Streptococcus uberis is one of the most frequent mastitis-causing pathogens isolated from dairy cows. Further understanding of S. uberis genetics may help elucidate the disease pathogenesis. We compared the genomes of S. uberis isolates cultured from dairy cows located in distinctly different geographic regions of Australia. All isolates had novel multi locus sequence types (MLST) indicating a highly diverse population of S. uberis. Global clonal complexes (GCC) were more conserved. GCC ST86 and GCC ST143 represented 30% of the total isolates (n = 27) and were clustered within different geographic regions. Core genome phylogeny revealed low phylogenetic clustering by region, isolation source, and MLST. Identification of putative sortase (srtA) substrates and generation of a custom putative virulence factor database revealed genes which may explain the affinity of S. uberis for mammary tissue, evasion of antimicrobial efforts and disease pathogenesis. Of 27 isolates, four contained antibiotic resistance genes including an antimicrobial resistance cluster containing mel/mef(A), mrsE, vatD, lnuD, and transposon-mediated lnuC was also identified. These are novel genes for S. uberis, which suggests interspecies lateral gene transfer. The presence of resistance genes across the two geographic regions tested within one country supports the need for a careful, tailored, implementation and monitoring of antimicrobial stewardship.

To examine the relation between increased newborn oxygen requirements and the postnatal rise in cardiac output, we measured left ventricular (LV) output, organ blood flows, and whole-body oxygen consumption using radioactive microspheres in late-gestation sheep fetuses and in the same animals 1 and 4 hours after cesarean section delivery. LV output rose from 264±23 ml * min`-kg body wt-' in fetuses to 444±33 ml * min`. kg body wt-' in lambs at 1 hour after delivery (p<0.005) and was unchanged at 4 hours after delivery. This rise in LV output was associated with a more than fourfold increase in the LV flow contribution to tissues situated distal to the ductus arteriosus (fetus, 51+9 ml * min`-kg body wt-V; lamb, 226+22 ml * min`-* kg body wt-V; p<0.005), which were mainly perfused by the right ventricle in utero. However, average blood flow to body tissues was similar in fetuses (37+4 ml * min`-100 g tissue-'), 1-hour lambs (39+4 ml * min`. 100 g tissue-'), and 4-hour lambs (40±5 ml * min`' 100 g tissue-').Oxygen consumption increased by 58%, from 7.84±0.43 ml * min-kg body wt-' in fetuses to 12.38+2.4 ml * min`kg body wt-F in 1-hour lambs (p<0.01), and was unchanged in 4-hour lambs. Although systemic blood flow did not change after birth, the arteriovenous oxygen content difference increased by 54%, from 1.98±0.16 ml/dl in fetuses to 3.05+±0.19 ml/dl in 1-hour lambs (p<0.005), and was unaltered in 4-hour lambs. We conclude that 1) an increased LV output after birth results from the LV taking over the perfusion of tissues supplied by the right ventricle in utero, 2) the perinatal rise in LV output maintains overall systemic perfusion, 3) an increased newborn oxygen consumption is achieved through a rise in arteriovenous oxygen extraction, and 4) rises in oxygen consumption and LV output at birth are not directly related to one another. (Circulation Research 1992;71:443-450) KEY WORDS * fetus * newborn * cardiac microspheres L eft ventricular (LV) output1'2 and whole-body oxygen consumption3'4 both increase substantially with birth. It is tempting to assume that these changes are closely related to one another,2 especially in view of the parallel reductions in oxygen consumption and LV output that occur during subsequent postnatal growth.5'6 This assumption, however, overlooks the complexity of the circulatory events associated with birth. Specifically, an increased LV output after birth could result from three factors. First, LV output might increase because of a net postnatal rise in organ blood flows.2 Second, because systemic blood flow is derived from both ventricles in the fetus7-9 but only from the LV in the newborn,28 LV output might increase after birth to compensate for loss of the fetal right ventricular (RV) contribution to systemic perfusion. Third, left to right shunting across an incompletely constricted ductus arteriosus in the early postnatal period might also augment LV output.

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Teat disinfection is a common pre-and post-milking mastitis prevention practice that is part of a mastitis control program in dairy herds. Commercially available teat disinfectants are generally chemical-based products. The use of these products has occasionally raised concerns about the risk of chemical residues in milk. An alternative treatment or prevention strategy based on probiotics has the potential to circumvent this risk. Two treatments were compared in a cross-over clinical trial in a single herd: a lactobacillus-based, post-milking teat spray (LACT), and a commercial iodine-based post-milking teat disinfectant product as (positive control, PC). The effect of the two treatments on cow somatic cell counts was quantified using a multivariate mixed-effects linear regression model with cow fitted as a random effect. The odds of teat end scores increasing from a low to a high score tended to be lower (OR = 0.74, 95% CI 0.54-1.01, P = 0.06) for cows receiving LACT treatment. On average, there was also a tendency for a lower somatic cell counts in the LACT treated cows (antilog of coefficient = 0.91, 95% CI 0.80-1.03, P = 0.13) compared with the PC treated cows. The application of the lactobacillus-based product to teats could reduce the rate of teat end scores progression from low to higher scores, and potentially improve teat end sphincter functions and udder health. Further, larger scale validation work is required to support the findings of the current study.