Antimicrobial susceptibility and resistance mechanisms of clinical Clostridium difficile from a Chinese tertiary hospital

Antibiotic Resistances of Clostridioides difficile

The rapid evolution of antibiotic resistance in Clostridioides difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are a matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances, and most of the epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways or biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

Microbial Resistance to Antibiotics and Effective Antibiotherapy

Currently, the efficacy of antibiotics is severely affected by the emergence of the antimicrobial resistance phenomenon, leading to increased morbidity and mortality worldwide. Multidrug-resistant pathogens are found not only in hospital settings, but also in the community, and are considered one of the biggest public health concerns. The main mechanisms by which bacteria develop resistance to antibiotics include changes in the drug target, prevention of entering the cell, elimination through efflux pumps or inactivation of drugs. A better understanding and prediction of resistance patterns of a pathogen will lead to a better selection of active antibiotics for the treatment of multidrug-resistant infections.

Clostridioides difficile in Latin America: A comprehensive review of literature (1984-2021)

This narrative review summarizes literature on C. difficile and C. difficile infections (CDI) that emerged from Latin America (LA) between 1984 and 2021. The revised information includes papers in English, Spanish, or Portuguese that were retrieved from the databases Pubmed, Scopus, Web of Science, Google Scholar, Scielo, and Lilacs. Information is presented chronologically and segregated in subregions, focusing on clinical presentation, risk factors, detection and typing methods, prevalence and incidence rates, circulating strains, and, when available, phenotypic traits, such as antimicrobial susceptibility patterns. Studies dealing with cases, clinical aspects of CDI, and performance evaluations of diagnostic methods predominated. However, they showed substantial differences in case definitions, measuring units, populations, and experimental designs. Although a handful of autochthonous strains were identified, predominantly in Brazil and Costa Rica, the presentation and epidemiology of CDI in LA were highly comparable to what has been reported in other regions of the world. Few laboratories isolate and type this bacterium and even less generate whole genome sequences or perform basic science on C. difficile. Less than ten countries lead academic productivity on C. difficile or CDI-related topics, and information from various countries in Central America and the Caribbean is still lacking. The review ends with a global interpretation of the data and recommendations to further develop and consolidate this discipline in LA.

Complete Genome Sequencing and Comparative Phenotypic Analysis Reveal the Discrepancy Between Clostridioides difficile ST81 and ST37 Isolates

Toxin A-negative, toxin B-positive Clostridioides difficile strains, which primarily include the ST81 and ST37 genotypes, are predominant in C. difficile infections leading to antibiotic-associated diarrhea in China. Recently, ST81 has been reported as the most prevalent genotype rather than ST37, although the genetic and functional characteristics of the two genotypes remain ambiguous. In this study, we conducted comprehensive comparative analysis of these two genotypes through complete genome sequencing and phenotypic profiling. The whole genome sequencing revealed that the ST81 and ST37 isolates were closely related genetically with similar gene compositions, and high rate of the core genome shared. The integrative and conjugative elements identified in ST81 were similar to those in ST37, albeit with more diverse and insertion regions. By characterizing the phenotypes related to colonization or survival in the host, we found that the ST81 isolates exhibited robust colonization ability and survival both in vitro and in vivo, enhanced spore production, and slightly increased motility, which may be attributable to the discrepancy in non-synonymous single-nucleotide polymorphisms in the relevant functional genes. Furthermore, the ST81 isolates displayed a significantly higher rate of resistance to fluoroquinolones compared with the ST37 isolates (94.12% vs. 62.5%) and mostly carried the amino acid substitution Asp426Val in GyrB. In summary, the results of our study indicate that ST81 isolates exhibit enhanced ability to transmit between hosts and survive in harsh environments, providing key genetic insights for further epidemiological investigations and surveillance of C. difficile infection.

Clostridioides difficile as a Dynamic Vehicle for the Dissemination of Antimicrobial-Resistance Determinants: Review and In Silico Analysis

The present paper is divided into two parts. The first part focuses on the role of Clostridioides difficile in the accumulation of genes associated with antimicrobial resistance and then the transmission of them to other pathogenic bacteria occupying the same human intestinal niche. The second part describes an in silico analysis of the genomes of C. difficile available in GenBank, with regard to the presence of mobile genetic elements and antimicrobial resistance genes. The diversity of the C. difficile genome is discussed, and the current status of resistance of the organisms to various antimicrobial agents is reviewed. The role of transposons associated with antimicrobial resistance is appraised; the importance of plasmids associated with antimicrobial resistance is discussed, and the significance of bacteriophages as a potential shuttle for antimicrobial resistance genes is presented. In the in silico study, 1101 C. difficile genomes were found to harbor mobile genetic elements; Tn6009, Tn6105, CTn7 and Tn6192, Tn6194 and IS256 were the ones more frequently identified. The genes most commonly harbored therein were: ermB, blaCDD, vanT, vanR, vanG and vanS. Tn6194 was likely associated with resistance to erythromycin, Tn6192 and CTn7 with resistance to the β-lactams and vancomycin, IS256 with resistance to aminoglycoside and Tn6105 to vancomycin.

Isolation and characterization of a multidrug-resistant Clostridioides difficile toxinotype V from municipal wastewater treatment plant

PURPOSE

Wastewater treatment plant (WWTP) is regarded as a potential source for transmission of Clostridioides difficile from urban areas into the surface water, through feces of human and animals. The aim of this study was to screen and characterize the C. difficile bacteria in inlet and outlet wastewater of different WWTPs in Tehran, Iran.

METHODS

Totally, 72 samples were collected from three different WWTPs (inlet site and outlet sites) during a year. C. difficile was isolated and characterized in terms of toxins, toxinotype, resistance profile and genes, and colonization factors using PCR.

RESULTS

One C. difficile toxinotype V was isolated from the outlet samples. The isolate was susceptible to vancomycin but resistant to metronidazole, tetracycline, ciprofloxacin, and moxifloxacin using MIC Test Strips. The isolated C. difficile was toxigenic (tcdA, tcdB, cdtA, cdtB positive and CPE positive) and had tcdC-A genotype. No mutations were found in fliC and fliD. The slpA sequence type was 078 - 01. The C. difficile was positive for tetM, int, but negative for vanA, nim, and tndX genes. Mutations were not observed in gyrA and gyrB genes.

CONCLUSIONS

This study provided evidence of presence of a multidrug-resistant C. difficile toxinotype V in one of the municipal WWTP. The transmission of such isolate to the environment and reuse of treated wastewater by human pose a threat to human health and dissemination of antibiotic resistant bacteria which are untreatable.

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.

