Activity Of Antimicrobial Combinations Research Articles

Virtual Screening of Potential RoxS Inhibitors and Evaluation of Their Antimicrobial Activity in Combination with Antibiotics against Clinically Resistant Bacteria.

Pseudomonas aeruginosa with difficult-to-treat resistance has been designated as an urgent or serious threat by the CDC in the United States; therefore, novel antibacterial drugs and combination strategies are urgently needed. The sensor kinase RoxS is necessary for the aerobic growth of Pseudomonas aeruginosa. This study aimed to screen candidate RoxS inhibitors and evaluate their efficacy in treating multi-drug-resistant and extensively drug-resistant Pseudomonas aeruginosa in combination with meropenem and amikacin to identify promising combination strategies. RoxS protein structures were constructed using homology modeling and potential RoxS inhibitors, including Ezetimibe, Deferasirox, and Posaconazole, were screened from the FDA-approved ZINC drug database using molecular docking and molecular dynamics simulations. MIC and checkerboard assays were used to determine the in vitro antimicrobial efficacy of the three drugs in combination with antibiotics. The results of in vitro experiments showed an additive effect of 100 μg/mL Deferasirox or 16 μg/mL Posaconazole in combination with meropenem and a synergistic effect of 1.5 μg/mL Deferasirox and amikacin. In summary, these three drugs are potential inhibitors of RoxS, and their combination with meropenem or amikacin is expected to reverse the resistance of P. aeruginosa, providing new combination strategies for the treatment of clinically difficult-to-treat Pseudomonas aeruginosa.

Sodium benzoate and sodium bisulfate as preservatives in apple juice and alternative sanitizers for washing cherry tomatoes

Unpasteurized apple ciders and fresh produce have been linked to multistate outbreaks due to contamination by foodborne pathogens. Organic acids such as benzoic acid are effective antimicrobials, and acidified sodium benzoate (NaB) has been reported to be effective in reducing pathogens inoculated on cherry tomatoes and preventing cross-contamination. Sodium bisulfate (SBS) is a powerful acidulant but has not been studied in combination with NaB. The objective of the present study was to characterize the antibacterial activity of SBS and its combination with NaB in tryptic soy broth (TSB) and apple juice, as well as washing cherry tomatoes. The minimum inhibitory concentration and minimum bactericidal concentration of SBS were all 0.5% w/v (corresponding to TSB medium pH of 4.30) and 1.0% w/v (corresponding to TSB medium pH of 2.88), respectively, for Escherichia coli O157:H7 ATCC 43895, Salmonella Enteritidis ATCC 13076, and Listeria monocytogenes Scott A. In TSB, the triple combination of 1.0% w/v SBS, 0.1% w/v NaB, and 0.02% w/v oregano oil (OO) showed the faster inactivation rate of the three bacteria than treatments with one or two antimicrobials; the activity of double combinations followed the order of 0.1% w/v NaB +1.0% w/v SBS > 0.1% w/v NaB +0.5% w/v SBS + 0.02% w/v OO > 0.1% w/v NaB +0.5% w/v SBS. pH was a critical factor in the activity of antimicrobial combinations in TSB, and L. monocytogenes was more resistant than Gram-negative E. coli O157:H7 and S. Enteritis. In apple juice added with 0.05% w/v NaB, 0.25% w/v SBS, and 0.01% w/v OO alone or in combinations, 5 log CFU/mL or greater reductions in 72 h were observed for E. coli O157:H7 and S. Enteritidis in double and triple combinations, while only the triple combination and the SBS-OO combination resulted in the same effect for L. monocytogenes. For cherry tomatoes inoculated with 6.8 log CFU/g E. coli O157:H7, complete decontamination (>6 log CFU/g) was achieved after soaking for 1 min in solutions containing 0.5–1.5% w/v SBS and 0.1% w/v NaB or 1.5% w/v SBS alone, and no pathogens were detected in all wash solutions containing 0.5–1.5% w/v SBS with and without NaB. The lower pH of wash solutions with a higher amount of SBS was a dominant factor in decontamination and prevention of cross-contamination. The present study showed the potential of SBS and its combination with NaB to enhance the safety of apple juice and cherry tomatoes.

