Antimicrobial Susceptibility of Clostridium difficile from Different Sources

A total of 79 Clostridium difficile strains from healthy young and elderly adults, elderly patients without gastrointestinal disease, elderly patients receiving antibiotics without gastrointestinal complications, and elderly patients with antibiotic-associated diarrhea or pseudomembranous colitis were tested for their susceptibilities to 24 antimicrobial agents. All of the 79 strains were inhibited by low concentrations of rifampicin, metronidazole, fusidic acid, vancomycin, ampicillin, and penicillin G. The strains were highly resistant to aminoglycosides, trimethoprim, sulfamethoxazole, nalidixic acid, and cycloserine and often resistant to neomycin, cefoxitin, and cefalexin. Wide variations in the susceptibility of C. difficile strains to erythromycin, clindamycin, lincomycin, chloramphenicol, and tetracycline were found. Strains resistant to erythromycin, clindamycin, and lincomycin were more frequently found among strains isolated from elderly adults than those isolated from young adults, with particularly high frequency among strains isolated from elderly patients receiving antibiotics. None of the 23 strains isolated from healthy young adults was resistant to chloramphenicol. All of the 14 strains resistant to erythromycin, clindamycin, lincomycin, and chloramphenicol were sensitive to tetracycline and all of the 15 strains resistant to erythromycin, clindamycin, lincomycin, and tetracycline were sensitive to chloramphenicol. Only one out of 19 tetracycline-resistant strains was highly toxigenic, whereas 42 (70%) of 60 sensitive strains were highly toxigenic.     

Characterization of Clostridium difficile strains isolated from immunosuppressed inpatients in a hospital in Rio de Janeiro,Brazil

The aim of this work was to identify and characterize Clostridium difficile strains from fecal and hospital environmental samples. C. difficile toxins were detected by ELISA in 28.5% of the analyzed samples. Four strains were isolated from immunosuppresssed inpatients presenting antibiotic-associated diarrhea. All strains possessed tcdA and tcdB genes and did not present neither the cdtA and cdtB genes nor any significant deletions in the tcdC gene. PFGE and PCR-ribotyping analysis showed that two strains belonged to the same clonal type (ribotype 014) and the other two were grouped into ribotype 106, in spite of presenting a similar, but not identical genetic fingerprint. This report shows that for the first time ribotype 106 was found outside the United Kingdom. All isolates were equally sensitive to metronidazole. The ribotype 014 isolates were highly resistant to clindamycin, while the ribotype 106 isolates were resistant to all fluoroquinolones tested. This work reveals the spread of C. difficile in the hospital unit studied and the presence of three genetically related types, two of them presenting resistance to fluoroquinolones.     

Detection of cross-infection associated to a Brazilian PCR-ribotype of <Emphasis Type="Italic">Clostridium difficile</Emphasis> in a university hospital in Rio de Janeiro,Brazil

Clostridium difficile is an important nosocomial enteric pathogen and is the etiological agent of pseudomembranous colites. Recently, the rates of C. difficile infection (CDI) have increased worldwide, but in Brazil few data about this situation and the incidence of clonal types of C. difficile exist. This study aimed to isolate and characterize C. difficile strains from samples obtained of a university hospital (HUCFF) in Rio de Janeiro city, Brazil. CDI was identified by ELISA in 27.1% of HUCFF-in-patients enrolled in the study, and the bacterium was recovered from eight of these fecal samples. All strains, except one, presented tcdA and tcdB genes and presented neither the cdtA and cdtB genes nor any significant deletions in the tcdC gene. All strains were sensitive to metronidazole, vancomycin and moxifloxacin, and resistant to clindamycin, ciprofloxacin and levofloxacin. PCR-ribotyping and PFGE revealed four different clonal types among the isolates. The Brazilian PCR-ribotype 133 accounted for 50% of strains isolated, and PCR-ribotype 233 strains were obtained from 25% of the in-patients. The prevalence and resurgence of the Brazilian PCR-ribotype 133 among the hospitalized patients of HUCFF was established, and cross-infection of different patients associated to the same PCR-ribotypes was detected. Our results emphasize the importance of the diagnosis and control of CDI in order to prevent the emergence of specific clones that can lead to C. difficile-associated outbreaks in Brazilian hospitals.     

