Antibacterial activity of α-mangostin against vancomycin resistant Enterococci (VRE) and synergism with antibiotics

alpha-Mangostin, isolated from the stem bark of Garcinia mangostana L., was found to be active against vancomycin resistant Enterococci (VRE) and methicillin resistant Staphylococcus aureus (MRSA), with MIC values of 6.25 and 6.25 to 12.5 microg/ml, respectively. Our studies showed synergism between alpha-mangostin and gentamicin (GM) against VRE, and alpha-mangostin and vancomycin hydrochloride (VCM) against MRSA. Further studies showed partial synergism between alpha-mangostin and commercially available antibiotics such as ampicillin and minocycline. These findings suggested that alpha-mangostin alone or in combination with GM against VRE and in combination with VCM against MRSA might be useful in controlling VRE and MRSA infections.     

Antimicrobial activity of mupirocin, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline against vancomycin-resistant enterococci (VRE) from clinical isolates in Korea (1998 and 2005)

It is a hot clinical issue whether newly approved antimicrobial agents such as daptomycin, linezolid, quinupristin/dalfopristin (synercid) and tigecycline are active enough to be used for infections caused by vancomycin resistant bacteria. We performed susceptibility tests for mupirocin, which is in widespread clinical use in Korea, and four new antimicrobials, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline, against vancomycin-resistant Enterococcus faecalis and Enterococcus faecium isolated from Korean patients in 1998 and 2005 to evaluate and compare the in vitro activity of these antimicrobials. Among these agents, quinupristin/dalfopristin, which is rarely used in hospitals in Korea, showed relatively high resistance to several vancomycin-resistant enterococci (VRE) isolated in 2005. Likewise, daptomycin, linezolid and tigecycline have not yet been in clinical use in Korea. However, our results showed that most of the 2005 VRE isolates were already resistant to linezolid and daptomycin (highest minimum inhibitory concentration (MIC) value >100 microg/ml). Compared with the other four antimicrobial agents tested in this study, tigecycline generally showed the greatest activity against VRE. However, four strains of 2005 isolates exhibited resistance against tigecycline (MIC >12.5 microg/ml). Almost all VRE were resistant to mupirocin, whereas all E. faecium isolated in 1998 were inhibited at concentrations between 0.8 to approximately 1.6 microg/ml. In conclusion, resistances to these new antimicrobial agents were exhibited in most of VRE strains even though these new antibiotics have been rarely used in Korean hospitals.     

Design and synthesis of benzenesulfonanilides active against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus

Vancomycin is mainly used as an antibacterial agent of last resort, but recently vancomycin-resistant bacterial strains have been emerging. Although new antimicrobials have been developed in order to overcome drug-resistant bacteria, many are structurally complex beta-lactams or quinolones. In this study, we aimed to create new anti-drug-resistance antibacterials which can be synthesized in a few steps from inexpensive starting materials. Since sulfa drugs function as p-aminobenzoic acid mimics and inhibit dihydropteroate synthase (DHPS) in the folate pathway, we hypothesized that sulfa derivatives would act as folate metabolite-mimics and inhibit bacterial folate metabolism. Screening of our sulfonanilide libraries, including benzenesulfonanilide-type cyclooxygenase-1-selective inhibitors, led us to discover benzenesulfonanilides with potent anti-methicillin-resistant Staphylococcus aureus (MRSA)/vancomycin-resistant Enterococcus (VRE) activity, that is, N-3,5-bis(trifluoromethyl)phenyl-3,5-dichlorobenzenesulfonanilide (16b) [MIC=0.5microg/mL (MRSA), 1.0microg/mL (VRE)], and 3,5-bis(trifluoromethyl)-N-(3,5-dichlorophenyl)benzenesulfonanilide (16c) [MIC=0.5microg/mL (MRSA), 1.0microg/mL (VRE)]. These compounds are more active than vancomycin [MIC=2.0microg/mL (MRSA), 125microg/mL (VRE)], but do not possess an amino group, which is essential for DHPS inhibition by sulfa drugs. These results suggested that the mechanism of antibacterial action of compounds 16b and 16c is different from that of sulfa drugs. We also confirmed the activity of these compounds against clinical isolates of Gram-positive bacteria.     

