Bactericidal antibiotic-phytochemical combinations against methicillin resistant Staphylococcus aureus

Methicillin resistant Staphylococcus aureus (MRSA) infection is a global concern nowadays. Due to its multi-drug resistant nature, treatment with conventional antibiotics does not assure desired clinical outcomes. Therefore, there is a need to find new compounds and/or alternative methods to get arsenal against the pathogen. Combination therapies using conventional antibiotics and phytochemicals fulfill both requirements. In this study, the efficacy of different phytochemicals in combination with selected antibiotics was tested against 12 strains of S. aureus (ATCC MRSA 43300, ATCC methicillin sensitive S. aureus or MSSA 29213 and 10 MRSA clinical strains collected from National University Hospital, Singapore). Out of the six phytochemicals used, tannic acid was synergistic with fusidic acid, minocycline, cefotaxime and rifampicin against most of strains tested and additive with ofloxacin and vancomycin. Quercetin showed synergism with minocycline, fusidic acid and rifampicin against most of the strains. Gallic acid ethyl ester showed additivity against all strains in combination with all antibiotics under investigation except with vancomycin where it showed indifference effect. Eugenol, menthone and caffeic acid showed indifference results against all strains in combination with all antibiotics. Interestingly, no antagonism was observed within these interactions. Based on the fractional inhibitory concentration indices, synergistic pairs were further examined by time-kill assays to confirm the accuracy and killing rate of the combinations over time. The two methods concurred with each other with 92% accuracy and the combinatory pairs were effective throughout the 24 hours of assay. The study suggests a possible incorporation of effective phytochemicals in combination therapies for MRSA infections.

Occurrence of methicillin resistant Staphylococcus aureus (MRSA) among clinical samples in tehran-iran and its correlation with polymorphism of specific accessory gene regulator (AGR) groups

Methicillin-Resistant Staphylococcus aureus (MRSA) is responsible for an increasing number of serious hospital and community acquired infections. Virulence gene expression in Staphylococcus aureus is orchestrated by regulators such as the accessory gene regulator (agr). Staphylococcal strains are divided into four major agr groups (agrI-IV) on the basis of agrD and agrC polymorphisms. The purpose of this study was to define the prevalence of MRSA strains in appointed Tehran's hospitals and then to define and compare the proportion of agr I, II, III, IV polymorphisms between MRSA and Methicillin Sensitive Staphylococcus aureus (MSSA) strains. A total of 235 isolates were evaluated by conventional antibiotic susceptibility tests and PCR for agr and mecA genes. 112 strains were MRSA (47.5%) and the most prevalent agr specific group was agr I followed by agr III, agr II and agr IV, respectively. The prevalence of agr groups amongst MRSA and MSSA strains was not statistically significant (P>0.05). This study suggests that agr I is not only the most prevalent agr type in MRSAs but also the most common one in Methicillin Sensitive Staphylococcus aureus (MSSA) strains in Iran.

Evaluation of the in vitro antimicrobial activity of an ethanol extract of Brazilian classified propolis on strains of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is one of the most frequent causes of hospital acquired infections. With the increase in multiple drug resistant strains, natural products such as propolis are a stratagem for new product discovery. The aims of this study were: to determine the in vitro antimicrobial activity of an ethanol extract of propolis; to define the MIC50 and MIC90 (Minimal Inhibitory Concentration - MIC) against 210 strains of S. aureus; to characterize a crude sample of propolis and the respective ethanol extract as to the presence of predetermined chemical markers. The agar dilution method was used to define the MIC and the high performance liquid chromatography (HPLC) method was used to characterize the samples of propolis. MIC results ranged from 710 to 2,850 µg/mL. The MIC50 and MIC90 for the 210 strains as well as the individual analysis of American Type Culture Collection (ATCC) strains of Methicillin-susceptible Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) were both 1,420 µg/mL. Based on the chromatographic analysis of the crude sample and ethanol extracted propolis, it was concluded that propolis was a mixture of the BRP (SP/MG) and BRP (PR) types. The results obtained confirm an antimicrobial activity in relation to the strains of the S. aureus tested.

