Susceptibility testing of Clostridium difficile against metronidazole and vancomycin by disk diffusion and Etest

Fecal Shedding of Clostridioides difficile in Calves in Sao Paulo State, Brazil

OBJECTIVE

This study aimed to evaluate the fecal shedding of C. difficile in calves on farms in Sao Paulo State, Brazil.

MATERIALS AND METHODS

Fecal samples (n=300) were collected from diarrheic (n=78) and nondiarrheic (n=222) calves less than 60 days of age from 20 farms. Fecal samples were inoculated into enrichment broth supplemented with taurocholate and cultured under anaerobic conditions. Colonies suspected to be C. difficile were harvested for DNA extraction and then multiplex PCR for the detection of genes encoding toxins A and B and binary toxins. All toxigenic isolates were ribotyped and tested for antimicrobial susceptibility, and five selected strains were subjected to whole-genome sequencing to determine their sequence type.

RESULTS AND DISCUSSION

C. difficile was isolated from 29.3% (88/300) of the samples. All toxigenic isolates (17/88, 19.3%) were classified as ribotypes RT046 (13/17 -79.47%, A+B+ CDT-) and RT126 (4/17=20.53%, A+B+ CDT+). The sequenced strains from RT046 were classified as ST35 (Clade 1), while those from RT126 were classified as ST11 (Clade 5). No associations between the epidemiological factors in any of the groups and C. difficile isolation were observed. Most of the toxigenic isolates (16/17=94.41%) were classified as multidrug-resistant. Calves can be an important source of toxigenic C. difficile strains, including multidrug-resistant isolates from ribotypes commonly observed in humans.

Evaluation of the Potential of Chitosan Nanoparticles as a Delivery Vehicle for Gentamicin for the Treatment of Osteomyelitis

Chitosan nanoparticle delivery systems have the potential for enhancing bone healing and addressing osteomyelitis. The objective was to deliver antimicrobial agents capable of preventing or treating osteomyelitis. Each formulation was optimized to achieve desired characteristics in terms of size (ranging from 100 to 400 nm), PDI (less than 0.5), zeta potential (typically negative), and in vitro release profiles for gentamicin. Entrapment percentages varied with gentamicin ranging from 10% to 65%. The chitosan nanoparticles exhibited substantial antimicrobial efficacy, particularly against P. aeruginosa and MRSA, with zones of inhibition ranging from 13 to 24 mm and a complete reduction in colony forming units observed between 3 and 24 h. These chitosan nanoparticle formulations loaded with antimicrobials hold promise for addressing orthopedic complications.

Fifty years devoted to anaerobes: historical, lessons, and highlights

Renew interest and enthusiasm for anaerobes stem from both technological improvements (culture media, production of an adequate anaerobic atmosphere, identification methods) and greater awareness on the part of clinicians. Anaerobic infections were historically treated empirically, targeting the species known to be involved in each type of infection. Prevotella, fusobacteria, and Gram-positive cocci (GPAC) were considered responsible for infections above the diaphragm whereas for intra-abdominal infections, Bacteroides of the fragilis group (BFG), GPAC and clostridia were predominantly implicated. The antibiotic susceptibility of anaerobes was only taken into consideration by the clinician in the event of treatment failure or when faced with infections by multidrug-resistant bacteria (MDR). The evolution of antibiotic resistance together with clinical failures due to the absence of detection of hetero-resistant clones has resulted in a greater need for accessible antibiotic susceptibility testing (AST) and disc diffusion method. Improved isolation and identification of anaerobes, along with the availability of accessible and robust methods for performing AST, will ensure that treatment, whether empirical or guided by an antibiogram, will lead to better outcomes for anaerobic infections.

Evaluation of disk diffusion method for testing the rifampicin, erythromycin, and tetracycline susceptibility of Clostridioides (prev. Clostridium) difficile

INTRODUCTION

Antimicrobial resistance (AMR) is one of the greatest threats to animal and public health. Clostridioides (prev. Clostridium) difficile is a major burden to healthcare and a relevant AMR gene reservoir. Despite the known importance of AMR in C. difficile epidemiology and treatment, antimicrobial susceptibility testing for this pathogen is still based on the determination of the minimal inhibitory concentration (MIC) by the agar dilution method, which is technically demanding and labor-intensive. In this study, the disk diffusion method was used to evaluate the susceptibility of C. difficile to erythromycin, rifampicin, and tetracycline.

MATERIAL AND METHODS

A total of 155 isolates isolated between 2011 and 2022 from humans and animals in Brazil were simultaneously tested using the disk diffusion method and the epsilometer test (Etest) for these three antimicrobials on Brucella blood agar supplemented with vitamin K and hemin.

RESULTS

The results suggest that disk diffusion can be an interesting routine tool to identify erythromycin- and rifampicin-resistant C. difficile isolates (≥20 mm cut-off) and wild type (WT) strains (≥28 mm). However, the disk diffusion protocol tested in this study does not seem suitable for tetracycline because of the common misclassification of resistant strains.

A Riboswitch-Driven Era of New Antibacterials

Riboswitches are structured non-coding RNAs found in the 5′ UTR of important genes for bacterial metabolism, virulence and survival. Upon the binding of specific ligands that can vary from simple ions to complex molecules such as nucleotides and tRNAs, riboswitches change their local and global mRNA conformations to affect downstream transcription or translation. Due to their dynamic nature and central regulatory role in bacterial metabolism, riboswitches have been exploited as novel RNA-based targets for the development of new generation antibacterials that can overcome drug-resistance problems. During recent years, several important riboswitch structures from many bacterial representatives, including several prominent human pathogens, have shown that riboswitches are ideal RNA targets for new compounds that can interfere with their structure and function, exhibiting much reduced resistance over time. Most interestingly, mainstream antibiotics that target the ribosome have been shown to effectively modulate the regulatory behavior and capacity of several riboswitches, both in vivo and in vitro, emphasizing the need for more in-depth studies and biological evaluation of new antibiotics. Herein, we summarize the currently known compounds that target several main riboswitches and discuss the role of mainstream antibiotics as modulators of T-box riboswitches, in the dawn of an era of novel inhibitors that target important bacterial regulatory RNAs.

