Bacteria known in animal infectious diseases can cause challenges in human diagnostic laboratories. We present pitfalls in the identification and susceptibility testing of Staphylococcus hyicus , a pathogen that typically causes exudative epidermitis in pigs. In this case, the coagulase-positive staphylococcus isolated from a septic patient was misidentified as Staphylococcus aureus .
This case describes evidence for a Shiga toxin-producing Escherichia coli (STEC) O146:H28 infection leading to hemolytic uremic syndrome in a neonate. STEC O146:H28 was linked hitherto with asymptomatic carriage in humans. Based on strain characteristics and genotyping data, the mother is a healthy carrier who transmitted the STEC during delivery. STEC strains belonging to the low-pathogenic STEC group must also be considered in the workup of neonatal hemolytic uremic syndrome.
BackgroundCampylobacter fetus subspecies fetus (CFF) is an important pathogen for both cattle and humans. We performed a systematic epidemiological and clinical study of patients and evaluated the genetic relatedness of 17 human and 17 bovine CFF isolates by using different genotyping methods. In addition, the serotype, the dissemination of the genomic island containing a type IV secretion system (T4SS) and resistance determinants for tetracycline and streptomycin were also evaluated.MethodsThe isolates from patients diagnosed with CFF infection as well as those from faecal samples of healthy calves were genotyped using pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), as well as single locus sequence typing (SLST) targeting cmp1 and cmp2 genes encoding two major outer membrane proteins in CFF. The presence of the genomic island and identification of serotype was determined by PCRs targeting genes of the T4SS and the sap locus, respectively. Tetracycline and streptomycin resistance phenotypes were determined by minimal inhibitory concentration. Clinical data obtained from medical records and laboratory data were supplemented by data obtained via telephone interviews with the patients and treating physicians.ResultsPFGE analysis defined two major clusters; cluster A containing 16 bovine (80 %) isolates and cluster B containing 13 human (92 %) isolates, suggesting a host preference. Further genotypic analysis using MLST, SLST as well as sap and T4SS PCR showed the presence of genotypically identical isolates in cattle and humans. The low diversity observed within the cmp alleles of CFF corroborates the clonal nature of this pathogen. The genomic island containing the tetracycline and streptomycin resistance determinants was found in 55 % of the isolates in cluster A and correlated with phenotypic antibiotic resistance.ConclusionsMost human and bovine isolates were separated on two phylogenetic clusters. However, several human and bovine isolates were identical by diverse genotyping methods, indicating a possible link between strains from these two hosts.
An unusual increase in the number of Campylobacter concisus isolates found in stool cultures provoked an outbreak investigation at Bern University Hospital. No epidemiological links were found between the cases, and the Campylobacter isolates were clonally unrelated. A change in culture conditions to a hydrogen-rich atmosphere enhancing growth of C. concisus was deemed responsible for this pseudo-outbreak. Campylobacter concisus is a fastidious Campylobacter species whose pathogenic role in human disease has not been established. Isolation of C. concisus from samples has been reported in association with periodontal disease, Barrett's esophagus (1, 2), enteritis, and inflammatory bowel disease (IBD) (3), and the pathogen has been proposed to be linked to certain hepatobiliary and kidney conditions in children (4). High prevalences of C. concisus in stool samples were encountered not only in children and adults suffering from diarrhea (detection rate, 0.7% to 49%) but also in healthy controls (detection rate, 0% to 52%) (1, 3). Immunodeficiency (5) and age extremes (6, 7) appear to be determinants of a higher prevalence in stool. Moreover, C. concisus might be detected by PCR almost universally in human saliva samples (3). Thus, it is unresolved whether C. concisus is merely a commensal bacterium of the human digestive tract or a true pathogen. In light of its genetic variability, both of these may be true (1, 2). In late 2013, a substantial increase in the number of stool cultures testing positive for C. concisus was observed at the Bern University Hospital. In order to rule out an outbreak, an epidemiological investigation was conducted.Bern University Hospital is a 950-bed tertiary care teaching hospital in Switzerland. In the microbiology laboratory, approximately 2,000 stool samples are cultured for enteropathogenic bacteria each year. For Campylobacter cultures, clinical stool specimens were inoculated onto Preston agar plates and incubated in a microaerobic atmosphere at 35°C or 42°C for 48 h. Microaerobic conditions were obtained with gas generator packs (CampyGen, Oxoid, United Kingdom), producing a final atmosphere of 5% O 2 , 10% CO 2 , and 85% N 2 , or with evacuation and gas replacement of anaerobic jars (TriLab, Jenny Science, Switzerland) containing approximately 5% O 2 , 8% CO 2 , 15% H 2 , and 72% N 2 (replacing 76% of the air with an anaerobic gas mixture containing 70% N 2 , 20% H 2 , and 10% CO 2 ). Isolates were identified by matrix-assisted laser desorption-ionization time of flight mass spectrometry (MALDI-TOF MS) (Bruker Biotyper; Bruker Daltonics, Bremen, Germany) and sequence analysis using the MicroSeq 500 16S rRNA gene PCR and sequencing kits (Applied Biosystems, Foster City, CA). Genetic relatedness of the isolates was analyzed by repetitive extragenic palindromic PCR (rep-PCR) (8). A case was defined as any patient with C. concisus isolated from a stool sample between 2003 and 2013. Retrospective and prospective case finding was performed, including patients who met the case definiti...
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