The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

High prevalence of gut microbiota colonization with broad-spectrum cephalosporin resistant Enterobacteriaceae in a Tunisian intensive care unit

Healthcare-associated infections due to cefotaxime-resistant Enterobacteriaceae (CRE) have become a major public health threat, especially in intensive care units (ICUs). Often acquired nosocomially, CRE can be introduced initially by patients at admission. This study aimed to determine the prevalence and genetic characteristics of CRE-intestinal carriage in ICU patients, to evaluate the rate of acquisition of these organisms during hospitalization, and to explore some of the associated risk factors for both carriage and acquisition.Between December 2014 and February 2015, the 63 patients admitted in the ICU of Charles Nicolle hospital were screened for rectal CRE colonization at admission and once weekly thereafter to identify acquisition. CRE fecal carriage rate was 20.63% (13/63) at admission and the acquisition rate was 42.85% (15/35). Overall, 35 CRE isolates were collected from 28 patients (25 Klebsiella pneumoniae, 7 Escherichia coli and 3 Enterobacter cloacae strains). Seven patients were simultaneously colonized with 2 CRE isolates. CTX-M-15 was detected in most of the CRE isolates (30/35, 88.23%).Three strains co-produced CMY-4 and 22 strains were carbapenem-resistant and co-produced a carbapenemase OXA-48 (n=13) or NDM-1 (n=6). All isolates were multidrug resistant. Molecular typing of K. pneumoniae strains, revealed 8 Pulsed field gel electrophoresis (PFGE) patterns and 4 sequence types (ST) ST101, ST147, ST429 and ST336. However, E. coli isolates were genetically unrelated and belonged to A (n=2), B1 (n=2) and B2 (n=3) phylogenetic groups and to ST131 (2 strains), ST572 (2 strains), ST615 (one strain) and ST617 (one strain). Five colonized patients were infected by CRE (4 with the same strain identified from their rectal swab and 1 with a different strain). Whether imported or acquired during the stay in the ICU, colonization by CRE is a major risk factor for the occurrence of serious nosocomial infections. Their systematic screening in fecal carriage is mandatory to prevent the spread of these multidrug resistant bacteria