Risk factors and outcome due to extended-spectrum ß-lactamase-producing uropathogenic Escherichia coli in community-onset bloodstream infections: A ten-year cohort study in Sweden.

OBJECTIVE: To study clinical outcome and risk factors associated with extended-spectrum ß-lactamase (ESBL)-producing uropathogenic Escherichia coli (UPEC) in community-onset bloodstream infections (CO-BSI). METHODS: This was a population-based cohort study including patients with pheno- and genotype-matched ESBL-producing E. coli and non-ESBL- E. coli in urine and blood samples collected in 2009-2018 in southeast Sweden. Seventy-seven episodes of ESBL-UPEC satisfying the inclusion criteria were matched 1:1 with 77 non-ESBL-UPEC for age, gender, and year of culture. RESULTS: The most common ST-type and ESBL gene was ST131 (55%), and blaCTX-M-15 (47%), respectively. Risk factors for ESBL-UPEC were: previous genitourinary invasive procedure (RR 4.66; p = 0.005) or history of ESBL-producing E. coli (RR 12.14; p = 0.024). There was significant difference between ESBL-UPEC and non-ESBL-UPEC regarding time to microbiologically appropriate antibiotic therapy (27:15 h vs. 02:14 h; p = <0.001) and hospital days (9 vs. 5; p = <0.001), but no difference in 30-day mortality (3% vs. 3%; p = >0.999) or sepsis within 36 hours (51% vs. 62%; p = 0.623) was observed. CONCLUSION: The predominant risk factors for ESBL-UPEC were history of ESBL-Ec infection and history of genitourinary invasive procedure. The overall mortality was low and the delay in appropriate antibiotic therapy did not increase the risk for 30-day mortality or risk for sepsis within 36 hours among patients infected with ESBL UPEC. However, these results must be regarded with some degree of caution due to the small sample size.

Low incidence of antibiotic-resistant bacteria in south-east Sweden: An epidemiologic study on 9268 cases of bloodstream infection.

OBJECTIVES: The aim of this study was to investigate the epidemiology of bloodstream infections (BSI) in a Swedish setting, with focus on risk factors for BSI-associated mortality. METHODS: A 9-year (2008-2016) retrospective cohort study from electronic records of episodes of bacteremia amongst hospitalized patients in the county of Östergötland, Sweden was conducted. Data on episodes of BSI including microorganisms, antibiotic susceptibility, gender, age, hospital admissions, comorbidity, mortality and aggregated antimicrobial consumption (DDD /1,000 inhabitants/day) were collected and analyzed. Multidrug resistance (MDR) was defined as resistance to at least three groups of antibiotics. MDR bacteria and MRSA, ESBL-producing Enterobacteriaceae, vancomycin-resistant enterococci not fulfilling the MDR criteria were all defined as antimicrobial-resistant (AMR) bacteria and included in the statistical analysis of risk factors for mortality. RESULTS: In all, 9,268 cases of BSI were found. The overall 30-day all-cause mortality in the group of patients with BSI was 13%. The incidence of BSI and associated 30-day all-cause mortality per 100,000 hospital admissions increased by 66% and 17% respectively during the nine-year study period. The most common species were Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae and Enterococcus faecalis. Independent risk factors for 30-day mortality were age (RR: 1.02 (CI: 1.02-1.03)) and 1, 2 or ≥3 comorbidities RR: 2.06 (CI: 1.68-2.52), 2.79 (CI: 2.27-3.42) and 2.82 (CI: 2.31-3.45) respectively. Almost 3% (n = 245) of all BSIs were caused by AMR bacteria increasing from 12 to 47 per 100,000 hospital admissions 2008-2016 (p = 0.01), but this was not associated with a corresponding increase in mortality risk (RR: 0.89 (CI: 0.81-0.97)). CONCLUSION: Comorbidity was the predominant risk factor for 30-day all-cause mortality associated with BSI in this study. The burden of AMR was low and not associated with increased mortality. Patients with BSIs caused by AMR bacteria (MDR, MRSA, ESBL and VRE) were younger, had fewer comorbidities, and the 30-day all-cause mortality was lower in this group.

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.

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.

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.

In vitro activity of MCB3681 against Clostridium difficile strains.