Antimicrobial and cytotoxic activities of neolignans from Magnolia officinalis

In the light of the steady increase of infections related to vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA), the medicinal plant Magnolia officinalis was subjected to bioassay-directed fractionation, which led to the isolation of the known neolignans piperitylmagnolol (1), magnolol (2), and honokiol (3) from the MeOH extract. In broth-microdilution assays, 1-3 exhibited antibacterial activities against VRE and MRSA at minimum-inhibitory concentrations (MIC) in the range of 6.25-25 microg/ml, compound 1 being the most-potent antibiotic. The ratio of MBC/MIC (MBC = minimum bactericidal concentration) was < or = 2 for all compounds. The kinetics of the antibacterial action of 1 and 3 were studied by means of time-kill assays; both compounds were bactericidal against VRE and MRSA, their actions being time dependent, or both time and concentration dependent. Magnolol (2) was acetylated to magnolol monoacetate (4) and magnolol diacetate (5) (partial or full masking of the phenolic OH functions). The cytotoxic properties of 1-5 against human OVCAR-3 (ovarian adenocarcinoma), HepG2 (hepatocellular carcinoma), and HeLa (cervical epitheloid carcinoma) cell lines were evaluated. The CD50 values for compounds 1-3 were in the range of 3.3-13.3 microg/ml, derivatives 4 and 5 being much less potent. This study indicates that piperitylmagnolol (= 3-[(1S,6S)-6-isopropyl-3-methylcyclohex-2-enyl]-5,5'-di(prop-2-enyl)[1,1'-biphenyl]-2,2'-diol; 1) possesses both significant anti-VRE activity and moderate cytotoxicity against the above cancer cell lines.     

Synergistic effects of the combination of galangin with gentamicin against methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis>

The antimicrobial killing activity toward methicillin-resistant Staphylococcus aureus (MRSA) has been a serious emerging global issue. New effective antimicrobials and/or new approaches to settle this issue are urgently needed. The oriental herb, Alpinia officinarum, has been used in Korea for several hundreds of years to treat various infectious diseases. As it is well known, one of the active constituents of Alpinia officinarum is galangin. Against the 17 strains, the minimum inhibitory concentrations (MICs) of galangin (GAL) were in the range of 62.5 ~ 125 microg/ml, and the MICs of gentamicin (GEN) ranged from 1.9 microg/ml to 2,000 microg/ml. The fractional inhibitory concentrations (FICs) of GAL, in combination with GEN, against 3 test strains were 0.4, 3.9, and 250 microg/ml, and were all 15.62 microg/ml in GEN. The FIC index showed marked synergism in the value range of 0.19 to 0.25. By determining time-kill curves, also confirmed the low synergism of the GAL and GEN combination against 4 h, 8 h, 12 h, and 24 h cultured MRSA. The time-kill study results indicated a low synergistic effect against 3 test strains. Thus, the mixture of GAL and GEN could lead to the development of new combination antibiotics against MRSA infection.     

Pharmacological synergism of bee venom and melittin with antibiotics and plant secondary metabolites against multi-drug resistant microbial pathogens

