Geographic patterns of antimicrobial susceptibilities for Bacteroides spp. worldwide: Results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2007-2020.

Antimicrobial susceptibilities of 4973 Bacteroides spp. isolates recovered from various sources of patients from 12 countries (99.6% from European countries) in the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme, 2007-2020, were investigated. The minimum inhibitory concentrations (MICs) of the isolates with six commonly used agents were determined using the agar dilution method. Among the isolates, 10 Bacteroides spp. were included: B. fragilis (n=3180, 64.0%) was encountered most frequently, followed by B. thetaiotaomicron (n=675) and B. ovatus (n=409). During the 14 years, the proportion of B. fragilis declined, but the proportion of non-fragilis Bacteroides spp. increased. More than 90% of the isolates tested were susceptible to piperacillin-tazobactam, meropenem and tigecycline. Significantly lower susceptibility rates to cefoxitin (P<0.001), clindamycin (P<0.001), piperacillin/tazobactam (P<0.001) and tigecycline (P=0.006) were observed among non-fragilis Bacteroides spp. isolates than among B. fragilis isolates. Moreover, the susceptibility rates to clindamycin (P=0.003) and tigecycline (P=0.044) decreased significantly among non-fragilis Bacteroides spp. over time. Clindamycin susceptibility rates >80% were found in Greece (100%), Sweden (86.3%) and the UK (80.7%), and the lowest susceptibility rates were found in the USA (42.9%) and Japan (53.9%). In conclusion, the susceptibility of Bacteroides spp. to commonly used antibiotics varied geographically. Empirical antibiotic therapy for suspected anaerobic infections with clindamycin and cefoxitin should be avoided due to high resistance rates. Piperacillin-tazobactam, meropenem, metronidazole and tigecycline could be considered favourable options for the treatment of infections caused by Bacteroides spp.

Characterization of mobile genetic elements in multidrug-resistant Bacteroides fragilis isolates from different hospitals in the Netherlands.

OBJECTIVES: Five human clinical multidrug-resistant (MDR) Bacteroides fragilis isolates, including resistance to meropenem and metronidazole, were recovered at different hospitals in the Netherlands between 2014 and 2020 and sent to the anaerobic reference laboratory for full characterization. METHODS: Isolates were recovered from a variety of clinical specimens from patients with unrelated backgrounds. Long- and short-read sequencing was performed, followed by a hybrid assembly to study the presence of mobile genetic elements (MGEs) and antimicrobial resistance genes (ARGs). RESULTS: A cfxA gene was present on a transposon (Tn) similar to Tn4555 in two isolates. In two isolates a novel Tn was present with the cfxA gene. Four isolates harbored a nimE gene, located on a pBFS01_2 plasmid. One isolate contained a novel plasmid carrying a nimA gene with IS1168. The tetQ gene was present on novel conjugative transposons (CTns) belonging to the CTnDOT family. Two isolates harbored a novel plasmid with tetQ. Other ARGs in these isolates, but not on an MGE, were: cfiA, ermF, mef(EN2), and sul2. ARGs harboured differed between isolates and corresponded with the observed phenotypic resistance. CONCLUSIONS: Novel CTns, Tns, and plasmids were encountered in the five MDR B. fragilis isolates, complementing our knowledge on MDR and horizontal gene transfer in anaerobic bacteria.

High prevalence of cfiA positive Bacteroides fragilis isolates collected at a teaching hospital in Hohhot, China.

OBJECTIVES: Carbapenem-resistant Bacteroides fragilis has emerged globally and cfiA is the key underlying factor. However, the prevalence of cfiA-positive carbapenem-resistant B. fragilis varies among countries. Therefore, we investigated the prevalence of cfiA-positive B. fragilis clinical isolates in a tertiary hospital in China. METHODS: Carbapenem-resistant cfiA-positive B. fragilis isolates were identified using polymerase chain reaction. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to identify the characteristic mass spectra of cfiA-positive B. fragilis. RESULTS: The prevalence of cfiA among 153 B. fragilis isolates was 22.2% (34/153), when 20.6% (7/34) cfiA-positive B. fragilis strains were isolated from pediatric patients. Twenty-one carbapenem-resistant B. fragilis isolates were identified and were all positive with cfiA gene. Two characteristic peaks (4825 and 9642 Da) were identified using MALDI-TOF MS, and the sensitivity, specificity, and both the positive and negative predictive values of these two peaks were 100%. A new peak shift from 9627 Da for cfiA-negative isolates to 9642 Da for cfiA-positive isolates was observed. CONCLUSIONS: A high prevalence of cfiA was observed among B.fragilis isolates in this study, especially those isolated from pediatric patients. Characteristic MS spectra can accurately discriminate cfiA-positive and -negative B. fragilis isolates and can contribute to the rapid screening of cfiA-positive B. fragilis isolates in clinical laboratories.

