Epidemic Clostridium Difficile Strains Research Articles

Predominance of PCR-ribotypes, 018 (smz) and 369 (trf) of Clostridium difficile in Japan: a potential relationship with other global circulating strains?

Global spread and evolutionary links of an epidemic Clostridium difficile strain (PCR-ribotype 027) have been noted in recent decades. However, in Japan, no outbreaks caused by type 027 have been reported to date. A total of 120 C. difficile isolates from patients at 15 hospitals during non-outbreak seasons between 2011 and 2013 as well as 18 and 21 isolates collected from two hospitals in 2010 and 2009, respectively, in outbreak periods in Japan, were examined. Among these 120 isolates, Japan-ribotypes smz and ysmz (subtype variant of smz) were the most predominant (39.2 %) followed by Japan-ribotype trf (15.8 %). Types smz/ysmz and trf were also concurrently predominant at two hospitals in the outbreak settings. Out of the five binary toxin-positive isolates observed, only one was PCR-ribotype 027 and another PCR-ribotype 078. Type smz was later found to correspond to PCR-ribotype 018. High rates of resistance against gatifloxacin, moxifloxacin, erythromycin and clindamycin were observed in the PCR-ribotype 018 isolates. Interestingly, all trf isolates were toxin A-negative, toxin B-positive, but they did not correspond to PCR-ribotype 017, thus being assigned a new ribotype (PCR-ribotype 369). In conclusion, PCR-ribotypes 018 (smz) and 369 (trf) were identified as major circulating strains in both outbreak and non-outbreak settings in Japan. Given their epidemiological relevance, molecular investigations are warranted to clarify potential evolutionary links with related strains found elsewhere, such as PCR-ribotypes 018 and 017 from Europe and North America.

Epidemic Clostridium difficile strains demonstrate increased competitive fitness compared to nonepidemic isolates.

Clostridium difficile infection is the most common cause of severe cases of antibiotic-associated diarrhea (AAD) and is a significant health burden. Recent increases in the rate of C. difficile infection have paralleled the emergence of a specific phylogenetic clade of C. difficile strains (ribotype 027; North American pulsed-field electrophoresis 1 [NAP1]; restriction endonuclease analysis [REA] group BI). Initial reports indicated that ribotype 027 strains were associated with increased morbidity and mortality and might be hypervirulent. Although subsequent work has raised some doubt as to whether ribotype 027 strains are hypervirulent, the strains are considered epidemic isolates that have caused severe outbreaks across the globe. We hypothesized that one factor that could lead to the increased prevalence of ribotype 027 strains would be if these strains had increased competitive fitness compared to strains of other ribotypes. We developed a moderate-throughput in vitro model of C. difficile infection and used it to test competition between four ribotype 027 clinical isolates and clinical isolates of four other ribotypes (001, 002, 014, and 053). We found that ribotype 027 strains outcompeted the strains of other ribotypes. A similar competitive advantage was observed when two ribotype pairs were competed in a mouse model of C. difficile infection. Based upon these results, we conclude that one possible mechanism through which ribotype 027 strains have caused outbreaks worldwide is their increased ability to compete in the presence of a complex microbiota.

Importance of toxin A, toxin B, and CDT in virulence of an epidemic Clostridium difficile strain.

Clostridium difficile infection is the main cause of healthcare-acquired diarrhea in the developed world. In addition to the main virulence factors toxin A and B, epidemic, PCR Ribotype 027 strains, such as R20291, produce a third toxin, CDT. To develop effective medical countermeasures, it is important to understand the importance of each toxin. Accordingly, we created all possible combinations of isogenic toxin mutants of R20291 and assessed their virulence. We demonstrated that either toxin A or toxin B alone can cause fulminant disease in the hamster infection model and present tantalizing data that C. difficile toxin may also contribute to virulence.

