Activity of a novel carbapenem, doripenem, against anaerobic pathogens

Doripenem, a synthetic 1-beta-methyl carbapenem, has a broad-spectrum of activity against almost all species of anaerobic bacteria, including all Bacteroides fragilis group species, most with MIC(90) results at <or=1 microg/mL (with the exception of Sutterella wadsworthensis). Against Clostridium difficile strains, it has a narrow range of inhibitory concentrations (1-4 microg/mL) that "may be achievable in the colon", potentially resulting in lower disease rates. It has been shown to be active in vitro against strains isolated from a variety of clinical infections, including bacteremias, diabetic foot and other soft tissues infections and in intra-abdominal and pelvic sites. In addition, a study of a pyometrium animal model of mixed infections noted a better microbiologic response than with imipenem. Two phase 3 multinational clinical trials of complicated mixed aerobic/anaerobic intra-abdominal infections noted "noninferiority" of doripenem when compared with meropenem, but in vitro against the anaerobes, it was "more potent than meropenem, ertapenem, ... and similar to imipenem". Doripenem activity against anaerobes seems comparable with the other extant carbapenems. Although resistance among anaerobic bacteria to this agent is possible, it remains relatively rare.

The non-value of preoperative and intraoperative cultures in predicting the bacteriology of subsequent wound infection in patients undergoing major head and neck cancer surgery

A prospective study of patients undergoing major head and neck cancer surgery was undertaken to define the value of preoperative and intraoperative cultures in identifying the patient at "high risk" of wound infection and in predicting the bacteriology of wound infection. One or two days before surgery, the skin of the operative site on the neck, the oropharynx and anterior nares were swabbed. an intraoperative wound culture was obtained after the pharyngeal defect was closed and the wound irrigated with water. All cultures were processed for aerobes in the Anaerobic Bacteriology Research Laboratory at Wadsworth Hospital Center. Wound infections developed in 10 of 31 patients who received cefazolin prophylactically and 21 of 25 patients who received no perioperative antibiotics. Fifty-five percent of infected patients and 68% of noninfected patients demonstrated potential pathogens preoperatively. A potential pathogen isolated preoperatively or intraoperatively was subsequently recovered from 35% of infected wounds. The majority of infected wound cultures grew one or more additional pathogens. A poor correlation was also noted between preoperative nasal Staphylococcus aureus isolation and subsequent recovery from wound infections. We conclude that preoperative and intraoperative aerobic wound cultures are not predictive of the "high risk" patient or of the bacteriology of subsequent wound infection in major head and neck cancer surgery.

Pasteurella multocida subsp. multocida and P. multocida subsp. septica differentiation by PCR fingerprinting and alpha-glucosidase activity

Pasteurella multocida is composed of three subspecies that are often differentiated by fermentation of sorbitol and dulcitol. We studied 35 dulcitol-negative P. multocida isolates from infected dog and cat bite wounds, 16 of which yielded weak and/or conflicting fermentation reactions in Andrades sorbitol, thus making it difficult to distinguish between the two dulcitol-negative subspecies of P. multocida, i.e., P. multocida subsp. multocida and P. multocida subsp. septica. All isolates and two control strains were further analyzed using a PCR fingerprinting technique with a single primer (M13 core) and assessed for alpha-glucosidase (alpha-Glu) activity. Although the PCR fingerprint patterns and alpha-Glu activity did not correlate well with the sorbitol fermentation reactions, they did correlate well with each other. All strains identified as P. multocida subsp. septica were positive for alpha-Glu activity and exhibited the group I PCR fingerprint profile. All strains categorized as P. multocida subsp. multocida displayed either the group II or group III PCR fingerprint profile; 9 of 11 of these isolates were alpha-Glu negative. These data suggest that both PCR fingerprinting and alpha-Glu activity provide reliable means for differentiating P. multocida subsp. multocida from P. multocida subsp. septica, particularly in strains that produce weak and/or discrepant sorbitol fermentation reactions.

In vitro activity of oritavancin (LY333328), vancomycin, clindamycin, and metronidazole against Clostridium perfringens, Propionibacterium acnes, and anaerobic Gram-positive cocci

Using an agar dilution method, we determined the in vitro activity of oritavancin, vancomycin, clindamycin and metronidazole against 114 unique clinical isolates of Gram-positive anaerobes. MIC(90)s (microg/mL) for oritavancin were as follows: Clostridium perfringens 1.0, Propionibacterium acnes 0.25, Peptostreptococcus anaerobius 0.25, Peptoniphilus asaccharolyticus 0.5, Finegoldia magna 0.25, Micromonas. micros 0.25, and Anaerococcus prevotii 0.25. On a weight basis, oritavancin is slightly more active than vancomycin against the strains tested. The oritavancin MICs are comparable to those previously reported against staphylococci and enterococci. Oritavancin shows excellent potential for treatment of infections containing Gram-positive anaerobes such as these.

