Detection of Scedosporium spp.: Colonizer or pathogen? A retrospective analysis of clinical significance and management in a large tertiary center.

Infections with Scedosporium spp. are emerging in the past two decades and are associated with a high mortality rate. Microbiological detection can be associated with either colonization or infection. Evolution from colonization into infection is difficult to predict and clinical management upon microbiological detection is complex. Microbiological samples from 2015 to 2021 were retrospectively analyzed in a single tertiary care center. Classification into colonization or infection was performed upon first microbiological detection. Clinical evolution was observed until July 2023. Further diagnostic procedures after initial detection were analyzed. Among 38 patients with microbiological detection of Scedosporium spp., 10 were diagnosed with an infection at the initial detection and two progressed from colonization to infection during the observation time. The main sites of infection were lung (5/12; 41.6%) followed by ocular sites (4/12; 33.3%). Imaging, bronchoscopy or biopsies upon detection were performed in a minority of patients. Overall mortality rate was similar in both groups initially classified as colonization or infection [30.7% and 33.3%, respectively (P = 1.0)]. In all patients where surgical debridement of site of infection was performed (5/12; 42%); no death was observed. Although death occurred more often in the group without eradication (3/4; 75%) compared with the group with successful eradication (1/8; 12.5%), statistical significance could not be reached (P = 0.053). As therapeutic management directly impacts patients' outcome, a multidisciplinary approach upon microbiological detection of Scedosporium spp. should be encouraged. Data from larger cohorts are warranted in order to analyze contributing factors favoring the evolution from colonization into infection.

Scedosporium is an environmental mould with a varied clinical relevance, as described in this cohort from a tertiary centre. Its microbiological detection represents a colonization or infection. An interdisciplinary approach is crucial for an optimal diagnostic strategy and patient outcome.

Evaluation of two rapid commercial assays for detection of Streptococcus agalactiae from vaginal samples.

INTRODUCTION: Streptococcus agalactiae, also known as group B streptococci (GBS), is associated with invasive infections in neonates. Identification of GBS vaginal colonization in pregnant women before delivery is essential for treatment with antibiotics to prevent intrapartum vertical transmission to the newborn. This study was designed to evaluate applicability of two rapid real-time PCRs in comparison to standard culture identification. MATERIAL AND METHODS: We compared the Xpert GBS assay, hereafter referred to as Xpert, and GenomEra GBS PCR, hereafter referred to as GenomEra. The standard culture identification consisted of two different agar plates as well as an enrichment broth. RESULTS: We analyzed vaginal samples of 260 pregnant women; 42 samples were tested GBS-positive by using standard culture as a gold standard, 30 by Xpert, and 37 by GenomEra. Xpert and GenomEra assays performed with sensitivities of 71.4% and 88.1% as well as specificities of 98.6% and 99.1%, respectively. Twelve vaginal samples were false-negative by Xpert and five samples by GenomEra. Interestingly, three negative Xpert results of standard culture-positive samples exhibited high Ct-values indicating the presence of GBS. If higher Ct-values are taken into consideration, the sensitivity of Xpert increases up to 78.6%. Moreover, only three Xpert PCRs had to be repeated, whereas two Genomera were invalid even after repetition and further 15 GenomEra PCRs were repeated because of borderline results or inhibition of the PCR test. CONCLUSIONS: In this study, GenomEra assay performed with a higher sensitivity than the Xpert PCR. On the other hand, the Xpert assay needs less hands-on-time for a sample preparation and requires approximately four-fold less repetitions as compared to the GenomEra assay. This robust performance of the Xpert assay make it applicable as a rapid intrapartum point-of-care test, although a higher sensitivity would be desirable. Therefore, culture in the 35-37 week of gestation remains the gold standard to detect vaginal colonization.

Assessing Antibiotic Tolerance of Staphylococcus aureus Derived Directly from Patients by the Replica Plating Tolerance Isolation System (REPTIS).

