Antimicrobial resistance progression in the United Kingdom: A temporal comparison of Clostridioides difficile antimicrobial susceptibilities

OBJECTIVES

Clostridioides difficile (CD) is widely reported as one of the most prevalent multi-drug resistant (MDR) organisms. Assessment of temporally disparate isolate collections can give valuable epidemiological data to further the understanding of antimicrobial resistance progression.

METHODS

A collection of 75 CD isolates (1980-86) was characterised by PCR ribotyping, cell cytotoxicity assay and susceptibility testing with a panel of 16 antimicrobials and compared to a modern surveillance collection consisting of 416 UK isolates (2012-2016). Agar-incorporation was performed to ascertain susceptibility data for vancomycin, metronidazole, rifampicin, fidaxomicin, moxifloxacin, clindamycin, imipenem, chloramphenicol, tigecycline, linezolid, ciprofloxacin, piperacillin/tazobactam, ceftriaxone, amoxicillin, tetracycline and erythromycin. Genomes were obtained using Illumina HiSeq3000 sequencing and assembled using CLC Genomics Workbench. Resistance genes were identified using the Comprehensive Antibiotic Research Database's Resistance Gene Identifier and ResFinder3.0.

RESULTS

Twenty-six known and one previously unobserved ribotype (RT) were detected. RT015 and RT020 dominated; 21.3% and 17.3%, respectively. Three moxifloxacin resistant (16-32 mg/L) RT027 isolates were recovered, pre-dating the earliest reports of this phenotype/genotype. Phenotypic resistance was observed to moxifloxacin (9.3% of isolates), ciprofloxacin (100%), erythromycin (17.3%), tetracycline (9.3%), linezolid and chloramphenicol (4.0%). Phenotypic comparisons with modern strains revealed increasing minimum inhibitory concentrations (MIC), with MIC₅₀ elevations of one doubling-dilution for the majority of compounds, excluding clindamycin and imipenem. Moxifloxacin MIC₉₀ comparisons revealed a two doubling-dilution increase between temporal isolate collections. Historical genomes revealed twenty different resistance determinants, including ermB (8.0% of isolates), tetM (9.3%), cfr (5.3%) and gyrA substitution Thr-82→Ile (9.3%). Seventeen isolates (22.7%) were resistant to ≥3 compounds (MDR), demonstrating ten different combinations. Intra-RT diversity was observed.

CONCLUSIONS

Antibiotic resistance in CD has increased since the early 1980s, across the majority of classes. Moxifloxacin resistance determinants may pre-date its introduction.

Antimicrobial resistance in Clostridioides (Clostridium) difficile derived from humans: a systematic review and meta-analysis

Background

Clostridioides (Clostridium) difficile is an important pathogen of healthcare- associated diarrhea, however, an increase in the occurrence of C. difficile infection (CDI) outside hospital settings has been reported. The accumulation of antimicrobial resistance in C. difficile can increase the risk of CDI development and/or its spread. The limited number of antimicrobials for the treatment of CDI is matter of some concern.

Objectives

In order to summarize the data on antimicrobial resistance to C. difficile derived from humans, a systematic review and meta-analysis were performed.

Methods

We searched five bibliographic databases: (MEDLINE [PubMed], Scopus, Embase, Cochrane Library and Web of Science) for studies that focused on antimicrobial susceptibility testing in C. difficile and were published between 1992 and 2019. The weighted pooled resistance (WPR) for each antimicrobial agent was calculated using a random- effects model.

Results

A total of 111 studies were included. The WPR for metronidazole and vancomycin was 1.0% (95% CI 0–3%) and 1% (95% CI 0–2%) for the breakpoint > 2 mg/L and 0% (95% CI 0%) for breakpoint ≥32 μg/ml. Rifampin and tigecycline had a WPRs of 37.0% (95% CI 18–58%) and 1% (95% CI 0–3%), respectively. The WPRs for the other antimicrobials were as follows: ciprofloxacin 95% (95% CI 85–100%), moxifloxacin 32% (95% CI 25–40%), clindamycin 59% (95% CI 53–65%), amoxicillin/clavulanate 0% (0–0%), piperacillin/tazobactam 0% (0–0%) and ceftriaxone 47% (95% CI 29–65%). Tetracycline had a WPR 20% (95% CI 14–27%) and meropenem showed 0% (95% CI 0–1%); resistance to fidaxomicin was reported in one isolate (0.08%).