Surveillance of antimicrobial susceptibilities reveals high proportions of multidrug resistance in toxigenic Clostridium difficile strains in different areas of Poland

Two hundred and fifty-three non-duplicate toxigenic Clostridium difficile isolates, collected from February 2012 to December 2014, were evaluated for phenotypic resistance to ten antimicrobial drugs with the E-test gradient diffusion method. All strains of C. difficile were susceptible to metronidazole, vancomycin, and tigecycline. The metronidazole MIC values of the hyperepidemic PCR-ribotypes RT027 and RT176 were higher than those of non-epidemic PCR-ribotypes (p < 0.05, as evidenced by Mann-Whitney U test). In contrast, vancomycin susceptibility did not differ between hyperepidemic and non-epidemic strains, although the difference was almost significant (p = 0.065). Clostridium difficile RT027 and RT176 isolates could be assessed to five and four different susceptibility patterns, respectively, representing various combinations of resistance to different antimicrobial classes. A single point mutation (Thr82Ile) in the gyrA gene was detected in 11 (78.6%) of 14 isolates with high level of resistance to ciprofloxacin and moxifloxacin and four different types of single point mutations (Arg447Lys, Ser416Ala, Asp426Val, Asp426Asn) in the gyrB gene were detected in 4 strains, also with high level of resistance to ciprofloxacin and moxifloxacin. Four different point mutations were detected in the rpoB gene in 21 rifampicin-resistant strains of which one has not been reported previously, Gln489Leu. This study demonstrates the presence of multidrug-resistant C. difficile strains in Polish hospitals over the study period, irrespective of geographical location or reference level of the hospital.

Antibiotic resistance of clinical isolates of Clostridioides difficile in China and its association with geographical regions and patient age

It is known that antibiotic usage is associated with the development of Clostridioides difficile infection (CDI), especially clindamycin, third-generation cephalosporins, and fuoroquinolones. Antibiotic resistance rates to many antibiotics varies a lot by study. We performed a study focused on antibiotic resistance in clinical isolates of C. difficile from more widespread geographic regions across China. Of 319 C. difficile isolates tested against 11 antibiotics, 313 (98.1%) were resistant to at least one antibiotic. The highest rate of resistance was to ciprofloxacin, clindamycin, and erythromycin across all age groups, similar to previous studies. However, all isolates were susceptible to metronidazole and vancomycin. Overall the resistance rate to tested antibiotics was lower than other reports in China except for chloramphenicol and meropenem. Genotype ST37/RT017 in clade 4 was resistant to more antibiotics than other types. Unexpectedly, RT078 isolates in this study were susceptible to almost all tested antibiotics. In addition, the proportion of multi-drug resistant (MDR) isolates observed (17%) in this study was much lower than several European studies (up to 55%) and a previous study in China (78%). Although isolates from patients aged between 65 and 85 were more resistant to antibiotics in comparison to other age groups, MDR isolates were still detected in children below 2-years of age. The highest percentage of MDR isolates was determined in South China, an area that is most developed economically. The clade 4, RT017 (ST37) has been associated with outbreaks in Europe and North America and is responsible for most C. difficile infections (CDIs) in Asia. In addition, RT017 is often clindamycin and fluoroquinolone resistant. This study provided a relatively comprehensive description of antibiotic resistance of C. difficile in China, and further elucidates the epidemiology and antibiotic resistance of clinical isolates of C. difficile in China at a national level.

Prevalence, characteristics and antimicrobial susceptibility patterns of Clostridioides difficile isolated from hospitals in Iran

OBJECTIVES

Clostridioides (previously Clostridium) difficile is a major growing cause of nosocomial diarrhoea known as C. difficile infection (CDI). This study investigated the prevalence and antimicrobial resistance patterns of C. difficile isolated from patients suffering from diarrhoea in Iran between 2016-2018.

METHODS

A total of 151 stool specimens were collected and were screened for the presence of C. difficile. Specimens were examined for toxins by culture, enzyme immunoassay (EIA) and PCR. Antimicrobial susceptibility testing was performed for 12 antibiotics (metronidazole, vancomycin, clindamycin, tetracycline, erythromycin, ciprofloxacin, levofloxacin, moxifloxacin, fusidic acid, piperacillin, piperacillin/tazobactam and rifampicin) by the disk diffusion method according to the guidelines of the CLSI, EUCAST and CA-SFM.

RESULTS

Of 151 stool specimens, 66 (43.7%) were positive for C. difficile by PCR, whereas 2 (1.3%) were only positive for C. difficile toxins based on EIA. A total of 292 clostridial isolates were obtained from specimens by culture, of which 133 (45.5%) were finally confirmed as C. difficile by PCR. Of 121 isolates resistant to at least one antibiotic, 107 (88.4%) were resistant to three or more antimicrobials and thus were defined as multidrug-resistant (MDR). Different and diverse resistance patterns to the antimicrobial drugs were seen among the isolates.

CONCLUSION

This is the first report of the isolation of C. difficile from different governmental hospitals of Iran and indicates that CDI might be an important nosocomial infection in different hospital wards. Moreover, this study provides a comprehensive picture of the MDR phenotype characteristics of C. difficile isolates in Iran.

Prevalence, genotype and antimicrobial resistance of Clostridium difficile isolates from healthy pets in Eastern China

BACKGROUND

Clostridium difficile (C. difficile) is a main cause of antibiotic-associated diarrhoea in humans. Several studies have been performed to reveal the prevalence rate of C. difficile in cats and dogs. However, little is known about the epidemiology of C. difficile in healthy pets in China. This study aimed to assess the burden of C. difficile shedding by healthy dogs and cats in China. Furthermore, the genetic diversity and antimicrobial susceptibility patterns of the recovered isolates were determined.

METHODS

A total of 175 faecal samples were collected from 146 healthy dogs and 29 cats. C. difficile strains were isolated and identified from the feces of these pets. The characterized C. difficile strains were typed by multilocus sequence typing (MLST), and the MICs of the isolates were determined against ampicillin, clindamycin, tetracycline, moxifloxacin, chloramphenicol, cefoxitin, metronidazole and vancomycin by the agar dilution method.

RESULTS

Overall, 3 faecal samples (1.7%) were C. difficile culture positive. One sample (0.7%) from a dog was C. difficile culture positive, while two cats (7.0%) yielded positive cultures. The prevalence rate differed significantly between cats and dogs. These isolates were typed into 3 MLST genotypes and were susceptible to chloramphenicol, tetracycline, metronidazole and moxifloxacin and resistant to ampicillin, clindamycin and cefoxitin. Notably, one strain, D141-1, which was resistant to three kinds of antibiotics and carried toxin genes, was recovered in the faeces of a healthy dog.

