Characterization of a Coliphage AS1 isolated from sewage effluent in Pakistan

The emergence of multi-drug resistant (MDR) bacterial strains, which are posing a global health threat has developed the interest of scientists to use bacteriophages instead of conventional antibiotics therapy. In light of an increased interest in the use of phage as a bacterial control agent, the study aimed to isolate and characterize lytic phages from sewage effluent. During the current study, bacteriophage AS1 was isolated from sewage effluent against E.coli S2. The lytic activity of phageAS1 was limited to E.coli S2 strain showing monovalent behavior. The calculated phage titer was 3.5×109 pfu/ml. PhageAS1 was stable at a wide range of pH and temperature. The maximum stability was recorded at 37ºC and pH 7.0, while showing its normal lytic activity at temperature 60ºC and from pH 5.0 to11.0 respectively. At temperature 70ºC, phage activity was somewhat reduced whereas, further increase in temperature and decrease or increase in pH completely inactivated the phage. From the current study, it was concluded that waste water is a best source for finding bacteriophages against multi-drug resistant bacterial strains and can be used as bacterial control agent.

Uses of Bacteriophages as Bacterial Control Tools and Environmental Safety Indicators

Bacteriophages are bacterial-specific viruses and the most abundant biological form on Earth. Each bacterial species possesses one or multiple bacteriophages and the specificity of infection makes them a promising alternative for bacterial control and environmental safety, as a biotechnological tool against pathogenic bacteria, including those resistant to antibiotics. This application can be either directly into foods and food-related environments as biocontrol agents of biofilm formation. In addition, bacteriophages are used for microbial source-tracking and as fecal indicators. The present review will focus on the uses of bacteriophages like bacterial control tools, environmental safety indicators as well as on their contribution to bacterial control in human, animal, and environmental health.

Eosinophils are part of the granulocyte response in tuberculosis and promote host resistance in mice

Host resistance to Mycobacterium tuberculosis (Mtb) infection requires the activities of multiple leukocyte subsets, yet the roles of the different innate effector cells during tuberculosis are incompletely understood. Here we uncover an unexpected association between eosinophils and Mtb infection. In humans, eosinophils are decreased in the blood but enriched in resected human tuberculosis lung lesions and autopsy granulomas. An influx of eosinophils is also evident in infected zebrafish, mice, and nonhuman primate granulomas, where they are functionally activated and degranulate. Importantly, using complementary genetic models of eosinophil deficiency, we demonstrate that in mice, eosinophils are required for optimal pulmonary bacterial control and host survival after Mtb infection. Collectively, our findings uncover an unexpected recruitment of eosinophils to the infected lung tissue and a protective role for these cells in the control of Mtb infection in mice.

Triggering receptor expressed on myeloid cells-1 (TREM-1) contributes to Bordetella pertussis inflammatory pathology

Whooping cough (pertussis) is a severe pulmonary infectious disease caused by the bacteria Bordetella pertussis . Pertussis infects an estimated 24 million people annually, resulting in >150,000 deaths. The NIH placed pertussis on the list of emerging pathogens in 2015. Antibiotics are ineffective unless administered before the onset of the disease characteristic cough. Therefore, there is an urgent need for novel pertussis therapeutics. We have shown that sphingosine-1-phosphate receptor (S1PR) agonists reduce pertussis inflammation, without increasing bacterial burden. Transcriptomic studies were performed to identify this mechanism and allow for the development of pertussis therapeutics which specifically target problematic inflammation without sacrificing bacterial control. These data suggested a role for triggering receptor expressed on myeloid cells-1 (TREM-1). TREM-1 cell surface receptor functions as an amplifier of inflammatory responses. Expression of TREM-1 is increased in response to bacterial infection of mucosal surfaces. In mice, B. pertussis infection results in TLR9-dependent increased expression of TREM-1 and its associated cytokines. Interestingly, S1PR agonists dampen pulmonary inflammation and TREM-1 expression. Mice challenged intranasally with B. pertussis and treated with ligand-dependent (LP17) and ligand-independent (GF9) TREM-1 inhibitors showed no differences in bacterial burden and significantly reduced TNF-α and CCL-2 expression compared to controls. Mice receiving TREM-1 inhibitors showed reduced pulmonary inflammation compared to controls indicating that TREM-1 promotes inflammatory pathology, but not bacterial control, during pertussis infection. This implicates TREM-1 as a potential therapeutic target for the treatment of pertussis.