Sensitivity to antibiotics of Clostridium difficile toxigenic nosocomial strains

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

Molecular characterization and antimicrobial susceptibilities of extra-intestinal Clostridium difficile isolates

Amongst 25 extra-intestinal clinical isolates of Clostridium difficile, A(+)B(+) (72%) and A(-)B(+) (4%) toxigenic phenotypes, as well as the non-toxigenic phenotype (A(-)B(-)) (24%), were identified. The A(-)B(-) isolates did not express toxin, yet carried part of the tcdA and tcdB gene and are of a previously unreported toxinotype. Six A(+)B(+) isolates also carried binary toxin genes. Resistance to erythromycin (20%), clindamycin (48%), tetracycline (16%), moxifloxacin (16%) and imipenem (11%) occurred but with no apparent correlation to phenotype. None of the strains was resistant to vancomycin or metronidazole. Imipenem-resistance decreased by EDTA, but susceptibility to meropenem suggests the presence of an imipenem specific metalloenzyme.     

Survey of susceptibility of clinical Clostridium diffiicile strains isolated from patients hospitalised in different departments of paediatric hospital to antimicrobial agents

This study was performed to determine the susceptibility of 50 C. difficile strains isolated from faecal samples of children suspected to antibiotic associated diarrhea (AAD) to antimicrobial agents: metronidazole, vancomycin, erythromycin, clindamycin, ciprofloxacin, moxifloksacin, gatifloksacin and imipenem. The all C. difficile strains were sensitived to metronidazole and vancomycin. Twenty six per cent of strains were resistant to erythromycin and clindamycin (MLS(B) type resistance). Resitance to ciprofloxacin, moxifloxacin, gatifloxacin and imipenem was detected in 98%, 8%, 8% and 30% of C. difficile strains, respectively.     

Molecular typing and antimicrobial susceptibility testing to six antimicrobials of <Emphasis Type="Italic">Clostridium difficile</Emphasis> isolates from three Czech hospitals in Eastern Bohemia in 2011–2012

In 2011–2012, a survey was performed in three regional hospitals in the Czech Republic to determine the incidence of Clostridium difficile infections (CDIs) and to characterize bacterial isolates. C. difficile isolates were characterized by PCR ribotyping, toxin genes detection, multiple-locus variable-number tandem-repeat analysis (MLVA), and antimicrobial susceptibility testing to fidaxomicin, vancomycin, metronidazole, clindamycin, LFF571, and moxifloxacin using agar dilution method. The incidence of CDI in three studied hospitals was 145, 146, and 24 cases per 100,000 inhabitants in 2011 and 177, 258, and 67 cases per 100,000 inhabitants in 2012. A total of 64 isolates of C. difficile was available for molecular typing and antimicrobial susceptibility testing. 60.9% of the isolates were classified as ribotype 176. All 41 isolates of ribotypes 176 and 078 were positive for the presence of binary toxin genes. Ribotype 176 also carried 18-bp deletion in the regulatory gene tcdC. Tested isolates of C. difficile were fully susceptible to vancomycin and metronidazole, whereas 65.1% of the isolates were resistant to moxifloxacin. MLVA results indicated that isolates from three different hospitals were genetically related, suggesting transmission between healthcare facilities.     