Detection of methicillin resistance and slime factor production of Staphylococcus aureus in bovine mastitis / Detecção de resistência a meticilina e produção do fator slime por Staphylococcus aureus em mastite bovina

This study aimed to detect methicillin resistant and slime producing Staphylococcus aureus in cases of bovine mastitis. A triplex PCR was optimized targetting 16S rRNA, nuc and mecA genes for detection of Staphylococcus species, S. aureus and methicillin resistance, respectively. Furthermore, for detection of slime producing strains, a PCR assay targetting icaA and icaD genes was performed. In this study, 59 strains were detected as S. aureus by both conventional tests and PCR, and 13 of them were found to be methicillinresistant and 4 (30.7%) were positive for mecA gene. Although 22 of 59 (37.2%) S. aureus isolates were slimeproducing in Congo Red Agar, in PCR analysis only 15 were positive for both icaA and icaD genes. Sixteen and 38 out of 59 strains were positive for icaA and icaD gene, respectively. Only 2 of 59 strains were positive for both methicillin resistance and slime producing, phenotypically, suggesting lack of correlation between methicillin resistance and slime production in these isolates. In conclusion, the optimized triplex PCR in this study was useful for rapid and reliable detection of methicillin resistant S. aureus. Furthermore, only PCR targetting icaA and icaD may not sufficient to detect slime production and further studies targetting other ica genes should be conducted for accurate evaluation of slime production characters of S. aureus strains.

Este estudo objetivou a detecção de Staphylococcus aureus resistente a meticilina e produtor do fator slime em casos de mastite bovina. Um PCR triplex foi otimizado, com alvo no genes 16SrRNA, nuc e mecA para detecção de Staphylococcus spp, S. aureus e resistencia a meticilina, respectivamente. Para detecção das cepas produtoras do fator slime, empregou-se um PCR com alvo nos genes icaA e icaD. No estudo, 59 cepas foram identificadas como S. aureus por testes convencionais e PCR, sendo 13 resistentes a meticilina e quatro positivas para o gene mecA. Embora 22 das 59 cepas tenham sido produtoras do fator slime em Agar Vermelho Congo, no teste PCR somente 15 foram positivas para os genes icaA e icaD. Dezesseis e 38 das 59 cepas foram positivas para os genes icaA e icaD, respectivamente. Somente duas das 59 cepas foram positivas simultaneamente para resistência a meticilina e produção do fator slime, sugerindo falta de correlação entre estas características. Em conclusão, o PCR triplex otimizado neste trabalho mostrou-se ser um método rápido e confiável para detecção de S.aureus meticilina resistente. Por outro lado, somente PCR para os genes icaA e icaD pode não ser suficiente para detectar produção de fator slime e outros estudos com alvo em outros genes ica são necessários para um avaliação correta da produção do fator slime por S. aureus.

Simultaneous determination of nafcillin and methicillin by different fluorimetric techniques using partial least-squares calibration.

The simultaneous determination of nafcillin and methicillin was accomplished by constant wavelength synchronous fluorimetry, in combination with partial least-squares multivariate calibration. The total luminescence information of the compounds was used to optimize the spectral data set to perform the calibration. A calibration set of standard samples was designed by combination of a factorial design, with three levels for each factor, and a central composite design. A comparative study of the results obtained using the excitation, the emission, the constant wavelength synchronous and the constant energy synchronous spectral data as analytical signals was performed. The data, set composed of the constant wavelength synchronous spectra, was selected as the analytical signal. The method was successfully applied to the determination of nafcillin and methicillin in mixtures.

New rapid assay for methicillin by spectrofluorimetry in pharmaceutical dosage forms.

A method for the spectrofluorimetric determination of methicillin is proposed (lambda ex = 279 nm, lambda em = 379 nm), for concentrations between 0.030 and 10.0 micrograms ml-1. The method was performed in water, at pH 6.20 provided by addition of phosphate buffer solution. The values obtained for detection and determination limits were 0.0188 and 0.063 micrograms ml-1, respectively. The method was successfully applied to assay a commercial injection containing methicillin sodium monohydrate.

Concentrations of methicillin in blood, normal milk and mastitic milk of cows after intramuscular injection of methicillin and tamethicillin.

