Low Concentration Of Pathogens Research Articles

Current concepts in the prevention of pathogen transmission via blood/plasma-derived products for bleeding disorders

The pathogen safety of blood/plasma-derived products has historically been a subject of significant concern to the medical community. Measures such as donor selection and blood screening have contributed to increase the safety of these products, but pathogen transmission does still occur. Reasons for this include lack of sensitivity/specificity of current screening methods, lack of reliable screening tests for some pathogens (e.g. prions) and the fact that many potentially harmful infectious agents are not routinely screened for. Methods for the purification/inactivation of blood/plasma-derived products have been developed in order to further reduce the residual risk, but low concentrations of pathogens do not necessarily imply a low level of risk for the patient and so the overall challenge of minimising risk remains. This review aims to discuss the variable level of pathogenic risk and describes the current screening methods used to prevent/detect the presence of pathogens in blood/plasma-derived products.

Microfluidic platform for direct capture and analysis of airborne Mycobacterium tuberculosis.

Airborne Mycobacterium tuberculosis is the main source of tuberculosis infection, which is known as one of the worldwide infectious diseases. Direct capture and analysis of airborne Mycobacterium tuberculosis is essential for disease prevention and control. At present, low concentration of pathogens directly collected from the air is the major drawback for rapid analysis. Herein an integrated microfluidic system capable of airborne Mycobacterium tuberculosis capture, enrichment, and rapid bacteriological immunoassay was developed. The whole detection time was decreased to less than 50 min including 20 min of enrichment and 30 min of immunoreaction analysis. It had the advantages of low detection limit, fast detection speed, and low reagent consumption compared with conventional techniques, showing the potential to become a new airborne pathogen analysis platform.

Quantitative Detection of Shiga Toxin-Producing and Enteropathogenic Escherichia coli Serotypes O157 and O26 in Bulk Raw Milk

The presence of pathogens must be adequately monitored in raw milk and dairy products to assess their safety. With this aim, sampling plans and analytical methods should be evaluated for their appropriateness. Five incremental samples were collected from 40 milk tankers and overall 200 individual samples were analysed to assess the number and distribution of Escherichia coli O157 and O26. Enriched samples were screened by PCR for the presence of the serogroup-specific genes rfbEO157 and wzxO26, and the positive cultures were analysed by reverse transcriptase-PCR to detect mRNA sequences encoded by these genes, which are indicative of the presence of viable bacteria. In addition, the numbers of E. coli O157 and O26 in milk were estimated by most-probable-number–PCR method. The results of PCR screening targeting the rfbEO157 and wzxO26 genes were positive in 34 samples (representing 15 batches) and complementary mRNA sequences were detected in 27 of these (80 %). Isolation from the enriched cultures resulted in detection of E. coli O157 in 100 % of the enriched samples positive for the O157 RNA marker, whereas E. coli O26 was isolated from only 37.5 % of the enriched cultures positive for O26 RNA marker. E. coli strains that produce Shiga toxins O26:H11 was isolated from one batch (2.5 %), while typical enteropathogenic E. coli O26 and non-pathogenic strains of E. coli O157 were isolated from four other batches. Estimated by most-probable-number (MPN), the number of E. coli O157 or O26 was below 0.3 MPN ml−1 in all the milk samples, except two that had MPN equal to 1.4∙ml−1 (CI95% 0.36–4.2). The distribution of E. coli O157 and O26 within the milk batches was not uniform. Seven (47 %) of the 15 batches with positive results for either the O157 or O26 gene had only one incremental sample positive out of five samples analysed. In the presence of very low concentrations of pathogens, the sampling method used may affect the probability of detection of ‘defective’ batches.

Gruźlica narządów głowy i szyi – wciąż aktualny problem w praktyce laryngologicznej

It is estimated that between XVI and XIX century one fourth of European population died of tuberculosis. Nowadays tuberculosis is still one of the most important infectious diseases. In 2009 estimately 9 million new cases were registered worldwide, mortality due tuberculosis reached 1.5 million. In Poland extrapulmonary tuberculosis is rare (7% of overall morbidity) and most commonly affects pleura, lymph nodes, bones, joints and genitourinary system. Head and neck tuberculosis is rare and causes many diagnostics problems. Retrospective analysis of case histories of patients admitted to ENT Department of Silesian Medical University in Katowice. Between 1993 and 2010 four cases of head and neck tuberculosis were diagnosed in our Clinic. Two of patients were admitted to the hospital with symptoms of laryngeal tumor such as difficulty in swallowing. During direct laryngoscopy tissue specimens were taken. Examination of the third patient showed tumor located below left angle of mandibule. During superficial parotidectomy tumor was removed. In the fourth registered case tuberculosis manifested as tumor of nasopharynx. In every case which is mentioned above pathology reports revealed epithelioid cell granulomas with caseous necrosis typical for tuberculosis. Patients underwent tuberculostatic treatment. Rare occurrence and lack of characteristic symptoms of head and neck tuberculosis often lead to misdiagnosis. Histopathological examination is the most important diagnostic procedure. Microbiological examination is difficult in extrapulmonary tuberculosis, because of low concentration of pathogens in specimens. Tuberculostatic therapy is the leading method of treatment in every case of tuberculosis.

