Effect of tebipenem pivoxil hydrobromide on the normal gut microbiota of a healthy adult population in Sweden: a randomised controlled trial.

BACKGROUND: Antimicrobials cause perturbations in the composition and diversity of the host microbiome. We aimed to compare gut microbiome perturbations caused by oral tebipenem pivoxil hydrobromide (a novel carbapenem) and by amoxicillin-clavulanic acid (an orally administered ß-lactam-ß-lactam inhibitor combination widely used in clinical practice). METHODS: We did a phase 1, single-centre, randomised, parallel-group, active-control trial to evaluate the effect of tebipenem pivoxil hydrobromide on the human gut microbiota. Healthy participants aged 18 years or older with no documented illnesses during recruitment were enrolled at Karolinska University Hospital (Stockholm, Sweden). Study participants were stratified by sex and block-randomised in a 1:1 ratio to treatment with either tebipenem pivoxil hydrobromide (600 mg orally every 8 h) or amoxicillin-clavulanic acid (500 mg amoxicillin and 125 mg clavulanic acid orally every 8 h). The study included 10 days of treatment (days 1-10) and four follow-up visits (days 14, 21, 90, and 180). The trial was open-label for clinical investigators and patients, but masked for microbiology investigators. Faecal samples were collected at all visits. Sequencing of 16S rDNA was used to measure the diversity metrics, and quantitative culture to quantify selected taxa. The primary outcomes were changes in the α and ß diversity and log count of colony-forming units for selected taxa between samples compared with baseline (day 1), and whether any changes reverted during the follow-up period. The analyses were done in the intention-to-treat population. This study was registered with ClinicalTrials.gov (NCT04376554). FINDINGS: The study was conducted between Jan 23, 2020, and April 6, 2021. 49 volunteers were screened for eligibility, among whom 30 evaluable participants (14 men and 16 women) were assigned: 15 (50%) to the tebipenem pivoxil hydrobromide group and 15 (50%) to the amoxicillin-clavulanic acid group. Baseline characteristics were similar between groups. Complete follow-up was available for all participants, and all participants except one completed treatment as assigned. The diversity metrics showed significant changes from baseline during the treatment period. Significant decreases in richness were observed on days 4-10 (p≤0·0011) in the amoxicillin-clavulanic acid group and on days 4-14 (p≤0·0019) in the tebipenem pivoxil hydrobromide group. Similarly, evenness was significantly decreased during treatment in the amoxicillin-clavulanic acid group (day 4, p=0·030) and the tebipenem pivoxil hydrobromide group (days 4-10, p<0·0001) compared with baseline. Quantitative cultures showed significant decreases in Enterobacterales (days 4-7, p≤0·0030), Enterococcus spp (days 4-14, p=0·025 to p<0·0001), Bifidobacterium spp (days 2-4, p≤0·026), and Bacteroides spp (days 4-10, p≤0·030) in the tebipenem pivoxil hydrobromide group. Similarly, in amoxicillin-clavulanic acid recipients, significant changes were observed in Enterobacterales (days 4-10, p≤0·048), Bifidobacterium spp (days 2-4, p≤0·013), and Lactobacillus spp (days 2-4, p≤0·020). Samples from the follow-up period were not significantly different from those at baseline in ß diversity analysis (PERMANOVA, p>0·99). By the end of the study, no significant change was observed compared with baseline in either group. There were no deaths or severe adverse events. INTERPRETATION: The impact of tebipenem pivoxil hydrobromide on the gut microbiome was similar to that of amoxicillin-clavulanic acid. The safety of antibiotic use with regard to the microbiome should be given attention, as dysbiosis is associated with health and disease. FUNDING: Spero Therapeutics.

In Vitro Activity of Omadacycline and Five Comparators against Contemporary Ribotypes of Clostridioides difficile in Stockholm, Sweden.

Clostridioides difficile infection represents a growing clinical challenge. The new compound omadacycline is a potential treatment alternative, as many antibiotics have limited activity or are rarely used due to costs and side effects. The activity of omadacycline and five comparators was assessed with agar dilution on a 2015-to-2018 collection of 65 C. difficile isolates from Sweden. Omadacycline demonstrated in vitro activity against the contemporary ribotypes of C. difficile, and further clinical investigation is needed. IMPORTANCE Evaluating the activity of novel antimicrobials like omadacycline is of great interest, as a reliable and efficient antimicrobial treatment for Clostridioides difficile infections is in demand.

In vitro activity of ceftazidime-avibactam against Gram-negative isolates collected in 18 European countries, 2015-2017.