Antibiotic-tolerant Staphylococcus aureus poses a great challenge to clinicians as well as to microbiological laboratories and is one reason for treatment failure. Antibiotic-tolerant strains survive transient antibiotic exposure despite being fully susceptible in vitro. Thus, fast and reliable methods to detect tolerance in the routine microbiology laboratory are urgently required. We therefore evaluated the feasibility of the replica plating tolerance isolation system (REPTIS) to detect antibiotic tolerance in Staphylococcus aureus isolates derived directly from patients suffering from different types of infections and investigated possible connections to clinical presentations and patient characteristics. One hundred twenty-five S. aureus isolates were included. Replica plating of the original resistance testing plate was used to assess regrowth in the zones of inhibition, indicating antibiotic tolerance. Bacterial regrowth was assessed after 24 and 48 h of incubation, and an overall regrowth score (ORS) was assigned. Regrowth scores were compared to the clinical presentation. Bacterial regrowth was high for most antibiotics targeting protein synthesis and relatively low for antibiotics targeting other cellular functions such as DNA replication, transcription, and cell wall synthesis, with the exception of rifampin. Isolates with a blaZ penicillinase had lower regrowth in penicillin and ampicillin. Low ORSs were more prevalent among isolates recovered from patients with immunosuppression or methicillin-resistant S. aureus (MRSA) isolates. In conclusion, REPTIS is useful to detect antibiotic tolerance in clinical microbiological routine diagnostics. Further studies should evaluate the impact of rapid detection of antibiotic tolerance as a clinical decision-making tool for tailored antibiotic treatments.

Antimicrobial susceptibility testing is crucial when treating Finegoldia magna infections.

Finegoldia magna is an anaerobic gram-positive bacterium that can cause invasive human infections. Recently, a 52-year-old patient suffering from a periprosthetic joint infection (PJI) due to F. magna was treated with cefepime on hemodialysis; however, treatment failed due to relapse caused by antibiotic-resistant strains. Reports on the antimicrobial susceptibility of F. magna clinical isolates are rare. We collected 57 clinical F. magna isolates from Zurich, Switzerland, between September 2019 and July 2020 and tested their antimicrobial susceptibility to investigate the local resistance pattern. Antimicrobial susceptibility testing (AST) was evaluated for nine antibiotics (benzylpenicillin, amoxicillin/clavulanic acid, cefuroxime, cefepime, levofloxacin, rifampicin, metronidazole, doxycycline, and clindamycin) by E-test according to CLSI guidelines. All F. magna strains were susceptible to benzylpenicillin, amoxicillin/clavulanic acid, and metronidazole, while 75% to clindamycin. F. magna isolates showed MIC values lower than species-unrelated breakpoints for cefuroxime, levofloxacin, and cefepime in 93%, 56%, and 32% of the cases, respectively. MIC values for rifampicin and doxycycline were lower than locally determined ECOFFs in 98% and 72% of the cases, respectively. In summary, we recommend the use of benzylpenicillin, amoxicillin/clavulanic acid, or metronidazole without prior AST as first-line treatment option against F. magna PJI infections. If cefuroxime, cefepime, levofloxacin, rifampicin, doxycycline, or clindamycin are used, AST is mandatory.

Impact of MALDI-TOF MS identification on anaerobic species and genus diversity in routine diagnostics.