New PCR ribotypes of Clostridium difficile detected in children in Brazil

A total of 35 Brazilian isolates of Clostridium difficile from faecal stools and four isolates from hospital environments were analyzed by PCR ribotyping. A whole cell protein profile (as an alternative for serogrouping), in vitro toxin production and susceptibility to vancomycin, metronidazole and clindamycin were also investigated. All strains were typeable by both phenotypic and genotypic methods, and a total of 13 different PCR ribotypes were identified, of which seven (132, 133, 134, 135, 136, 142 and 143) were considered new types and accounted for 78.5% of all samples evaluated (including hospital environments). A non-toxigenic C. difficile PCR ribotype 133 was detected in all children groups examined (inpatients, outpatients and healthy children), whilst toxigenic PCR ribotypes 015, 131, 134 and 135 were associated mostly with symptomatic children. Serogroups G and D were disseminated both in patients from the community and from the pediatric hospital, with group G prevalent among outpatient children. All strains were susceptible to vancomycin and metronidazole but high levels of resistance to clindamycin were found, especially among serogroups G and D. Co-existence of different ribotypes and serogroups in the same individual was observed. The new seven ribotypes found in this investigation may represent strains characteristic of this region of Brazil.     

Genetically related Clostridium difficile from water sources and human CDI cases revealed by whole-genome sequencing

Clostridium difficile isolates from the environment are closely related to those from humans, indicating a possible environmental transmission route for C. difficile infection (CDI). In this study, C. difficile was isolated from 47.3% (53/112) of lake/pond, 23.0% (14/61) of river, 20.0% (3/15) of estuary and 0.0% (0/89) of seawater samples. The most common toxigenic strain isolated was C. difficile PCR ribotype (RT) 014/020 (10.5%, 8/76). All water isolates were susceptible to fidaxomicin, metronidazole, rifaximin, amoxicillin/clavulanic acid, moxifloxacin and tetracycline. Resistance to vancomycin, clindamycin, erythromycin and meropenem was detected in 5.3% (4/76), 26.3% (20/76), 1.3% (1/76) and 6.6% (5/76) of isolates, respectively. High-resolution core-genome analysis was performed on RT 014/020 isolates of water origin and 26 clinical RT 014/020 isolates from the same year and geographical location. Notably, both human and water strains were intermixed across three sequence types (STs), 2, 13 and 49. Six closely related groups with ≤10 core-genome single nucleotide polymorphisms were identified, five of which comprised human and water strains. Overall, 19.2% (5/26) of human strains shared a recent genomic relationship with one or more water strains. This study supports the growing hypothesis that environmental contamination by C. difficile plays a role in CDI transmission.     

Molecular epidemiology of Clostridium difficile strains from nosocomial-acquired infections

The purpose of this study is to analyze isolates of Clostridium difficile from patients with nosocomial acquired infection in respect to their molecular type and antimicrobial susceptibility. Fifty-nine randomly selected clinical isolates were characterized. Molecular typing was performed by rep-PCR (DiversiLab). Isolates were tested by disk diffusion towards 11 different antibiotics. All isolates were susceptible to metronidazole and vancomycin. Fifty five (93 %) isolates were resistant to erythromycin and fifty six (95 %) exhibited resistance to both clindamycin and moxifloxacin. Twenty rep-PCR types were identified, but most clinical isolates formed four major rep-PCR clusters (A₁ 24/59, 40 %; A₂ 20/59, 33 %; A₃ 5/59, 8 %; A₄ 3/59, 5 %). These results show high genetic variability, which demonstrate clearly the complexity of the strains of C. difficile and also show an increasing rate of resistance to fluoroquinolones in our region emphasizing the importance of implementing surveillance programs in order to prevent further spread of resistance in C. difficile.     

