Silver Nanoforms as a Therapeutic Agent for Killing Escherichia coli and Certain ESKAPE Pathogens

The scope of this study included the preparation of silver nanoforms with high antimicrobial efficacy, low cost, and ease of application. The term 'silver nanoforms' refers to silver located on the amorphous or crystalline titanium dioxide (TiO2). Silver nanoforms may be used as an alternative to antibiotics in killing bacteria. Pure and silver-incorporated titanium (used as a carrier) was prepared using the sol-gel-modified method. Physical and chemical properties of the samples were described, and the antibacterial activity was indicated using the following strains of bacteria: Staphylococcus aureus, Klebsiella pneumoniae (ESKAPE pathogens), and Escherichia coli. The results have shown that the antibacterial activity of silver nanoforms with amorphous TiO2 is much better than that in the samples based on anatase (crystalline TiO2). The sensitivity of the tested bacteria to silver nanoforms depends on physical and chemical properties of the nanoforms and individual characteristics of the bacteria. For the first time, significant participation of amorphous TiO2 in antibacterial compounds has been described through this study.

The role of complement activity in the sensitivity of Salmonella O48 strains with sialic acid-containing lipopolysaccharides to the bactericidal action of normal bovine serum

Sialic acids are important constituents of animal tissue glycoconjugates and are also present in the antigens of some bacterial strains. Capsular polysaccharides with sialic acid (NeuAc) have been extensively studied with regard to sensitivity to the bactericidal action of serum, whereas little is known in this regard about lipopolysaccharides (LPS) which contain NeuAc. Strains of Salmonella O48, able to infect animals and containing the same structures of LPS with NeuAc, were examined for their susceptibility to the bactericidal action of normal bovine serum (NBS). The strains showed varied sensitivity to the bactericidal action of NBS, which indicates that the expression of LPS containing NeuAc residues is not critical for the strains' resistance to the serum's activity. In this study the mechanisms of complement activation responsible for killing serum-sensitive Salmonella O48 rods by NBS were also established. Three such mechanisms were distinguished: activation of the classical/lectin pathways, important (decisive) in the bactericidal mechanism of complement activation, parallel activation of the classical/lectin and alternative pathways, and independent activation of the classical and lectin or the alternative pathway.

Killing of Gram-negative bacteria with normal human serum and normal bovine serum: use of lysozyme and complement proteins in the death of Salmonella strains O48

Serum is an environment in which bacterial cells should not exist. The serum complement system provides innate defense against microbial infections. It consists of at least 35 proteins, mostly in pre-activated enzymatic forms. The activation of complement is achieved through three major pathways: the classical, alternative, and lectin. Lysozyme, widely present in body fluids, catalyzes the hydrolysis of beta 1,4 linkage between N-acetyloglucosamine and N-acetylmuramic acid in the bacterial cell wall and cooperates with the complement system in the bactericidal action of serum. In this study, ten strains of serotype O48 Salmonella, mainly associated with warm-blooded vertebrates and clinically important causing diarrhea in infants and children, were tested. The results demonstrated that the most efficient killing of Salmonella O48 occurred when all the components of normal bovine serum (NBS) and normal human serum (NHS) cooperated. To prove the role of lysozyme in the bactericidal activity of bovine and human serum, the method of serum adsorption onto bentonite (montmorillonite, MMT) was used. In order to investigate structural transitions accompanying the adsorption of serum components, we applied X-ray diffraction methods. The results of this investigation suggested that apart from lysozyme, other proteins (as, e.g., C3 protein or IgG immunoglobulin) were adsorbed on MMT particles. It was also shown that Ca(2+) cations can be adsorbed on bentonite. This may explain the different sensitivities of the serovars belonging to the same O48 Salmonella serotype to NBS and NHS devoid of lysozyme.

