Efficacy of Delafloxacin versus Moxifloxacin against Bacterial Respiratory Pathogens in Adults with Community-Acquired Bacterial Pneumonia (CABP): Microbiology Results from the Delafloxacin Phase 3 CABP Trial

ABSTRACT Delafloxacin is a novel fluoroquinolone with activity against Gram-positive, Gram-negative, and atypical pathogens, including fluoroquinolone-nonsusceptible methicillin-resistant Staphylococcus aureus (MRSA). The microbiological results of a phase 3 clinical trial in adults with community-acquired pneumonia (CAP) comparing delafloxacin (300 mg intravenously [i.v.] with the option to switch to 450 mg orally every 12 h) to moxifloxacin (400 mg i.v. with the option to switch to 400 mg orally once a day [QD]) were determined. Patients from 4 continents, predominately Europe but also South America and Asia, were enrolled. The microbiological intent-to-treat (MITT) population included 520 patients, and 60.5% of these patients had a bacterial pathogen identified. Multiple diagnostic methods were employed, including culture, serology, PCR, and urinary antigen tests. Based on baseline MIC90 values, delafloxacin exhibited at least 16-fold greater activity than moxifloxacin for Gram-positive and fastidious Gram-negative pathogens. Delafloxacin retained activity against resistant phenotypes found in Streptococcus pneumoniae (penicillin-, macrolide-, and multiple-drug resistant), Haemophilus species (β-lactamase producing and macrolide nonsusceptible), and S. aureus (MRSA and fluoroquinolone-nonsusceptible methicillin-susceptible S. aureus [MSSA]). The microbiological success rates were 92.7% for S. pneumoniae (87.5% for penicillin-resistant S. pneumoniae [PRSP]), 92.6% for S. aureus (100% for MRSA), 100% for Escherichia coli, 82.4% for Klebsiella pneumoniae, 100% for Klebsiella oxytoca, 100% for Moraxella catarrhalis, 91.7% for Haemophilus influenzae, 88.6% for Haemophilus parainfluenzae, 96.7% for Mycoplasma pneumoniae, 93.1% for Legionella pneumophila, and 100% for Chlamydia pneumoniae. There was little correlation between MICs and outcomes, with a high proportion of favorable outcomes observed across all delafloxacin baseline MIC values. Delafloxacin may be considered a treatment option as monotherapy for CAP in adults, where broad-spectrum coverage including MRSA activity is desirable.

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Lefamulin in Patients with Community-Acquired Bacterial Pneumonia Caused by Atypical Respiratory Pathogens: Pooled Results from Two Phase 3 Trials

Antibiotics ◽

10.3390/antibiotics10121489 ◽

2021 ◽

Vol 10 (12) ◽

pp. 1489

Author(s):

Susanne Paukner ◽

David Mariano ◽

Anita F. Das ◽

Gregory J. Moran ◽

Christian Sandrock ◽

...

Keyword(s):

