Mucosal Lipocalin 2 Has Pro-Inflammatory and Iron-Sequestering Effects in Response to Bacterial Enterobactin

Nasal colonization by both gram-positive and gram-negative pathogens induces expression of the innate immune protein lipocalin 2 (Lcn2). Lcn2 binds and sequesters the iron-scavenging siderophore enterobactin (Ent), preventing bacterial iron acquisition. In addition, Lcn2 bound to Ent induces release of IL-8 from cultured respiratory cells. As a countermeasure, pathogens of the Enterobacteriaceae family such as Klebsiella pneumoniae produce additional siderophores such as yersiniabactin (Ybt) and contain the iroA locus encoding an Ent glycosylase that prevents Lcn2 binding. Whereas the ability of Lcn2 to sequester iron is well described, the ability of Lcn2 to induce inflammation during infection is unknown. To study each potential effect of Lcn2 on colonization, we exploited K. pneumoniae mutants that are predicted to be susceptible to Lcn2-mediated iron sequestration (iroA ybtS mutant) or inflammation (iroA mutant), or to not interact with Lcn2 (entB mutant). During murine nasal colonization, the iroA ybtS double mutant was inhibited in an Lcn2-dependent manner, indicating that the iroA locus protects against Lcn2-mediated growth inhibition. Since the iroA single mutant was not inhibited, production of Ybt circumvents the iron sequestration effect of Lcn2 binding to Ent. However, colonization with the iroA mutant induced an increased influx of neutrophils compared to the entB mutant. This enhanced neutrophil response to Ent-producing K. pneumoniae was Lcn2-dependent. These findings suggest that Lcn2 has both pro-inflammatory and iron-sequestering effects along the respiratory mucosa in response to bacterial Ent. Therefore, Lcn2 may represent a novel mechanism of sensing microbial metabolism to modulate the host response appropriately

Antibiotic resistance genes in an urban river as impacted by bacterial community and physicochemical parameters

Antibiotic resistance genes (ARGs) in urban rivers are a serious public health concern in regions with poorly planned, rapid development. To gain insights into the predominant factors affecting the fate of ARGs in a highly polluted urban river in eastern China, a total of 285 ARGs, microbial communities, and 20 physicochemical parameters were analyzed for 17 sites. A total of 258 unique ARGs were detected using high-throughput qPCR, and the absolute abundance of total ARGs was positively correlated with total organic carbon and total dissolved nitrogen concentrations (P < 0.01). ARG abundance and diversity were greatly altered by microbial community structure. Variation partitioning analysis showed that the combined effects of multiple factors contributed to the profile and dissemination of ARGs, and variation of microbial communities was the major factor affecting the distribution of ARGs. The disparate distribution of some bacteria, including Bacteroides from mammalian gastrointestinal flora, Burkholderia from zoonotic infectious diseases, and Zoogloea from wastewater treatment, indicates that the urban river was strongly influenced by point-source pollution. Results imply that microbial community shifts caused by changes in water quality may lead to the spread of ARGs, and point-source pollution in urban rivers requires greater attention to control the transfer of ARGs between environmental bacteria and pathogens

Report: Deliverable 2.2.2 Passive transfer of immunity from cows to calves and antibodies in nursing cows’ milk

The transfer of sufficient immunoglobulin G (IgG) to the neonatal calf through colostrum is essential to provide the calf with immunological protection and resistance against disease. Studies on the efficiency of colstrum intake and levels of IgG absorption in calves reared with cow contact are contradictory . On-farm trials were conducted in Switzerland (CH) and France (FR) to test if (1) passive transfer of immunity from cows to calves and (2) if immune (IgG) and antimicrobial (lactoferrin content=LF) parameters in dairy cows’ milk would change by nursing. Calves’ plasma and milk from cows being milked and additionally suckled twice daily for 30 minutes after milking (CH) or between morning and evening milking (FR) was compared to milk from dairy cows only milked. In CH trials IgG content in calf serum did not differ between feeding groups at any observation point, but showed a clear change over time in form of a marked drop followed by an increase again. This was mainly due to the fact that colostrum mangement between suckling and teat bucket fed calves did not differ in these trials. In FR, the IgG concentration in calves’ serum was similar in the different groups and no interaction was observed with the week. The passive immunity transfer was adequate for most calves, except for 3, 2 and 4 calves (out of 14) in groups Control, Dam and Mixed respectively whose plasma IgG concentration was below the threshold of 10 g/L (Besser et al., 1991). The plasma IgG concentration decreased significantly from week 3 to 10 and was significantly higher in female than in male calves. In Swiss trials neither IgG content (mg/L) nor lactoferrin content (LF) in cows' milk differed between feeding regimes. While IgG considerably decreased after 3 weeks, LF content stayed constant, but was more variable in nursing cows. By contrast, in French trials milk IgG was significantly higher in Mixed-cows in week 3, compared to Control and Dam-cows. This finding is very surprising considering that in week 3, all Mixed and Dam cows were suckling their calves. Therefore, differences do not seem to be due to calves’ suckling. Further investigations need to be done in order to try to understand the French results. Also contrary to the Swiss results, milk LF concentration increased steadily from week 3 to 13 and in Week 13. Milk LF was significantly higher in Control cows compared to Dam and Mixed-cows. Again, this result is very surprising and does not seem to be related to calves’ suckling as in week 13, all calves were weaned in all groups. Here again, further investigation needs to be done in order to try to understand this result that could be linked to milk SCC, slightly higher in average in Control cows in week 13