Detection of antibiotic-resistant microorganisms
AssigneeGen-Probe Incorporated
InventorsMichael M. Becker, Kui Gao, Wai-Chung Lam
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Abstract
Method of detecting methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) in a nucleic acid coamplification assay. The invention advantageously reduces the incidence of false-positive MRSA determinations in real-time assays by requiring satisfaction of a threshold criterion that excludes certain co-infections from the MRSA determination. The invention further provides for determination of MSSA, even when the MSSA is present in combination with methicillin-resistant coagulase-negative (MR-CoNS) bacteria at high or low levels.
Claims12
A method of establishing whether a nasal swab sample contains methicillin-sensitive S. aureus bacteria or methicillin-resistant S. aureus bacteria, said method comprising the steps of:
- (a) obtaining nucleic acids from the nasal swab sample;
- (b) coamplifying a S. aureus-specific target sequence and a target sequence specific for methicillin resistance in an in vitro nucleic acid amplification reaction performed using nucleic acids obtained in step (a) as templates,
- wherein each of said target sequences is included among nucleic acids obtained in step (a), and
- wherein amplification products for both of said target sequences are produced and detected in the in vitro nucleic acid amplification reaction;
- (c) determining time-dependent indicia of amplification for the S. aureus-specific target sequence and for the target sequence specific for methicillin resistance that coamplified in step (b);
- (d) calculating a numerical value that is a function of both of said time-dependent indicia of amplification determined in step (c);
- and
- (e) establishing that
- (1) said biological sample contains methicillin-sensitive S. aureus bacteria if the numerical value calculated in step (d) is less than a threshold criterion value that distinguishes the coamplification kinetics of nucleic acids obtained from
- (i) methicillin-resistant S. aureus bacteria, and
- (ii) a mixture of methicillin-sensitive S. aureus bacteria and methicillin-resistant coagulase-negative bacteria, and
- (2) said biological sample contains methicillin-resistant S. aureus bacteria for all values of the numerical value calculated in step (d) that are greater than said threshold criterion value.
Dependencies are inferred from the claim text.