Complete Bactericidal Activity Research Articles

Bactericidal activity of slightly acidic electrolyzed water against the cariogenic bacterium Streptococcus mutans and other oral bacteria

AbstractIntroductionSlightly acidic electrolyzed water (SAEW) is sterilizing agent produced by the electrolysis of hydrochloric acid. Because SAEW has been applied to various foods as the disinfectant, SAEW is expected to be used in the medical field. In this study, we evaluated the bactericidal effect of SAEW on various oral bacteria.MethodologyThe bactericidal activity of SAEW against cariogenic bacteria, periodontopathogenic bacteria, and antibiotic‐resistant bacteria was evaluated.ResultsWe first examined the effect of SAEW on Streptococcus mutans UA159 with different reaction time or the number of bacterial cells. SAEW showed complete bactericidal activity against up to 107 cells within 1 min and even 10 s. Against cariogenic bacteria, periodontopathogenic bacteria, and antibiotic‐resistant bacteria, we evaluated the bactericidal effect of SAEW against 10 S. mutans clinical isolates, three periodontopathogenic bacteria, and 18 cephalosporin‐resistant Gram‐negative bacteria, and we found complete killing against all bacteria. Various dilutions (25%, 50%, and 75%) of SAEW by water still showed complete bactericidal activity, while dilutions by artificial saliva lost the bactericidal activity significantly, with 23.3% bactericidal activity even by 75% SAEW. Storage of SAEW for 7 days at room temperature still showed complete killing activity.ConclusionOur results demonstrated that SAEW has a high antibacterial effect on oral bacteria, indicating the possibility of clinical use in the dental field such as disinfection of dental devices and oral care.

CHEMICAL COMPOSITION AND BIOLOGICAL PROPERTIES OF THE KIDNEYS OF POPULUS NIGRA L. OF THE CASPIAN REGION

The chemical composition of low molecular weight organic compounds (NOS) was studied by chromatography-mass spectrometric analysis of Populus nigra L. kidneys. Of the Caspian region and comparative antimicrobial (bactericidal) activity of extractive components with other plants with characteristic antimicrobial properties. The extraction was carried out by percolation in water-alcohol solutions. The study of antimicrobial activity was carried out by the standard CFU method. As a result, 49 compounds were identified, of which 10 remained unidentified. The study of comparative antimicrobial properties of plant extracts showed the complete bactericidal activity of Populus nigra kidneys against opportunistic microorganisms and microflora of air and water, in MIC equal to 0.25 micrograms/ml. Therefore, the NOSES isolated from the kidneys of Populus nigro of the Caspian region have prospects for further study of antioxidant activity for the preparation of biotechnological drugs and pharmaceutical substances.

Bacterial Response to the Surface Aging of PLA Matrices Loaded with Active Compounds.

The use of active components in biomaterials improves the properties of existing ones and makes it possible to obtain new devices with antibacterial properties that prevent infections after implantation, thus guaranteeing the success of the implant. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles were incorporated into polylactic acid (PLA) films to assess the extent to which progressive aging of the new surfaces resists bacterial colonization processes. For this purpose, the films' surface was characterized by contact angle measurements, ToF-SIMS and AFM, and adhesion, viability and biofilm growth of Staphylococcus epidermidis bacteria on these films were also evaluated. The results show that the inclusion of Mg and CTAB in PLA films changes their surface properties both before and after aging and also modifies bacterial adhesion on the polymer. Complete bactericidal activity is exhibited on non-degraded films and films with CTAB. This antibacterial behavior is maintained after degradation for three months in the case of films containing a higher amount of CTAB.

Antibacterial Activity and Mode of Action of β-caryophyllene on Bacillus cereus

Natural products such as essential oils (EOs) are secondary metabolites that can be obtained from either plant or animal sources or produced by microorganisms. Much attention has been given to exploring the use of secondary metabolites as natural antibacterial agents. This study investigates the antibacterial activity and mechanism of β-caryophyllene, a compound that can be found in various EOs, against Bacillus cereus. The minimum inhibitory concentration of β-caryophyllene against B. cereus was 2.5% (v/v), whereas killing kinetics of β-caryophyllene at minimum inhibitory concentration recorded complete bactericidal activity within 2 hours. Zeta-potential measurement in the cells treated with half the minimum inhibitory concentration of β-caryophyllene at 1.25% (v/v) showed an increase in the membrane permeability surface charge to –3.98 mV, compared to untreated cells (–5.46 mV). Intracellular contents leakage of UV-absorbing materials was detected in the cells treated with β-caryophyllene. Additionally, β-caryophyllene does not interfere with the efflux activity of B. cereus via the ethidium bromide influx/efflux activity. The results revealed that β-caryophyllene was able to alter membrane permeability and integrity of B. cereus, leading to membrane damage and intracellular content leakage, which eventually caused cell death.

