Role of verocytotoxigenic Escherichia coli in cattle and buffalo calf diarrhoea

Abstract 273 Strains of Escherichia coli isolated from diarrhoeic and healthy control cattle and buffalo calves in Sri Lanka, were tested for Verocytotoxin (VT) and for heat-stable (ST) and heat-labile (LT) enterotoxins. VT and ST toxigenic E. coli were significantly associated with diarrhoea, accounting for 28% and 18% of diarrhoeic episodes, respectively. LT toxigenic E. coli were not significantly associated with diarrhoea.     

血清脑钠肽、超敏C反应蛋白、可溶性ST2对阵发性心房颤动患者射频消融术后复发的预测价值研究

摘要 目的：探讨血清脑钠肽（BNP）、超敏C反应蛋白（hs-CRP）、可溶性致瘤抑制素2（sST2）对阵发性心房颤动（AF）患者射频消融（RFA）术后复发的预测价值。方法：选择2016年1月至2020年12月我院收治的接受RFA术治疗的82例阵发性AF患者,术后随访12个月,根据术后是否复发分为复发组（25例）和未复发组（57例）。检测患者血清BNP、hs-CRP、sST2水平,收集临床相关资料,采用多因素Logistic回归模型分析影响阵发性AF患者RFA术后复发的因素,采用受试者工作特征（ROC）曲线分析血清BNP、hs-CRP、sST2预测阵发性AF患者RFA术后复发的价值。结果：复发组血清BNP、hs-CRP、sST2水平高于未复发组（P＜0.05）。血清BNP、hs-CRP、sST2水平升高、AF病程增长是影响阵发性AF患者RFA术后复发的危险因素（P＜0.05）。血清BNP、hs-CRP、sST2预测阵发性AF患者消融术后复发的曲线下面积分别为0.720、0.694、0.718,联合三者预测阵发性AF患者RFA术后复发的曲线下面积为0.866,高于BNP、hs-CRP、sST2单独预测。结论：阵发性AF患者血清BNP、hs-CRP、sST2水平升高是RFA术后复发的危险因素,联合检测血清BNP、hs-CRP、sST2水平有助于预测阵发性AF患者RFA术后复发。     

FITC-labeled lectins and calcofluor white ST as probes for the investigation of the molecular architecture of cell surfaces. Studies on conjugatophycean species

Summary In a screening program with 7 FITC-labeled lectins as probes, ConA receptors were identified in all of the 28 members of theConjugatophyceae, being under investigation. In nearly all of them RCA₁₂₀ receptors, too, are expressed. In 3 species only, PNA receptors, and in 2 species UEA receptors have been detected. No binding of DBA, SBA, and WGA was observed. The receptors for ConA, RCA₁₂₀, and UEA were shown to be associated with different molecules. Each lectin exhibits a unique and specific binding pattern, both chemically, as well as with regard to the topographic distribution on cell surfaces. While ConA receptors predominantly are associated with constituents of the cell wall, RCA₁₂₀ receptors mostly form part of the surrounding mucilage; the same holds for UEA receptors. Besides a variability of topographic distribution and species-to-species variation, a cell-to-cell variation exists in many species, suggesting that the expression of a lectin receptor is due to the developmental state of the cell and/or depends on external stimuli. In conclusion, we may point out, that FITC-labeled lectins turned out to be extremely useful probes for the investigation of the molecular architecture of cell walls. Calcofluor white ST binding to fibrillar polysaccharides (most probably cellulose) was shown to be inhibited by external incrustations of the cell wall. One species does not show any reaction with calcofluor white ST at all.     

Ultrastructure of retrocerebral complex of the earwig, Euborellia annulipes, and rôle of aorta as a neurohaemal organ

The ultrastructure of the retrocerebral endocrine-aortal complex of the earwig, Euborellia annulipes has been studied. The space between the inner and outer stromal layers of the aorta is occupied by numerous axon terminals and pre-terminals containing large electron dense granules (NS-I) of approximately 100 to 220 nm and a few axon terminals having small granules (NS-II) of approximately 40 to 90 nm; the former appear to belong to medial neurosecretory A-cells, and the latter to the B-cells of the brain. The corpora cardiaca consist of intrinsic cells with mitochondria and multivesicular bodies. Granules of type NS-II and NS-III are observed in the axon terminals and pre-terminals in the corpora cardiaca. The NS-II are identical to those found in the aorta and are probably the secretions of the lateral B-cells. Granules of type NS-III are 40 to 120 nm and electron dense, and are intrinsic in origin. Similar granules occur in the intrinsic cells of the corpora cardiaca. E M studies have confirmed the rôle of the aorta as a neurohaemal organ for the medial neurosecretory cells, and the corpora cardiaca for the lateral neurosecretory cells of the brain. The corpora cardiaca also act as a reservoir for the intrinsic secretion. The corpus allatum is a solid body consisting of parenchymal cells with prominent nuclei, mitochondria, and endoplasmic reticulum. In between its cells are occasional glial cells and also neurosecretory as well as non-neurosecretory axons. The gland is devoid of A-cell NSM.     