BACKGROUND: Between 2015-2017, 21 850 Enterobacterales isolates and 6156 Pseudomonas aeruginosa (P. aeruginosa) isolates were collected by 77 centers in 18 European countries as part of the International Network for Optimal Resistance Monitoring (INFORM) study (which was included into the Antimicrobial Testing Leadership and Surveillance [ATLAS] study in 2018). METHODS: A central reference laboratory performed antimicrobial susceptibility testing using broth microdilution panels according to Clinical and Laboratory Standards Institute guidelines. The presence of ß-lactamases was confirmed using multiplex PCR assays. RESULTS: Among Enterobacterales isolates, the highest rates of susceptibility were to ceftazidime-avibactam (99.0%; MIC90 0.5 mg/L), meropenem (96.3%), amikacin (95.2%), and imipenem (92.8%). All Enterobacterales organisms were highly susceptible to colistin (≥ 94.6%), apart from Proteus mirabilis, which is intrinsically resistant to colistin. Susceptibility rates among ceftazidime-resistant isolates were 95.7% for ceftazidime-avibactam and 87.9% for colistin, and 78.5% and 71.1%, respectively, among carbapenemase-positive isolates. Colistin was the only agent with activity against metallo-ß-lactamases (100% susceptibility) among Enterobacterales and P. aeruginosa isolates. Overall susceptibility rates among P. aeruginosa were highest to colistin (99.5%) and ceftazidime-avibactam (92.3%), and were similar to ceftazidime-resistant isolates for colistin (98.9%) and reduced to 66.2% for ceftazidime-avibactam. Susceptibility rates among multidrug-resistant P. aeruginosa isolates were 98.9% to colistin and 71.7% to ceftazidime-avibactam. CONCLUSIONS: Clinical isolates of Enterobacterales and P. aeruginosa collected from Europe, between 2015-2017, were highly susceptible to ceftazidime-avibactam, suggesting it is a useful alternative agent for patients whose treatment options may be limited. Persistent antimicrobial resistance requires continued surveillance and monitoring.

Clostridium difficile Infection-Daily Symptoms (CDI-DaySyms™) questionnaire: psychometric characteristics and responder thresholds.

BACKGROUND: The purpose of the current study was to determine the final content validation, psychometric characteristics, clinically meaningful improvement, and responder thresholds of the Clostridium difficile infection (CDI)-Daily Symptoms (CDI-DaySyms™) patient-reported outcome (PRO) questionnaire. METHODS: This validation study was part of two phase III studies (NCT01987895 and NCT01983683) conducted in patients with mild-to-moderate or severe CDI who completed the CDI-DaySyms™ daily throughout the treatment period. The questionnaire was evaluated in three stages: final PRO item content validation (Stage I); psychometric evaluation of reliability and construct validity (Stage II); and determination of clinically meaningful improvement and responder thresholds using distribution-based methods (Stage III). RESULTS: The analysis included 168 patients. Most patients were female and Caucasian with mild-to-moderate CDI. The mean age was 57.1 years. Initial item analysis supported by confirmatory factor analysis demonstrated the relevance of 10 items grouped into three distinct domains (Diarrhea Symptoms, Abdominal Symptoms, and Systemic/Other Symptoms). Domain scores demonstrated acceptable internal consistency and test-retest reliability, were sensitive to change, and correlated in expected directions with other relevant symptom and disease-severity measures. Responder thresholds were defined as score changes of - 1.00, - 0.80, and - 0.70 in the Diarrhea Symptoms, Abdominal Symptoms, and Systemic/Other Symptoms domains, respectively. CONCLUSIONS: The CDI-DaySyms™ is a valid measure of patient-reported CDI symptoms, with good measurement properties, which supports its utility as an endpoint in clinical studies. Further studies confirming responder thresholds based on anchor-based methods are required. TRIAL REGISTRATION: NCT01987895 , registered November 20, 2013; NCT01983683 , registered November 14, 2013.

Cadazolid for the treatment of Clostridium difficile infection: results of two double-blind, placebo-controlled, non-inferiority, randomised phase 3 trials.

