Improving antimicrobial stewardship with penicillin allergy testing: a review of current practices and unmet needs

Penicillin allergy, the most frequently reported drug allergy, has been associated with suboptimal antibiotic therapy, increased antimicrobial resistance, increased rates of Clostridioides difficile colonization and infection, as well as extended hospital length of stay and increased cost. Although up to 10% of all patients may report penicillin allergy, most penicillin allergies are not confirmed. As such, most patients with a penicillin allergy can still safely use penicillin and related drugs following a more precise assessment. Herein, we review the current practices and unmet needs in penicillin allergy testing. The diagnostic algorithm is mostly based on a clinical history assessment followed by in vivo testing, i.e. skin test and/or drug challenge. As these tests are labour and resource intensive, there is increased interest in point-of-care penicillin allergy de-labelling solutions incorporated into Antimicrobial Stewardship Programmes including digital assessment tools. These can be locally parameterized on the basis of characteristics of target populations, incidence of specific allergies and local antibiotic usage to perform clinical risk stratification. Safely ruling out any residual risk remains essential and in vivo drug challenge and/or skin testing should be systematically encouraged. Gradual understanding and convergence of the risk stratification of the clinical presentation of penicillin allergy is enabling a wider implementation of this essential aspect of antimicrobial stewardship through digitalized decision tools and in vivo testing. More research is needed to deliver point of care in vitro diagnostic tools to democratize this de-labelling practice, which would be highly beneficial to patient care. This progress, together with better education of patients and clinicians about the availability, efficacy and safety of penicillin allergy testing, will increase the dissemination of penicillin allergy assessment as an important component of Antimicrobial Stewardship Programmes.

High prevalence and expression of antiseptic resistance genes among infectious t037/ST239 methicillin-resistant Staphylococcus aureus (MRSA) strains in North Khorasan Province, Iran

OBJECTIVES

Staphylococcus aureus is an important infectious agent and the majority of methicillin-resistant S. aureus (MRSA) infections are of nosocomial origin. To define the level and distribution of antiseptic resistance among infectious S. aureus strains we studied MRSA and methicillin-susceptible S. aureus (MSSA) isolates collected from different infection sites in an assortment of patients.

MATERIALS AND METHODS

S. aureus isolates were investigated for in vitro susceptibility to antiseptic agents and detection of qacA/B, smr, vanA, and mecA genes.

RESULTS

Among the S. aureus isolates we studied, 25 and 41 were MRSA and MSSA, respectively. The mean of minimum inhibitory concentrations (MICs) for benzethonium chloride (BTC) among MRSA was statistically significantly higher than for MSSA (26 µg/ml versus 11.7 µg/ml, P=0.003) while there was no significant difference between MRSA and MSSA for benzalkonium chloride (BKC) and chlorhexidine digluconate (CHG). The qacA/B genes were carried in 68% of the MRSA and 58.2% of MSSA (P=0.601), while smr was carried in 39% of MRSA and 29.3% of MSSA strains (P=1.000). In 15 out of 25 cases, MRSA ST239 with spa types t037, t030, and t7688 was isolated from the infection site with 86.6% of them carrying a resistance gene (qacA/B or qacA/B + smr).

CONCLUSION

The frequent presence of antiseptic resistance genes and a consequently elevated MIC against antiseptics among ST239 MRSA emphasizes the importance of mandatorily monitoring MRSA for effective infection control.

Novel strategies to diagnose prosthetic or native bone and joint infections

INTRODUCTION

Bone and Joint Infections (BJI) are medically important, costly and occur in native and prosthetic joints. Arthroplasties will increase significantly in absolute numbers over time as well as the incidence of Prosthetic Joint Infections (PJI). Diagnosis of BJI and PJI is sub-optimal. The available diagnostic tests have variable effectiveness, are often below standard in sensitivity and/or specificity, and carry significant contamination risks during the collection of clinical samples. Improvement of diagnostics is urgently needed.

AREAS COVERED

We provide a narrative review on current and future diagnostic microbiology technologies. Pathogen identification, antibiotic resistance detection, and assessment of the epidemiology of infections via bacterial typing are considered useful for improved patient management. We confirm the continuing importance of culture methods and successful introduction of molecular, mass spectrometry-mediated and next-generation genome sequencing technologies. The diagnostic algorithms for BJI must be better defined, especially in the context of diversity of both disease phenotypes and clinical specimens rendered available.