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.

Molecular characterization and antimicrobial susceptibilities of extra-intestinal Clostridium difficile isolates

Amongst 25 extra-intestinal clinical isolates of Clostridium difficile, A(+)B(+) (72%) and A(-)B(+) (4%) toxigenic phenotypes, as well as the non-toxigenic phenotype (A(-)B(-)) (24%), were identified. The A(-)B(-) isolates did not express toxin, yet carried part of the tcdA and tcdB gene and are of a previously unreported toxinotype. Six A(+)B(+) isolates also carried binary toxin genes. Resistance to erythromycin (20%), clindamycin (48%), tetracycline (16%), moxifloxacin (16%) and imipenem (11%) occurred but with no apparent correlation to phenotype. None of the strains was resistant to vancomycin or metronidazole. Imipenem-resistance decreased by EDTA, but susceptibility to meropenem suggests the presence of an imipenem specific metalloenzyme.

Impact of Surotomycin on the Gut Microbiota of Healthy Volunteers in a Phase 1 Clinical Trial

Clostridium difficile-associated diarrhea has been associated with disruption of the normal intestinal microbiota, particularly theBacteroides fragilisgroup andPrevotellaspecies. Surotomycin is a bactericidal cyclic lipopeptide in development for treatment ofClostridium difficile-associated diarrhea that has selective and potent activity againstC. difficileand other Gram-positive bacteria and a minimal impact on intestinal Gram-negative organisms. The impacts of ascending doses of surotomycin on major organism groups in the gut microbiota of healthy volunteers were evaluated during a randomized, double-blind, placebo-controlled, multiple-dose phase 1 study. Thirty volunteers were randomized into 3 cohorts, using a 4:1 ratio, to receive 250 mg, 500 mg, or 1,000 mg of surotomycin, or placebo, twice daily for 14 days. Stool samples collected at baseline (days 0 and 1) and at the end of treatment (days 13 to 15) were cultured quantitatively. TheB. fragilisgroup, theBacteroides/Prevotellagroup, andEnterobacteriaceaewere also quantified by quantitative real-time PCR. Baseline and end-of-treatment stool samples showed 1- to 2-log10CFU/g reductions in total bacterial counts for most volunteers. Various decreases in clostridial,Lactobacillus-Bifidobacteriumgroup, and enterococcus-streptococcus group counts occurred while patients were receiving surotomycin, whereas the enterobacteria and theB. fragilisgroup persisted at the end of treatment. There was no change in enterococcus MICs of surotomycin, nor was vancomycin-resistantEnterococcusdetected after exposure. Surotomycin at doses of up to 1,000 mg twice daily had only modest disruptive effects on the gut microbiota. The potential sparing of the gut microbiota by surotomycin may decrease the risk of disease recurrence.

Cefoxitin for treatment of infections due to anaerobic bacteria

Twenty-seven patients with 29 infections due to anaerobic or mixed anaerobic-aerobic bacteria were treated with cefoxitin. From the 27 patients 99 isolates of anaerobic bacteria and 70 isolates of aerobic bacteria were recovered. Twelve pleuropulmonary infections, 12 soft tissue infections, three bone infections, and two intraabdominal infections were treated. Twenty-six of the 29 infections were completely or partially eradicated; the remaining three infections were unchanged. One-third of the patients experienced phlebitis; in two instances severe phlebitis caused discontinuation of therapy. In this study cefoxitin appeared to be an effective single agent for the therapy of infections due to specific anaerobic bacteria or to a mixed flora of anaerobic and aerobic bacteria.

Comparative in vitro activities of ertapenem against bacterial pathogens from patients with acute pelvic infection

This study compared the in vitro activities of ertapenem, ceftriaxone, co-amoxiclav, ciprofloxacin and piperacillin-tazobactam against 314 aerobic bacteria and of ertapenem, piperacillin-tazobactam, cefoxitin, ceftriaxone, chloramphenicol, ticarcillin-clavulanate, ampicillin-sulbactam, clindamycin and metronidazole against 500 anaerobic bacteria from 212 patients with acute pelvic infection. Antimicrobial susceptibilities were determined by broth microdilution (aerobes) or agar dilution (anaerobes), following NCCLS guidelines. The most common isolates were Enterobacteriaceae and Peptostreptococcus spp. Ertapenem was the most active drug tested against Enterobacteriaceae (100% susceptible) and anaerobes (99.8% susceptible); the least active agents were co-amoxiclav (79% of Enterobacteriaceae susceptible) and ceftriaxone (85.9% of anaerobes susceptible). All agents tested had excellent activity against beta-haemolytic streptococci and methicillin-susceptible Staphylococcus aureus.