BACKGROUND: Cadazolid is a novel quinoxolidinone antibiotic developed for treating Clostridium difficile infection. We aimed to investigate the safety and efficacy of cadazolid compared with vancomycin in patients with C difficile infection. METHODS: IMPACT 1 and IMPACT 2 were identically designed, multicentre, double-blind, placebo-controlled, non-inferiority, randomised phase 3 trials. IMPACT 1 was done in Australia, Brazil, Canada, France, Germany, Italy, the Netherlands, Peru, Poland, Romania, Spain, and the USA, and IMPACT 2 was done in Argentina, Belgium, Brazil, Canada, Chile, Croatia, Czech Republic, Greece, Hungary, Israel, Romania, Slovakia, South Korea, the UK, and the USA. Patients (aged 18 years or older) with mild-to-moderate or severe C difficile infection (diarrhoea with positive glutamate dehydrogenase and toxin A or B enzyme immunoassays) were randomly assigned (1:1) with a randomisation list stratified by centre and C difficile infection episode type (block size of four), and allocation was masked to investigators and participants. Patients received either oral cadazolid 250 mg twice daily with vancomycin-matching placebo capsule four times daily or oral vancomycin 125 mg four times a day with cadazolid-matching placebo suspension twice daily for 10 days, with 30 days of follow-up. The primary efficacy outcome was non-inferiority (margin -10%) of cadazolid versus vancomycin for clinical cure in the modified intention-to-treat and per-protocol populations. Clinical cure was defined as resolution of diarrhoea with no additional treatment for C difficile infection. These trials are registered with ClinicalTrials.gov, numbers NCT01987895 (IMPACT 1) and NCT01983683 (IMPACT 2). FINDINGS: Between March 28, 2014, and March 24, 2017, for IMPACT 1, and Dec 13, 2013, and May 2, 2017, for IMPACT 2, 1263 participants were randomly assigned to receive cadazolid (306 in IMPACT 1 and 298 in IMPACT 2) or vancomycin (326 in IMPACT 1 and 311 in IMPACT 2). In the modified intention-to-treat population in IMPACT 1, 253 (84%) of 302 had clinical cure in the cadazolid group versus 271 (85%) of 318 in the vancomycin group. In IMPACT 2, 235 (81%) of 290 versus 258 (86%) of 301 had clinical cure. In the per-protocol population, 247 (88%) of 282 versus 264 (92%) of 288 had clinical cure in IMPACT 1 and 214 (87%) of 247 versus 237 (92%) of 259 in IMPACT 2. Non-inferiority for clinical cure to vancomycin was shown in IMPACT 1 but not in IMPACT 2 (IMPACT 1 treatment difference: -1·4 [95% CI -7·2 to 4·3] for modified intention to treat and -4·1 [-9·2 to 1·0] for per protocol; IMPACT 2: -4·7 [-10·7 to 1·3] for modified intention to treat and -4·9 [-10·4 to 0·6] for per protocol). The safety and tolerability profiles of the two antibiotics were similar. INTERPRETATION: Cadazolid was safe and well tolerated but did not achieve its primary endpoint of non-inferiority to vancomycin for clinical cure in one of two phase 3 C difficile infection trials. Therefore, further commercial development of cadazolid for C difficile infection is unlikely. FUNDING: Actelion Pharmaceuticals.

The CDI-DaySyms: Content Development of a New Patient-Reported Outcome Questionnaire for Symptoms of Clostridium difficile Infection.

OBJECTIVES: To develop a patient-reported outcome (PRO) questionnaire for symptoms of Clostridium difficile infection (CDI) following the US Food and Drug Administration PRO guidelines. METHODS: Patients' experiences of CDI symptoms were elicited in open-ended discussions with patients and nurses at five US sites (stage 1). A draft PRO measure was developed after demonstration of concept saturation. Two rounds of cognitive interviews were conducted with patients at three US sites (stage 2), with revision of the draft measure after each round. All patients were 18 years or older, with confirmed CDI. The study was conducted with input from a panel of five CDI experts in Europe and North America. RESULTS: Stage 1 included interviews with 18 patients and supplementary interviews with 6 nurses; 16 additional patients were interviewed in stage 2. Patients were representative of the general CDI population and were diverse in age, sex, and disease severity. Concept saturation was reached in stage 1. Items were organized in a draft conceptual framework with five hypothesized domains: diarrhea, abdominal discomfort, tiredness, lightheadedness, and other symptoms. Stage 2 demonstrated initial content validity of the 13-item draft daily diary (CDI-DaySyms). Participants reported that the questions were clear, relevant, and comprehensive. They were able to use the instructions to complete the diary correctly and considered the 24-hour recall period appropriate. CONCLUSIONS: The CDI-DaySyms captures symptoms relevant to patients undergoing CDI, demonstrating initial content validity. Final content and psychometric validity are being evaluated in a substudy comprising patients from two ongoing international clinical trials (ClinicalTrials.gov identifiers NCT01987895 and NCT01983683).