Prevalence of antimicrobial resistant genes in Bacteroides spp. isolated in Oita Prefecture, Japan.

INTRODUCTION: Bacteroides spp. are the most common anaerobic bacteria isolated from the human gastrointestinal tract. Several resistant genes are present in Bacteroides spp. However, most studies have focused on the prevalence of the cfiA gene in Bacteroides fragilis alone. We assessed the susceptibility to antimicrobial agents and the prevalence of cepA, cfiA, cfxA, ermF, nim, and tetQ genes in Bacteroides strains isolated from clinical specimens in our hospital. METHODS: We isolated 86 B. fragilis and 58 non-fragilis Bacteroides strains from human clinical specimens collected from January 2011 to November 2021. Resistance against piperacillin (PIPC), cefotaxime (CTX), cefepime (CFPM), meropenem (MEPM), clindamycin, and minocycline was determined. RESULTS: The resistant rates of penicillins and cephalosporins in non-fragilis isolates were significantly higher than those in B. fragilis isolates. In B. fragilis isolates, the resistant rates of PIPC, CTX, and CFPM in cfxA-positive isolates were significantly higher than those in cfxA-negative isolates (71% vs. 16%, 77% vs. 19%, and 77% vs. 30%, respectively). Thirteen B. fragilis isolates harbored the cfiA gene, two of which were resistant to MEPM. Six of the 13 cfiA-positive B. fragilis isolates were heterogeneously resistant to MEPM. CONCLUSION: It is important to evaluate the use of MEPM as empirical therapy for Bacteroides spp. infections, considering the emergence of carbapenem resistance during treatment, existence of MEPM-resistant strains, and heterogeneous resistance.

Comparative Genomics of Bacteroides fragilis Group Isolates Reveals Species-Dependent Resistance Mechanisms and Validates Clinical Tools for Resistance Prediction.

Bacteroides fragilis group (BFG) are the most frequently recovered anaerobic bacteria from human infections, and resistance to frontline antibiotics is emerging. In the absence of routine antimicrobial susceptibility testing (AST) for BFG in most clinical settings, we assessed the utility of clinical and modern genomics tools to determine BFG species-level identification and resistance patterns. A total of 174 BFG clinical isolates supplemented with 20 archived carbapenem-resistant B. fragilis sensu stricto (BFSS) isolates underwent antimicrobial susceptibility testing, MALDI-ToF mass-spectrometry, and whole-genome sequencing (WGS). Bruker BioTyper and VITEK-MS MALDI-ToF systems demonstrated accurate species-level identifications (91% and 90% agreement, respectively) compared to average nucleotide identity (ANI) analysis of WGS data. Distinct ß-lactamase gene profiles were observed between BFSS and non-fragilis Bacteroides species, with significantly higher MICs to piperacillin-tazobactam in B. vulgatus and B. thetaiotaomicron relative to BFSS (P ≤ 0.034). We also uncovered phylogenetic diversity at the genomospecies level between division I and division II BFSS (ANI <0.95) and demonstrate that division II BFSS strains harbor an increased capacity to achieve carbapenem resistance through chromosomal activation of the CfiA carbapenemase. Finally, we report that CfiA detection by the Bruker BioTyper Subtyping Module accurately detected carbapenem resistance in BFSS with positive and negative percent agreement of 94%/90% and 95%/95% compared to ertapenem and meropenem susceptibility, respectively. These comparative analyses indicate that resistance mechanisms are distinct at both the phenotypic and genomic level across species within the BFG and that modern MALDI-ToF identification systems can be used for accurate species-level identification and resistance prediction of the BFG. IMPORTANCE Anaerobic infections present unique challenges in terms of detecting and identifying the etiologic agent and selecting the optimal antimicrobial therapy. Antimicrobial resistance is increasing in anaerobic pathogens, and it is critical to understand the prevalence and mechanisms of resistance to commonly prescribed antimicrobial therapies. This study uses comparative genomics to validate clinical tools for species-level identification and phenotypic resistance prediction in 194 isolates of Bacteroides fragilis group (BFG) bacteria, which represent the most commonly isolated organisms among anaerobic infections. We demonstrate species-specific patterns in antimicrobial resistance and validate new strategies for species-level organism identification and phenotypic resistance prediction in a routine clinical laboratory setting. These findings expand our understanding and management of anaerobic infections and justify further investigations into the molecular basis for species-specific resistance patterns observed within this study.