Clostridioides difficile epidemiology in the Middle and the Far East

OBJECTIVES

Clostridioides difficile is an important pathogen of healthcare-associated gastrointestinal infections. Recently, an increased number of C. difficile infection (CDI) surveillance data has been reported from Asia. The aim of this review is to summarize the data on the prevalence, distribution and molecular epidemiology of CDI in the Middle and the Far East.

METHODS

Literature was drawn from a search of PubMed up to September 30, 2021.

RESULTS

The meta-analysis of data from 111 studies revealed the pooled CDI prevalence rate in the Middle and the Far East of 12.4% (95% CI 11.4-13.3); 48 studies used PCR for CDI laboratory diagnoses. The predominant types (RT)/sequence type (ST) differ between individual countries (24 studies, 14 countries). Frequently found RTs were 001, 002, 012, 017, 018 and 126; RT017 was predominant in the Far East. The epidemic RT027 was detected in 8 countries (22 studies), but its predominance was reported only in three studies (Israel and Iran). The contamination of vegetable and meat or meat products and/or intestinal carriage of C. difficile in food and companion animals have been reported; the C. difficile RTs/STs identified overlapped with those identified in humans.

CONCLUSIONS

A large number of studies on CDI prevalence in humans from the Middle and the Far East have been published; countries with no available data were identified. The number of studies on C. difficile from non-human sources is limited. Comparative genomic studies of isolates from different sources are needed.

[Updated review of Clostridium difficile infection in elderly]

Clostridium difficile infection is the most common cause of health care-associated diarrhoea, and its incidence increases with age. Clinical challenges, risk of resistance to treatment, risk of recurrence, and treatment responses are different in elderly. The aim of this review is to discuss the updated epidemiology, pathophysiology, diagnosis, and therapeutic management of C. difficile infection in elderly with the available data.

Proteomic Signatures of Clostridium difficile Stressed with Metronidazole, Vancomycin, or Fidaxomicin

The anaerobic pathogen Clostridium difficile is of growing significance for the health care system due to its increasing incidence and mortality. As C. difficile infection is both supported and treated by antibiotics, a deeper knowledge on how antimicrobial agents affect the physiology of this important pathogen may help to understand and prevent the development and spreading of antibiotic resistant strains. As the proteomic response of a cell to stress aims at counteracting the harmful effects of this stress, it can be expected that the pattern of a pathogen’s responses to antibiotic treatment will be dependent on the antibiotic mechanism of action. Hence, every antibiotic treatment is expected to result in a specific proteomic signature characterizing its mode of action. In the study presented here, the proteomic response of C. difficile 630∆erm to vancomycin, metronidazole, and fidaxomicin stress was investigated on the level of protein abundance and protein synthesis based on 2D PAGE. The quantification of 425 proteins of C. difficile allowed the deduction of proteomic signatures specific for each drug treatment. Indeed, these proteomic signatures indicate very specific cellular responses to each antibiotic with only little overlap of the responses. Whereas signature proteins for vancomycin stress fulfil various cellular functions, the proteomic signature of metronidazole stress is characterized by alterations of proteins involved in protein biosynthesis and protein degradation as well as in DNA replication, recombination, and repair. In contrast, proteins differentially expressed after fidaxomicin treatment can be assigned to amino acid biosynthesis, transcription, cell motility, and the cell envelope functions. Notably, the data provided by this study hint also at so far unknown antibiotic detoxification mechanisms.

Prevalence of Clostridium difficile Isolated from Beef and Chicken Meat Products in Turkey

The concern about the possibility of food can be a vehicle for the transmission of Clostridium difficile to humans has been raised recently due to the similarities among the strains isolated from patients, foods and food animals. In this study, therefore, the prevalence of C. difficile was investigated in beef and chicken meat products collected from 57 different butcher shops, markets and fast food restaurants in Sakarya province of Turkey. Two out of 101 samples (1.98%) was positive for C. difficile indicating a very low prevalence. The pathogen was isolated from an uncooked meatball sample and a cooked meat döner sample, whereas not detected in chicken meat samples. The meatball isolate was resistant to vancomycin and tetracycline, while the cooked meat döner isolate was resistant to vancomycin and metronidazole. Both isolates were sensitive to moxifloxacin and clindamycin. Toxins A and B were not detected. This study reveals the presence of C. difficile in further processed beef products in Turkey.

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.

Surveillance of antibiotic resistance among common Clostridium difficile ribotypes in Hong Kong

Incidence of Clostridium difficile infection (CDI) is rapidly increasing and it poses a major health burden globally. However, data regarding the epidemiology of CDI in Asia are limited. We aimed to characterize the antimicrobial susceptibility patterns of common ribotypes of toxigenic C. difficile in Hong Kong. Fifty-three PCR ribotypes were identified among 284 toxigenic C. difficile clinical isolates. The five most prevalent ribotypes were 002 (13%), 017 (12%), 014 (10%), 012 (9.2%), and 020 (9.5%). All tested C. difficile strains remained susceptible to metronidazole, vancomycin, meropenem and piperacillin/tazobactam, but highly resistant to cephalosporins. Of the fluoroquinolones, highest resistance to ciprofloxacin was observed (99%), followed by levofloxacin (43%) and moxifloxacin (23%). The two newly emerged PCR ribotypes, 017 and 002, demonstrated high levels of co-resistance towards clindamycin, tetracycline, erythromycin and moxifloxacin. PCR ribotypes 017 and 002 with multi-drug resistance are rapidly emerging and continuous surveillance is important to monitor the epidemiology of C. difficile to prevent outbreaks of CDI.