Comparative in vitro activities of ABT-773 against 362 clinical isolates of anaerobic bacteria

The activity of ABT-773, a novel ketolide antibiotic, against clinical isolates of anaerobic bacteria was determined and compared to the activities of other antimicrobial agents. MICs at which 90% of isolates were inhibited (MIC(90)s) were </=0.06 microg/ml for Actinomyces spp., Clostridium perfringens, Peptostreptococcus spp., Propionibacterium spp., and Porphyromonas spp. The MIC(50)s and MIC(90)s were </=0.06 and >32 microg/ml, respectively, for Eubacterium spp., Lactobacillus spp., Clostridium difficile, and Clostridium ramosum. The MIC(90) for Bilophila wadsworthia, Bacteroides ureolyticus, and Campylobacter gracilis was 1 microg/ml, and that for Prevotella bivia and other Prevotella spp. was 0.5 microg/ml. The MIC(90) for Fusobacterium nucleatum was 8 microg/ml, and that for Fusobacterium mortiferum and Fusobacterium varium was >32 microg/ml. The MIC(90)s for the Bacteroides fragilis group were as follows: for B. fragilis, 8 microg/ml; for Bacteroides thetaiotaomicron, Bacteroides ovatus, Bacteroides distasonis, and Bacteroides uniformis, >32 microg/ml; and for Bacteroides vulgatus, 4 microg/ml. Telithromycin MICs for the B. fragilis group were usually 1 to 2 dilutions higher than ABT-773 MICs. For all strains, ABT-773 was more active than erythromycin by 4 or more dilutions, and for some strains this drug was more active than clindamycin.

Comparative in vitro activities of ertapenem (MK-0826) against 469 less frequently identified anaerobes isolated from human infections

We studied the in vitro activity of ertapenem against 469 less frequently identified anaerobes from 11 genera and 52 species isolated from human infections. Ertapenem was uniformly active against 460 of 469 (98%) strains at concentrations of < or = 4 microg/ml. Only 4 of 14 Clostridium difficile, 1 of 11 Clostridium innocuum, and 4 of 6 Lactobacillus sp. strains required ertapenem concentrations of > or = 8 microg/ml for inhibition.

In vitro activities of telithromycin and 10 oral agents against aerobic and anaerobic pathogens isolated from antral puncture specimens from patients with sinusitis

A study of the comparative in vitro activity of telithromycin, a new ketolide, against 155 aerobic and 171 anaerobic antral sinus puncture isolates showed it to be active against a broad range of sinus pathogens. All pneumococci, including erythromycin-resistant strains, were susceptible to telithromycin at < or = 0.5 microg/ml; all Haemophilus influenzae and Eikenella corrodens strains were inhibited by < or = 4 microg of telithromycin/ml; all Moraxella spp. and beta-lactamase-producing Prevotella species strains were inhibited by < or = 0.25 and 0.5 microg of telithromycin/ml, respectively. Among all anaerobes tested, 94% (160 of 171 strains) were susceptible to < or = 4 microg of telithromycin/ml; however, 8 of 17 (47%) Fusobacterium strains, 2 Veillonella strains, and 1 Peptostreptococcus micros strain required > 4 microg of telithromycin/ml for inhibition. Telithromycin may offer a therapeutic alternative for sinus infections, including those due to erythromycin-resistant pneumococci.

Effect of inoculum size on in vitro activity of norfloxacin against fecal anaerobic bacteria. Rationale for selective decontamination of the digestive tract

Previous studies have shown that anaerobic bacteria are susceptible to norfloxacin at the levels attained in the feces. Conversely, studies in laboratory animals and neutropenic humans using norfloxacin for selective decontamination of the digestive tract have shown that norfloxacin markedly reduces the aerobic enteric flora without reducing fecal anaerobic flora. In an effort to resolve this paradox, the effect of a 10(9) colony-forming units (cfu)/ml inoculum, which is more reflective of actual fecal counts than the standard 10(5) cfu/ml inoculum, on the activity of norfloxacin against two fecal Escherichia coli isolates and 16 fecal anaerobic isolates was studied. The results showed a marked inoculum effect at 10(9) cfu/ml for most anaerobic isolates but not for the E. coli strains tested. At 256 micrograms/ml, all E. coli were killed while the anaerobic bacteria maintained colony counts greater than or equal to 10(9) cfu/ml. Hence, the lack of anaerobic activity (minimal inhibitory concentration greater than or equal to 512 micrograms/ml) at higher fecal inocula might explain the utility of norfloxacin in selective decontamination of the bowel.