EXPERT OPINION

Whether interventions in BJI or PJI are surgical or chemo-therapeutic (antibiotics and bacteriophages included), prior sensitive and specific pathogen detection remains a therapy-substantiating necessity. Innovative tests for earlier and more sensitive and specific detection of bacterial pathogens in BJI are urgently needed.

An update on the routine application of MALDI-TOF MS in clinical microbiology

Introduction: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has entered clinical diagnostics and is today a generally accepted and integral part of the workflow for microbial identification. MALDI-TOF MS identification systems received approval from national and international institutions, such as the USA-FDA, and are continuously improved and adopted to other fields like veterinary and industrial microbiology. The question is whether MALDI-TOF MS also has the potential to replace other conventional and molecular techniques operated in routine diagnostic laboratories. Areas covered: We give an overview of new advancements of mass spectral analysis in the context of microbial diagnostics. In particular, the expansion of databases to increase the range of readily identifiable bacteria and fungi, the refined discrimination of species complexes, subspecies, and types, the testing for antibiotic resistance or susceptibility, progress in sample preparation including automation, and applications of other mass spectrometry techniques are discussed. Expert opinion: Although many new approaches of MALDI-TOF MS are still in the stage of proof of principle, it is expectable that MALDI-TOF MS will expand its role in the clinical microbiology laboratory of the future. New databases, instruments and analytical software modules will continue to be developed to further improve diagnostic efficacy.

Routine Whole-Genome Sequencing for Outbreak Investigations of Staphylococcus aureus in a National Reference Center

The French National Reference Center for Staphylococci currently uses DNA arrays and spa typing for the initial epidemiological characterization of Staphylococcus aureus strains. We here describe the use of whole-genome sequencing (WGS) to investigate retrospectively four distinct and virulent S. aureus lineages [clonal complexes (CCs): CC1, CC5, CC8, CC30] involved in hospital and community outbreaks or sporadic infections in France. We used a WGS bioinformatics pipeline based on de novo assembly (reference-free approach), single nucleotide polymorphism analysis, and on the inclusion of epidemiological markers. We examined the phylogeographic diversity of the French dominant hospital-acquired CC8-MRSA (methicillin-resistant S. aureus) Lyon clone through WGS analysis which did not demonstrate evidence of large-scale geographic clustering. We analyzed sporadic cases along with two outbreaks of a CC1-MSSA (methicillin-susceptible S. aureus) clone containing the Panton–Valentine leukocidin (PVL) and results showed that two sporadic cases were closely related. We investigated an outbreak of PVL-positive CC30-MSSA in a school environment and were able to reconstruct the transmission history between eight families. We explored different outbreaks among newborns due to the CC5-MRSA Geraldine clone and we found evidence of an unsuspected link between two otherwise distinct outbreaks. Here, WGS provides the resolving power to disprove transmission events indicated by conventional methods (same sequence type, spa type, toxin profile, and antibiotic resistance profile) and, most importantly, WGS can reveal unsuspected transmission events. Therefore, WGS allows to better describe and understand outbreaks and (inter-)national dissemination of S. aureus lineages. Our findings underscore the importance of adding WGS for (inter-)national surveillance of infections caused by virulent clones of S. aureus but also substantiate the fact that technological optimization at the bioinformatics level is still urgently needed for routine use. However, the greatest limitation of WGS analysis is the completeness and the correctness of the reference database being used and the conversion of floods of data into actionable results. The WGS bioinformatics pipeline (EpiSeq^TM) we used here can easily generate a uniform database and associated metadata for epidemiological applications.

Distribution of staphylococcal cassette chromosome mec types among methicillin-resistant coagulase negative staphylococci in central Iran

BACKGROUND AND OBJECTIVES

Methicillin-resistant coagulase-negative staphylococci (MR-CoNS) are important nosocomial pathogens. They may serve as a reservoir of SCCmec, the genomic island encoding amongst other methicillin resistance. This study was designed to determine the distribution of different SCCmec types from MR-CoNS isolated from clinical specimens in a tertiary hospital in central Iran, having high frequency of nosocomial methicillin-resistant staphylococcal infections.

MATERIALS AND METHODS

We evaluated isolates from patients attending the Vali-Asr Hospital located in the center of Iran, from February to December 2012. Multiplex PCR was performed for SCCmec typing. For isolates in which SCCmec could not be typed directly, additional ccr and mec complex analyses were performed.