Conclusion

Resistance to metronidazole, vancomycin, fidaxomicin, meropenem and piperacillin/tazobactam is reported rarely. From the alternative CDI drug treatments, tigecycline had a lower resistance rate than rifampin. The high-risk antimicrobials for CDI development showed a high level of resistance, the highest was seen in the second generation of fluoroquinolones and clindamycin; amoxicillin/clavulanate showed almost no resistance. Tetracycline resistance was present in one fifth of human clinical C. difficile isolates.

Molecular epidemiology of predominant and emerging Clostridioides difficile ribotypes

There has been an increase in the incidence and severity of Clostridioides difficile infection (CDI) worldwide, and strategies to control, monitor, and diminish the associated morbidity and mortality have been developed. Several typing methods have been used for typing of isolates and studying the epidemiology of CDI; serotyping was the first typing method, but then was replaced by pulsed-field gel electrophoresis (PFGE). PCR ribotyping is now the gold standard method; however, multi locus sequence typing (MLST) schemes have been developed. New sequencing technologies have allowed comparing whole bacterial genomes to address genetic relatedness with a high level of resolution and discriminatory power to distinguish between closely related strains. Here, we review the most frequent C. difficile ribotypes reported worldwide, with a focus on their epidemiology and genetic characteristics.

Clostridium difficile infection: Evolution, phylogeny and molecular epidemiology

Over the recent decades, Clostridium difficile infection (CDI) has emerged as a global public health threat. Despite growing attention, C. difficile remains a poorly understood pathogen, however, the exquisite sensitivity offered by next generation sequencing (NGS) technology has enabled analysis of the genome of C. difficile, giving us access to massive genomic data on factors such as virulence, evolution, and genetic relatedness within C. difficile groups. NGS has also demonstrated excellence in investigations of outbreaks and disease transmission, in both small and large-scale applications. This review summarizes the molecular epidemiology, evolution, and phylogeny of C. difficile, one of the most important pathogens worldwide in the current antibiotic resistance era.

U.S.-Based National Sentinel Surveillance Study for the Epidemiology of Clostridium difficile-Associated Diarrheal Isolates and Their Susceptibility to Fidaxomicin

In 2011 a surveillance study for the susceptibility to fidaxomicin and epidemiology of Clostridium difficile isolates in the United States was undertaken in seven geographically dispersed medical centers. This report encompasses baseline surveillance in 2011 and 2012 on 925 isolates. A convenience sample of C. difficile isolates or toxin positive stools from patients were referred to a central laboratory. Antimicrobial susceptibility was determined by agar dilution (CLSI M11-A8). Clinical and Laboratory Standards Institute (CLSI), Food and Drug Administration, or European Union of Clinical Antimicrobial Susceptibility Testing (EUCAST) breakpoints were applied where applicable. Toxin gene profiles were characterized by multiplex PCR on each isolate. A random sample of 322 strains, stratified by institution, underwent restriction endonuclease analysis (REA). The fidaxomicin MIC90 was 0.5 μg/ml for all isolates regardless of REA type or toxin gene profile, and all isolates were inhibited at ≤1.0 μg/ml. By REA typing, BI strains represented 25.5% of the isolates. The toxin gene profile of tcdA, tcdB, and cdtA/B positive with a tcdC 18-bp deletion correlated with BI REA group. Moxifloxacin and clindamycin resistance was increased among either BI or binary toxin-positive isolates. Metronidazole and vancomycin showed reduced susceptibility (EUCAST criteria) in these isolates. Geographic variations in susceptibility, REA group and binary toxin gene presence were observed. Fidaxomicin activity against C. difficile isolated in a national surveillance study did not change more than 1 year after licensure. This analysis provides baseline results for future comparisons.