Clostridium difficile in emergency room

Clostridium difficile strains are known as etiological agents of pseudomembranous colitis (PMC), antibiotic-associated diarrhea (AAC) and colitis (AAC) and hospital-acquired infections. The aim of this study was to determine the frequency of C. difficile infection among patients in the emergency room and to compare isolated strains by phenotypic and genotypic characteristics. During a period of 11 months, 56 stool samples taken from diarrheic patients hospitalized in the emergency room of the Medical Center UC Davis and 14 environmental samples were cultured for isolation of C. difficile strains. Eighteen C. difficile strains were isolated from stool samples cultured on selective TCCCA plates and 5 strains from environmental samples using Rodac plates. Eleven toxigenic (TcdA+/TcdB+), 6 non-toxigenic (TcdA-/TcdB-) and unique toxin A-negative/toxin B-positive (TcdA-/TcdB+) C. difficile strains were detected among patients' isolates and 3 toxigenic and 2 non-toxigenic strains-among environmental samples. The majority of C. difficile-positive patients were treated previously by antibiotics. Four strains isolated from patients' fecal samples and one strain isolated from the environment demonstrated high-level resistance to erythromycin and clindamycin (MIC >256mug/mL). The results obtained by AP-PCR and PCR-ribotyping revealed genetic heterogeneity among the strains isolated from patients' fecal samples. However, similarity was observed among environmental strains and strains isolated from patients' fecal samples. Considering the importance of emergency room patients as a potential source of C. difficile strains, it appears to be important examine these patients for C. difficile before transfer to the other hospital units.     

High diversity of Clostridium difficile genotypes isolated from a single poultry farm producing replacement laying hens

Clostridium difficile is well established as a pathogen of horses, calves, and pigs, but little is known about its prevalence in poultry. In this study, chicken fecal samples were collected on four occasions from two populations being raised as layer replacements. Samples were examined by an enrichment culture method, and 38 of 61 (62.3%) were culture positive. The rate of colonization seemed to be age dependent: 100% of fecal samples from 2-week- old birds were culture positive, and the colonization rate decreased to 71.4% in 14-week- old birds, and to 40.9% in 18-week- old birds. Unlike in other domestic animal hosts, the diversity of PCR ribotypes found on a single farm was high, and 44 isolated strains belonged to 12 PCR ribotypes. Furthermore, the prevalence of variant strains having changed toxin genes for toxins A and B and possessing an additional toxin, binary toxin, was low. The majority of strains were toxinotype 0, although two were nontoxinogenic and three were binary toxin-positive toxinotype IV. Toxinotype V strains, which are often associated with food animals, were not found.     

Molecular Epidemiology of Clostridium difficile Infection in a Large Teaching Hospital in Thailand

Clostridium difficile infection (CDI) is a leading cause of healthcare-associated morbidity and mortality worldwide. In Thailand, CDI exhibits low recurrence and mortality and its molecular epidemiology is unknown. CDI surveillance was conducted in a tertiary facility (Siriraj Hospital, Bangkok). A total of 53 toxigenic C. difficile strains from Thai patients were analyzed by multi-locus sequence typing (MLST), PCR ribotyping, and pulse-field gel electrophoresis (PFGE). The mean age of the cohort was 64 years and 62.3% were female; 37.7% of patients were exposed to > two antibiotics prior to a diagnosis of CDI, with beta-lactams the most commonly used drug (56.3%). Metronidazole was used most commonly (77.5%; success rate 83.9%), and non-responders were treated with vancomycin (success rate 100%). None of the isolates carried binary toxin genes. Most isolates (98.2–100%) were susceptible to metronidazole, vancomycin, tigecycline and daptomycin. There were 11 sequence types (STs), 13 ribotypes (RTs) and four PFGE types. Six previously identified STs (ST12, ST13, ST14, ST33, ST41 and ST45) and five novel STs unique to Thailand (ST66, ST67, ST68, ST69 and ST70) were identified. PCR RTs UK 017 (ST45) (45.3%) and UK 014/020 (ST33) (24.5%) were the most common. High concordance was observed between the MLST and ribotyping results (p<0.001). C. difficile isolates from Thai patients were highly susceptible to standard antimicrobial agents. In conclusion, the five STs indicate the high genetic diversity and unique polymorphisms in Thailand. Moreover, the emergence of antimicrobial resistance to vancomycin warranted continuous surveillance to prevent further spread of the toxigenic C. difficile isolates.     

