Evaluation of the Light-Cycler® SeptiFast Test in Newborns With Suspicion of Nosocomial Sepsis

Use of Rapid Molecular Polymerase Chain Reaction in Early Detection of Bacteremia in Neonates Prior to Blood Culture Positivity: A Pilot Study

OBJECTIVE

 There has been national strive to decrease the time needed to identify microorganisms in blood culture samples to reduce antibiotic use. This study evaluated rapid molecular polymerase chain reaction (PCR) use in identifying microorganisms in negative culture bottles from neonates with suspected bacterial blood stream infection at 20 to 24 hours of incubation.

STUDY DESIGN

 All blood specimens from neonates with suspected blood stream infection were included. Specimens were incubated using a standard blood culturing instrument that would flag positive if bacterial growth was detected. If the specimen was flagged positive at <20 hours, it was tested by PCR and plated for identification as per standard protocol. In our design, if specimen was not flagged at 20 hours of incubation, the bottle was sterilely accessed and a sample was obtained for PCR testing. The bottle would be returned for incubation for 120 hours or until flagged positive.

RESULTS

 A total of 192 blood specimens were included. Four specimens flagged positive at <20 hours and were all found to be positive by PCR. All other samples did not flag positive by 20 hours of incubation and were tested by PCR between 20 and 24 hours. One sample tested positive via PCR at 21.6 hours then flagged positive on the culturing instrument at 23.5 hours. All other specimens were negative by PCR and remained culture negative at 120 hours. The positive and negative predictive value of PCR verified by blood culture were both equal to 1.0.

CONCLUSION

 Using rapid molecular PCR on blood culture specimens at 20 to 24 hours of incubation provides 100% true negative results possibly allowing providers to discontinue antibiotics at 24 hours.

KEY POINTS

· Antibiotic overuse leads to adverse neonatal outcomes.. · Molecular PCR may have true negative results.. · Larger study is needed to discontinue antibiotics earlier..

Emerging Technologies for Molecular Diagnosis of Sepsis

Rapid and accurate profiling of infection-causing pathogens remains a significant challenge in modern health care. Despite advances in molecular diagnostic techniques, blood culture analysis remains the gold standard for diagnosing sepsis. However, this method is too slow and cumbersome to significantly influence the initial management of patients. The swift initiation of precise and targeted antibiotic therapies depends on the ability of a sepsis diagnostic test to capture clinically relevant organisms along with antimicrobial resistance within 1 to 3 h. The administration of appropriate, narrow-spectrum antibiotics demands that such a test be extremely sensitive with a high negative predictive value. In addition, it should utilize small sample volumes and detect polymicrobial infections and contaminants. All of this must be accomplished with a platform that is easily integrated into the clinical workflow. In this review, we outline the limitations of routine blood culture testing and discuss how emerging sepsis technologies are converging on the characteristics of the ideal sepsis diagnostic test. We include seven molecular technologies that have been validated on clinical blood specimens or mock samples using human blood. In addition, we discuss advances in machine learning technologies that use electronic medical record data to provide contextual evaluation support for clinical decision-making.

Non-culture based assays for the detection of fungal pathogens

Traditional, culture based methods for the diagnosis of fungal infections are still considered as gold standard, but they are time consuming and low sensitive. Therefore, in order to overcome the limitations, many researchers have focused on the development of new immunological and molecular based rapid assays that could enable early diagnosis of infection and accurate identification of fungal pathogens causing superficial and invasive infection. In this brief review, we highlighted the advantages and disadvantages of conventional diagnostic methods and possibility of non-culture based assays in diagnosis of superficial fungal infections and presented the overview on currently available immunochromatographic assays as well as availability of biomarkers detection by immunodiagnostic procedures in prompt and accurate diagnosis of invasive fungal infections. In addition, we presented diagnostic efficiency of currently available molecular panels and researches in this area.