CONCLUSION

Our results suggest that common pets may be a source of pathogenic C. difficile, indicating that household transmission of C. difficile from pets to humans can not be excluded.

Genomic Study of a Clostridium difficile Multidrug Resistant Outbreak-Related Clone Reveals Novel Determinants of Resistance

Background:Clostridium difficile infection (CDI) is prevalent in healthcare settings. The emergence of hypervirulent and antibiotic resistant strains has led to an increase in CDI incidence and frequent outbreaks. While the main virulence factors are the TcdA and TcdB toxins, antibiotic resistance is thought to play a key role in the infection by and dissemination of C. difficile.

Methods: A CDI outbreak involving 12 patients was detected in a tertiary care hospital, in Lisbon, which extended from January to July, with a peak in February, in 2016. The C. difficile isolates, obtained from anaerobic culture of stool samples, were subjected to antimicrobial susceptibility testing with Etest^®strips against 11 antibiotics, determination of toxin genes profile, PCR-ribotyping, multilocus variable-number tandem-repeat analysis (MLVA) and whole genome sequencing (WGS).

Results: Of the 12 CDI cases detected, 11 isolates from 11 patients were characterized. All isolates were tcdA^-/tcdB⁺ and belonged to ribotype 017, and showed high level resistance to clindamycin, erythromycin, gentamicin, imipenem, moxifloxacin, rifampicin and tetracycline. The isolates belonged to four genetically related MLVA types, with six isolates forming a clonal cluster. Three outbreak isolates, each from a different MLVA type, were selected for WGS. Bioinformatics analysis showed the presence of several antibiotic resistance determinants, including the Thr82Ile substitution in gyrA, conferring moxifloxacin resistance, the substitutions His502Asn and Arg505Lys in rpoB for rifampicin resistance, the tetM gene, associated with tetracycline resistance, and two genes encoding putative aminoglycoside-modifying enzymes, aadE and aac(6′)-aph(2″). Furthermore, a not previously described 61.3 kb putative mobile element was identified, presenting a mosaic structure and containing the genes ermG, mefA/msrD and vat, associated with macrolide, lincosamide and streptogramins resistance. A substitution found in a class B penicillin-binding protein, Cys721Ser, is thought to contribute to imipenem resistance.

Conclusion: We describe an epidemic, tcdA^-/tcdB⁺, multidrug resistant clone of C. difficile from ribotype 017 associated with a hospital outbreak, providing further evidence that the lack of TcdA does not impair the infectious potential of these strains. We identified several determinants of antimicrobial resistance, including new ones located in mobile elements, highlighting the importance of horizontal gene transfer in the pathogenicity and epidemiological success of C. difficile.

Highly antibiotic-resistant Clostridium difficile isolates from Iranian patients

AIMS

Little is known about the resistance rate and susceptibility profile of Clostridium difficile isolates in Iran. Therefore, the aim of present study is to assess the rate of drug-resistant C. difficile.

METHODS AND RESULTS

During a 6-year period, four hospitals submitted 735 stool specimens from patients suspected for C. difficile infections to the anaerobic bacteriology laboratory. The 46 C. difficile isolates were subjected to disc diffusion and minimum inhibitory concentration (MIC) Test Strips. All isolates were susceptible to vancomycin (VAN) while the highly resistant phenotypes of metronidazole (MTZ) (67·4%), moxifloxacin (78·3%), ciprofloxacin (69·5%) and tetracycline (82·6%) were observed. Of more concern, 67·3% of C. difficile isolates displayed multidrug-resistant phenotypes. More than half of the isolates (n = 27, 58·6%) were coresistant to ciprofloxacin and moxifloxacin. The MIC90 of VAN was ≤2 mg l^-1 , whereas this value for MTZ, ciprofloxacin, moxifloxacin and tetracycline was higher than the resistance breakpoints. According to the comparison of interpretive categories for two tests, the categorical agreement was less than 90% for VAN, ciprofloxacin and tetracycline.

CONCLUSIONS

The disc diffusion method can be used to detect the isolates with reduced susceptibility to MTZ or moxifloxacin. The high rate of resistance to fluoroquinolones highlights the possibility of the emergence of hypervirulent strains in our settings.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides data regarding the high level of resistance against multiple antibiotics except VAN.

Isolation of Toxigenic Clostridium difficile from Animal Manure and Composts Being Used as Biological Soil Amendments

The well-known nosocomial pathogen Clostridium difficile has recently been recognized as a community-associated pathogen. As livestock animals carry and shed C. difficile in their feces, animal manure-based composts may play an important role in disseminating toxigenic C. difficile strains into the agricultural environment. The present study surveyed C. difficile contamination of commercially available composts and animal manure. Presumptive C. difficile isolates were confirmed by testing for the tpi housekeeping gene in addition to Gram staining. The confirmed C. difficile isolates were further tested for toxigenicity, PCR ribotype, and susceptibilities to selected antibiotics. C. difficile was found in 51 out of 142 samples (36%). A total of 58 C. difficile strains were isolated from those 51 positive compost/manure samples. The presence of C. difficile in compost did not significantly correlate (P > 0.05) with the physical and most microbiological parameters, including the presence of fecal coliforms. The majority of C. difficile isolates were toxigenic, with 63.8% positive for the toxin A gene (tcdA) and 67.2% positive for the toxin B gene (tcdB). Only 3 isolates (5.17%) were positive for the binary toxins. There were 38 different PCR ribotypes among the 58 C. difficile isolates, and ribotype 106 was the most prevalent, followed by ribotypes 020 and 412. All C. difficile isolates were susceptible to the selected antibiotics, but >50% of the isolates had reduced susceptibility to clindamycin by the agar dilution method. This study indicates that compost may be a reservoir of toxigenic C. difficile strains.IMPORTANCEClostridium difficile infection (CDI) is a leading cause of antibiotic-associated diarrhea in health care facilities in developed countries. Extended hospital stays and recurrences severely increase the cost of treatments and the high mortality rate that is observed among the elderly. Community-associated CDI cases that occur without any recent contact with the hospital environment are increasing. Studies have reported the isolation of virulent C. difficile strains from water, soil, meat, vegetables, pets, livestock animals, and animal manure. The objective of this study was to isolate and characterize C. difficile strains from animal manure and commercially available compost products. Our results demonstrate that not only unprocessed animal manure but also finished composts made of different feedstocks can serve as a reservoir for C. difficile as well. Most importantly, our study revealed that properly processed compost is a potential source of toxigenic and clindamycin-resistant C. difficile isolates.