Chemical Genomics, Structure Elucidation, and in Vivo Studies of the Marine-Derived Anticlostridial Ecteinamycin

A polyether antibiotic, ecteinamycin (1), was isolated from a marine Actinomadura sp., cultivated from the ascidian Ecteinascidia turbinata. 13C enrichment, high resolution NMR spectroscopy, and molecular modeling enabled elucidation of the structure of 1, which was validated on the basis of comparisons with its recently reported crystal structure. Importantly, ecteinamycin demonstrated potent activity against the toxigenic strain of Clostridium difficile NAP1/B1/027 (MIC = 59 ng/μL), as well as other toxigenic and nontoxigenic C. difficile isolates both in vitro and in vivo. Additionally, chemical genomics studies using Escherichia coli barcoded deletion mutants led to the identification of sensitive mutants such as trkA and kdpD involved in potassium cation transport and homeostasis supporting a mechanistic proposal that ecteinamycin acts as an ionophore antibiotic. This is the first antibacterial agent whose mechanism of action has been studied using E. coli chemical genomics. On the basis of these data, we propose ecteinamycin as an ionophore antibiotic that causes C. difficile detoxification and cell death via potassium transport dysregulation.

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.

Clostridium difficile Infection and Patient-Specific Antimicrobial Resistance Testing Reveals a High Metronidazole Resistance Rate

BACKGROUND

Clostridium difficile (CD) infection (CDI) causes marked morbidity and mortality, accounting for large healthcare expenditures annually. Current CDI treatment guidelines focus on clinical markers of patient severity to determine the preferred antibiotic regimen of metronidazole versus vancomycin. The antimicrobial resistance patterns for patients with CD are currently unknown.

AIM

The aim of this study was to define the antimicrobial resistance patterns for CD.

METHODS

This study included all patients with stools sent for CD testing to a private laboratory (DRG Laboratory, Alpharetta, Georgia) in a 6-month period from across the USA. Patient data was de-identified, with only age, gender, and zip-code available per laboratory protocol. All samples underwent PCR testing followed by hybridization for CD toxin regions A and B. Only patients with CD-positive PCR were analyzed. Antimicrobial resistance testing using stool genomic DNA evaluated presence of imidazole- and vancomycin-resistant genes using multiplex PCR gene detection.

RESULTS

Of 2743, 288 (10.5%) stool samples were positive for CD. Six were excluded per protocol. Of 282, 193 (69.4%) were women, and average age was 49.4 ± 18.7 years. Of 282, 62 were PCR positive for toxins A and B, 160 for toxin A positive alone, and 60 for toxin B positive alone. Antimicrobial resistance testing revealed 134/282 (47.5%) patients resistant to imidazole, 17 (6.1%) resistant to vancomycin, and 9 (3.2%) resistant to imidazole and vancomycin.

CONCLUSIONS

CD-positive patients with presence of imidazole-resistant genes from stool DNA extract was a common phenomenon, while vancomycin resistance was uncommon. Similar to treatment of other infections, antimicrobial resistance testing should play a role in CDI clinical decision-making algorithms to enable more expedited and cost-effective delivery of patient care.

Routine disc diffusion antimicrobial susceptibility testing of Clostridium difficile and association with PCR ribotype 027

Reduced susceptibility to metronidazole and vancomycin in Clostridium difficile has been reported, which emphasises the need for simple antimicrobial susceptibility testing methods. The aim of this study was to apply a published disc diffusion method and zone diameter breakpoint correlates to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological minimum inhibitory concentration (MIC) cut-off values in a routine setting. Metronidazole and vancomycin zone diameters from 2702 isolates were recorded. Fifteen isolates had a metronidazole zone diameter below the published breakpoint (<23 mm) and five isolates had a vancomycin zone diameter below the published breakpoint (<19 mm), most of which were polymerase chain reaction (PCR) ribotype 027. The total number of PCR ribotype 027 was 29 (1.1 %). Overall, C. difficile PCR ribotype 027 isolates had smaller zone diameters than non-027 isolates. The disc diffusion method is very simple and inexpensive, and the published zone diameter breakpoints will detect C. difficile isolates with reduced susceptibility to metronidazole and vancomycin.

Novel riboswitch-binding flavin analog that protects mice against Clostridium difficile infection without inhibiting cecal flora

Novel mechanisms of action and new chemical scaffolds are needed to rejuvenate antibacterial drug discovery, and riboswitch regulators of bacterial gene expression are a promising class of targets for the discovery of new leads. Herein, we report the characterization of 5-(3-(4-fluorophenyl)butyl)-7,8-dimethylpyrido[3,4-b]quinoxaline-1,3(2H,5H)-dione (5FDQD)-an analog of riboflavin that was designed to bind riboswitches that naturally recognize the essential coenzyme flavin mononucleotide (FMN) and regulate FMN and riboflavin homeostasis. In vitro, 5FDQD and FMN bind to and trigger the function of an FMN riboswitch with equipotent activity. MIC and time-kill studies demonstrated that 5FDQD has potent and rapidly bactericidal activity against Clostridium difficile. In C57BL/6 mice, 5FDQD completely prevented the onset of lethal antibiotic-induced C. difficile infection (CDI). Against a panel of bacteria representative of healthy bowel flora, the antibacterial selectivity of 5FDQD was superior to currently marketed CDI therapeutics, with very little activity against representative strains from the Bacteroides, Lactobacillus, Bifidobacterium, Actinomyces, and Prevotella genera. Accordingly, a single oral dose of 5FDQD caused less alteration of culturable cecal flora in mice than the comparators. Collectively, these data suggest that 5FDQD or closely related analogs could potentially provide a high rate of CDI cure with a low likelihood of infection recurrence. Future studies will seek to assess the role of FMN riboswitch binding to the mechanism of 5FDQD antibacterial action. In aggregate, our results indicate that riboswitch-binding antibacterial compounds can be discovered and optimized to exhibit activity profiles that merit preclinical and clinical development as potential antibacterial therapeutic agents.

