One study screened 281 randomly collected clinical specimens and identified 62 for complete detailed analysis of pathogen content. The purpose was to test the accuracy and timing for BACcel™ rapid diagnostic assays intended for use with critically ill patients who acquire serious infections. The BACcel™ system eliminates culturing and analyzes individual live microbial cells directly from a patient specimen. All specimens came from the lower respiratory tract, used to diagnose pneumonia and other severe lung or bronchial infections. Hospital acquired pneumonia is the leading infectious cause of death in ICUs.
The study targeted three major pathogenic bacterial species responsible for infections multi-drug resistance (MDR). Together, these three species account for more than half of hospital acquired MDR infections. They include Staphylococcus aureus (“Staph,” including MRSA), Pseudomonas aeruginosa, and Acinetobacter species. The latter two organisms already have high MDR propensity. But investigators are now finding new strains that recently acquired novel, rapidly-spreading “superbug” KPC genes from entirely unrelated species.
The new ASM study reported that the total time from specimen to results only required 4 hours, instead of the typical 3-day time for cultures using the same specimens. Results included organism counts, identification, and expression of two major resistance types for each one, including MRSA. Identification was correct in 182 of 186 tests, and antibiotic resistance classification in 31 of 32 tests.
The second study characterized Accelr8’s new test for a hidden type of resistance in “Staph.” Not only MRSA, but also the more common type of Staph can effectively resist the standard anti-MRSA antibiotic, vancomycin. With a new type of strain known as hVISA, culturing tests indicate susceptibility to vancomycin, but fails to detect subtle indications of low-level resistance that can lead to treatment failure. Microbiologists refer to this type of cryptic behavior as “heteroresistance.”