A prospective study of community-associated Clostridium difficile infections: the role of antibiotics and co-infections

OBJECTIVES

This prospective study was performed to determine the incidence, risk factors, severity and outcomes of community-associated Clostridium difficile infection (CA-CDI) in the SE of Scotland.

METHODS

All patients (335) diagnosed with laboratory confirmed CDI in the city of Edinburgh, East Lothian and Midlothian regions of Scotland between August 2010 and July 2011 were followed up for one year after diagnosis. Clinical details and laboratory markers were recorded. Stool samples were tested for C. difficile, other bacterial pathogens and norovirus. Molecular epidemiology of C. difficile isolates was studied by PCR-ribotyping.

RESULTS

Of the total 335 confirmed CDI cases, PCR-ribotype 001 was the commonest (14.1%), followed by PCR-ribotypes 078 (12.9%) and 015 (11.7%), respectively. CA-CDI represented 12.5% of the cases. In these, PCR-ribotype 078 was the commonest (19.0%), followed by PCR-ribotypes 014/020 (16.7%), PCR-ribotype 015 (14.3% and PCR-ribotype 001 (11.9%). A lower Charlson co-morbidity index and a lower age was observed in the CA-CDI group as was total number of different antibiotic classes whereas age >75 was more common in the HA-CDI group. On multivariable analysis presence of PCR-ribotype 078 was significantly associated with community acquisition (p = 0.006) whereas a greater proportion of immunosuppressed patients and those on antibiotics 8 weeks preceding diagnosis (p = 0.035 and p = 0.005 respectively) were found among HA-CDI cases. Charlson co-morbidity index, number of different antibiotics given in the eight weeks preceding onset, severity of infection and rural residence were not significantly different between the two groups.

CONCLUSION

This study demonstrates that patients with CA-CDI may also present with severe infection, are less likely to receive antibiotics prior to CDI, more likely to be younger in age and have a greater proportion of PCR-ribotype 078 compared with CDI acquired in a hospital setting. Hence a high level of vigilance must be maintained to detect CDI cases which present in the community without the traditional predisposing factors.

Characterization of temperate phages infecting Clostridium difficile isolates of human and animal origins

Clostridium difficile is a Gram-positive pathogen infecting humans and animals. Recent studies suggest that animals could represent potential reservoirs of C. difficile that could then transfer to humans. Temperate phages contribute to the evolution of most bacteria, for example, by promoting the transduction of virulence, fitness, and antibiotic resistance genes. In C. difficile, little is known about their role, mainly because suitable propagating hosts and conditions are lacking. Here we report the isolation, propagation, and preliminary characterization of nine temperate phages from animal and human C. difficile isolates. Prophages were induced by UV light from 58 C. difficile isolates of animal and human origins. Using soft agar overlays with 27 different C. difficile test strains, we isolated and further propagated nine temperate phages: two from horse isolates (ΦCD481-1 and ΦCD481-2), three from dog isolates (ΦCD505, ΦCD506, and ΦCD508), and four from human isolates (ΦCD24-2, ΦCD111, ΦCD146, and ΦCD526). Two phages are members of the Siphoviridae family (ΦCD111 and ΦCD146), while the others are Myoviridae phages. Pulsed-field gel electrophoresis and restriction enzyme analyses showed that all of the phages had unique double-stranded DNA genomes of 30 to 60 kb. Phages induced from human C. difficile isolates, especially the members of the Siphoviridae family, had a broader host range than phages from animal C. difficile isolates. Nevertheless, most of the phages could infect both human and animal strains. Phage transduction of antibiotic resistance was recently reported in C. difficile. Our findings therefore call for further investigation of the potential risk of transduction between animal and human C. difficile isolates.