OBJECTIVES: Introduction of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has revolutionized bacterial identification in the last decade. In 2013, MALDI-TOF MS was implemented for the identification of anaerobic bacteria at our laboratory. This study analyzed the impact of MALDI-TOF MS on the number of different anaerobic genera and species identified in diagnostics. METHODS: 155 anaerobic human clinical isolates, representing the most frequently isolated anaerobic species at our laboratory, were identified by conventional biochemical methods and by a Bruker MALDI Biotyper (Bruker Daltonics, Bremen, Germany). Discrepancies were resolved by partial 16S rRNA gene sequence analysis. In addition, we compared the frequencies of anaerobic genera and species prior to the implementation of MALDI-TOF MS from 2008 to 2012 to the frequencies of anaerobes from 2013 to 2020 when MALDI-TOF MS was used for identification. RESULTS: The diversity of anaerobic bacteria increased from 12 genera and 20 species in 2012, before the introduction of MALDI-TOF MS, to 16 genera and 31 species in 2013 and to 20 genera and 41 species in 2020 when MALDI-TOF MS was used as primary identification method. MALDI-TOF MS allowed species assignment within closely related species such as the Bacteroides fragilis group in accordance with 16S identification, and correctly identified newly described anaerobic species. CONCLUSION: Introduction of MALDI-TOF MS identification increased genus and species diversity of the reported anaerobes at our laboratory. Updates to the MALDI-TOF MS database and new species descriptions will further increase the diversity of anaerobic bacteria isolated from infectious processes.

Invasive Aspergillosis Due to Aspergillus Section Usti: A Multicenter Retrospective Study.

BACKGROUND: Aspergillus spp. of section Usti (A. ustus) represent a rare cause of invasive aspergillosis (IA). This multicenter study describes the epidemiology and outcome of A. ustus infections. METHODS: Patients with A. ustus isolated from any clinical specimen were retrospectively identified in 22 hospitals from 8 countries. When available, isolates were sent for species identification (BenA/CaM sequencing) and antifungal susceptibility testing. Additional cases were identified by review of the literature. Cases were classified as proven/probable IA or no infection, according to standard international criteria. RESULTS: Clinical report forms were obtained for 90 patients, of whom 27 had proven/probable IA. An additional 45 cases were identified from literature review for a total of 72 cases of proven/probable IA. Hematopoietic cell and solid-organ transplant recipients accounted for 47% and 33% cases, respectively. Only 8% patients were neutropenic at time of diagnosis. Ongoing antimold prophylaxis was present in 47% of cases. Pulmonary IA represented 67% of cases. Primary or secondary extrapulmonary sites of infection were observed in 46% of cases, with skin being affected in 28% of cases. Multiple antifungal drugs were used (consecutively or in combination) in 67% of cases. The 24-week mortality rate was 58%. A. calidoustus was the most frequent causal agent. Minimal inhibitory concentrations encompassing 90% isolates (MIC90) were 1, 8, >16, and 4 µg/mL for amphotericin B, voriconazole, posaconazole, and isavuconazole, respectively. CONCLUSIONS: Aspergillus ustus IA mainly occurred in nonneutropenic transplant patients and was frequently associated with extrapulmonary sites of infection. Mortality rate was high and optimal antifungal therapy remains to be defined.

A rare case of severe gastroenteritis caused by Aeromonas hydrophila after colectomy in a patient with anti-Hu syndrome: a case report.

BACKGROUND: Aeromonas hydrophila is a gram-negative facultative anaerobic coccobacillus, which is an environmental opportunistic pathogen. A. hydrophila are involved in several infectious diseases such as gastroenteritis, septicemia and wound infections. However, gastroenteritis caused by Aeromonas spp. are rare and the clinical relevance of Aeromonas species in stool specimens is still under debate. CASE PRESENTATION: Our case concerns a 32-year-old woman who presented at hospital with a worsening watery diarrhea and fever requiring intensive care. A cholera-like illness was diagnosed. The patient had a past history of an anti-Hu syndrome with a myenteric ganglionitis. A molecular multiplex RT-PCR (QIAstat-Dx Gastrointestinal Panel, QIAGEN) covering a broad spectrum of diverse gastrointestinal pathogens performed directly from the stool was negative but the stool culture revealed growth of A. hydrophila. Further investigations of the A. hydrophila strain in cell cultures revealed the presence of a cytotoxic enterotoxin. CONCLUSIONS: Although A. hydrophila rarely causes gastroenteritis, Aeromonas spp. should be considered as a causative agent of severe gastroenteritis with a cholera-like presentation. This case highlights the need to perform culture methods from stool samples when PCR-based methods are negative and gastrointestinal infection is suspected.

