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Staphylococcus aureus remains one of the leading causes of infections worldwide and a common cause of bacteraemia. However, studies documenting the epidemiology of S. aureus in South America using genomics are scarce. We hereby report on the largest genomic epidemiology study to date of both methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in South America, conducted by the StaphNET-SA network. We characterised 404 genomes recovered from a prospective observational study of S. aureus bacteraemia in 58 hospitals from Argentina, Bolivia, Brazil, Paraguay and Uruguay between April and October 2019. We show that a minority of S. aureus isolates are phenotypically multi-drug resistant (5.2%), but more than a quarter are resistant to macrolide-lincosamide-streptogramin B (MLSb). MSSA were more genetically diverse than MRSA. Lower rates of associated antimicrobial resistance in community-associated(CA)-MRSA versus hospital-associated (HA)-MRSA were found in association with three S. aureus genotypes dominating the MRSA population: CC30-MRSA-IVc- t019-lukS/F-PV+ , CC5-MRSA-IV- t002-lukS/F-PV- and CC8-MRSA-IVc- t008-lukS/F-PV+ -COMER+. These are historically from a CA origin, carry on average fewer antimicrobial resistance determinants, and often lack key virulence genes. Surprisingly, CC398-MSSA- t1451-lukS/F-PV- related to the CC398 human-associated lineage is widely disseminated throughout the region, and is described here for the first time as the most prevalent MSSA lineage in South America. Moreover, CC398 strains carrying ermT (largely responsible for the MLSb resistance rates of MSSA strains: inducible iMLSb phenotype) and sh_fabI (related to triclosan resistance) were recovered from both CA and HA origin. The frequency of MRSA and MSSA lineages differed between countries but the most prevalent S. aureus genotypes are high-risk clones widely distributed in the South American region without a clear country-specific phylogeographical structure. Therefore, our findings underline the need for continuous genomic surveillance by regional networks such as StaphNET-SA. This article contains data hosted by Microreact.

Objective: To assess the effects of dopexamine on splanchnic blood flow and splanchnic oxygen uptake in septic patients., Design: A prospective, controlled trial., Setting: A ten-bed intensive care unit (ICU) in a university hospital., Patients: Twelve patients with severe sepsis (according to the criteria of the 1992 American College of Chest Physicians/Society of Critical Care Medicine consensus conference) being stabilized by volume loading and treated to an elevated oxygen delivery by dobutamine infusion., Interventions: Infusion of increasing dosages of dopexamine (0.5, 1.0, 2.0, and 4.0 microg/kg/min)., Measurements and Main Results: Systemic and splanchnic hemodynamic and oxygen transport parameters as well as gastric mucosal pH (pHi) were measured. A hepatic venous catheter technique with indocyanine green dye dilution was used to determine splanchnic blood flow. Dopexamine increased global and splanchnic oxygen delivery without affecting oxygen consumption (VO2). Splanchnic blood flow increased proportionally to cardiac output, indicating that there was no selective effect of dopexamine on the splanchnic flow. Dopexamine decreased pHi in a dose-dependent fashion in all 12 patients., Conclusions: In hemodynamically stable, hyperdynamic septic patients being treated with dobutamine, dopexamine has no selective effect on splanchnic blood flow. In fact, a decreased pHi suggests a harmful effect on gastric mucosal perfusion.

Objective: To assess global and splanchnic blood flow and oxygen transport in patients with sepsis with and without norepinephrine treatment., Design: Prospective, clinical study., Setting: University hospital intensive care unit., Patients: A convenience sample of 15 septic shock patients treated with norepinephrine and 13 patients with severe sepsis who did not receive norepinephrine., Measurements and Main Results: There were no differences between the two groups in global haemodynamics and oxygen transport. Splanchnic blood flow and oxygen delivery (splanchnic DO2 303 +/- 43 ml/min per m2) and consumption (splanchnic VO2 100 +/- 13 ml/min per m2) were much higher in the septic shock group compared with the severe sepsis group (splanchnic DO2 175 +/- 19 ml/min per m2, splanchnic VO2 61 +/- 6 ml/min per m2). Gastric mucosal pH was subnormal in both groups (septic shock 7.29 +/- 0.02, severe sepsis 7.25 +/- 0.02) with no significant difference. No significant differences between groups were detected in lactate values., Conclusion: These data confirm a redistribution of blood flow to the splanchnic region in sepsis that is even more pronounced in patients with septic shock requiring norepinephrine. However, subnormal gastric mucosal pH suggested inadequate oxygenation in parts of the splanchnic region due to factors other than splanchnic hypoperfusion. Progress in this area will depend on techniques that address not only total splanchnic blood flow, but also inter-organ flow distribution, intra-organ distribution, and other microcirculatory or metabolic malfunctions.