Different Antibiotic Resistance and Sporulation Properties within Multiclonal Clostridium difficile PCR Ribotypes 078, 126, and 033 in a Single Calf Farm

Clostridium difficile strains were sampled periodically from 50 animals at a single veal calf farm over a period of 6 months. At arrival, 10% of animals were C. difficile positive, and the peak incidence was determined to occur at the age of 18 days (16%). The prevalence then decreased, and at slaughter, C. difficile could not be isolated. Six different PCR ribotypes were detected, and strains within a single PCR ribotype could be differentiated further by pulsed-field gel electrophoresis (PFGE). The PCR ribotype diversity was high up to the animal age of 18 days, but at later sampling points, PCR ribotype 078 and the highly related PCR ribotype 126 predominated. Resistance to tetracycline, doxycycline, and erythromycin was detected, while all strains were susceptible to amoxicillin and metronidazole. Multiple variations of the resistance gene tet(M) were present at the same sampling point, and these changed over time. We have shown that PCR ribotypes often associated with cattle (ribotypes 078, 126, and 033) were not clonal but differed in PFGE type, sporulation properties, antibiotic sensitivities, and tetracycline resistance determinants, suggesting that multiple strains of the same PCR ribotype infected the calves and that calves were likely to be infected prior to arrival at the farm. Importantly, strains isolated at later time points were more likely to be resistant to tetracycline and erythromycin and showed higher early sporulation efficiencies in vitro, suggesting that these two properties converge to promote the persistence of C. difficile in the environment or in hosts.     

An in vitro culture model to study the dynamics of colonic microbiota in Syrian golden hamsters and their susceptibility to infection with Clostridium difficile

Clostridium difficile infections (CDI) are caused by colonization and growth of toxigenic strains of C. difficile in individuals whose intestinal microbiota has been perturbed, in most cases following antimicrobial therapy. Determination of the protective commensal gut community members could inform the development of treatments for CDI. Here, we utilized the lethal enterocolitis model in Syrian golden hamsters to analyze the microbiota disruption and recovery along a 20-day period following a single dose of clindamycin on day 0, inducing in vivo susceptibility to C. difficile infection. To determine susceptibility in vitro, spores of strain VPI 10463 were cultured with and without soluble hamster fecal filtrates and growth was quantified by quantitative PCR and toxin immunoassay. Fecal microbial population changes over time were tracked by 16S ribosomal RNA gene analysis via V4 sequencing and the PhyloChip assay. C. difficile culture growth and toxin production were inhibited by the presence of fecal extracts from untreated hamsters but not extracts collected 5 days post-administration of clindamycin. In vitro inhibition was re-established by day 15, which correlated with resistance of animals to lethal challenge. A substantial fecal microbiota shift in hamsters treated with antibiotics was observed, marked by significant changes across multiple phyla including Bacteroidetes and Proteobacteria. An incomplete return towards the baseline microbiome occurred by day 15 correlating with the inhibition of C. difficile growth in vitro and in vivo. These data suggest that soluble factors produced by the gut microbiota may be responsible for the suppression of C. difficile growth and toxin production.     

Case-Control Study on the Role of Enterotoxigenic Bacteroides fragilis as a Cause of Diarrhea among Children in Kolkata,India