Molecular epidemiology and antimicrobial susceptibility of human Clostridium difficile isolates from a single institution in Northern China

Because the epidemiology of Clostridium difficile infection (CDI) is region-specific, the present study was undertaken to examine the epidemiology of C difficile outbreaks in Beijing, China.Eighty nonduplicate isolates were collected from March, 2016 to December, 2016. The molecular type and phylogenetic analysis were evaluated by multilocus sequence typing (MLST). The minimum inhibitory concentrations (MICs) for 11 antibiotics and the resistance mechanisms were investigated.Sixty-five toxigenic strains (81.25%), including 22 tcdABCDT strains (27.5%) and 43 tcdABCDT strains (53.75%), and also 15 nontoxigenic strains (tcdABCDT; 18.75%) were detected. MLST identified 21 different sequence types (STs), including 2 novel types (ST409 and ST416). All isolates were susceptible to metronidazole, vancomycin, fidaxomicin, piperacillin/tazobactam, and meropenem, and all were effectively inhibited by emodin (MICs 4-8 μg/mL). The resistance rates to rifaximin, ceftriaxone, clindamycin, erythromycin, and ciprofloxacin were 8.75%, 51.25%, 96.25%, 81.25%, and 96.25%, respectively; 81.25% (65/80) of isolates were multidrug-resistant. Amino acid mutations in GyrA and/or GyrB conferred quinolone resistance. One novel amino acid substitution, F86Y in GyrA, was found in 1 CIP-intermediate strain. The erm(B) gene played a key role in mediating macrolide-lincosamide-streptogramin B (MLSB) resistance. Erm(G) was also found in erm(B)-negative strains that were resistant to both erythromycin and clindamycin. RpoB mutations were associated with rifampin resistance, and 2 new amino mutations were identified in 1 intermediate strain (E573A and E603N).Regional diversity and gene heterogeneity exist in both the ST type and resistant patterns of clinical C difficile isolates in Northern China.

Use of matrix-assisted laser desorption ionization-time of flight mass spectrometry to identify MLST clade 4 Clostridium difficile isolates

Clostridium difficile is the leading cause of health care-associated infections. Previous studies suggest that C. difficile MLST clade 4 strains with higher drug resistance rates constitute the major clone spreading in China. Thus development of a rapid and accurate typing method for these strains is needed to monitor the epidemiology of this clone and to guide clinical treatment. A total of 160 non-duplicate C. difficile isolates recovered from three large teaching hospitals in Beijing were studied. All the 41 clade 4 C. difficile isolates clustered together on the PCA dendrogram. Spectra peak statistics revealed that five markers (2691.43Da, 2704.91Da, 2711.93Da, 3247.27Da and 3290.76Da) can easily and reliably distinguish between clade 4 and non-clade 4 isolates, with area under the curve (AUC) values of 0.991, 0.997, 0.973, 1 and 1, respectively. In conclusion, MALDI-TOF MS is a very simple and accurate method for identifying C. difficile MLST clade 4 strains.

Molecular characterization of Clostridium difficile isolated from carriage and association of its pathogenicity to prevalent toxic genes

BACKGROUND

There are reports of non-toxigenic C. difficile strains from asymptomatic carriers are increasing source of transmission. Asymptomatic carriage transmission in the hospital or community settings might have changed over the years. Therefore, we initiated a prospective epidemiological study to define the risk factors and pathogenicity of asymptomatic C. difficile carriage.

METHODS

Stools sample from 188 subjects with diarrhoea due to C. difficile toxin and colonization without diarrhoea was subjected to routine microbial culture, molecular characterization for identification of toxin genes and mechanisms of resistance in C.difficile. Demographic data were recorded. Fifty five were positive for C. difficile includes thirty nine toxigenic C. difficile (TCD) and sixteen non toxigenic C. difficile (NTCD) isolates. Pathogenecity of toxic and nontoxic strains were analysed using AO/EB staining, Annexin V staining using flow cytometer and Galleria mellonella survival analyses.

RESULTS

Among 188, fifty five were positive for C.difficile. Infected or colonized individual with TCD or NTCD were more frequently exposed to hemodialysis compared with uncolonized patients. Isolates showed more resistant to clindamycin and levofloxacin. All TCD and eight of NTCD were tcdA-positive. Only four of TCD were positive for cdtA, tcdA, and tcdB (7%, n = 55). In thirty isolates erm (B) gene was found to be prevelant gene. High virulence was found with TCD strain and it was validated using in Galleria mellonella infection model which supported in vitro experiments. The strain with cdtA, tcdA, and tcdB, seen to have elevated virulence to increased resistance and virulence subsequently led to raised virulence in this pathogen.

CONCLUSION

Asymptomatic TCD colonization was relatively high, however, with a small number of enrolled subjects the significant of results might have limitations and the occurrence of CDI among different age group still remains unclear.

A retrospective study of community-acquired Clostridium difficile infection in southwest China

To identify the prevalence and characteristics of community-acquired Clostridium difficile infection (CA-CDI) in southwest China, we conducted a cross-sectional study. 978 diarrhea patients were enrolled and stool specimens’ DNA was screened for virulence genes. Bacterial culture was performed and isolates were characterized by PCR ribotyping and multilocus sequence typing. Toxin genes tcdA and/or tcdB were found in 138/978 (14.11%) cases for fecal samples. A total of 55 C. difficile strains were isolated (5.62%). The positive rate of toxin genes and isolation results had no statistical significance between children and adults groups. However, some clinical features, such as fecal property, diarrhea times before hospital treatment shown difference between two groups. The watery stool was more likely found in children, while the blood stool for adults; most of children cases diarrhea ≤3 times before hospital treatment, and adults diarrhea >3 times. Independent risk factor associated with CA-CDI was patients with fever. ST35/RT046 (18.18%), ST54/RT012 (14.55%), ST3/RT001 (14.55%) and ST3/RT009 (12.73%) were the most distributed genotype profiles. ST35/RT046, ST3/RT001 and ST3/RT009 were the commonly found in children patients but ST54/RT012 for adults. The prevalence of CA-CDI in Yunnan province was relatively high, and isolates displayed heterogeneity between children and adults groups.

Clostridium difficile Infections: A Global Overview of Drug Sensitivity and Resistance Mechanisms

Clostridium difficile (C. difficile) is the most prevalent causative pathogen of healthcare-associated diarrhea. Notably, over the past 10 years, the number of Clostridium difficile outbreaks has increased with the rate of morbidity and mortality. The occurrence and spread of C. difficile strains that are resistant to multiple antimicrobial drugs complicate prevention as well as potential treatment options. Most C. difficile isolates are still susceptible to metronidazole and vancomycin. Incidences of C. difficile resistance to other antimicrobial drugs have also been reported. Most of the antibiotics correlated with C. difficile infection (CDI), such as ampicillin, amoxicillin, cephalosporins, clindamycin, and fluoroquinolones, continue to be associated with the highest risk for CDI. Still, the detailed mechanism of resistance to metronidazole or vancomycin is not clear. Alternation in the target sites of the antibiotics is the main mechanism of erythromycin, fluoroquinolone, and rifamycin resistance in C. difficile. In this review, different antimicrobial agents are discussed and C. difficile resistance patterns and their mechanism of survival are summarized.