Temporal and regional incidence of carbapenemase-producing Enterobacterales, Switzerland, 2013 to 2018.

IntroductionIn contrast to countries where carbapenemase-producing Enterobacterales (CPE) are endemic, only sporadic cases were reported in Switzerland until 2013. An aggravation of the epidemiological situation in neighbouring European countries indicated the need for a surveillance study in Switzerland.AimWe aimed to describe CPE distributions in Switzerland and identify epidemiological factors associated with changes in incidence.MethodsData on all human CPE isolates from 2013 to 2018 were collected by the Swiss Centre for Antibiotic Resistance (ANRESIS) and analysed for temporal and regional trends by Generalised Poisson regression. Isolates associated with infection or colonisation were included in a primary analysis; a secondary analysis included invasive isolates only. Statistical detection of regional clusters was performed with WHONET/SaTScan.ResultsWe analysed 731 CPE isolates, of which 325 (44.5%) were associated with screenings and 173 (23.7%) with infections. Yearly detection of CPE isolates increased considerably during the study period from 65 to 212. The most frequently isolated species were Klebsiella pneumoniae (54%) and Escherichia coli (28%). The most frequent genotypes were OXA-48 (43%), KPC (21%) and NDM (14%). In contrast to the French-speaking parts of Switzerland (West, Geneva) where OXA-48 were the predominant genotypes (around 60%), KPC was the most frequently detected genotype in the Italian-speaking region (63%). WHONET/SaTScan outbreak detection analysis identified seven clusters in five regions of Switzerland.ConclusionsIn a first continuous surveillance of CPE in Switzerland, we found that the epidemiological situation aggravated nationwide and that regional patterns of CPE genotypes mirrored the situation in neighbouring European countries.

Tentative breakpoints and areas of technical uncertainty for early reading automated disc diffusion for Enterobacterales.

BACKGROUND: Disc diffusion is a reliable, accurate and cost-efficient procedure for antimicrobial susceptibility testing (AST) but requires long (18-24 h) incubation times. Reading of disc diffusion after short incubation times (6-8 h) by automated systems is feasible but should be categorized with time-adapted breakpoints to reduce errors. OBJECTIVES: This study systematically compared early readings (6 and 8 h) of disc diffusion using an automated system with that of the standard 18 h EUCAST method. Time-adapted tentative breakpoints were proposed to discriminate susceptible from resistant isolates and areas of technical uncertainty were defined to minimize the risk of errors. METHODS: A total of 1106 Enterobacterales isolates with a wide variety of resistance mechanisms and resistance profiles were included. All isolates were analysed for susceptibility to amoxicillin/clavulanic acid, ceftriaxone, cefepime, meropenem, ciprofloxacin and gentamicin using the automated WASPLabTM system. Part of the collection (515 isolates) was also analysed for susceptibility to an additional 10 antibiotics. RESULTS: Separation between WT and non-WT populations was poorer at early incubation times than following standard incubation. Editing of rapid automated AST results after 6 and 8 h incubation with time-adapted breakpoints resulted in 84.0% and 88.5% interpretable results with assignment to the resistant or susceptible category. Major error and very major error rates for the 6 h readings were only 0.4% and 0.3%, virtually identical to those of 18 h AST reading. CONCLUSIONS: Time-adapted clinical breakpoints in disc diffusion testing for Enterobacterales allow for accurate automated AST interpretation after shortened incubation times for a large number of antibiotics, with the additional possibility of subsequent confirmation after 18 h incubation.

Alpha-defensin lateral flow test does not appear to be useful in predicting shoulder periprosthetic joint infections.