Comparison of the Virulence of Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus

The virulence of methicillin-resistant Staphylococcus aureus (MRSA) was compared with that of methicillin-sensitive S. aureus (MSSA), using 13 MRSA and 7 MSSA strains isolated from clinical specimens. The infectivity and lethality of the two groups were examined as to the inoculum required to infect 50% of guinea pigs (ID₅₀) and to kill 50% of mice (LD₅₀), respectively. The mean ID₅₀ [log₁₀ colony forming units (CFU)] for MRSA strains was 7.1 ± 0.60 standard deviation, which was 1.5 higher than that for MSSA strains (P < 0.001). The mean LD₅₀ (log₁₀ CFU) for MRSA strains was 9.0 ± 0.42, being 1.1 higher than that for MSSA strains (P = 0.001). Pretreatment of mice with cyclophosphamide decreased the mean LD₅₀ for MRSA strains more than that for MSSA strains, resulting in the difference in the mean LD₅₀ being insignificant (P = 0.502). These results indicate that MRSA is less virulent than MSSA in normal hosts, but that they are equally virulent in immunocompromised hosts. The growth of MRSA strains was much slower than that of MSSA strains in the lag phase, although their growth rates were almost the same in the exponential growth phase, suggesting that the difference in virulence between them may be at least partly due to such a difference in growth.     

Synergistic effect on anti-methicillin-resistant Staphylococcus aureus among combinations of α-mangostin-rich extract,lawsone methyl ether and ampicillin

α-Mangostin-rich extract (AME) exhibited satisfactory inhibitory activities against all tested MRSA strains, with minimum inhibitory concentrations (MICs) of 7·8–31·25 µg ml⁻¹, whereas lawsone methyl ether (LME) and ampicillin revealed weak antibacterial activity with MICs of 62·5–125 µg ml⁻¹. However, the combination of AME and LME showed synergistic effects against all tested MRSA strains with fractional inhibitory concentration index (FICI) values of 0·008–0·009, while the combination of AME and ampicillin, as well as LME and ampicillin produced synergistic effects with FICIs of 0·016–0·257. A time-kill assay against MRSA (DMST 20654 strain) revealed a 6-log reduction in CFU per ml, which completely inhibited bacterial growth for the combinations of AME and LME, AME and ampicillin, and LME and ampicillin at a 8-h incubation, while those against MRSA (2468 strain) were at 10-h incubation. The combination of α-mangostin and LME as well as the combinations of each compound with ampicillin synergized the alteration of membrane permeability. In addition, α-mangostin, LME and ampicillin inhibited the biofilm formation of MRSA. These findings indicated that the combinations of AME and LME or each of them in combination with ampicillin had enhanced antibacterial activity against MRSA. Therefore, these compounds might be used as the antibacterial cocktails for treatment of MRSA.     

Synthesis,biological evaluation and structure-activity relationships of 5-arylidene tetramic acids with antibacterial activity against methicillin-resistant Staphylococcus aureus

The steady rise of the antimicrobial resistance is a major global threat to human health that requires the urgent need for novel antibiotics. In this work we report the synthesis of a small library of 3-subsituted-5-arylidene tetramic acids in order to investigate the scope of our previously established methodology via an intermediate oxazolone and their antimicrobial activity. From this series of 14 tetramic acids, 11 derivatives are novel and one of them is a Schiff base, which was structurally characterized with single-crystal X-ray analysis and NMR spectroscopy. The compounds incorporating a lipophilic acyl group at carbon-3 of the ring showed moderate to high activity with minimum inhibitory activity of 4–32 μg/mL against methicillin-resistant Staphylococcus aureus (MRSA), accompanied by no human cell toxicity and hemolytic activity within the tested concentration range. The substituent at para position of the aryl ring seemed to have no or little effect on the antimicrobial activity of these compounds.