Antibiotic Resistances of Clostridium difficile

The rapid evolution of antibiotic resistance in Clostridium difficile and the consequent effects on prevention and treatment of C. difficile infections (CDIs) are matter of concern for public health. Antibiotic resistance plays an important role in driving C. difficile epidemiology. Emergence of new types is often associated with the emergence of new resistances and most of epidemic C. difficile clinical isolates is currently resistant to multiple antibiotics. In particular, it is to worth to note the recent identification of strains with reduced susceptibility to the first-line antibiotics for CDI treatment and/or for relapsing infections. Antibiotic resistance in C. difficile has a multifactorial nature. Acquisition of genetic elements and alterations of the antibiotic target sites, as well as other factors, such as variations in the metabolic pathways and biofilm production, contribute to the survival of this pathogen in the presence of antibiotics. Different transfer mechanisms facilitate the spread of mobile elements among C. difficile strains and between C. difficile and other species. Furthermore, recent data indicate that both genetic elements and alterations in the antibiotic targets can be maintained in C. difficile regardless of the burden imposed on fitness, and therefore resistances may persist in C. difficile population in absence of antibiotic selective pressure.

Double-Serine Fluoroquinolone Resistance Mutations Advance Major International Clones and Lineages of Various Multi-Drug Resistant Bacteria

The major international sequence types/lineages of methicillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae and ESBL-producing E. coli were demonstrated to have been advanced by favorable fitness balance associated with high-level resistance to fluoroquinolones. The paper shows that favorable fitness in the major STs/lineages of these pathogens was principally attained by the capacity of evolving mutations in the fluoroquinolone-binding serine residues of both the DNA gyrase and topoisomerase IV enzymes. The available information on fitness balance incurred by individual and various combinations of mutations in the enzymes is reviewed in multiple species. Moreover, strong circumstantial evidence is presented that major STs/lineages of other multi-drug resistant bacteria, primarily vancomycin-resistant Enterococcus faecium (VRE), emerged by a similar mechanism. The reason(s) why the major ST/lineage strains of various pathogens proved more adept at evolving favorable mutations than most isolates of the same species remains to be elucidated.

Molecular, microbiological and clinical characterization of Clostridium difficile isolates from tertiary care hospitals in Colombia

In Colombia, the epidemiology and circulating genotypes of Clostridium difficile have not yet been described. Therefore, we molecularly characterized clinical isolates of C.difficile from patients with suspicion of C.difficile infection (CDI) in three tertiary care hospitals. C.difficile was isolated from stool samples by culture, the presence of A/B toxins were detected by enzyme immunoassay, cytotoxicity was tested by cell culture and the antimicrobial susceptibility determined. After DNA extraction, tcdA, tcdB and binary toxin (CDTa/CDTb) genes were detected by PCR, and PCR-ribotyping performed. From a total of 913 stool samples collected during 2013-2014, 775 were included in the study. The frequency of A/B toxins-positive samples was 9.7% (75/775). A total of 143 isolates of C.difficile were recovered from culture, 110 (76.9%) produced cytotoxic effect in cell culture, 100 (69.9%) were tcdA+/tcdB+, 11 (7.7%) tcdA-/tcdB+, 32 (22.4%) tcdA-/tcdB- and 25 (17.5%) CDTa+/CDTb+. From 37 ribotypes identified, ribotypes 591 (20%), 106 (9%) and 002 (7.9%) were the most prevalent; only one isolate corresponded to ribotype 027, four to ribotype 078 and four were new ribotypes (794,795, 804,805). All isolates were susceptible to vancomycin and metronidazole, while 85% and 7.7% were resistant to clindamycin and moxifloxacin, respectively. By multivariate analysis, significant risk factors associated to CDI were, staying in orthopedic service, exposure to third-generation cephalosporins and staying in an ICU before CDI symptoms; moreover, steroids showed to be a protector factor. These results revealed new C. difficile ribotypes and a high diversity profile circulating in Colombia different from those reported in America and European countries.

High in vitro activity of fidaxomicin against Clostridium difficile isolates from a university teaching hospital in China

BACKGROUND

Clostridium difficile infection (CDI) is a significant cause of morbidity and mortality in both the acute care setting and the wider healthcare system. The purpose of this study was to evaluate the in vitro activity of fidaxomicin against C. difficile isolates from a university teaching hospital in China.

METHODS

One hundred and one C. difficile isolates were collected and analyzed for toxin genes by multiplex PCR. The toxin gene positive strains were also typed by multilocus sequence typing (MLST) and PCR-ribotyping. The MICs of the isolates were determined against fidaxomicin, metronidazole, vancomycin, tigecycline and moxifloxacin, by the agar dilution method.

RESULTS

All the 101 isolates exhibited low MICs to fidaxomicin (0.032-1 mg/L), metronidazole (0.125-1 mg/L), vancomycin (0.25-2 mg/L) and tigecycline (0.016-0.5 mg/L). Tigecycline showed the lowest geometric mean MIC value (0.041 mg/L), followed by fidaxomicin (0.227 mg/L), metronidazole (0.345 mg/L), and vancomycin (0.579 mg/L). About 35% of the strains (n = 35) were resistant to moxifloxacin, and the resistance rate to moxifloxacin for A-B+CDT- isolates (85.0%) was much higher than that of A+B+CDT- (15.7%) and A-B-CDT- (29.2%) isolates (P < 0.001). The MIC values of fidaxomicin, metronidazole, vancomycin and moxifloxacin against the 3 ST1 isolates were higher than for other STs. All the 28 moxifloxacin-resistant toxigenic isolates carried a mutation either in gyrA or/and gyrB.

CONCLUSION

Fidaxomicin exhibited high antimicrobial activity against all C. difficile isolates tested, which shows promise as a new drug for treating Chinese CDI patients.

Isolation of enterococci, their antimicrobial susceptibility patterns and associated factors among patients attending at the University of Gondar Teaching Hospital

Background

Enterococci become clinically important especially in immune compromised patients and important causes of nosocomial infections. Data on the prevalence, antimicrobial susceptibility patterns and associated factors of enterococci are scarce in Ethiopia.

Methods

A hospital based cross-sectional study was conducted at the University of Gondar Teaching Hospital from February 28, 2014 to May 1, 2014. Pretested structured questionnaire was used to collect socio-demographic data and possible associated factors of enterococci infections. Clinical samples including urine, blood, wound swabs and other body fluids from patients requested by physician for culture and antimicrobial susceptibility test during the study period were included. A total of 385 patients were included in the study. Data were entered and analyzed using SPSS Version 20. P values <0.05 were considered as statistically significant.

