Faten El Sayed1, Samo Jeverica2, Anne-Laure Roux3, Thomas Bauer4, Lionelle Nkam5, Valérie Sivadon-Tardy6, Latifa Noussair7, Jean-Louis Herrmann8, Jean-Louis Gaillard3, Mitja Rak2, Lea Papst9, Martin Rottman8. 1. APHP, GHU Paris Saclay, Hôpital Ambroise Paré, Microbiology Department, Boulogne-Billancourt, France; Université Paris-Saclay, UVSQ, Inserm, Infection et Inflammation, Montigny-Le-Bretonneux, France. Electronic address: faten.elsayed@aphp.fr. 2. National Laboratory of Health, Environment and Food, Maribor, Slovenia. 3. APHP, GHU Paris Saclay, Hôpital Ambroise Paré, Microbiology Department, Boulogne-Billancourt, France; Université Paris-Saclay, UVSQ, Inserm, Infection et Inflammation, Montigny-Le-Bretonneux, France. 4. APHP, GHU Paris Saclay, Hôpital Ambroise Paré, Orthopedic Surgery Department, Boulogne-Billancourt, France. 5. Clinical Research Unit, APHP Paris Saclay Ouest, Ambroise Paré Hospital, Boulogne-Billancourt, France. 6. APHP, GHU Paris Saclay, Hôpital Ambroise Paré, Microbiology Department, Boulogne-Billancourt, France. 7. APHP, GHU Paris Saclay, Hôpital Raymond Poincaré, Microbiology Department, Garches, France. 8. Université Paris-Saclay, UVSQ, Inserm, Infection et Inflammation, Montigny-Le-Bretonneux, France; APHP, GHU Paris Saclay, Hôpital Raymond Poincaré, Microbiology Department, Garches, France. 9. Department of Infectious Diseases, University Medical Centre Ljubljana, Ljubljana, Slovenia.
Abstract
OBJECTIVES: Blood culture bottles (BCBs) are commonly used for the diagnosis of infections associated with orthopedic devices. Although Cutibacterium acnes is an important pathogen in orthopedics, relatively little is known about its growth characteristics in BCBs. This prompted us to analyze the influence of bacterial genotype and clinical significance on time-to-detection (TTD) in BCBs. METHODS: We reviewed 59 cases of orthopedic device-related infections in which at least one intraoperative specimen yielded a pure C. acnes culture from anaerobic BCBs (BD Bactec Lytic/10 Anaerobic/F; Lytic-Ana) and/or solid media. A strain was considered infectant if the same genotype was present in two or more intraoperative samples. From these cases, we isolated a total of 72 unique C. acnes strains belonging to four multilocus sequence type clonal complexes (CCs): CC18, CC28, CC36 and CC53. Growth rate and TTD in Lytic-Ana BCB were studied under experimental conditions (inoculation of standard inoculum) and in clinical samples (inoculation of periprosthetic tissue samples). RESULTS: Median TTD values were shorter for CC53 compared to other CCs under experimental conditions (69 vs. 103 h; p < 0.001) and from clinical specimens (70 vs. 200 h; p = 0.02). Infectant strains had a shorter median TTD compared to contaminant strains in a clinical situation, while the difference was not observed under experimental conditions. CONCLUSIONS: The detection dynamics of C. acnes in Lytic-Ana BCBs were associated with genotype. Thus, TTD not only reflects the bacterial load in clinical samples, but may also reflect the intrinsic properties of the clonal complex of C. acnes.
OBJECTIVES: Blood culture bottles (BCBs) are commonly used for the diagnosis of infections associated with orthopedic devices. Although Cutibacterium acnes is an important pathogen in orthopedics, relatively little is known about its growth characteristics in BCBs. This prompted us to analyze the influence of bacterial genotype and clinical significance on time-to-detection (TTD) in BCBs. METHODS: We reviewed 59 cases of orthopedic device-related infections in which at least one intraoperative specimen yielded a pure C. acnes culture from anaerobic BCBs (BD Bactec Lytic/10 Anaerobic/F; Lytic-Ana) and/or solid media. A strain was considered infectant if the same genotype was present in two or more intraoperative samples. From these cases, we isolated a total of 72 unique C. acnes strains belonging to four multilocus sequence type clonal complexes (CCs): CC18, CC28, CC36 and CC53. Growth rate and TTD in Lytic-Ana BCB were studied under experimental conditions (inoculation of standard inoculum) and in clinical samples (inoculation of periprosthetic tissue samples). RESULTS: Median TTD values were shorter for CC53 compared to other CCs under experimental conditions (69 vs. 103 h; p < 0.001) and from clinical specimens (70 vs. 200 h; p = 0.02). Infectant strains had a shorter median TTD compared to contaminant strains in a clinical situation, while the difference was not observed under experimental conditions. CONCLUSIONS: The detection dynamics of C. acnes in Lytic-Ana BCBs were associated with genotype. Thus, TTD not only reflects the bacterial load in clinical samples, but may also reflect the intrinsic properties of the clonal complex of C. acnes.