Structurally Related Liposomes Containing N-Oxide Surfactants: Physicochemical Properties and Evaluation of Antimicrobial Activity in Combination with Therapeutically Available Antibiotics.

Although liposomes are largely investigated as drug delivery systems, they can also exert a pharmacological activity if devoid of an active principle as a function of their composition. Specifically, charged liposomes can electrostatically interact with bacterial cells and, in some cases, induce bacterial cell death. Moreover, they also show a high affinity toward bacterial biofilms. We investigated the physicochemical and antimicrobial properties of liposomes formulated with a natural phospholipid and four synthetic l-prolinol-derived surfactants at 9/1 and 8/2 molar ratios. The synthetic components differ in the nature of the polar headgroup (quaternary ammonium salt or N-oxide) and/or the length of the alkyl chain (14 or 16 methylenes). These differences allowed us to investigate the effect of the molecular structure of liposome components on the properties of the aggregates and their ability to interact with bacterial cells. The antimicrobial properties of the different formulations were assessed against Gram-negative and Gram-positive bacteria and fungi. Drug–drug interactions with four classes of available clinical antibiotics were evaluated against Staphylococcus spp. The target of each class of antibiotics plays a pivotal role in exerting a synergistic effect. Our results highlight that the liposomal formulations with an N-oxide moiety are required for the antibacterial activity against Gram-positive bacteria. In particular, we observed a synergism between oxacillin and liposomes containing 20 molar percentage of N-oxide surfactants onStaphylococcus haemolyticus, Staphylococcus epidermidis, andStaphylococcus aureus. In the case of liposomes containing 20 molar percentage of the N-oxide surfactant with 14 carbon atoms in the alkyl chain for S. epidermidis, the minimum inhibitory concentration was 0.125 μg/mL, well below the breakpoint value of the antibiotic.

The Design of Alapropoginine, a Novel Conjugated Ultrashort Antimicrobial Peptide with Potent Synergistic Antimicrobial Activity in Combination with Conventional Antibiotics.

(1) Background: Antimicrobial resistance represents an urgent health dilemma facing the global human population. The development of novel antimicrobial agents is needed to face the rising number of resistant bacteria. Ultrashort antimicrobial peptides (USAMPs) are considered promising antimicrobial agents that meet the required criteria of novel antimicrobial drug development. (2) Methods: Alapropoginine was rationally designed by incorporating arginine (R), biphenylalanine (B), and naproxen to create an ultrashort hexapeptide. The antimicrobial activity of alapropoginine was evaluated against different strains of bacteria. The hemolytic activity of alapropoginine was also investigated against human erythrocytes. Finally, synergistic studies with antibiotics were performed using the checkerboard technique and the determination of the fractional inhibitory index. (3) Results: Alapropoginine displayed potent antimicrobial activities against reference and multi-drug-resistant bacteria with MIC values of as low as 28.6 µg/mL against methicillin-resistant S. aureus. Alapropoginine caused negligible toxicity toward human red blood cells. Moreover, the synergistic studies showed improved activities for the combined conventional antibiotics with a huge reduction in their antimicrobial concentrations. (4) Conclusions: The present study indicates that alapropoginine exhibits promising antimicrobial activity against reference and resistant strains of bacteria with negligible hemolytic activity. Additionally, the peptide displays synergistic or additive effects when combined with several antibiotics.

Protective Liquid Crystal Nanoparticles for Targeted Delivery of PslG: A Biofilm Dispersing Enzyme.

