Norvaline accumulation by regulatory mutants of Serratia marcescens.

A gene coding for desensitized L-threonine dehydratase was transduced with phage PS20 into a leucine accumulator of Serratia marcescens Sr41. The transductant converted L-threonine to alpha-ketobutyrate, a precursor of both norvaline and isoleucine. An isoleucine-valine auxotroph of the transductant accumulated large amount of norvaline from L-threonine as well as from D-threonine.     

Chemical and electrophoretic changes induced by polymyxin B on outer membrane components from Serratia marcescens.

The effects of polymyxin B (PB) on outer membrane (OM) components from resistant (strain 08) and sensitive (strain Bizio) cells of Serratia marcescens were characterized by chemical analysis and polyacrylamide gel electrophoresis (PGE) in sodium dodecylsulfate. Chemical analysis revealed no major differences in the OM fractions after PB treatment of both strains, except for the loss of protein in PB treated OM of the sensitive strain. The yield and composition between the lipopolysaccharides (LPS) of the two strains were different both before and after treatment. PGE revealed that there was a complex formation between the LPS of resistant strain and PB but both dissociation and degradation occurred in the LPS components in the sensitive strain. In addition, it was found that the protein components were destabilized by PB with subsequent loss of some of the components from OM of the sensitive strain. The difference in the amount of LPS and their ability to complex with PB may reflect different degrees of antibiotic susceptibility of these two strains of S. marcescens. A sequential multistep mechanism is proposed for the action of PB on outer membranes of this species.     

Microbial transformation of maridomycin III by Serratia marcescens

Two transformation products of maridomycin (MDM) III, MDM-S1 and MDM-S2 named after Serratia marcescens, were isolated by silica gel chromatography. NMR and IR analysis revealed that MDM-S1 and -S2 had no aldehyde group at C-18 on the macrolactone ring, and that the hydroxyl group at C-9 seemed to disappear. Although MDM-S1 and -S2 are less active against Gram-positive bacteria than starting MDM III they are interesting materials in view of the introduction of nitrogen into each molecule, and that the transformation products are produced by Gram-negative bacteria which are thought to be insensitive to macrolide antibiotics.     

Failure of drugs that selectively inhibit thromboxane synthesis to modify endotoxin shock in conscious rats.

The effects of two thromboxane synthetase inhibitors ( dazoxiben and UK 38485) were investigated on the cardiovascular and metabolic effects of Escherichia coli endotoxin infusion in the conscious, unrestrained rat. Infusion of E. coli endotoxin (41.7 ng kg-1 min-1) for 4 h produced a fall in mean arterial pressure, an increase in heart rate, a transient hyperglycaemia (at 1 h) followed by hypoglycaemia (evident at 6 h), an elevation in plasma lactate and a profound thrombocytopenia. The above changes were accompanied by a marked elevation in plasma thromboxane B2 concentrations (e.g. endotoxin-treated 935 +/- 150 pg ml-1 at 1 h compared with pre-endotoxin values of 125 +/- 30 pg ml-1). The administration of either dazoxiben (30 mg kg-1 i.v., given 30 min before starting the endotoxin infusion) or UK 38485 (15 mg kg-1 given 30 min before, and again 4 h after, starting the endotoxin infusion) prevented the rise in plasma thromboxane B2 concentrations. Neither dazoxiben nor UK 38485 prevented the metabolic, cardiovascular or thrombocytopenic effects of endotoxin and did not modify mortality. These results suggest that, although large amounts of thromboxane are generated in response to endotoxin, they do not play an important role in the major pathophysiological consequences of acute endotoxaemia.     

Ceftazidime in the treatment of meningitis caused by multiresistant Serratia marcescens]

A patient of subarachnoid hemorrhage was treated with spinal CSF drainage. Serratia marcescens meningitis occurred because of the spinal CSF drainage. The organism was multiresistant and refractory to antibiotics including piperacillin, imipenem, gentamicin and cephaloridine. It was sensitive to ceftazidime (CAZ). Treatment with CAZ resulted in clinical improvement associated with rapid clearing of the organism from CSF. CAZ serum level was high enough and CAZ penetration into the CSF was satisfactory. According to the evaluation of CAZ concentrations in serum and CSF, two regimens of treatment were recommended. One is an administration of CAZ 1 g x 4 times/day. Another is a combination with CAZ administration 2 g x 2 times/day and followed by 1 g x 4 times/day. The results suggest that CAZ is an extremely effective antibiotic for meningitis caused by CAZ-susceptible bacteria.     

The inactivation of gentamicin and netilmicin by carbenicillin: its effect on Serratia marcescens.