Antimicrobial effect of nisin electrospun amaranth: pullulan nanofibers in apple juice and fresh cheese

Nisin-loaded amaranth protein isolate:pullulan (API:PUL) nanofibers were prepared by the electrospinning method. The nisin release kinetic was evaluated at pH 3.4 and 6.1 and the antimicrobial effectiveness of the electrospun mats was evaluated in apple juice and fresh cheese. The nisin API:PUL fibers with 120 nm average diameter reached 81.49% and 43.85% nisin release after 12 h at pH 3.4 and 6.1, respectively. The encapsulation of nisin in electrospun fibers allowed complete bactericidal activity against Salmonella Typhimurium, L. monocytogenes and L. mesenteroides inoculated in apple juice after 48, 20 and 48 h, respectively. When nisin API:PUL fibers were applied to fresh cheese, microorganism inactivation was complete after 142, 120 and 170 h, respectively. The results demonstrated that nisin API:PUL electrospun fibers significantly reduce the bacterial population and can be used in food products for microbiological safety.

In Vitro Activity of Ceftolozane-Tazobactam against Multidrug-Resistant Nonfermenting Gram-Negative Bacilli Isolated from Patients with Cystic Fibrosis.

Ceftolozane-tazobactam was tested against 58 multidrug-resistant nonfermenting Gram-negative bacilli (35 Pseudomonas aeruginosa, 11 Achromobacter xylosoxydans, and 12 Stenotrophomonas maltophilia isolates) isolated from cystic fibrosis patients and was compared to ceftolozane alone, ceftazidime, meropenem, and piperacillin-tazobactam. Ceftolozane-tazobactam was the most active agent against P. aeruginosa but was inactive against A. xylosoxydans and S. maltophilia In time-kill experiments, ceftolozane-tazobactam had complete bactericidal activity against 2/6 clinical isolates (33%).

Phage tail-like particles kill Clostridium difficile and represent an alternative to conventional antibiotics

Current Clostridium difficile infection (CDI) antibiotic regimens have become increasingly ineffective at achieving cure and preventing recurrence. A recently developed alternative to conventional antibiotics are phage tail-like particles (PTLPs), which are proteins that are morphologically similar to bacteriophages and are produced by C difficile. This study examines the in vitro killing spectrum of a previously unreported PTLP isolated from a clinical isolate of C difficile. Using patient-derived samples from an institutional review board-approved C difficile tissue bank, a ribotype 078 C difficile isolate was anaerobically incubated on blood agar plates that were preswabbed with norfloxacin to induce the production of PTLPs. Concentrated PTLP populations were confirmed using transmission electron microscopy. Using a standard lawn spot approach, bactericidal activity was assessed as indicated by a clearing within the bacterial lawn. The PTLP genomic cluster was also fully sequenced and open reading frames were annotated according to predicted function. PTLPs were assessed using 64 patient-derived C difficile isolates of varying ribotypes. PTLPs demonstrated complete bactericidal activity in 21 of 25 ribotype 027 isolates with partial activity in 2 of the 25. Complete bactericidal activity was not demonstrated against any other ribotype or non-difficile bacteria, suggesting a species and ribotype specificity. Functional genes, which may be necessary for killing, were identified within the PTLP genetic locus. PTLPs demonstrate capability in eradicating C difficile in vitro, and with further development, may represent an organism-specific, microbiome-sparing therapy for CDI.

Exploration of in vitro time point quantitative evaluation of newly synthesized benzimidazole and benzothiazole derivatives as potential antibacterial agents

Present communication deals with the in vitro time point quantitative antibacterial evaluation of newly synthesized 1,2-disubstituted benzimidazoles (3a-p) and 2-substituted benzothiazoles (5a-h) against Gram-positive bacteria Staphylococcus aureus, Bacillus cereus, and Gram-negative bacteria Vibrio cholerae, Shigella dysenteriae and Escherichia coli. These compounds were synthesized under mild reaction conditions using Al(2)O(3)-Fe(2)O(3) nanocrystals as heterogeneous catalyst. Bio-evaluation studies revealed that, compounds 3a, 5a and 5d exhibited moderate to good antibacterial activity against all the tested bacterial stains. The compounds 3a, 3f and 5a have shown enhanced inhibitory activity compared with standard antibacterial drug ciprofloxacin against V. cholerae, B. cereus, and S. dysenteriae, respectively. Additionally, the compounds 3a, 3e, 3f, 3h and 5b displayed complete bactericidal activity within 24 h, whereas ciprofloxacin took 48 h to kill those bacteria completely.