Incorrect diagnosis of Clostridium difficile infection in a university hospital in Japan

Physicians often fail to suspect Clostridium difficile infection (CDI) and many microbiology laboratories use suboptimal diagnostic techniques. To estimate the extent of and reasons for incorrect diagnosis of CDI in Japan, we investigated toxigenic C. difficile isolated from all stool culture samples and clinical course. Over a 12-month period in 2010, all stool culture samples (n = 975) submitted from inpatients in a university hospital in Japan were cultured for C. difficile and routine microbiological testing was conducted. In total, 177 C. difficile isolates were recovered, and 127 isolates were toxigenic. Among the toxin-A-positive/toxin-B-positive isolates, 12 were also positive for the binary toxin gene. However, clinically important ribotypes, such as 027 and 078, were not identified. A total of 58 (45.7%) cases with toxigenic C. difficile had unformed stool, and the incidence CDI was 1.6 cases per 10,000 patient-days. Of these 58 cases, 40 were not diagnosed in routine testing due to a lack of clinical suspicion (24.1%, 14/58) or a negative C. difficile toxin assay result (44.8%, 26/58). A stool toxin assay was performed in 54 patients (78.2%, 54/69) who did not have unformed stool. The present study demonstrated that a significant number of CDI cases in Japan might be overlooked or misdiagnosed in clinical practice due to a lack of clinical suspicion and limitations of microbiological testing for CDI in Japan. Providing education to promote awareness of CDI among physicians is important to improve the accuracy of diagnosis in Japan.

Association of tcdA+/tcdB+ Clostridium difficile Genotype with Emergence of Multidrug-Resistant Strains Conferring Metronidazole Resistant Phenotype

Background:

Reduced susceptibility of Clostridium difficile to antibiotics is problematic in clinical settings. There is new evidence indicating the cotransfer of toxin-encoding genes and conjugative transposons encoding resistance to antibiotics among different C. difficile strains. To analyze this association, in the current study, we evaluated the frequency of toxigenic C. difficile among the strains with different multidrug-resistant (MDR) profiles in Iran.

Methods:

Antimicrobial susceptibility patterns and minimal inhibitory concentrations (MIC) of the isolates were determined against metronidazole, imipenem, ceftazidime, amikacin, and ciprofloxacin by agar dilution method. The association of the resistance profiles and toxigenicity of the strains were studied by PCR targeting tcdA and tcdB genes.

Results:

Among 86 characterized strains, the highest and lowest resistance rates were related to ciprofloxacin (97%) and metronidazole (5%), respectively. The frequency of resistance to other antibiotics was as follow: imipenem (48%), ceftazidime (76%), and amikacin (76.5%). Among the resistant strains, double drug resistance and MDR phenotypes were detected in the frequencies of 10.4% and 66.2%, respectively. All of the metronidazole-resistant strains belonged to tcdA ⁺/tcdB ⁺ genotype with triple or quintuple drug resistance phenotypes. MIC₅₀ and MIC₉₀ for this antibiotic was equally ≤ 8 μg/ml.

Conclusion:

These results proposed the association of tcdA ⁺/tcdB ⁺ genotype of C. difficile and the emergence of resistance strains to broad-spectrum antibiotics and metronidazole.

Impact of clinical awareness and diagnostic tests on the underdiagnosis of Clostridium difficile infection

A multicenter study of Clostridium difficile infection (CDI) performed during 2008 in Spain revealed that two of every three episodes went undiagnosed or were misdiagnosed owing to nonsensitive diagnostic tests or lack of clinical suspicion and request. Since then, efforts have been made to improve the diagnostic tests used by laboratories and to increase the awareness of this disease among both clinicians and microbiologists. Our objective was to evaluate the impact of these efforts by assessing the current magnitude of underdiagnosis of CDI in Spain using two point-prevalence studies performed on one day each in January and July of 2013. A total of 111 Spanish laboratories selected all unformed stool specimens received for microbiological diagnosis on these days, and toxigenic culture was performed at a central reference laboratory. Toxigenic isolates were characterized both pheno- and genotypically. The reference laboratory detected 103 episodes of CDI in patients aged 2 years or more. Half (50.5 %) of the episodes were not diagnosed in the participating laboratories, owing to insensitive diagnostic tests (15.5 %) or the lack of clinical suspicion and request (35.0 %). The main ribotypes were 014, 078/126, 001/072, and 106. Ribotype 027 caused 2.9 % of all cases. Despite all the interventions undertaken, CDI remains a highly neglected disease because of the lack of sensitive diagnostic tests in some institutions and, especially, the absence of clinical suspicion, mainly in patients with community-associated CDI. Toxigenic C. difficile should be routinely sought in unformed stools sent for microbiological diagnosis, regardless of their origin.

Vancomycin Enemas as Adjunctive Therapy for Clostridium difficile Infection

Background

For severe, complicated Clostridium difficile infection (CDI), concomitant treatment with IV metronidazole and oral vancomycin is usually prescribed. Sometimes vancomycin per rectum (VPR) is added to increase colonic drug delivery. Our purpose was to examine clinical outcomes of patients with CDI treated with VPR and compare results to a matched control group.

Methods

This was a retrospective case-control study in a setting of tertiary-care ICU on diarrhea patients with a positive toxin test for C. difficile. We identified all ICU patients prescribed VPR from January 2003 to December 2013. The dose of VPR mixed in 100 cc of tap water ranged from 125 to 250 mg Q 6 - 8 hours. All patients had diarrhea and a positive test for C. difficile toxin. Included patients received ≥ 4 doses of VPR. The primary outcome was the combined endpoint of colon surgery or death. We matched VPR cases 1:2 with CDI controls that had identical APACHE II scores.

Results

We identified 24 CDI patients who received VPR and met inclusion criteria: 11 male, mean age 61.8 ± 15.9 years. All patients received concomitant CDI therapy. Four patients (16.7%) required colectomy, and overall mortality was 45.8%. For the 48 controls, need for surgery was identical (16.7%; P = 1.00). The mortality rate also did not differ (41.7%; P = 0.74). For the combined outcome of surgery or death, the rate was 45.8% for the controls and 50.0% for the VPR group (P = 0.73).

