The Role of Breathing in Infection and Immune Defense

Title: Synergistic effect of pressurized carbon dioxide and sodium hypochlorite on the inactivation of Enterococcus sp. in seawater

Authors: Dang TT, Imai T, Le TV, Nguyen DK, Higuchi T, Kanno A, Yamamoto K, Sekine M.

Journal: Water Res. 2016 Dec 1;106:204-213. doi: 10.1016/j.watres.2016.10.003. Epub 2016 Oct 3. PMID: 27721172.

Link to PubMed: Synergistic effect of pressurized carbon dioxide and sodium hypochlorite on the inactivation of Enterococcus sp. in seawater

Abstract: This study investigated the effect of combined treatments using pressurized carbon dioxide (PCD) and sodium hypochlorite (NaOCl) on the inactivation of Enterococcus sp. in artificial seawater. Bacterial inactivation was conducted in a liquid-film-forming apparatus with various pressure conditions, CO2 supply rates, and chlorine dosages. Combined PCD/chlorine treatments resulted in greater disinfection efficiency than those for the two individual treatments. Synergy values were correlated with pressure and CO2 concentrations (p < 0.001). Combination of 0.9 MPa PCD (various CO2 supply rates: 25% CO2 + 75% N2, 50% CO2 + 50% N2, and 100% CO2) and chlorine (0.20 mg L-1) yielded average synergy values of 4.9, 5.2, and 4.4 log, respectively, within 3 min. Combined treatment with PCD (100% CO2, 0.3 MPa, and 20 °C) and chlorine (0.20-0.22 mg L-1) achieved an average synergy value of 4.6 log and complete inactivation (5.2-5.5 log reductions) of Enterococcus sp. within 4 min. In contrast, when the two individual treatments (PCD and chlorine) were used, only 3.7 and 1.8-2.3 log reductions, respectively, were achieved after 25 min. These findings suggest that the combined PCD/chlorine treatment has synergistic benefits and provides a promising method for the disinfection of ballast water.

Title: Antimicrobial Effect of Pressurized Carbon Dioxide on Staphylococcus aureus in Broth and Milk

Authors: Osman Erkmen

Journal: LWT - Food Science and Technology, Volume 30, Issue 8, 1997, Pages 826-829, ISSN 0023-6438, https://doi.org/10.1006/fstl.1997.0277.

Link to ScienceDirect: Antimicrobial Effect of Pressurized Carbon Dioxide on Staphylococcus aureus in Broth and Milk

Abstract: Studies were carried out to assess the use of high pressure CO2 treatment to inhibit Staphylococcus aureus in broth and raw cow's milk at 25 °C. Two phases in the survival curves were observed. The early stage was characterized by a slow rate of decrease in number of S. aureus; this rate increased sharply at the later stage. Staphylococcus aureus suspended in broth was completely inactivated after CO2 treatment at 7 MPa for 100 min and 8 MPa for 60 min. The sterilization effects of CO2 on both S. aureus and aerobic bacteria were observed at 14.6 MPa for 5 h and 9 MPa for 2 h in whole and skim milk, respectively. Staphylococcus aureus and aerobic bacteria were more difficult to inactivate when they were suspended in whole milk that may have protected the cell from penetration by CO2. Reduction rates of S. aureus and aerobic bacteria were sensitive to pressure, exposure time and the suspending medium.

Title: Humidified Warmed CO2 Treatment Therapy Strategies Can Save Lives With Mitigation and Suppression of SARS-CoV-2 Infection: An Evidence Review

Authors: El-Betany AMM, Behiry EM, Gumbleton M, Harding KG.

Journal: Front Med (Lausanne). 2020 Dec 11;7:594295. doi: 10.3389/fmed.2020.594295. PMID: 33425942; PMCID: PMC7793941.

