Heterogeneous fitness landscape cues, pknG low expression, and phthiocerol dimycocerosate low production of Mycobacterium tuberculosis ATCC25618 rpoB S450L in enriched broth

Extrapulmonary and Drug-Resistant Childhood Tuberculosis: Unveiling the Disease to Adopt the Optimal Treatment Strategy

Paediatric tuberculosis (TB) is a substantial threat among infectious diseases, particularly considering the high risk of extrapulmonary tuberculosis (EPTB), severe forms of the disease, and the spreading of drug-resistant strains. Describing the characteristics of children with EPTB and those with drug-resistant tuberculosis (DR-TB) and analysing the role of second-line drugs could facilitate the management of these cases. This retrospective study was conducted on 271 children diagnosed with active TB disease (44 EPTB cases, 9 DR-TB cases), originating from diverse geographic areas, who were referred to the infectious disease unit at Meyer Children's Hospital, Florence, Italy, from 2006 to 2022. In most patients, the management of therapies was complicated by the impossibility to obtain drug susceptibility testing (DST) results, which improved over the years: 17/154 (11.04%) children had DST results between 2006 and 2013, and 50/117 (42.73%, p < 0.001) between 2014 and 2022. Second-line drugs were not exclusively administered to DR-TB cases, but also to EPTB cases (20/44, 45.45%). Drugs were generally well tolerated; adverse events occurred in 13 children (13/271, 4.80%) and were generally mild and reversable. Therapies were successful in 267 children (98.52%) considered cured, while 4 (1.48%) presented sequelae. Both univariate and multivariate logistic regression analyses were conducted to investigate factors associated with EPTB, DR-TB, and second-line drugs administration. Originating from Asia emerged as a risk factor associated with both EPTB and DR-TB (p = 0.013 and p = 0.045, respectively). The introduction of GeneXpert tests has significantly improved TB diagnosis and the obtaining of DST results. The administration of second-line therapies should be limited primarily to DR-TB cases, but it is possible that these drugs may also be beneficial in selected EPTB cases.

Staphylococcus aureus Modulates Carotenoid and Phospholipid Content in Response to Oxygen-Restricted Growth Conditions, Triggering Changes in Membrane Biophysical Properties

Staphylococcus aureus membranes contain carotenoids formed during the biosynthesis of staphyloxanthin. These carotenoids are considered virulence factors due to their activity as scavengers of reactive oxygen species and as inhibitors of antimicrobial peptides. Here, we show that the growth of S. aureus under oxygen-restricting conditions downregulates carotenoid biosynthesis and modifies phospholipid content in biofilms and planktonic cells analyzed using LC-MS. At oxygen-restrictive levels, the staphyloxanthin precursor 4,4-diapophytofluene accumulates, indicating that the dehydrogenation reaction catalyzed by 4,4'-diapophytoene desaturases (CrtN) is inhibited. An increase in lysyl-phosphatidylglycerol is observed under oxygen-restrictive conditions in planktonic cells, and high levels of cardiolipin are detected in biofilms compared to planktonic cells. Under oxygen-restriction conditions, the biophysical parameters of S. aureus membranes show an increase in lipid headgroup spacing, as measured with Laurdan GP, and decreased bilayer core order, as measured with DPH anisotropy. An increase in the liquid-crystalline to gel phase melting temperature, as measured with FTIR, is also observed. S. aureus membranes are therefore less condensed under oxygen-restriction conditions at 37 °C. However, the lack of carotenoids leads to a highly ordered gel phase at low temperatures, around 15 °C. Carotenoids are therefore likely to be low in S. aureus found in tissues with low oxygen levels, such as abscesses, leading to altered membrane biophysical properties.