RESULTS

Totally, 70 MR-CoNS isolates, comprising of 47 S. epidermidis strains (67%), 10 S. saprophyticus (14.3%), 9 S. hemolyticus (13%) and 4 S. lugdunensis (5.7%) were identified. Thirty-nine were characterized as type IVa 19 (27%), type III 11 (16%), type II 7 (10%) and type V 2 (3%). Only 20 isolates (28.6%) carried the ccr complex, while the current methods could not characterize the 11 remaining isolates.

CONCLUSION

A high level of SCCmec genetic diversity was found among MR-CoNS isolates. MR-CoNS may act as a reservoir of SCCmec IV for MRSA. This issue should be taken into consideration seriously.

Antimicrobial resistance: one world, one fight!

The lack of new antibiotic classes calls for a cautious use of existing agents. Yet, every 10 min, almost two tons of antibiotics are used around the world, all too often without any prescription or control. The use, overuse and misuse of antibiotics select for resistance in numerous species of bacteria which then renders antimicrobial treatment ineffective. Almost all countries face increased antimicrobial resistance (AMR), not only in humans but also in livestock and along the food chain. The spread of AMR is fueled by growing human and animal populations, uncontrolled contamination of fresh water supplies, and increases in international travel, migration and trade. In this context of global concern, 68 international experts attending the fifth edition of the World HAI Resistance Forum in June 2015 shared their successes and failures in the global fight against AMR. They underlined the need for a “One Health” approach requiring research, surveillance, and interventions across human, veterinary, agricultural and environmental sectors. This strategy involves concerted actions on several fronts. Improved education and increased public awareness are a well-understood priority. Surveillance systems monitoring infections need to be expanded to include antimicrobial use, as well as the emergence and spread of AMR within clinical and environmental samples. Adherence to practices to prevent and control the spread of infections is mandatory to reduce the requirement of antimicrobials in general care and agriculture. Antibiotics need to be banned as growth promoters for farm animals in countries where it has not yet been done. Antimicrobial stewardship programmes in animal husbandry have proved to be efficient for minimising AMR, without compromising productivity. Regarding the use of antibiotics in humans, new tools to provide highly specific diagnoses of pathogens can decrease diagnostic uncertainty and improve clinical management. Finally, infection prevention and control measures – some of them as simple as hand hygiene – are essential and should be extended beyond healthcare settings. Aside from regulatory actions, all people can assist in AMR reduction by limiting antibiotic use for minor illnesses. Together, we can all work to reduce the burden of AMR.

Detection of Staphylococcus aureus delta-toxin production by whole-cell MALDI-TOF mass spectrometry

The aim of the present study was to detect the Staphylococcus aureus delta-toxin using Whole-Cell (WC) Matrix Assisted Laser Desorption Ionization-Time-of-Flight (MALDI-TOF) mass spectrometry (MS), correlate delta-toxin expression with accessory gene regulator (agr) status, and assess the prevalence of agr deficiency in clinical isolates with and without resistance to methicillin and glycopeptides. The position of the delta-toxin peak in the mass spectrum was identified using purified delta-toxin and isogenic wild type and mutant strains for agr-rnaIII, which encodes delta-toxin. Correlation between delta-toxin production and agr RNAIII expression was assessed by northern blotting. A series of 168 consecutive clinical isolates and 23 unrelated glycopeptide-intermediate S. aureus strains (GISA/heterogeneous GISA) were then tested by WC-MALDI-TOF MS. The delta-toxin peak was detected at 3005±5 Thomson, as expected for the naturally formylated delta toxin, or at 3035±5 Thomson for its G10S variant. Multivariate analysis showed that chronicity of S. aureus infection and glycopeptide resistance were significantly associated with delta-toxin deficiency (p = 0.048; CI 95%: 1.01-10.24; p = 0.023; CI 95%: 1.20-12.76, respectively). In conclusion, the S. aureus delta-toxin was identified in the WC-MALDI-TOF MS spectrum generated during routine identification procedures. Consequently, agr status can potentially predict infectious complications and rationalise application of novel virulence factor-based therapies.

bro {beta}-lactamase and antibiotic resistances in a global cross-sectional study of Moraxella catarrhalis from children and adults

OBJECTIVES

To compare and contrast the geographic and demographic distribution of bro beta-lactamase and antibiotic MIC(50/90) for 1440 global Moraxella catarrhalis isolates obtained from children and adults between 2001 and 2002.