Conclusion

In a case-control study, the use of VPR was not demonstrated to reduce the need for colectomy or decrease mortality. Based on our modest sample size and failure to show efficacy, we cannot strongly advocate for the use of VPR.

Ambush of Clostridium difficile spores by ramoplanin: activity in an in vitro model

Clostridium difficile infection (CDI) is a gastrointestinal disease caused by C. difficile, a spore-forming bacterium that in its spore form is tolerant to standard antimicrobials. Ramoplanin is a glycolipodepsipeptide antibiotic that is active against C. difficile with MICs ranging from 0.25 to 0.50 μg/ml. The activity of ramoplanin against the spores of C. difficile has not been well characterized; such activity, however, may hold promise, since posttreatment residual intraluminal spores are likely elements of disease relapse, which can impact more than 20% of patients who are successfully treated. C. difficile spores were found to be stable in deionized water for 6 days. In vitro spore counts were consistently below the level of detection for 28 days after even brief (30-min) exposure to ramoplanin at concentrations found in feces (300 μg/ml). In contrast, suppression of spore counts was not observed for metronidazole or vancomycin at human fecal concentrations during treatment (10 μg/ml and 500 μg/ml, respectively). Removal of the C. difficile exosporium resulted in an increase in spore counts after exposure to 300 μg/ml of ramoplanin. Therefore, we propose that rather than being directly sporicidal, ramoplanin adheres to the exosporium for a prolonged period, during which time it is available to attack germinating cells. This action, in conjunction with its already established bactericidal activity against vegetative C. difficile forms, supports further evaluation of ramoplanin for the prevention of relapse after C. difficile infection in patients.

Luminal Toxin-Binding Agents for Clostridium difficile Infection

OBJECTIVE

To systematically search the literature for trials evaluating luminal toxin-binding agents (LTBAs) for Clostridium difficile infection (CDI).

METHODS

A systematic search was conducted utilizing PubMed and International Pharmaceutical Abstracts with the following terms: anion-exchange resins, C difficile, cholestyramine, tolevamer, and colestipol. Articles were included if published in the English language and reported clinical outcomes of more than 5 adult humans with CDI treated with LTBAs.

RESULTS

Nearly all clinical trials evaluated LTBA as monotherapy for CDI and LTBAs are inferior to standard therapy. In contemporary practice, LTBAs are employed as adjunctive or sequential therapy for which there is a paucity of data. Some data suggest potential efficacy for recurrent CDI. Current guidelines for CDI assert LTBAs are contraindicated due to drug-drug interactions with vancomycin. However, the impact of this interaction on clinical outcomes has not been evaluated, and it is unknown whether higher doses of vancomycin or separating the administration of LTBAs from vancomycin would mitigate this interaction.

CONCLUSION

LTBA monotherapy is inferior to vancomycin and metronidazole for CDI. Some data indicate possible benefit in reducing recurrent CDI, but outcomes with adjunctive and/or sequential LTBAs are unavailable. Further studies are needed to investigate the role of LTBAs for CDI.

Clinical Practice Guidelines for Clostridium difficile Infection in Adults: 2010 Update by the Society for Healthcare Epidemiology of America (SHEA) and the Infectious Diseases Society of America (IDSA)

Since publication of the Society for Healthcare Epidemiology of America position paper onClostridium difficileinfection in 1995, significant changes have occurred in the epidemiology and treatment of this infection.C. difficileremains the most important cause of healthcare-associated diarrhea and is increasingly important as a community pathogen. A more virulent strain ofC. difficilehas been identified and has been responsible for more-severe cases of disease worldwide. Data reporting the decreased effectiveness of metronidazole in the treatment of severe disease have been published. Despite the increasing quantity of data available, areas of controversy still exist. This guideline updates recommendations regarding epidemiology, diagnosis, treatment, and infection control and environmental management.

Clostridium perfringens and Clostridium difficile in cooked beef sold in Côte d'Ivoire and their antimicrobial susceptibility

The aim of this study was to evaluate the prevalence of Clostridium difficile and Clostridium perfringens in cooked beef sold in the streets in Côte d'Ivoire and their antimicrobial susceptibility. A total of 395 kidney and flesh samples of cooked beef were collected from vendors at Abidjan and subjected to C. difficile and C. perfringens isolation and identification by using biochemical tests, API 20A system and PCR detection. Subsequently, the antimicrobial susceptibility test was performed for confirmed isolates. Our results showed the prevalence of 12.4% for C. difficile (11.04% in kidney and 13.45% in flesh) and 5.06% for C. perfringens (2.32% in kidney and 7.17% in flesh). Metronidazole and vancomycin remained the most potent antimicrobial agents against C. difficile while metronidazole and penicillin G were the most potent agents against C. perfringens. The resistance rates to tetracycline, doxycycline, chloramphenicol and erythromycin against C. difficile and C. perfringens isolates ranged from 2.05% to 8.16% and from 20% to 50%, respectively. Among all antimicrobial agents tested against C. difficile, percentages of resistance to quinolones ciprofloxacin, norfloxacin and nalidixic acid as well as to gentamicin and cefotaxime were the highest. Eight resistant phenotypes were defined for C. difficile isolates and eleven resistant phenotypes for C. perfringens isolates. Clindamycin/gentamicin/cefotaxime/ciprofloxacin/norfloxacin/nalidixic acid resistance was the most common phenotype for C. difficile (55.10% of isolates) while norfloxacin/nalidixic acid resistance was the most common phenotype for C. perfringens (20% of isolates).