Antibacterial activity of Acinetobacter baumannii phage ϕAB2 endolysin (LysAB2) against both Gram-positive and Gram-negative bacteria

To investigate the nature and origin of the antibacterial activity of the lytic phage ϕAB2 toward Acinetobacter baumannii, we successfully isolated and characterized a novel phage lysozyme (endolysin) from ϕAB2 and named it LysAB2. To analyze antibacterial activity of LysAB2, the complete LysAB2 and two deletion derivatives were constructed, purified and characterized. Zymographic assays showed that only the intact LysAB2 could lyse the peptidoglycan of A. baumannii and the Staphylococcus aureus cell wall. Antibacterial analysis also showed that only the intact LysAB2 retained the complete bactericidal activity. When applied exogenously, LysAB2 exhibited a broad bacteriolytic activity against a number of Gram-negative and Gram-positive bacteria. Thermostability assays indicated that LysAB2 was stable at 20∼40 °C. Its optimal pH was 6.0, and it was active from pH 4 to 8. Scanning electron microscopy revealed that exposure to 500 μgml(-1) LysAB2 for up to 60 min caused a remarkable modification of the cell shape of the bacteria. Treating bacteria with LysAB2 clearly enhanced permeation of the bacterial cytoplasmic membrane. These results indicate that LysAB2 is an effective lysozyme against bacteria, and they suggest that it is a good candidate for a therapeutic/disinfectant agent to control nosocomial infections caused by multiple drug-resistant bacteria.

The in vitro pharmacological activities of 12 South African Hermannia species

Hermannia species are widely used in traditional medicine in southern Africa, however no extensive study has been conducted on this genus. The acetone extracts of 12 indigenous Hermannia species (flowers, stems and leaves combined) were evaluated for various pharmacological activities. All investigated species displayed promising antimicrobial activity, with Hermannia saccifera being the most active against Staphylococcus aureus (MIC = 19.5 μg/ml), Bacillus cereus (MIC = 19.5 μg/ml) and Enterococcus faecalis (MIC = 125 μg/ml). Time-kill studies on H. saccifera against S. aureus indicated bacteriostatic activity at 1.25, 2.5 and 5.0%, and a concentration of 7.5% achieved complete bactericidal activity after 4 h. Ten of the 12 species indicated good free radical scavenging activity, with H. cuneifolia demonstrating the most promising activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH :IC 50 = 10.26 μg/ml) and 2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS + /TEAC: IC 50 = 10.32 μg/ml) assays. In addition, all species exhibited moderate anti-inflammatory activity in the 5-lipoxygenase assay with the exception of H. cuneifolia (IC 50 = 15.32 μg/ml) . Overall, the selected species were low in cytotoxicity, except for H. saccifera and H. trifurca. Several Hermannia species indicated promising in vitro biological activity which relate to their traditional use in treating a number of disease states.

Assessment of immune response to meningococcal disease: comparison of a whole-blood assay and the serum bactericidal assay

A whole-blood assay (WBA), which assesses the complete bactericidal activity of blood, was compared with the serum bactericidal assay (SBA), which measures antibody and complement mediated cell lysis. Twenty children infected with serogroup B strains and 25 infected with serogroup C strains were studied 8–12 weeks after disease, and 29 healthy children were used as controls. The infecting strain (convalescent children only) and two reference strains, MC58 (B:15:P1.7, 16) and NCTC 8554 (C:NT:P1.5) were used. In children previously infected with a serogroup B strain, bactericidal activity was detected in 95% and 85% to their infecting strain by the WBA (>50% killing) and the SBA (s), respectively. Bactericidal activity to the reference serogroup B and C strain was detected by WBA in 70 and 75% of children, respectively, and the SBA in 45% and 20%. In contrast bactericidal activity was detected to both serogroup C strains in >80% of children previously infected with a serogroup C strain using either assay and in 48% (WBA) and 20% (SBA) to the reference serogroup B strain. Levels of bactericidal activity were detectable in fewer control children. Children convalescing from meningococcal disease develop an immune response to their infecting strain, detectable by both the WBA and SBA, which is independent of age. However, the WBA appears to be a more sensitive measure of bactericidal activity to heterologous strains than the SBA.

Relationship of high tissue concentrations of azithromycin to bactericidal activity and efficacy in vivo

Measurement of killing kinetics of azithromycin against strains of Streptococcus pneumoniae and Klebsiella pneumoniae in vitro showed that it had a limited bactericidal activity (greater than 90% kill) for the first eight hours of incubation, but developed complete bactericidal activity (greater than 99.9% kill) by 24 h incubation. Since high and sustained tissue levels of azithromycin occur in animals and humans, it was proposed that it might produce a bactericidal effect in vivo. This was demonstrated in a lung infection model in mice, designed to mimic the in-vitro killing studies. A 25 mg/kg dose of azithromycin given 24 h before intranasal challenge reduced the recoverable Str. pneumoniae population by greater than 99.9%, in comparison with untreated controls. Erythromycin did not produce a bactericidal effect at 100 mg/kg, and roxithromycin only reduced the viable count by 96%, at a dose of 50 mg/kg. Against a K. pneumoniae lung infection, a 50 mg/kg dose of azithromycin reduced the bacterial count by 99%. The bactericidal effect was correlated with lung tissue concentrations of azithromycin. In a proliferating Escherichia coli paper disc infection model, extravascular fluid concentrations of azithromycin were correlated with a 99.9% reduction in bacterial count, while corresponding serum concentrations were always less than the MIC. Dosing with azithromycin eradicated Haemophilus influenzae from the bulla (middle ear) of gerbils, as was not the case with erythromycin and roxithromycin. This effect was correlated with the antibiotic concentration in bulla lavage.