Evaluation of antimicrobial activity of ceftaroline against Clostridium difficile and propensity to induce C. difficile infection in an in vitro human gut model

To examine the effects of exposure to ceftaroline or ceftriaxone on the epidemic Clostridium difficile strain PCR ribotype 027 and the indigenous gut microflora in an in vitro human gut model. Additionally, the MICs of ceftriaxone and ceftaroline for 60 C. difficile isolates were determined. Two triple-stage chemostat gut models were primed with human faeces and exposed to ceftaroline (10 mg/L, twice daily, 7 days) or ceftriaxone (150 mg/L, once daily, 7 days). Populations of indigenous gut microorganisms, C. difficile total viable counts, spore counts, cytotoxin titres and antimicrobial concentrations were monitored throughout. MICs were determined by a standard agar incorporation method. In the gut model, both ceftaroline and ceftriaxone induced C. difficile spore germination, proliferation and toxin production, although germination occurred 5 days later in the ceftaroline-exposed model. Toxin detection was sustained until the end of the experimental period in both models. No active antimicrobial was detected in vessel 3 of either model, although inhibitory effects on microflora populations were observed. Ceftaroline was ∼8-fold more active against C. difficile than ceftriaxone (geometric mean MICs, 3.38 versus 28.18 mg/L; MIC90s, 4 versus 64 mg/L; and MIC ranges, 0.125-16 versus 8-128 mg/L). Ceftaroline, like ceftriaxone, can induce simulated C. difficile infection in a human gut model. However, low in vivo gut concentrations of ceftaroline and increased activity against C. difficile in comparison with ceftriaxone mean that the true propensity of this novel cephalosporin to induce C. difficile infection remains unclear.

Decreased Cure and Increased Recurrence Rates for Clostridium difficile Infection Caused by the Epidemic C. difficile BI Strain

An epidemic strain of Clostridium difficile designated by restriction endonuclease analysis (REA) as group BI has caused multiple outbreaks of severe C. difficile infection (CDI). The treatment response of patients infected with this strain is uncertain. Clostridium difficile isolates were collected from 2 phase 3 clinical trials comparing fidaxomicin to vancomycin and typed using REA. Clinical cure and recurrence outcomes were analyzed by strain type of the infecting organism, BI and non-BI, using both univariate and multivariate analyses. From 999 patients, 719 isolates were available for typing (356 fidaxomicin treated and 363 vancomycin treated). BI was the most common REA group (34% of isolates). Patients infected with BI had lower cure rates (86.6%; 214 of 247) than those infected with non-BI strains (94.3%; 445 of 472) (P < .001). The cure rate difference between the BI and non-BI patients was significant for both vancomycin (P = .02) and fidaxomicin (P = .007). BI patients had a recurrence rate of 27.4% (51 of 186), compared with a recurrence rate of 16.6% (66 of 397) in non-BI patients (P = .002). By multivariate analysis, BI infection was statistically significant as a risk factor for reduced cure (odds ratio [OR], 0.48; 95% confidence interval [CI], .27-.85; P = .030) and for increased recurrence (OR, 1.57; 95% CI, 1.01-2.45; P = .046). The clinical cure rate of patients infected with the epidemic BI C. difficile strain is lower than the cure rate of those infected with non-BI strains whether treated with fidaxomicin or vancomycin. Similarly, the CDI recurrence rate is increased in patients with the BI strain compared with patients with other C. difficile strains.

Current strategies for management of initial Clostridium difficile infection

In the past decade, an epidemic strain of Clostridium difficile has led to increased incidence and severity of nosocomial C. difficile infections (CDI). Responsiveness to standard antimicrobial care for this strain is declining, and the morbidity and mortality of CDI and recurrent CDI are rising. Effective management requires a coordinated effort among all members of the healthcare team to facilitate early identification of patients at risk for CDI, early recognition of disease onset and confirmatory testing, prompt initiation of the most appropriate management approach, and ongoing monitoring throughout the continuum of care. Hospitalists, as coordinators of patient care, are in an ideal position to ensure that patients receive prompt and optimal treatment based on current clinical evidence and severity of the disease.

First Australian isolation of epidemic Clostridium difficile PCR ribotype 027

We report the first isolation in Australia of a hypervirulent epidemic strain of Clostridium difficile, PCR ribotype 027. It was isolated from a 43-year-old woman with a permanent ileostomy, who appears to have been infected while travelling in the United States. The isolate was positive for toxin A, toxin B and binary toxin, and resistant to fluoroquinolone antimicrobials, and had characteristic deletions in the tcdC gene. All diagnostic laboratories and health care facilities in Australia should now be on high alert for this organism.