METHODS

One thousand four hundred and forty M. catarrhalis isolates originating from seven world regions were investigated. The isolates were recovered from 411 children <5 years of age and 1029 adults >20 years of age. PCR-restriction fragment length polymorphism (RFLP) was performed to determine bro prevalence and to distinguish between bro types. MIC values of 12 different antibiotics were determined using the CLSI (formerly NCCLS) broth microdilution method.

RESULTS

Of the 1440 isolates, 1313 (91%) possessed the bro-1 gene and 64 (4%) possessed the bro-2 gene. Additionally, the prevalence of bro positivity between the child and adult age groups was significantly different (P < 0.0001), though bro-1 and bro-2 prevalences within age groups were not significantly different. Consistently higher beta-lactam MICs were observed for M. catarrhalis isolates originating in the Far East. Significant correlations in MICs were observed for several antibiotic combinations, including all five beta-lactams with each other, and among the two quinolones.

CONCLUSIONS

The worldwide prevalence of bro gene carriage in clinical isolates of M. catarrhalis is now approaching 95%, with children significantly more likely to harbour bro-positive isolates than adults. Further, statistically significant differences in the distribution of beta-lactam MICs were observed between different world regions, particularly with respect to the Far East.

Multilocus Sequence Typing of Hospital-Associated Enterococcus faecium from Brazil Reveals Their Unique Evolutionary History

We studied the genetic relationships between vancomycin-susceptible (n = 11) and -resistant Enterococcus faecium (VRE, n = 20) recovered from Brazil using a multilocus sequence typing (MLST) scheme. Grouping of allelic profiles revealed six clusters of related sequence types (STs) that differ in no more than two of the seven alleles. Of these, one cluster harbored 16 of the 20 isolates recovered during the first VRE outbreak in Brazil. The ampicillin and gentamicin resistance profiles were stable in the isolates that clustered within the groups I-III. Comparison with the allelic profiles of 139 E. faecium from different geographical regions and origins found in the international database http://www.mlst.net revealed that the Brazilian outbreak clone did not cluster in the previously named complex-17. This genetic complex contains hospital epidemic and clinical isolates recovered from different countries and continents. Twenty two of the 31 Brazilian isolates, including the VRE outbreak clone, clustered apart from the E. faecium isolates from the database, suggesting that these Brazilian isolates have a distinct evolutionary history.

Co-infection with two different Campylobacter jejuni strains in a patient with the Guillain-Barré syndrome

Campylobacter jejuni is the predominant cause of antecedent infection in Guillain-Barré syndrome (GBS) or Miller Fisher syndrome (MFS). C. jejuni probably triggers GBS or MFS through molecular mimicry between bacterial sialylated lipo-oligosaccharides (LOS) and gangliosides in peripheral nerve tissue. We investigated whether co-infections with multiple C. jejuni strains occur in GBS or MFS patients and we further characterized these strains. PFGE analysis of 83 C. jejuni isolates from single primary colonies from stool cultures of 13 patients with GBS or MFS revealed co-infection with two different strains in one patient (8%). We showed that only strain GB5.1 contained an LOS biosynthesis gene locus that is associated with neuropathy. The patient serum strongly reacted with the LOS of strain GB5.1 and not with the LOS of strain GB5.2. Mass spectrometry revealed that both strains expressed a non-sialylated outer core structure in their LOS. The patient serum contained anti-asialo-GM2 antibodies that cross-reacted with the LOS of strain GB5.1. This study demonstrates that co-infection with multiple C. jejuni strains occurs in GBS patients. Consequently, not all C. jejuni strains isolated from the faeces of a GBS patient are involved in the pathogenesis of GBS per se. Furthermore, this is the first report in which cross-reactivity of antibodies to asialo-GM2 and to the LOS of a C. jejuni strain from a GBS patient has been demonstrated. This finding suggests that molecular mimicry with non-sialylated structures may also be involved in the pathogenesis of GBS.