Comparison of antimicrobial susceptibility among Clostridium difficile isolated from an integrated human and swine population in Texas

Clostridium difficile can be a major problem in hospitals because the bacterium primarily affects individuals with an altered intestinal flora; this largely occurs through prolonged antibiotic use. Proposed sources of increased community-acquired infections are food animals and retail meats. The objective of this study was to compare the antimicrobial resistance patterns of C. difficile isolated from a closed, integrated population of humans and swine to increase understanding of the bacterium in these populations. Swine fecal samples were collected from a vertically flowing swine population consisting of farrowing, nursery, breeding, and grower/finisher production groups. Human wastewater samples were collected from swine worker and nonworker occupational group cohorts. Antimicrobial susceptibility testing was performed on 523 C. difficile strains from the population using the commercially available agar diffusion Epsilometer test (Etest(®)) for 11 different antimicrobials. All of the swine and human strains were susceptible to amoxicillin/clavulanic acid, piperacillin/tazobactam, and vancomycin. In addition, all of the human strains were susceptible to chloramphenicol. The majority of the human and swine strains were resistant to cefoxitin and ciprofloxacin. Statistically significant differences in antimicrobial susceptibility were found among the swine production groups for ciprofloxacin, tetracycline, amoxicillin/clavulanic acid, and clindamycin. No significant differences in antimicrobial susceptibility were found across human occupational group cohorts. We found that 8.3% of the swine strains and 13.3% of the human strains exhibited resistance to metronidazole. The finding of differences in susceptibility patterns between human and swine strains of C. difficile provides evidence that transmission between host species in this integrated population is unlikely.

The changing faces of Clostridium difficile: a personal reflection of the past 34 years

Late in 1978 my boss gave me a folder with "Clostridium difficile (diffikilé)" written on it. Inside were a few recent and now classic papers by Bartlett, Larson and co. It was suggested that this might be an interesting research topic. So began a continuing adventure which has resulted in at least 50 publications from my group. Over the years we have made several important contributions to the field. Beginning in 1982 we showed that C. difficile was a common cause of community-acquired infection! During the next few years we did extensive structural studies on the bacterium. This culminated in 1984 with a fingerprinting study (by immunoblotting surface antigens), on Swedish strains supplied by Carl-Erik Nord, which was probably the first study to demonstrate that C. difficile was really an infectious agent. This was later reinforced with strains sent from Amsterdam by Ed Kuijper. Later in the 1980s, in a study of recurrent disease, we showed that ca. 50% of recurrences were due to infection with a different strain. During my term as chair of the European Study Group for C. difficile, we began to define the status of C. difficile infection (CDI) in Europe and develop guidance for diagnosis and treatment. Recently we utilised our extensive culture collection, with isolates from the 1970s to the present, to observe how epidemiology has been driven largely by antibiotic usage. We have now come full circle: in the early years C. difficile infection was caused by many different strains. Then in the period beginning in the 1990s, characterised by often-large outbreaks and poor infection control, disease was caused by a few endemic strains highlighted by the 027/NAP1/BI pandemic. Now in a much-improved local situation, we are seeing again that the majority of cases (largely sporadic) is caused by multiple types. Current studies range from molecular studies on toxin and spore production, immune responses, novel observations on CDI in children, to what is the best way of decontaminating the anaerobe laboratory.