Molecular characteristics of Clostridium difficile strains from patients with a first recurrence more than 8 weeks after the primary infection.

BACKGROUND/PURPOSE: Nearly all published studies of recurrent Clostridium difficile infections (CDI) report recurrent CDI within 8 weeks after the primary infection. This study explored the molecular characteristics of C. difficile isolates from the first recurrent CDI more than 8 weeks after the primary infection. METHODS: Consecutive hospitalized patients with a recurrent CDI more than 8 weeks after a primary infection were enrolled prospectively from January 2008 to February 2011. All C. difficile isolates of the primary and recurrent infections were collected and subjected to polymerase chain reaction ribotyping and antimicrobial susceptibility testing. RESULTS: There were 62 cases of CDI in this study, which included 32 cases (51.6%) of recurrence due to the same ribotype of C. difficile, 26 (41.9%) cases due to a different ribotype, and four (6.5%) cases with 2-4 recurrences due to the same or different strains. One hundred and forty C. difficile isolates were obtained, which included 62 primary CDI isolates and 78 recurrent isolates. Ribotype 020 was the most common C. difficile strain in primary and recurrent infections. Ribotype 001 accounted for 15.4% (10/78) of recurrent infections and 3.2% (2/62) of primary infections (p = 0.0447). The minimum inhibitory concentration at 90% (MIC90) values of linezolid, moxifloxacin, and clindamycin against type 001 strains were much higher, compared to the three other common ribotypes. CONCLUSION: Recurrent CDI more than 8 weeks after a primary infection can be caused by the same or different C. difficile ribotype at similar percentages. Ribotype 001 C. difficile strains, which have a lower susceptibility to antimicrobials, were isolated more frequently in patients with a recurrent CDI.

In-vitro activity of solithromycin against anaerobic bacteria from the normal intestinal microbiota.

Solithromycin is a novel fluoroketolide with high activity against bacteria associated with community-acquired respiratory tract infections as well as gonorrhea. However, data on the activity of solithromycin against anaerobic bacteria from the normal intestinal microbiota are scarce. In this study, 1024 Gram-positive and Gram-negative anaerobic isolates from the normal intestinal microbiota were analyzed for in-vitro susceptibility against solithromycin and compared to azithromycin, amoxicillin/clavulanic acid, ceftriaxone, metronidazole and levofloxacin by determining the minimum inhibitory concentration (MIC). Solithromycin was active against Bifidobacteria (MIC50, 0.008 mg/L) and Lactobacilli (MIC50, 0.008 mg/L). The MIC50 for Clostridia, Bacteroides, Prevotella and Veillonella were 0.5, 0.5, 0.125 and 0.016 mg/L, respectively. Gram-positive anaerobes were more susceptible to solithromycin as compared to the other antimicrobials tested. The activity of solithromycin against Gram-negative anaerobes was equal or higher as compared to other tested agents.

Methicillin-resistant Staphylococcus aureus in Stockholm, Sweden: Molecular epidemiology and antimicrobial susceptibilities to ceftaroline, linezolid, mupirocin and vancomycin in 2014.

Methicillin-resistant Staphylococcus aureus (MRSA) is a public health problem worldwide. The aim of the present study was to investigate the molecular epidemiology and antimicrobial susceptibilities of MRSA strains in Stockholm, Sweden in 2014. Pulsed-field gel electrophoresis (PFGE) was used to characterise the strains. Antimicrobial susceptibilities to ceftaroline, linezolid and mupirocin were determined by the disc diffusion method. Etest was used to determine vancomycin susceptibility and to confirm resistance to ceftaroline, mupirocin and linezolid in non-susceptible strains. High-level ceftaroline-resistant strains [minimum inhibitory concentration (MIC)≥4mg/L] were confirmed by the broth microdilution method. spa typing was carried out on strains that were non-susceptible to the antibiotics tested. In total, 743 consecutive non-duplicate MRSA strains recovered in Stockholm in 2014 were investigated. PFGE analysis of the isolates revealed a population with 271 different PFGE patterns and three non-typeable strains. No PFGE type accounted for >10% of all strains. The most common PFGE types were MRSA-00-02 (6.9%) and MRSA-05-02 (4.6%). MRSA-05-02 is a USA300-like strain. The antimicrobial susceptibilities of the strains were as follows: ceftaroline, 98.5%; linezolid, 100%; mupirocin, 99.3%; and vancomycin, 100%. Two strains with spa t001 displayed ceftaroline MICs of 4mg/L. Three strains with spa types t002, t064 and t437 showed high-level mupirocin resistance (MIC>1024mg/L). In conclusion, there was a diverse genetic population among the MRSA isolates and no predominant genotype was found. This study identified a few strains with high-level ceftaroline resistance, high-level mupirocin resistance and high-risk genotypes.