The glycoside hydrolase, PslG, attacks and degrades the dominant Psl polysaccharide in the exopolymeric substance (EPS) matrix of Pseudomonas aeruginosa biofilms and is a promising therapy to potentiate the effect of antibiotics. However, the need for coadministration with an antibiotic and the potential susceptibility of PslG to proteolysis highlights the need for an effective delivery system. Here, we compared liposomes versus lipid liquid crystal nanoparticles (LCNPs) loaded with PslG and tobramycin as potential formulation approaches to (1) protect PslG from proteolysis, (2) trigger the enzyme's release in the presence of bacteria, and (3) improve the total antimicrobial effect in vitro and in vivo in a Caenorhabditis elegans infection model. LCNPs were an effective formulation strategy for PslG and tobramycin that better protected the enzyme against proteolysis, triggered and sustained the release of PslG, improved the antimicrobial effect by 10-100-fold, and increased the survival of C. elegans infected with P. aeruginosa. Digestible LCNPs had the advantage of triggering the enzyme's release in the presence of bacteria. However, compared to nondigestible LCNPs, negligible differences arose between the LCNPs' ability to protect PslG from proteolysis and potentiate the antimicrobial activity in combination with tobramycin. In C. elegans, the improved antimicrobial efficacy was comparable to tobramycin-LCNPs, although the PslG + tobramycin-LCNPs achieved a greater than 10-fold reduction in bacteria compared to the unformulated combination. Herewith, LCNPs are showcased as a promising protective delivery system for novel biofilm dispersing enzymes combined with antibiotics, enabling infection-directed therapy and improved performance.

Chitosan nanoemulsions of cold-pressed orange essential oil to preserve fruit juices

Sweet orange essential oil is obtained from the peels of Citrus sinensis (CSEO) by cold pressing, and used as a valuable product by the food industry. Nanoencapsulation is known as a valid strategy to improve chemical stability, organoleptic properties, and delivery of EO-based products. In the present study we encapsulated CSEO using chitosan nanoemulsions (cn) as nanocarrier, and evaluated its antimicrobial activity in combination with mild heat, as well as its sensorial acceptability in orange and apple juices. CSEO composition was analyzed by GC–MS, and 19 components were identified, with limonene as the predominant constituent (95.1%). cn-CSEO was prepared under low shear conditions and characterized according to droplet size (<60 nm) and polydispersity index (<0.260 nm). Nanoemulsions were stable for at least 3 months at 4 ± 2 °C. cn-CSEO were compared with suspensions of CSEO (s-CSEO) (0.2 μL of CSEO/mL) in terms of antibacterial activity in combination with mild heat (52 °C) against Escherichia coli O157:H7 Sakai. cn-CSEO displayed a greater bactericidal activity than s-CSEO at pH 7.0 and pH 4.0. The validation in fruit juices showed an improved bactericidal effect of cn-CSEO in comparison with s-CSEO when combined with mild heat in apple juice, but not in orange juice. In both juices, the combination of CSEO and mild heat exerted synergistic lethal effects, reducing the treatment time to cause the inactivation of up to 5 Log10 cycles of E. coli O157:H7 Sakai cells. Finally, the sensory characteristics of both juices were acceptable either when using s-CSEO or CSEO nanoemulsified with chitosan. Therefore, as a promising carrier for lipophilic substances, the encapsulation of EOs with chitosan nanoemulsions might represent an advantageous alternative when combined with mild heat to preserve fruit juices.

Antimicrobial activity of Apis mellifera L. and Trigona sp. propolis from Nepal and its phytochemical analysis

In this study, we evaluated antimicrobial activity, antimicrobial activity in combination with antibiotics, and chemical composition of Nepalese propolis 70% ethanolic extracts. Propolis originated from two genera of bees – Apis mellifera L. and Trigona sp. HPLC-DAD-MS/MS analyses revealed that the composition of both extracts was almost the same and the main components were flavonoid aglycones (mainly neoflavonoids, isoflavonoids) and pterocarpans. The highest antibacterial activity (disc diffusion test) was observed against Helicobacter pylori, Staphylococcus aureus and Shigella flexneri. Antibiotics exhibited synergism with Apis mellifera L. and Trigona sp. propolis against S. aureus and the strongest effect was observed for the combination with amikacin and tetracycline. Moreover, Nepalase propolis inhibited filamentation of C. albicans and caused oxidative stress by production of the superoxide anion radical (O2−) and a lower concentration of the hydroxyl radical (OH).Propolis extracts are potent antibacterial agents and may be used in combination with antibiotics.