PURPOSE: Periprosthetic joint infections (PJIs) remain a challenging complication after shoulder arthroplasty. The antimicrobial peptide α-defensin has been proposed as a new synovial fluid biomarker in diagnosing PJIs. To date, only little data are available on the diagnostic accuracy of α-defensin in shoulder PJIs; thus, we aimed to evaluate its diagnostic value in a cohort of patients with a suspected shoulder PJI. METHODS: Between June 2016 and June 2018, we prospectively enrolled patients with a diagnostic shoulder aspiration due to painful shoulder arthroplasty or planned revision surgery. PJI diagnostics were performed according to the Musculoskeletal Infection Society (MSIS) criteria. All patients with an antibiotic therapy within two  weeks before enrollment, insufficient amount of synovial aspirate, or bloody aspiration were excluded. α-Defensin was measured in the synovial fluid using the α-defensin lateral flow (ADLF) test (Synovasure®). RESULTS: Out of 60 patients, we could include 29 (59% female) patients with a mean age of 70 (range, 50-92) years. A shoulder PJI was detected in five cases (Staphylococcus aureus, n = 2; Staphylococcus epidermidis, n = 2; Cutibacterium acnes, n = 1). The ADLF test was positive in seven out of 29 cases. According to the MSIS criteria, the ADLF test was false-negative in two patients and false-positive in four patients, resulting in sensitivity, specificity, and positive and negative predictive value of 60%, 83%, 43%, and 91%, respectively. The overall accuracy was 79%. CONCLUSION: The ALDF test does not appear to be useful in predicting shoulder PJIs but may be used as an additional diagnostic factor in rejecting these infections.

Association of Cutibacterium avidum Colonization in the Groin With Obesity: A Potential Risk Factor for Hip Periprosthetic Joint Infection.

Background: An increase in the incidence of hip periprosthetic joint infections caused by Cutibacterium avidum has recently been detected after hip arthroplasty with an anterior surgical approach. We raised the question of whether skin colonization with C. avidum differs between the anterior and the lateral thigh as areas of surgical incision fields. Methods: Between February and June 2017, we analyzed skin scrapings from the groin and the anterior and lateral thigh in patients undergoing a primary hip arthroplasty. We anaerobically cultured plated swab samples for Cutibacterium spp. for ≥7 days. Univariate logistic regression analysis was used to explore associations between body mass index (BMI) and colonization rate at different sites. Results: Twenty-one of 65 patients (32.3%) were colonized with C. avidum at any site, mainly at the groin (n = 16; 24.6%), which was significantly higher at the anterior (n = 5; 7.7%; P = .009) or lateral (n = 6; 9.2%; P = .02) thigh. Patients colonized with C. avidum did not differ from noncolonized patients in age or sex, but their BMIs were significantly higher (30.1 vs 25.6 kg/m2, respectively; P = .02). Furthermore, increased BMI was associated with colonization at the groin (odds ratio per unit BMI increase, 1.15; 95% confidence interval; 1.03-1.29; P = .01). Conclusions: The groin, rather than the anterior thigh, showed colonization for C. avidum in obese patients. Further studies are needed to evaluate current skin disinfection and draping protocols for hip arthroplasty, particularly in obese patients.

Propionibacterium avidum: A Virulent Pathogen Causing Hip Periprosthetic Joint Infection.

