Fusobacteria behaving badly: Masquerading strains of strictly anaerobic Escherichiacoli misidentified due to the deletion of the hemB gene.

Three strictly anaerobic strains of Escherichia coli were misidentified as Fusobacterium mortiferum, due to a deletion of the hemB gene which is involved in anaerobic respiration. An unusual antimicrobial susceptibility pattern sparked the further diagnostic strategies that eventually identified these strains as true anaerobic E. coli This phenomenon is more common than appreciated and can have an impact on clinical practice including persistent and relapsing infections.

In vitro activity of TD-1792, a multivalent glycopeptide-cephalosporin antibiotic, against 377 strains of anaerobic bacteria and 34 strains of Corynebacterium species.

TD-1792 is a multivalent glycopeptide-cephalosporin heterodimer antibiotic with potent activity against Gram-positive bacteria. We tested TD-1792 against 377 anaerobes and 34 strains of Corynebacterium species. Against nearly all Gram-positive strains, TD-1792 had an MIC90 of 0.25 µg/ml and was typically 3 to 7 dilutions more active than vancomycin and daptomycin.

Re-assessment of phenotypic identifications of Bacteroides putredinis to Alistipes species using molecular methods.

Alistipes (previously Bacteroides) are strictly anaerobic gram-negative rods that resemble the Bacteroides fragilis group in that most species are bile-resistant and indole-positive; however, they are only weakly saccharolytic and most species produce light brown pigment only on laked rabbit blood agar. In this retrospective study, we re-identified 18 organisms previously identified phenotypically as "Bacteroides putredinis-like", but that did not produce pigment on routine media. The strains were identified with 16S rDNA sequencing and pigment production was evaluated on several different culture media. Only 12/18 strains had molecular identifications of Alistipes species, while the remaining strains phylogenetically resembled Butyricimonas and Odoribacter spp. Pigment production was not a reliable test for those Alistipes strains that are described as pigment producers.

Bactericidal activity of telavancin, vancomycin and metronidazole against Clostridium difficile.

We compared the time-kill activities of telavancin, vancomycin and metronidazole at concentrations of 2 times, 4 times, and 8 times their respective MICs against five Clostridium difficile strains including REA type BI, using inocula that contained predominantly either vegetative cells or spores. Telavancin MICs (0.125-0.25 microg/ml) were 2-8-fold lower than those of vancomycin. Telavancin was bacteriostatic, reducing the inoculum by 1-2.5 log(10) after 24 h. No major differences occurred with the different inoculum forms or the REA types. Although telavancin MICs were 2-8 times lower than vancomycin, both demonstrated similar bacteriostatic activity against C. difficile while metronidazole was bactericidal.

Comparative in vitro activity of REP3123 against Clostridium difficile and other anaerobic intestinal bacteria.

OBJECTIVES: The aim of this study was to determine the anaerobic spectrum of activity of REP3123, a novel diaryldiamine that inhibits bacterial methionyl-tRNA synthetases in Gram-positive bacteria. METHODS: Fifty recent clinical isolates of Clostridium difficile from patients diagnosed with C. difficile infection and 223 other intestinal normal flora anaerobes were tested for their susceptibility to REP3123 and four or five comparator agents by the agar dilution method using supplemented Brucella agar with 5% laked sheep blood. RESULTS: All strains of C. difficile were inhibited by 0.5-1 mg/L REP3123, including those resistant to moxifloxacin and clindamycin. REP3123 lacked activity against many normal flora anaerobes in the gut, including Clostridium ramosum, bifidobacteria, lactobacilli of the Lactobacillus casei-rhamnosus-plantarum group and Gram-negative anaerobes. CONCLUSIONS: REP3123 demonstrated good potency against C. difficile, but limited activity against many other intestinal anaerobic species, thus, in theory, maintaining the colonization resistance barrier.

Virulence characteristics of community-associated Staphylococcus aureus and in vitro activities of moxifloxacin alone and in combination against community-associated and healthcare-associated meticillin-resistant and -susceptible S. aureus.