Clinical Response ◽

Legionella Pneumophila ◽

Bacterial Pneumonia ◽

Chlamydia Pneumoniae ◽

Diagnostic Methods ◽

Phase 3 ◽

Two Phase ◽

Diagnostic Modality ◽

Risk Class ◽

Atypical Pathogens

Lefamulin was the first systemic pleuromutilin antibiotic approved for intravenous and oral use in adults with community-acquired bacterial pneumonia based on two phase 3 trials (Lefamulin Evaluation Against Pneumonia [LEAP]-1 and LEAP-2). This pooled analysis evaluated lefamulin efficacy and safety in adults with community-acquired bacterial pneumonia caused by atypical pathogens (Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydia pneumoniae). In LEAP-1, participants received intravenous lefamulin 150 mg every 12 h for 5–7 days or moxifloxacin 400 mg every 24 h for 7 days, with optional intravenous-to-oral switch. In LEAP-2, participants received oral lefamulin 600 mg every 12 h for 5 days or moxifloxacin 400 mg every 24 h for 7 days. Primary outcomes were early clinical response at 96 ± 24 h after first dose and investigator assessment of clinical response at test of cure (5–10 days after last dose). Atypical pathogens were identified in 25.0% (91/364) of lefamulin-treated patients and 25.2% (87/345) of moxifloxacin-treated patients; most were identified by ≥1 standard diagnostic modality (M. pneumoniae 71.2% [52/73]; L. pneumophila 96.9% [63/65]; C. pneumoniae 79.3% [46/58]); the most common standard diagnostic modality was serology. In terms of disease severity, more than 90% of patients had CURB-65 (confusion of new onset, blood urea nitrogen > 19 mg/dL, respiratory rate ≥ 30 breaths/min, blood pressure <90 mm Hg systolic or ≤60 mm Hg diastolic, and age ≥ 65 years) scores of 0–2; approximately 50% of patients had PORT (Pneumonia Outcomes Research Team) risk class of III, and the remaining patients were more likely to have PORT risk class of II or IV versus V. In patients with atypical pathogens, early clinical response (lefamulin 84.4–96.6%; moxifloxacin 90.3–96.8%) and investigator assessment of clinical response at test of cure (lefamulin 74.1–89.7%; moxifloxacin 74.2–97.1%) were high and similar between arms. Treatment-emergent adverse event rates were similar in the lefamulin (34.1% [31/91]) and moxifloxacin (32.2% [28/87]) groups. Limitations to this analysis include its post hoc nature, the small numbers of patients infected with atypical pathogens, the possibility of PCR-based diagnostic methods to identify non-etiologically relevant pathogens, and the possibility that these findings may not be generalizable to all patients. Lefamulin as short-course empiric monotherapy, including 5-day oral therapy, was well tolerated in adults with community-acquired bacterial pneumonia and demonstrated high clinical response rates against atypical pathogens.

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In Vitro Activity of Ceftazidime-Avibactam against Isolates from Respiratory and Blood Specimens from Patients with Nosocomial Pneumonia, Including Ventilator-Associated Pneumonia, in a Phase 3 Clinical Trial

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02356-19 ◽

2020 ◽

Vol 64 (5) ◽

Cited By ~ 2

Author(s):

Gregory G. Stone ◽

Patricia A. Bradford ◽

Margaret Tawadrous ◽

Dianna Taylor ◽

Mary Jane Cadatal ◽

...

Keyword(s):

Nosocomial Pneumonia ◽

Bacterial Pathogen ◽

Multidrug Resistant ◽

Ventilator Associated Pneumonia ◽

Phase 3 ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Highly Active

ABSTRACT Nosocomial pneumonia (NP), including ventilator-associated pneumonia (VAP), is increasingly associated with multidrug-resistant Gram-negative pathogens. This study describes the in vitro activity of ceftazidime-avibactam, ceftazidime, and relevant comparator agents against bacterial pathogens isolated from patients with NP, including VAP, enrolled in a ceftazidime-avibactam phase 3 trial. Gram-positive pathogens were included if coisolated with a Gram-negative pathogen. In vitro susceptibility was determined at a central laboratory using Clinical and Laboratory Standards Institute broth microdilution methods. Of 817 randomized patients, 457 (55.9%) had ≥1 Gram-negative bacterial pathogen(s) isolated at baseline, and 149 (18.2%) had ≥1 Gram-positive pathogen(s) coisolated. The most common isolated pathogens were Klebsiella pneumoniae (18.8%), Pseudomonas aeruginosa (15.8%), and Staphylococcus aureus (11.5%). Ceftazidime-avibactam was highly active in vitro against 370 isolates of Enterobacteriaceae, with 98.6% susceptible (MIC90, 0.5 μg/ml) compared with 73.2% susceptible for ceftazidime (MIC90, >64 μg/ml). The percent susceptibility values for ceftazidime-avibactam and ceftazidime against 129 P. aeruginosa isolates were 88.4% and 72.9% (MIC90 values of 16 μg/ml and 64 μg/ml), respectively. Among ceftazidime-nonsusceptible Gram-negative isolates, ceftazidime-avibactam percent susceptibility values were 94.9% for 99 Enterobacteriaceae and 60.0% for 35 P. aeruginosa. MIC90 values for linezolid and vancomycin (permitted per protocol for Gram-positive coverage) were within their respective MIC susceptibility breakpoints against the Gram-positive pathogens isolated. This analysis demonstrates that ceftazidime-avibactam was active in vitro against the majority of Enterobacteriaceae and P. aeruginosa isolates from patients with NP, including VAP, in a phase 3 trial. (This study has been registered at ClinicalTrials.gov under identifier NCT01808092.)