Background: Propionibacteria are important members of the human skin microbiota, but are also opportunistic pathogens associated with periprosthetic joint infection (PJI). While the role of Propionibacterium acnes in PJI has been widely described, insight into the capacity of Propionibacterium avidum to cause PJI is limited. Methods: An unusual cluster of 4 hip PJIs caused by P. avidum in one orthopedic center in 2015 prompted us to retrospectively identify and analyze clinical data related to previous P. avidum PJI cases (1997-2015). We also characterized the hemolytic and biofilm-producing capacity of our 4 clinical P. avidum strains isolated in 2015, and investigated their phylogenetic relationships by whole-genome sequencing. Results: We retrospectively identified 13 P. avidum PJIs, with the majority being hip-related infections (n = 11). Preoperative synovial fluid cultures were P. avidum positive in 63.6% of cases. Six of 12 patients (50%) with available case histories were treated with an exchange of the prosthesis. In all but 1 of the 6 patients treated with debridement-retention of the prosthesis, treatment failed, thus requiring a 2-stage revision. The isolated P. avidum strains showed a more pronounced hemolytic activity, but a similar biofilm-forming ability when compared to P. acnes. Whole-genome sequencing identified 2 phylogenetic clusters highly related to P. avidum PJI strains isolated in Sweden. Conclusions: We describe the largest series of P. avidum PJI predominantly located in the hip. Phylogenetic similarity of our P. avidum strains to PJI strains isolated elsewhere suggests that these invasive lineages may be common.

Whole-Genome Sequencing of Aggregatibacter Species Isolated from Human Clinical Specimens and Description of Aggregatibacter kilianii sp. nov.

Aggregatibacter species are commensal bacteria of human mucosal surfaces that are sometimes involved in serious invasive infections. During the investigation of strains cultured from various clinical specimens, we encountered a coherent group of 10 isolates that could not be allocated to any validly named species by phenotype, mass spectrometry, or partial 16S rRNA gene sequencing. Whole-genome sequencing revealed a phylogenetic cluster related to but separate from Aggregatibacter aphrophilus The mean in silico DNA hybridization value for strains of the new cluster versus A. aphrophilus was 56% (range, 53.7 to 58.0%), whereas the average nucleotide identity was 94.4% (range, 93.9 to 94.8%). The new cluster exhibited aggregative properties typical of the genus Aggregatibacter Key phenotypic tests for discrimination of the new cluster from validly named Aggregatibacter species are alanine-phenylalanine-proline arylamidase, N-acetylglucosamine, and ß-galactosidase. The name Aggregatibacter kilianii is proposed, with PN_528 (CCUG 70536T or DSM 105094T) as the type strain.

Corynebacterium Species Rarely Cause Orthopedic Infections.

Corynebacterium spp. are rarely considered pathogens, but data on Corynebacterium spp. as a cause of orthopedic infections are sparse. Therefore, we asked how often Corynebacterium spp. caused an infection in a defined cohort of orthopedic patients with a positive culture. In addition, we aimed to determine the species variety and the susceptibility of isolated strains to define potential treatment strategies. We retrospectively assessed all bone and joint samples that were collected between 2006 and 2015 from an orthopedic ward and that were positive for Corynebacterium spp. by culture. The isolates were considered relevant to an infection if the same Corynebacterium sp. was present in at least two samples. We found 97 orthopedic cases with isolation of Corynebacterium spp. (128 positive samples). These were mainly Corynebacterium tuberculostearicum (n = 26), Corynebacterium amycolatum (n = 17), Corynebacterium striatum (n = 13), and Corynebacterium afermentans (n = 11). Compared to the species found in a cohort of patients with positive blood cultures hospitalized in nonorthopedic wards, we found significantly more C. striatum- and C. tuberculostearicum-positive cases but no C. jeikeium-positive cases in our orthopedic cohort. Only 16 out of 66 cases (24.2%) with an available diagnostic set of at least two samples had an infection. Antibiotic susceptibility testing (AST) showed various susceptibility results for all antibiotics except vancomycin and linezolid, to which 100% of the isolates were susceptible. The rates of susceptibility of corynebacteria isolated from orthopedic samples and of isolates from blood cultures were comparable. In conclusion, our study results confirmed that a Corynebacterium sp. is most often isolated as a contaminant in a cohort of orthopedic patients. AST is necessary to define the optimal treatment in orthopedic infections.

Ureaplasma and Mycoplasma in kidney allograft recipients-A case series and review of the literature.