Sensitivity to antibiotics of Clostridium difficile toxigenic nosocomial strains

Clostridium difficile is the etiological agent of diarrhoea and colitis, especially in elderly patients. The incidence of these diseases has increased during the last 10 years. Emergence of so-called hypervirulent strains is considered as one of the main factors responsible for the more severe disease and changed profile of sensitivity to antimicrobial agents. The aim of this work was to determine the sensitivity profile of toxigenic strains of C. difficile in the Czech Republic in 2011-2012 to selected antibiotics. The antibiotics clindamycin, metronidazole, vancomycin and amoxicillin with clavulanic acid were used for this purpose. Isolates cultured on Brazier's C. difficile selective agar were analysed for the presence of toxin genes using Xpert detection system. Xpert analysis revealed that 33 strains carried the genes for toxins tcdB, cdt and tcdCΔ117, thus showing characteristics typical for the hypervirulent ribotype 027/PFGE type NAP1/REA type B1. The remaining 29 strains carried only the gene for toxin B (tcdB) and not cdt and tcdCΔ117. Our results indicate the higher susceptibility of C. difficile hypertoxigenic strains to three out of four tested antibiotics (except vancomycin) than it is for the other toxigenic strains. We found that only 10.34% of other toxigenic strains were resistant to clindamycin, and no resistance was found in all other cases. All the isolates were sensitive to amoxicillin/clavulanic acid in vitro. However, its use is not recommended for therapy of infections caused by C. difficile.

Antimicrobial susceptibility of animal and human isolates of Clostridium difficile by broth microdilution

A total of 188 human (n = 92) and animal (n = 96) isolates of Clostridium difficile of different PCR ribotypes were screened for susceptibility to 30 antimicrobials using broth microdilution. When comparing the prevalence of antimicrobial resistance, the isolates of animal origin were significantly more often resistant to oxacillin, gentamicin and trimethoprim/sulfamethoxazole (P<0.01). The most significant difference between the animal and human populations (P = 0.0006) was found in the level of imipenem resistance, with a prevalence of 53.3 % in isolates of human origin and 28.1 % in isolates of animal origin. Overall, the results show similar MICs for the majority of tested antimicrobials for isolates from human and animal sources, which were collected from the same geographical region and in the same time interval. This supports the hypothesis that C. difficile could be transmissible between human and animal hosts. Resistant isolates have been found in all animal species tested, including food and companion animals, and also among non-toxigenic isolates. The isolates of the most prevalent PCR ribotype 014/020 had low resistance rates for moxifloxacin, erythromycin, rifampicin and daptomycin, but a high resistance rate for imipenem. Multiresistant strains were found in animals and humans, belonging to PCR ribotypes 012, 017, 027, 045, 046, 078 and 150, and also to non-toxigenic strains of PCR ribotypes 010 and SLO 080.

Antimicrobial susceptibility of clostridium difficile clinical isolates in iran

Background

Clostridium difficile infection (CDI) is major growing problem in hospitals and its high incidence has been reported in recent years.

Objectives

The aim of this study was to investigate the antimicrobial susceptibility patterns of C. difficile clinical isolates against antibiotics commonly used for treatment CDI in hospitalized patients.

Material and Methods

During a 12 month study, 75 C. difficile isolates were collected from 390 patients with CDI. All samples were treated with alcohol and yeast extract broth. The treated suspensions were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) supplemented with 5% sheep blood and incubated in anaerobic conditions, at 37 °C for 5 days. Cdd-3, tcdA and tcdB genes were identified using PCR assay.

Results

The prevalence of A⁺B⁺ , A⁺ B^- and A^- B⁺ strains were 64(85.3%), 5(6.7%) and 6(8%) respectively. In vitro susceptibility of 75 clinical isolates of C. difficile to 5 antimicrobial agents, including metronidazole, vancomycin, clindamycin, erythromycin and cefotaxime were investigated by Clinical and Laboratory Standards Institute (CLSI) agar dilution method. Metronidazole and vancomycin had good activity against C. difficile isolates with MIC90s of 2 and 1 µg/ml, respectively. Seventy one (94.6%) of strains was inhibited by concentrations that did not exceed 2µg/ml for metronidazole. Resistant to metronidazole observed in 5.3% of isolates. Forty three (57.3%) of the isolates were resistant to erythromycin. Of 43 resistant strains to erythromycin, 9 (12%) isolates had high-level MIC of more than 64 µg/ml. All strains were resistant to cefotaxime. Sixty seven (89.3%) isolates were resistant to clindamycin (MIC90s > 256 µg/ml) and only 6.7% were sensitive to clindamycin. Multidrug-resistant (three or more antibiotics) was seen in 36(48%) isolates.