Result

The overall prevalence of enterococci infection was 6.2% (24/385). The commonest sites of infections were urinary tract followed by wound and blood. Among the 24 isolates, 33.3% (8/24) were resistant to all tested antimicrobial agents. Forty one point 7 % (10/24) of the enterococci isolates were vancomycin resistant enterococci (VRE). Moreover, two third of the isolates were multidrug resistant (MDR) enterococci. In multivariate analysis, duration of hospital stay for two days and more than two days with infection rate 17/32 (53.1%), previous history of any antibiotics (AOR = 9.13; [95% CI; 2.01–41.51] P = 0.00) and history of urinary catheterization (AOR = 8.80; [95% CI; 1.70–45.64] P = 0.01) were associated with presence of higher enterococci infections than their respective groups.

Conclusion

The prevalence of enterococci infections among patients with UTIs, wound infections and sepsis were higher than the other infections. Multi drug resistant enterococci including VRE were isolated from clinical samples in the study area. Being hospitalized for ≥48 h, having history of any antibiotic administration and catheterization were associated factors for enterococci infections. Presence of VRE indicates decreased antibiotic treatment options of multidrug resistant enterococci. Therefore, efforts should be made to prevent enterococci infections and emergency of multidrug resistant enterococci. Moreover, species identification and antibiotic resistant in advanced and at large scale is demanding.

Update on Antimicrobial Resistance in Clostridium difficile: Resistance Mechanisms and Antimicrobial Susceptibility Testing

Oral antibiotics such as metronidazole, vancomycin and fidaxomicin are therapies of choice for Clostridium difficile infection. Several important mechanisms for C. difficile antibiotic resistance have been described, including the acquisition of antibiotic resistance genes via the transfer of mobile genetic elements, selective pressure in vivo resulting in gene mutations, altered expression of redox-active proteins, iron metabolism, and DNA repair, as well as via biofilm formation. This update summarizes new information published since 2010 on phenotypic and genotypic resistance mechanisms in C. difficile and addresses susceptibility test methods and other strategies to counter antibiotic resistance of C. difficile.

Therapeutic interventions for gut dysbiosis and related disorders in the elderly: antibiotics, probiotics or faecal microbiota transplantation?

Ageing and physiological functions of the human body are inversely proportional to each other. The gut microbiota and host immune system co-evolve from infants to the elderly. Ageing is accompanied by a decline in gut microbial diversity, immunity and metabolism, which increases susceptibility to infections. Any compositional change in the gut is directly linked to gastrointestinal disorders, obesity and metabolic diseases. Increase in opportunistic pathogen invasion in the gut like Clostridium difficile leading to C. difficile infection is more common in the elderly population. Frequent hospitalisation and high prevalence of nosocomial infections with the ageing is also well documented. Long-term utilisation of broad-spectrum antibiotic therapy is being followed in order to control these infections. Nosocomial infections and antibiotic therapy in combination or alone is leading to gastroenteritis followed by Clostridium associated diarrhoea or antibiotic associated diarrhoea. Above all, use of broad-spectrum antibiotics is highly debated all over the world due to growing antimicrobial resistance. The use of narrow spectrum antibiotics could be helpful to some extent. Dietary supplementation of probiotics with prebiotics (synbiotics) or without prebiotics has improved gut commensal diversity and regulated the immune system. The recent emergence of faecal microbiota transplantation has played an important role in treating recurrent Clostridium associated diarrhoea. This review focuses on various therapeutic interventions for gut dysbiosis and gastrointestinal diseases in the elderly. The possible mechanism for antimicrobial resistance and mechanism of action of probiotics are also discussed in detail.

Molecular Epidemiology and Antimicrobial Susceptibility of Clostridium difficile Isolates from a University Teaching Hospital in China

While the developed world has seen a significant increase in the number of scientific articles on Clostridium difficile infection (CDI), the developing world still lags behind on this subject due to limited laboratory capacity, low awareness, and limited surveillance of this problem. As such, CDI is considered a neglected but potentially huge problem in developing countries. The major aim of this study was to systemically evaluate the utility of several molecular typing tools for CDI, including their relevance in epidemiological studies in developing countries such as China. A total of 116 non-repetitive toxigenic C. difficile isolates from Chinese patients, were studied. The isolates comprised 83 (71.6%) A+B+CDT- isolates, 27 (23.3%) A-B+CDT- isolates, and 6 (5.1%) A+B+CDT+ isolates. Typing methods evaluated included multilocus variable-number tandem-repeat analysis, PCR ribotyping, multilocus sequence typing, and sequencing of slpA and tcdC genes, which identified 113, 30, 22, 18, and 8 genotypes each and exhibited discriminatory powers of 0.999, 0.916, 0.907, 0.883, and 0.765, respectively. Compared to A+B+ strains, A-B+ strains exhibited higher prevalence of drug resistance to clindamycin, erythromycin, levofloxacin, rifampicin, rifaximin, and tetracycline. Furthermore, drug resistance rates of strains with different PCR ribotypes differed, supporting the importance of molecular typing in management and control of CDI. Based on our earlier suggestion to improve the diagnostic laboratory capacity of CDI in developing countries, setting up efficient surveillance programs complemented by relevant molecular typing methods is warranted.

DETECTION, RIBOTYPING AND ANTIMICROBIAL RESISTANCE PROPERTIES OF CLOSTRIDIUM DIFFICILE STRAINS ISOLATED FROM THE CASES OF DIARRHEA

BACKGROUND

Clostridium difficile is the most prevalent cause of antibiotic-associated infectious diarrhea al-around the world. Prevalence of virulent and resistant strains of Clostridium difficile is increasing now a day. The present investigation was carried out to study the prevalence, ribotyping and antibiotic resistance pattern of C. difficile isolated from diarrheic and non-diarrheic pediatrics.

MATERIALS AND METHODS

Four-hundred stool specimens were collected from the diarrheic and non-diarrheic pediatrics hospitalized due to the diseases other than diarrhea. Samples were cultured and their positive results were subjected to disk diffusion and PCR-based ribotyping.

RESULTS

Thirty-five out of 400 (8.75%) samples were positive for C. difficile. Prevalence of C. difficile in diarrheic and non-diarrheic pediatrics were 11.25% and 4.16%, respectively. Male had the higher prevalence of bacteria than female (P < 0.05). eight to twelve months old pediatrics were the most commonly infected group. R27 (14.28%), R1 (10.71%), R12 (7.14%), R13 (7.14%) and R18 (7.14%) were most commonly detected ribotypes. There were no positive results for studied ribotypes in non-diarrheic pediatrics. C. difficile strains had the highest levels of resistance against tetracycline (71.42%), erythromycin (57.14%), moxifloxacin (48.57%), metronidazole (28.57%) and clindamycin (22.85%) antibiotics.