Molecular epidemiology and antimicrobial susceptibility of Enterococci recovered from Brazilian intensive care units

We studied the antimicrobial resistance and the molecular epidemiology of 99 enterococcal surveillance isolates from two hospitals of Brasilia, Brazil. Conventional biochemical tests were used to identify the enterococcal species and the disk diffusion method was used to determine their resistance profiles. Enterococcus faecalis (76%) and E. faecium (9%) were the most prevalent species. No enterococci showed the vanA or vanB vancomycin resistance phenotypes or genotypes. Only the intrinsically resistant species E. gallinarum (n=2) and E. casseliflavus (n=3) harbored the vancomycin-resistance genes vanC1 and vanC2/3, respectively. We found E. faecalis isolates with high-level resistance to gentamicin (22%) and streptomycin (8%) and both E. faecalis and E. faecium isolates with resistance to more than two antimicrobials (84% and 67%, respectively). Nine E. faecalis isolates (12%) were resistant to ampicillin; the minimal inhibitory concentration (MIC) values were 16 microg/mL (n=6) and 32 microg/mL (n=3). Among these ampicillin-resistant E. faecalis, seven were also resistant to gentamicin, ciprofloxacin, rifampin, penicillin, chloramphenicol, tetracycline and erythromycin. Pulsed-field gel electrophoresis classified those isolates in three different genotypes, suggesting dissemination of genetically related ampicillin-resistant E. faecalis strains among different patients.

Enterotoxigenic Bacteroides fragilis (ETBF) strains isolated in The Netherlands and Poland are genetically diverse

Gram-negative anaerobic rods isolated in The Netherlands and Poland from extraintestinal and intestinal sources were identified as Bacteroides fragilis (n = 210) on the basis of Gram staining, growth on selective Bacteroides Bile Esculine medium as black colonies, and biochemical characteristics. PCR-mediated assessment of the presence of the B. fragilis enterotoxin (fragilysin) gene in all strains identified 12 so-called enterotoxin-positive B. fragilis (ETBF) strains (15%) among the Dutch strains and 16 ETBF among the Polish strains (13%). NotI Pulsed Field Gel Electrophoresis (PFGE) analysis revealed that these strains are genetically heterogeneous. Among the Dutch strains an identical pair and a set of four indiscriminate strains were identified. This suggests that limited nosocomial spread of ETBF can be observed. However, there was no identity obeserved when strains from The Netherlands were compared to their Polish counterparts. The antimicrobial susceptibility testing revealed that one Polish strain isolated from a patient with antibiotic associated diarrhoeae (AAD) was simultaneously highly resistant to clindamycin and cefoxitin (MIC>256 mg/L). Two other strains appeared to be clindamycin resistant. All resistant strains had different PFGE patterns, suggesting that resistance development occurred at independent occassions.

Recent emergence of an epidemic clindamycin-resistant clone of Clostridium difficile among Polish patients with C. difficile-associated diarrhea

Analysis of both the antibiotic resistance and the virulence characteristics of anaerobic human microbial pathogens is important in order to improve our understanding of a number of clinically significant infectious diseases, including Clostridium difficile-associated diarrhea (CDAD). We determined the presence of the clindamycin resistance-associated gene ermB and the ribotype of 33 C. difficile strains isolated from Polish patients suffering from CDAD. While all strains produced cytotoxin B (TcdB), enterotoxin A (TcdA) was produced by a subset of 15 strains only. The results showed that a single ermB-positive, TcdA(-)B(+) C. difficile strain with ribotype A has disseminated widely in the two Warsaw hospitals under investigation. Although different strains with the same phenotype were detected, the genotype A strain appeared to be the only one with a clear epidemic character. Apparently, enhanced local spread of CDAD-causing C. difficile may be restricted to a limited number of bacterial genotypes only.

Patterns of resistance associated with integrons, the extended-spectrum beta-lactamase SHV-5 gene, and a multidrug efflux pump of Klebsiella pneumoniae causing a nosocomial outbreak

Multiresistant Klebsiella pneumoniae caused a nosocomial outbreak. Resistance patterns of the presumed outbreak isolates varied among and within patients. In order to control the outbreak, screening for extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae was commenced. A number of susceptible K. pneumoniae strains were stored to serve as controls in genetic strain typing. Typing by pulsed-field gel electrophoresis proved the clonality of the strains in the recognized outbreak patients. Typing of the control strains by pulsed-field gel electrophoresis showed that at least one patient had been missed by the ESBL screening procedure. Further genetic typing confirmed the presence of the SHV-5 ESBL gene in all but one of the outbreak strains. Variable presence of integrons that carried the aminoglycoside resistance genes aadB and aadA2 was found. A gyrA mutation in codon 83 was present in all outbreak strains tested, despite considerable differences in ciprofloxacin MICs. The MICs of ciprofloxacin and the chemically unrelated drug cefoxitin were correlated (r = 0.86, P < 0.01) and were compatible with the overexpression of an efflux pump in a subset of the outbreak strains. We conclude that outbreak strains that express an ESBL gene only at a low level may pass unnoticed in a screening procedure, when the laboratory is unaware of variable ESBL expression. In this particular outbreak, screening for strains for which ciprofloxacin MICs were > or =0.25 micro g/ml would in retrospect have been the most sensitive method for detection of the K. pneumoniae outbreak strain.

