Rapid diagnostics of orthopedic implant-associated infections using Unyvero ITI implant and tissue infection application is not optimal for Staphylococcus species identification.

OBJECTIVES: This pilot study aimed to compare the commercial Unyvero ITI multiplex PCR application (U-ITI, Curetis GmbH) with conventional culturing concerning (a) detection of pathogens, (b) time to detection of pathogens and (c) time to and quality of antibiotic treatment recommendation in diagnostics of orthopedic implant-associated infections (OIAI). RESULTS: 72 tissue biopsies from 15 consecutive patients with deep OIAI infections were analyzed with conventional culturing including phenotypic antibiotic susceptibility testing and the U-ITI. U-ITI showed lower sensitivity than conventional culturing concerning detection of pathogens (73% vs 93%). 4/15 patients would have been given false negative results by U-ITI, all of which were culture-positive for Staphylococcus species. Median time to detection of pathogens was 47 h and antibiotic resistance 89 h by conventional methods compared to 13.5 h with the U-ITI. The U-ITI did not detect antibiotic resistance, whereas conventional culturing showed resistance to antibiotics covered by the U-ITI panel in 2 patients. Time to detection of pathogens was improved, but the detection limit for staphylococci was unsatisfactory. Although the time to antibiotic treatment recommendation was significantly reduced, the U-ITI would have resulted in incorrect antibiotic recommendation in 2 patients. Our data do not support use of this assay in diagnostics.

The impact of age on risk assessment, therapeutic practice and outcome in candidemia.

BACKGROUND: In Norway, the epidemiological situation of candidemia is followed closely. We have previously demonstrated the highest incidence of candidemia in elderly >65 years of age. However, knowledge of other aspects of this infection is lacking. OBJECTIVE: The aim of this nationwide, retrospective study was to examine risk factors, therapeutic practice and outcome in adult candidemia patients according to age. METHODS: We retrieved data from medical records from patients who developed candidemia in Norway between 1 January 2008 and 31 December 2012. Data were analyzed according to age, younger patients being between 18 and 65 years, elderly being ≥65 years of age. RESULTS: From 771 eligible patients, 738 patients (95.7%) were included (58% men, mean age 65.2 years, 58.1% being ≥65 years). Exposure to health-care related risk factors for candidemia were significantly more common in the younger patients (neutropenia, central venous catheter, mechanical ventilation and chemotherapy) who received empirical treatment more often than the elderly (29.8% vs. 21.7%, p = .01). More elderly did not received any antifungal therapy (27.3% vs 16.8%, p < 0001) and had higher mortality compared to younger patients (45.5% vs 23.9%, p < .0001). In the study population, mortality was higher with age (per 10-years increase, OR 1.43;1.28-1.59, p < 0.0001), in patients not receiving targeted therapy (OR 2.5; CI 1.82-3.36, p < .0001) or any therapy at all (OR 4.64; 3.23-6.68, p < .0001). CONCLUSIONS: Risk factors for candidemia, treatment and outcome differed significantly according to age. Given the increasing numbers of elderly, scrutiny on our clinical practice is warranted.

erm gene distribution among Norwegian Bacteroides isolates and evaluation of phenotypic tests to detect inducible clindamycin resistance in Bacteroides species.