Aminoglycosides antagonize bacteriophage proliferation, attenuating phage suppression of bacterial growth, biofilm formation, and antibiotic resistance

The common co-occurrence of antibiotics and phages in both natural and engineered environments underscore the need to understand their interactions and implications for bacterial control and antibiotic resistance propagation. Here, aminoglycoside antibiotics that inhibit protein synthesis (e.g., kanamycin and neomycin) impeded replication of coliphage T3 and Bacillus phage BSP, reducing their infection efficiency and mitigating their hindrance of bacterial growth, biofilm formation and tolerance to antibiotics. For example, treatment with phage T3 reduced subsequent biofilm formation by E. coli liquid cultures to 53 ± 5% of the no-phage control, but a smaller reduction of biofilm formation (89 ± 10%) was observed for combined exposure to phage T3 and kanamycin. Despite sharing a similar mode of action with aminoglycosides (i.e., inhibiting protein synthesis) and antagonizing phage replication –albeit to a lesser degree, tetracyclines did not inhibit phages for bacterial control. Phage T3 combined with tetracycline showed higher suppression of biofilm formation than when combined with aminoglycosides (25 ± 6% of no-phage control). Addition of phage T3 to E. coli suspensions with tetracycline also suppressed the development of tolerance to tetracycline. However, this suppression of antibiotic tolerance development disappeared when tetracycline was replaced with 3 mg/L kanamycin, corroborating greater antagonism with aminoglycosides. Overall, this study highlights this overlooked antagonistic effect on phage proliferation, which may attenuate phage suppression of bacterial growth, biofilm formation, antibiotic tolerance, and maintenance of antibiotic resistance genes. Importance Co-existence of residual antibiotics and phages is common in many environments, which underscores the need to understand their interactive effects on bacteria and the implications for antibiotic resistance propagation. Here, aminoglycosides acting as bacterial protein synthesis inhibitors impeded replication of various phages. This alleviated the suppressive effects of phages against bacterial growth and biofilm formation, and diminished bacterial fitness cost that suppress emergence of tolerance to antibiotics. We show that changes in bacteria caused by environmentally relevant concentrations of sublethal antibiotics can affect phage-host dynamics that are commonly overlooked in vitro, but can result in unexpected environmental consequences.

Refining the Galleria mellonella Model by Using Stress Marker Genes to Assess Clostridioides difficile Infection and Recuperation during Phage Therapy

The Galleria mellonella is an effective model for probing Clostridioides difficile interactions with phages. Despite valuable insights from this model, the larvae are not easily amenable to assessing detailed clinical responses to either bacteria or phages. Here, larval survival, colonisation and toxin levels were compared to expression profiles of 17 G. mellonella stress genes to monitor Clostridiodes difficile infection (CDI), and recuperation during phage therapy. The larvae were infected with a ribotype 014/020 isolate and treated with an optimised phage cocktail. Larvae treated prophylactically with phages and the phage-control larval group were protected, showing the highest survival, and low C. difficile colonisation and toxin rates, compared to co-infection, remedial and bacterial-control larval groups. Expression of growth (9) and reproduction (2) genes were enhanced within prophylaxis and phage-control larval groups compared to the co-infection, remedial and bacterial control groups. In contrast, expression of infection (2), humoral (1) and cellular (3) immunity genes declined in the prophylactic and phage-control groups but increased in the co-infection, remedial and bacterial control larvae. The molecular markers augment the survival, colonisation and toxin data and allow detailed monitoring of CDI and recovery. This data support the use of stress marker genes as tools to analyse clinical symptoms in this model.