Genomic epidemiology of Staphylococcus aureus isolated from bloodstream infections in South America during 2019 supports regional surveillance.

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.

Uso de plantas medicinales en la ciudad de Villaguay, Argentina / Use of medicinal plants in the city of Villaguay, Argentina / Uso de plantas medicinais na cidade de Villaguay, Argentina

El objetivo de este estudio fue determinar la prevalencia del uso de plantas medicinales entre los habitantes de la ciudad de Villaguay. Es un estudio de tipo descriptivo transversal. Se aplicó una encuesta a 381 personas. Se encontró que un 60,9% de los participantes usa plantas medicinales con fines terapéuticos. Se registró un total de 77 especies y 51 usos diferentes. Con respecto a la frecuencia de consumo, un 44,4% las usaban diariamente. El 51,2% de los usuarios de plantas medicinales refirió utilizar simultáneamente medicamentos convencionales, y un 58% de ellos no informó de dicha práctica a su médico. Se encontró que las personas con enfermedades crónicas y de edad de 49,4 ± 6,5 años hacen mayor uso de plantas medicinales. Los profesionales de la salud deben tener en cuenta el considerable porcentaje de usuarios de plantas medicinales presente en la población

The objective of this study was to determine the prevalence of the use of medicinal plants among the inhabitants of the city of Villaguay. It is a descriptive, cross-sectional study. A survey was applied 381 people. It was found that 60.9% of the participants use medicinal plants for therapeutic purposes. A total of 77 species and 51 different uses were recorded. Regarding the frequency of consumption, 44.4% used them daily. The simultaneous use of conventional drugs was reported by 51.2% of the users of medicinal plants, and 58% of them did not report this practice to their doctor. It was found that people with chronic diseases and aged 49.4 ± 6.5 years make greater use of medicinal plants. Health professionals must take into account the remarkable percentage of users of medicinal plants present in the population

O objectivo deste estudo foi determinar a prevalência do uso de plantas medicinais entre os habitantes da cidade de Villaguay. Trata-se de um estudo de tipo descritivo transversal. Aplicou-se um questionário a 381 pessoas. Verificou-se que 90,9% dos participantes usa plantas medicinais com fins terapéuticos. Registou-se um total de 77 espécies e 51 usos diferentes. No que respeita à frequência de consumo, 44,4% usa-as diariamente. O uso simultâneo de medicamentos convencionais foi relatado por 51,2% dos usuários de plantas medicinais e 58% deles não informa o seu médico do consumo de plantas. Observou-se que as pessoas com doenças crónicas e de idade entre 49,4 ± 6,5 são as que mais usam as plantas medicinais. Os profissionais de saúde devem ter em conta a considerável percentagem de consumidores de plantas medicinais na população

Genetic changes associated with tigecycline resistance in Staphylococcus aureus in vitro-selected mutants belonging to different lineages.

Tigecycline (TGC) resistance remains rare in Staphylococcus aureus worldwide. In this study, 12 TGC-resistant S. aureus mutants (TRSAm) were obtained displaying an increase in efflux activity. The isolates belonged to seven different genetic lineages, with a predominance of clonal complex 5 (CC5). Diverse genetic changes in mepA and mepR genes were found producing alterations in the amino acid sequences of the corresponding proteins (MepA and MepR, respectively). The most frequent amino acid change in MepA was Glu287Gly. All of the TRSAm exhibited different single nucleotide polymorphisms (SNPs) or insertions/deletions (InDels) in mepR causing premature stop codons or amino acid changes in MepR. Expression of mepA was significantly increased in TRSAm with different mutations in mepA and mepR. Of the 12 TRSAm, 6 also harboured mutations in rpsJ that resulted in amino acid changes in the S10 ribosomal protein, with Lys57 being the most frequently mutated site. Our findings demonstrate that these acquired mechanisms of TGC resistance are not restricted to a single type of genotypic background and that different lineages might have the same plasticity to develop TGC resistance. The impact of TGC selective pressure assessed by whole-genome sequencing in four selected strain pairs revealed mutations in other singular genes and IS256 mobilisation.

In vitro selection of Staphylococcus aureus mutants resistant to tigecycline with intermediate susceptibility to vancomycin.

BACKGROUND: Tigecycline (TIG) is an antibiotic belonging to the glycylcyclines class and appears to be a good choice to fight infections caused by Staphylococcus aureus. To date, TIG exhibits good activity against this microorganism. The aim of this work was to obtain in vitro mutants of S. aureus resistant to TIG and evaluate possible changes in their susceptibility patterns to other antibiotics. RESULTS: Two mutants of S. aureus resistant to TIG (MIC = 16 µg/mL) were selected in vitro from clinical isolates of methicillin-resistant S. aureus. In both mutants, corresponding to different lineage (ST5 and ST239), an increase of efflux activity against TIG was detected. One mutant also showed a reduced susceptibility to vancomycin, corresponding to the VISA phenotype (MIC = 4 µg/mL), with a loss of functionality of the agr locus. The emergence of the VISA phenotype was accompanied by an increase in oxacillin and cefoxitin MICs. CONCLUSIONS: This study demonstrates that, under selective pressure, the increase of efflux activity in S. aureus is one of the mechanisms that may be involved in the emergence of tigecycline resistance. The emergence of this phenotype may eventually be associated to changes in susceptibility to other antibiotics such oxacillin and vancomycin.

Comparative time-kill study of doxycycline, tigecycline, cefazolin and vancomycin against several clones of Staphylococcus aureus.