16S-23S rRNA gene internal transcribed spacer sequences for analysis of the phylogenetic relationships among species of the genus Porphyromonas

The 16S-23S rRNA gene internal transcribed spacer (ITS) regions of 11 reference strains of Porphyromonas species, together with Bacteroides distasonis and Tannerella forsythensis, were analysed to examine interspecies relationships. Compared with the phylogenetic tree generated using 16S rRNA gene sequences, the resolution of the ITS sequence-based tree was higher, but species positioning and clustering were similar with both approaches. The recent separation of Porphyromonas gulae and Porphyromonas gingivalis into distinct species was confirmed by the ITS data. In addition, analysis of the ITS sequences of 24 clinical isolates of Porphyromonas asaccharolytica plus the type strain ATCC 25260(T) divided the sequences into two clusters, of which one was alpha-fucosidase-positive (like the type strain) while the other was alpha-fucosidase-negative. The latter resembled the previously studied unusual extra-oral isolates of 'Porphyromonas endodontalis-like organisms' (PELOs) which could therefore be called 'Porphyromonas asaccharolytica-like organisms' (PALOs), based on the genetic identification. Moreover, the proposal of alpha-fucosidase-negative P. asaccharolytica strains as a new species should also be considered.

Growth characteristics and a novel method for identification (the WEE-TAB system) of Porphyromonas species isolated from infected dog and cat bite wounds in humans

Thirty-nine clinical isolates of Porphyromonas species recovered from infected cat and dog bite wounds in humans and eight American Type Culture Collection and National Collection of Type Cultures type strains were characterized by using the API ZYM system, the RapID ANA II system, and conventional biochemical methods. Growth characteristics on various agar media were compared. All strains grew on brucella blood agar supplemented with vitamin K1 and hemin and on brucella laked blood agar supplemented with vitamin K1 and hemin. In contrast, only 34% of strains grew on unsupplemented brucella blood agar, 62% grew on Columbia blood agar, and 70% grew on tryptic soy blood agar (the last three media did not contain vitamin K1 or hemin). The ability of the single-tube, triple-substrate WEE-TAB system to detect the preformed enzymes N-acetyl-beta-D-glucosaminidase, alpha-D-galactosidase, beta-D-galactosidase, alpha-fucosidase, trypsin-like activity, and chymotrypsin was evaluated. The WEE-TAB test results were easy to interpret; the WEE-TAB tests were more sensitive than the comparable tests with the API ZYM and RapID ANA II systems for the detection of alpha-D-galactosidase, beta-D-galactosidase, trypsin, and chymotrypsin, and the WEE-TAB tests accurately identified Porphyromonas species.

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.

In vitro activities of iodonium salts against oral and dental anaerobes

The comparative in vitro activities of 11 iodonium salt compounds, 0.12% chlorhexidine, and four antimicrobial agents against 322 anaerobic and fastidious potential dental and periodontal bacterial pathogens were studied. Iodonium salts 3, 4, 5, 9, and 10 had in vitro activities comparable to that of chlorhexidine against most isolates. These compounds may be suitable for incorporation into an oral mouthwash.

Specimen collection and transport, anaerobic culture techniques, and identification of anaerobes

Excellent progress has been made in recent years in the development and refinement of technical materials used for transporting specimens and growing and identifying anaerobes. Several good systems for maintaining swabs and vials for transporting liquid specimens are commercially available. Anaerobic bags are useful for transporting unusual specimens, such as tissue or bone, and are also a convenient way to incubate small numbers of plates. Several different types of anaerobic chambers, with or without gloves, and separately enclosed incubators are being used by an increasing number of laboratories. Prereduced anaerobically sterilized plates and biochemicals in tubes are available from several commercial sources. A new rapid identification microsystem based on tests for performed enzymes permits identification of many clinically significant anaerobes to the species level in 4 hr.

