Mapping the coverage, availability and uptake of External Quality Assessment programmes across One Health sectors in Asia.

INTRODUCTION: Establishing effective external quality assessment (EQA) programmes is an important element in ensuring the quality of, and building capacity for, antimicrobial resistance (AMR) laboratory surveillance. OBJECTIVES: To understand the current coverage of, and challenges to participation in, EQAs in National Reference Laboratories (NRLs) across One Health (OH) sectors in Asia. METHODS: Current EQA coverage was evaluated through desktop review, online surveys and interviews of both EQA participants and providers. EQA coverage was mapped and summarized by laboratory type and 'readiness' level and identified challenges evaluated qualitatively. RESULTS: Of the 31 identified NRLs [16 Human Health (HH) and 15 Animal/Food Safety laboratories (A/FS)], 14 HH and 7 A/FS laboratories currently participated in international EQA schemes and several participated in two or more different schemes. Seven laboratories were currently not participating in any EQA scheme and two of these (one HH and one A/FS) do not currently perform microbiology; six HH NRLs provided national EQAs. Of the eight surveyed international EQA providers, three were based in Asia and all offered varying programmes in terms of pathogens, frequency and support mechanisms for reporting and follow-up. Only one provider currently served laboratories across all OH sectors. CONCLUSIONS: The current coverage of EQA programmes for AMR in Asia was heterogeneous across countries but especially across OH sectors. This updated overview of the coverage and challenges associated with participation in, and provision of, EQAs for AMR suggest the benefit and relevance of introducing one comprehensive and high-quality EQA programme across OH sectors in Asia.

Chitinase Expression in Listeria monocytogenes Is Influenced by lmo0327, Which Encodes an Internalin-Like Protein.

The chitinolytic system of Listeria monocytogenes thus far comprises two chitinases, ChiA and ChiB, and a lytic polysaccharide monooxygenase, Lmo2467. The role of the system in the bacterium appears to be pleiotropic, as besides mediating the hydrolysis of chitin, the second most ubiquitous carbohydrate in nature, the chitinases have been deemed important for the colonization of unicellular molds, as well as mammalian hosts. To identify additional components of the chitinolytic system, we screened a transposon mutant library for mutants exhibiting impaired chitin hydrolysis. The screening yielded a mutant with a transposon insertion in a locus corresponding to lmo0327 of the EGD-e strain. lmo0327 encodes a large (1,349 amino acids [aa]) cell wall-associated protein that has been proposed to possess murein hydrolase activity. The single inactivation of lmo0327, as well as of lmo0325 that codes for a putative transcriptional regulator functionally related to lmo0327, led to an almost complete abolishment of chitinolytic activity. The effect could be traced at the transcriptional level, as both chiA and chiB transcripts were dramatically decreased in the lmo0327 mutant. In accordance with that, we could barely detect ChiA and ChiB in the culture supernatants of the mutant strain. Our results provide new information regarding the function of the lmo0325-lmo0327 locus in L. monocytogenes and link it to the expression of chitinolytic activity.IMPORTANCE Many bacteria from terrestrial and marine environments express chitinase activities enabling them to utilize chitin as the sole source of carbon and nitrogen. Interestingly, several bacterial chitinases may also be involved in host pathogenesis. For example, in the important foodborne pathogen Listeria monocytogenes, the chitinases ChiA and ChiB and the lytic polysaccharide monooxygenase Lmo2467 are implicated in chitin assimilation but also act as virulence factors during the infection of mammalian hosts. Therefore, it is important to identify their regulators and induction cues to understand how the different roles of the chitinolytic system are controlled and mediated. Here, we provide evidence for the importance of lmo0327 and lmo0325, encoding a putative internalin/autolysin and a putative transcriptional activator, respectively, in the efficient expression of chitinase activity in L. monocytogenes and thereby provide new information regarding the function of the lmo0325-lmo0327 locus.

Quorum sensing signals are produced by Aeromonas salmonicida and quorum sensing inhibitors can reduce production of a potential virulence factor.

Many pathogens control production of virulence factors by self-produced signals in a process called quorum sensing (QS). We demonstrate that acyl homoserine lactone (AHL) signals, which enable bacteria to express certain phenotypes in relation to cell density, are produced by a wide spectrum of Aeromonas salmonicida strains. All 31 typical strains were AHL producers as were 21 of 26 atypical strains, but on a strain population basis, production of virulence factors such as protease, lipase, A-layer or pigment did not correlate with the production and accumulation of AHLs in the growth medium. Pigment production was only observed in broth under highly aerated conditions. Quorum sensing inhibitors (QSIs) are compounds that specifically block QS systems without affecting bacterial growth and 2 such compounds, sulphur-containing AHL-analogues, reduced production of protease in a typical strain of Aeromonas salmonicida. The most efficient compound N-(heptylsulfanylacetyl)-L-homoserine lactone (HepS-AHL), reduced protease production by a factor of 10. Five extracellular proteases were detected on gelatin-containing sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) gels and 3 of these were completely down regulated by HepS-AHL. Hence, QSIs can curb virulence in some strains and could potentially be pursued as bacterial disease control measures in aquaculture.