Molecular assays for the diagnosis of sepsis in neonates

BACKGROUND

Microbial cultures for diagnosis of neonatal sepsis have low sensitivity and reporting delay. Advances in molecular microbiology have fostered new molecular assays that are rapid and may improve neonatal outcomes.

OBJECTIVES

To assess the diagnostic accuracy of various molecular methods for the diagnosis of culture-positive bacterial and fungal sepsis in neonates and to explore heterogeneity among studies by analyzing subgroups classified by gestational age and type of sepsis onset and compare molecular tests with one another.

SEARCH METHODS

We performed the systematic review as recommended by the Cochrane Diagnostic Test Accuracy Working Group. On 19 January 2016, we searched electronic bibliographic databases (the Cochrane Library, PubMed (from 1966), Embase (from 1982), and CINAHL (from 1982)), conference proceedings of the Pediatric Academic Societies annual conference (from 1990), clinical trial registries (ClinicalTrials.gov, International Standard Randomised Controlled Trial Number (ISRCTN) registry, and World Health Organization (WHO) International Clinical Trials Platform (ICTRP) Search portal), and Science Citation Index. We contacted experts in the field for studies.

SELECTION CRITERIA

We included studies that were prospective or retrospective, cohort or cross-sectional design, which evaluated molecular assays (index test) in neonates with suspected sepsis (participants) in comparison with microbial cultures (reference standard).

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the methodologic quality of the studies and extracted data. We performed meta-analyses using the bivariate and hierarchical summary receiver operating characteristic (HSROC) models and entered data into Review Manager 5.

MAIN RESULTS

Thirty-five studies were eligible for inclusion and the summary estimate of sensitivity was 0.90 (95% confidence interval (CI) 0.82 to 0.95) and of specificity was 0.93 (95% CI 0.89 to 0.96) (moderate quality evidence). We explored heterogeneity by subgroup analyses of type of test, gestational age, type of sepsis onset, and prevalence of sepsis and we did not find sufficient explanations for the heterogeneity (moderate to very low quality evidence). Sensitivity analyses by including studies that analyzed blood samples and by good methodology revealed similar results (moderate quality evidence).

AUTHORS' CONCLUSIONS

Molecular assays have the advantage of producing rapid results and may perform well as 'add-on' tests.

Intra-abdominal Candida spp infection in acute abdomen in a quality assurance (QA)-certified academic setting

AIMS

To evaluate the contribution of light microscopy to detecting Candida spp infection in patients with complicated intra-abdominal infections (IAIs) admitted for acute abdomen to a quality assurance (QA)-certified surgical emergency ward.

METHODS

We conducted a retrospective study (2008-2012) of 809 abdominal intraoperative or biopsy tissue specimens obtained from patients admitted with acute abdomen and microbiological samples positive for Candida spp. Demographic data, mortality, comorbidities, specimen type, microscopy results, special histological staining performed, antimicrobial therapy were collected and analysed. Any comments at the multidisciplinary team meeting was recorded in minutes of and approved.

RESULTS

Sixty-six patients with complicated IAIs due to Candida spp were identified (39 male, 27 female, mean±SD age 75±20 years). Candida albicans was isolated in 35 cases and Candida non-albicans spp in 31 cases. Candida spp were isolated from blood in 50% of all selected microbiological specimens. Patients were stratified according to Candida spp (albicans vs non-albicans), underlying cancer disease and no previous antimicrobial administration, and a positive correlation with C. albicans isolation was found (p=0.009 and p=0.048, respectively). Out of 41 cases with microscopic evaluation, we identified yeast forms, pseudohyphae or both, indicative of Candida spp, in 23. Identification of Candida spp in histological specimens was higher in C. albicans cases than in C. non-albicans cases (73% vs 37.5%). Microscopy allowed prompt treatment of all patients.

CONCLUSIONS

Light microscopy still has great diagnostic significance, being a solid QA step. It provides rapid information and clues in patients who may harbour impaired defence mechanisms, concurrent chronic conditions and/or cancer.