Antianaerobic antimicrobials: spectrum and susceptibility testing

Susceptibility testing of anaerobic bacteria recovered from selected cases can influence the choice of antimicrobial therapy. The Clinical and Laboratory Standards Institute (CLSI) has standardized many laboratory procedures, including anaerobic susceptibility testing (AST), and has published documents for AST. The standardization of testing methods by the CLSI allows comparisons of resistance trends among various laboratories. Susceptibility testing should be performed on organisms recovered from sterile body sites, those that are isolated in pure culture, or those that are clinically important and have variable or unique susceptibility patterns. Organisms that should be considered for individual isolate testing include highly virulent pathogens for which susceptibility cannot be predicted, such as Bacteroides, Prevotella, Fusobacterium, and Clostridium spp.; Bilophila wadsworthia; and Sutterella wadsworthensis. This review describes the current methods for AST in research and reference laboratories. These methods include the use of agar dilution, broth microdilution, Etest, and the spiral gradient endpoint system. The antimicrobials potentially effective against anaerobic bacteria include beta-lactams, combinations of beta-lactams and beta-lactamase inhibitors, metronidazole, chloramphenicol, clindamycin, macrolides, tetracyclines, and fluoroquinolones. The spectrum of efficacy, antimicrobial resistance mechanisms, and resistance patterns against these agents are described.

Diagnosis of Clostridium difficile infection: an ongoing conundrum for clinicians and for clinical laboratories

Clostridium difficile is a formidable nosocomial and community-acquired pathogen, causing clinical presentations ranging from asymptomatic colonization to self-limiting diarrhea to toxic megacolon and fulminant colitis. Since the early 2000s, the incidence of C. difficile disease has increased dramatically, and this is thought to be due to the emergence of new strain types. For many years, the mainstay of C. difficile disease diagnosis was enzyme immunoassays for detection of the C. difficile toxin(s), although it is now generally accepted that these assays lack sensitivity. A number of molecular assays are commercially available for the detection of C. difficile. This review covers the history and biology of C. difficile and provides an in-depth discussion of the laboratory methods used for the diagnosis of C. difficile infection (CDI). In addition, strain typing methods for C. difficile and the evolving epidemiology of colonization and infection with this organism are discussed. Finally, considerations for diagnosing C. difficile disease in special patient populations, such as children, oncology patients, transplant patients, and patients with inflammatory bowel disease, are described. As detection of C. difficile in clinical specimens does not always equate with disease, the diagnosis of C. difficile infection continues to be a challenge for both laboratories and clinicians.

Proteomic analysis of a NAP1 Clostridium difficile clinical isolate resistant to metronidazole

BACKGROUND

Clostridium difficile is an anaerobic, Gram-positive bacterium that has been implicated as the leading cause of antibiotic-associated diarrhea. Metronidazole is currently the first-line treatment for mild to moderate C. difficile infections. Our laboratory isolated a strain of C. difficile with a stable resistance phenotype to metronidazole. A shotgun proteomics approach was used to compare differences in the proteomes of metronidazole-resistant and -susceptible isolates.

METHODOLOGY/PRINCIPAL FINDINGS

NAP1 C. difficile strains CD26A54_R (Met-resistant), CD26A54_S (reduced- susceptibility), and VLOO13 (Met-susceptible) were grown to mid-log phase, and spiked with metronidazole at concentrations 2 doubling dilutions below the MIC. Peptides from each sample were labeled with iTRAQ and subjected to 2D-LC-MS/MS analysis. In the absence of metronidazole, higher expression was observed of some proteins in C. difficile strains CD26A54_S and CD26A54_R that may be involved with reduced susceptibility or resistance to metronidazole, including DNA repair proteins, putative nitroreductases, and the ferric uptake regulator (Fur). After treatment with metronidazole, moderate increases were seen in the expression of stress-related proteins in all strains. A moderate increase was also observed in the expression of the DNA repair protein RecA in CD26A54_R.

CONCLUSIONS/SIGNIFICANCE

This study provided an in-depth proteomic analysis of a stable, metronidazole-resistant C. difficile isolate. The results suggested that a multi-factorial response may be associated with high level metronidazole-resistance in C. difficile, including the possible roles of altered iron metabolism and/or DNA repair.

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.

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.

Analysis of anti-Clostridium difficile activity of thuricin CD, vancomycin, metronidazole, ramoplanin, and actagardine, both singly and in paired combinations

Due to the ongoing problem of recurrence of Clostridium difficile-associated diarrhea following antibiotic treatment, there is an urgent need for alternative treatment options. We assessed the MICs of five antimicrobials singly and in combinations against a range of C. difficile clinical isolates. Ramoplanin-actagardine combinations were particularly effective, with partial synergistic/additive effects observed against 61.5% of C. difficile strains tested.

Antimicrobial susceptibility testing of Clostridium difficile using EUCAST epidemiological cut-off values and disk diffusion correlates

With the emergence of reduced susceptibility of Clostridium difficile to metronidazole and vancomycin the value of antimicrobial susceptibility testing has increased. The aim of our study was to evaluate disk diffusion for susceptibility testing of C. difficile by comparing disk diffusion results with MICs from gradient tests and to propose zone diameter breakpoint correlates for the EUCAST epidemiological cut-off values (ECOFFs) recently published. We tested 211 clinical isolates of C. difficile, from patients with diarrhoea hospitalized at Aarhus and Odense University Hospitals, Denmark. Furthermore, ten clinical isolates of C. difficile from the Anaerobe Reference Laboratory, University Hospital of Wales, with known reduced susceptibility to either metronidazole or vancomycin, were included. Isolates were tested with Etest gradient strips and disk diffusion towards metronidazole, vancomycin and moxifloxacin on Brucella Blood Agar supplemented with hemin and vitamin K. We found an excellent agreement between inhibition zone diameter and MICs. For each MIC value, the inhibition zones varied from 0 to 8 mm, with 93% of values within 6 mm for metronidazole, 95% of values within 4 mm for vancomycin, and 98% of values within 4 mm for moxifloxacin. With proposed zone diameter breakpoints for metronidazole, vancomycin and moxifloxacin of WT ≥ 23 mm, WT ≥ 19 and WT ≥ 20 mm, respectively, we found no very major errors and only major errors below 2%. In conclusion, we suggest that disk diffusion is an option for antimicrobial susceptibility testing of C. difficile.

