Antimicrobial resistance patterns of Streptococcus uberis isolates from bovine milk in Chiba prefecture, Japan: association between multidrug resistance and clonal complex 996

Streptococcus uberis is one of major pathogens causing bovine mastitis. However, there is poor information on antimicrobial resistance (AMR) among the Japanese isolates. To provide treatment information for the mastitis caused by S. uberis in Japan, we aimed to clarify AMR patterns of the isolates from bovine milk mainly in Chiba. AMR phenotyping/genotyping [blaZ-erm(A)-erm(B)-mef(A)-linB-lnuD-tet(M)-tet(O)-tet(K)-tet(L)-tet(S)] and multilocus sequence typing were performed to analyze relationships between AMR patterns and clonal complexes (CCs). Resistance to tetracycline-, macrolide-, and lincosamide-classes was mainly associated with possession of tet(O), tet(S), erm(B), linB, and lnuD genes. CC996 was significantly associated with multidrug resistance (P<0.0001). These findings will aid Chiba farm animal clinics in treating bovine mastitis.

Review of the Early-Middle Pleistocene boundary and Marine Isotope Stage 19

The Global Boundary Stratotype Section and Point (GSSP) defining the base of the Chibanian Stage and Middle Pleistocene Subseries at the Chiba section, Japan, was ratified on January 17, 2020. Although this completed a process initiated by the International Union for Quaternary Research in 1973, the term Middle Pleistocene had been in use since the 1860s. The Chiba GSSP occurs immediately below the top of Marine Isotope Substage (MIS) 19c and has an astronomical age of 774.1 ka. The Matuyama-Brunhes paleomagnetic reversal has a directional midpoint just 1.1 m above the GSSP and serves as the primary guide to the boundary. This reversal lies within the Early-Middle Pleistocene transition and has long been favoured to mark the base of the Middle Pleistocene. MIS 19 occurs within an interval of low-amplitude orbital eccentricity and was triggered by an obliquity cycle. It spans two insolation peaks resulting from precession minima and has a duration of ~ 28 to 33 kyr. MIS 19c begins ~ 791-787.5 ka, includes full interglacial conditions which lasted for ~ 8-12.5 kyr, and ends with glacial inception at ~ 774-777 ka. This inception has left an array of climatostratigraphic signals close to the Early-Middle Pleistocene boundary. MIS 19b-a contains a series of three or four interstadials often with rectangular-shaped waveforms and marked by abrupt (< 200 year) transitions. Intervening stadials including the inception of glaciation are linked to the calving of ice sheets into the northern North Atlantic and consequent disruption of the Atlantic meridional overturning circulation (AMOC), which by means of the thermal bipolar seesaw caused phase-lagged warming events in the Antarctic. The coherence of stadial-interstadial oscillations during MIS 19b-a across the Asian-Pacific and North Atlantic-Mediterranean realms suggests AMOC-originated shifts in the Intertropical Convergence Zone and pacing by equatorial insolation forcing. Low-latitude monsoon dynamics appear to have amplified responses regionally although high-latitude teleconnections may also have played a role.

Paleoceanography and dinoflagellate cyst stratigraphy across the Lower-Middle Pleistocene Subseries (Calabrian-Chibanian Stage) boundary at the Chiba composite section, Japan

A dinoflagellate cyst record from the highly resolved Chiba composite section in Japan has been used to reconstruct sea-surface paleoceanographic changes across the Lower-Middle Pleistocene Subseries (Calabrian-Chibanian Stage) boundary at the global stratotype, constituting the first detailed study of this microfossil group from the Pleistocene of the Japanese Pacific margin. Cold, subarctic water masses from 794.2 ka gave way to warming and rapid retreat of the Subpolar Front at 789.3 ka, ~ 2000 years before the end of Marine Isotope Stage (MIS) 20. Throughout the fully interglacial conditions of MIS 19c, assemblages are consistent with warm sea surface temperatures but also reveal instability and latitudinal shifts in the Kuroshio Extension system. The abrupt dominance of Protoceratium reticulatum cysts between 772.9 and 770.4 ka (MIS 19b) registers the influence of cooler, mixed, nutrient-rich waters of the Kuroshio-Oyashio Interfrontal Zone resulting from a southward shift of the Kuroshio Extension. Its onset at 772.9 ka serves as a local ecostratigraphic marker for the Chibanian Stage Global Boundary Stratotype Section and Point (GSSP) which occurs just 1.15 m (= 1300 years) below it. An interval from 770.1 ka to the top of the examined succession at 765.8 ka (MIS 19a) represents warm, presumably stratified but still nutrient-elevated surface waters, indicating a northward shift of the Kuroshio Extension ~ 5 kyrs after the termination of full interglacial conditions on land.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s40645-021-00438-3.