Link to full text: Humidified Warmed CO2 Treatment Therapy Strategies Can Save Lives With Mitigation and Suppression of SARS-CoV-2 Infection: An Evidence Review

Abstract: The coronavirus disease (COVID-19) outbreak has presented enormous challenges for healthcare, societal, and economic systems worldwide. There is an urgent global need for a universal vaccine to cover all SARS-CoV-2 mutant strains to stop the current COVID-19 pandemic and the threat of an inevitable second wave of coronavirus. Carbon dioxide is safe and superior antimicrobial, which suggests it should be effective against coronaviruses and mutants thereof. Depending on the therapeutic regime, CO2 could also ameliorate other COVID-19 symptoms as it has also been reported to have antioxidant, anti-inflammation, anti-cytokine effects, and to stimulate the human immune system. Moreover, CO2 has beneficial effects on respiratory physiology, cardiovascular health, and human nervous systems. This article reviews the rationale of early treatment by inhaling safe doses of warmed humidified CO2 gas, either alone or as a carrier gas to deliver other inhaled drugs may help save lives by suppressing SARS-CoV-2 infections and excessive inflammatory responses. We suggest testing this somewhat counter-intuitive, but low tech and safe intervention for its suitability as a preventive measure and treatment against COVID-19. Overall, development and evaluation of this therapy now may provide a safe and economical tool for use not only during the current pandemic but also for any future outbreaks of respiratory diseases and related conditions.

Title: Virus and bacteria inactivation by CO2 bubbles in solution

Authors: Garrido Sanchis, A., Pashley, R. & Ninham, B.

Journal: npj Clean Water 2, 5 (2019). https://doi.org/10.1038/s41545-018-0027-5

Link to full text: Virus and bacteria inactivation by CO2 bubbles in solution

Abstract: The availability of clean water is a major problem facing the world. In particular, the cost and destruction caused by viruses in water remains an unresolved challenge and poses a major limitation on the use of recycled water. Here, we develop an environmentally friendly technology for sterilising water. The technology bubbles heated un-pressurised carbon dioxide or exhaust gases through wastewater in a bubble column, effectively destroying both bacteria and viruses. The process is extremely cost effective, with no concerning by-products, and has already been successfully scaled-up industrially.

Title: Carbon Dioxide as a Microbial Toxicity Enhancer of Some Antibacterial Agents: A New Potential Water Purification Tool

Authors: Varsik Martirosyan, Karlen Hovnanyan, Sinerik Ayrapetyan

Journal: International Scholarly Research Notices, 22 April 2012, https://doi.org/10.5402/2012/906761

Link to full text: Carbon Dioxide as a Microbial Toxicity Enhancer of Some Antibacterial Agents: A New Potential Water Purification Tool

Abstract: The aim of current paper was to investigate the possibility of increasing the toxicity of calcium hypochlorite (Ca(ClO)2) and hydrogen peroxide (H2O2) on Escherichia coli K-12 by preliminary enrichment of culture media by carbon dioxide (CO2). For this purpose, the microbes sensitivity to H2O2 or/and Ca(ClO)2 at normal and CO2-enriched medium was studied by spectrophotometric, radioisotopic, and electronmicroscopic methods. Ten-minute preincubation in CO2-enriched medium enhanced the toxic effect of both H2O2 or/and Ca(ClO)2 on bacteria as a result of induced growth inhibition, compared to no-CO2 enriched group. Additionally, changes in cell morphology and proliferation were observed. It was demonstrated that the preliminary incubation of microbes in CO2-enriched culture media in no supercritical concentration elevate the toxic effect of H2O2 or/and Ca(ClO)2 on microbes. This can serve as a novel, effective, inexpensive, and environmentally friendly approach for water purification from bacteria, further improving the protection of the environment and human health.

Title: Carbon dioxide inhibits the growth rate of Staphylococcus aureus at body temperature

Authors: Persson M, Svenarud P, Flock JI, van der Linden J.

Journal: Surg Endosc. 2005 Jan;19(1):91-4. doi: 10.1007/s00464-003-9334-z. Epub 2004 Nov 11. PMID: 15529188.

Link to PubMed: Carbon dioxide inhibits the growth rate of Staphylococcus aureus at body temperature

Abstract:
Background: Since the 1930s, carbon dioxide (CO(2)) has been combined with cold storage for the preservation of food. However, its use for the prevention of surgical wound infection was long considered to be impractical. Now CO(2) is widely used during laparoscopic procedures, and a method has been developed to create a CO(2) atmosphere in an open wound. The aim of this study was to investigate the effect of CO(2) on the growth of Staphylococcus aureus at body temperature.