A comparison of the antimicrobial resistance of fecal Bacteroides isolates and assessment of the composition of the intestinal microbiotas of carbapenem-treated and non-treated persons from Belgium and Hungary.

The antimicrobial susceptibilities of Bacteroides strains isolated from the feces of imipenem-treated patients from Belgium and Hungary were compared with those isolated from the normal microbiota from these two and five other European countries and assessed. Of the 10 antibiotics tested, highly significant differences were found with cefoxitin (decrease for Belgium and for this two and the five countries from the previous study), clindamycin (decrease for Belgium and for this two and the five countries from the previous study) and moxifloxacin (increase for Belgium and for this two and the five countries from the previous study) relative to normal microbiota strains reported earlier. Imipenem treatment brought about modest, but notable differences in the compositions of the microbiomes where there was less diversity in the treated group relative to the non-treated group.

High frequency of enterotoxigenic Bacteroides fragilis and Enterococcus faecalis in the paraffin-embedded tissues of Iranian colorectal cancer patients.

BACKGROUND: The association between specific bacteria and colorectal cancer (CRC) has been proposed. Only a few studies have, however, investigated this relationship directly in colorectal tissue with conflicting results. So, we aimed to quantitate Streptococcus gallolyticus, Fusobacterium spp, Enterococcus faecalis and enterotoxigenic Bacteroides fragilis (ETBF) in formalin-fixed and paraffin-embedded (FFPE) colorectal tissue samples of Iranian CRC patients and healthy controls. METHODS: A total of 80 FFPE colorectal tissue samples of CRC patients (n = 40) and healthy controls (n = 40) were investigated for the presence and copy number of above bacterial species using quantitative PCR. Relative quantification was determined using ΔΔCT method and expressed as relative fold difference compared to reference gene. RESULTS: Relative abundance and copy number of E. faecalis and ETBF were significantly higher in CRC samples compared to control group. E. faecalis was more prevalent than ETBF in tumor samples. Frequency of ETBF and E. faecalis in late stages (III/IV) of cancer was significantly higher than early stages (I/II). We did not detect a significant difference in abundance of S. gallolyticus and Fusobacterium spp between two groups. CONCLUSION: Our study revealed the higher concentration of E. faecalis and ETBF in FFPE samples of CRC patients than controls. However, additional investigations on fecal and fresh colorectal cancer tissue samples are required to substantiate this correlation.

UK Bacteroides species surveillance survey: Change in antimicrobial resistance over 16 years (2000-2016).

OBJECTIVES: To assess the differences in antimicrobial susceptibility of UK Bacteroides species across two distinct cohorts from 2000 to 2016. METHODS: Strain identification was performed using matrix-assisted laser-desorption ionisation time of flight mass spectrometry (MALDI-TOF MS) or by partial 16S rRNA sequencing. Minimum inhibitory concentrations (MICs) were determined using agar dilution, following CLSI guidelines (CLSI, 2012; 2017). RESULTS: 224 isolates were included from 2000 to 168 from 2016. Bacteroides fragilis was the most common species, comprising 68% of the 2000 cohort, and 77% in 2016. For all antimicrobials tested, there was an overall increase in the rates of non-susceptible isolates between the cohorts. CONCLUSIONS: The antibiogram of Bacteroides species in the UK is no longer predictable. Multi-drug resistant isolates although rare, are on the rise, and require testing to guide therapy. The monitoring and surveillance of resistance trends is imperative, as is the development of standardised, robust and accessible antimicrobial susceptibility testing methodology for clinical laboratories.