Ureaplasma urealyticum and Mycoplasma hominis are common inhabitants of the human genital tract. Increasingly, serious and sometimes fatal infections in immunocompromised hosts have been reported, highlighting their pathogenic potential. We reviewed the clinical impact of positive Ureaplasma spp. and Mycoplasma spp. urine cultures in 10 renal allograft recipients who presented with sterile leukocyturia. Five recipients remained asymptomatic. Five patients were symptomatic with dysuria or pain at the graft site. Three patients developed biopsy-proven acute graft pyelonephritis with graft dysfunction. One of these patients additionally showed a renal abscess as demonstrated by magnetic resonance imaging (MRI). All were successfully treated. A literature search revealed a substantial number of case reports with severe and sometimes fatal Ureaplasma spp. or Mycoplasma spp. infections in immunocompromised patients. Colonization rate is high in renal transplant patients. A subset of patients is at risk for invasive disease.

Comparison of phenotypic methods for the detection of penicillinase in Staphylococcus aureus and proposal of a practical diagnostic approach.

Objectives: Disc diffusion is a cost-efficient, low-complexity, reliable method for detection of blaZ -mediated benzylpenicillin resistance in Staphylococcus aureus if the zone edge is inspected. EUCAST breakpoints cannot fully separate ß-lactamase-positive from ß-lactamase-negative strains, and EUCAST recommends the zone edge test. Literature on nitrocefin-based testing and the zone edge test is scarce with wide variations in reported assay performance. Methods: This study compared two different nitrocefin-based commercial and in-house tests and the EUCAST-based zone edge test for penicillinase detection in S. aureus applying a PCR-based gold standard. Results: In total, 215 non-duplicate clinical S. aureus isolates were included in the study, of which 127 (59.1%) did not harbour a blaZ gene, whereas 88 (40.9%) were blaZ positive. This study showed that for blaZ detection the zone edge test is more sensitive (96.6%) than nitrocefin tests independent of using nitrocefin discs (87.5% sensitivity) or solution (89.8% sensitivity), and that the significant inter-person variations of the zone edge test are probably related to the training level of the individual investigators (individual sensitivity ranging from 68.2% to 96.6%, specificity ranging from 89.8% to 100%). Conclusions: In addition to continued and strict training of investigators, we propose mandatory checking of benzylpenicillin zone edges, particularly in an investigation zone from 26 to 30 mm, which can result in improved specificity/positive predictive value of the zone edge test (from 98.4% to 100%) but retains the high sensitivity/negative predictive value of the method.

Evaluation of the Bruker MALDI Biotyper for Identification of Fastidious Gram-Negative Rods.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has entered clinical laboratories, facilitating identification of bacteria. Here, we evaluated the MALDI Biotyper (Bruker Daltonics) for the identification of fastidious Gram-negative rods (GNR). Three sample preparation methods, direct colony transfer, direct transfer plus on-target formic acid preparation, and ethanol-formic acid extraction, were analyzed for 151 clinical isolates. Direct colony transfer applied with the manufacturer's interpretation criteria resulted in overall species and genus identification rates of 43.0% and 32.5%, respectively; 23.2% of the isolates were not identified, and two misidentifications (1.3%) were observed. The species identification rates increased to 46.4% and 53.7% for direct transfer plus formic acid preparation and ethanol-formic acid extraction, respectively. In addition, we evaluated score value cutoff alterations. The identification rates hardly increased by reducing the genus cutoff, while reducing the 2.0 species cutoff to 1.9 and to 1.8 increased the identification rates to up to 66.2% without increasing the rate of misidentifications. This study shows that fastidious GNR can reliably be identified using the MALDI Biotyper. However, the identification rates do not reach those of nonfastidious GNR such as the Enterobacteriaceae. In addition, two approaches optimizing the identification of fastidious GNR by the MALDI Biotyper were demonstrated: formic acid-based on-target sample treatment and reductions in cutoff scores to increase the species identification rates.