Ecological Effect of Solithromycin on Normal Human Oropharyngeal and Intestinal Microbiota.

Solithromycin is a new fluoroketolide. The purpose of the present study was to investigate the effect of orally administered solithromycin on the human oropharyngeal and intestinal microbiota. Thirteen healthy volunteers (median age, 27.3 years) received oral solithromycin at 800 mg on day 1 followed by 400 mg daily on days 2 to 7. Fecal and saliva samples were collected at baseline and on days 2, 5, 7, 9, 14, and 21 for pharmacokinetic and microbiological analyses. Plasma samples were collected predose on days 2, 5, and 7 as proof of exposure, and solithromycin concentration ranges were 21.9 to 258 ng/ml, 18.0 to 386 ng/ml, and 16.9 to 417 ng/ml, respectively. The solithromycin concentrations in feces were 15.8 to 65.4 mg/kg, 24.5 to 82.7 mg/kg, 21.4 to 82.7 mg/kg, 12.1 to 72.4 mg/kg, 0.2 to 25.6 mg/kg, and 0 to 0.5 mg/kg on days 2, 5, 7, 9, 14, and 21, respectively. The numbers of enterobacteria and enterococci decreased and were normalized on day 14. The numbers of lactobacilli and bifidobacteria decreased from day 2 to day 14 and were normalized on day 21. The clostridia decreased on days 2, 7, and 14 and were normalized on day 21. No Clostridium difficile strains or toxins were detected during the study period. The number of Bacteroides strains was not significantly changed. The solithromycin concentrations in saliva were 0 to 1.2 mg/liter, 0 to 0.5 mg/liter, 0 to 0.5 mg/liter, and 0 to 0.1 mg/liter on days 2, 5, 7, and 9, respectively. The numbers of streptococci decreased on day 2 and were normalized on day 5. The numbers of lactobacilli, prevotellae, fusobacteria, and leptotrichiae decreased from day 2 and were normalized on day 21.

Clostridium difficile recurrences in Stockholm.

Sixty-eight hospital-admitted patients with a first episode of Clostridium difficile infection (CDI) were included and followed up during 1 year. Faeces samples were collected at 1, 2, 6 and 12 months after inclusion and analyzed for the presence of C. difficile toxin B, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped and the MICs of the isolates were determined against eight antimicrobial agents. In 68 patients initially included, antibiotics, clinical signs and co-morbidities were analyzed and 56 were evaluable for recurrences. The mean number of different antibiotics given during 3 months prior to inclusion was 2.6 (range 0-6). Six patients had not received any antibiotics and three of them had diagnosed inflammatory bowel disease. Thirty-two patients (57%) had either a microbiological or clinical recurrence, 16 of whom had clinical recurrences that were confirmed microbiologically (13, 23%) or unconfirmed by culture (3, 5%). Twenty-nine patients were positive in at least one of the follow-up tests, 16 had the same ribotype in follow-up tests, i.e. relapse, and 13 a different ribotype, i.e., reinfection. Most common ribotypes were 078/126, 020, 023, 026, 014/077, 001 and 005. No strain of ribotype 027 was found. Strains ribotype 078/126 and 023 were positive for binary toxin and were the strains most prone to cause recurrence. All strains were sensitive to vancomycin and metronidazole. Patients with recurrences were significantly older (p = 0.02) and all patients had a high burden of comorbidities, which could explain the high fatality rate, 26 (38%) patients died during the 1-year follow-up.

Same Exposure but Two Radically Different Responses to Antibiotics: Resilience of the Salivary Microbiome versus Long-Term Microbial Shifts in Feces.