A total of 874 fecal specimens (446 diarrheal cases and 428 controls) from diarrheal children admitted in the Infectious Diseases Hospital, Kolkata and age and sex matched asymptomatic subjects from an urban community were assessed for the prevalence of enterotoxigenic Bacteroides fragilis (ETBF). Isolates of B. fragilis were tested for the presence of enterotoxin gene (bft) by PCR. The detection rate of ETBF was 7.2% (63 of 874 specimens) that prevailed equally in diarrheal cases and controls (7.2% each; 32 of 446 cases and 31 of 428 controls). Male children up to one year age group was significantly (p<0.05) associated with ETBF infection as compared to children > 2 years of age in cases and controls. In 25 ETBF isolates, the bft gene was genotyped using PCR-RFLP and only two alleles were identified with prevalence rate of 40% and 60% for bft-1 and bft-3, respectively. All the ETBF isolates were susceptible for chloramphenicol and imipenem but resistant to clindamycin (48%), moxifloxacin (44%) and metronidazole (32%). Resistance of ETBF to moxifloxacin (44%) and metronidazole is an emerging trend. Pulsed-field gel electrophoresis (PFGE) revealed that majority of the ETBF isolates are genetically diverse. In the dendrogram analysis, two clusters were identified, one with ETBF resistant to 5–8 antimicrobials and the other cluster with metronidazole and moxifloxacin susceptible isolates from diarrheal cases. To our knowledge, this is the first detailed report on ETBF from India indicating its clinical importance and molecular characteristics.     

Are Rapid Immunoassays for in vivo Detection of Toxin A Sufficient for Diagnostic Purposes of Clostridium difficile -Associated Diseases?

One hundred and fifty-five stool specimens of patients suspected for Clostridium difficile -associated diarrhoea, colitis or pseudomembranous colitis (PMC) were investigated. All patients were pre-treated with antibiotics, suffered from watery diarrhoea and abdominal pain and were hospitalized in different hospital units. Units varied from departments of surgery, internal medicine, intensive care, paediatry, dermatology, orthopaedy to gastroenterology. Fifty C. difficile strains were isolated from the faecal samples. Clostridium difficile toxin detection was done directly in the stool samples, and also in cultured C. difficile strains (in vivo and in vitro, respectively). We observed clear differences between in vivo and in vitro toxin A detection by using commercial rapid immuno-enzymatic tests: from 25 in vivo toxin A-negative samples, 17 were positive in vitro. This observation suggests that culturing of C. difficile on selective medium is mandatory for adequate toxin detection and necessary for confirming the presence of toxin-producing C. difficile. This is especially important among patients with clinical symptoms and history of pretreatment with antibiotics and when in vivo toxin A detection is negative. It was established that toxin gene detection by PCR is optimal and PCR results were concordant with results of other in vitro assays. Genotyping by using AP-PCR and PCR ribotyping showed heterogeneity among the toxigenic C. difficile strains cultured from in vivo toxin A-negative stool samples.     

Surveillance and trends of antimicrobial resistance among clinical isolates of anaerobes in Kuwait hospitals from 2002 to 2007

The susceptibility trends for all anaerobes processed by the Anaerobe Reference Laboratory against various antibiotics were determined by using data for 2557 isolates referred by all government hospitals in Kuwait from 2002 to 2007. MIC were determined for the following anti-anaerobic antibiotics: amoxicillin–clavulanic acid, clindamycin, imipenem, meropenem, metronidazole, penicillin, piperacillin, piperacillin–tazobactam and vancomycin (for Gram-positive anaerobes only), using E-test method. The commonest isolates were Bacteroides fragilis (36.8%), followed by Peptostreptococcus spp. (21.9%), Bacteroides ovatus (15.5%) and Prevotella bivia (12.1%). In addition, Prevotella oralis and other Bacteroides spp. represented 8.5% and 8.1% of total number of isolates, respectively. Resistance rate varied among the antimicrobial agents and the species tested. The β-lactams, with the exception of penicillin, were the most active drugs. Piperacillin–tazobactam was the only antimicrobial agent to which all the isolates were uniformly susceptible. Imipenem and metronidazole were highly active with resistance rate of only <5% recorded against most isolates. However, 42.8, 55.8 and 9.3% of Clostridium difficile isolates were resistant to imipenem, clindamycin and meropenem, respectively. It is noteworthy that from 2002 to 2007, there was a gradual increase in resistance rates to clindamycin, amoxicillin–clavulanic acid and piperacillin among B. fragilis. Periodic surveillance of antibiotic resistance among the anaerobic bacteria is recommended as a guide to empiric antibiotic use and formulation of guideline for appropriate choice of antimicrobial therapy in anaerobic infections.     

