Yumi A. Warren

In Vitro Activities of the New Semisynthetic Glycopeptide Telavancin (TD-6424), Vancomycin, Daptomycin, Linezolid, and Four Comparator Agents against Anaerobic Gram-Positive Species and Corynebacterium spp.

ABSTRACT Telavancin is a new semisynthetic glycopeptide anti-infective with multiple mechanisms of action, including inhibition of bacterial membrane phospholipid synthesis and inhibition of bacterial cell wall synthesis. We determined the in vitro activities of telavancin, vancomycin, daptomycin, linezolid, quinupristin-dalfopristin, imipenem, piperacillin-tazobactam, and ampicillin against 268 clinical isolates of anaerobic gram-positive organisms and 31 Corynebacterium strains using agar dilution methods according to National Committee for Clinical Laboratory Standards procedures. Plates with daptomycin were supplemented with Ca2+ to 50 mg/liter. The MICs at which 90% of isolates tested were inhibited (MIC90s) for telavancin and vancomycin were as follows: Actinomyces spp. (n = 45), 0.25 and 1 μg/ml, respectively; Clostridium difficile (n = 14), 0.25 and 1μ g/ml, respectively; Clostridium ramosum (n= 16), 1 and 4 μg/ml, respectively; Clostridium innocuum (n = 15), 4 and 16 μg/ml, respectively; Clostridium clostridioforme (n= 15), 8 and 1 μg/ml, respectively; Eubacterium group (n = 33), 0.25 and 2μ g/ml, respectively; Lactobacillus spp. (n= 26), 0.5 and 4 μg/ml, respectively; Propionibacterium spp. (n = 34), 0.125 and 0.5 μg/ml, respectively; Peptostreptococcus spp. (n = 52), 0.125 and 0.5 μg/ml, respectively; and Corynebacterium spp. (n = 31), 0.03 and 0.5 μg/ml, respectively. The activity of TD-6424 was similar to that of quinupristin-dalfopristin for most strains except C. clostridioforme and Lactobacillus casei, where quinupristin-dalfopristin was three- to fivefold more active. Daptomycin had decreased activity (MIC > 4 μg/ml) against 14 strains of Actinomyces spp. and all C. ramosum, Eubacterium lentum, and Lactobacillus plantarum strains. Linezolid showed decreased activity (MIC > 4 μg/ml) against C. ramosum, two strains of C. difficile, and 15 strains of Lactobacillus spp. Imipenem and piperacillin-tazobactam were active against >98% of strains. The MICs of ampicillin for eight Clostridium spp. and three strains of L. casei were >1 μg/ml. The MIC90 of TD-6424 for all strains tested was ≤2 μg/ml. TD-6424 has potential for use against infections with gram-positive anaerobes and deserves further clinical evaluation.

Comparative In Vitro Activities of Ertapenem (MK-0826) against 1,001 Anaerobes Isolated from Human Intra-Abdominal Infections

ABSTRACT By using an agar dilution method, the comparative in vitro activities of ertapenem (MK-0826) were studied against 1,001 anaerobes isolated from human intra-abdominal infections in 17 countries worldwide. MK-0826 was uniformly active against all isolates, including all Bacteroides fragilis group species isolates, with the exception of 12 of 61 (20%) strains of Bilophila wadsworthia, 3 strains of lactobacilli, and 1 isolate ofAcidaminococcus fermentans. Geographical variation in activity was not observed.

In Vitro Activities of Daptomycin, Vancomycin, Quinupristin- Dalfopristin, Linezolid, and Five Other Antimicrobials against 307 Gram-Positive Anaerobic and 31 Corynebacterium Clinical Isolates