Impact of pH on the activity of co-used antimicrobials against resistant Escherichia coli strains of animal origin

In this study, combination antimicrobial therapy, due to its higher potential against resistant bacteria, was evaluated for the inhibition of multidrug-resistant E. coli strains. The influence of pH as an environmental variable on the activity of antimicrobial combinations was evaluated by calculating the factional concentration indexes at pH values 5.0, 6.0, 7.3, and 8.0. The highest synergistic activity rates of ceftriaxone + colistin, danofloxacin + colistin, danofloxacin + ceftiofur, and ceftiofur + gentamicin combinations were 50%, 33%, 100%, and 50%, respectively measured at ≥7.3 pH. The lowest synergistic activity rates for all combinations were observed at the acidic pH values of 5.0 and 6.0. The results of this study clearly demonstrated that acidic pH of the medium impaired the activity of the antimicrobial combinations. Although ceftriaxone and ceftiofur exert optimal activity at acidic pH values, the synergistic activity of the co-used drugs reached its highest level at pH ≥7.3.

A peppermint oil emulsion stabilized by resveratrol-zein-pectin complex particles: Enhancing the chemical stability and antimicrobial activity in combination with the synergistic effect

The combination of different antimicrobial agents might produce synergistic effects and has gained increasing interest. Interfacial engineering of emulsion systems has been developed to co-encapsulate and protect bioactive components with different solubility. In this study, peppermint oil and resveratrol display synergistic effect against the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Salmonella Typhimurium. Partially wettable resveratrol-loaded zein-pectin complex particles with a three-phase contact angle of ~78° were fabricated via a desolvation method. Peppermint oil emulsions with the co-inclusion of resveratrol were successfully prepared by zein-pectin complex particles, showing a high encapsulation efficiency for peppermint oil (~88%) and resveratrol (~99%). Addition of pectin decreased size distribution of the emulsions, improved antimicrobial activity, physical and chemical stability and prolonged antimicrobial efficiency against Staphylococcus aureus and Salmonella Typhimurium. Overall, the current study may have a valuable contribution to develop an efficient antimicrobial system based on the synergistic effect of combined agents and a single emulsion stabilized by protein-polysaccharide complex particles.

Characterization and Synergistic Antimicrobial Evaluation of Lipopeptides from Bacillus amyloliquefaciens Isolated from Oil-Contaminated Soil.

Lipopeptides show great potential for biomedical application. Several lipopeptides exhibit narrow and broad-spectrum inhibition activities. The aim of the study is to characterize the lipopeptides produced by B. amyloliquefaciens strain MD4-12 and evaluate the synergistic antimicrobial activity in combination with a conventional antibiotic against Gram-negative bacteria. B. amyloliquefaciens strain MD4-12 was isolated from oil-contaminated soil. The isolate was cultivated in McKeen medium, and the lipopeptides were isolated by precipitation and extraction with methanol. Characterization of the lipopeptides by ESI-MS gave nine mass ion peaks with m/z 994–1072, resulted from protonating of the main ions in [M + H]+ and [M + Na]+ ion form. These mass ion peaks attributed to surfactin homologs. By tandem mass spectrometry, five variants of surfactin with the same amino acid sequence in peptide moiety could be revealed. The peptide moiety contains seven amino acids identified as Glu-Leu/Ile-Leu-Val-Asp-Leu-Leu/Ile while the fatty acid moiety comprises a different length of chain from C12 to C16. Surfactin showed antibacterial activity against various Gram-positive and Gram-negative bacteria. Combination surfactin with ampicillin showed a synergistic effect against P. aeruginosa ATCC 27853.

Wound Pathogens: Investigating Antimicrobial Activity of Commercial Essential Oil Combinations against Reference Strains.