PH-dependent bactericidal effects of acidulated fluoride gels on preformed plaque aggregates of Streptococcus mutans 6715

The anticaries action of topically applied sodium fluoride (NaF) preparations has been attributed, at least in part, to the antibacterial effect of fluoride on cariogenic bacteria. In this report we examined the bactericidal activity of acidulated NaF gels against preformed plaque aggregates of Streptococcus mutans 6715. Both commercially available and laboratory-prepared gels were tested. Prepared NaF gels were acidified to various pH levels with HCl, H3PO4, or HF. The aggregates of S. mutans were immersed in the various fluoride gels for 5 min and then monitored for viability. None of the commercially available NaF gels with pHs of 3.5 to 4.5 and fluoride concentrations of 5,000 to 12,300 micrograms/ml were capable of exerting complete bactericidal activity against aggregates of S. mutans. For the laboratory-prepared NaF gels, neither the source of hydrogen ion nor the source of fluoride influenced the outcome when fluoride was present at the appropriate MBC and pH. NaF gels with a fluoride concentration of 37,000 micrograms/ml were bactericidal to S. mutans at pH 3.0. At pH 2.5 and 2.0, approximately 12,000 and 1,100 micrograms of fluoride per ml, respectively, was bactericidal. Results from this study suggest that the bactericidal properties of acidulated NaF gels can be enhanced by lowering their pHs to below 3.0.

Enterococci

• Enterococci cause urinary tract infection (usually asymptomatic), 5% to 15% of cases of endocarditis, and rare cases of meningitis. Their role in polymicrobial infection in the abdomen and pelvis is difficult to assess. Ninety percent of enterococci are inhibited by 4 mg/L of penicillin G, by 2 mg/L of ampicillin, and by 6 mg/L of vancomycin. The penicillinase-resistant penicillins, cephalosporins, carbenicillin, and ticarcillin are at least fourfold less active against enterococci than penicillin G, whereas piperacillin has activity equivalent to penicillin G. The addition of an aminoglycoside to penicillin, ampicillin, vancomycin or piperacillin—which are not bactericidal against most strains of enterococci—results in more rapid and complete bactericidal activity (ie, synergistic activity). (<i>Arch Intern Med</i>1982;142:2006-2009)

An Experimental Study of the Neisser-Wechsberg Phenomenon

(1) The inhibiting phenomenon of Neisser and Wechsberg, as frequently observed with bacteriolytic sera, can also be shown to occur with haemolytic sera.(2) This phenomenon develops early during immunisation, when it is very marked; but as immunisation proceeds it tends to disappear.(3) In sera examined some time after their removal the inhibiting faculty is seen to disappear first, before any marked change is noticed in its bactericidal titre. This can be shown to occur in vivo also.(4) The inhibiting faculty is observed only with inactivated sera; fresh and active sera showing complete bactericidal activity at all times. The effects are not however due to complementoids produced by inactivation.(5) The phenomenon is not due to the action of any of the known anti bodies, or special “inhibiting antibodies”; but it is due probably to dis sociation of the antigen-amboceptor complex. Such dissociation only occurs when amboceptors are present in excess. This explains why inhibition occurs only with high doses of an immune serum.The serum to be used should be without an antiseptic. Commercially prepared antisera usually contain a small amount of it. It is shown that corpuscles sensitised in them undergo haemolysis without the addition of complement (see p. 427).(6) Since it is known that the union of antigen and amboceptor is not always a firm one, it is suggested that during early days of immunisation amboceptors of a weak combining affinity are produced. These are replaced later by those which are capable of a more permanent union with them (antigens).(7) The name “complement-blocking” is not an appropriate one, as com plement could be shown to exist free in the inhibiting fluids. It should rather be spoken of as an “amboceptor-dissociation” effect.(8) Inhibition is specific. An attempt was made to utilise this fact in differ entiation of strains of true cholera but it was found to have no definite diagnostic value.The writer wishes to express his indebtedness to Prof. Hewlett for sug gesting the problem to him and also for his kind guidance and encouragement during the course of the experiments. His thanks are also due to Dr Taylor for his valuable assistance.