Method for Label-Free Detection of Femtogram Quantities of Biologics in Flowing Liquid Samples

Rapid (approximately 10 min) measurement of very low concentration of pathogens (approximately 10 cells/mL) and protein (approximately fg/mL) has widespread use in medical diagnostics, monitoring biothreat agents, and in a broader context as a research method. For low-level pathogen, we currently use culture enrichment methods and, thus, rapid analysis is not possible. For low protein concentration, no direct method is currently available. We report here a novel macrocantilever design whose high-order resonant mode near 1 MHz exhibits mass detection sensitivity of 10 cells/mL for cells and 100 fg/mL for protein. The sensor is 1x3 mm and uses a piezoelectric layer for both actuation and sensing resonance. Sample is flowed (approximately 1 mL/min) past the antibody-immobilized sensor, and as antigen binds to the sensor, resonance frequency decreases in proportion to antigen concentration. The sensor showed selectivity to the pathogen even though copious nonpathogenic variant was simultaneously present.

A Method of Measuring Escherichia Coli O157:H7 at 1 Cell/mL in 1 Liter Sample Using Antibody Functionalized Piezoelectric-Excited Millimeter-Sized Cantilever Sensor

Piezoelectric-excited millimeter-sized cantilever (PEMC) sensors immobilized with antibody specific to Escherichia coli (EC) 0157:H7 is used to detect EC at 1 cell/mL in 1 mL and 1 L samples in a batch and flow mode, respectively. Two sensor designs were used. The first design (PEMC-a) has both the piezoelectric and non-piezoelectric layer anchored, while in the second design (PEMC-b) had only the piezoelectric layer anchored. PEMC-a, used in batch mode with 1 mL sample, showed limit of detection at 10 cells/ mL using the second bending mode at 85.5 kHz in air. PEMC-b exhibited resonant frequencies at 186.5, 883.5, and 1778.5 kHz in air and 162.5, 800.0, and 1725.5 kHz in sample flow conditions. A one-liter sample containing 1000 EC cells was introduced at 1.5, 2.5, 3, and 17 ml/min, and the change in resonant frequency was monitored. The total frequency change observed for the mode at 800 kHz and sample flow rates of 1.5, 2.5, 3, and 17 mL/min were 2230+/-11, 3069 +/-47, 4686+/-97, and 7188+/-52 Hz, respectively. Each detection experiment was confirmed by exposing the sensor to a low pH solution followed by a phosphate buffered saline (PBS) rinse, which caused the release of the attached EC. The final frequency change observed was nearly identical to the value prior to EC attachment. Kinetic analysis showed that the observed binding rate constant at 1.5, 2.5, 3 mL/min were 0.009, 0.015, and 0.021 min(-1), respectively. The significance of these results is that very low concentration of pathogens in large sample volumes can be measured in a short time period without the need for filtration or enrichment.

Manufacturing bacteriological contamination outbreaks in industrialized meat production systems: The case of E. coli O157:H7

This article outlines aconceptual framework for examining recentoutbreaks of E. coli O157:H7 infectionassociated with the consumption of beef in theUnited States. We argue that beef produced inthis country is generally safer frombacteriological contamination than in the past.Paradoxically, increasing intensification andconcentration in the meat subsector since theearly 1980s has (a) altered agro-food ecology,including characteristics of foodborne bacteriaand human physiology; (b) created conditionsfavorable for the rapid amplification of lowconcentrations of pathogens; and (c) reducedthe beef industry's flexibility to introducechanges necessary to preclude and/or controlthe rapid spread of pathogens in meat and meatproducts. As a result, beef industry currentlyis capable of producing large quantities ofbacteriologically safe meat whilesimultaneously becoming more vulnerable to foodcontaminations that can be fatal in some cases.The limitations and effectiveness of a newregulatory regime, the HACCP (Hazard Analysisand Critical Control Points) system as well asother efforts to decontaminate the beef supplyare discussed.