Ten clinical isolates of Serratia marcescens were tested on Mueller-Hinton agar containing gentamicin or netilmicin with carbenicillin. The isolates grew on plates where inactivation occurred, at higher antibiotic concentrations, but failed at lower concentrations. This growth response was individualistic and not closely related to the minimum inhibitory concentrations.     

Haemodynamic effects of the carboxylic ionophore monensin when administered before and during shock induced by E. coli endotoxin.

The haemodynamic effects of the carboxylic ionophore monensin have been examined in cats anaesthetized with sodium pentobarbitone. Marked increases in left ventricular dP/dtmax (and dP/dt at fixed isovolumic pressures) and slight increases in cardiac output and stroke volume occurred, indicating increased myocardial contractility. Heart rate was unchanged but systemic arterial pressure was substantially increased. Satisfactory increases in contractility and arterial pressure were obtained when monensin was infused intravenously in a total dose of 0.25 mg kg-1 over 10 min. Larger doses, especially if rapidly injected, resulted in very marked increases in myocardial contractility leading eventually to cardiac failure. The haemodynamic effects of monensin were markedly reduced during shock induced by E. coli endotoxin and there was unfortunately no evidence to suggest that this extremely potent compound might be potentially beneficial in this form of profound cardiovascular shock.     

Decrease by naloxone of some electrocardiographic and biochemical changes following endotoxin induced shock in rats

Administration of endotoxin, a lipopolysaccharide extracted from cell walls of gram negative bacteria, elicited alterations in various metabolic parameters and in the electrocardiogram of rats. Cardiac glycogen and serum glucose were decreased, while serum pyruvate and acid phosphatase levels were increased. There was initial tachycardia followed by significant bradycardia and elevation of the ST segment in the animals with shock. Erythrocyte count, haemoglobin and haematocrit were not changed after shock. Treatment with naloxone caused significant decreases in the metabolic and electrocardiographic changes induced by endotoxin.     

The effects of the protease inhibitor, aprotinin, on the course of shock induced by endotoxin in cats.

The administration of endotoxin derived from Escherichia coli to anaesthetized cats resulted, within the first 5 min, in an initial increase in right atrial pressure and a reduction in systemic arterial blood pressure. Over the next 2 h shock was characterized by a reduced cardiac output, tachycardia, reduced arterial pH and an increased level of lactate. The survival rate at the end of the 8 h experimental period was only 10%. The protease inhibitor aprotinin (Trasylol), given as a continuous intravenous infusion 1000 kallikrein inhibitor units (k.i.u.) kg-1h-1 together with a bolus of 40,000 k.i.u. kg-1, significantly inhibited the severity and incidence of the initial endotoxin response (increase in right atrial pressure and systemic hypotension), perhaps suggesting the direct or indirect involvement of kinins. Aprotinin did not reduce the delayed effects of endotoxin (sustained reduction in cardiac output, lacticacidosis), nor did it improve survival at 8 h. Indeed, there was some evidence that aprotinin exaggerated the delayed effects of endotoxin in this model.     

Haemodynamic effects of the carboxylic ionophore monensin when administered before and during shock induced by E. coli endotoxin

The haemodynamic effects of the carboxylic ionophore monensin have been examined in cats anaesthetized with sodium pentobarbitone. Marked increases in left ventricular dP/dt_max (and dP/dt at fixed isovolumic pressures) and slight increases in cardiac output and stroke volume occurred, indicating increased myocardial contractility. Heart rate was unchanged but systemic arterial pressure was substantially increased. Satisfactory increases in contractility and arterial pressure were obtained when monensin was infused intravenously in a total dose of 0·25 mg kg^?1 over 10 min. Larger doses, especially if rapidly injected, resulted in very marked increases in myocardial contractility leading eventually to cardiac failure. The haemodynamic effects of monensin were markedly reduced during shock induced by E. coli endotoxin and there was unfortunately no evidence to suggest that this extremely potent compound might be potentially beneficial in this form of profound cardiovascular shock.     

Gastric mucosal damage induced by endotoxin shock and its prevention by naloxone and anti-ulcer drugs in rats

Administration of endotoxin (20 mg/kg i.p.) produced a moderate degree of gastric mucosal damage in rats. The lesions remained confined to the glandular mucosa and consisted of small punctiform lesions, erosions and petechial hemorrhage. The characteristic feature of these lesions was a typical submucosal ecchymosis in the glandular stomach observed in about 30% of the animals. Pretreatment with ranitidine, pirenzepine, proglumide, sucralfate and naloxone produced varying degrees of protection. The ulcerogenic effect of endotoxin shock is apparently mediated through the release of endorphins.     