Optimal Length of Cultivation Time for Isolation of Propionibacterium acnes in Suspected Bone and Joint Infections Is More than 7 Days.

Diagnosis of Propionibacterium acnes bone and joint infection is challenging due to the long cultivation time of up to 14 days. We retrospectively studied whether reducing the cultivation time to 7 days allows accurate diagnosis without losing sensitivity. We identified patients with at least one positive P. acnes sample between 2005 and 2015 and grouped them into "infection" and "no infection." An infection was defined when at least two samples from the same case were positive. Clinical and microbiological data, including time to positivity for different cultivation methods, were recorded. We found 70 cases of proven P. acnes infection with a significant faster median time to positivity of 6 days (range, 2 to 11 days) compared to 9 days in 47 cases with P. acnes identified as a contamination (P < 0.0001). In 15 of 70 (21.4%) patients with an infection, tissue samples were positive after day 7 and in 6 patients (8.6%) after day 10 when a blind subculture of the thioglycolate broth was performed. The highest sensitivity was detected for thioglycolate broth (66.3%) and the best positive predictive values for anaerobic agar plates (96.5%). A prolonged transportation time from the operating theater to the microbiological laboratory did not influence time to positivity of P. acnes growth. By reducing the cultivation time to 7 days, false-negative diagnoses would increase by 21.4%; thus, we recommend that biopsy specimens from bone and joint infections be cultivated to detect P. acnes for 10 days with a blind subculture at the end.

Prosthetic Vascular Graft Infections: Bacterial Cultures from Negative-Pressure-Wound-Therapy Foams Do Not Improve Diagnostics.

We analyzed the diagnostic value of microorganisms cultured from negative-pressure-wound-therapy (NPWT) foam samples compared to that of microorganisms cultured from deep tissue samples from patients with vascular graft infections. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 58%, 86%, 81%, and 66%, respectively. The diagnostic value of microbiological cultures from NPWT foams was poor.

Clonality and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus at the University Hospital Zurich, Switzerland between 2012 and 2014.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is a global epidemic threat. The aim of this study was to determine which globally known MRSA lineages are currently present at our tertiary care hospital in Switzerland, a hospital with low MRSA prevalence. In light of the increasing prevalence of multi drug resistance including vancomycin resistance we also assessed antibiotic susceptibilities. METHODS: The 146 MRSA strains collected over two years (March 2012 until February 2014) at the University Hospital Zurich, Switzerland, were analyzed by PFGE analysis of SmaI digests in combination with spa-typing. In addition, representative isolates were analyzed by multi locus sequence typing (MLST). Susceptibilities to eight antibiotics were assessed using the Kirby-Bauer disc diffusion method. RESULTS: Isolates showed resistance to erythromycin (48%), ciprofloxacin (43%), clindamycin (31%), tetracycline (22%), and gentamicin (16%). All isolates were susceptible to vancomycin, 95% were susceptible to sulfamethoxazole/trimethoprim and rifampicin, respectively. PFGE analysis revealed 22 different patterns, with four major patterns that accounted for 53.4% of all MRSA isolates, and seven sporadic patterns. Spa typing revealed 50 different spa types with the predominant types being t008 (14%), t002 (10%), and t127 (9%). 82% of the MRSA isolates could be assigned to six clonal complexes (CCs) namely CC1 (10%), CC5 (23%), CC8 (18%), CC22 (17%), CC30 (11%), and CC45 (3%) based on spa-types, PFGE patterns, and MLST. Two isolates could not be typed by either PFGE analysis or spa-typing and three isolates had spa-types that have not yet been described. CONCLUSIONS: The combination of the two typing methods was more discriminatory as compared to the use of a single method. Several of the lineages that are predominant in Europe are present in our hospital. Resistances to antibiotics have decreased in comparison to a study conducted between 2004 and 2006.