UNLABELLED: Due to the spread of resistance, antibiotic exposure receives increasing attention. Ecological consequences for the different niches of individual microbiomes are, however, largely ignored. Here, we report the effects of widely used antibiotics (clindamycin, ciprofloxacin, amoxicillin, and minocycline) with different modes of action on the ecology of both the gut and the oral microbiomes in 66 healthy adults from the United Kingdom and Sweden in a two-center randomized placebo-controlled clinical trial. Feces and saliva were collected at baseline, immediately after exposure, and 1, 2, 4, and 12 months after administration of antibiotics or placebo. Sequences of 16S rRNA gene amplicons from all samples and metagenomic shotgun sequences from selected baseline and post-antibiotic-treatment sample pairs were analyzed. Additionally, metagenomic predictions based on 16S rRNA gene amplicon data were performed using PICRUSt. The salivary microbiome was found to be significantly more robust, whereas the antibiotics negatively affected the fecal microbiome: in particular, health-associated butyrate-producing species became strongly underrepresented. Additionally, exposure to different antibiotics enriched genes associated with antibiotic resistance. In conclusion, healthy individuals, exposed to a single antibiotic treatment, undergo considerable microbial shifts and enrichment in antibiotic resistance in their feces, while their salivary microbiome composition remains unexpectedly stable. The health-related consequences for the gut microbiome should increase the awareness of the individual risks involved with antibiotic use, especially in a (diseased) population with an already dysregulated microbiome. On the other hand, understanding the mechanisms behind the resilience of the oral microbiome toward ecological collapse might prove useful in combating microbial dysbiosis elsewhere in the body. IMPORTANCE: Many health care professionals use antibiotic prophylaxis strategies to prevent infection after surgery. This practice is under debate since it enhances the spread of antibiotic resistance. Another important reason to avoid nonessential use of antibiotics, the impact on our microbiome, has hardly received attention. In this study, we assessed the impact of antibiotics on the human microbial ecology at two niches. We followed the oral and gut microbiomes in 66 individuals from before, immediately after, and up to 12 months after exposure to different antibiotic classes. The salivary microbiome recovered quickly and was surprisingly robust toward antibiotic-induced disturbance. The fecal microbiome was severely affected by most antibiotics: for months, health-associated butyrate-producing species became strongly underrepresented. Additionally, there was an enrichment of genes associated with antibiotic resistance. Clearly, even a single antibiotic treatment in healthy individuals contributes to the risk of resistance development and leads to long-lasting detrimental shifts in the gut microbiome.

Multicenter, Double-Blind, Randomized, Phase 2 Study Evaluating the Novel Antibiotic Cadazolid in Patients with Clostridium difficile Infection.

Cadazolid, a novel fluoroquinolone-oxazolidinone antibiotic, exhibits potent in vitro activity against Clostridium difficile, including the epidemic BI/NAP1/027 strain. This multicenter, randomized, double-blind, active reference group, phase 2 study evaluated the efficacy and safety of oral cadazolid in treatment of adult patients with C. difficile infection (CDI). Eligible patients with first occurrence/first recurrence of CDI were randomized 1:1:1:1 to 250, 500, or 1,000 mg cadazolid twice daily (BID) or oral 125 mg vancomycin four times daily (QID) for 10 days. The primary endpoint was clinical cure at test of cure (48 ± 24 h after the end of treatment; modified intent-to-treat population), defined as resolution of diarrhea with no further CDI treatment required. Secondary endpoints included recurrence rate, sustained clinical response (clinical cure without recurrence), and time to diarrhea resolution. Of 84 patients enrolled, 20, 22, 20, and 22 received 250, 500, or 1,000 mg cadazolid BID or 125 mg vancomycin QID, respectively. The primary endpoint was achieved in 76.5% (80% confidence interval [CI], 58.4, 89.3), 80.0% (63.9, 91.0), 68.4% (51.1, 82.5), and 68.2% (52.3, 81.3) of patients, respectively. There was no evidence of a cadazolid dosage-dependent response. Each dosage of cadazolid resulted in a lower recurrence rate than with vancomycin (18.2 to 25.0% versus 50%). Consequently, higher sustained clinical response rates were observed with cadazolid (46.7 to 60.0%) than with vancomycin (33.3%). The times to diarrhea resolution were similar for cadazolid and vancomycin. Cadazolid was well tolerated, with no safety signal observed. The results of this phase 2 study support further clinical development of cadazolid. (This study has been registered in the United States at ClinicalTrials.gov under registration no. NCT01222702 and in Europe with the European Medicines Agency under registration no. EUDRA-CT 2010-020941-29.).

Ecological effect of ceftazidime/avibactam on the normal human intestinal microbiota.