Conclusions

Metronidazole and vancomycin still seem to be most effective drugs for treatment CDI.

Characterization of swine isolates of Clostridium difficile in Spain: a potential source of epidemic multidrug resistant strains?

Clostridium difficile is an emerging pathogen for humans and animals and there is concern about the possibility that livestock might serve as a reservoir of epidemic strains. In Spain, ribotype 078 is one of the most prevalent in human episodes of C. difficile infection, but the distribution of this and other ribotypes in animals is yet unknown. We present the first report on the ribotype distribution and antimicrobial susceptibility of C. difficile in swine in Spain. A total of 144 isolates were PCR ribotyped, and their MIC values for 13 antimicrobial agents were determined using the Etest. Toxins A and B production was assessed using a commercial immunoassay and, in the case of toxin B, a specific cytotoxicity test. Our results show a high prevalence of the toxigenic 078 ribotype (94.4%) and multidrug resistance (49.3%) among the studied isolates. A minority of isolates (5.6%) belonged to a mostly non-toxinogenic ribotype. All isolates were resistant to the fluoroquinolone ciprofloxacin, but susceptible to daptomycin, linezolid, meropenem, rifampicin, teicoplanin, tigecycline, metronidazole and vancomycin. Resistance to clindamycin, ertapenem, erythromycin and moxifloxacin was common (≥27.8% in all cases). Resistance rates for the different antibiotics tested were in all cases independent from the ribotype of isolates and the host's condition (diarrheic or non-diarrheic), but erythromycin and moxifloxacin resistance was associated with the geographic origin of isolates. Metronidazole heteroresistance was found among animal isolates of C. difficile. Our results highlight the role of livestock as a potential source of epidemic multidrug resistant strains in Spain.

Molecular epidemiology and resistance profiles of Clostridium difficile in a tertiary care hospital in Spain

Epidemiological surveillance of Clostridium difficile infection has gained importance in recent years as a result of the rapid spread of epidemic strains, including hypervirulent strains and strains with reduced susceptibility to antimicrobials. The molecular epidemiology and antimicrobial susceptibility of C. difficile in the reference hospital of the Balearic Islands (Spain) is reported in this study. One hundred isolates of toxigenic C. difficile from different patients were selected using rapid dual EIA screening test. All isolates were characterized through toxin profile, PCR ribotyping and, in addition, multi-locus sequence typing (MLST) was performed on fifty selected strains. MICs to metronidazole, vancomycin, erythromycin and moxifloxacin were also determined. A total of 43 different ribotypes were distinguished, with higher prevalence of ribotype 014 (34%). Twenty one per cent of the isolates expressed binary toxin and it is noteworthy that 62% of these were identified as the hypervirulent ribotype 078, the second most prevalent ribotype found in our hospital (13%). A total of 20 different sequence types (STs) were found, including a new described allele and ST. MLST data showed a clear concordance between some ribotypes and STs, mainly represented by ribotype 014/ST-2, ribotype 078/ST-11 and ribotype 001/ST-3. Phylogenetic analysis also revealed that most of the isolates were genetically related, forming a large clonal complex. Finally, ribotypes 078 (ST-11) and 001 (ST-3) were associated with higher resistance to erythromycin and to erythromycin and moxifloxacin, respectively. All these data suggest that the combination of ribotyping and MLST is a good tool for the surveillance of the changing epidemiology of C. difficile. A wide dissemination of clones has been observed in our setting, ribotype 014 (ST-2) being the most prevalent followed by the hypervirulent ribotype 078 (ST-11) and ribotype 001 (ST-3), their spread in our setting probably influenced by their higher resistance.