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Surveillance of Omadacycline Activity against Clinical Isolates from a Global Collection (North America, Europe, Latin America, Asia-Western Pacific), 2010-2011

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00018-17 ◽

2017 ◽

Vol 61 (5) ◽

Cited By ~ 30

Author(s):

Michael A. Pfaller ◽

Michael D. Huband ◽

Paul R. Rhomberg ◽

Robert K. Flamm

Keyword(s):

Latin America ◽

North America ◽

Klebsiella Oxytoca ◽

Enterobacter Aerogenes ◽

Community Acquired Pneumonia ◽

Asia Pacific ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Viridans Group Streptococci

ABSTRACT Omadacycline is a broad-spectrum aminomethylcycline in late-stage clinical development for the treatment of acute bacterial skin and skin structure infections and community-acquired pneumonia as an oral and an intravenous once-daily formulation. In this study, omadacycline and comparators were tested against 69,246 nonduplicate bacterial isolates collected prospectively during 2010 and 2011 from medical centers in Asia-Pacific (11,397 isolates), Europe (23,490 isolates), Latin America (8,038 isolates), and North America (26,321 isolates). Omadacycline was tested by broth microdilution following Clinical and Laboratory Standards Institute M07-A10 (2015) methods. A total of 99.9% of Staphylococcus aureus isolates were inhibited by ≤2 μg/ml of omadacycline (MIC50/90, 0.12/0.25 μg/ml), including 100.0% of methicillin-susceptible S. aureus isolates and 99.8% of methicillin-resistant S. aureus isolates. Omadacycline potencies were comparable for Streptococcus pneumoniae (MIC50/90, 0.06/0.06 μg/ml), viridans group streptococci (MIC50/90, 0.06/0.12 μg/ml), and beta-hemolytic streptococci (MIC50/90, 0.06/0.12 μg/ml) regardless of species and susceptibility to penicillin. Omadacycline was active against Enterobacteriaceae and was most active against Escherichia coli (MIC50/90, 0.5/2 μg/ml), Enterobacter aerogenes (MIC50/90, 2/4 μg/ml), Klebsiella oxytoca (MIC50/90, 1/4 μg/ml), and Citrobacter spp. (MIC50/90, 1/4 μg/ml). Omadacycline was active against Haemophilus influenzae (MIC50/90, 1/1 μg/ml) regardless of β-lactamase status and against Moraxella catarrhalis (MIC50/90, 0.12/0.25 μg/ml). The potent activity of omadacycline against Gram-positive and Gram-negative bacteria indicates that omadacycline merits further study in serious infections in which multidrug resistance and mixed Gram-positive and Gram-negative infections may be a concern.

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In VitroAntibacterial Activity of AZD0914, a New Spiropyrimidinetrione DNA Gyrase/Topoisomerase Inhibitor with Potent Activity against Gram-Positive, Fastidious Gram-Negative, and Atypical Bacteria

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.04124-14 ◽

2014 ◽

Vol 59 (1) ◽

pp. 467-474 ◽

Cited By ~ 44

Author(s):

Michael D. Huband ◽

Patricia A. Bradford ◽

Linda G. Otterson ◽

Gregory S. Basarab ◽

Amy C. Kutschke ◽

...

