A cooperativity between virus and bacteria during respiratory infections

Respiratory tract infections remain the leading cause of morbidity and mortality worldwide. The burden is further increased by polymicrobial infection or viral and bacterial co-infection, often exacerbating the existing condition. Way back in 1918, high morbidity due to secondary pneumonia caused by bacterial infection was known, and a similar phenomenon was observed during the recent COVID-19 pandemic in which secondary bacterial infection worsens the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) condition. It has been observed that viruses paved the way for subsequent bacterial infection; similarly, bacteria have also been found to aid in viral infection. Viruses elevate bacterial infection by impairing the host’s immune response, disrupting epithelial barrier integrity, expression of surface receptors and adhesion proteins, direct binding of virus to bacteria, altering nutritional immunity, and effecting the bacterial biofilm. Similarly, the bacteria enhance viral infection by altering the host’s immune response, up-regulation of adhesion proteins, and activation of viral proteins. During co-infection, respiratory bacterial and viral pathogens were found to adapt and co-exist in the airways of their survival and to benefit from each other, i.e., there is a cooperative existence between the two. This review comprehensively reviews the mechanisms involved in the synergistic/cooperativity relationship between viruses and bacteria and their interaction in clinically relevant respiratory infections

Interaction of bacteria and inhalable particulate matter in respiratory infectious diseases caused by bacteria

Air pollution is a major global health issue and a significant risk factor for respiratory infections. Air pollution containing inhalable particulate matter (PM), including Diesel Exhaust Particles (DEP), Urban Particles (UP), tobacco smoke particles, dust particles, ambient Black Carbon (BC), household smoke, etc., emitted from vehicles, industry, construction, agriculture waste burning, cooking, etc., exerts a negative effect on human health. The exposure of inhalable PM to the upper airways, often colonized by opportunistic microbes, represents a unique risk for respiratory infections. Several epidemiological studies reported that PM exposure increases susceptibility to, and severity of, lower respiratory infections like pneumonia or other important diseases such as otitis media, asthma, lung cancer, cardiovascular disease, and Chronic Obstructive Pulmonary disease (COPD). It has been suggested that inhalable PM exposure damages airway epithelial cells, alters the immune response, affects the microbiota, and, as a result, opportunist or pathogenic bacteria (Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, Pseudomonas aeruginosa, or Staphylococcus aureus) establishes respiratory infections. PM and bacteria interaction alters bacteria physiology and enhances bacterial proliferation and biofilm mode of growth. However, the exact mechanism pertaining to how the PM reverts the opportunistic bacteria of the nasopharynx to a pathogenic state is not well understood. In the present review, we have focused on understanding the airborne PM and bacteria interaction that makes humans more susceptible to otherwise harmless bacteria, especially those in the upper airways. Further, we have provided an overview of potential mechanisms triggered by air pollutants to induce bacterial infectious diseases

Table_1_Revisiting the role of cyanobacteria-derived metabolites as antimicrobial agent: A 21st century perspective.DOCX

Cyanobacterial species are ancient photodiazotrophs prevalent in freshwater bodies and a natural reservoir of many metabolites (low to high molecular weight) such as non-ribosomal peptides, polyketides, ribosomal peptides, alkaloids, cyanotoxins, and isoprenoids with a well-established bioactivity potential. These metabolites enable cyanobacterial survival in extreme environments such as high salinity, heavy metals, cold, UV-B, etc. Recently, these metabolites are gaining the attention of researchers across the globe because of their tremendous applications as antimicrobial agents. Many reports claim the antimicrobial nature of these metabolites; unfortunately, the mode of action of such metabolites is not well understood and/or known limited. Henceforth, this review focuses on the properties and potential application, also critically highlighting the possible mechanism of action of these metabolites to offer further translational research. The review also aims to provide a comprehensive insight into current gaps in research on cyanobacterial biology as antimicrobials and hopes to shed light on the importance of continuing research on cyanobacteria metabolites in the search for novel antimicrobials.</p