Applications of MALDI-TOF Mass Spectrometry in Clinical Diagnostic Microbiology

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) represents one of the most accurate, reliable, and fast methods for the identification of bacterial strains from positive cultures, and therefore it has largely replaced all other previously used approaches for microbial identification. The main application of MALDI-TOF MS in clinical microbiology laboratories is the identification of bacteria from colonies recovered from solid culture media. This chapter discusses specific identification procedures that are needed for some bacteria, such as Actinomycetes and Mycobacteria. The performance of MALDI-TOF MS identification relies on the number of mass spectra that reach the quality allowing identification and the number of correct identifications. MALDI-TOF MS has also been proposed for Staphylococcus aureus strain typing or for the detection of biomarkers of the most virulent toxigenic isolates. MALDI-TOF MS could also be used for Mycobacterium

Analysis of the costs for the laboratory of flow cytometry screening of urine samples before culture

Urine culture samples comprise a large proportion of the workload in clinical microbiology laboratories, and most of the urine samples show no growth or insignificant growth. A flow cytometry-based analyzer (Sysmex Corporation, Japan) has been used to screen out negative urine samples prior to culture in the Päijät-Häme district. We applied decision analytic modelling to analyze, from a laboratory perspective, the economic feasibility of the screening method as compared to culture only (conventional method) for diagnosis of urinary tract infection. Our model suggests that the least costly analytical strategy is the conventional method. The incremental cost of screening is €0.29/sample. Although laboratory costs are higher, considerable savings on workload can be achieved. Furthermore, screening has numerous benefits on the treatment process of a patient that well warrant the use of the screening method. We conclude that the incremental cost of screening the samples is worth the expense

Secular trend and risk factors for antimicrobial resistance in Escherichia coli isolates in Switzerland 1997-2007

BACKGROUND: : Antibacterial resistance in Escherichia coli isolates of urinary infections, mainly to fluoroquinolones, is emerging. The aim of our study was to identify the secular trend of resistant E. coli isolates and to characterize the population at risk for colonization or infections with these organisms. PATIENTS AND METHODS: : Retrospective analysis of 3,430 E.coli first isolates of urine specimens from patients admitted to the University Hospital Basel in 1997, 2000, 2003, and 2007. RESULTS: : Resistance to ciprofloxacin, trimethoprim/sulfamethoxazole, and amoxicillin/clavulanate has increased over the 10-year study period (from 1.8% to 15.9%, 17.4% to 21.3%, and 9.5% to 14.5%, respectively). A detailed analysis of the 2007 data revealed that independent risk factors for ciprofloxacin resistance were age (5.3% > 35 years of age to 21.9% in patients 0.001) and male gender (OR 1.59, 95% CI 1.05-2.41, p = 0.04). In contrast, nosocomial E. coli isolates were associated with lower odds of ciprofloxacin resistance (OR 0.51, 95% CI 0.28-0.67, p > 0.001). The frequency of resistant isolate rates was not influenced by the clinical significance (i.e., colonization vs urinary tract infection, UTI) or by whether the urine was taken from a urinary catheter. Importantly, the increase in ciprofloxacin resistance paralleled the increase in ciprofloxacin consumption in Switzerland (Pearson's correlation test R(2)= 0.998, p = 0.002). Of note, resistance was less frequent in isolates sent in by general practitioners. However, after adjustment for age and gender, only resistance against amoxicillin/clavulanate was found to be less frequent (OR 0.34, 95% CI 0.16-0.92, p = 0.03). CONCLUSION: : Our study reveals that resistance rates have been increasing during the last decade. Published resistance rates may lack information due to important differences regarding age, gender, and probable origin of the isolates. Empirical therapy for UTI should be guided more on individual risk profile and local resistance data than on resistance data banks