Activity of vancomycin against epidemic Clostridium difficile strains in a human gut model

Vancomycin and metronidazole remain the only primary options for the treatment of Clostridium difficile infection (CDI). Recent reports have suggested a superior clinical response to vancomycin therapy compared with metronidazole, but this has been difficult to prove or explain. There are few robust in vitro data of the effects of antibiotic treatment of CDI in a gut reflective setting. We used clindamycin to induce high-level toxin production by two epidemic C. difficile PCR ribotypes in a human gut model of CDI. Vancomycin was instilled into the models to achieve in vivo faecal concentrations. C. difficile populations and toxin titres, and gut bacterial populations and vancomycin levels were monitored before, during and after vancomycin instillation. Clindamycin treatment elicited C. difficile germination and high-level cytotoxin production. Vancomycin reduced total viable counts and cytotoxin titres of both C. difficile PCR ribotypes, with no evidence of recurrence before the model runs were ended. C. difficile PCR ribotype 027 populations exhibited greater germination capacity than did PCR ribotype 106. Vancomycin was more rapidly effective against the greater numbers of PCR ribotype 027 vegetative forms. Vancomycin showed no activity against C. difficile spores. Bacteriological response to vancomycin varies between strains causing CDI, possibly correlating with the extent of germination capacity. Vancomycin effectively reduced vegetative forms and cytotoxin titres of both of the epidemic C. difficile PCR ribotypes evaluated, but showed no anti-spore activity. Comparison with the results of a previous gut model study showed that vancomycin was more effective than metronidazole in reducing C. difficile PCR ribotype 027 numbers and cytotoxin titres.

Typing Clostridium difficile strains based on tandem repeat sequences

BackgroundGenotyping of epidemic Clostridium difficile strains is necessary to track their emergence and spread. Portability of genotyping data is desirable to facilitate inter-laboratory comparisons and epidemiological studies.ResultsThis report presents results from a systematic screen for variation in repetitive DNA in the genome of C. difficile. We describe two tandem repeat loci, designated 'TR6' and 'TR10', which display extensive sequence variation that may be useful for sequence-based strain typing. Based on an investigation of 154 C. difficile isolates comprising 75 ribotypes, tandem repeat sequencing demonstrated excellent concordance with widely used PCR ribotyping and equal discriminatory power. Moreover, tandem repeat sequences enabled the reconstruction of the isolates' largely clonal population structure and evolutionary history.ConclusionWe conclude that sequence analysis of the two repetitive loci introduced here may be highly useful for routine typing of C. difficile. Tandem repeat sequence typing resolves phylogenetic diversity to a level equivalent to PCR ribotypes. DNA sequences may be stored in databases accessible over the internet, obviating the need for the exchange of reference strains.

Clostridium difficile–associated diarrhea: an emerging threat to pregnant women

To estimate if Clostridium difficile-associated disease (CDAD) is increasing in peripartum women. Peripartum CDAD was assessed through 1) passive surveillance collecting clinical and pathology data on severe cases and 2) survey among infectious disease consultants (ICDs) in the Emerging Infections Network. Ten severe cases were collected; most had associated antibiotic use. Seven women were either admitted to the ICU or underwent colectomy. Three infants were stillborn, and 3 women died. The epidemic Clostridium difficile strain was found in 2 cases. Among 798 ICDs, 419 (52%) participated in the survey. Thirty-seven respondents (9%) recalled 55 cases, mostly in the postpartum period with 21 complications, mainly due to relapse. Severe CDAD may be increasing in peripartum women. Clinicians should have a low threshold for testing, be aware of the potential for severe outcomes, and take steps to reduce both the risk of disease and resultant complications.

P795 Tolevamer, a novel toxin-binding polymer, neutralises the large clostridial toxins from the B1/027 epidemic strain of Clostridium difficile

P795 Tolevamer, a novel toxin-binding polymer, neutralises the large clostridial toxins from the B1/027 epidemic strain of Clostridium difficile

P1056 Emergence of a new epidemic Clostridium difficile strain (ribotype 017) resistant to newer fluoroquinolones in Poland

P1056 Emergence of a new epidemic Clostridium difficile strain (ribotype 017) resistant to newer fluoroquinolones in Poland

A Hospital Outbreak of Diarrhea Due to an Emerging Epidemic Strain of Clostridium difficile