The increasing prevalence of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) poses a challenge for antimicrobial therapy of skin and soft tissue infections (SSTIs). To determine whether another antimicrobial agent might enhance the activity of moxifloxacin against CA-MRSA, this study analysed its activity alone and in chequerboard combination with doxycycline, rifampicin, clindamycin, trimethoprim, sulfamethoxazole/trimethoprim (SXT) and vancomycin against recent SSTI clinical isolates, and also characterized the isolates for Panton-Valentine leukocidin (PVL), agr groups, staphylococcal cassette chromosome mec (SSCmec) types and delta-haemolysin production. For comparison, 25 strains of outpatient meticillin-susceptible S. aureus (MSSA), 24 strains of healthcare-associated (HA)-MRSA and six historical strains of vancomycin-intermediate S. aureus (VISA) were included. It was found that 21/25 CA-MRSA strains tested were PVL-positive, SSCmec type 4 and agr type 1, whilst 4/25 were PVL-negative, SSCmec type 2 and agr type 2. Two of the agr type 2 strains were negative for delta-haemolysin but all other strains were positive. Moxifloxacin MIC50/90 values (microg ml(-1)) were 1/8 for CA-MRSA, 4/32 for HA-MRSA and 0.5 to

In vitro activity of azithromycin and nine comparator agents against 296 strains of oral anaerobes and 31 strains of Eikenella corrodens.

At this time in the USA there are no antimicrobials with specific indications for oral infections, and many of those currently used have limited efficacy against oral anaerobic strains. We tested the activity of azithromycin against a broad range of anaerobic oral pathogens and, at pH 8, found it to be effective against 98% of strains, including all fusobacteria and beta-lactamase-producing strains of Prevotella spp. All strains of Eikenella corrodens were also susceptible to azithromycin but resistant to erythromycin, clindamycin, metronidazole and cefalexin. Other comparator agents were penicillin, amoxicillin/clavulanic acid, tetracycline, levofloxacin and ciprofloxacin. Minimum inhibitory concentrations obtained on agar adjusted to pH 8 were generally one dilution lower than those obtained on agar at pH 7.

Activity of Ceftaroline against Aerobic Gram-Positive and Gram-Negative Pathogens: Effect of Test Method Variability.

Ceftaroline is a new cephalosporin with bactericidal activity against methicillin-resistant S. aureus (MRSA) as well as gram-negative pathogens. Variations of in vitro test conditions were found to affect ceftaroline activity, with 5% NaCl inhibiting growth and/or reducing the minimum inhibitory concentrations (MICs) for E. coli, K. pneumoniae, M. catarrhalis, H. influenzae, and streptococci, while an inoculum of 10(6) CFU/mL raised MICs of some E. coli, K. pneumoniae, and M. catarrhalis strains.

In vitro activities of doripenem and six comparator drugs against 423 aerobic and anaerobic bacterial isolates from infected diabetic foot wounds.

Against 182 anaerobe and 241 aerobe strains obtained from diabetic foot infections, doripenem was the most active carbapenem against Pseudomonas aeruginosa (MIC(90), 2 microg/ml), more active than imipenem against Proteus mirabilis, and ertapenem was more active against Escherichia coli and Klebsiella spp. The MIC(50) and MIC(90) values were < or =0.125 microg/ml for methicillin-sensitive Staphylococcus aureus and all streptococci and 0.25/1 for Bacteroides fragilis.

Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. isolated from human clinical infections.

One hundred eight isolates were previously identified in our laboratory as Clostridium clostridioforme by colonial and cellular morphology, as well as biochemical tests. Recent studies have indicated that there are actually three different species in this C. clostridioforme group: C. hathewayi, C. bolteae, and C. clostridioforme. Our isolates were reexamined using biochemical and enzymatic tests and molecular methods. Forty-six isolates were reidentified as C. hathewayi, 34 as C. bolteae, five as C. clostridioforme, and one as C. symbiosum. Twenty-two strains were identified only to the genus level by 16S rRNA gene sequencing, and although they are microscopically and morphologically indistinguishable from the above-mentioned three species, they are phenotypically different and only 96 to 98% similar by gene sequencing. Twenty of these 22 strains were indole positive and formed two novel species. We propose Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. as names for these new species. They are differentiated from each other by results for raffinose, rhamnose, alpha-galactosidase, and beta-galactosidase: positive, negative, positive, and positive, respectively, for the former species and negative, positive, negative, and negative, respectively, for the latter species. The type strain of C. aldenense is RMA 9741 (ATCC BAA-1318; CCUG 52204), and the type strain of C. citroniae is RMA 16102 (ATCC BAA-1317; CCUG 52203).

Synergistes group organisms of human origin.

