Genetics of high level penicillin resistance in clinical isolates of Streptococcus pneumoniae

Abstract Mosaic penicillin-binding proteins (PBP) 1A, 2X and 2B genes were cloned from four clinical isolates of Streptococcus pneumoniae with levels of susceptibility to penicillin ranging from 1.5 to 16 μg benzylpenicillin ml⁻¹. In each instance it was possible to transform either the penicillin-sensitive laboratory strain R6 or a sensitive clinical isolate 110K/70 to the full level of penicillin resistance with these three penicillin-binding proteins alone. Until now it has not been possible to clearly determine whether alterations to PBP1A, 2X and 2B alone were sufficient to attain high level penicillin resistance.     

A study of pathogenic factors of Streptococcus pneumoniae strains causing meningitis

Abstract Pneumococcal meningitis in St. Petersburg in the period 1985–1991 occurred in 1.7–2.3 children per 100 000 annually. The most common serotypes among pneumococcal strains isolated from patients with meningitis were 19, 1, 6, 15, and 2, whereas, among the capsulated strains isolated from carriers, type 3 predominated. Only one third of strains from cases of meningitis were highly virulent for mice (types 1, 2, 3). Hyaluronidase was produced by all the 39 studied strains, 22 (84.6±7.1%) out of 26 strains from patients with otitis media, and only by 15 (11.5±2.8%) out of 130 strains isolated from carriers. Non-capsulated strains lacked this enzyme. Results of intranasal inoculation of pneumococcal strains with different hyaluronidase activity and addition of exogenous hyaluronidase to strains which did not produce the enzyme confirm the hypothesis that this enzyme plays an important role in bacterial dissemination and breaching of the blood brain barrier by pneumococci. It was concluded that high hyaluronidase activity, presence of capsule, and pneumolysin or serotype (1, 2, and 19) despite hyaluronidase titer, are the most important factors contributing to the development of pneumococcal meningitis. The role of the mouse toxic factor is unclear.     

The preservation of Mycoplasma capricolum cell intactness after phospholipase A2 treatment

(1) By treating Mycoplasma capricolum cells with phospholipase A₂ about 80% of membrane phospholipids were rapidly hydrolyzed. The rate and extent of hydrolysis (at 37°C) were the same in intact cells and in isolated unsealed membranes. (2) Due to the low endogenous lysophospholipase activity detected in M. capricolum, phospholipase A₂ treatment resulted in the accumulation of lysophospholipids and free fatty acids. The free fatty acids were efficiently extracted from the cells by 1% bovine serum albumin whereas the lysophospholipids were almost fully retained within the cell membrane. (3) Following phospholipase A₂ treatment in the presence of 1% bovine serum albumin, cell intactness was preserved as indicated by the constant absorbance of the cell suspension and the retention of nucleic acids and NADH dehydrogenase activity within the cells. The treated cells showed, however, a slight decrease in K⁺ content and a decrease in cell viability. Viability was fully preserved after phospholipase A₂ treatment of cells grown with exogenous sphingomyelin. (4) Adapting M. capricolum to a cholesterol-poor medium resulted in a marked decrease in the cholesterol to phospholipid molar ratio (from about 1.1 to 0.3). Phospholipase A₂ treatment of the cholesterol-poor cells resuted in cell lysis. Cell lysis was induced in the cholesterol-rich cells by hydrolysing the lysophospholipids accumulated following phospholipase A₂ treatment. (5) It is suggested that after phospholipase A₂ treatment of M. capricolum cells, a relatively stable cell membrane is maintained and cell intactness is preseved due to the interaction of cholesterol, present in high amount in this membrane, with the lysophospholipids formed.     