The undiagnosed cases of Clostridium difficile infection in a whole nation: where is the problem?

Underdiagnosis of Clostridium difficile infection (CDI) because of lack of clinical suspicion or the use of non-sensitive diagnostic techniques is a known problem whose real magnitude has not yet been quantified. In order to estimate the extent of this underdiagnosis, we performed C. difficile cultures on all unformed stool specimens sent-irrespective of the type of request-to a series of laboratories in Spain on a single day. The specimens were cultured, and isolates were characterized at a central reference laboratory. A total of 807 specimens from 730 patients aged ≥ 2 years were selected from 118 laboratories covering 75.4% of the Spanish population. The estimated rate of hospital-acquired CDI was 2.4 episodes per 1000 admissions or 3.8 episodes per 10,000 patient-days. Only half of the episodes occurred in patients hospitalized for >2 days. Two of every three episodes went undiagnosed or were misdiagnosed, owing to non-sensitive diagnostic tests (19.0%) or lack of clinical suspicion and request (47.6%; mostly young people or non-hospitalized patients). The main ribotypes were 014/020 (20.5%), 001 (18.2%), and 126/078 (18.2%). No ribotype 027 strains were detected. Strains were fully susceptible to metronidazole and vancomycin. CDI was underdiagnosed in diarrhoeic stools in a high proportion of episodes, owing to the use of non-sensitive techniques or lack of clinical suspicion, particularly in people aged <65 years or patients with community-acquired diarrhoea. C. difficile toxins should be routinely sought in unformed stools of any origin sent for microbiological diagnosis. The ribotype 027 clone has not yet disseminated in Spain.

Fecal microbiota transplantation for recurrent clostridium difficile infection

With the increasing prevalence of recurrent/refractory Clostridium difficile infection (CDI), alternative treatments to the standard antibiotic therapies are being sought. One of the more controversial of such alternative treatments is fecal microbiota transplantation (FMT). Although the notion of FMT is foreign-even startling-and not esthetic to most people, the concept has been around for many decades. Its benefit and efficacy dates back >50 years to its use for staphylococcal pseudomembranous colitis, and now FMT is showing a great promise as an inexpensive, safe, and highly efficient treatment for recurrent and refractory CDI. Moreover, with a better understanding of the intricacies of the colonic microbiome and its role in colonic pathophysiology, FMT has the potential to become the standard of care for CDI treatment, and a potential answer to other intestinal disorders in years to come.

Treatment of refractory and recurrent Clostridium difficile infection

The incidence of Clostridium difficile infection (CDI) has increased since 2000, with greater numbers of severe cases reported, in part due to the emergence of a hypervirulent strain. Initial therapy with metronidazole is still recommended for mild to moderate CDI, but vancomycin is recommended for first-line therapy of severe CDI. Colectomy could be life-saving for some patients with severe disease that does not respond to maximal medical therapy. Recurrent CDI is a challenge to treat; no single effective therapy currently exists. Treatments include antibiotics, adjunct probiotics, fecal microbiota transplant and immune approaches. This Review discusses the various therapeutic approaches used for the treatment of refractory and recurrent CDI.

Faecal pharmacokinetics of orally administered vancomycin in patients with suspected Clostridium difficile infection

Background

Oral vancomycin (125 mg qid) is recommended as treatment of severe Clostridium difficile infection (CDI). Higher doses (250 or 500 mg qid) are sometimes recommended for patients with very severe CDI, without supporting clinical evidence. We wished to determine to what extent faecal levels of vancomycin vary according to diarrhoea severity and dosage, and whether it is rational to administer high-dose vancomycin to selected patients.

Methods

We recruited hospitalized adults suspected to have CDI for whom oral vancomycin (125, 250 or 500 mg qid) had been initiated. Faeces were collected up to 3 times/day and levels were measured with the AxSYM fluorescence polarization immunoassay.

Results

Fifteen patients (9 with confirmed CDI) were treated with oral vancomycin. Patients with ≥4 stools daily presented lower faecal vancomycin levels than those with a lower frequency. Higher doses of oral vancomycin (250 mg or 500 mg qid) led to consistently higher faecal levels (> 2000 mg/L), which were 3 orders of magnitude higher than the MIC₉₀ of vancomycin against C. difficile. One patient receiving 125 mg qid had levels below 50 mg/L during the first day of treatment.

Conclusions

Faecal levels of vancomycin are proportional to the dosage administered and, even in patients with increased stool frequency, much higher than the MIC₉₀. Patients given the standard 125 mg qid dosage might have low faecal levels during the first day of treatment. A loading dose of 250 mg or 500 mg qid during the first 24-48 hours followed by the standard dosage should be evaluated in larger studies, since it might be less disruptive to the colonic flora and save unnecessary costs.

Anaerobic bacteria and antibiotics: What kind of unexpected resistance could I find in my laboratory tomorrow?

The purpose of this article is to set out some important considerations on the main emerging antibiotic resistance patterns among anaerobic bacteria. The first point concerns the Bacteroides fragilis group and its resistance to the combination of β-lactam+β-lactamase inhibitor. When there is overproduction of cephalosporinase, it results in increased resistance to the β-lactams while maintaining susceptibility to β-lactams/β-lactamase inhibitor combinations. However, if another resistance mechanism is added, such as a loss of porin, resistances to β-lactam+β-lactamase inhibitor combinations may occur. The second point is resistance to metronidazole occurring due to nim genes. PCR detection of nim genes alone is not sufficient for predicting resistance to metronidazole; actual MIC determinations are required. Therefore, it can be assumed that other resistance mechanisms can also be involved. Although metronidazole resistance remains rare for the B. fragilis group, it has nevertheless been detected worldwide and also been observed spreading to other species. In some cases where there is only a decreased susceptibility, clinical failures may occur. The last point concerns resistance of Clostridium species to glycopeptides and lipopeptides. Low levels of resistance have been detected with these antibiotics. Van genes have been detected not only in clostridia but also in other species. In conclusion, antibiotic resistance involves different mechanisms and affects many anaerobic species and is spreading worldwide. This demonstrates the need to continue with antibiotic resistance testing and surveys in anaerobic bacteria.