Yaws, Haemophilus ducreyi, and Other Bacterial Causes of Cutaneous Ulcer Disease in the South Pacific Islands.

Cutaneous ulcers in the tropics are a painful and debilitating condition that anchors people into poverty. In rural regions of the South Pacific, infectious cutaneous ulcers are caused mainly by bacteria, including Treponema pallidum pertenue (yaws), Haemophilus ducreyi, and polymicrobial ulcers. For this group of infections the term cutaneous ulcer disease (CUD) is proposed. Some infections can cause malformations on the bone that have a permanent impact on lives in endemic communities. Better characterization of CUD may help design diagnostic tools and more effective antimicrobial therapies. This review updates the knowledge of CUD and discusses optimized terminology and syndromic management.

Antimicrobial susceptibility and prevalence of resistance genes in Bacteroides fragilis isolated from blood culture bottles in two tertiary care hospitals in Japan.

The in vitro susceptibilities of Bacteroides fragilis to antimicrobial agents, especially to carbapenem, are a major concern in the treatment of patients with bloodstream infections. In this study, 50 isolates of B. fragilis were obtained from positive blood bottles from 2014 to 2019 in Saitama, Japan. Their susceptibility to ampicillin/sulbactam was reduced to 70.0% compared with a previous report, whereas they were still sufficiently susceptible to piperacillin/tazobactam (94.0%). Five cfiA-positive isolates (5/50, 10.0%) were identified that were resistant to doripenem and meropenem, and two of them carried an insertion sequence located upstream of the cfiA-coding region. In particular, imipenem should be considered as a first-line carbapenem for the empirical treatment of B. fragilis infection because only insertion sequence and cfiA double-positive strains showed resistance to imipenem. Thirty-six percent of the isolates had a reduced minimum inhibitory concentration for moxifloxacin. In addition, metronidazole should still be considered as an active agent for B. fragilis because all isolates were susceptible to this antibiotic and the prevalence of the nim gene was low in Japan.

A Europe-wide assessment of antibiotic resistance rates in Bacteroides and Parabacteroides isolates from intestinal microbiota of healthy subjects.

Here, we sought to assess the levels of antibiotic resistance among intestinal Bacteroides and Parabacteroides strains collected between 2014 and 2016 in Europe and also attempted to compare resistance levels between clinical and commensal isolates. Bacteroides and Parabacteroides isolates were recovered from faecal samples via the novel Bacteroides Chromogenic Agar (BCA) method. Antibiotic susceptibilities were determined by agar dilution for ten antibiotics. The values obtained were then statistically evaluated. Altogether 202 Bacteroides/Parabacteroides isolates (of which 24, 11.9%, were B. fragilis) were isolated from the faecal specimens of individuals taken from five European countries. The percentage values of isolates resistant to ampicillin, amoxicillin/clavulanate, cefoxitin, imipenem, clindamycin, moxifloxacin, metronidazole, tetracycline, tigecycline and chloramphenicol were 96.6, 4.5, 14.9, 2.0, 47.3, 11.4, 0, 66.2, 1.5 and 0%, respectively. These values are close to those reported in the previous European clinical Bacteroides antibiotic susceptibility survey except for amoxicillin/clavulanate and clindamycin, where the former was lower and the latter was higher in normal microbiota isolates. To account for these latter findings and to assess temporal effects we compared the data specific for Hungary for the same period (2014-2016), and we found differences in the resistance rates for cefoxitin, moxifloxacin and tetracycline.

Prevalence and antimicrobial susceptibility of enterotoxigenic extra-intestinal Bacteroides fragilis among 13-year collection of isolates in Kuwait.

