafloxacin, 89% to metronidazole and 43% to penicillin G. Geometric mean moxifloxacin MIC values forBacteroides fragilis and the B. fragilis group were 0.5 and 0.8 μg/mL, respectively. Eighty-eight percent of B. fragilis and 100% of other B. fragilis group species were susceptible to both moxifloxacin and trovafloxacin. All of the strains of B. fragilis and most of the other B. fragilis group species were resistant to penicillin G. At least 99% of other Bacteroides species, Prevotella, and Fusobacterium strains were susceptible to moxifloxacin, metronidazole, piperacillin/tazobactam and trovafloxacin (88% were susceptible to trovafloxacin at 2 μg/mL and all were susceptible at 4 μg/mL). The strains of Clostridium difficile andClostridium ramosum found in these specimens were both resistant to penicillin G but susceptible to the other agents. All strains of Peptostreptococcus species were susceptible to all of the agents except penicillin G. Activities of the agents against non-spore-forming Gram-positive rods at the intermediate breakpoint were, respectively, moxifloxacin-100%, metronidazole-49%, penicillin G-86%, piperacillin/tazobactam-100%, and trovafloxacin-97%. The promising in vitro activity of moxifloxacin against anaerobic pulmonary isolates warrants further investigation, including clinical correlation studies.     

Standardization of antimicrobial disc susceptibility test for anaerobic bacteria.

Both agar diluiton and agar diffusion tests with 8 clinically useful or potentially useful antimicrobial agents were performed with 74 strains of Bacteroides fragilis. Correlation of results obtained by the two methods and applicability of the single disc test to the measurement of antimicrobial susceptibility of anaerobes were analyzed. Prediction of susceptibility, intermediate susceptibility, and resistance of anaerobic bacteria to antimicrobial agents, based on the measurement of inhibition zone diameter, appeared to be satisfactory generally.     

Drug resistance of 100 clinical strains of Enterococcus spp

The aim of this study was to evaluate the drug susceptibility of 100 Enterococcus spp. strains isolated from patients hospitalized in State Clinical Hospital No 1 in Warsaw. All strains were identified (API 20 STREP) and their susceptibility to antibiotics was tested (ATB STREP) in automatic ATB system. Additionally, PYRase activity, beta-lactamase production (in nitrocefin test), MICs for vancomycin and teicoplanin (E test), HLAR--high level aminoglycoside resistance and susceptibility to vancomycin, teicoplanin, piperacillin and piperacillin/tazobactam (disc diffusion method) were determined. E. faecalis ATCC 29212 was used as the control strain. Fifty E. faecalis, 45 E. faecium, 2 E. casseliflavus, 2 E. durans and 1 E. avium strain were cultured. All strains were PYRase-positive and beta-lactamase-negative. Ten isolates demonstrated intermediate susceptibility to vancomycin (6--E. faecalis and 4--E. faecium). One E. faecalis strain was intermediately susceptible to both glycopeptides. One E. casseliflavus strain showed low-level resistance to vancomycin, but this strain was susceptible to teicoplanin--phenotype Van C. HLAR strains were found among 31 E. faecalis and 40 E. faecium strains. 48 E. faecalis strains were susceptible to piperacillin and 49 to piperacillin/tazobactam. Whereas, 41 E. faecium were resistant to both these drugs. Thirty six per cent of isolates were resistant to penicillin and ampicillin, 73% to erythromycin, 87% to tetracycline, 89% to lincomycin and 56% to nitrofurantoin. Some discrepancies were noticed between the results of different methods applied for susceptibility testing--ATB system, E test and disc diffusion. These discrepancies concerned HLAR detection and susceptibility to glycopeptides determination. The best methods were: disc-diffusion for HLAR detection and E test for determination of resistance to vancomycin and teicoplanin. Increasing resistance to antimicrobial agents is observed in clinical Enterococcus spp. isolates cultured in our laboratory, especially in E. faecium strains. It is necessary to control the dissemination of multiresistant Enterococcus spp. strains in hospital wards.     

Enrichment of Propionibacterium in paddy soil by addition of various organic substances

Enrichment of Propionibacterium and production of propionic acid in paddy soil after addition of glucose, casamino acids, or Na-lactate, respectively, were investigated. Only in the case of Na-lactate, both enrichment of Propionibacterium (74% of total anaerobes isolated) and production of large amounts of propionic acid were observed. These results suggest that lactate may support the growth of Propionibacterium in paddy soil.