The bacterial division Synergistes represents a poorly characterized phylotype of which only a few isolates have been cultured, primarily from natural environments. Recent detection of Synergistes-like sequence types in periodontal pockets and caries lesions of humans prompted us to search the R. M. Alden culture collection (Santa Monica, Calif.) for biochemically unidentifiable, slow-growing, obligately anaerobic gram-negative bacilli. Here we report on five clinical isolates cultured from peritoneal fluid and two isolates from soft-tissue infections that together constitute three separate evolutionary lineages within the phylogenetic radiation of the division Synergistes. One of these clusters was formed by the peritoneal isolates and had an 85% similarity to Synergistes jonesii, the first described Synergistes species, which was isolated from the rumen of a goat. The isolates from soft-tissue infections, on the other hand, formed two distinct lineages moderately related to each other with a similarity of approximately 78%. In addition, by using a newly designed 16S rRNA gene-based PCR assay with intended target specificity for Synergistes, we found that the dominant phylotype from a fecal sample was nearly identical to that of the strains obtained from peritonitis. Conversely, sequence types detected in periodontal pockets formed a separate cluster that shared a similarity of only 80% with the soft-tissue isolates. These findings suggest a high diversity of medically important Synergistes clades that apparently are unique to individual ecological niches in the human body. In conclusion, we now have available the first characterized human isolates of the division Synergistes which are colonizing, and probably infecting, several sites in the human body.

In vitro activity of moxifloxacin against 923 anaerobes isolated from human intra-abdominal infections.

The in vitro activity of moxifloxacin against 923 recent anaerobic isolates obtained from pretreatment cultures in patients with complicated intra-abdominal infections was studied using the CLSI M11-A-6 agar dilution method. Moxifloxacin was active against 87% (96 of 110) Bacteroides fragilis strains at < or = 1 microg/ml and 87% (79 of 90) B. thetaiotaomicron strains at < or = 2 microg/ml. Species variation was seen, with B. uniformis, B. vulgatus, Clostridium clostridioforme, and C. symbiosum being least susceptible and accounting for most of the resistant isolates; excluding the aforementioned four resistant species, 86% (303 of 363) of Bacteroides species isolates and 94% (417 of 450) of all other genera and species were susceptible to < or = 2 microg/ml of moxifloxacin. Overall, moxifloxacin was active against 763 of 923 (83%) of strains at < or = 2 microg/ml, supporting its use as a monotherapy for some community-acquired intra-abdominal infections.

Comparative in vitro activities of retapamulin (SB-275833) against 141 clinical isolates of Propionibacterium spp., including 117 P. acnes isolates.

Using the NCCLS agar dilution method, we studied the in vitro activity of retapamulin (SB-275833) against 141 clinical isolates of Propionibacterium species, including seven multiresistant strains, and found retapamulin to be the most active agent among those tested with MICs of < or = 1 microg/ml against all isolates.

In vitro activities of daptomycin, vancomycin, and penicillin against Clostridium difficile, C. perfringens, Finegoldia magna, and Propionibacterium acnes.

Daptomycin has in vitro activity against gram-positive anaerobic bacteria, although limited numbers of species have been tested. We studied the in vitro activities of daptomycin, vancomycin, and penicillin against more than 100 strains each of Clostridium difficile, C. perfringens, Finegoldia magna, and Propionibacterium acnes. Daptomycin Etest MICs and results from time-kill studies were determined for selected strains. For 392 of 421 strains (93%), daptomycin was inhibitory at < or =1 microg/ml, including 15 of 16 strains of C. difficile with elevated linezolid MICs of 8 and 16 microg/ml, all 32 strains with moxifloxacin MICs of > or =4 microg/ml, and all 16 strains resistant to clindamycin. Daptomycin MICs were also < or =1 microg/ml for all 16 F. magna strains resistant to clindamycin and all 32 strains resistant to tetracycline. Only one strain, a C. perfringens strain, had a MIC of >2 microg/ml to daptomycin. Eighty-five and 92.5% of the Etest MICs were within 1 dilution of the agar dilution method for all drugs at 24 and 48 h, respectively. In time-kill studies, a C. difficile strain was inhibited by both daptomycin and vancomycin at 1, 2, 4, 8, and 24 h; colony counts were decreased by 2.3 to 2.9 log at 24 h. Vancomycin was not bactericidal for C. perfringens; however, daptomycin showed bactericidal activity as early as 1 h at four and eight times the MIC and at 2 and 4 h at two and four times the MIC.