Keyword(s):

Antibacterial Activity ◽

Legionella Pneumophila ◽

Bacterial Species ◽

Dna Gyrase ◽

Cross Resistance ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Topoisomerase Inhibitor

ABSTRACTAZD0914 is a new spiropyrimidinetrione bacterial DNA gyrase/topoisomerase inhibitor with potentin vitroantibacterial activity against key Gram-positive (Staphylococcus aureus,Staphylococcus epidermidis,Streptococcus pneumoniae,Streptococcus pyogenes, andStreptococcus agalactiae), fastidious Gram-negative (Haemophilus influenzaeandNeisseria gonorrhoeae), atypical (Legionella pneumophila), and anaerobic (Clostridium difficile) bacterial species, including isolates with known resistance to fluoroquinolones. AZD0914 works via inhibition of DNA biosynthesis and accumulation of double-strand cleavages; this mechanism of inhibition differs from those of other marketed antibacterial compounds. AZD0914 stabilizes and arrests the cleaved covalent complex of gyrase with double-strand broken DNA under permissive conditions and thus blocks religation of the double-strand cleaved DNA to form fused circular DNA. Whereas this mechanism is similar to that seen with fluoroquinolones, it is mechanistically distinct. AZD0914 exhibited low frequencies of spontaneous resistance inS. aureus, and if mutants were obtained, the mutations mapped togyrB. Additionally, no cross-resistance was observed for AZD0914 against recent bacterial clinical isolates demonstrating resistance to fluoroquinolones or other drug classes, including macrolides, β-lactams, glycopeptides, and oxazolidinones. AZD0914 was bactericidal in both minimum bactericidal concentration andin vitrotime-kill studies. Inin vitrocheckerboard/synergy testing with 17 comparator antibacterials, only additivity/indifference was observed. The potentin vitroantibacterial activity (including activity against fluoroquinolone-resistant isolates), low frequency of resistance, lack of cross-resistance, and bactericidal activity of AZD0914 support its continued development.

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In Vitro Activity of Ceftazidime-Avibactam against Isolates from Patients in a Phase 3 Clinical Trial for Treatment of Complicated Intra-abdominal Infections

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02584-17 ◽

2018 ◽

Vol 62 (7) ◽

pp. e02584-17 ◽

Cited By ~ 4

Author(s):

Gregory G. Stone ◽

Paul Newell ◽

Patricia A. Bradford

Keyword(s):

Clinical Trial ◽

Pseudomonas Aeruginosa ◽

Treatment Options ◽

Multidrug Resistant ◽

Phase 3 ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Abdominal Infections

ABSTRACT The increasing prevalence of multidrug-resistant Gram-negative pathogens has generated a requirement for new treatment options. Avibactam, a novel non-β-lactam–β-lactamase inhibitor, restores the activity of ceftazidime against Ambler class A, C, and some class D β-lactamase-producing strains of Enterobacteriaceae and Pseudomonas aeruginosa. The in vitro activities of ceftazidime-avibactam versus comparators were evaluated against 1,440 clinical isolates obtained in a phase 3 clinical trial in patients with complicated intra-abdominal infections (cIAI; ClinicalTrials.gov identifier NCT01499290). Overall, in vitro activities were determined for 803 Enterobacteriaceae, 70 P. aeruginosa, 304 Gram-positive aerobic, and 255 anaerobic isolates obtained from 1,066 randomized patients at baseline. Susceptibility was determined by broth microdilution. The most commonly isolated Gram-negative, Gram-positive, and anaerobic pathogens were Escherichia coli (n = 549), Streptococcus anginosus (n = 130), and Bacteroides fragilis (n = 96), respectively. Ceftazidime-avibactam was highly active against isolates of Enterobacteriaceae, with an overall MIC90 of 0.25 mg/liter. In contrast, the MIC90 for ceftazidime alone was 32 mg/liter. The MIC90 value for ceftazidime-avibactam (4 mg/liter) was one dilution lower than that of ceftazidime alone (8 mg/liter) against isolates of Pseudomonas aeruginosa. The ceftazidime-avibactam MIC90 for 109 ceftazidime-nonsusceptible Enterobacteriaceae isolates was 2 mg/liter, and the MIC range for 6 ceftazidime-nonsusceptible P. aeruginosa isolates was 8 to 32 mg/liter. The MIC90 values were within the range of susceptibility for the study drugs permitted per the protocol in the phase 3 study to provide coverage for aerobic Gram-positive and anaerobic pathogens. These findings demonstrate the in vitro activity of ceftazidime-avibactam against bacterial pathogens commonly observed in cIAI patients, including ceftazidime-nonsusceptible Enterobacteriaceae. (This study has been registered at ClinicalTrials.gov under identifier NCT01499290.)