Limitation of polymyxin B on suppression of endotoxin shock induced by Salmonella infection in mice

The protective effects of an antibiotic polymyxin B (PLB), having lipopolysaccharide (LPS)-binding activity, on infection-induced endotoxin shock in mice were investigated. Infection with 10(8) colony forming units of an attenuated Salmonella typhimurium aroA strain caused lethal endotoxin shock to ddY mice. Treatment with PLB 1 h post infection (p.i.) resulted in significant reduction of mortality and bacterial numbers in livers. In addition, treatment with PLB 1 h p.i. resulted in a transient increase at the early stage and gradual decline in plasma LPS levels. Although plasma levels of sCD14 and high mobility group box chromosomal protein-1 (HMGB-1) increased according with progression of infection, increases in plasma levels of sCD14 and HMGB-1 were downregulated by treatment with PLB 1 h p.i. However, the lethal shock was not blocked by treatment with anti-CD14 monoclonal antibody at 3 h and 6 h p.i. Interestingly, administration of PLB 6 h p.i. did not show any protective activities, indicating that a time window for effective PLB action is present.     

Multidrug resistance in Serratia marcescens and cloning of genes responsible for the resistance

Six clinically isolated strains of Serratia marcescens were tested for their drug resistance. All showed fairly high resistance to many antimicrobial agents tested including norfloxacin, streptomycin, ampicillin, erythromycin, tetracycline, chloramphenicol, and antimicrobial dyes. Using the drug-hypersensitive strain of Escherichia coli KAM32 as the host, we cloned the genes responsible for multidrug resistance from chromosomal DNA of one of the strains of S. marcescens, NUSM8906. We obtained 28 hybrid plasmids that made host cells resistant to several antimicrobial agents. Many of the transformants harboring each of the plasmids showed multidrug resistance, and some showed resistance to specific drugs. The hybrid plasmids were classified into several groups based on their drug specificity. It appears that each class of plasmid carries different types of drug resistance genes. Analysis of such genes will reveal the multiple mechanisms involved in multidrug resistance in S. marcescens.     

Evidences for complex formation between polymyxin B and lipopolysaccharides from Serratia marcescens.

In vitro and in vivo complex formations of polymyxin B and lipopolysaccharides (LPS) from resistant and sensitive cells of Serratia marcescens were studied by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and electron microscopy. In vitro treatment of LPS from resistant cells with polymyxin B gave two populations of spherical complexes of differnt molecular weights as determined electrophoretically. Similar treatment of LPS from sensitive cells resulted in dissociation of the LPS-protein and subsequent complexing with the LPS moiety into stable spheres. In vivo treatment of resistant cells with polymyxin B resulted in LPS-polymyxin B complexes which were comparatively smaller and existed in two morphological forms; spheres and linear ribbons. LPS from the sensitive cells were degraded extensively into small rods and an amorphous mass by the in vivo polymyxin B treatment. In both systems, the electrophoretic results consistently matched the electron microscopic evidences for complex formation of LPS with polymyxin B. It is suggested that the disruptive effects of polymyxin B on LPS in the outer membrane of S. marcescens may be the explanation for the change in permeability barrier in the resistant cells and disorganization of the outer membrane and subsequent death in the sensitive cells. Furthermore, the ability of the LPS to complex with the polymyxin B molecules in resistant cells may be the basis of their resistance to the antibiotic.     

Multicomponent assessment and optimization of the cellulase activity by Serratia marcescens inhabiting decomposed leaf litter soil

In lignocellulosic biomass digestion, the enzymatic hydrolysis of lignocellulosic polymers is regarded as the rate-limiting step for enzyme synthesis. The present study is focused on hydrolytic microbial communities isolation from degraded leaf litter soil, and optimization efforts that aid in the decomposition of biomass in the environment. Based on morphological characteristics and leads from preliminary testing, four of the isolates were determined to be effective cellulose degraders. Molecular identification of robust microbial genera included Galactomyces sp. Cefu3, Aspergillus flavus N11, Serratia marcescens CH1, and Bacillus sp Cp4 species, respectively. Serratia marcescens CH1 was determined to be the most potent of the four isolates for cellulase enzyme activity. Further, Serratia marcescens CH1 exhibited highest multi-enzyme activity for endo-(1,4)-β-D-glucanase, exo-(1,4)-β-D-glucanase, and β-glucosidase. The assay conditions were optimized and determined by the Response Surface Methodology (RSM).     

黏质沙雷菌的产酶现状及抗菌药物耐药性的研究

目的 了解黏质沙雷菌产酶现状和耐药性,为临床治疗黏质沙雷菌提供合理用药的实验依据.方法 常规培养分离细菌,应用VITEK-2全自动细菌分析仪鉴定细菌.常规药敏试验采用K-B纸片法,MIC测定采用微量倍比稀释法,按CLSI规定标准进行.结果 从临床感染的标本中分离出50株黏质沙雷菌,主要是呼吸道标本(占45株).其70%...