Search

Background Cooling towers are a major source of large community-associated outbreaks of Legionnaires’ disease, a severe pneumonia. This disease is contracted when inhaling aerosols that are contaminated with bacteria from the genus Legionella, most importantly Legionella pneumophila. How cooling towers support the growth of this bacterium is still not well understood. As Legionella species are intracellular parasites of protozoa, it is assumed that protozoan community in cooling towers play an important role in Legionella ecology and outbreaks. However, the exact mechanism of how the eukaryotic community contributes to Legionella ecology is still unclear. Therefore, we used 18S rRNA gene amplicon sequencing to characterize the eukaryotic communities of 18 different cooling towers. The data from the eukaryotic community was then analysed with the bacterial community of the same towers in order to understand how each community could affect Legionella spp. ecology in cooling towers. Results We identified several microbial groups in the cooling tower ecosystem associated with Legionella spp. that suggest the presence of a microbial loop in these systems. Dissolved organic carbon was shown to be a major factor in shaping the eukaryotic community and may be an important factor for Legionella ecology. Network analysis, based on co-occurrence, revealed that Legionella was correlated with a number of different organisms. Out of these, the bacterial genus Brevundimonas and the ciliate class Oligohymenophorea were shown, through in vitro experiments, to stimulate the growth of L. pneumophila through direct and indirect mechanisms. Conclusion Our results suggest that Legionella ecology depends on the host community, including ciliates and on several groups of organisms that contribute to its survival and growth in the cooling tower ecosystem. These findings further support the idea that some cooling tower microbiomes may promote the survival and growth of Legionella better than others.

Legionella pneumophila is a natural inhabitant of water systems. From there, it can be transmitted to humans by aerosolization resulting in severe pneumonia. Most large outbreaks are caused by cooling towers colonized with L. pneumophila. The resident microbiota of the cooling tower is a key determinant for the colonization and growth of L. pneumophila. In our preceding study, the genus Pseudomonas correlated negatively with the presence of L. pneumophila in cooling towers, but it was not clear which species was responsible. Therefore, we identified the Pseudomonas species inhabiting 14 cooling towers using a Pseudomonas-specific 16S rRNA amplicon sequencing strategy. We found that cooling towers that are free of L. pneumophila contained a high relative abundance of members from the Pseudomonas alcaliphila/oleovorans phylogenetic cluster. P. alcaliphila JCM 10630 inhibited the growth of L. pneumophila on agar plates. Analysis of the P. alcaliphila genome revealed the presence of a gene cluster predicted to produce toxoflavin. L. pneumophila growth was inhibited by pure toxoflavin and by extracts from P. alcaliphila culture found to contain toxoflavin by liquid chromatography coupled with mass spectrometry. In addition, toxoflavin inhibits the growth of Vermameoba vermiformis, a host cell of L. pneumophila. Our study indicates that P. alcaliphila may be important to restrict growth of L. pneumophila in water systems through the production of toxoflavin. A sufficiently high concentration of toxoflavin is likely not achieved in the bulk water but might have a local inhibitory effect such as near or in biofilms.

Background: In India, tobacco consumption is responsible for one of the highest rates of oral cancer in the world, the annual oral cancer incidence is steadily increasing among young tobacco users. Studies have documented efforts taken by physicians, doctors and even dentists, in the form of individual or group counseling to curb tobacco use in smoke or smokeless form. However, which one is more effective, still remains an unanswered question. The aim of the study was to compare the effectiveness of individual and group counseling for cessation of the tobacco habit amongst industrial workers in Pune and to compare quit rates. Materials and methods: An interventional study design was selected for 150 industrial workers which were stratified randomly into three groups (control, individual and group counseling groups) and interventions were provided to individual and group counseling groups over a period of six months, which were then compared with the control group that received brief intervention at the start of the study. Results: There was significant difference in the quit rates of the participants in the individual counseling group (ICG) and group counseling group (GCG) when compared at 6 months with the control counseling group (CCG). In the individual counseling group was 6% while in group counseling group it was 7.5% after six months of counseling. Conclusions: No conclusion could be drawn whether individual or group counseling were better interms of quit rates. Individual and group counseling groups were definitely better than the control group when compared at 3 and 6 months, respectively.

Electronic cigarettes (EC), a proxy to conventional cigarettes, gained popularity on the basis of its own advocacy, marketing and large scale publicity. Sometimes marketed as an adjunct to quitting or a substitute for cigarettes, its popularity rose. However, its sale in the global markets was subjected to prejudice. Reasons cited by the regulatory bodies for its ouster were the toxic contents it contained. Some countries preferred to ban them while some have legalised them. However, the manufacturers have claimed that it does have the potential to help smokers quit or at least replace the conventional cigarettes which cause millions of death globally. Research is hence needed to prove the efficacy and utility of this device for welfare of people who are looking for better options than puffing cigarettes.