BACKGROUND: Some strains of Bacteroides fragilis species are associated with diarrhea as a result of enterotoxin production (bft or fragilysin). Fragilysin is activated by C11 protease (fpn) and together with C10 protease (bfp) play a significant role in its invasiveness. The objectives of this study were to investigate the proportion of clinical isolates from extra-intestinal sources that are toxin producers and characterize the genes mediating toxin production. Clinical isolates submitted to our reference laboratory over the last 13 years were screened for toxin production using PCR technique. All stool isolates were excluded. The isolates were tested for their susceptibility to 8 antimicrobial agents by E test. Carbapenem resistance gene cfiA was detected by PCR. RESULTS: A total of 421 B. fragilis isolates were viable. Out of these, bft was detected in 210 (49.9%) isolates. Of the 210 bft-positive isolates, 171 (81.4%), 33 (15.7%) and 6 (2.8%) harbored bft-1, bft-2, and bft-3 genes, respectively. Twenty (9.5%) of the bft-positive strains originated from bloodstream infections. Twenty-five, 20 and 9 strains harbored bfp-1, bfp-2 and bfp-3 gene, respectively. Two, 3, 4 bfp isotypes were detected simultaneously in some of strains. The resistance rates against amoxicillin-clavulanic acid was 32%, clindamycin 62%, cefoxitin 26%, imipenem 11%, meropenem 17%, metronidazole 4%, piperacillin 61% and tigecycline 14%. A chromosomally located cfiA gene that encode metallo-ß-lactamase was identified in only 34 isolates (16.2%). CONCLUSIONS: The prevalence of enterotoxin-producing B. fragilis was high among the extra-intestinal isolates. Metronidazole was the most active agent against all isolates. There was no statistically significance difference between resistance rates among bft-positive and bft-negative isolates except for clindamycin.

High prevalence of division II (cfiA positive) isolates among blood stream Bacteroides fragilis in Slovenia as determined by MALDI-TOF MS.

Bacteroides fragilis can be classified into division I (cfiA negative) and division II (cfiA positive) isolates. Division II isolates have a silent chromosomal carbapenemase gene (cfiA) that can become overexpressed by an insertion of a mobile genetic element and thus develop a phenotypic resistance to carbapenems. Aims of our study were (i) to determine the prevalence of B. fragilis division II (cfiA positive) isolates among blood stream and non-blood stream isolates from two major Slovenian tertiary-care hospitals and (ii) to assess its influence on phenotypic resistance to imipenem. Consecutive non-duplicate B. fragilis isolates from blood stream and non-blood stream specimens were included in the analysis from 2015 to 2017 period. Data from laboratory information system were matched with mass spectra obtained with Microflex LT instrument and MALDI Biotyper 3.1 software (Bruker Daltonik, Bremen, Germany). All mass spectra were reanalyzed using Bruker taxonomy library. Spectra with a log(score) > 2.0 were further analyzed with cfiA library that separates B. fragilis division I and II isolates based on a log(score) value difference of >0.3. Minimal inhibitory concentrations (MICs) for imipenem were determined with Etest (bioMérieux, Marcy l'Étoile, France), using supplemented Brucella agar and EUCAST breakpoints (S ≤ 2 mg/L, R > 8 mg/L). Altogether 623 consecutive B. fragilis isolates were included in the analysis; 47 (7.5%) were isolated from blood stream and 576 (92.5%) from non-blood stream specimens. Among all study isolates, 51 (8.2%) proved to belong to division II (cfiA positive). The proportions of division II isolates among blood stream and non-blood stream isolates were 14.9% and 7.6%, respectively (p = 0.081, ns). In total, 1.3% (n = 8) were non-susceptible to imipenem (MIC >2 mg/L); 4.3% (n = 2) among blood stream and 1% (n = 6) among non-blood stream isolates. All imipenem resistant isolates belonged to division II. Modal MICs (MIC range) were 0.064 mg/L (0.016 mg/L-2 mg/L) and 0.125 mg/L (0.064 mg/L-≥32 mg/L) for division I and II isolates, respectively.