Epidemiology of Clostridium difficile infections in a tertiary-care hospital in Korea

To survey healthcare-associated Clostridium difficile infection (HA-CDI) in a 900-bed tertiary-care hospital, we prospectively investigated the epidemiology of CDI and distribution of PCR-ribotypes. From February 2009 through January 2010, all patients with HA-CDI were enrolled. Epidemiological information and prescription records for antibiotics were collected. The C. difficile isolates were characterized using reference strains and were tested for antibiotic susceptibility. During the survey, incidence of HA-CDI was 71.6 per 100 000 patient-days. In total, 140 C. difficile isolates were obtained from 166 patients with HA-CDI. The PCR-ribotyping yielded 38 distinct ribotypes. The three most frequently found ribotypes made up 56.4% of all isolates; they comprised 37 isolates (26.4%) of PCR-ribotype 018, 22 (15.7%) of toxin A-negative PCR-ribotype 017, and 20 (14.3%) of PCR-ribotype 001. Clostridium difficile PCR-ribotype 018 was present in all departments throughout the hospital during the 11 months, whereas ribotype 017 and ribotype 001 appeared mostly in the pulmonary department. Hypervirulent C. difficile PCR-ribotype 027 was detected in 1 month on two wards. The incidence of CDI in each department showed a seven-fold difference, which correlated significantly with the amount of prescribed clindamycin (R = 0.783, p 0.013) or moxifloxacin (R = 0.733, p 0.025) in the departments. The rates of resistance of the three commonest ribotypes to clindamycin and moxifloxacin were significantly higher than those of other strains (92.1% versus 38.2% and 89.5% versus 27.3%, respectively). CDI is an important nosocomially acquired infection and this study emphasizes the importance of implementing country-wide surveillance to detect and control CDI in Korea.

Association between PCR ribotypes and antimicrobial susceptibility among Clostridium difficile isolates from healthcare-associated infections in South Korea

In this study, the association between antimicrobial susceptibility, PCR ribotype and presence of the ermB gene in clinical isolates of Clostridium difficile was investigated. PCR ribotyping and ermB gene PCR were performed on 131 C. difficile isolates. The susceptibility of these isolates to metronidazole, vancomycin, piperacillin/tazobactam (TZP), clindamycin, moxifloxacin and rifaximin was also determined. Use of antibiotics within the previous 2 months was documented. Resistance rates to clindamycin, moxifloxacin and rifaximin were 67.9%, 62.6% and 19.1%, respectively. No metronidazole, vancomycin or TZP resistance was detected. Previous exposure to moxifloxacin was significantly correlated with resistance to this antibiotic, but prior use of clindamycin was not significantly correlated with clindamycin resistance. Sixty-four strains (48.9%) carried the ermB gene, of which all but one (98.5%) were resistant to clindamycin. The clindamycin resistance rates of the common PCR ribotypes (018, 017 and 001) were 91.4%, 100% and 84.2%, respectively, and their moxifloxacin resistance rates were 91.4%, 95.0% and 78.9%, respectively. Resistance rates to rifaximin were 5.7% and 95.0% in ribotype 018 and 017 strains, whilst none of the 001 strains were resistant to rifaximin. In conclusion, the common ribotypes 018, 017 and 001 of C. difficile have high rates of resistance to clindamycin and moxifloxacin, but differ greatly in the frequency of rifaximin resistance.

Activity of a novel cyclic lipopeptide, CB-183,315, against resistant Clostridium difficile and other Gram-positive aerobic and anaerobic intestinal pathogens

We evaluated the activity of CB-183,315 against Clostridium difficile, including strains that are resistant to fluoroquinolones and metronidazole and with elevated MICs to vancomycin as well as other Gram-positive intestinal pathogens. The MICs of CB-183,315 against all C. difficile isolates were ≤ 1 μg/ml. CB-183,315 had greater activity than vancomycin and metronidazole against C. difficile isolates and was more active than the comparators against vancomycin-resistant enterococcus (VRE). CB-183,315 also had excellent activity against methicillin-resistant Staphylococcus aureus (MRSA), other Clostridium spp., and Peptostreptococcus spp.