This study aimed to determine the antimicrobial activity of 247 essential oil combinations against the reference strains of wound pathogens. Essential oil combinations were investigated for antimicrobial activity against five pathogens. The minimum inhibitory concentration (MIC) assay was used and the fractional inhibitory concentration index (ΣFIC) calculated to determine interactions between selected oils. Twenty-six combinations displayed broad-spectrum antimicrobial activity against all five reference strains and several displayed synergy against more than one pathogen. The combination of Santalum austrocaledonicum (sandalwood) with Commiphora myrrha (myrrh) displayed noteworthy antimicrobial activity against all five reference strains and synergy against four (MIC values 0.03-1.00 mg/ml and ΣFIC values 0.19-1.00 mg/ml) pathogens. No antagonism was observed. Santalum spp. and Vetiveria zizanioides essential oils contributed the most to antimicrobial activity in combination. Essential oil combinations are presented as a viable option in wound therapy.

Activity of antimicrobial combinations against KPC-2-producing Klebsiella pneumoniae in a rat model and time-kill assay.

This study evaluated the efficacy of tigecycline (TIG), polymyxin B (PMB), and meropenem (MER) in 80 rats challenged with Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae infection. A time-kill assay was performed with the same strain. Triple therapy and PMB+TIG were synergistic, promoted 100% survival, and produced negative peritoneal cultures, while MER+TIG showed lower survival and higher culture positivity than other regimens (P = 0.018) and was antagonistic. In vivo and in vitro studies showed that combined regimens, except MER+TIG, were more effective than monotherapies for this KPC-producing strain.

Nontuberculous mycobacterial ocular infections--comparing the clinical and microbiological characteristics between Mycobacterium abscessus and Mycobacterium massiliense.

PurposeTo analyze the clinical characteristics of nontuberculous mycobacterial (NTM) ocular infections and the species-specific in vitro antimicrobial susceptibility.Material and MethodsIn 2000 to 2011 at the National Taiwan University Hospital, multilocus sequencing of rpoB, hsp65 and secA was used to identify NTM isolates from ocular infections. The clinical presentation and treatment outcomes were retrospectively compared between species. Broth microdilution method was used to determine the minimum inhibitory concentrations of amikacin (AMK), clarithromycin (CLA), ciprofloxacin (CPF), levofloxacin (LVF), moxifloxacin (MXF) and gatifloxacin (GAF) against all strains. The activities of antimicrobial combinations were assessed by the checkerboard titration method.ResultsA total of 24 NTM strains (13 Mycobacterium abscessus and 11 Mycobacterium massiliense) were isolated from 13 keratitis, 10 buckle infections, and 1 canaliculitis cases. Clinically, manifestations and outcomes caused by these two species were similar and surgical intervention was necessary for medically unresponsive NTM infection. Microbiologically, 100% of M. abscessus and 90.9% of M. massiliense ocular isolates were susceptible to amikacin but all were resistant to fluoroquinolones. Inducible clarithromycin resistance existed in 69.3% of M. abscessus but not in M. massiliense isolates. None of the AMK-CLA, AMK-MXF, AMK-GAF, CLA-MXF and CLA-GAF combinations showed synergistic or antagonistic effect against both species in vitro.Conclusions M. abscessus and M. massiliense are the most commonly identified species for NTM ocular infections in Taiwan. Both species were resistant to fluoroquinolones, susceptible to amikacin, and differ in clarithromycin resistance. Combined antimicrobial treatments showed no interaction in vitro but could be considered in combination with surgical interventions for eradication of this devastating ocular infection.

Combination therapy in severe Acinetobacter baumannii infections: an update on the evidence to date.

Acinetobacter baumannii is a drug-resistant Gram-negative pathogen increasingly causing hospital-acquired infections in critically ill patients. In this review, we summarize the current mechanisms of antimicrobial resistance in A. baumannii and describe in detail recent in vitro and in vivo experimental data on the activity of antimicrobial combinations against this microorganism. We then introduce the rationale for the use of combination antibiotic therapy in resistant A. baumannii infections. Finally, we present and critically discuss both uncontrolled clinical studies and the few randomized clinical trials of combination antimicrobial therapy for these infections, with a special focus on ongoing multinational trials and optimal approach to future research in this field.