The goal of this study was to investigate the antimicrobial activity of bee venom and its main component, melittin, alone or in two-drug and three-drug combinations with antibiotics (vancomycin, oxacillin, and amikacin) or antimicrobial plant secondary metabolites (carvacrol, benzyl isothiocyanate, the alkaloids sanguinarine and berberine) against drug-sensitive and antibiotic-resistant microbial pathogens. The secondary metabolites were selected corresponding to the molecular targets to which they are directed, being different from those of melittin and the antibiotics.The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were evaluated by the standard broth microdilution method, while synergistic or additive interactions were assessed by checkerboard dilution and time-kill curve assays. Bee venom and melittin exhibited a broad spectrum of antibacterial activity against 51 strains of both Gram-positive and Gram-negative bacteria with strong anti-MRSA and anti-VRE activity (MIC values between 6 and 800 µg/ml). Moreover, bee venom and melittin showed significant antifungal activity (MIC values between 30 and 100 µg/ml). Carvacrol displayed bactericidal activity, while BITC exhibited bacteriostatic activity against all MRSA and VRE strains tested (reference strains and clinical isolates), both compounds showed a remarkable fungicidal activity with minimum fungicidal concentration (MFC) values between 30 and 200 µg/ml. The DNA intercalating alkaloid sanguinarine showed bactericidal activity against MRSA NCTC 10442 (MBC 20 µg/ml), while berberine exhibited bacteriostatic activity against MRSA NCTC 10442 (MIC 40 µg/ml).Checkerboard dilution tests mostly revealed synergism of two-drug combinations against all the tested microorganisms with FIC indexes between 0.24 and 0.50, except for rapidly growing mycobacteria in which combinations exerted an additive effect (FICI = 0.75–1). In time-kill assays all three-drug combinations exhibited a powerful bactericidal synergistic effect against MRSA NCTC 10442, VRE ATCC 51299, and E. coli ATCC 25922 with a reduction of more than 3log₁₀ in the colony count after 24 h. Our findings suggest that bee venom and melittin synergistically enhanced the bactericidal effect of several antimicrobial agents when applied in combination especially when the drugs affect several and differing molecular targets. These results could lead to the development of novel or complementary antibacterial drugs against MDR pathogens.     

Antileishmanial activity of indole alkaloids from Aspidosperma ramiflorum

The present study was designated to evaluate the antileishmanial activity of acid and basic fractions that were obtained after acid-basic extraction, from ethanolic 70% crude extract and pure compounds from the stem bark of Aspidosperma ramiflorum. The basic alkaloidal fraction presented a good activity against the extracellular form (promastigotes) of Leishmania (L.) amazonensis (LD(50) value<47 microg/ml). Based on these findings, the basic fraction was fractionated on silica gel column chromatography in a bioassay-guided fractionation affording individual purified ramiflorines A and B. Both ramiflorines A and B showed significant activity against Leishmania (L.) amazonensis (LD(50) values of 16.3+/-1.6 microg/ml and 4.9+/-0.9 microg/ml, respectively). Our results are promising, showing that these compounds are biologically active against Gram-positive bacteria.     

A newly isolated Streptomyces sp. CS392 producing three antimicrobial compounds

With the aim of isolating new microbes capable of producing strong antimicrobial substances, strain CS392 was screened from 700 soil isolates preserved in our laboratory. The strain was related to genus Streptomyces based on various characteristics. Three highly active antimicrobial compounds, C1, C2 and C3, produced by the strain were purified by solvent extraction followed by silica gel column chromatography. These compounds were highly active against various Gram-positive resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), and vancomycin-resistant Enterococcus (VRE). Among three, C3 was the most active against MRSA and VRSA with minimal inhibitory concentration (MIC) of 2 μg/ml while C2 and C3 had MIC values of 4 μg/ml for the strains. In case of Bacillus subtilis ATCC6633, C1 and C3 were more effective with MIC values of 0.5 μg/ml than C2 with MIC of 2 μg/ml. Those antibiotics were variably active (MIC of 4-32 μg/ml) against Micrococcus luteus ATCC 9341, Enterococcus faecalis ATCC 29212, Mycobacterium smegmatis ATCC 9341 and VRE.     

Isolation and characterization of Streptomyces sp KH-614 producing anti-VRE (vancomycin-resistant enterococci) antibiotics

The actinomycete strain KH-614 was antagonistic to vancomycin-resistant enterococci (VRE). Based on the diaminopimelic acid (DAP) type, morphological and physiological characteristics examined by scanning electron microscopy (SEM), KH-614 was confirmed as belonging to the genus Streptomyces. Based on the 16S rDNA nucleotide sequences, Streptomyces sp. KH-614 was found to have a relationship with Streptomyces lydicus. The production of antibiotic from this strain was most favorable when cultured in glucose, polypeptone, yeast extract (PY) medium for 6 days at 27 degrees C. The antibiotic was identified as a cyclo(L-leucyl-L-prolyl) by comparing it with the reported spectral data including MS and NMR. Cyclo(leu-pro) was found to be active against twelve VRE strains, including E. faecium (vanA, vanB), and E. faecalis (vanA, vanB), that had been isolated over a period three years (1998-2000). Cyclo(leu-pro) was especially effective against VRE strains such as E. faecalis (K-99-34), E. faecalis (K-00-184), E. faecalis (K-00-221), and the MIC values were 12.5 microg/ml. Moreover, cyclo(leu-pro) was effective against three leukemic cell lines at concentrations below 100 microg/ml. At 100 mg/ml cyclo(leu-pro), K562, HL60, and U937 leukemic cell lines showed growth inhibition of 95, 91, and 93%, respectively. In a normal cell line, MDBK, cyclo(leu-pro) exerted 24% growth inhibition at a concentration of 100 microg/ml, and showed no inhibitory activity at concentrations below 10 microg/ml. These results indicate that cyclo(leu-pro) is a potential anti-leukemic and anti-VRE agent.     