[Infectivity and resistance to antibiotics of bacterial strains isolated from patients hospitalised in intensive care units]

The aim of this study was to evaluate the frequency of isolation and antimicrobial resistance testing of bacterial strains isolated from clinical specimens from patients hospitalized in three Intensive Care Units in Wrocław. The susceptibility of bacteria (107 strains) to selected antibiotics was determined. The results clearly show that non-fermentative rods were identified as the main agents causing pneumonia (58% of isolates). The second commonest pathogens were Gram-positive cocci (29%). The P. aeruginosa and E. cloacae strains were resistant to ampicillin, amoxicillin/clavulanate, cefuroxime and cefotaxime. All isolates of A. baumanii were susceptible only to imipenem. The rods of K. pneumoniae and E. coli were resistant to ampicillin, about 55% strains of both bacteria were sensitive to other antibiotics, except piperacillin/tazobactam, imipenem and ciprofloxacin. About 90% of methicillin resistant S. epidermidis strains were resistant to all antibiotics, except vancomycin (100% isolates were sensitive). ESBL were detected among E. cloace, K. pneumoniae and E. coli. We found P. aeruginosa rods producing MBL.

The mechanisms of activation of normal human serum complement byEscherichia coli strains with K1 surface antigen

Ten E. coli K1 strains isolated from the urine of children with urinary tract infections were sensitive to the bactericidal action of normal human serum (NHS). The role of the particular mechanisms of complement activation was determined in the process of killing these strains, showing variable sensitivity to the bactericidal action of NHS; three mechanisms of activation of human complement were observed. Important role of alternative pathway activation in the bactericidal action of NHS against E. coli K1 strains independent of the classical and lectin pathways was not established.

[Etiological factors of urinary tract infections in children]

Etiological factors of urinary tract infection in children have been studied. The Escherichia coli, Klebsiella sp., Enterococcus sp. and Enterobacter sp. were the most often isolated bacteria from infant and baby urine. In this age group of patients uromycoses were also affirmed. From the urine of older children (1-18 years old) mainly Escherichia coli, Enterococcus sp., Proteus sp. and Morganella morganii have been raised. Uropathogens' occurrence was analysed by a statistical method in the relation to age and sex of the children. The girls in the age of 1 to 18 years were more open than boys to urinary tract infections caused by Escherichia coli and less open to infections caused by Morganella morganii and Enterococcus sp.

Bactericidal activity of normal cord serum (NCS) against Gram-negative rods with sialic acid-containing lipopolysaccharides (LPS)

Sialic acids, that are important constituents of animal tissue glycoconjugates, are also present in antigens of some bacterial strains. Capsular polysaccharides with sialic acid have been extensively studied whereas little is known on lipopolysaccharides which contain sialic acid. The susceptibility of Gram-negative strains with sialic acid-containing lipopolysaccharides to the bactericidal action of the sera of newborns was examined. The strains investigated showed variable sensitivity to the bactericidal action of normal cord serum.

Entomopathogenic activities of environmental isolates of Bacillus thuringiensis against dipteran larvae

Twenty-five field isolates of Bacillus thuringiensis from the Lower Silesia region of Poland, the Osola plain, and phylloplane niches and soil samples from the Karkonosze National Park were tested for insecticidal activity against larvae of the dipterans Aedes aegypti, Drosophila melanogaster and Musca domestica. The spore-crystal mixture of B. thuringiensis finitimus (soil isolate) killed nearly half of the fourth instar larvae of Ae. aegypti. Similar mortality of between 39-61% was recorded after treatment with two phylloplane isolates belonging to biochemical type I of B. thuringiensis (subsp. japonensis, yoso and jinghongiensis) and type IV (subsp. tochigiensis,). The effect of B. thuringiensis wratislaviensis H-47 was lowest, with larval mortality ranging from 7-28%. The susceptibility of D. melanogaster, evaluated as percentage of larvae that did not survive to adulthood, varied between 0-38% and 0-45% at dosages of 0.5 and 1 ml, respectively. The LC50s ranged from 5.07 x 10(9) to 1.04 x 10(11) spore-crystal mixture. The LC50s for M. domestica larvae were 4.1-4.8 x 10(8) spores/ml of B. thuringiensis finitimus and the phylloplane strain KpC1 (I type) and 2.9 x 10(9) for the phyloplane representative of group I. Generally, all tested isolates showed the most activity against common fly larvae. The highest (64-81% mortality) was observed after treatment with both phylloplane (OpPs1, KpF3, KpC1) and soil isolates (KsAc1) of biochemical type I as well as B. thuringiensis finitimus (type III).