ABSTRACT The activities of daptomycin, a cyclic lipopeptide, and eight other agents were determined against 338 strains of gram-positive anaerobic bacteria and corynebacteria by the NCCLS reference agar dilution method with supplemented brucella agar for the anaerobes and Mueller-Hinton agar for the corynebacteria. The daptomycin MICs determined on Ca2+-supplemented (50 mg/liter) brucella agar plates were one- to fourfold lower than those determined in unsupplemented media. Daptomycin was highly active (MICs, ≤2 μg/ml) against many strains including 36 of 37 peptostreptococci, 37 of 48 isolates of the Eubacterium group, and all strains of Propionibacterium spp., Clostridium perfringens, Clostridium difficile, and other Clostridium spp. It was fourfold or greater more active than vancomycin against Clostridium innocuum and 16 of 34 strains of vancomycin-resistant lactobacilli. Three strains of C. difficile for which quinupristin-dalfopristin and linezolid MICs were >8 μg/ml were inhibited by <1 μg of daptomycin per ml. Daptomycin MICs were ≥4 μg/ml for most strains of Clostridium clostridioforme, Clostridium paraputrificum, Clostridium tertium, and Clostridium ramosum; the isolates were generally more resistant to other antimicrobials. Daptomycin was two- to fourfold less active against Actinomyces spp. than vancomycin, quinupristin-dalfopristin, or linezolid. Twenty-nine of 31 strains of Corynebacterium spp., including Corynebacterium jeikeium, Corynebacterium amycolatum, and Corynebacterium pseudodiphtheriticum, were inhibited by ≤0.25 μg of daptomycin per ml. For two strains of “Corynebacterium aquaticum,” 8 μg of daptomycin per ml was required for inhibition. Daptomycin demonstrated very good activities against a broad range of gram-positive organisms including vancomycin-resistant C. innocuum and lactobacillus strains and quinupristin-dalfopristin- and linezolid-resistant C. difficile strains.

Comparative In Vitro Activities of GAR-936 against Aerobic and Anaerobic Animal and Human Bite Wound Pathogens

ABSTRACT GAR-936 is a new semisynthetic glycylcycline with a broad antibacterial spectrum, including tetracycline-resistant strains. The in vitro activities of GAR-936, minocycline, doxycycline, tetracycline, moxifloxacin, penicillin G, and erythromycin were determined by agar dilution methods against 268 aerobic and 148 anaerobic strains of bacteria (including Pasteurella, Eikenella,Moraxella, Bergeyella, Neisseria, EF-4, Bacteroides, Prevotella,Porphyromonas, Fusobacterium,Staphylococcus, Streptococcus,Enterococcus, Corynebacterium,Propionibacterium, Peptostreptococcus, andActinomyces) isolated from infected human and animal bite wounds in humans, including strains resistant to commonly used antimicrobials. GAR-936 was very active, with an MIC at which 90% of the strains are inhibited (MIC90) of ≤0.25 μg/ml, against all aerobic gram-positive and -negative strains, including tetracycline-resistant strains of Enterococcus,Streptococcus, and coagulase-negative staphylococci, except for Eikenella corrodens (MIC90, ≤4 μg/ml). GAR-936 was also very active against all anaerobic species, including tetracycline-, doxycycline-, and minocycline-resistant strains ofPrevotella spp., Porphyromonas spp.,Bacteroides tectum, and Peptostreptococcusspp., with an MIC90 of ≤0.25 μg/ml. Erythromycin- and moxifloxacin-resistant fusobacteria were susceptible to GAR-936, with an MIC90 of 0.06 μg/ml.

In Vitro Activity of Moxifloxacin against 923 Anaerobes Isolated from Human Intra-Abdominal Infections

ABSTRACT 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 ≤1 μg/ml and 87% (79 of 90) B. thetaiotaomicron strains at ≤2 μg/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 ≤2 μg/ml of moxifloxacin. Overall, moxifloxacin was active against 763 of 923 (83%) of strains at ≤2 μg/ml, supporting its use as a monotherapy for some community-acquired intra-abdominal infections.

Biochemical Differentiation and Comparison of Desulfovibrio Species and Other Phenotypically Similar Genera

ABSTRACT 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-μg 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.

Synergistes Group Organisms of Human Origin

ABSTRACT 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 Ceftobiprole against Aerobic and Anaerobic Strains Isolated from Diabetic Foot Infections

ABSTRACT Against 443 aerobic and anaerobic bacteria isolated from diabetic foot infections, ceftobiprole MICs (μg/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.

Clostridium aldenense sp. nov. and Clostridium citroniae sp. nov. Isolated from Human Clinical Infections

ABSTRACT 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, α-galactosidase, and β-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).

In Vitro Activities of Dalbavancin and 12 Other Agents against 329 Aerobic and Anaerobic Gram-Positive Isolates Recovered from Diabetic Foot Infections

ABSTRACT Tests of dalbavancins in vitro activity against 209 aerobic and 120 anaerobic isolates from pretreatment diabetic foot infections showed an MIC90 of ≤0.125 μg/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 MIC90s for MSSA and MRSA of 0.5 and 1 μg/ml for vancomycin, 4 and 4 μg/ml for linezolid, 0.5 and 0.5 μg/ml for daptomycin, and 0.25 and >8 μg/ml for clindamycin.