Ceftaroline versus isolates from animal bite wounds: comparative in vitro activities against 243 isolates, including 156 Pasteurella species isolates

More than 5 million Americans are bitten by animals, usually dogs, annually. Bite patients comprise ∼1% of all patients who visit emergency departments (300,000/year), and approximately 10,000 require hospitalization and intravenous antibiotics. Ceftaroline is the bioactive component of the prodrug ceftaroline fosamil, which is FDA approved for the treatment of acute bacterial skin and skin structure infections (ABSSSIs), including those containing methicillin-resistant Staphylococcus aureus (MRSA). There are no in vitro data about the activity of ceftaroline against Pasteurella multocida subsp. multocida and Pasteurella multocida subsp. septica, other Pasteurella spp., or other bite wound isolates. We therefore studied the in vitro activity of ceftaroline against 243 animal bite isolates. MICs were determined using the broth microdilution method according to CLSI guidelines. Comparator drugs included cefazolin, ceftriaxone, ertapenem, ampicillin-sulbactam, azithromycin, doxycycline, and sulfamethoxazole-trimethoprim (SMX-TMP). Ceftaroline was the most active agent against all 5 Pasteurella species, including P. multocida subsp. multocida and P. multocida subsp. septica, with a maximum MIC of ≤0.008 μg/ml; more active than ceftriaxone and ertapenem (MIC(90)s, ≤0.015 μg/ml); and more active than cefazolin (MIC(90), 0.5 μg/ml) doxycycline (MIC(90), 0.125 μg/ml), azithromycin (MIC(90), 0.5 μg/ml), ampicillin-sulbactam (MIC(90), 0.125 μg/ml), and SMX-TMP (MIC(90), 0.125 μg/ml). Ceftaroline was also very active against all S. aureus isolates (MIC(90), 0.125 μg/ml) and other Staphylococcus and Streptococcus species, with a maximum MIC of 0.125 μg/ml against all bite isolates tested. Ceftaroline has potential clinical utility against infections involving P. multocida, other Pasteurella species, and aerobic Gram-positive isolates, including S. aureus.

In vitro activities of garenoxacin (BMS-284756) against 170 clinical isolates of nine Pasteurella species

The in vitro susceptibilities of 170 clinical isolates plus 12 American Type Culture Collection strains of Pasteurella species comprising nine species and three Pasteurella multocida subspecies were studied by an agar dilution method. Garenoxacin (BMS-284756), a new des-fluoro(6) quinolone, was active at 90% of the strains susceptible to Collapse

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MESH Headings

• Anti-Infective Agents/pharmacology
• Bites and Stings/microbiology
• Culture Media
• Drug Resistance, Bacterial
• Fluoroquinolones
• Humans
• Indoles
• Microbial Sensitivity Tests
• Pasteurella/drug effects
• Pasteurella Infections/microbiology
• Quinolones
• United States

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Bactericidal activities of methoxyfluoroquinolones gatifloxacin and moxifloxacin against aerobic and anaerobic respiratory pathogens in serum

Gatifloxacin (Bristol-Myers Squibb) and moxifloxacin (Bayer) are new methoxyfluoroquinolones with broad-spectrum activity against aerobic and anaerobic pathogens of the respiratory tract. In this investigation, we analyzed the bactericidal activity in serum over time of these antimicrobials against three aerobic (Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus) and four anaerobic (Peptostreptococcus micros, Peptostreptococcus magnus, Fusobacterium nucleatum, and Prevotella melaninogenica) bacteria associated with respiratory tract infections. Serum samples were obtained from 11 healthy male subjects following a single 400-mg oral dose of gatifloxacin and moxifloxacin. These samples were collected prior to and at 2, 6, 12, and 24 h after the dose of each drug. Gatifloxacin exhibited bactericidal activity for a median of 12 h against Streptococcus pneumoniae (MIC = 0.5 micro g/ml), Peptostreptococcus micros (MIC = 0.25 micro g/ml), and F. nucleatum (MIC = 0.5 micro g/ml) and 24 h against H. influenzae (MIC = 0.03 micro g/ml), Staphylococcus aureus (MIC = 0.125 micro g/ml), Peptostreptococcus magnus (MIC = 0.125 micro g/ml), and Prevotella melaninogenica (MIC = 0.5 micro g/ml). Moxifloxacin exhibited bactericidal activity for a median of 24 h against Streptococcus pneumoniae (MIC = 0.125 micro g/ml), H. influenzae (MIC = 0.015 micro g/ml), Staphylococcus aureus (MIC = 0.06 micro g/ml), F. nucleatum (MIC = 0.5 micro g/ml), Prevotella melaninogenica (MIC =0.5 micro g/ml), Peptostreptococcus magnus (MIC = 0.125 micro g/ml), and Peptostreptococcus micros (MIC = 0.25 micro g/ml). The results from this pharmacodynamic study suggest that these fluoroquinolones would have prolonged killing activity against these organisms in vivo and may have clinical utility in the treatment of mixed aerobic-anaerobic respiratory tract infections.