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2230. Analysis of the Microbiological Data from the Delafloxacin (DLX) Phase 3 Community-acquired Bacterial Pneumonia (CABP) Trial

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.1908 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S761-S762 ◽

Cited By ~ 1

Author(s):

Sandra McCurdy ◽

Kara Keedy ◽

Laura Lawrence ◽

Amanda Sheets ◽

Megan Quintas

Keyword(s):

Legionella Pneumophila ◽

Chlamydia Pneumoniae ◽

Oral Treatment ◽

Phenotypic Characterization ◽

Clinical Activity ◽

Microbiological Analysis ◽

Culture Methods ◽

Phase 3 ◽

Atypical Pathogens

Abstract Background DLX is a novel fluoroquinolone (FQ) antibiotic with Gram-positive/MRSA, Gram-negative and atypical activity. It offers IV and oral treatment with no QT restrictions. In a Phase 3 study in CABP patients, DLX was non-inferior to moxifloxacin (MOX) in the primary endpoint, early clinical response at 96 ± 24 hours (88.9 vs. 89.0; 95% CI: −4.4, 4.1) in the intent-to-treat (ITT) population. A detailed microbiological analysis was conducted. Methods CABP pathogens were identified by culture/non-culture methods. Pathogens identified by non-culture methods included Streptococcus pneumoniae (Sp; culture, urinary antigen [UA], nasopharyngeal [NP] swab lytA PCR), Legionella pneumophila (Lp) (culture, UA, serology), Mycoplasma pneumoniae (Mp; culture, serology), and Chlamydia pneumoniae (Cp; serology). All other pathogens were identified using culture only. For Sp cultured from NP, a concomitant lytA PCR value of ≥ 1000 gene copies/mL was required. All isolates underwent susceptibility testing, and a subset of isolates underwent molecular or phenotypic characterization including whole-genome sequencing for FQ resistance mechanisms, PCR for PVL/mecA genes (S. aureus), β-lactamases (Haemophilus/Moraxella spp), and serotyping (Sp). Results Included in submitted image. Conclusion DLX demonstrated potent in vitro and clinical activity against CABP pathogens, including Sp [MRSP, MDRSP, PRSP], MRSA, Haemophilus species, Enterobacteriaceae, P. aeruginosa, and the atypical pathogens Cp, Mp, and Lp. Disclosures All authors: No reported disclosures.

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In Vitro Activity of Ceftaroline against Gram-Positive and Gram-Negative Pathogens Isolated from Patients in Canadian Hospitals in 2009

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01787-10 ◽

2011 ◽

Vol 55 (6) ◽

pp. 2837-2846 ◽

Cited By ~ 34

Author(s):

James A. Karlowsky ◽

Heather J. Adam ◽

Melanie R. DeCorby ◽

Philippe R. S. Lagacé-Wiens ◽

Daryl J. Hoban ◽

...

Keyword(s):

Staphylococcus Epidermidis ◽

Klebsiella Oxytoca ◽

Canadian Hospital ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Recent Collection