Active K+ transport in Mycoplasma mycoides var. Capri. Net and unidirectional K+ movements

Analysis of the cation composition of growing Mycoplasma mycoides var. Capri indicates that these organisms have a high intracellular K⁺ concentration ($\text{K}{}_{\mathrm{<mtext>i</mtext>}}\text{: 200–300}\text{mM}$) which greatly exceeds that of the growth medium, and a low Na⁺ concentration ($\text{Na}{}_{\mathrm{<mtext>i</mtext>}}{}^{\mathrm{+}}\text{: 20}\text{mM}$). Unlike $\text{Na}{}_{\mathrm{<mtext>i</mtext>}}{}^{\mathrm{+}}\text{, K}{}_{\mathrm{<mtext>i</mtext>}}{}^{\mathrm{+}}$ varies with cell aging.The K⁺ transport properties studied in washed organisms resuspended in buffered saline solution show that cells maintain a steady and large K⁺ concentration gradient across their membrane at the expense of metabolic energy mainly derived from glycolysis. In starved cells, $\text{K}{}_{\mathrm{<mtext>i</mtext>}}{}^{\mathrm{+}}$ decreases and is partially compensated by a gain in Na⁺. This substitution completely reverses when metabolic substrate is added (K⁺ reaccumulation process). Kinetic analysis of K⁺ movement in cells with steady K⁺ level shows that most of K⁺ influx is mediated by an autologous K⁺-K⁺ exchange mechanism. On the other hand, during K⁺ reaccumulation by K⁺-depleted cells, a different mechanism (a K⁺ uptake mechanism) with higher transport capacity and affinity drives the net K⁺ influx. Both mechanisms are energy-dependent.Ouabain and anoxia have no effect on K⁺ transport mechanisms; in contrast, both processes are completely blocked by dicyclohexylcarbodiimide, an inhibitor of the Mg²⁺-dependent ATPase activity.     

Scanning electron microscopy ofMycoplasma pneumoniae on the membrane of individual ciliated tracheal cells

Summary Cell monolayer cultures were prepared from hamster tracheal explants by a collagenase exposure and subsequent incubation in Waymouth’s MAB 87/3 medium. The epithelial outgrowth occurred on glass cover slips. Cilia on the monolayers continued to beat normally after the “parent” explant was removed. Monolayer cultures infected withMycoplasma pneumoniae had significant amounts of attachment. A morphological analysis of the attachment was conducted with scanning electron microscopy. Clusters, cocci, and filaments ofM. pneumoniae all attached to the epithelial cells, but the filaments were especially common. Mycoplasmas were seen in association with both ciliated and nonciliated cell membranes. On ciliated cells, mycoplasmas were on the ciliary strands and on the cell membrane. When located immediately adjacent to or in between cilia, mycoplasmas were oriented vertically with the constricted attachment tip oriented down toward the host cell membrane. When located more than a micron away from the ciliary fibers, mycoplasmas lay horizontally along the epithelial cell membrane. The photographic data suggest that clusters or “sperules” of mycoplasmas may liberate individual mycoplasmas that attach to the cell membrane. It appears that the receptor sites forM. pneumoniae are rather uniformly distributed along the ciliated cell membrane, and are not restricted to the interciliary areas. Electron microscopy was done with the cooperation of Dr. R. Macleod and the staff of the Center for Electron Microscopy at the University of Illinois. Critical editorial review was provided by C. Dayton. This investigation was supported in part by grants to M. G. G. from the National Institute of Allergy and Infectious Diseases (AI 12559) and the National Heart, Lung, and Blood Institute (HL 23806), Bethesda, Maryland.     

Streptococcus pneumoniae type 3 encodes a protein highly similar to the human glutamate decarboxylase (GAD65)

Abstract A 2.5-kb Sca I fragment of the type 3 pneumococcal strain 406 DNA containing a 1425-nucleotide open reading frame ( gadA ) and encoding a 475-amino acid protein ( M _rmr 54427) was characterised. The gene gadA was expressed in Salmonella typhimurium . Pulsed-field gel electrophoresis and Southern blotting analysis of DNAs prepared from several pneumococcal serotypes showed that only those clinical isolates belonging to serotype 3 harbour the gadA gene. Sequence comparison of GadA with proteins included in the data banks revealed the highest similarity with human glutamate decarboxylase (GAD₆₅) (59% similarity, 28% identity). Auto-antibodies to GAD₆₅ have been associated with the onset of insulin-dependent diabetes mellitus. Interestingly, several epitopes of GAD₆₅ that have been identified as immunodominant are particularly well conserved in the pneumococcal GadA.     

