Kerin L. Tyrrell

16S-23S rDNA internal transcribed spacer sequences for analysis of the phylogenetic relationships among species of the genus Fusobacterium.

The 16S-23S rDNA internal transcribed spacer (ITS) regions of all currently defined Fusobacterium species and related taxa such as Leptotrichia buccalis, Sebaldella termitidis and Streptobacillus moniliformans, were analysed to examine inter- and intraspecies as well as subspecies relationships. For the ITS-amplification, a new eubacterial universal primer pair was designed and used. The majority of the Fusobacterium strains, along with L. buccalis showed one major, and two to three weaker, distinct bands (short and long versions) with lengths of 800-830 bp and 1000-1100 bp. Nevertheless, six other patterns were also found within the genus Fusobacterium, demonstrating its heterogeneity. The ITS region was sequenced and found to consist both of conserved motifs, which functioned as a framework for alignment, and of variable sites, which provided high phylogenetic resolution. Analyses of the ITS-DNA sequences and ITS relative length (short version) allowed species and subspecies differentiation in most cases. The results confirmed the strikingly distant relationship between Fusobacterium prausnitzii and the genus Fusobacterium. Fusobacterium nucleatum subspecies, along with Fusobacterium naviforme, Fusobacterium simiae and Fusobacterium periodonticum, formed a cluster with an inherently high potential for diversification. Other clusters were formed by Fusobacterium necrophorum subspecies with Fusobacterium gonidaformans and by Fusobacterium varium with Fusobacterium mortiferum and Fusobacterium ulcerans. Fusobacterium russii as well as Fusobacterium perfoetens formed separate branches. Fusobacterium necrophorum subspp. necrophorum and funduliforme on the one hand, and Fusobacterium varium and Fusobacterium mortiferum on the other, were found to be very similar, even at the high-resolution ITS level.

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.

Pharmacokinetics and Pharmacodynamics of Linezolid in Obese Patients with Cellulitis

BACKGROUND: Linezolid is an oxazolidinone antimicrobial with excellent oral bioavailability and tissue penetration and is active against multidrug-resistant skin/soft tissue pathogens. OBJECTIVE: To study the pharmacokinetics and antibacterial activity of linezolid against selective skin/soft tissue pathogens in obese patients. METHODS: We obtained multiple serum samples from 7 obese patients (>50% over their calculated ideal body weight) receiving oral linezolid 600 mg every 12 hours for treatment of cellulitis. Following a minimum of 3 doses, serum concentrations of linezolid were measured in each subject prior to (trough) and 1 and 6 hours after a dose. These samples were then tested against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) (linezolid minimum inhibitory concentrations [MICs] 1.0, 2.0, 4.0 μg/mL) and one strain each of vancomycin-resistant Enterococcus faecium (VRE) (MIC 2.0 μg/mL), Bacteroides fragilis (MIC 2.0 μg/mL), and Peptostreptococcus magnus (MIC 1.0 μg/mL). Serum inhibitory titers (SITs) and bactericidal titers (SBTs) were measured at each time point, and the median activity for these 7 patients was calculated. RESULTS: Mean linezolid serum concentrations were 4.2, 12.3, and 7.2 μg/mL at these respective time points. Median SITs for 12 hours (100% of the dosing interval) were observed against each organism with the exception of the least susceptible strain of MRSA (MIC 4.0 μg/mL); serum inhibitory activity was observed only at the one-hour time point against this isolate. Furthermore, prolonged (⩾6 h) median SBTs were observed against one isolate of MRSA (MIC 1.0 μg/mL) as well as the strain of VRE and P. magnus. CONCLUSIONS: Serum concentrations of oral linezolid in this patient population were diminished compared with those of healthy volunteers, but still provided prolonged serum inhibitory activity against common pathogens associated with skin/soft tissue infections. One treatment concern would be an obese patient receiving oral linezolid who was infected with a less susceptible (MIC ⩾4.0 μg/mL) strain of S. aureus. Bactericidal activity was also observed against selective pathogens.

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.

Periodontal Bacteria in Rabbit Mandibular and Maxillary Abscesses

ABSTRACT Despite the high incidence of odontogenic abscesses in pet rabbits, published data on the bacteriology of these infections are lacking, and clinical cultures are often ambiguous, making antibiotic choices difficult. In order to define the bacteriology of these infections, 12 rabbit mandibular and maxillary abscesses were cultured aerobically and anaerobically. All specimens yielded pathogenic bacteria, including Fusobacterium nucleatum, Prevotella heparinolytica, Prevotella spp., Peptostreptococcus micros, Streptococcus milleri group, Actinomyces israelii, and Arcanobacterium haemolyticum. These organisms are consistent with the characterized bacteriology of periodontal disease in human and other mammalian studies. The isolates were tested against 10 antimicrobial agents commonly used to treat rabbits; 100% of the strains tested were susceptible to clindamycin, 96% were susceptible to penicillin and ceftriaxone, 54% were susceptible to ciprofloxacin, and only 7% were susceptible to trimethoprim-sulfamethoxazole.

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.