Methods: First, S. aureus inoculated on blood agar were exposed to pure CO(2) (100%), standard anaerobic gas (5% CO(2), 10% hydrogen, 85% nitrogen), or air at 37 degrees C for a period of 24 h; then a viable count of the bacteria was made. Second, S. aureus inoculated in brain-heart infusion broth and kept at 37 degrees C were exposed to CO(2) or air for 0, 2, 4, 6, and 8 h; then the optical density of the bacteria was measured.

Results: After 24 h, the number of S. aureus on blood agar was about 100 times lower in CO(2) than in anaerobic gas (p = 0.001) and about 1,000 times lower than in air (p = 0.001). Also, in broth, there were fewer bacteria with CO(2) than with air (p < 0.01). After 2 h, the number of bacteria was increased with air (p < 0.001) but not with CO(2) (p = 0.13). After 8 h, the optical density had increased from zero to 1.2 with air but it had increased only to 0.01 with CO(2) (p = 0.001).

Conclusion: Pure CO(2) significantly decreased the growth rate of S. aureus at body temperature. The inhibitory effect of CO(2) increased exponentially with time. Its bacteriostatic effect may help to explain the low infection rates in patients who undergo laparoscopic procedures.

Title: Intraoperative CO2 insufflation can decrease the risk of surgical site infection

Authors: Persson M, van der Linden J.

Journal: Med Hypotheses. 2008;71(1):8-13. doi: 10.1016/j.mehy.2007.12.016. Epub 2008 Mar 4. PMID: 18304752.

Link to PubMed: Intraoperative CO2 insufflation can decrease the risk of surgical site infection

Abstract: Surgical wound infections may ruin otherwise successful operations, and are associated with extended hospital stay, extra costs, and high mortality rates. In open surgery the wound's exposure to ambient air increases the risk of wound infection via several independent factors. The open surgical wound is subjected to airborne bacterial contamination, desiccation, and heat loss that increase the bacterial load, cause superficial necrosis, and impair tissue oxygenation and cellular immune functions, respectively. The present hypothesis is that topically applied carbon dioxide in the open surgical wound can be used intraoperatively to avoid these risks, and thus help to prevent postoperative wound infection. We also criticize existing methods and describe the theoretical background and supporting evidence for our suggested method. If the hypothesis would prove to be correct in a clinical trial, the new method may be an effective complement, or even an alternative, to antibiotics in preventing surgical site infection.

Title: Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells

Authors: Foxman EF, Storer JA, Fitzgerald ME, Wasik BR, Hou L, Zhao H, Turner PE, Pyle AM, Iwasaki A.

Journal: Proc Natl Acad Sci U S A. 2015 Jan 20;112(3):827-32. doi: 10.1073/pnas.1411030112. Epub 2015 Jan 5. PMID: 25561542; PMCID: PMC4311828.

Link to full text: Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells

Abstract: Most isolates of human rhinovirus, the common cold virus, replicate more robustly at the cool temperatures found in the nasal cavity (33-35 °C) than at core body temperature (37 °C). To gain insight into the mechanism of temperature-dependent growth, we compared the transcriptional response of primary mouse airway epithelial cells infected with rhinovirus at 33 °C vs. 37 °C. Mouse airway cells infected with mouse-adapted rhinovirus 1B exhibited a striking enrichment in expression of antiviral defense response genes at 37 °C relative to 33 °C, which correlated with significantly higher expression levels of type I and type III IFN genes and IFN-stimulated genes (ISGs) at 37 °C. Temperature-dependent IFN induction in response to rhinovirus was dependent on the MAVS protein, a key signaling adaptor of the RIG-I-like receptors (RLRs). Stimulation of primary airway cells with the synthetic RLR ligand poly I:C led to greater IFN induction at 37 °C relative to 33 °C at early time points poststimulation and to a sustained increase in the induction of ISGs at 37 °C relative to 33 °C. Recombinant type I IFN also stimulated more robust induction of ISGs at 37 °C than at 33 °C. Genetic deficiency of MAVS or the type I IFN receptor in infected airway cells permitted higher levels of viral replication, particularly at 37 °C, and partially rescued the temperature-dependent growth phenotype. These findings demonstrate that in mouse airway cells, rhinovirus replicates preferentially at nasal cavity temperature due, in part, to a less efficient antiviral defense response of infected cells at cool temperature.

Keywords: RIG-I; airway; common cold; innate immunity; rhinovirus.