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SAN DIEGO – , according to a detailed study of six isolates.
“Both patient and microbe factors can contribute to treatment failure, even involving pan-susceptible isolates,” Andrew Berti, PharmD, PhD, said in an interview prior to an annual scientific meeting on infectious diseases.
The researchers presented the case of a patient who experienced multiple episodes of breakthrough Staphylococcus aureus bacteremia over a period of 5 years in the setting of appropriately dosed antimicrobial suppressive therapy. They recovered six clinical bloodstream isolates from the patient during distinct episodes of methicillin-susceptible S. aureus (MSSA) bacteremia, and it was determined that a central line infection was the source for each episode. Isolates recovered were susceptible to the individual therapies received, which included oxacillin, daptomycin, and dalbavancin. The researchers used Illumina technology to collect bacterial whole genome sequence data. “Relatively little is known about bacterial evolution during human infection as these tend to be acute, rapidly resolved events,” Dr. Berti said. “This case was unique in that we could observe changes to a pathogen over a more than 6 years period as it adapted to survive host defenses and multiple antibiotic interventions.”
The researchers discovered that the first two isolates (ST256) and the last four isolates (ST5) “represent distinct populations and suggest that a distinct MSSA strain displaced the previous population between bacteremia episodes 2 and 3,” they wrote in their abstract. “Of note, all of these strains were able to survive and establish breakthrough bacteremias despite favorable susceptibility profiles to the agents used as suppressive therapy. Although the MICs remain low and in the susceptible range to oxacillin, daptomycin, and dalbavancin, these isolates progressively developed significant antimicrobial tolerance phenotypes, which coincided with mutations in walK (yycG), htrA2, ftsW, ebh, and ileS that may be advantageous to survival under antibiotic pressure.”
Dr. Berti acknowledged certain limitations of the analysis, including the inability to test for heteroresistance to some antibiotics, which may also contribute to treatment failure. “Specific therapeutic interventions that coincide with bacterial population changes are not necessarily causative of those changes,” he said. One of the study authors, Warren Rose, PharmD, disclosed having received research grants, speaker honoraria, and/or consulting fees from Theravance, Merck, The Medicines Company and Visante, Inc. All other authors reported having no financial disclosures.
SAN DIEGO – , according to a detailed study of six isolates.
“Both patient and microbe factors can contribute to treatment failure, even involving pan-susceptible isolates,” Andrew Berti, PharmD, PhD, said in an interview prior to an annual scientific meeting on infectious diseases.
The researchers presented the case of a patient who experienced multiple episodes of breakthrough Staphylococcus aureus bacteremia over a period of 5 years in the setting of appropriately dosed antimicrobial suppressive therapy. They recovered six clinical bloodstream isolates from the patient during distinct episodes of methicillin-susceptible S. aureus (MSSA) bacteremia, and it was determined that a central line infection was the source for each episode. Isolates recovered were susceptible to the individual therapies received, which included oxacillin, daptomycin, and dalbavancin. The researchers used Illumina technology to collect bacterial whole genome sequence data. “Relatively little is known about bacterial evolution during human infection as these tend to be acute, rapidly resolved events,” Dr. Berti said. “This case was unique in that we could observe changes to a pathogen over a more than 6 years period as it adapted to survive host defenses and multiple antibiotic interventions.”
The researchers discovered that the first two isolates (ST256) and the last four isolates (ST5) “represent distinct populations and suggest that a distinct MSSA strain displaced the previous population between bacteremia episodes 2 and 3,” they wrote in their abstract. “Of note, all of these strains were able to survive and establish breakthrough bacteremias despite favorable susceptibility profiles to the agents used as suppressive therapy. Although the MICs remain low and in the susceptible range to oxacillin, daptomycin, and dalbavancin, these isolates progressively developed significant antimicrobial tolerance phenotypes, which coincided with mutations in walK (yycG), htrA2, ftsW, ebh, and ileS that may be advantageous to survival under antibiotic pressure.”
Dr. Berti acknowledged certain limitations of the analysis, including the inability to test for heteroresistance to some antibiotics, which may also contribute to treatment failure. “Specific therapeutic interventions that coincide with bacterial population changes are not necessarily causative of those changes,” he said. One of the study authors, Warren Rose, PharmD, disclosed having received research grants, speaker honoraria, and/or consulting fees from Theravance, Merck, The Medicines Company and Visante, Inc. All other authors reported having no financial disclosures.
SAN DIEGO – , according to a detailed study of six isolates.
“Both patient and microbe factors can contribute to treatment failure, even involving pan-susceptible isolates,” Andrew Berti, PharmD, PhD, said in an interview prior to an annual scientific meeting on infectious diseases.
The researchers presented the case of a patient who experienced multiple episodes of breakthrough Staphylococcus aureus bacteremia over a period of 5 years in the setting of appropriately dosed antimicrobial suppressive therapy. They recovered six clinical bloodstream isolates from the patient during distinct episodes of methicillin-susceptible S. aureus (MSSA) bacteremia, and it was determined that a central line infection was the source for each episode. Isolates recovered were susceptible to the individual therapies received, which included oxacillin, daptomycin, and dalbavancin. The researchers used Illumina technology to collect bacterial whole genome sequence data. “Relatively little is known about bacterial evolution during human infection as these tend to be acute, rapidly resolved events,” Dr. Berti said. “This case was unique in that we could observe changes to a pathogen over a more than 6 years period as it adapted to survive host defenses and multiple antibiotic interventions.”
The researchers discovered that the first two isolates (ST256) and the last four isolates (ST5) “represent distinct populations and suggest that a distinct MSSA strain displaced the previous population between bacteremia episodes 2 and 3,” they wrote in their abstract. “Of note, all of these strains were able to survive and establish breakthrough bacteremias despite favorable susceptibility profiles to the agents used as suppressive therapy. Although the MICs remain low and in the susceptible range to oxacillin, daptomycin, and dalbavancin, these isolates progressively developed significant antimicrobial tolerance phenotypes, which coincided with mutations in walK (yycG), htrA2, ftsW, ebh, and ileS that may be advantageous to survival under antibiotic pressure.”
Dr. Berti acknowledged certain limitations of the analysis, including the inability to test for heteroresistance to some antibiotics, which may also contribute to treatment failure. “Specific therapeutic interventions that coincide with bacterial population changes are not necessarily causative of those changes,” he said. One of the study authors, Warren Rose, PharmD, disclosed having received research grants, speaker honoraria, and/or consulting fees from Theravance, Merck, The Medicines Company and Visante, Inc. All other authors reported having no financial disclosures.
REPORTING FROM ID WEEK 2017
Key clinical point: Both patient and microbe factors can contribute to antibitoic treatment failure.
Major finding: Two distinct Staphylococcus aureus lineages were islolated over a period of 5 years, and each was able to persist despite appropriate antibitoic interventions.
Study details: Clinical analysis of six bloodstream isolates from a singles patient over a 5-year period.
Disclosures: One of the study authors, Warren Rose, PharmD, disclosed having received research grants, speaker honoraria and/or consulting fees from Theravance, Merck, The Medicines Company and Visante. All other authors reported having no financial disclosures.