[Infectivity and resistance to antibiotics of uropathogenic gram-negative rods]

The nature of bacterial isolates from children with clinically suspected urinary tract infections (UTI) was studied. The susceptibility of urinary pathogens to selected antibiotics was determined. The results clearly show that E. coli was identified as the main causative agent of UTI children (67% of isolates). The second commonest pathogen was P. mirabilis (10%). Over half E. coli isolates were resistant to amino-penicilins but almost all isolates (over 80%) were sensitive to antimicrobial agents combined with beta-lactamase inhibitors. We found significantly high percentage (32.5%) of ESBL strains among K. pneumoniae isolates.

Synergistic bactericidal effect of cephalexin and normal cord serum (NCS) against Escherichia coli K1 strains isolated from children with urinary tract infections (UTI)

Investigations were performed on the bactericidal activity of cephalexin (keflex) and normal cord serum (NCS) against Escherichia coli K1 strains isolated from UTI. A synergistic interaction of the antibiotic and NCS was found against the strains resistant and sensitive to the serum.

The susceptibility of gram-negative rods and their adaptive forms resistant to colistine to the bactericidal action of sera

The susceptibility of Escherichia coli K1, Salmonella enteritidis, Salmonella typhimurium strains and their adaptative forms resistant to colistine (Colr forms) was compared with respect to their sensitivity to the bactericidal action of normal cord serum and normal bovine serum. It has been shown that the Colr forms are more susceptible to sera as compared to initial strains. The increase of sensitivity of the Colr forms is connected with structural changes within bacterial cell wall which is the target for complement as well as for colistine.

Mechanism of antigenic variation in Shigella flexneri bacilli. IV. Role of lipopolysaccharides and their components in the sensitivity of Shigella flexneri 1b and its Lac+ recombinant to killing action of serum

The effect of lipopolysaccharides (LPS) on the normal bovine serum (NBS) bactericidal reactions against mixture of S. flexneri 6713 1b strain and its 3b Lac+ recombinant were investigated. The serum killing of S. flexneri strains was inhibited, in different degree, by LPS extracted from either organisms. These properties were mainly due to LPS molecules; the lipid A fraction showed only low anticomplement activity, the polysaccharide fraction inhibited the killing activity of NBS in very low degree even at high concentration. These studies suggest that LPS composition especially the O-antigen polysaccharide chain contributes to the susceptibility of S. flexneri strains to NBS bactericidal activity.

Influence of ozone on the susceptibility of Escherichia coli K1 to the bactericidal action of serum

The susceptibility to the bactericidal action of normal bovine serum of twenty two Escherichia coli K1 strains, isolated from the urine of patients with urinary tract infections, was determined. Only four strains were resistant. Ozonization of bacterial suspensions enhanced the sensitivity of the strains to the action of both normal serum and a serum in which the alternative pathway of complement activation was thermally blocked.

[Bacterial antigenic structure of Shigella flexneri serotype 1B and its 3B serotype mutant and susceptibility to bacterial action of complement in normal bovine serum]

The susceptibility of S. flexneri 1b and 3b strains to killing action of serum was investigated. Differences in sensitivity to bactericidal action of complement appeared to result from different structure of their LPS-es. The protective effect of LPS-es depends both on their origin and concentration.

Studies on the influence of ozone on complement-mediated killing of bacteria

The role of ozone in the susceptibility of clinical isolates of Acinetobacter anitratus and Pseudomonas aeruginosa to serum was investigated. It was found that ozone-treated cells were more susceptible to complement-mediated killing serum. These results suggest that ozone damage or change of cell membrane leads to a more rapid penetration of the membrane attack complex of complement.

Preliminary studies of the effect of ozone on the bactericidal properties of complement

The study analyzes the bactericidal influence of an ozonized blood serum on gram-negative bacilli. Considerable differences were observed concerning the effect which ozonized normal human serum has upon Klebsiella, Pseudomonas and Salmonella strains. It was found that the impact may vary depending not only on the time of the exposure of serum to ozone, but also on the type of strain and the structure of the outer membrane of the bacteria. The Salmonella typhimurium strain of the Ra chemotype treated with the serum which was exposed to ozone showed higher susceptibility to the action of complement than the S. typhimurium strain of the S chemotype.