Methicillin-Susceptible ST398 Staphylococcus aureus Responsible for Bloodstream Infections: An Emerging Human-Adapted Subclone?

In the course of an annual 3-month bloodstream infections (BSI) survey conducted during a four-year period in 31 healthcare institutions located in three noncontiguous French regions, we report 18 ST398 Staphylococcus aureus BSI. ST398 BSI incidence showed a seven-fold increase during the study period (0.002 per 1,000 patient days in 2007 vs. 0.014 in 2010). ST398 BSI isolates differed from the pig-borne multiresistant clone: 17/18 BSI isolates were methicillin susceptible and none was of t011, t034 or t108 pig-borne spa-types. ST398 BSI isolates had homogenous resistance patterns (15/18 with only Eryr) and prophagic content (all harboured the hlb-converting Sau3int phage). The clustering of BSI and pig-borne isolates by spa-typing and MLVA, the occurrence of Sau3int phage in BSI isolates and the lack of this phage in pig-borne isolates suggest that the emergence of BSI isolates could have arisen from horizontal transfer, at least of the Sau3int phage, in genetically diverse MSSA ST398 isolates. The acquisition of the phage likely plays a role in the increasing ability of the lysogenic ST398 isolates to colonize human. The mode of acquisition of the non pig-borne ST398 isolates by our 18 patients remains unclear. ST398 BSI were diagnosed in patients lacking livestock exposure and were significantly associated with digestive portals of entry (3/18 [16.7%] for ST398 vs. 19/767 [2.5%] for non ST398 BSI; p = .012). This raises the question of possible foodborne human infections. We suggest the need for active surveillance to study and control the spread of this human-adapted subclone increasingly isolated in the hospital setting

Emergence of unusual bloodstream infections associated with pig-borne-like Staphylococcus aureus ST398 in France

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Multicentre external quality control evaluating universal 16S polymerase chain reaction (PCR) in the diagnosis of bone and joint infections

International audienceObjectives:During a multicentrer French Study performed to assess the contribution of 16S PCR in the diagnosis of prosthesis osteoarticular infections, 300 patients were included from December 2009 to April 2012. An external quality control (QC) was considered essential due to the diversity of molecular equipment for each laboratory. Three sets were held, for each including 4 bacterial DNA extracts (E) and 4 crushed osteoarticular deep samples.Methods:Extraction: 0,2 ml of pretreated S (PK, 37 °C, 3h) with elution in 0.1 ml. Four laboratories used Qiagen manual extraction and 3 others used automated extraction 1 MagnaPur Roche, 1 Easy Mag, BioMérieux and 1 iPrep, Invitrogen. Real time 16S PCR with SybrGreen was performed with degenerate primers amplifying 658pb followed by sequencing. In the 7 centers, PCR thermocyclers used were 2 MX 3000p Agilent, 1 Roche Light Cycler, 1 Abi 7900 and 1 Applied Step one plus, 1 Smartcycler Cepheid,1 Biorad Chrono 4 and for PCR premix, Takara premix exTaq, Applied, Promega and Biorad were used.Results: 168 QC were sent and 160 responses were analyzed (1 laboratory did not participate in the first QC series). Expected results were obtained in 97.5% for Extracts and 95% for Samples. Sensitivity and Specificity were 100 and 90% for E and 93.3 and 100% for S. Ct standard deviations (SD) for E were from 1 to 9 while SD was 2 to 7 for S. For centers using the same premix, the results were closer, SD 0.5 to 1.5 (3 Ct gap max). For S, no influence of extraction system was observed.Conclusion:If extraction system had no influence, premix seems to be the most important factor influencing the value of threshold. This QC demonstrates the possibility to obtain good and homogeneous results by using the same 16S PCR in laboratories with different equipments for molecular bone and joint infection diagnosis

Dissemination of Methicillin-Susceptible CC398 Staphylococcus aureus Strains in a Rural Greek Area

A large collection of Staphylococcus aureus including a. 745 clinically significant isolates that were consecutively recovered from human infections during 2012-2013, b. 19 methicillin- susceptible (MSSA), randomly selected between 2006-2011 from our Staphylococcal Collection, c. 16 human colonizing isolates, and d. 10 strains from colonized animals was investigated for the presence and the molecular characteristics of CC398. The study was conducted in Thessaly, a rural region in Greece. The differentiation of livestock-associated clade from the human clade was based on canSNPs combined with the presence of the phi 3 bacteriophage and the tetM, scn, sak, and chp genes. Among the 745 isolates, two MRSA (0.8% of total MRSA) and thirteen MSSA (2.65% of total MSSA) were found to belong to CC398, while, between MSSA of our Staphylococcal Collection, one CC398, isolated in 2010, was detected. One human individual, without prior contact with animals, was found to be colonized by a MSSA CC398. No CC398 was identified among the 10 S. aureus isolated from animals. Based on the molecular markers, the 17 CC398 strains were equally placed in the livestock-associated and in the human clades. This is the first report for the dissemination of S. aureus CC398 among humans in Greece