BACKGROUND: We present herein, a comparative study assessing the bactericidal kinetics of tigecycline, doxycycline, cefazolin and vancomycin against several methicllin-susceptible (MSSA) and -resistant (MRSA) Staphylococcus aureus isolates recovered from patients of 24 different cities in Argentina. METHODS: After genotypic characterization, 20 strains (10 MRSA and 10 MSSA) were selected for time-kill studies. RESULTS: Vancomycin showed bactericidal effect (i.e. ≥3-log(10) CFU/mL decrease) against 50% and 10% of the MRSA strains at 4 x Minimal Inhibitory Concentration (MIC) and 2xMIC, respectively, after 24 h of incubation and displayed bactericidal activity against all MSSA isolates at 4xMIC. Cefazolin was bactericidal against 30% of MSSA strains at the higher concentration (4xMIC) and against 10% at 2 x MIC and MIC dose concentrations. The bactericidal magnitude of cefazolin observed after 24 h of incubation was lower than the vancomycin one. Albeit bacteriostactic, tigecycline at 2xMIC exerted a -1 to2-log decrease in the viable cell counts after 24-h incubation against 19 of the 20 S. aureus strains. Doxycycline was the least inhibitory of the antibiotics tested against both MRSA and MSSA, displaying no bactericidal activity in any of the cases and showing regrowth after 24 h of incubation at MIC level. CONCLUSION: Vancomycin at high concentrations showed the best activity. Cefazolin did not show the activity expected for a beta-lactam antibiotic against MSSA. Tigecycline may be a useful option in infections caused by MRSA, where bactericidal activity is not an exclusive requirement and doxycycline does not seem an attractive alternative in serious infections.

[Comparative evaluation of the sensitivity of Acinetobacter to colistin, using the prediffusion and minimum inhibitory concentration methods: detection of heteroresistant isolates]. / Sensibilidad de Acinetobacter a la colistina evaluada mediante los métodos de predifusión y de concentración inhibitoria mínima: Detección de aislamientos heterorresistentes.

The objective of this study is to perform a comparative evaluation of the prediffusion and minimum inhibitory concentration (MIC) methods for the detection of sensitivity to colistin, and to detect Acinetobacter baumanii-calcoaceticus complex (ABC) heteroresistant isolates to colistin. We studied 75 isolates of ABC recovered from clinically significant samples obtained from various centers. Sensitivity to colistin was determined by prediffusion as well as by MIC. All the isolates were sensitive to colistin, with MIC = 2µg/ml. The results were analyzed by dispersion graph and linear regression analysis, revealing that the prediffusion method did not correlate with the MIC values for isolates sensitive to colistin (r² = 0.2017). Detection of heteroresistance to colistin was determined by plaque efficiency of all the isolates with the same initial MICs of 2, 1, and 0.5 µg/ml, which resulted in 14 of them with a greater than 8-fold increase in the MIC in some cases. When the sensitivity of these resistant colonies was determined by prediffusion, the resulting dispersion graph and linear regression analysis yielded an r² = 0.604, which revealed a correlation between the methodologies used.

Sensibilidad de Acinetobacter a la colistina evaluada mediante los métodos de predifusión y de concentración inhibitoria mínima: Detección de aislamientos heterorresistentes / Comparative evaluation of the sensitivity of Acinetobacter to colistin, using the prediffusion and minimum inhibitory concentration methods: Detection of heteroresistant isolates

El objetivo de este estudio fue evaluar comparativamente los métodos de predifusión y de concentración inhibitoria mínima para establecer la sensibilidad de aislamientos del complejo Acinetobacter calcoaceticus-baumannii (ABC) a la colistina y detectar a aquellos que presenten heterorresistencia a dicho antibiótico. Se estudiaron 75 aislamientos de ABC recuperados de materiales clínicamente significativos. Se determinó su sensibilidad a la colistina por el método de predifusión y de concentración inhibitoria mínima. Todos los aislamientos resultaron sensibles, con CIM = 2 µg/ml y halos de inhibición en el ensayo de la predifusión = 20 mm. Mediante el método de eficiencia de plaqueo se evaluó la presencia de heterorresistencia a la colistina. Se encontraron 14 aislamientos que originaron colonias heterorresistentes; sus CIM aumentaron en algunos casos en más de 8 veces. Con estas colonias seleccionadas se repitió el ensayo de predifusión. Finalmente se confeccionaron los gráficos de dispersión y se realizaron los análisis de regresión lineal, tanto para el conjunto inicial de todos los aislamientos clínicos como para el subgrupo de los aislamientos resistentes generados durante la evaluación de la heterorresistencia. Se obtuvieron coeficientes de determinación (r²) de 0,2017 y 0,604, respectivamente, lo que indica correlación entre los métodos sólo al evaluar aislamientos preseleccionados por su resistencia a este agente.

The objective of this study is to perform a comparative evaluation of the prediffusion and minimum inhibitory concentration (MIC) methods for the detection of sensitivity to colistin, and to detect Acinetobacter baumanii-calcoaceticus complex (ABC) heteroresistant isolates to colistin. We studied 75 isolates of ABC recovered from clinically significant samples obtained from various centers. Sensitivity to colistin was determined by prediffusion as well as by MIC. All the isolates were sensitive to colistin, with MIC = 2µg/ml. The results were analyzed by dispersion graph and linear regression analysis, revealing that the prediffusion method did not correlate with the MIC values for isolates sensitive to colistin (r² = 0.2017). Detection of heteroresistance to colistin was determined by plaque efficiency of all the isolates with the same initial MICs of 2, 1, and 0.5 µg/ml, which resulted in 14 of them with a greater than 8-fold increase in the MIC in some cases. When the sensitivity of these resistant colonies was determined by prediffusion, the resulting dispersion graph and linear regression analysis yielded an r² = 0.604, which revealed a correlation between the methodologies used.