Antimicrobial activity of isoprenoid-substituted xanthones from Cudrania cochinchinensis against vancomycin-resistant enterococci.

Ten xanthones with one or two isoprenoid groups and a prenylated benzophenone isolated from roots of Cudrania cochinchinensis (Moraceae) were tested for their antimicrobial activities against vancomycin-resistant enterococci (VRE). Among these compounds, gerontoxanthone H exhibited considerable antibacterial activity against five VRE strains (VanA, VanB and VanC) (MICs = 1.56 microg/ml). Four xanthones, 1,3,7-trihydroxy-2-prenylxanthone, gerontoxanthone I, alvaxanthone and isoalvaxanthone, showed weaker antibacterial activity against these VREs (MICs = 3.13-6.25 microg/ml). .     

Comparison of the effects in vitro of tea tree oil and plaunotol on methicillin-susceptible and methicillin-resistant strains of Staphylococcus aureus

The effects in vitro of tea tree oil (TTO) and plaunotol were examined by monitoring the growth of a standard strain of Staphylococcus aureus FDA 209P and of fourteen methicillin-susceptible strains of S. aureus (MSSA), together with twenty methicillin-resistant strains (MRSA). The minimum inhibitory concentrations (MIC) and the doses for 50% inhibition of growth (ID50) were determined by the micro-broth dilution (MD) method, and the broth dilution with shaking (BDS) method, respectively. The MIC of plaunotol for 50 and 90% of the MSSA and MRSA were assessed by the MD method, as 16 microg/ml and > or = 1,024 microg/ml, respectively. No antibacterial effects of TTO on MSSA and MRSA were detected by the MD method. The growth-inhibitory effects of TTO on S. aureus by the BDS method were examined, and it appeared that TTO was effective over a lower range of concentrations than previously reported. It seems that TTO is very effective in vitro against MSSA and MRSA at high concentrations but less effective below 40 microg/ml of TTO.     

Synthesis of variously oxidized abietane diterpenes and their antibacterial activities against MRSA and VRE

Variously oxidized 12 natural abietanes, 6,7-dehydroferruginol methyl ether (3), ferruginol (5), 11-hydroxy-12-oxo-7,9(11),13-abietatriene (7), royleanone (9), demethyl cryptojaponol (12), salvinolone (14), sugiol methyl ether (16), sugiol (17), 5,6-dehydrosugiol methyl ether (19), 5,6-dehydrosugiol (20), 6beta-hydroxyferruginol (23), and taxodione (25) were synthesized. Antimicrobial activities of synthesized phenolic diterpenes and their related compounds against MRSA and VRE were evaluated. Phenols (12-hydroxyabieta-8,11,13-trien-6-one 22 and 23), catechols (12 and 14) and taxodione 25 showed potent activity with 4-10 microg/mL of MIC against MRSA and 4-16 microg/mL of MIC against VRE. (-)-Ferruginol showed more potent activity than natural type (+)-ferruginol. Quinone methide 7 showed the most potent activity with 0.5-1 microg/mL of MIC against both MRSA and VRE.     