In vitro activities of dalbavancin and 12 other agents against 329 aerobic and anaerobic gram-positive isolates recovered from diabetic foot infections.

Tests of dalbavancin's in vitro activity against 209 aerobic and 120 anaerobic isolates from pretreatment diabetic foot infections showed an MIC(90) of < or =0.125 microg/ml against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), and 120 anaerobes (Clostridium perfringens, other clostridia, Peptoniphilus asaccharolyticus, Finegoldia magna, and Anaerococcus prevotii), compared to respective MIC(90)s for MSSA and MRSA of 0.5 and 1 microg/ml for vancomycin, 4 and 4 microg/ml for linezolid, 0.5 and 0.5 microg/ml for daptomycin, and 0.25 and >8 microg/ml for clindamycin.

In vitro activity of ceftobiprole against aerobic and anaerobic strains isolated from diabetic foot infections.

Against 443 aerobic and anaerobic bacteria isolated from diabetic foot infections, ceftobiprole MICs (microg/ml) at which 90% of the isolates tested were inhibited were as follows: methicillin-resistant Staphylococcus aureus, 1; methicillin-susceptible S. aureus and Staphylococcus lugdunensis, 0.5; Anaerococcus prevotii, 0.125; Finegoldia magna, 0.5; Peptoniphilus asaccharolyticus, 1; Peptostreptococcus anaerobius, 4; Escherichia coli and Enterobacter species, 0.125; Klebsiella species, 2; and Pseudomonas aeruginosa, 8.

Comparative in vitro susceptibilities of 396 unusual anaerobic strains to tigecycline and eight other antimicrobial agents.

Tigecycline was tested against 396 strains of lesser-known anaerobic species encountered in human infections. It was active against all gram-positive strains and 228 of 232 gram-negative anaerobes at < or =1 microg/ml. One strain of Prevotella oralis was nonsusceptible at 8 microg/ml.

In vitro activity of 11 antibiotics against 74 anaerobes isolated from pediatric intra-abdominal infections.

The in vitro activity of 11 antimicrobials was tested against 74 recent anaerobic isolates obtained from pretreatment cultures in pediatric patients with complicated intra-abdominal infections using the CLSI M11-A-6 agar dilution method. Carbapenems, beta-lactamase inhibitor combinations and metronidazole retained good activity, while all Bacteroides fragilis group species produced beta-lactamase and were penicillin resistant and 43% were either intermediately susceptible or resistant to clindamycin. Cefoxitin had moderate activity against B. fragilis but poor activity against Bacteroides thetaiotaomicron and other B. fragilis group isolates.

Biochemical differentiation and comparison of Desulfovibrio species and other phenotypically similar genera.

Seventeen human clinical isolates representing four species of Desulfovibrio were characterized using 16S rRNA gene sequences and tests for catalase, indole, nitrate, bile, urease, formate-fumarate stimulation, desulfoviridin, motility, and hydrogen sulfide production, plus susceptibility to antimicrobial agents. Eighty additional strains representing 10 phenotypically similar genera (Bilophila, Selenomonas, Capnocytophaga, Campylobacter, Bacteroides, Sutterella, Anaerobiospirillum, Dialister, Veillonella, and Mobiluncus) were included for comparison. All Desulfovibrio species produced H2S and were desulfoviridin positive, and all Desulfovibrio species except D. piger were motile. The four Desulfovibrio species could be distinguished from each other using tests for catalase, indole, nitrate, urease, and growth on bile, with the following results (positive [+], negative [-], growth [G], and no growth [NG]): for D. piger, -, -, -, -, and G, respectively; for D. fairfieldensis, +, -, +, -, and G, respectively; for D. desulfuricans, -, -, +, +, and NG, respectively; and for D. vulgaris, -, +, -, -, and G, respectively. Resistance to the 10-microg colistin disk separated the Desulfovibrio species from most of the other genera, which were usually susceptible. These simple tests were useful for characterizing the Desulfovibrio species and differentiating them from other phenotypically similar genera.

Broth microdilution and disk diffusion tests for susceptibility testing of Pasteurella species isolated from human clinical specimens.

Broth microdilution and disk diffusion susceptibility testing were performed on 73 strains of Pasteurella species isolated from human infections and on five American Type Culture Collection strains of Pasteurella species. Both methods appear reliable for testing susceptibilities of Pasteurella species.