Antibiotic susceptibility tests directly on urine samples using Uro-Quick, a rapid automated system

Coherent fluctuation nephelometry as a promising method for diagnosis of bacteriuria

Objectives

Specialized analyzers are used to automate the diagnosis of bacteriuria in laboratory practice. They are based on analysis of microorganisms concentration in urine samples or recording the growth of urine microflora. Coherent fluctuation nephelometry (CFN) has high sensitivity and allows analyzing both parameters simultaneously. The aim of the study is to compare the effectiveness of CFN-based and flow cytometry based analyzers.

Design and methods

Total 117 urine samples from children were studied in parallel using the CFN-analyzer and UF-1000i (Sysmex), the results were confirmed by conventional microbiological methods.

Results

In 21 urine samples (18%), significant bacteriuria was determined (≥10⁴ CFU/ml). The best diagnostic indicators were obtained while testing urine samples using the CFN-analyzer. The most efficient bacteriuria diagnosis is achieved by simultaneous analyses of microorganisms concentration in urine and growth of urine microflora (sensitivity - 95.2%, specificity - 96.9%, positive predictive value - 87%, negative predictive value - 98.9%, diagnostic odds ratio - 81.7, positive likelihood ratio - 30.5, negative likelihood ratio- 0.049, area under curve in ROC-analysis - 0.987). The CFN-analyzer allows the preliminary selection of negative urine samples, which do not require further analysis by conventional microbiological methods, thereby decreasing the number of cultures by 80.3%.

Conclusions

This study suggests that the CFN-analyzer is the effective tool for bacteriuria screening in children.

Osteomyelitis of the long bones

Long bone osteomyelitis presents a variety of challenges to the physician. The severity of the disease is staged depending upon the infection's particular features, including its etiology, pathogenesis, extent of bone involvement, duration, and host factors particular to the individual patient (infant, child, adult, or immunocompromised). Long bone osteomyelitis may be either hematogenous or caused by a contiguous spread of infection. A single pathogenic organism is almost always recovered from the bone in hematogenous osteomyelitis; Staphylococcus aureus is the most common organism isolated. A variety of multidrug-resistant organisms of bacteria continue to be a source of concern in arresting infection. The primary weapons to treat these infections are culture-specific antibiotics, aggressive debridement, muscle flaps, and bone grafts. This article offers a basic review of the classification, etiology, epidemiology, pathogenesis, and treatment of long bone osteomyelitis.

A biosensor platform for rapid antimicrobial susceptibility testing directly from clinical samples

PURPOSE

A significant barrier to efficient antibiotic management of infection is that the standard diagnostic methodologies do not provide results at the point of care. The delays between sample collection and bacterial culture and antibiotic susceptibility reporting have led to empirical use of antibiotics, contributing to the emergence of drug resistant pathogens. As a key step toward the development of a point of care device for determining the antibiotic susceptibility of urinary tract pathogens, we report on a biosensor based antimicrobial susceptibility test.

MATERIALS AND METHODS

For assay development bacteria were cultured with or without antibiotics, and growth was quantitated by determining viable counts and electrochemical biosensor measurement of bacterial 16S rRNA. To determine antibiotic susceptibility directly from patient samples, urine was cultured on antibiotic plates for 2.5 hours and growth was determined by electrochemical measurement of bacterial 16S rRNA. For assay validation 252 urine samples were collected from patients at the Spinal Cord Injury Service at Veterans Affairs Palo Alto Health Care System. The biosensor based antimicrobial susceptibility test was completed for samples containing gram-negative organisms. Pathogen identification and antibiotic susceptibility results were compared between our assay and standard microbiological analysis.

RESULTS

A direct biosensor quantitation of bacterial 16S rRNA can be used to monitor bacterial growth for a biosensor based antimicrobial susceptibility test. Clinical validation of a biosensor based antimicrobial susceptibility test with patient urine samples demonstrated that this test was 94% accurate in 368 pathogen-antibiotic tests compared to standard microbiological analysis.

CONCLUSIONS

This biosensor based antimicrobial susceptibility test, in concert with our previously described pathogen identification assay, can provide culture and susceptibility information directly from a urine sample within 3.5 hours.

Evaluation of the Uro4 HB&L system for the rapid diagnosis of lower respiratory tract infections in intensive care units

Respiratory tract infection is a common and important problem in the intensive care unit (ICU) setting. It has been demonstrated that an appropriate initial regimen or its early modification (within 6-12h from diagnosis) based on microbiological results leads to a higher survival rate. Here we evaluated the Uro4 HB&L automated system for the rapid diagnosis of respiratory tract infections in ICU patients. A total of 644 lower respiratory tract specimens collected from 400 inpatients from nine ICUs at the Padova University hospital were collected during a 12-month period. All samples were processed both with the Uro4 HB&L system and with the reference culture method. Out of 322 samples, 312 were concordant positive, 276 out of 276 were concordant negative, 66 samples were declared uncertain and discarded because of an excess in turbidity. The diagnostic accuracy was good, compared with standard cultures from BAL specimens, in terms of sensitivity (0.972), specificity (1.00), likelihood ratios and diagnostic odds ratio. Ten discordant samples, resulted positive with the reference culture and not detectable with the Uro4 HB&L, were confirmed positive by Gram-stain smear analysis performed after incubation. The Uro4 HB&L system, compared to the standard culture method, revealed a very high sensitivity and a full specificity in identifying clinically relevant microorganisms from lower respiratory tract samples after merely 6h. Overall our results indicate that Uro4 HB&L is a reliable system for the surveillance of the respiratory tract infections in ICUs; it could speed up the laboratory procedures and provide fast, reliable results for clinicians.