Ceftazidime/avibactam is a new combination of the antibiotic ceftazidime with the novel, non-ß-lactam ß-lactamase inhibitor avibactam. The purpose of the present study was to investigate the effect of ceftazidime/avibactam on the human intestinal microbiota following intravenous (i.v.) administration. Twelve healthy volunteers received ceftazidime/avibactam by i.v. infusion (2000mg ceftazidime and 500mg avibactam) given over 2h every 8h on Days 1-6 (inclusive) and a single dose on Day 7. Faecal samples were collected on Day-1 (pre-dose), during administration on Days 2, 5 and 7 and post-dose on Days 9, 14 and 21. Samples were cultured on non-selective and selective media. The number of Escherichia coli and other enterobacteria decreased significantly during administration of ceftazidime/avibactam, whereas the number of enterococci increased. Lactobacilli, bifidobacteria, clostridia and Bacteroides decreased significantly during ceftazidime/avibactam administration. The effects on lactobacilli, bifidobacteria and Bacteroides were similar in the 12 volunteers, whilst clostridia showed different ecological patterns among the volunteers. Toxigenic Clostridium difficile strains were detected in five volunteers during the study. In four of the volunteers, loose stools were reported as adverse events. Plasma samples were collected on Days -1, 2, 5 and 7. Ceftazidime and avibactam concentrations in plasma (ceftazidime 0-224.2mg/L of plasma and avibactam 0-70.5mg/L of plasma) and faeces (ceftazidime 0-468.2mg/kg of faeces and avibactam 0-146.0mg/kg of faeces) were found by bioassay. New colonising resistant clostridia were found in five volunteers and lactobacilli were found in three volunteers.

Impact of Ciprofloxacin and Clindamycin Administration on Gram-Negative Bacteria Isolated from Healthy Volunteers and Characterization of the Resistance Genes They Harbor.

The aim of this study was to assess the impact of ciprofloxacin, clindamycin, and placebo administration on culturable Gram-negative isolates and the antibiotic resistance genes they harbor. Saliva and fecal samples were collected from healthy human volunteers before and at intervals, up to 1 year after antibiotic administration. Samples were plated on selective and nonselective media to monitor changes in different colony types or bacterial species. Following ciprofloxacin administration, there was a decrease of Escherichia coli in feces and after clindamycin administration a decrease of Bacteroides in feces and Leptotrichia in saliva, which all returned to pretreatment levels within 1 to 4 months. Ciprofloxacin administration also resulted in an increase in ciprofloxacin-resistant Veillonella in saliva, which persisted for 12 months. Additionally, 949 aerobic and anaerobic isolates purified from ciprofloxacin- and clindamycin-containing plates were screened for the presence of resistance genes. Resistance gene carriage was widespread in isolates from all three treatment groups, and no association was observed between genes and antibiotic administration. Although the anaerobic component of the microbiota was not a major reservoir of aerobe-associated antimicrobial resistance (AMR) genes, we detected the sulfonamide resistance gene sul2 in anaerobic isolates. The longitudinal nature of the study allowed identification of distinct Escherichia coli clones harboring multiple resistance genes, including one carrying an extended-spectrum ß-lactamase blaCTX-M group 9 gene, which persisted in the gut for up to 4 months. This study provided insight into the effects of antibiotic administration on healthy microbiota and the diversity of resistance genes harbored therein.

Ecological Effect of Ceftaroline-Avibactam on the Normal Human Intestinal Microbiota.

Ceftaroline-avibactam is a new combination of the antibiotic ceftaroline with a novel non-ß-lactam ß-lactamase inhibitor, avibactam. The purpose of the present study was to investigate the effect of ceftaroline-avibactam on the human intestinal microbiota. Fourteen healthy volunteers received ceftaroline-avibactam (600 mg ceftaroline fosamil and 600 mg avibactam) intravenously over 2 h every 8 h on days 1 to 6 and as a single dose on day 7. Fecal samples were collected on day -1 (within 24 h of the first infusion on day 1) and on days 2, 5, 7, 9, 14, and 21. Escherichia coli numbers decreased during the study and normalized on day 21. An increased number of Klebsiella bacteria appeared on day 14 and normalized on day 21. The number of other enterobacteria decreased during the study, and the number of enterococci decreased from days 2 to 7 and normalized on day 9. Candida numbers increased from days 5 to 9 and normalized after day 14. The number of lactobacilli decreased during the study and recovered on day 14. The number of bifidobacteria decreased on day 2 and normalized on day 21. The number of Bacteroides bacteria was unchanged. Clostridium difficile numbers decreased on days 7 and 9 and increased on days 14 and 21. A toxigenic C. difficile strain was detected in one volunteer on day 21 with no reported adverse events. Plasma samples were collected on days -1, 2, 5, and 7. Ceftaroline and avibactam concentrations were 0 to 34.5 mg/liter and 0 to 61.6 mg/liter, respectively, in plasma and 0 to 35.4 mg/kg and 0 to 98.5 mg/kg, respectively, in feces. (This study is registered in the European Clinical Trials Database [https://eudract.ema.europa.eu/] under number EudraCT 2012 004921-25.).