ABSTRACTThein vitroactivities of ceftaroline and comparative agents were determined for a collection of the most frequently isolated bacterial pathogens from hospital-associated patients across Canada in 2009 as part of the ongoing CANWARD surveillance study. In total, 4,546 isolates from 15 sentinel Canadian hospital laboratories were tested using the Clinical and Laboratory Standards Institute (CLSI) broth microdilution method. Compared with other cephalosporins, including ceftobiprole, cefepime, and ceftriaxone, ceftaroline exhibited the greatest potency against methicillin-susceptibleStaphylococcus aureus(MSSA), with a MIC90of 0.25 μg/ml. Ceftaroline also demonstrated greater potency than ceftobiprole against community-associated methicillin-resistantS. aureus(MRSA) (MIC90, 0.5 μg/ml) and health care-associated MRSA (MIC90, 1 μg/ml) and was at least 4-fold more active than other cephalosporins againstStaphylococcus epidermidis; all isolates of MSSA and MRSA tested were susceptible to ceftaroline (MIC, ≤1 μg/ml). Against streptococci, includingStreptococcus pneumoniae, ceftaroline MICs (MIC90, ≤0.03 μg/ml) were comparable to those of ceftobiprole; however, against penicillin-nonsusceptible, macrolide-nonsusceptible, and multidrug-nonsusceptible isolates ofS. pneumoniae, ceftaroline demonstrated 2- to 4-fold and 4- to 16-fold more potent activities than those of ceftobiprole and ceftriaxone, respectively. All isolates ofS. pneumoniaetested were susceptible to ceftaroline (MIC, ≤0.25 μg/ml). Among Gram-negative isolates, ceftaroline demonstrated potent activity (MIC90, ≤0.5 μg/ml) againstEscherichia coli(92.2% of isolates were susceptible),Klebsiella pneumoniae(94.1% of isolates were susceptible),Proteus mirabilis(97.7% of isolates were susceptible), andHaemophilus influenzae(100% of isolates were susceptible). Ceftaroline demonstrated less potent activity (MIC90, ≥4 μg/ml) againstEnterobacterspp.,Acinetobacter baumannii,Pseudomonas aeruginosa,Klebsiella oxytoca,Serratia marcescens, andStenotrophomonas maltophilia. Overall, ceftaroline demonstrated potentin vitroactivity against a recent collection of the most frequently encountered Gram-positive and Gram-negative isolates from patients attending hospitals across Canada in 2009.

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A Pathway Closely Related to the d-Tagatose Pathway of Gram-Negative Enterobacteria Identified in the Gram-Positive Bacterium Bacillus licheniformis

Applied and Environmental Microbiology ◽

10.1128/aem.03918-12 ◽

2013 ◽

Vol 79 (11) ◽

pp. 3511-3515 ◽

Cited By ~ 10

Author(s):

Edwige Van der Heiden ◽

Michaël Delmarcelle ◽

Sarah Lebrun ◽

Régine Freichels ◽

Alain Brans ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Gene Cluster ◽

Bacillus Licheniformis ◽

Klebsiella Oxytoca ◽

Negative Bacterium ◽

Positive Bacterium ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Bacterium Bacillus

ABSTRACTWe report the first identification of a gene cluster involved ind-tagatose catabolism inBacillus licheniformis. The pathway is closely related to thed-tagatose pathway of the Gram-negative bacteriumKlebsiella oxytoca, in contrast to thed-tagatose 6-phosphate pathway described in the Gram-positive bacteriumStaphylococcus aureus.

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Antimicrobial Activity of Omadacycline Tested against Clinical Bacterial Isolates from Hospitals in Mainland China, Hong Kong, and Taiwan: Results from the SENTRY Antimicrobial Surveillance Program (2013 to 2016)

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02262-18 ◽

2019 ◽

Vol 63 (3) ◽

Cited By ~ 11

Author(s):

Cecilia G. Carvalhaes ◽

Michael D. Huband ◽

Harald H. Reinhart ◽

Robert K. Flamm ◽

Helio S. Sader

Keyword(s):

Staphylococcus Aureus ◽

Hong Kong ◽

Klebsiella Oxytoca ◽

Surveillance Program ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Vancomycin Resistant ◽