In vitro activities of antimicrobial combinations against clinical isolates of Neisseria gonorrhoeae

The Centers for Disease Control and Prevention (CDC) now recommend combination therapy with ceftriaxone 250 mg plus azithromycin (AZM) 1 g as a first-line regimen for gonorrhea because the increase of Neisseria gonorrhoeae resistant to multiple antimicrobial agents. However, reports on the in vitro activity of antimicrobial combinations against clinical isolates of N. gonorrhoeae are very rare. In the present study, a checkerboard method was utilized to examine the in vitro activity of ceftriaxone (CTRX), cefodizime (CDZM), spectinomycin (SPCM), or gentamicin (GM) in combination with AZM against 25 clinical isolates of N. gonorrhoeae. The SPCM + AZM combination demonstrated the lowest mean fractional inhibitory concentration index (FICI) of 0.69, followed by the CDZM + AZM combination (mean FICI, 0.75), the CTRX + AZM combination (mean FICI, 0.81), and the GM + AZM combination (mean FICI, 0.83). Additivity/indifference effect was detected for the SPCM + AZM combination, the CDZM + AZM combination, the CTRX + AZM combination, and the GM + AZM combination, against 96%, 72%, 92%, and 100% of the isolates, respectively. There was no antagonism for any of the antimicrobial combinations against the 25 N. gonorrhoeae isolates. These results suggest that the antimicrobial combinations may be worthy of clinical evaluation as an alternative regimen for gonococcal infections caused by antimicrobial-resistant strains.

Different activities of antimicrobial combinations against multidrug resistant Acinetobacter baumanniiin vitro

Objective To evaluate the activities of 18 pairs of antimicrobials combinations against non - duplicate clinical isolates of multidrug resistant Acinetobacter baumanrrii （MDRAB） in vitro . Methods Collect isolates of Acinetobacter baumannii from different patients from October 2009 to May 2010, which were isolated in Clinical Laboratory Center of Beijing Friendship Hospital, Capital Medical University. Use broth microdilution method to detect MIC of mono-antimicrobial, and checkerboard broth microdilution method to detect combinatied MIC, and calculate fractional inhibitory concentration （FIC） index to determine drug combinations effects. When the performance of the same drug combinations conflicted, appropriate strains were selected for screening of drug-resistant mechanisms by polymerase chain reaction（PCR） , including effiux pump genes. Results In tests in vitro, rifampicin and polymyxin B, imipenem and gentamicin, cefepime and levofloxacin showed synergy at high proportion, 68.1% , 45.5% , 40.9% , respectively. Minocycline and rifampicin, ampicillin/sulbactam and tobramycin. Ceftazidime and ciprofloxacin showed additive effect at high proportion, 81.8% , 68.2% , 68.2% , respectively. There were several combinations which appeared the opposite effects to tested strains. Strains No. 19 corresponding reaction was synergy and No. 21, No. 26 corresponding reactions were antagonism. The three strains above were selected for screening resistant mechanisms. The difference is that genotypes of adeS were negative in No. 19 and positive in No. 21 and No. 26. Conclusion Rifampicin and polymyxin B combination showed synergy against the MDRAB in vitro, which can be considered as the treatment choice for critical infections caused by MDRAB. Imipenem and gentamicin, cefepime and levofloxacin also showed synergy in vitro, but in some isolates showed antagonism. This phenomenon may be due to the gene adeS activated by certain antibiotics, and the activated adeSdrived efflux pump express or overexpress, which made the drugs in bacterial ceils pumped out,causing antagonistic effect. The individual differences in strains should be considered when clinic strain apply these two combinations above. Key words: Multi-drug resistant Acinetobacter baumannii; Antimicrobial combination

Synthesis of silver and copper nanoparticle containing a-C:Hby ion irradiation of polymers

One of the many applications of diamond like carbon (DLC) is the biocompatible coating of medical tools and implants. The most recent field of interest concerns the generation of antimicrobial activity in combination with the excellent wear resistance and biocompatibility of DLC. As has already been shown for polymers, nanoparticles of silver or copper within a carbonacious matrix have a bactericidal effect. In this work we describe a new technique to produce amorphous hydrogenated carbon films (a-C:H), which contain nanometer sized clusters of silver or copper. The hybrid deposition process is based on sol–gel synthesis of polymer films and subsequent ion-induced densification and cross-linking to form a-C:H. By thermal or UV-induced reduction of metal salts in polymer solution, colloidal metal particles are produced. In this way polymer films, already containing noble metal nanoclusters, can be deposited in a wet chemical step. Upon sol–gel deposition, the polymer is subjected to ion irradiation. Based on earlier results, the influence of ion energy on chemical and mechanical properties, as well as bonding structure is investigated. Special attention is also dedicated to ion-induced diffusion and growth as well as oxidation effects.