Comparative evaluation of the BD Phoenix and VITEK 2 automated instruments for identification of isolates of the Burkholderia cepacia complex

We evaluated two new automated identification systems, the BD Phoenix (Becton Dickinson) and the VITEK 2 (bioMérieux), for identification of isolates of the Burkholderia cepacia complex (BCC). The test sample included 42 isolates of the highly virulent and epidemic genomovar III, 45 isolates of B. multivorans, and 47 isolates of other members of the BCC. Rates of correct identification by the BD Phoenix and VITEK 2 were similar when all BCC isolates were considered (50 and 53%, respectively) but differed markedly for genomovar III (71 and 38%; P < 0.01) and for B. multivorans (58 and 89%; P < 0.001). For the BD Phoenix as well as the VITEK 2, taking all 134 isolates of the BCC together, rates of correct identification of clinical isolates (56 and 55%, respectively; n = 85) were higher than those of environmental isolates (21 and 39%, respectively; n = 28). Clinical isolates of genomovar III (n = 27) showed correct identification rates of 81% (BD Phoenix) and 48% (VITEK 2) (P < 0.01). Rates of misidentification for BD Phoenix and VITEK 2 were 9 and 17% for genomovar III, 22 and 7% for B. multivorans, and 36 and 13% for the other BCC members (P < 0.01), respectively. More than half of the isolates misidentified by each instrument were identified as Ralstonia pickettii, Ralstonia paucula (CDC IV C-2 group), Alcaligenes faecalis, Achromobacter spp., or, for the VITEK 2, "various nonfermenters." This study reemphasizes that confirmatory identification of BCC, preferably by molecular methods, is highly recommended.

Attachment of Staphylococcus aureus to eukaryotic cells and experimental pitfalls in staphylococcal adherence assays: a critical appraisal

Staphylococcus aureus is a bacterial species with pathogenic potential to both humans and animals. The primary natural niche is said to be the human vestibulum nasi from where bacterial cells may spread to the environment or additional anatomical sites such as the perineum or the hands, where residence is usually transient. Apparently, S. aureus is capable of a precise and balanced interaction with specific types of eukaryotic nasal cells. Although a wide variety of important bacterial ligands and possible eukaryote receptors have been described, the precise mechanisms leading to persistent bacterial colonization and, even more importantly, associated infection have not yet been elucidated in detail. This may be a consequence of the fact that most of the adherence factors have been studied individually in simplified in vitro systems, not taking the complexity of multi-factorial in vivo cell-cell interactions into account. An overall scheme of the initial and sequential interactions leading to S. aureus colonization of eukaryotic cell surfaces has not yet emerged. This review concisely describes the current state of affairs in the multi-disciplinary field of staphylococcal adherence research. Specific emphasis is placed upon the pros and cons of the various artificial, mostly in vitro models employed to study the interaction between bacterial and human or animal cells.

PCR ribotyping and arbitrarily primed PCR for the comparison of enterotoxigenic Bacteroides fragilis strains from two Polish university hospitals

OBJECTIVE: To study the clinical incidence and possible clonal relatedness of enterotoxigenic strains of Bacteroides fragilis among pediatric and adult patients in two Polish university hospitals. METHODS: Fecal samples from 201 adults and 131 infants (with or without diarrhea) and vaginal samples from 100 pregnant women nursed in two Polish university hospitals were analyzed with respect to carriage of enterotoxin-producing Bacteroides fragilis (ETBF). This putative pathogen was identified by cultivation and subsequent cytopathogenicity testing of culture supernatants on HT/29 C1 cells. RESULTS AND DISCUSSION: Two ETBF strains were isolated from childrens' feces; two additional strains were isolated from adults, and from the vaginal samples only a single strain was isolated. One strain (W2) was isolated from a child with diarrhea. These incidence figures, the fact that all ETBF isolates were shown to produce strongly differing amounts of the cytotoxin, and the genetic unrelatedness of the strains as demonstrated by two different PCR-mediated DNA typing procedures, indicates that clonal spread of ETBF is presently not a clinical problem in these hospitals. It was shown that PCR-mediated ribotyping and arbitrarily primed PCR can be applied with success to study the epidemiology of ETBF.