Trends in antibiotic resistance in Prevotella species from patients of the University Hospital of Maxillofacial Surgery,Sofia, Bulgaria,in 2003–2009

Head-and-neck infections often involve anaerobes such as Prevotella species. Aim of the present study was to assess the evolution and the factors associated with resistance in Prevotella species to penicillin, clindamycin, metronidazole, tetracycline and β-lactams/β-lactamase inhibitors (BL/BLIs). In total, 192 Prevotella strains, isolated from patients with oral and head-and-neck infections, were evaluated. Common isolates were Prevotella intermedia and Prevotella melaninogenica within the pigmented species as well as Prevotella oris and Prevotella oralis group within the non-pigmented species. Overall resistance was 43.2% for penicillin, 10.9% for clindamycin, 0% for metronidazole. Nonsusceptibility to tetracycline was 29.1% without significant differences in resistance rates between pigmented and other species. Penicillin resistant strains were β-lactamase positive. From 2003–2004 to 2007–2009, penicillin resistance rates increased about four-fold (from 15.4% to 60.6%). Clindamycin resistance did not show evolution, whereas tetracycline nonsusceptibility decreased from 43.3% in 2003–2004 to 20.7% in 2007–2009. Except for one (0.5%) P. oralis strain with intermediate susceptibility to BL/BLIs, the other strains were susceptible to the agents. In conclusion, in Prevotella strains from patients with head-and-neck infections, the resistance rate to penicillin increased, that to clindamycin remained stable and the nonsusceptibility rate to tetracycline decreased during the period. Activity against >99% of Prevotella strains was observed with metronidazole and BL/BLIs. The penicillin resistance and tetracycline nonsusceptibility were associated with the year of study, national antibiotic consumption and possibly with previous treatment (for tetracycline). The evolution of penicillin resistance in Prevotella strains was highly dynamic.     

Molecular Characterization of Clostridium difficile Isolates from Human Subjects and the Environment

Clostridium difficile is a spore-forming, gram-positive, anaerobic bacillus that can cause C. difficile infection (CDI). However, only a few studies on the prevalence and antibiotic resistance of C. difficile in healthy individuals in China have been reported. We employed a spore enrichment culture to screen for C. difficile in the stool samples of 3699 healthy Chinese individuals who were divided into 4 groups: infants younger than 2 years of age and living at home with their parents; children aged 1 to 8 years of age and attending three different kindergarten schools; community-dwelling healthy adult aged 23–60 years old; and healthcare workers aged 28–80 years old. The C. difficile isolates were analyzed for the presence of toxin genes and typed by PCR ribotyping and multilocus sequence typing (MLST). The minimum inhibitory concentration of 8 antimicrobial agents was determined for all of the isolates using the agar dilution method. The intestinal carriage rate in the healthy children was 13.6% and ranged from 0% to 21% depending on age. The carriage rates in the 1654 community-dwelling healthy adults and 348 healthcare workers were 5.5% and 6.3%, respectively. Among the isolates, 226 were toxigenic (225 tcdA+/tcdB+ and 1 tcdA+/tcdB+ ctdA+/ctdB+). Twenty-four ribotypes were found, with the dominant type accounting for 29.7% of the isolates. The toxigenic isolates were typed into 27 MLST genotypes. All of the strains were susceptible to vancomycin, metronidazole, fidaxomicin, and rifaximin. High resistance to levofloxacin and ciprofloxacin at rates of 39.8% and 98.3%, respectively, were observed. ST37 isolates were more resistant to levofloxacin than the other STs. The PCR ribotypes and sequence types from the healthy populations were similar to those from the adult patients.