Increased Clostridium difficile-associated disease (CDAD) in a hospital and an affiliated long-term care facility continued despite infection control measures. We investigated this outbreak to determine risk factors and transmission settings. The CDAD cases were compared according to where the disease was likely acquired based on health care exposure and characterization of isolates from case patients, asymptomatic carriers, and the environment. Antimicrobial susceptibility testing, strain typing using pulsed-field gel electrophoresis, and toxinotyping were performed, and toxins A and B, binary toxin, and deletions in the tcdC gene were detected using polymerase chain reaction. Risk factors were examined in a case-control study, and overall antimicrobial use was compared at the hospital before and during the outbreak. Significant increases were observed in hospital-acquired (0.19 vs 0.86; P < .001) and long-term care facility-acquired (0.04 vs 0.31; P = .004) CDAD cases per 100 admissions as a result of transmission of a toxinotype III strain at the hospital and a toxinotype 0 strain at the long-term care facility. The toxinotype III strain was positive for binary toxin, an 18-base pair deletion in tcdC, and increased resistance to fluoroquinolones. Independent risk factors for CDAD included use of fluoroquinolones (odds ratio [OR], 3.22; P = .04), cephalosporins (OR, 5.19; P = .006), and proton pump inhibitors (OR, 5.02; P = .02). A significant increase in fluoroquinolone use at the hospital took place during the outbreak (185.5 defined daily doses per 1000 patient-days vs 200.9 defined daily doses per 1000 patient-days; P < .001). The hospital outbreak of CDAD was caused by transmission of a more virulent, fluoroquinolone-resistant strain of C difficile. More selective fluoroquinolone and proton pump inhibitor use may be important in controlling and preventing such outbreaks.

Tigecycline does not induce proliferation or cytotoxin production by epidemic Clostridium difficile strains in a human gut model

Data on the risk of Clostridium difficile infection (CDI) associated with specific antibiotics are difficult to obtain because of confounding clinical factors. It is particularly important to evaluate the propensity of new antibiotics to induce CDI. We have examined the propensity of tigecycline to induce CDI using a human gut model. We used a three-stage chemostat human gut model to study the effects of tigecycline on indigenous gut microflora and C. difficile. Two epidemic C. difficile were studied in separate experiments: PCR ribotype 001 (UK, CD001) and PCR ribotype 027 (North America, CD027). Tigecycline MICs for 39 C. difficile representing 19 distinct PCR ribotypes were also determined. Tigecycline MICs were 0.06 mg/L for all the C. difficile strains. Peak tigecycline concentrations in the gut model were 10.9 and 11.7 mg/L in CD027 and CD001 experiments, respectively. Tigecycline instillation invoked marked decreases in numbers of bacteroides and bifidobacteria (10(7)-10(8) cfu/mL) and lesser reductions in facultative anaerobes. Despite markedly altered gut microflora, CD001 and CD027 remained as spores for the duration of the experiment, with no evidence of proliferation or cytotoxin production. Tigecycline exposure did not induce C. difficile proliferation or cytotoxin production despite reduced competing microflora. The potency of tigecycline against C. difficile may contribute to the low risk of CDI induction. Factors other than gut microflora colonization resistance may be important in preventing C. difficile spore germination, proliferation and cytotoxin production.

A modified pulsed-field gel electrophoresis (PFGE) protocol for subtyping previously non-PFGE typeable isolates of Clostridium difficile polymerase chain reaction ribotype 001

A modified pulsed-field gel electrophoresis (PFGE) protocol was developed and applied to 50 isolates of the UK epidemic strain of Clostridium difficile, polymerase chain reaction (PCR) ribotype 001, to develop a PFGE-based subtyping scheme. This protocol overcame the inherent DNA degradation problems associated with typing this strain of C. difficile by this method, and whole genomic digestion with SmaI restriction enzyme yielded seven distinct and reproducible PFGE banding patterns. Modified PFGE is an appropriate method for subtyping C. difficile PCR ribotype 001 that could be used to improve epidemiological investigations.

Evidence to support the existence of subgroups within the UK epidemic Clostridium difficile strain (PCR ribotype 1)

We used three different DNA fingerprinting techniques and clindamycin susceptibility testing to confirm that Clostridium difficile PCR ribotype I isolates can be divided into two subclones. This observation may permit a better understanding of the epidemiology and pathogenicity of C. difficile infection.

Nosocomial diarrhoea

Toroviruses have been reported as a new cause of nosocomial viral diarrhoea, and the role of astroviruses has been further elucidated. Polymerase chain reaction methods promise to improve the diagnosis and understanding of the aetiology and control of hospital-acquired viral gastroenteritis. A clearer picture of the impact and extent of Clostridium difficile diarrhoea has emerged, and several control measures have been described. An epidemic Clostridium difficile strain and toxin A-deficient strains have been reported. There is growing evidence that enterotoxin-producing Clostridium perfringens can also cause antibiotic-associated diarrhoea.