Detection of bacteria in blood culture bottles by time-resolved light scattering and absorption measurement

A method for detecting the presence of bacteria in a scattering and/or absorbing sample comprising the steps of:

• introducing modulated electromagnetic radiation into the sample at a first point;
• receiving collected modulated electromagnetic radiation at a second point;
• determining a time-averaged intensity of the collected modulated electromagnetic radiation over time;
• determining a phase of the collected modulated electromagnetic radiation relative to the introduced modulated electromagnetic radiation;
• determining a phase shift of the collected modulated electromagnetic radiation relative to the introduced modulated electromagnetic radiation;
• comparing the determined phase shift of the collected modulated electromagnetic radiation with a phase shift measured at a prior time to detect the presence of bacteria;
• and
• indicating that bacteria are present in the sample if the determined phase shift is significantly different than the phase shift measured at the prior time.

A method for detecting the presence of bacteria in a scattering and/or absorbing sample comprising the steps of:

• introducing modulated electromagnetic radiation into the sample at a first point;
• determining a modulation degree of the modulated electromagnetic radiation reemerging at a second point;
• comparing the determined modulation degree with a modulation degree measured at a prior time to detect the presence of bacteria;
• and
• indicating that bacteria are present if the determined modulation degree is significantly different that the modulation degree measured at the prior time.

A method for detecting the presence of bacteria in a scattering and/or absorbing sample comprising the steps of:

• introducing modulated electromagnetic radiation into a sample at a first point at an initial time;
• receiving collected modulated electromagnetic radiation at a second point located across the sample from the first point;
• determining a time-averaged intensity of the collected modulated electromagnetic radiation over time;
• determining an amplitude of the collected modulated electromagnetic radiation relative to the introduced electromagnetic radiation;
• determining a modulation degree of the collected modulated electromagnetic radiation;
• repeating the steps or receiving collected modulated electromagnetic radiation, determining the time-averaged intensity, determining the amplitude and determining the modulation degree of the collected modulated electromagnetic radiation;
• comparing the modulation degree measured at the initial time and at subsequent times to detect the presence of bacteria;
• and
• indicating that bacteria are present if the modulation degree of the sample measured at subsequent times is significantly different than the modulation degree measured at the initial time.

Apparatus for detecting the presence of bacteria in a scattering and/or absorbing sample comprising:

• means for introducing modulated electromagnetic radiation into the sample at a first point;
• detector means for receiving collected modulated electromagnetic radiation at a second point;
• processing means for determining a time-averaged intensity value for the collected modulated electromagnetic radiation over time;
• means for determining a modulation degree of the collected modulated electromagnetic radiation;
• means for comparing the determined modulation degree of the collected modulated electromagnetic radiation with a control modulation degree measured at a previous time to detect the presence of bacteria;
• and
• means for indicating that bacteria are present in the determined modulation degree of the collected modulated electromagnetic radiation is significantly different from the control modulation degree measured at the previous time.

Apparatus for detecting the presence of bacteria in a scattering and/or absorbing sample comprising:

• means for introducing modulated electromagnetic radiation into the sample at a first point;
• detector means for receiving collected modulated electromagnetic radiation at a second point;
• means for determining a modulation degree of the collected modulated electromagnetic radiation;
• means for comparing the determined modulation degree with a control modulation degree determined from a control sample known to be free of bacteria to detect the presence of bacteria;
• and
• means for indicating that bacteria if the determined modulation degree of the collected modulated electromagnetic radiation is significantly different from the control modulation degree of the control sample.

Apparatus for detecting the presence of bacteria in a scattering and/or absorbing sample comprising:

• means for introducing modulated electromagnetic radiation into the sample at a first point;
• detector means for receiving collected modulated electromagnetic radiation at a second point;
• means for determining a phase shift of the collected modulated electromagnetic radiation;
• means for comparing the determined phase shift with a control phase shift determined from a control sample known to be free of bacteria to detect the presence of bacteria;
• and
• means for indicating that bacteria are present if the determined phase shift of the collected modulated electromagnetic radiation is significantly different from the control phase shift of the control sample.