Tamethicillin (TAM) is a basic ester pro-drug of methicillin (MET) which is converted in the body by non-specific esterases to MET. Equal doses of MET and TAM were administered intramuscularly in a crossover trial involving four dairy cows. Acute mastitis was induced in each cow by infusing two quarters of the udder with Escherichia coli endotoxin 3 h before antibiotic administration. Peak serum MET concentrations after MET injection were significantly (P less than 0.001) higher than peak serum drug concentrations after TAM injection. The t1/2 of MET in serum after MET and TAM treatments were 18 min and 2 h, respectively. Normal milk MET concentrations during the first 8 h after TAM administration were significantly (P less than 0.05) higher than after MET treatment. Mastitic milk MET concentrations during the period 2-6 after MET injection were significantly (P less than 0.01) higher than after TAM administration. However, MET concentrations which were equal to or higher than the minimal inhibitory concentrations for penicillin G-resistant staphylococci were maintained in the mastitic milk for 8 h after treatment with MET and TAM.

Penetration of nafcillin, methicillin, and cefazolin into human brain tissue.

To determine the penetration of the antistaphylococcal antibiotics, nafcillin, methicillin, and cefazolin, into brain tissue, we gave to each of 27 patients undergoing craniotomy and brain biopsy one of the antibiotics in a 2-g intravenous infusion just before operation. At the time of brain tissue removal (30 to 225 minutes after the start of the infusion), a serum specimen was obtained, and tissue and serum were assayed for antibiotic concentration. Eleven of 13 brain specimens contained detectable nafcillin concentrations between 0.36 and 11 micrograms/g of tissue (mean, 2.7 micrograms/g for all 13 specimens). Fourteen of 18 brain tissue specimens contained detectable methicillin concentrations between 0.56 and 5.0 micrograms/g of tissue (mean, 2.0 micrograms/g for all 18 specimens). Ten of 11 brain tissue specimens contained detectable cefazolin concentrations between 2.0 and 40 micrograms/g of tissue (mean, 10.6 micrograms/g for all 11 specimens). Each antibiotic penetrated "abnormal" brain tissue better than "relatively normal" brain tissue. Because nafcillin is more active against Staphylococcus aureus, we conclude that nafcillin is preferable to methicillin for the therapy of central nervous system staphylococcal infections. Cefazolin achieves higher brain tissue concentrations than the penicillins, but has not been clinically evaluated for the therapy of central nervous system infections.

Probenecid and intraocular methicillin.

Probenecid was given intravenously to rabbits in an effort to extend the intraocular longevity of intravitreal methicillin. With relatively high levels of probenecid, an insignificant elevation of half-life was obtained. Aqueous levels of methicillin were measured after intravitreal injection and were found to be adequate to inhibit penicillinase-producing S. aureus for approximately 20 hours.

Effect of local anesthetics on intraocular penetration of subconjunctival antibiotics.

The combination of the subconjunctival injection of lidocaine HCl or procaine HCl with the subconjunctival injection of penicillin G, methicillin, cephaloridine, or gentamicin did not influence their intraocular penetration or subsequent antibiotic activity in aqueous humor of experimental animals.

[Clinical and experimental parallels in studying the effect of chymotrypsin on the pharmacokinetics of antibiotics]. / Kliniko-éksperimental'nye paralleli pri izuchenii vliianiia khimotripsina na farmakokinetiku antibiotikov

The effect of intramuscular chimotripsin on the levels of methicillin and tetracycline administered respectively intramuscularly and orally was studied in patients with chronic pneumonia and in experimental rats. It was found that the dose of chimotripsin providing higher methicillin blood levels was many times lower than the enzyme doses providing analogous indices for the blood serum and organs of the rats. When the patients were treated with tetracycline and chimotripsin, increased blood levels of the antibiotic were observed. Administration of chimotripsin to the rats had no effect on tetracycline pharmacokinetics in the animals.

Antibiotic levels in pericardial fluid.

An experimental model was designed to study the ability of antibiotics to enter the pericardial compartment. Noninfected and infected pericardial fluid and serum antibiotic activities were determined in adult mongrel dogs before and at intervals after antibiotic administration. After the administration of penicillin G, methicillin, cephaloridine, streptomycin, or gentamicin, clinically adequate antibiotic levels in the noninfected pericardial fluid were obtained within 1 h, and these levels approached or exceeded the serum levels within 2-4 h. Antibiotic levels obtained from infected dog pericardial fluids were higher than those from noninfected animals. Patients' serum and pericardial fluid antibiotic levels were measured after penicillin G, penicillin V, cephalothin, and gentamicin administration. We have found, both in the canine and human studies, that pericardial antibiotic levels taken at least 2 h after antibiotic administration are almost identical to those in the blood.