Prevalence of D. fragilis infection in the household contacts of a group of infected patients / Prevalencia de infección por D. fragilis en contactos domiciliarios de un grupo de pacientes infectados

INTRODUCTION: The results of a study on the household contacts of patients with D. fragilis infection are presented. METHODS: A prospective, descriptive study was carried out on all Dientamoeba fragilis-infected patients treated at the Tropical Medicine Unit of Hospital Universitario Central de Asturias between 2012- 2017 and their household contacts. Three stool samples per patient and three stool samples from each of their household contacts were concentrated and analysed. Polymerase chain reaction (PCR) was used to detect the presence of D. fragilis in all stool samples. Co-infection with E. vermicularis was studied in both groups. Patients and contacts who failed to deliver one or more samples for diagnosis and patients without household contacts were excluded. RESULTS: 44 Patients infected with D. fragilis, as well as their 97 household contacts were enrolled. 50.5% of household contacts had a positive PCR for D. fragilis. 20 were also coinfected with E. vermicularis. The presence of infection was significantly more frequent in patients with children (34/15 versus 24/24; p= 0.064; OR: 2.267 [0.988-5.199]), E. vermicularis infection in the children being 20/29 versus 0/48 (p = 0.0001), and in another family member being 29/20 versus 15/33 (p = 0.008; OR: 3.190 [1.384-7.352]). CONCLUSIONS: The prevalence of D. fragilis infection in household contacts was high. It was associated with the presence of children in the family nucleus and coinfection with E. vermicularis irrespective of gender, age, rural area or contact with animals

INTRODUCCIÓN: Los informes de sensibilidad acumulada son una herramienta valiosa para guiar el tratamiento empírico de infecciones urinarias, sobre todo en el contexto actual de crecientes tasas de resistencia. Nuestro objetivo es analizar la sensibilidad antimicrobiana de bacterias aisladas de urocultivos de pacientes pediátricos durante un período de 5 años. MÉTODOS: Estudio retrospectivo de los urocultivos del período 2011-2015. La identificación y estudios de sensibilidad se realizaron con el sistema Vitek-2 (BioMérieux(R)) y se interpretaron según los criterios de EUCAST. Se analizaron los datos de sensibilidad antimicrobiana según sexo y tramos de edad (neonatos, 1 mes-5 años, 5-15 años) y se compararon con los datos de mayores de 15 años. RESULTADOS: En el período analizado se procesaron 17.164 urocultivos de 7.924 pacientes menores de 16 años. Los porcentajes de sensibilidad en estos pacientes fueron: ampicilina 36,3%; amoxicilina/clavulánico 75,3%; cefuroxima 83,2%; cotrimoxazol 68,9%; ciprofloxacino 85,3%; fosfomicina 85,5%; nitrofurantoína 84,4%, y cefalosporinas de tercera generación 89-91%. Aminoglucósidos (>92%) y carbapenemas (95%) mantienen las mayores tasas de sensibilidad. La prevalencia de aislamientos productores de BLEE fue significativamente menor en niños menores de 16 años (1,5% vs. 4,1%). En menores de 16 años, los aislamientos de Escherichia coli procedentes de mujeres fueron significativamente (p < 0,0001) más sensibles a ampicilina (41% vs. 30%) y amoxicilina-clavulánico (82% vs. 72%) que en varones. CONCLUSIONES: La elaboración de informes de sensibilidad acumulados desglosados por edad o sexo permite detectar importantes diferencias. En nuestra área, cefuroxima puede considerarse como primera opción de tratamiento empírico en pacientes pediátricos

A multicentre survey of the antibiotic susceptibility of clinical Bacteroides species from Hungary.