The changing epidemiology of Clostridium difficile infections

The epidemiology of Clostridium difficile infection (CDI) has changed dramatically during this millennium. Infection rates have increased markedly in most countries with detailed surveillance data. There have been clear changes in the clinical presentation, response to treatment, and outcome of CDI. These changes have been driven to a major degree by the emergence and epidemic spread of a novel strain, known as PCR ribotype 027 (sometimes referred to as BI/NAP1/027). We review the evidence for the changing epidemiology, clinical virulence and outcome of treatment of CDI, and the similarities and differences between data from various countries and continents. Community-acquired CDI has also emerged, although the evidence for this as a distinct new entity is less clear. There are new data on the etiology of and potential risk factors for CDI; controversial issues include specific antimicrobial agents, gastric acid suppressants, potential animal and food sources of C. difficile, and the effect of the use of alcohol-based hand hygiene agents.

The changing epidemiology of Clostridium difficile infections

The epidemiology of Clostridium difficile infection (CDI) has changed dramatically during this millennium. Infection rates have increased markedly in most countries with detailed surveillance data. There have been clear changes in the clinical presentation, response to treatment, and outcome of CDI. These changes have been driven to a major degree by the emergence and epidemic spread of a novel strain, known as PCR ribotype 027 (sometimes referred to as BI/NAP1/027). We review the evidence for the changing epidemiology, clinical virulence and outcome of treatment of CDI, and the similarities and differences between data from various countries and continents. Community-acquired CDI has also emerged, although the evidence for this as a distinct new entity is less clear. There are new data on the etiology of and potential risk factors for CDI; controversial issues include specific antimicrobial agents, gastric acid suppressants, potential animal and food sources of C. difficile, and the effect of the use of alcohol-based hand hygiene agents.

Clostridium difficile and the disease it causes

Clostridium difficile is a spore-forming, toxin-producing, anaerobic bacterium abundant in soils and water. Frequent and early colonization of the human intestinal flora is common and often asymptomatic. Antimicrobials given commonly disrupt the intestinal microflora and through proliferation in colon and production of toxin A and B it precipitates C. difficile infection (CDI). The enterocytic detachment and bowel inflammation provoke C. difficile-associated diarrhoea (CDAD) sometimes developing into severe pseudomembranous colitis (PMC) and paralytic ileus. Infection is acquired from an endogenous source or from spores in the environment, most easily facilitated during hospital stay. In the elderly, comorbidity, hospitalization and antimicrobial treatment present as major risk factors and the slow recolonization of the normal flora likely responsible for single or multiple recurrences of CDI (25-50%) post therapy. The key procedure for diagnosis is toxin detection from stool specimens and sometimes in combination with culture to increase sensitivity. In mild cases stopping the offending antimicrobial will lead to resolution (25%) but standard therapy still consist of either oral metronidazole or vancomycin. Alternative agents are presently being developed and fidaxomicin, as well as nitrothiazolide are promising. Furthermore, host factors like low antitoxin A levels in serum relates to increased risk of recurrence and small numbers of patients have received immunoglobulin with good results. An immunogenic toxoid vaccine has been developed and human colostrum rich in specific secretory Ig A also support the future use of immunotherapy. Today we experience a tenfold increase of CDI incidence in the western world and both epidemics and therapeutic failure of metronidazole is contributing to morbidity and mortality. The current epidemic of the C. difficile strain NAP1/027 emerging in 2002 in Canada and the USA has now spread to most parts of Europe and virulence factors like high toxin production and sporulation challenge the therapeutic situation and cause great concern among infection control workers. Excessive use of modern fluoroquinolones is thought to play an important role in facilitating this epidemic since NAP1/027 was shown to have acquired moxifloxacin resistance compared to historical strains of the same genotype. Both the current epidemic like this and other local outbreaks from resistant or virulent strains warrant culture to be routinely performed enabling susceptibility testing and typing of the pathogen. Genotyping is most commonly done today by pulse-field gel electrophoresis (PFGE) or PCR ribotyping but multilocus variable-number tandem-repeat analysis (MLVA) seems promising. Epidemiological surveillance using all these tools will help us to better understand the global spread of C. difficile.

Antimicrobial resistance in Clostridium difficile

Clostridium difficile is the leading cause of hospital-acquired diarrhoea and the number of outbreaks has risen markedly since 2003. The emergence and spread of resistance in C. difficile is complicating treatment and prevention. Most isolates are still susceptible to vancomycin and metronidazole (MTZ), however transient and heteroresistance to MTZ have been reported. The prevalence of resistance to other antimicrobial agents is highly variable in different populations and in different countries, ranging from 0% to 100%. Isolates of common polymerase chain reaction (PCR) ribotypes are more resistant than uncommon ribotypes. Most of the resistance mechanisms that have been identified in C. difficile are similar to those in other Gram-positive bacteria, including mutation, selection and acquisition of the genetic information that encodes resistance. Better antibiotic stewardship and infection control are needed to prevent further spread of resistance in C. difficile.

Clostridium difficile infection in the intensive care unit

Clostridium difficile infection (CDI) is becoming more common worldwide. The morbidity and mortality associated with C difficile is also increasing at an alarming rate. Critically ill patients are at particularly high risk for CDI because of the prevalence of multiple risk factors in this patient population. Treatment of C difficile continues to be a difficult problem in patients with severe or recurrent disease. This article seeks to provide a broad understanding of CDI in the intensive care unit, with special emphasis on risk factor identification, treatment options, and disease prevention.