Autolysins are direct involved in the bactericidal effect caused by penicillin in wild type and in tolerant pneumococci

The two pneumococcal autolytic enzymes (an N-acetylmuramoyl-L-alanine amidase and an endo-beta-1,4-N-acetylglucosaminidase) are directly involved in the penicillin-induced killing of Streptococcus pneumoniae. The activity of these lytic enzymes was efficiently controlled in tolerant mutants under physiological conditions.     

RNA polymerase heterogeneity in Streptomyces aureofaciens: characterization by antibody-linked polymerase assay

The ability of Escherichia coli with different receptor specificities to interact with meconium was studied. E. coli strains expressing P-fimbriae, specific for Gal alpha 1-4Gal beta-containing receptors, were agglutinated by meconium at high titres. This reaction was inhibited by globotetraosylceramide. The attachment of P-fimbriated E. coli to human colonic epithelial cells of the HT-29 cell line was inhibited by meconium. Some type 1 fimbriated strains were agglutinated by meconium, but the agglutination was rarely blocked by methyl alpha-D-mannoside. The attachment by type 1 fimbriated strains to HT-29 cells was reduced by meconium only in some cases. These results suggest that meconium interacts with the P-fimbriae of E. coli, in a way that may influence bacterial colonization of the neonatal intestine.     

肺炎支原体感染对儿童血常规参数及C反应蛋白水平的影响

摘要 目的：探讨肺炎支原体（Mycoplasma pneumoniae, MP）感染对儿童血常规数及C反应蛋白（C reactive protein, CRP）水平的影响。方法：以60例肺炎支原体抗体（MP-IgM）阳性患儿作为观察组,选取同期60名MP-IgM阴性儿童作为对照组,对两组患儿血常规参数和CRP水平进行回顾性分析。结果：与对照组比较,观察组红细胞压积、血红蛋白、单核细胞比例、单核细胞计数、中性粒细胞比例、中性粒细胞计数、红细胞计数均数或中位数升高,嗜碱性粒细胞比例、嗜碱性粒细胞计数、嗜酸性粒细胞比例、嗜酸性粒细胞计数、淋巴细胞比例（LY）、淋巴细胞比计数（LY#）、平均红细胞血红蛋白量、红细胞平均体积、平均血小板体积、血小板压积、血小板分布宽度、血小板计数、红细胞分布宽度均数或中位数降低;观察组患儿的CRP水平中位数显著高于对照组,以上差异有统计学意义（P<0.05）;Logistic多元回归分析结果显示,MP感染与淋巴细胞比例、淋巴细胞比计数降低具有正相关性（P<0.05）。结论：MP感染患儿的血常规参数和CRP水平均发生变化,临床医生应对这些参数给予关注和连续监测,从而提高诊疗效果。     

妇科门诊患者阴道分泌物检测及支原体感染情况和耐药性

目的分析妇科门诊患者阴道分泌物及支原体感染和耐药性情况。方法选取我院2017年7月至2018年7月于妇科门诊就诊的1 200例患者为研究对象,收集患者阴道分泌物并检测支原体感染情况及其耐药性。结果 1 200例患者中患滴虫性阴道炎者13例(1.08%),霉菌性阴道炎139例(11.58%),细菌性阴道病97例(8.08%)。阴道清洁度Ⅲ～Ⅳ度的患者滴虫性阴道炎、霉菌性阴道炎、细菌性阴道病的发生率显著高于清洁度Ⅰ～Ⅱ度的患者(均P0.05)。不同年龄段患者滴虫性阴道炎、霉菌性阴道炎和细菌性阴道病的发生率差异无统计学意义(均P0.05)。25岁的患者解脲支原体(Un)感染率最高(58.10%),35～44岁患者人型支原体(Mh)感染率最高(5.09%),25岁患者Un合并Mh感染率最高(21.91%)。支原体总敏感率较高的抗生素为美满霉素(95.86%)、强力霉素(95.15%)和交沙霉素(97.05%),敏感率较低的为甲砜霉素(19.15%),克林霉素(14.66%)和司帕沙星(27.77%)。结论阴道清洁度与阴道炎的发生具有相关性。患者阴道分泌物中支原体的检测及药敏试验可为临床治疗提供参考依据。