BACKGROUND: The species of the Bacteroides fragilis group are important components of human microbiota, but as opportunistic pathogens they can be the causative agents of severe infections. METHODS: The major aims of our investigation were the evaluation of the susceptibility of 400 different Hungarian B. fragilis group isolates to 10 antibiotics by the agar dilution method, the comparison of our resistance data with previous national and international antibiotic resistance data and the comparison of present data in regional aspect. The MIC-values on 10 antibiotics of all the strains were determined with the agar dilution method by CLSI. The presence of the cfiA gene in Division II B. fragilis strains was confirmed by RT-PCR. RESULTS: We detected a relatively high resistance rate of ampicillin, moxifloxacin, clindamycin and tetracycline, but amoxicillin/clavulanic acid, metronidazole, tigecycline and chloramphenicol showed excellent activity. In this study, we found that 6.75% of the isolates were resistant to cefoxitin and 7% to meropenem, while 8.58% of our B. fragilis strains harboured the cfiA gene. Most of the meropenem resistant strains were isolated in one of the participating centres. In the case of meropenem, cefoxitin, clindamycin and high-level-ampicillin-resistant strains, we found significant regional differences. DISCUSSION: Most of the results of our study were concordant with previous national and international data, with the exception of amoxicillin/clavulanic acid, cefoxitin and meropenem. CONCLUSIONS: Our study highlighted the importance of the periodic monitoring of the antimicrobial susceptibility of Bacteroides species providing important information for the appropriate therapy.

Molecular characterisation of multidrug-resistant Bacteroides isolates from Hungarian clinical samples.

OBJECTIVES: Members of the Bacteroides fragilis group are the most important components of the normal human gut microbiota, however these bacteria can also cause severe infections. Due to frequent use of antibiotics, the spread of multidrug-resistant (MDR) strains is a real threat worldwide. METHODS: In a multicentre study, 400 Bacteroides isolates from five Hungarian microbiology laboratories were cultured and were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Minimum inhibitory concentrations (MICs) of ten antibiotics were determined by the agar dilution method and were evaluated according to EUCAST or CLSI breakpoints. RESULTS: Six MDR strains were found and their antibiotic resistance genes were investigated by molecular methods The DNA amplicon of B. fragilis SZ38 was sequenced to search for a mutation in the gyrA gene. Among the six MDR isolates, one cfiA-, two cepA-, three cfxA-, two ermG-, six tetQ-, three tetX- and two bexA-positive strains were found. None of the MDR isolates harboured cepA, nim, ermB or tetX1 genes. CONCLUSIONS: In the past 12 years, only a few cases of MDR Bacteroides infections have been reported. Within a comprehensive multicentre survey, we demonstrated the relatively high prevalence of MDR strains isolated in one centre with five isolates as well as one isolate from another centre during a relatively short period of time. This study highlights the importance of antimicrobial susceptibility testing and surveillance among B. fragilis group isolates.

Identification of CfiA coding genes in Bacteroides fragilis isolates recovered in Argentina. Inconsistencies in CfiA organization and nomenclature.

CfiA (CcrA) metallo-ß-lactamase is the main carbapenem resistance mechanism in B. fragilis. From cfiA positive isolates detected in a previous surveillance study, 3 displayed resistance to imipenem while the remaining were susceptible. The aim of this study was to identify the cfiA alleles and to analyze the presence of IS elements in their upstream regions. CfiA-1, CfiA-4, CfiA-13, CfiA-19 and CfiA-22 were detected. IS elements belonging to IS21 family and IS942 group were identified upstream to cfiA in the 3 imipenem resistant isolates. We present an exhaustive analysis of cfiA/CfiA registers in databases, illustrating the inconsistencies in both organization and nomenclature. According to this analysis CfiA family comprises nowadays 15 different CfiA variants coded by 24 cfiA sequences. Curation of CfiA database is mandatory, if not new cfiA admission at GenBank will contribute to make this classification more complex.

Prevalence and characterization of enterotoxigenic Bacteroides fragilis and toxigenic Clostridium difficile in a Taipei emergency department.

BACKGROUND/PURPOSE: Enterotoxigenic Bacteroides fragilis (ETBF) and toxin-encoding Clostridium difficile (TXCD) are associated with gastroenteritis. Routine anaerobic blood culture for recovery of these anaerobic pathogens is not used for the detection of their toxins, especially for toxin-variant TXCD. The aim of this study was to investigate the prevalence and risk factors of the genotypes of these anaerobes in patients with acute diarrheal illnesses. METHODS: The data and samples of 513 patients with gastroenteritis were collected in a Taipei emergency department from March 1, 2006 to December 31, 2009. Nonenterotoxigenic B. fragilis (NTBF) and ETBF and the toxin genotypes of TXCD were detected by molecular methods. RESULTS: The prevalence rates of NTBF, ETBF, and TXCD infections were 33.14%, 1.56%, and 2.34%, respectively. ETBF infections often occurred in the elderly (average age = 67.13 years) and during the cold, dry winters. TXCD infections were widely distributed in age and often occurred in the warm, wet springs and summers. The symptoms of ETBF-infected patients were significantly more severe than those of NTBF-infected patients. CONCLUSION: This study identified and analyzed the prevalence, risk factors, and clinical presentations of these anaerobic infections. Future epidemiologic and clinical studies are needed to understand the role of ETBF and TXCD in human gastroenteritis.