Antimicrobial Activities of Methanol,Ethanol and Supercritical CO2 Extracts of Philippine Piper betle L. on Clinical Isolates of Gram Positive and Gram Negative Bacteria with Transferable Multiple Drug Resistance

Piper betle L. has traditionally been used in alternative medicine in different countries for various therapeutic purposes, including as an anti-infective agent. However, studies reported in the literature are mainly on its activities on drug susceptible bacterial strains. This study determined the antimicrobial activities of its ethanol, methanol, and supercritical CO₂ extracts on clinical isolates of multiple drug resistant bacteria which have been identified by the Infectious Disease Society of America as among the currently more challenging strains in clinical management. Assay methods included the standard disc diffusion method and the broth microdilution method for the determination of the minimum inhibitory concentration (MIC) and the minimum bactericidal concentrations (MBC) of the extracts for the test microorganisms. This study revealed the bactericidal activities of all the P. betle leaf crude extracts on methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), extended spectrum β-lactamase-producing Enterobacteriaceae, carbapenem-resistant Enterobacteriaceae, and metallo-β-lactamase-producing Pseudomonas aeruginosa and Acinetobacter baumannii, with minimum bactericidal concentrations that ranged from 19μg/ml to 1250 μg/ml. The extracts proved to be more potent against the Gram positive MRSA and VRE than for the Gram negative test bacteria. VRE isolates were more susceptible to all the extracts than the MRSA isolates. Generally, the ethanol extracts proved to be more potent than the methanol extracts and supercritical CO₂ extracts as shown by their lower MICs for both the Gram positive and Gram negative MDRs. MTT cytotoxicity assay showed that the highest concentration (100 μg/ml) of P. betle ethanol extract tested was not toxic to normal human dermal fibroblasts (HDFn). Data from the study firmly established P. betle as an alternative source of anti-infectives against multiple drug resistant bacteria.     

Different antibacterial actions of isoflavones isolated from Erythrina poeppigiana against methicillin-resistant Staphylococcus aureus

AIMS: To screen six isoflavones isolated from Erythrina poeppigiana (Leguminosae) for their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: Stem bark of E. poeppigiana was macerated with acetone and the methylene chloride-soluble fraction of the residue was applied to repeated silica gel column chromatography and eluted. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by a broth dilution method. Inactive compounds that failed inhibiting bacterial growth at 25 microg ml(-1) were further investigated for their combination effects with methicillin and oxacillin. Of the isolated isoflavones, 5,7,4'-trihydroxy-8,3'-di(gamma,gamma-dimethylallyl)isoflavone (isolupalbigenin) exhibited the highest anti-MRSA activity (MICs: 1.56-3.13 microg ml(-1); MBCs: 6.25-12.5 microg ml(-1)), followed by 5,7,4'-trihydroxy-6-gamma,gamma-dimethylallylisoflavone (erythrinin B). Inactive compounds were combined with methicillin or oxacillin, 5,4'-dihydroxy-(3',4'-dihydro-3'-hydroxy)-2',2'-dimethylpyrano[5',6':6,7]isoflavone (M-Wi-2) intensifying the susceptibility of MRSA strains to these antibiotics. In all but one strain, the MIC values of methicillin were reduced from > or =100 to 6.25-12.5 microg ml(-1) in the presence of M-Wi-2 (25 microg ml(-1)). CONCLUSIONS: Isoflavones from E. poeppigiana showed two different antibacterial activities against MRSA: direct growth inhibition and intensification of methicillin sensitivity. SIGNIFICANCE AND IMPACT OF THE STUDY: Isolupalbigenin and M-Wi-2 could lead to the development of compounds for new approaches against MRSA infection.     

Anticariogenic activity of macelignan isolated from Myristica fragrans (nutmeg) against Streptococcus mutans

The occurrence of dental caries is mainly associated with oral pathogens, especially cariogenic Streptococcus mutans. Preliminary antibacterial screening revealed that the extract of Myristica fragrans, widely cultivated for the spice and flavor of foods, possessed strong inhibitory activity against S. mutans. The anticariogenic compound was successfully isolated from the methanol extract of M. fragrans by repeated silica gel chromatography, and its structure was identified as macelignan by instrumental analysis using 1D-NMR, 2D-NMR and EI-MS. The minimum inhibitory concentration (MIC) of macelignan against S. mutans was 3.9 microg/ml, which was much lower than those of other natural anticariogenic agents such as 15.6 microg/ml of sanguinarine, 250 microg/ml of eucalyptol, 500 microg/ml of menthol and thymol, and 1000 microg/ml of methyl salicylate. Macelignan also possessed preferential activity against other oral microorganisms such as Streptococcus sobrinus, Streptococcus salivarius, Streptococcus sanguis, Lactobacillus acidophilus and Lactobacillus casei in the MIC range of 2-31.3 microg/ml. In particular, the bactericidal test showed that macelignan, at a concentration of 20 microg/ml, completely inactivated S. mutans in 1 min. The specific activity and fast-effectiveness of macelignan against oral bacteria strongly suggest that it could be employed as a natural antibacterial agent in functional foods or oral care products.     

