[Contribution to the early diagnosis of bacteremia: microbial growth detection in liquid culture media by ultrasound].
Nosocomial infection is an important problem because the number of patients daily affected in big hospitals. A big effort exists to develop techniques able to early detect the micro-organisms which cause the infection. The ultrasound is a mechanical radiology technique widely used in Medicine for diagnosis and therapy. It is also well known that this radiation can be used to control relative changes of several physico-chemical parameters in liquids. As an example, the velocity an attenuation of acoustic waves coming through a liquid can be accurately measured. The developed technique consists of an ultrasonic chamber immersed into a thermostatized water bath with two transducers operating in through-transmission. Different culture bottles were placed in between the transducers to live the ultrasound to come across the sample. Several micro-organisms with controlled concentrations, chosen between the most common in sepsis clinical, were used to inoculate each bottle. In the case of aerobic metabolism, the carbon dioxide gas produced by bacteria introduce elastic changes into the liquid which modify both the propagation velocity and the attenuation of the ultrasound. The continuous monitoring of the time-of-flight and the amplitude of an ultrasonic pulse coming through the sample give us a clear indication of the metabolism process. The signatures observed permits the identification of algorithms to early define the positive cases. The developed technique is faster than other commercial systems. The intrinsically non-invasive characteristic of the ultrasound and the relative cheapness of the technique open new attractive possibilities in microbiological diagnosis.
Maestre
J R
JR
Servicio de Microbiología Clínica, Hospital del Aire, Madrid.
Montero de Espinosa
F R
FR
D016470:Bacteremia / Q000175:diagnosis* / Q000382:microbiology; D003428:Cross Infection / Q000175:diagnosis* / Q000382:microbiology; D003470:Culture Media; D004926:Escherichia coli / Q000254:growth & development; D006801:Humans; D014463:Ultrasonography / Q000379:methods*
D003470:Culture Media