Emergence and evolution of an international cluster of MDR Bacteroides fragilis isolates.

OBJECTIVES: The aim of this study was to examine the antibiotic resistance profiles, antibiotic resistance mechanisms and possible 'clonal' nature of some MDR Bacteroides fragilis strains that simultaneously harboured cfiA, nimB, IS1186 and IS4351. METHODS: Antibiotic susceptibilities were determined by Etests and antibiotic resistance genes and different genetic elements were detected by applying PCR methods. The environments of the cfiA and nimB genes were also determined by sequencing. The transferability of the cfiA, nimB and tet(Q) genes was tested by conjugation. The genetic relatedness of the test strains was tested by ERIC-PCR or PFGE. The complete genome sequences of two strains (B. fragilis BF8 and O:21) were determined by next-generation sequencing. RESULTS: Most of the seven B. fragilis strains tested displayed multidrug resistance phenotypes; five strains were resistant to at least five types of antibiotics. Besides the common genetic constitution, ERIC-PCR implied high genetic relatedness. Similarities in some of the antibiotic resistance mechanisms [carbapenems (cfiA) and metronidazole (nimB)] also confirmed their common origin, but some other resistance mechanisms {MLSB [erm(F)] and tetracycline [tet(Q)]} and PFGE typing revealed differences. In B. fragilis BF8 and O:21, erm(F) and tet(X) genes were found with IS4351 borders, thus constituting Tn4351. All the strains were tet(Q) positive and transferred this gene in conjugation experiments, but not the cfiA and nimB genes. CONCLUSIONS: An international cluster of MDR B. fragilis strains has been identified and characterized. This 'clone' may have emerged early in the evolution of division II B. fragilis strains, which was suggested by the low-complexity ERIC profiles and differences in the PFGE patterns.

Anaerobic bacteraemia: a 10-year retrospective epidemiological survey.

In order to identify current trends in anaerobic bacteraemia, a 10-year retrospective study was performed in the University Hospital Brussel, Belgium. All clinically relevant bacteraemia detected from 2004 until 2013 were included. Medical records were reviewed in an attempt to define clinical parameters that might be associated with the occurrence of anaerobic bacteraemia. 437 of the isolated organisms causing anaerobic bacteraemia were thawed, subcultured and reanalyzed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF). There were an average of 33 cases of anaerobic bacteraemia per year during 2004-2008 compared to an average of 27 cases per year during 2009-2013 (P = 0.017), corresponding to a decrease by 19% between the first and the latter period. Also, the total number of cases of anaerobic bacteraemia per 100,000 patient days decreased from 17.3 in the period from 2004 to 2008 to 13.7 in the period 2009 to 2013 (P = 0.023). Additionally, the mean incidence of anaerobic bacteraemia decreased during the study period (1.27/1000 patients in 2004 vs. 0.94/1000 patients in 2013; P = 0.008). In contrast, the proportion of isolated anaerobic bacteraemia compared to the number of all bacteraemia remained stable at 5%. Bacteroides spp. and Parabacteroides spp. accounted for 47.1% of the anaerobes, followed by 14.4% Clostridium spp., 12.6% non-spore-forming Gram-positive rods, 10.5% anaerobic cocci, 8.2% Prevotella spp. and other Gram-negative rods and 7.1% Fusobacterium spp. The lower gastrointestinal tract (47%) and wound infections (10%) were the two most frequent sources for bacteraemia, with the origin remaining unknown in 62 cases (21%). The overall mortality rate was 14%. Further studies focusing on the antimicrobial susceptibility and demographic background of patients are needed to further objectify the currently observed trends.