SARS-CoV-2 across Africa: The impact of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been hard to track in African countries, largely because of patchy data. Wilkinson et al . curated viral genomes collected in 2021 from several countries across the continent. Outbreaks during 2020 in each African country were initiated by imported cases, mostly from Europe. As the pandemic developed, case numbers in African countries were likely many times higher than reported, and subsequent waves of the pandemic appear to have been more severe. Consequently, high-transmission variants have emerged that have spread within the continent, and African countries must be included in global control efforts. —CA

Despite a slight decline since 2014, tuberculosis (TB) remains the major deadly infectious disease worldwide with about 1.5 million deaths each year and with about one-third of the population being latently infected with Mycobacterium tuberculosis, the etiologic agent of TB. During primo-infection, the recruitment of immune cells leads to the formation of highly organized granulomas. Among the different cells, one outstanding subpopulation is the foamy macrophage (FM), characterized by the abundance of triacylglycerol-rich lipid bodies (LB). M. tuberculosis can reside in FM, where it acquires, from host LB, the neutral lipids which are subsequently processed and stored by the bacilli in the form of intracytosolic lipid inclusions (ILI). Although host LB can be viewed as a reservoir of nutrients for the pathogen during latency, the molecular mechanisms whereby intraphagosomal mycobacteria interact with LB and assimilate the LB-derived lipids are only beginning to be understood. Past studies have emphasized that these physiological processes are critical to the M. tuberculosis infectious-life cycle, for propagation of the infection, establishment of the dormancy state and reactivation of the disease. In recent years, several animal and cellular models have been developed with the aim of dissecting these complex processes and of determining the nature and contribution of their key players. Herein, we review some of the in vitro and in vivo models which allowed to gain significant insight into lipid accumulation and consumption in M. tuberculosis, two important events that are directly linked to pathogenicity, granuloma formation/maintenance and survival of the tubercle bacillus under non-replicative conditions. We also discuss the advantages and limitations of each model, hoping that this will serve as a guide for future investigations dedicated to persistence and innovative therapeutic approaches against TB.

The coronary artery disease is a chronic inflammatory disease involving genetic as well as environmental factors. Recent evidence suggests that the oral microbiome has a significant role in triggering atherosclerosis. The present study assessed the oral microbiome composition variation between coronary patients and healthy subjects in order to identify a potential pathogenic signature associated with coronary artery disease (CAD). We performed metagenomic profiling of salivary microbiomes by 16S rRNA next-generation sequencing. Oral microbiota profiling was performed for 30 individuals including 20 patients with CAD and 10 healthy individuals without carotid plaques or previous stroke or myocardial infarction.We found that oral microbial communities in patients and healthy controls are represented by similar global core oral microbiome. The predominant taxa belonged to Firmicutes (genus Streptococcus, Veillonella, Granulicatella, Selenomonas), Proteobacteria (genus Neisseria, Haemophilus), Actinobacteria (genus Rothia), Bacteroidetes (genus Prevotella, Porphyromonas) and Fusobacteria (genus Fusobacterium, Leptotrichia). More than 60% relative abundance of each sample for both CAD patients and controls is represented by three major genera including Streptococcus (24.97% and 26.33%), Veillonella (21.43% and 19.91%) and Neisseria (14.23% and 15.33%). Using penalized regression analysis, the bacterial genus Eikenella was involved as the major discriminant genus for both status and Syntax score of CAD. We also reported a significant negative correlation between Syntax score and Eikenella abundance in coronary patients’ group (Spearman rho =-0.68, p= 0.00094). In conclusion, the abundance of Eikenella in oral coronary patient samples compared to controls could be a prominent pathological indicator for the development of CAD.

Smooth tubercle bacilli (STB) including ‘‘Mycobacterium canettii’’ are members of the Mycobacterium tuberculosis complex (MTBC) which cause non-contagious tuberculosis in human. This group comprises less than one hundred isolates characterized by smooth colonies and cordless organisms. Most STB isolates have been obtained from patients exposed to the Republic of Djibouti but seven isolates, including the three seminal ones obtained by Georges Canetti between 1968 and 1970, were recovered from patients in France, Madagascar, Sub-Sahara East Africa and French Polynesia. STB form a genetically heterogeneous group of MTBC organisms with large 4.48 ± 0.05 Mb genomes which may link Mycobacterium kansasii to MTBC organisms. Lack of inter-human transmission suggested a yet unknown environmental reservoir. Clinical data indicate a respiratory tract route of contamination and the digestive tract as an alternative route of contamination. Further epidemiological and clinical studies are warranted to elucidate areas of uncertainty regarding these unusual mycobacteria and the tuberculosis they cause.

Adipose tissues were shown to host Mycobacterium tuberculosis which is persisting inside mature adipocytes. It remains unknown whether this holds true for Mycobacterium canettii, a rare representative of the M. tuberculosis complex responsible for lymphatic and pulmonary tuberculosis. Here, we infected primary murine white and brown pre-adipocytes and murine 3T3-L1 pre-adipocytes and mature adipocytes with M. canettii and M. tuberculosis as a positive control. Both mycobacteria were able to infect 18–22% of challenged primary murine pre-adipocytes; and to replicate within these cells during a 7-day experiment with the intracellular inoculums being significantly higher in brown than in white pre-adipocytes for M. canettii (p = 0.02) and M. tuberculosis (p = 0.03). Further in-vitro infection of 3T3-L1 mature adipocytes yielded 9% of infected cells by M. canettii and 17% of infected cells by M. tuberculosis (p = 0.001). Interestingly, M. canettii replicated and accumulated intra-cytosolic lipid inclusions within mature adipocytes over a 12-day experiment; while M. tuberculosis stopped replicating at day 3 post-infection. These results indicate that brown pre-adipocytes could be one of the potential targets for M. tuberculosis complex mycobacteria; and illustrate differential outcome of M. tuberculosis complex mycobacteria into adipose tissues. While white adipose tissue is an unlikely sanctuary for M. canettii, it is still an open question whether M. canettii and M. tuberculosis could persist in brown adipose tissues.

Mycobacterium canettii , which has a smooth colony morphology, is the tuberculous organism retaining the most genetic traits from the putative last common ancestor of the rough-morphology Mycobacterium tuberculosis complex. To explore whether M. canettii can infect individuals by the oral route, mice were fed phosphate-buffered saline or 10 ⁶ M. canettii mycobacteria and sacrificed over a 28-day experiment. While no M. canettii was detected in negative controls, M. canettii -infected mice yielded granuloma-like lesions for 4/4 lungs at days 14 and 28 postinoculation (p.i.) and positive PCR detection of M. canettii for 5/8 mesenteric lymph nodes at days 1 and 3 p.i. and 5/6 pooled stools collected from day 1 to day 28 p.i. Smooth M. canettii colonies grew from 68% of lungs and 36% of spleens and cervical lymph nodes but fewer than 20% of axillary lymph nodes, livers, brown fat samples, kidneys, or blood samples throughout the 28-day experiment. Ready translocation in mice after digestive tract challenge demonstrates the potential of ingested M. canettii organisms to relocate to distant organs and lungs. The demonstration of this relocation supports the possibility that populations may be infected by environmental M. canettii .