Determining the Long-term Effect of Antibiotic Administration on the Human Normal Intestinal Microbiota Using Culture and Pyrosequencing Methods.

The purpose of the study was to assess the effect of ciprofloxacin (500 mg twice daily for 10 days) or clindamycin (150 mg 4 times daily for 10 days) on the fecal microbiota of healthy humans for a period of 1 year as compared to placebo. Two different methods, culture and microbiome analysis, were used. Fecal samples were collected for analyses at 6 time-points. The interval needed for the normal microbiota to be normalized after ciprofloxacin or clindamycin treatment differed for various bacterial species. It took 1-12 months to normalize the human microbiota after antibiotic administration, with the most pronounced effect on day 11. Exposure to ciprofloxacin or clindamycin had a strong effect on the diversity of the microbiome, and changes in microbial composition were observed until the 12th month, with the most pronounced microbial shift at month 1. No Clostridium difficile colonization or C. difficile infections were reported. Based on the pyrosequencing results, it appears that clindamycin has more impact than ciprofloxacin on the intestinal microbiota.

Development of antimicrobial resistance in the normal anaerobic microbiota during one year after administration of clindamycin or ciprofloxacin.

Thirty healthy subjects (15 males and 15 females) were randomly assigned in three groups and clindamycin (150 mg qid) or ciprofloxacin (500 mg bid) or placebo was given for a 10-day period. Skin, nasal, saliva, faeces samples were collected at day - 1, day 11, 1 month, 2 months, 4 months and 12 months post administration for microbiological analysis. Ciprofloxacin or clindamycin had no impact on the anaerobic skin microbiota and the proportions of antibiotic resistant anaerobic bacteria were similar as in the placebo group. Ciprofloxacin had impact on the Propionibacterium acnes in the nasal microbiota that normalized after 1 month, however, ciprofloxacin-resistant P. acnes strains increased at month 2 and month 12. Clindamycin had no impact on the nasal microbiota. In the oropharyngeal microbiota, a higher proportion of ciprofloxacin resistant Veillonella was found, it lasting up to 12 months post dosing. In the clindamycin group, clindamycin-resistant Prevotella spp. were found in increased proportions compared to placebo at various time points except month 4 in the saliva samples. The relative proportion of ciprofloxacin-resistant Bifidobacteria increased in the faecal samples on day 11, 1 month, 4 months and 12 months post dosing compared to placebo. The proportion of clindamycin-resistant Bacteroides spp. increased at 1, 2, 4 and 12 months post dosing compared to placebo in the faecal samples. No Clostridium difficile was recovered from any of the samples from any of the volunteers at any visit. The concentrations of ciprofloxacin or clindamycin in the faeces were higher than the MICs for most of the organisms present in the normal microbiota. No obvious correlation between the groups in resistant patterns for anaerobic bacteria was observed. In conclusion, based on the microbiological data of the microbiota as well as the results of the bioassays for ciprofloxacin and clindamycin concentrations in the faecal samples, oral administration of ciprofloxacin and clindamycin has an impact on the anaerobic microbiota and may have a long-term effect on the development and persistence of antibiotic-resistant anaerobes in the normal microbiota.

Risk factors of Clostridium difficile infections among patients in a university hospital in Shanghai, China.

Clostridium difficile infection (CDI) is an increasing concern in China. However, the risk factors of CDI are rarely reported in the Chinese population. A prospective observational study was therefore conducted among patients with hospital-acquired C. difficile diarrhoea and the risk factors of CDI in a retrospective case-control study. The CDI patients were compared with the non-CDI diarrhoeal patients and those without diarrhoea, respectively. The recurrent CDI patients were compared with the corresponding non-recurrent CDI patients and those without diarrhoea, respectively. Overall, of the 240 patients with hospital-acquired diarrhoea 90 (37.5%) were diagnosed as CDI, and 12 (13.3%) of the 90 CDI patients experienced recurrence. Multivariate analysis indicated that renal disease, malignancy, hypoalbuminemia, prior antibiotic treatment, chemotherapy, nasogastric tube use, length of stay>14 days and intra-abdominal surgery, defined daily dose of antimicrobial agents≥19, prior use of more than three antimicrobial agents, and use of carbapenems were independent risk factors for the first episode of CDI. Use of laxatives, the first- and second-generation narrow-spectrum cephalosporins or metronidazole was identified as protective factors. It is necessary to make testing of C. difficile available as a routine practice and control these risk factors in Chinese hospitals to avoid CDI outbreaks.