One hundred fourteen Clostridium difficile strains were collected from 67 patients and analyzed for the presence of C. difficile toxin B by the cell cytotoxoicity neutralization assay, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped. The MICs of the isolates were determined against MCB3681 and nine other antimicrobial agents by the agar dilution method. All isolates were positive for toxin B as well as for toxin A and B genes. In addition, 13 isolates were positive for the binary toxin genes. Thirty-two different ribotypes were identified. No strain of ribotype 027 was found. All 114 isolates were sensitive to MCB3681 (0.008-0.5 mg/l), cadazolid (0.064-0.5 mg/l), fidaxomicin (0.008-0.125 mg/l), metronidazole (0.125-2 mg/l), vancomycin (0.125-1 mg/l) and tigecycline (0.032-0.25 mg/l). Three isolates were resistant to linezolid (8 mg/l), 12 isolates were resistant to moxifloxacin (8-32 mg/l), 87 isolates were resistant to clindamycin (8-256 mg/l) and 107 isolates were resistant to ciprofloxacin (8-256 mg/l). No association between toxins A, B and binary toxin, ribotypes and the sensitivity to MCB3681 could be found. MCB3681 has a potent in vitro activity against C. difficile.

Ecological impact of MCB3837 on the normal human microbiota.

MCB3837 is a novel, water-soluble, injectable prodrug that is rapidly converted to the active substance MCB3681 in vivo following intravenous (i.v.) administration. Both MCB3837 and MCB3681 are oxazolidinone-quinolone hybrid molecules. The purpose of the present study was to investigate the effect of MCB3681 on the human skin, nose, oropharyngeal and intestinal microbiota following administration of MCB3837. Twelve healthy male subjects received i.v. MCB3837 (6 mg/kg body weight) once daily for 5 days. Skin, nose, saliva and faecal samples were collected on Day -1 (pre dose), during administration on Days 2 and 5, and post dose on Days 8, 12 and 19. Micro-organisms were identified to genus level. No measurable concentrations of MCB3681 were found in any saliva samples or in the faecal samples on Day -1. On Day 2, 10 volunteers had faecal MCB3681 concentrations between 16.5 mg/kg faeces and 275.1mg/kg faeces; no MCB3681 in faeces could be detected in two of the volunteers. On Day 5, all volunteers had faecal concentrations of MCB3681 ranging from 98.9 to 226.3 mg/kg. MCB3681 caused no ecological changes in the skin, nasal and oropharyngeal microbiota. The numbers of enterococci, bifidobacteria, lactobacilli and clostridia decreased in the intestinal microbiota during administration of the drug. Numbers of Escherichia coli, other enterobacteria and Candida were not affected during the study. There was no impact on the number of Bacteroides. The faecal microbiota was normalised on Day 19. No new colonising aerobic or anaerobic Gram-positive bacteria with MCB3681 minimum inhibitory concentrations of ≥4 mg/L were found.

In vitro activity of cadazolid against Clostridium difficile strains isolated from primary and recurrent infections in Stockholm, Sweden.

One hundred thirty-three Clostridium difficile strains were collected from 71 patients and analyzed for the presence of C. difficile toxin B by the cell cytotoxicity neutralization assay, genes for toxin A, toxin B, binary toxin and TcdC deletion by PCR. All strains were also PCR-ribotyped and analyzed for sporulation frequency. The MICs of the isolates were determined against cadazolid and seven other antimicrobial agents by the agar dilution method. All isolates were positive for toxin B by the cell cytotoxicity neutralization assay. One hundred fourteen isolates were positive for toxin A and B and 16 isolates were positive for toxin A, toxin B and binary toxin by PCR. Three isolates were negative for toxin A but positive for toxin B. Thirty-three different ribotypes were identified. No strain of ribotype 027 was found. No differences in sporulation were noticed between the primary and recurrent isolates. All 133 isolates were sensitive to cadazolid (0.064-0.5 mg/l), fidaxomicin (0.008-0.125 mg/l), metronidazole (0.125-2 mg/l), vancomycin (0.125-1 mg/l) and tigecycline (0.032-0.25 mg/l). Three isolates were resistant to linezolid (8 mg/l), 15 isolates were resistant to moxifloxacin (8-32 mg/l) and 103 isolates were resistant to clindamycin (8-256 mg/l). No association between toxins A, B and binary toxin, ribotypes or the sporulation and the sensitivity to cadazolid could be found. Cadazolid has a potent in vitro activity against C. difficile.

Ecological impact of doxycycline at low dose on normal oropharyngeal and intestinal microflora.

