Yuliya Zboromyrska

Aetiology of traveller’s diarrhoea: evaluation of a multiplex PCR tool to detect different enteropathogens

Travellers diarrhoea (TD) is the most common illness reported in international travellers. TD is caused by a wide range of pathogens, including bacteria, viruses and parasites. Multiplex PCR assays can be especially useful for studying the aetiology of TD. The first objective of this study was to evaluate the utility of the commercially available multiplex PCR (xTAG(®) Gastrointestinal Pathogen Panel (GPP)) for the diagnosis of TD. A total of 185 stool specimens obtained from 174 patients were processed using the GPP assay. This test detected 86 pathogens in 67 stool samples (67/185, 36.2%). Sixteen pathogens out of 86 were also detected by routine testing. The remaining pathogens (n = 70) required further confirmation by alternative techniques. Finally, 60 out of 70 pathogens were confirmed. The second objective of this study was to analyse the aetiology of TD based on the results obtained by the GPP test and routine methods. The primary pathogens causing TD were Shigella (24.2%) followed by enterotoxigenic Escherichia coli (ETEC) (23.2%), enteroaggregative E. coli (14.7%) and Giardia (13.7%). Significant regional differences were observed for ETEC with 19.4% of TD cases acquired in Africa, 11.3% in Asia and none in South Central (SC) America (p 0.01), Giardia was found in 1.5% of cases among those who had travelled to Africa, 14.1% of those who had travelled to Asia and 3% of those who had travelled to SC America (p 0.01). In conclusion, the GPP test improved the detection of enteropathogens and allowed better assessment of the aetiology of TD.

Identification of Clinically Relevant Corynebacterium spp., Arcanobacterium haemolyticum, and Rhodococcus equi by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

ABSTRACT The identification of 83 Corynebacterium, 13 Arcanobacterium haemolyticum, and 10 Rhodococcus equi strains by conventional methods (API Coryne complemented with 16S rRNA gene sequence analysis) was compared with matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry identification. The correlation between API and MALDI-TOF results was 89%. MALDI-TOF is a rapid and accurate system for identification of the above-mentioned microorganisms.

Rapid Diagnosis of Staphylococcal Catheter-Related Bacteraemia in Direct Blood Samples by Real-Time PCR

Catheter-related bacteremia (CRB) is an important cause of morbidity and mortality among hospitalized patients, being staphylococci the main etiologic agents. The objective of this study was to assess the use of a PCR-based assay for detection of staphylococci directly from blood obtained through the catheter to diagnose CRB caused by these microorganisms and to perform a cost-effectiveness analysis. A total of 92 patients with suspected CRB were included in the study. Samples were obtained through the catheter. Paired blood cultures were processed by standard culture methods and 4 ml blood samples were processed by GeneXpert-MRSA assay for the detection of methicillin-susceptible (MSSA) or methicillin-resistant (MRSA) Staphylococcus aureus, and methicillin-resistant coagulase-negative staphylococci (MR-CoNS). Sixteen CRB caused by staphylococci were diagnosed among 92 suspected patients. GeneXpert detected 14 out of 16 cases (87.5%), including 4 MSSA and 10 MR-CoNS in approximately 1 hour after specimen receipt. The sensitivity and specificity of GeneXpert were 87.5% (CI 95%: 60.4–97.8) and 92.1% (CI 95%: 83–96.7), respectively, compared with standard culture methods. The sensitivity of GeneXpert for S. aureus was 100%. Regarding a cost-effectiveness analysis, the incremental cost of using GeneXpert was of 31.1€ per patient while the incremental cost-effectiveness ratio of GeneXpert compared with blood culture alones was about 180€ per life year gained. In conclusion, GeneXpert can be used directly with blood samples obtained through infected catheters to detect S. aureus and MR-CoNS in approximately 1h after sampling. In addition, it is cost-effective especially in areas with high prevalence of staphylococcal CRB.

Usefulness of time-to-positivity in aerobic and anaerobic vials to predict the presence of Candida glabrata in patients with candidaemia

OBJECTIVES To determine whether time-to-positivity (TTP) in aerobic and anaerobic blood culture vials is useful to predict the presence of Candida glabrata in patients with candidaemia. METHODS TTP was recorded for both aerobic and anaerobic vials for each blood culture set of monomicrobial candidaemia. We considered TTP as the shortest time registered for any positive vial. Two diagnostic criteria were evaluated: the cut-off TTP value as obtained from a receiver operating characteristic curve and the detection of growth only or with a shorter TTP in anaerobic vials. RESULTS A total of 157 episodes were analysed of which 19 (12.1%) were due to C. glabrata. The TTP for C. glabrata was longer than that for other species. C. glabrata grew more frequently than other species in anaerobic vials [9/19 (47%) versus 19/138 (14%); P = 0.001] and also more often exclusively or earlier in anaerobic vials [7/19 (37%) versus 5/138 (4%); P < 0.0001]. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of a TTP >56.5 h for predicting the presence of C. glabrata were 47%, 88%, 36% and 92%, respectively. Growth detection only or earlier in anaerobic flasks had a sensitivity of 37%, a specificity of 96%, a PPV of 58% and an NPV of 92%. CONCLUSIONS Using the BACTEC 9240 system, a TTP ≤ 56.5 h is useful to rule out C. glabrata. In addition, in settings with an ~12% prevalence of C. glabrata candidaemia, yeast detection exclusively or earlier in anaerobic vials increases the probability of the presence of C. glabrata to 58%, which may be useful for early treatment optimization.