Geographic Regions

ABSTRACTOmadacycline is a derivative of minocycline and the first agent of the aminomethylcycline class. A total of 3,282 organisms (1 per patient) were consecutively collected from patients hospitalized in China (including Hong Kong) and Taiwan. Susceptibility testing was performed by broth microdilution methods in a central laboratory (JMI Laboratories). The collection included Gram-positive and Gram-negative organisms from patients with pneumonia, bloodstream, skin, community-acquired respiratory, and other infections. Omadacycline was very potent againstStaphylococcus aureus(n= 689; MIC50/90, 0.12/0.25 mg/liter), including methicillin-resistantStaphylococcus aureus(MRSA;n= 299; MIC50/90, 0.12/0.5 mg/liter), and had similar activity across geographic regions. Omadacycline was very active againstStreptococcus pneumoniae(highest MIC, 0.25 mg/liter), β-hemolytic streptococci (highest MIC, 1 mg/liter), viridans group streptococci (highest MIC, 0.25 mg/liter), andEnterococcusspp. (highest MIC, 0.5 mg/liter) from all geographic regions. Overall, 53.8% ofS. pneumoniaeisolates were penicillin resistant (penicillin MIC, ≥2 mg/liter) and 10.7% of enterococci (21.2% amongE. faeciumisolates) were vancomycin resistant. Omadacycline was active againstHaemophilus influenzae(MIC50/90, 0.5/1 mg/liter) regardless of β-lactamase production and was active againstMoraxella catarrhalis(MIC50/90, ≤0.12/0.25 mg/liter). AgainstEnterobacteriaceae, omadacycline was most active againstEscherichia coli(MIC50/90, 1/2 mg/liter),Klebsiella oxytoca(MIC50/90, 1/4 mg/liter), andEnterobacter cloacae(MIC50/90, 2/4 mg/liter). Omadacycline had potentin vitroactivity against Gram-positive and Gram-negative pathogens isolated from China and Taiwan and retained activity against problem pathogens, such as MRSA, vancomycin-resistant enterococci (VRE), penicillin-resistantS. pneumoniae(PRSPN), and extended-spectrum β-lactamase-producingE. coli. The observed MIC profile in Chinese isolates was very similar to that seen in the U.S. and European surveillance studies.

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Dynamics ofMycobacterium tuberculosisAg85B Revealed by a Sensitive Enzyme-Linked Immunosorbent Assay

mBio ◽

10.1128/mbio.00611-19 ◽

2019 ◽

Vol 10 (2) ◽

Cited By ~ 2

Author(s):

Joel D. Ernst ◽

Amber Cornelius ◽

Miriam Bolz

Keyword(s):

Protein Secretion ◽

Immunosorbent Assay ◽

Bacterial Population ◽

Enzyme Linked Immunosorbent Assay ◽

Bacterial Protein ◽

Gram Positive ◽

Gram Negative ◽

Content Type ◽

Bacterial Proteins

ABSTRACTSecretion of specific proteins contributes to pathogenesis and immune responses in tuberculosis and other bacterial infections, yet the kinetics of protein secretion and fate of secreted proteinsin vivoare poorly understood. We generated new monoclonal antibodies that recognize theMycobacteriumtuberculosissecreted protein Ag85B and used them to establish and characterize a sensitive enzyme-linked immunosorbent assay (ELISA) to quantitate Ag85B in samples generatedin vitroandin vivo. We found that nutritional or culture conditions had little impact on the secretion of Ag85B and that there is considerable variation in Ag85B secretion by distinct strains in theM. tuberculosiscomplex: compared with the commonly used H37Rv strain (lineage 4),Mycobacteriumafricanum(lineage 6) secretes less Ag85B, and two strains from lineage 2 secrete more Ag85B. We also used the ELISA to determine that the rate of secretion of Ag85B is 10- to 100-fold lower than that of proteins secreted by Gram-negative and Gram-positive bacteria, respectively. ELISA quantitation of Ag85B in lung homogenates ofM. tuberculosisH37Rv-infected mice revealed that although Ag85B accumulates in the lungs as the bacterial population expands, the amount of Ag85B per bacterium decreases nearly 10,000-fold at later stages of infection, coincident with the development of T cell responses and arrest of bacterial population growth. These results indicate that bacterial protein secretionin vivois dynamic and regulated, and quantitation of secreted bacterial proteins can contribute to the understanding of pathogenesis and immunity in tuberculosis and other infections.IMPORTANCEBacterial protein secretion contributes to host-pathogen interactions, yet the process and consequences of bacterial protein secretion during infection are poorly understood. We developed a sensitive ELISA to quantitate a protein (termed Ag85B) secreted byM. tuberculosisand used it to find that Ag85B secretion occurs with slower kinetics than for proteins secreted by Gram-positive and Gram-negative bacteria and that accumulation of Ag85B in the lungs is markedly regulated as a function of the bacterial population density. Our results demonstrate that quantitation of bacterial proteins during infection can reveal novel insights into host-pathogen interactions.

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