remains one of the leading causes of infections worldwide and a common cause of bacteraemia. However, studies documenting the epidemiology of
in South America using genomics are scarce. We hereby ...report on the largest genomic epidemiology study to date of both methicillin-resistant
(MRSA) and methicillin-susceptible
(MSSA) in South America, conducted by the StaphNET-SA network. We characterised 404 genomes recovered from a prospective observational study of
bacteraemia in 58 hospitals from Argentina, Bolivia, Brazil, Paraguay and Uruguay between April and October 2019. We show that a minority of
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
genotypes dominating the MRSA population: CC30-MRSA-IVc-
, CC5-MRSA-IV-
and CC8-MRSA-IVc-
-COMER+. These are historically from a CA origin, carry on average fewer antimicrobial resistance determinants, and often lack key virulence genes. Surprisingly, CC398-MSSA-
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
(largely responsible for the MLSb resistance rates of MSSA strains: inducible iMLSb phenotype) and
(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
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.
Abstract Acute pneumonia caused by Streptococcus pneumoniae is a major cause of child mortality. Antibodies are considered the main effectors of protection in this clinical presentation of ...pneumococcal invasive disease. To get new insights into the mechanisms involved in the protective immunity, we established a murine experimental model of protection against acute pneumococcal pneumonia and then evaluated the transcriptional, humoral and cellular responses in protected and non-protected animals. We found that intranasal inoculation of a sublethal dose of S. pneumoniae serotype 1 conferred complete protection against a subsequent challenge with a lethal dose of the same strain. Sublethal infection elicited a strong IgM and IgG antibody response against the capsular polysaccharide, as assessed one week later, and an exacerbated influx of neutrophils into the lungs immediately after the lethal challenge. Genome-wide microarray-based transcriptional analysis of whole lungs showed 149 differentially expressed genes among which we found upregulation of Il17a , Ifng and several IL-17A- and IFN-γ-related genes in protected versus non-protected mice. Kinetics analysis showed higher expression levels of Il17a in protected animals at all time points whereas Ifng was upregulated early in the protected mice and later in the non-protected animals. Intracelluar cytokine staining demonstrated that CD4+ T cells account for a great proportion of the IL-17A produced in the lungs of protected animals. Overall, these results showed that an upregulation of IL-17A- and a timely regulation of IFN-γ-related gene expression, together with development of a Th17 response, are relevant characteristics of the protective immunity against S. pneumoniae acute pneumonia.
For the last 14 years the Pan American Health Organization has been promoting surveillance of invasive pneumococcal disease in Latin American children for better understanding of the disease ...tendencies regarding capsular types circulation in each country and susceptibility to antimicrobials.
Laboratory-based surveillance data from 10 Latin American countries collected from 2000 to 2005 were analyzed, including serotype distribution and susceptibility to beta-lactam antibiotics.
Although 61 different capsular types were identified during the 6-year surveillance, 13 serotypes accounted for 86% of all isolates. These were consistently the most prevalent throughout the study period with serotype 14 predominating. Diminished susceptibility to penicillin was detected in 38% of all Streptococcus pneumoniae isolates, with the highest prevalence in Dominican Republic and Mexico. Decreased susceptibility to penicillin increased in Brazil and Colombia whereas decreased high resistance rates was recorded in Chile.
These data indicate that 10 countries of the Region continue to have high quality laboratory-based surveillance for pneumococcal disease thus generating valuable information so that healthcare decision makers may prioritize interventions. The heptavalent vaccine will potentially cover from 52.4% to 76.5% of strains causing invasive pneumococcal disease and the 13 valent from 76.7% to 88.3%.
The objective of this study was to characterize the phenotype and genotype of two isolates of rifampicin-resistant Neisseria meningitidis associated with two independent events involving transmission ...of severe meningococcal meningitis that occurred in September and October 2010 in Montevideo, Uruguay. The most recent 10 years of data from the national antimicrobial resistance surveillance system were reviewed to estimate the frequency of the particular meningococcal features that were characterized. Rifampicin resistance was studied using the epsilometer test. The serotype and serosubtype of the isolates were determined by ELISA, and the genotype was characterized using DNA digestion with Nhel and pulse field gel electrophoresis. The two isolates were identical: B:2a:P1.5. In the collection of 408 strains of N. meningitidis isolated in Uruguay in the past 10 years, the phenotype only appeared in two isolates, which were sensitive to rifampicin. The two isolates studied also shared a single pulse type, which was different from that of two other rifampicin-resistant isolates obtained in 2003 and 2007. Consequently, it was concluded that both cases of transmission were caused by a single rifampicin-resistant strain, which could have been an import from another country or else the result of a drift from serogroup C to B due to selective pressure exerted by vaccines administered to the population. It is essential to maintain and maximize surveillance. However, since this type of finding has been sporadic so far, unless a secondary case is identified, there is no justification for changing the antimicrobial drug currently being administered to contacts as prophylaxis.
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