Antimicrobial and diffusional correlation of N‐alkyl betaines and N‐alkyl‐N,N‐dimethylamine oxides from semisolids

Previous studies have shown that two classes of amphoteric surfactants, N‐alkyl betaines and N‐alkyl‐N,N‐dimethylamine oxides, exhibit pronounced antimicrobial activity in combination and have potential for use in a semisolid formulation for topical or vaginal delivery. In this work, several potential delivery systems were prepared and evaluated for antimicrobial activity and diffusional properties. A novel antimicrobial test for semisolids was proposed that determined the contact time needed to kill microorganisms. The unformulated agents in solution exhibited the faster kill within 60 min, followed by the hydroxyethylcellulose gel formulation in 90 min, and the poloxamer gel and a cream that required several hours. Diffusion from the dosage form utilized a Slide‐A‐Lyzer diffusion cassette with a 10,000 MWCO membrane with 14C‐labeled active species added to the aforementioned antimicrobial formulations. Diffusion of the individual betaine and amine oxide derivatives were tracked over time to determine the diffusion rates and profiles of the components in each formulation and in solution. The betaine derivative diffused up to three times faster than the amine oxide derivative within the first 2 h, but the amount diffused was approximately equivalent at 24 h. The formulations delayed release in the same rank order as the contact time kill analysis: hydroxyethylcellulose gel > poloxamer gel > cream. © 2001 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1386–1394, 2001

Antimicrobial mixtures used by tissue banks for harvested skin: comparative in vitro activity

The activities of antimicrobial combinations from three geographically diverse skin/tissue banks used in the processing of skin/tissue were compared using bacteria and yeast isolated from burn patients. All formulations showed 90% or more effectiveness against bacteria generally susceptible to antibiotics but were less effective (60–80%) when tested against bacteria resistant to specific antimicrobials. Anti-yeast activity was present when an appropriate antifungal agent was included in the combination. All formulations were stable for at least six weeks. Results of this study raise certain questions about the use of these antimicrobial combinations in contemporary skin/tissue banking and point the way toward areas for future study.

Antimicrobial properties of hydrogen peroxide and sodium bicarbonate individually and in combination against selected oral, gram-negative, facultative bacteria.

The topical application of hydrogen peroxide (H2O2) and sodium bicarbonate (NaHCO3), individually and in combination, has been used empirically in the treatment of periodontal diseases. In this study, we examined both minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of these disinfectants individually and in combination against selected facultative, Gram-negative oral bacteria in a microtiter dilution assay. The bacteria studied included Actinobacillus actinomycetemcomitans, Haemophilus aphrophilus, Eikenella corrodens, and Capnocytophaga gingivalis. These bacteria exhibited MBC (one hr) values ranging from 75 mumol/L to greater than 10 mmol/L and MIC from less than 5 to 500 mumol/L for H2O2. The tested bacteria exhibited MIC values for NaHCO3 of from 23 to 182 mmol/L, and the MBC (one hr) exceeded 728 mmol/L for most of the strains examined. At sublethal (sub-MIC) concentrations, sodium bicarbonate antagonized the ability of H2O2 to inhibit bacterial growth in MIC assays, but sublethal concentrations of H2O2 had no effect on the MIC values of NaHCO3. Lethal concentrations of H2O2 and NaHCO3 exhibited synergistic antimicrobial activity in combination in one-hour bactericidal assays. Since the bactericidal properties of these antimicrobial agents are synergistic, we conclude that it may be rational to use them in combination to treat certain forms of periodontal disease. Also, lower and perhaps safer concentrations of H2O2 can be used in combination with NaHCO3 when oxidative antimicrobial chemotherapy is indicated.