CONCLUSION

Prescription of antibiotics in diarrheic pediatrics, males and also 8-12 months old pediatrics should be done in a regular and cautious manner.

Recent advances in the understanding of antibiotic resistance in Clostridium difficile infection

Clostridium difficile epidemiology has changed in recent years, with the emergence of highly virulent types associated with severe infections, high rates of recurrences and mortality. Antibiotic resistance plays an important role in driving these epidemiological changes and the emergence of new types. While clindamycin resistance was driving historical endemic types, new types are associated with resistance to fluoroquinolones. Furthermore, resistance to multiple antibiotics is a common feature of the newly emergent strains and, in general, of many epidemic isolates. A reduced susceptibility to antibiotics used for C. difficile infection (CDI) treatment, in particular to metronidazole, has recently been described in several studies. Furthermore, an increased number of strains show resistance to rifamycins, used for the treatment of relapsing CDI. Several mechanisms of resistance have been identified in C. difficile, including acquisition of genetic elements and alterations of the antibiotic target sites. The C. difficile genome contains a plethora of mobile genetic elements, many of them involved in antibiotic resistance. Transfer of genetic elements among C. difficile strains or between C. difficile and other bacterial species can occur through different mechanisms that facilitate their spread. Investigations of the fitness cost in C. difficile indicate that both genetic elements and mutations in the molecular targets of antibiotics can be maintained regardless of the burden imposed on fitness, suggesting that resistances may persist in the C. difficile population also in absence of antibiotic selective pressure. The rapid evolution of antibiotic resistance and its composite nature complicate strategies in the treatment and prevention of CDI. The rapid identification of new phenotypic and genotypic traits, the implementation of effective antimicrobial stewardship and infection control programs, and the development of alternative therapies are needed to prevent and contain the spread of resistance and to ensure an efficacious therapy for CDI.

Occurrences and distribution of sulfonamide and tetracycline resistance genes in the Yangtze River Estuary and nearby coastal area

The role of highly impacted estuaries needs to be examined with respect to the spread of antibiotic resistance genes in the environment. In the present study, sulfonamide resistance (sul), tetracycline resistance (tet) and class I integron (int1) genes were ubiquitous in the sediments of the Yangtze Estuary (YE) and nearby coastal area, and exhibited a declining trend from the inner estuary to the coast. Good relationships were only observed between int1 and sul1 genes, implying that int1 gene is essential to the proliferation of sul1 gene. A non-significant correlation between int1 and 16S rRNA genes indicated that the int1 gene came from pollution sources of ARGs instead of being intrinsic in environmental bacterial populations. Sulfonamides were rarely detected in the sediments of this region, so could not result in the production of sul genes in the local environment.

Rapid detection of ermB gene in Clostridium difficile by loop-mediated isothermal amplification

Macrolide-lincosamide-streptogramin B resistance in Clostridium difficile is mostly due to the ermB resistance determinant. Here, we describe a sensitive and rapid molecular method to detect ermB in C. difficile to contribute to the wider epidemiological study. Five sets of loop-mediated isothermal amplification (LAMP) primers were designed and optimized for rapid detection of ermB. The specificity and sensitivity of the primers for ermB were detected, and the ermB LAMP assay was compared to conventional PCR with 80 clinical isolates of C. difficile. Real-time monitoring of turbidity and chromogenic reaction were used to determine negative and positive results. A total of 26 pathogenic bacterial strains of different species were found to be negative for ermB, which indicated the high specificity of the primers. ermB was detected in 78.8 % (63/80) of the clinical isolates by both LAMP and conventional PCR. The detection limit of LAMP was 36.1  pg DNA μl- 1 and its sensitivity was 10-fold greater than that of conventional PCR. This study is the first report regarding the development and application of the LAMP assay for detection of the ermB gene in C. difficile strains. The developed LAMP method is sensitive, specific and provides a user-friendly visual approach for the rapid detection of ermB-bearing C. difficile.

Antimicrobial Resistance and Reduced Susceptibility in Clostridium difficile: Potential Consequences for Induction, Treatment, and Recurrence of C. difficile Infection

Clostridium difficile infection (CDI) remains a substantial burden on healthcare systems and is likely to remain so given our reliance on antimicrobial therapies to treat bacterial infections, especially in an aging population in whom multiple co-morbidities are common. Antimicrobial agents are a key component in the aetiology of CDI, both in the establishment of the infection and also in its treatment. The purpose of this review is to summarise the role of antimicrobial agents in primary and recurrent CDI; assessing why certain antimicrobial classes may predispose to the induction of CDI according to a balance between antimicrobial activity against the gut microflora and C. difficile. Considering these aspects of CDI is important in both the prevention of the infection and in the development of new antimicrobial treatments.

Doxycycline and Tigecycline: Two Friendly Drugs with a Low Association with Clostridium Difficile Infection

Clostridium difficile infection (CDI) is known to be associated with prior exposure to many classes of antibiotics. Standard therapy for CDI (i.e., metronidazole and vancomycin) is associated with high recurrence rates. Although tetracycline derivatives such as tetracycline, doxycycline or tigecycline are not the standard therapeutic choices for CDI, they may serve as an alternative or a component of combination therapy. Previous tetracycline or doxycycline usage had been shown to have less association with CDI development. Tigecycline, a broad-spectrum glycylcycline with potency against many gram-positive or gram-negative pathogens, had been successfully used to treat severe or refractory CDI. The in vitro susceptibility of C. difficile clinical isolates to tigecycline in many studies showed low minimal inhibitory concentrations. Tigecycline can suppress in vitro toxin production in both historical and hypervirulent C. difficile strains and reduce spore production in a dose-dependent manner. Tetracycline compounds such as doxycycline, minocycline, and tigecycline possess anti-inflammatory properties that are independent of their antibiotic activity and may contribute to their therapeutic effect for CDI. Although clinical data are limited, doxycycline is less likely to induce CDI, and tigecycline can be considered one of the therapeutic choices for severe or refractory CDI.