Advanced PCR-based molecular diagnosis of gastrointestinal infections: challenges and opportunities

ABSTRACT Acute infections of the gastrointestinal tract are among the most common infectious diseases. The etiological agents of gastroenteritis may be bacteria, viruses or protozoa. Identification of the etiological agents of acute diarrhea is important for the treatment and management of diarrheal diseases. Conventional stool culture for bacteria shows a low sensitivity and requires more than 24 hours. In addition, other approaches to detect viruses and protozoa mainly involve antigen detection, but this is not available for all enteropathogens, and microscopic observation requires training and is of low sensitivity. In this review, the authors describe currently available molecular methods to detect different enteropathogens and analyze the main advantages and disadvantages of these methods for laboratory diagnosis of gastroenteritis.

Evaluation of a Loop-Mediated Isothermal Amplification-Based Methodology To Detect Carbapenemase Carriage in Acinetobacter Clinical Isolates

ABSTRACT Carbapenem-resistant Acinetobacter baumannii is a major source of nosocomial infections worldwide and is mainly associated with the acquisition of OXA-type carbapenemases and, to a lesser extent, metallo-β-lactamases (MBLs). In this study, 82 nonepidemiologically related Acinetobacter strains carrying different types of OXA or MBL enzymes were tested using the Eazyplex system, a loop-mediated isothermal amplification (LAMP)-based method to rapidly detect carbapenemase carriage. The presence/absence of carbapenem-hydrolyzing enzymes was correctly determined for all isolates in <30 min.

Time to Positivity and Detection of Growth in Anaerobic Blood Culture Vials Predict the Presence of Candida glabrata in Candidemia: a Two-Center European Cohort Study

ABSTRACT This study shows the accuracy of exclusive or earlier growth in anaerobic vials to predict Candida glabrata in a large series of candidemic patients from two European hospitals using the Bactec 9240 system. Alternatively, C. glabrata can be predicted by a time to positivity cutoff value, which should be determined for each setting.

Evaluation of a rapid immunochromatographic test for the detection of OXA-48 carbapenemase

We evaluated the OXA-48K-Set, a rapid immunochromatographic test for the detection of Oxacillinase-48 (OXA-48) carbapenemases, among 37 strains expressing OXA-48 and OXA-48-like carbapenemases and 20 additional strains harboring other β-lactamases. The test showed 100% sensitivity and specificity and the results were obtained in 15minutes.

Perspectivas de futuro de la espectrometría de masas en microbiología

MALDI-TOF (matrix-assisted laser desorption ionization time-of-flight) mass spectrometry (MS) has been vigorously introduced in many clinical microbiology laboratories for the rapid and accurate identification of bacteria and fungi. In fact, the implementation of this methodology can be considered a revolution in these laboratories. In addition to microbial identification, MALDI-TOF MS is being used for the detection of some mechanisms of antibiotic resistance and for the molecular typing of bacteria. A number of current and future applications that increase the versatility of this methodology may also be mentioned. Among these are its direct application on clinical samples, the detection of toxins or specific microbial antigens, and its application in the fields of virology and parasitology.Resumen La espectrometria de masas (EM) MALDI-TOF (matrix-assisted laser desorption ionization time-of-flight) se ha introducido con fuerza en muchos laboratorios de microbiologia clinica para la identificacion rapida y precisa de bacterias y hongos. De hecho, podemos considerar la implementacion de esta metodologia como una revolucion en dichos laboratorios. Ademas de la identificacion microbiana, la EM MALDI-TOF se esta utilizando para la deteccion de algunos mecanismos de resistencia a los antibioticos y para la tipificacion molecular de bacterias. Sin embargo, existe una serie de aplicaciones actuales y futuras que aumentan la versatilidad de esta metodologia. Entre estas cabe destacar la aplicacion directa a partir de muestras clinicas; la deteccion de toxinas o de antigenos microbianos especificos, y las aplicaciones en el campo de la virologia y de la parasitologia.

Diarrea del viajero

Travellers diarrhoea (TD) is acquired primarily through ingestion of food and drinks contaminated with pathogens that cause diarrhoea. They can be bacteria, protozoa, helminths, and viruses. Globally, the most common causes of TD are two pathotypes of Escherichia coli (enterotoxigenic and enteroaggregative) and Campylobacter, although there are significant variations by geographic area visited. Most TD occurs in individuals traveling to low-middle income countries. The type of travel, length of stay, travellers age, and the presence of certain underlying conditions are important risk factors to consider for the acquisition of TD. While TD is usually a mild and self-limiting disease, half of travellers with TD experience some limitation of activities during their trip, while up to 10% will experience persistent diarrhoea or other complications. The purpose of this article is to provide an updated microbiological, epidemiological, and clinical profile of travellers diarrhoea, including known risk factors, as well as to make recommendations on the prevention and treatment of TD.