Molecular and microbiological characterization of Clostridium difficile isolates from single, relapse, and reinfection cases

In this study, we investigated the correlation between the microbiological characteristics of Clostridium difficile clinical isolates and the recurrence of C. difficile-associated disease (CDAD). Twenty C. difficile isolates recovered from 20 single infection cases and 53 isolates from 20 recurrent cases were analyzed by pulsed-field gel electrophoresis (PFGE) and PCR ribotyping, and the cytotoxicity, antimicrobial susceptibility, and sporulation/germination rates of the isolates were examined. Recurrent cases were divided into relapse or reinfection cases by the results of C. difficile DNA typing. Among the 20 recurrent cases, 16 cases (80%) were identified to be relapse cases caused by the initial strain and the remaining 4 cases (20%) were identified to be reinfection cases caused by different strains. All 73 isolates were susceptible to both vancomycin and metronidazole, but resistance against clindamycin, ceftriaxone, erythromycin, and ciprofloxacin was found in 87.7%, 93.2%, 87.7%, and 100% of the isolates, respectively. No correlations between DNA typing group, cytotoxicity, and sporulation rate of isolates and infection status, i.e., single, relapse, or reinfection, were observed. However, the isolates recovered from relapse cases showed a significantly higher germination rate when incubated in medium lacking the germination stimulant sodium taurocholate. These results indicate that the germination ability of C. difficile may be a potential risk factor for the recurrence of CDAD.

The epidemiology of Clostridium difficile in Scotland

The objective of this study was to characterise the epidemiology of Clostridium difficile in Scotland by determining the distribution of PCR ribotypes and antimicrobial susceptibility in 1613 isolates collected from all healthboard areas of Scotland in the period November 2007-December 2009. Three PCR ribotypes predominated amongst the Scottish isolates of C. difficile; ribotype 106 (29.4%), ribotype 001 (22%) and ribotype 027 (12.6%) followed by the less prevalent ribotypes including 002, 015, 014, 078, 005, 023 and 020. The distribution of ribotypes varied between healthboard areas. Ribotype 106 or 001 was the predominant ribotype in 10 healthboard areas, while ribotype 027 was the predominant type in two neighbouring areas. Antimicrobial susceptibility testing of C. difficile isolates showed high frequencies of resistance to moxifloxacin, levofloxacin, erythromycin and cefotaxime in the epidemic C. difficile ribotypes 001, 027 and 106 compared to other less common ribotypes. Furthermore, reduced susceptibility to metronidazole was found only in the epidemic strains. These findings are compatible with the hypothesis that fluoroquinolones, macrolides and cephalosporins may play a role in the spread of C. difficile in Scotland (while the role of metronidazole needs further investigations), and highlights the role of antimicrobial stewardship in preventing and controlling C. difficile infection (CDI).

Comparison of toxin and spore production in clinically relevant strains of Clostridium difficile

Clostridium difficile is a major cause of nosocomial diarrhoea. The toxins that it produces (TcdA and TcdB) are responsible for the characteristic pathology of C. difficile infection (CDI), while its spores persist in the environment, causing its widespread transmission. Many different strains of C. difficile exist worldwide and the epidemiology of the strains is ever-changing: in Scotland, PCR ribotype 012 was once prevalent, but currently ribotypes 106, 001 and 027 are endemic. This study aimed to identify the differences among these ribotypes with respect to their growth, and toxin and spore production in vitro. It was observed that the hypervirulent ribotype 027 produces significantly more toxin than the other ribotypes in the exponential and stationary phases of growth. Further, the endemic strains produce significantly more toxins and spores than ribotype 012. Of note was the observation that tcdC expression did not decrease into the stationary phase of growth, implying that it may have a modulatory rather than repressive effect on toxin production. Further, the increased expression of tcdE in ribotype 027 suggests its importance in the release of the toxins. It can thus be concluded that several genotypic and phenotypic traits might synergistically contribute to the hypervirulence of ribotype 027. These observations might suggest a changing trend towards increased virulence in the strains currently responsible for CDI.