Rapid detection of bacteria in urine samples by the “three-plug-injection” method using capillary electrophoresis

Sensitive and rapid detection of pathogenic bacteria from urine samples using multiplex recombinase polymerase amplification

Bacterial infections may cause severe diseases such as tuberculosis, sepsis, nephritis and cystitis. The rapid and sensitive detection of bacteria is a prerequisite for the treatment of these diseases. The current gold standard for bacterial identification is bacteriological culture. However, culture-based identification takes 3-7 days, which is time-consuming and laborious. In this study, bacteria in urine samples were enriched using a portable filter-based pipette. Then, a centrifugal chip was constructed to detect multiple pathogenic bacteria from urine samples by integrating the DNA extraction, multiplex recombinase polymerase amplification (RPA) and fluorescent detection together. This eliminated the time-consuming cultivation step, and thus accelerated the diagnosis of the urinary tract infections (UTIs). The five major pathogenic bacteria in UTIs were detected in this study, which are Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhimurium. Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus were successfully detected with limits of detection of 100 CFU mL-1 from urine samples within 40 min. Salmonella typhimurium was successfully detected with a limit of detection of 1000 CFU mL-1 from urine samples. The chip-based bacteria detection proposed in this study is a promising tool for sensitive, accurate, and multiplex identification of bacteria in clinical urine samples of UTIs and bacteriuria.

Capillary electrophoresis based on nucleic acid detection for diagnosing human infectious disease

Rapid transmission, high morbidity, and mortality are the features of human infectious diseases caused by microorganisms, such as bacteria, fungi, and viruses. These diseases may lead within a short period of time to great personal and property losses, especially in regions where sanitation is poor. Thus, rapid diagnoses are vital for the prevention and therapeutic intervention of human infectious diseases. Several conventional methods are often used to diagnose infectious diseases, e.g. methods based on cultures or morphology, or biochemical tests based on metabonomics. Although traditional methods are considered gold standards and are used most frequently, they are laborious, time consuming, and tedious and cannot meet the demand for rapid diagnoses. Disease diagnosis using capillary electrophoresis methods has the advantages of high efficiency, high throughput, and high speed, and coupled with the different nucleic acid detection strategies overcomes the drawbacks of traditional identification methods, precluding many types of false positive and negative results. Therefore, this review focuses on the application of capillary electrophoresis based on nucleic detection to the diagnosis of human infectious diseases, and offers an introduction to the limitations, advantages, and future developments of this approach.

Capillary electrophoresis for fast detection of heterogeneous population in colistin-resistant Gram-negative bacteria

It has been shown that diverse strains of bacteria can be separated according to their characteristic surface properties by means of CE. We employed here this analytical technique to the study of colistin-resistance in Gram-negative bacteria, which involves the selection of mutants with modified outer membrane composition resulting in changes of surface cell properties. In the same way as with molecular entities, we performed firstly the validation of an ITP-based CE method for three common pathogenic Gram-negative bacteria namely Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Secondly, we compared the electrophoretic profiles of bacterial samples from a colistin-susceptible clinical isolate of K. pneumoniae and from the corresponding colistin-resistant derivative. By a simple CE run taking a few minutes, the coexistence of several bacterial subpopulations in the colistin-resistant derivative was clearly evidenced. This work encourages further research that would allow applications of CE in clinical laboratory for a daily monitoring of bacterial population in cared patients when "last-chance" colistin treatment is initiated against multidrug-resistant bacteria.

Rapid, culture-independent, optical diagnostics of centrifugally captured bacteria from urine samples

This work presents a polymeric centrifugal microfluidic platform for the rapid and sensitive identification of bacteria directly from urine, thus eliminating time-consuming cultivation steps. This "Lab-on-a-Disc" platform utilizes the rotationally induced centrifugal field to efficiently capture bacteria directly from suspension within a glass-polymer hybrid chip. Once trapped in an array of small V-shaped structures, the bacteria are readily available for spectroscopic characterization, such as Raman spectroscopic fingerprinting, providing valuable information on the characteristics of the captured bacteria. Utilising fluorescence microscopy, quantification of the bacterial load has been achieved for concentrations above 2 × 10(-7) cells ml(-1) within a 4 μl sample. As a pilot application, we characterize urine samples from patients with urinary tract infections. Following minimal sample preparation, Raman spectra of the bacteria are recorded following centrifugal capture in stopped-flow sedimentation mode. Utilizing advanced analysis algorithms, including extended multiplicative scattering correction, high-quality Raman spectra of different pathogens, such as Escherichia coli or Enterococcus faecalis, are obtained from the analyzed patient samples. The whole procedure, including sample preparation, requires about 1 h to obtain a valuable result, marking a significant reduction in diagnosis time when compared to the 24 h and more typically required for standard microbiological methods. As this cost-efficient centrifugal cartridge can be operated using low-complexity, widely automated instrumentation, while providing valuable bacterial identification in urine samples in a greatly reduced time-period, our opto-microfluidic Lab-on-a-Disc device demonstrates great potential for next-generation patient diagnostics at the of point-of-care.