Comparison of Staphylococcus aureus isolates associated with food intoxication with isolates from human nasal carriers and human infections

Staphylococcus aureus represents an organism of striking versatility. While asymptomatic nasal colonization is widespread, it can also cause serious infections, toxinoses and life-threatening illnesses in humans and animals. Staphylococcal food poisoning (SFP), one of the most prevalent causes of foodborne intoxication worldwide, results from oral intake of staphylococcal enterotoxins leading to violent vomiting, diarrhea and cramps shortly upon ingestion. The aim of the present study was to compare isolates associated with SFP to isolates collected from cases of human nasal colonization and clinical infections in order to investigate the role of S. aureus colonizing and infecting humans as a possible source of SFP. Spa typing and DNA microarray profiling were used to characterize a total of 120 isolates, comprising 50 isolates collected from the anterior nares of healthy donors, 50 isolates obtained from cases of clinical infections in humans and 20 isolates related to outbreaks of staphylococcal food poisoning. Several common spa types were found among isolates of all three sources (t015, t018, t056, t084). DNA microarray results showed highly similar virulence gene profiles for isolates from all tested sources. These results suggest contamination of foodstuff with S. aureus colonizing and infecting food handlers to represent a source of SF

Comparison of Staphylococcus aureus isolates associated with food intoxication with isolates from human nasal carriers and human infections

Staphylococcus aureus represents an organism of striking versatility. While asymptomatic nasal colonization is widespread, it can also cause serious infections, toxinoses and life-threatening illnesses in humans and animals. Staphylococcal food poisoning (SFP), one of the most prevalent causes of foodborne intoxication worldwide, results from oral intake of staphylococcal enterotoxins leading to violent vomiting, diarrhea and cramps shortly upon ingestion. The aim of the present study was to compare isolates associated with SFP to isolates collected from cases of human nasal colonization and clinical infections in order to investigate the role of S. aureus colonizing and infecting humans as a possible source of SFP. Spa typing and DNA microarray profiling were used to characterize a total of 120 isolates, comprising 50 isolates collected from the anterior nares of healthy donors, 50 isolates obtained from cases of clinical infections in humans and 20 isolates related to outbreaks of staphylococcal food poisoning. Several common spa types were found among isolates of all three sources (t015, t018, t056, t084). DNA microarray results showed highly similar virulence gene profiles for isolates from all tested sources. These results suggest contamination of foodstuff with S. aureus colonizing and infecting food handlers to represent a source of SFP

Order analysis for measurement of Lamb wave propagation distance

The order analysis technique is utilized to directly measure the propagation distance of a Lamb wave without knowing its travel time and group velocity. The proposed algorithm relates the propagating wave-packets to the referenced wave-packet, instead of to an absolute propagating distance. The dispersion signal in the frequency domain is firstly resampled and interpolated according to the unwrapped phase derived from the referenced wave-packet. Subsequently, it is transformed into the angle domain stationary signal. The 'order' is defined as the propagating distance of dispersion wave-packet normalized by that of referenced wave-packet. Then the order spectrum is obtained by the Fourier transform of the equivalent angle signal. Finally, the wave-packet propagation distance is estimated precisely according to the mono-function relationship between the orders and the propagation distances. Synthetic and experimental results show that the proposed method enables the precise propagation distance estimation and mode identification regardless of the phenomenon of dispersion and multi-mode overlapping