The aims of this study were to describe the distribution of the most common erm genes in a collection of Norwegian Bacteroides isolates and to investigate whether the phenotypic tests for determining inducible clindamycin resistance among Bacteroides species recommended by EUCAST, NordicAST and the manufacturer of E-test®, are effective. We investigated 175 unique Bacteroides isolates for the presence of erm(B), erm(F) and erm(G) genes, determined their minimum inhibitory concentrations (MICs) to clindamycin and categorised their susceptibility according to EUCAST breakpoints. 27 isolates were resistant to clindamycin. Furthermore, we investigated whether these recommended methods could detect inducible resistance in the Bacteroides isolates: 1) EUCAST recommendation: Dissociated resistance to erythromycin (clindamycin susceptible with erythromycin MIC > 32 mg/L), 2) NordicAST recommendation: Double disk diffusion test (DDD) or 3) Manufacturer of E-test®'s recommendation: prolonged incubation of clindamycin E-test® for 48 h. erm genes were detected in 30 (17%, 95% CI 12%-23%) of 175 Bacteroides isolates with erm(F) as the dominating gene. There were six (4%, 95% CI 1%-7%) of 148 clindamycin susceptible isolates harbouring erm genes, they were considered inducibly resistant to clindamycin. None of the methods for phenotypic detection of inducible clindamycin resistance performed satisfactory with sensitivities of 33%, 17% and 0% and specificities of 90%, 99% and 97% for dissociated resistance, DDD and prolonged incubation of clindamycin E-test®, respectively. In our view, the scientific basis for investigating every Bacteroides isolate for inducible resistance to clindamycin is weak. Molecular detection of erm genes may prove a better option than the phenotypic methods we evaluated.

Anaerobic blood culture isolates in a Norwegian university hospital: identification by MALDI-TOF MS vs 16S rRNA sequencing and antimicrobial susceptibility profiles.

We investigated 197 anaerobic isolates recovered from blood cultures in the period 2009-2013. The isolates included were Bacteroides spp., Clostridium spp., Prevotella spp., Fusobacterium spp. and Gram-positive anaerobic cocci (GPAC). Identification results by MALDI-TOF MS were compared to those obtained by 16S rRNA sequencing, and the MICs of benzylpenicillin, clindamycin, piperacillin-tazobactam, meropenem and metronidazole were determined by Etests. The MALDI-TOF MS correctly identified 94.9% of the anaerobes to the genus level, and 86.8% to the species level, with errors mainly among the non-fragilis Bacteroides spp. and GPAC. About 73.3% of the isolates were non-susceptible to penicillin, mainly due to high resistance rates in the Bacteroides spp. (99.2%) and Prevotella spp. (69.2%). About 18.5% of the isolates were clindamycin resistant. Piperacillin-tazobactam had an excellent activity against all anaerobes except the non-fragilis Bacteroides spp., of which 43.8% were non-susceptible. The clinical significance of such a high resistance rate is unclear. Meropenem and metronidazole were the most active antibiotics, with 96.9% and 97.9% of the isolates being susceptible.

Dolosigranulum pigrum causing biomaterial-associated arthritis.

Dolosigranulum pigrum is a gram-positive, catalase-negative bacteria rarely associated with disease. We report a case of biomaterial-associated arthritis in an immunocompetent patient caused by D. pigrum. The organism was isolated from a synovial biopsy specimen and its identity confirmed by 16S rRNA gene sequencing.

A large outbreak of Listeria monocytogenes infection with short incubation period in a tertiary care hospital.

OBJECTIVES: Listeria monocytogenes is a foodborne pathogen with a high mortality rate. We report a large, nosocomial outbreak of Listeria monocytogenes infection. METHODS: Patients with L. monocytogenes isolated from a sterile site, or from faeces when diarrhoea and fever were present, were included. Clinical data were collected from the patient records. The incubation period was calculated as the time between exposure and start of symptoms. RESULTS: Seventeen patients (11 women, median age 64 years) were infected of whom 15 patients were at increased risk for listeriosis. Eleven patients received empiric antibiotic treatment, eight of them with cephalosporins. Three patients died with a resulting mortality rate of 18%. The source of the outbreak was a Camembert cheese made from pasteurised milk containing up to 360 million colony forming units per portion. The median incubation period was 3-4 days. CONCLUSIONS: The incubation period in this outbreak was significantly shorter than previously reported, a fact that may be due to the high number of ingested bacteria. Furthermore, food restrictions in hospitals seem warranted, as do treatment with antibiotics effective against L. monocytogenes in at-risk populations.