Emergence of an outbreak-associated Clostridium difficile variant with increased virulence

The prevalence of Clostridium difficile infections has increased due to the emergence of epidemic variants from diverse genetic lineages. Here we describe the emergence of a novel variant during an outbreak in a Costa Rican hospital that was associated with severe clinical presentations. This C. difficile variant elicited higher white blood cell counts and caused disease in younger patients than did other strains isolated during the outbreak. Furthermore, it had a recurrence rate, a 30-day attributable disease rate, and disease severity as great as those of the epidemic strain NAP1. Pulsed-field gel electrophoresis genotyping indicated that the outbreak strains belong to a previously undescribed variant, designated NAP_CR1. Whole-genome sequencing and ribotyping indicated that the NAP_CR1 variant belongs to C. difficile ribotype 012 and sequence type 54, as does the reference strain 630. NAP_CR1 strains are resistant to fluoroquinolones due to a mutation in gyrA, and they possess an 18-bp deletion in tcdC that is characteristic of the epidemic, evolutionarily distinct, C. difficile NAP1 variant. NAP_CR1 genomes contain 10% more predicted genes than strain 630, most of which are of hypothetical function and are present on phages and other mobile genetic elements. The increased virulence of NAP_CR1 was confirmed by mortality rates in the hamster model and strong inflammatory responses induced by bacteria-free supernatants in the murine ligated loop model. However, NAP_CR1 strains do not synthesize toxin A and toxin B at levels comparable to those in NAP1 strains. Our results suggest that the pathogenic potential of this emerging C. difficile variant is due to the acquisition of hypothetical functions associated with laterally acquired DNA.

Strain types and antimicrobial resistance patterns of Clostridium difficile isolates from the United States, 2011 to 2013

We determined the PCR ribotypes and antimicrobial susceptibility patterns of 508 toxigenic Clostridium difficile isolates collected between 2011 and 2013 from 32 U.S. hospitals. Of the 29 PCR ribotypes identified, the 027 strain type was the most common (28.1%), although the rates varied by geographic region. Ribotype 014/020 isolates appear to be emerging. Clindamycin and moxifloxacin resistances (36.8% and 35.8%, respectively) were the most frequent resistance phenotypes observed. Reduced susceptibility to vancomycin was observed in 39.1% of 027 isolates.

Clostridium difficile infection: a worldwide disease

Clostridium difficile, an anaerobic toxigenic bacterium, causes a severe infectious colitis that leads to significant morbidity and mortality worldwide. Both enhanced bacterial toxins and diminished host immune response contribute to symptomatic disease. C. difficile has been a well-established pathogen in North America and Europe for decades, but is just emerging in Asia. This article reviews the epidemiology, microbiology, pathophysiology, and clinical management of C. difficile. Prompt recognition of C. difficile is necessary to implement appropriate infection control practices.

Molecular epidemiology of Clostridium difficile in a tertiary hospital of China

Clostridium difficile infection (CDI) is caused by toxin-producing strains. It accounts for 20-30 % of antibiotic-associated diarrhoea and particularly accounts for 90 % of pseudomembranous colitis. The epidemiological study of C. difficile is thus important. In this study, we report the molecular epidemiology and ward distribution of C. difficile in a tertiary hospital of China. A total of 161 toxigenic strains were isolated from 1845 patients originating from different wards and the strains were characterized based on toxin profile and multilocus sequence typing. Variable isolation rates were observed in different wards and the occurrence was higher in intensive care unit and geriatric wards. Toxin gene profiling revealed that, out of the 161 isolates, 134 (83.2)% were positive for both toxin A (tcdA) and toxin B (tcdB) (A+B+) followed by toxin A-negative and B-positive (A-B+) (16.8 %) isolates. However, only three of the toxigenic strains (1.9 %) were positive for both the cdtA and cdtB genes. Based on the molecular epidemiology study, a total of 30 different sequence types (STs), including one new ST (ST-220), were distinguishable. ST-54 was the most prevalent (23.0 %), followed by ST-35 (19.3 %) and ST-37 (10.0 %). None of the isolates belonged to ST-1 (ribotype 027) or ST-11 (ribotype 078). Taken together, the toxin profile and the molecular epidemiological data showed that all the ST-37 clades were of toxin type A-B+, which accounted for 59.3 % of all type A-B+ isolates. Meanwhile the clade 1 genotype, ST-54, was widely distributed among the geriatric, infection and haematology wards. There was no outbreak of C. difficile infection during our study; however the possibility of prolonged outbreaks cannot be completely ignored.

Clostridium difficile-associated disease: Adherence with current guidelines at a tertiary medical center

AIM: To assess adherence with the the Society for Healthcare Epidemiology of America (SHEA)/ the Infectious Diseases Society of America (IDSA) guidelines for management of Clostridium difficile (C. difficile)-associated disease (CDAD) at a tertiary medical center.

METHODS: All positive C. difficile stool toxin assays in adults between May 2010 and May 2011 at the University of Maryland Medical Center were identified. CDAD episodes were classified as guideline adherent or non-adherent and these two groups were compared to determine demographic and clinical factors predictive of adherence. Logistic regression analysis was performed to assess the effect of multiple predictors on guideline adherence.

RESULTS: 320 positive C. difficile stool tests were identified in 290 patients. Stratified by disease severity criteria set forth by the SHEA/IDSA guidelines, 42.2% of cases were mild-moderate, 48.1% severe, and 9.7% severe-complicated. Full adherence with the guidelines was observed in only 43.4% of cases. Adherence was 65.9% for mild-moderate CDAD, which was significantly better than in severe cases (25.3%) or severe-complicated cases (35.5%) (P < 0.001). There was no difference in demographics, hospitalization, ICU exposure, recurrence or 30-d mortality between adherent and non-adherent groups. A multivariate model revealed significantly decreased adherence for severe or severe-complicated episodes (OR = 0.18, 95%CI: 0.11-0.30) and recurrent episodes (OR = 0.46, 95%CI: 0.23-0.95).

CONCLUSION: Overall adherence with the SHEA/IDSA guidelines for management of CDAD at a tertiary medical center was poor; this was most pronounced in severe, severe-complicated and recurrent cases. Educational interventions aimed at improving guideline adherence are warranted.

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.

Epidemiology of Clostridium difficile infection in Asia

While Clostridium difficile infection (CDI) has come to prominence as major epidemics have occurred in North America and Europe over the recent decade, awareness and surveillance of CDI in Asia have remained poor. Limited studies performed throughout Asia indicate that CDI is also a significant nosocomial pathogen in this region, but the true prevalence of CDI remains unknown. A lack of regulated antibiotic use in many Asian countries suggests that the prevalence of CDI may be comparatively high. Molecular studies indicate that ribotypes 027 and 078, which have caused significant outbreaks in other regions of the world, are rare in Asia. However, variant toxin A-negative/toxin B-positive strains of ribotype 017 have caused epidemics across several Asian countries. Ribotype smz/018 has caused widespread disease across Japan over the last decade and more recently emerged in Korea. This review summarises current knowledge on CDI in Asian countries.