This study included 34 healthy volunteers (16 male and 18 female) aged 19-37 years, of whom 17 received doxycycline 40 mg capsules orally once daily (o.d.) and 17 received placebo 40 mg capsules orally o.d. for 16 weeks. Plasma, saliva and faecal samples were collected before drug administration and at 4, 8, 16 and 20 weeks. Plasma samples were assayed for doxycycline concentrations, and saliva and faecal samples were investigated for doxycycline concentrations and microbiological analyses. Plasma concentrations of doxycycline in the doxycycline group were as follows: baseline visit (2 h), 0.20-0.61 mg/L; 4-week visit, 0.30-1.04 mg/L; 8-week visit, 0.43-1.49 mg/L; 16-week visit, 0.32-1.12 mg/L; and 20-week visit 0 mg/L. No doxycycline was detected in plasma in the placebo group. No doxycycline concentrations in the saliva samples were found in the doxycycline or placebo groups at the five visits. Faecal concentrations of doxycycline in the doxycycline group were as follows: baseline visit, 0 mg/kg; 4-week visit, 0-3.71 mg/kg; 8-week visit, 0-1.85 mg/kg; 16-week visit, 0-4.10 mg/kg; and 20-week visit, 0 mg/kg. No doxycycline faecal concentrations were detected in the placebo group. Minor effects on the aerobic and anaerobic oropharyngeal microflora were observed both in the doxycycline and placebo groups. There were minor changes in the number of enterococci and Escherichia coli in the doxycycline and placebo groups. The anaerobic intestinal microflora in the doxycycline and placebo groups was not changed, and no Clostridium difficile strains were isolated.

Effect of new antimicrobial agents on the ecological balance of human microflora.

The human normal microflora is relatively stable at each ecological habitat under normal circumstances and acts as a barrier against colonization by potentially pathogenic microorganisms and against overgrowth of already present opportunistic microorganisms. Administration of antimicrobial agents causes disturbances in the ecological balance between the host and the normal microflora. The risk of emergence and spread of resistant strains between patients and dissemination of resistant determinants between microorganisms is reduced if colonization resistance is not disturbed by antimicrobial agents. In this article, the potential ecological effects of administration of new antimicrobial agents on the intestinal and oropharyngeal microflora are summarized. The review is based on clinical studies published during the past 10 years.

Effect of telavancin on human intestinal microflora.

Telavancin is a new lipoglycopeptide antibiotic for the treatment of Gram-positive infections. It has a dual mechanism of action by inhibiting bacterial cell wall synthesis and disrupting the bacterial plasma membrane. The purpose of the present study was to investigate the effect of administration of telavancin on the human intestinal microflora. Thirteen healthy subjects (six males and seven females; age range 18-40 years) received 10mg/kg body weight telavancin by intravenous infusion over a 60-min period once every 24h for 7 days. Plasma and urine were collected on Days 5, 6 and 7 for pharmacokinetic analysis of telavancin. Faecal samples were collected on Days -1 (pre-dose), 2, 5, 7, 9, 14 and 21. Faecal specimens were cultured on non-selective and selective media. Different colony types were counted, isolated in pure culture and identified to genus level. No measurable concentrations of telavancin were found in faeces. No significant effects on the number of Enterobacteriaceae, enterococci, Candida albicans, bifidobacteria, lactobacilli, clostridia and Bacteroides spp. were observed during the study period. No Clostridium difficile strains or toxins were found. No new colonising aerobic and anaerobic Gram-positive bacteria with telavancin minimum inhibitory concentrations of ≥ 2 mg/L were found. Based on the microbiological data, telavancin has no significant ecological impact on the human intestinal microflora.

Effect of ceftobiprole on the normal human intestinal microflora.

Ceftobiprole is a new broad-spectrum pyrrolidinone cephem active against meticillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis and Gram-negative bacteria such as Enterobacteriaceae and Pseudomonas spp. The purpose of the present study was to investigate the effect of administration of ceftobiprole on the normal intestinal microflora. Twelve healthy subjects (six males and six females) aged 20-31 years received ceftobiprole 500 mg by intravenous infusion every 8h for 7 days. Plasma samples were collected on Days -1, 1, 4, 7, 10, 14 and 21 for determination of drug concentration by biological and chemical methods. Faecal samples were collected on Days -1, 2, 4, 7, 10, 14 and 21. For analysis of the microflora, faecal specimens were cultured on non-selective and selective media. Different colony types were counted, isolated in pure culture and identified to genus level. All new colonising aerobic and anaerobic bacteria were tested for susceptibility to ceftobiprole. Plasma concentrations of ceftobiprole 10 min after completion of infusion were as follows: Day 1, 14.7-23.6 mg/L; Day 4, 15.9-24.5 mg/L; and Day 7, 15.9-23.9 mg/L. No ceftobiprole was detected in plasma on Days -1, 10, 14 and 21. No measurable concentrations of ceftobiprole were found in faeces on Days -1, 2, 4, 7, 10, 14 and 21. There were minor changes in the numbers of enteric bacteria, enterococci and Candida albicans and there were moderate changes in the numbers of bifidobacteria, lactobacilli, clostridia and Bacteroides spp. during the same period. No Clostridium difficile strains or toxins were found. No new colonising aerobic and anaerobic bacteria with ceftobiprole minimum inhibitory concentrations of ≥ 4 mg/L were found. Ceftobiprole had no significant ecological impact on the human intestinal microflora.