New bisanthraquinone antibiotics and semi-synthetic derivatives with potent activity against clinical Staphylococcus aureus and Enterococcus faecium isolates

The escalation of antibiotic resistance among Gram-positive pathogens presents increasing treatment challenges and requires the development of innovative therapeutic agents. Here, we present the antimicrobial properties of structurally unusual bisanthraquinone metabolites produced by a marine streptomycete and four semi-synthetic derivatives. Biological activities were measured against clinically derived isolates of vancomycin-resistant Enterococcus faecium (VRE), and methicillin-susceptible, methicillin-resistant, and tetracycline-resistant Staphylococcus aureus (MSSA, MRSA, and TRSA, respectively). The most potent antibiotic displayed MIC₅₀ values of 0.11, 0.23, and 0.90 μM against a panel (n = 25 each) of clinical MSSA, MRSA, and VRE, respectively, and was determined to be bactericidal by time-kill analysis.     

2016-2017年宁夏地区牛源金黄色葡萄球菌的全基因组分析

[目的]了解宁夏地区奶牛乳腺炎金黄色葡萄球菌(Staphylococcus aureus,SA)代表菌株的基因组序列基本特征,进一步探究其耐药基因型、毒力及进化关系,为兽医临床防治提供理论依据.[方法]采用纸片法对97株金黄色葡萄球菌临床分离株进行抗菌药物敏感性试验,同时进行葡萄球菌蛋白A(Staphylococcus...     

Inhibition of the myotoxic activity of Bothrops jararacussu venom and its two major myotoxins, BthTX-I and BthTX-II, by the aqueous extract of Tabernaemontana catharinensis A. DC. (Apocynaceae)

Partial neutralization of the myotoxic effect of Bothrops jararacussu venom (BV) and two of its myotoxins [bothropstoxin-I (BthTX-I), catalytically inactive, and II (BthTX-II), showing low PLA2 activity], by the lyophilized aqueous extract of Tabernaemontana catharinensis (AE), was studied in rat isolated soleus muscle preparations (in vitro) and through i.m. injection in the gastrocnemius muscle (in vivo) by determination of creatine kinase (CK) activity and histopathological analysis. Incubation of soleus muscle for 1 h with BV or toxins (20 microg/ml) plus AE (400 microg/ml) added immediately after BV, BthTX-I or BthTX-II reduced CK levels by 53%, 37% and 56%, respectively. The myonecrotic effects of BV (20 microg/ml) upon soleus muscle was reduced 24%, 35% and 36% when AE (400 microg/ml) was added 1 h after BV and CK was evaluated 30 min, 1 and 2 h later, respectively. For BthTX-I these values were 46%, 48% and 47%, while for BthTX-II no inhibitory effect was detected. Histological analysis of soleus muscle after incubation with AE (400 microg/ml, 1 h) did not reveal any change in muscle fibers, but severe necrosis induced by BV or toxins (20 microg/ml) was clearly in evidence, and decreased significantly when soleus muscle was protected by AE. This protection was also observed when AE was administered 1 h after BV or BthTX-I, but not after BthTX-II. AE did not inhibit the catalytic PLA2 activity of BthTX-II or BV and did not change the PAGE pattern of BV, BthTX-I or BthTX-II. In vivo assays were performed in 100-g rats and maximal CK release was attained at a dose of 100 microg of BV, 3 h after injection. AE was not effective when injected 20 s after BV or toxins. However, injecting BV or toxins (100 microg), which were pre-incubated with AE (2 mg) caused an inhibition of 57%, 59% and 51%, respectively, with zero time pre-incubation, but was less effective with 1 h pre-incubation. This plant represents a potential source of promising myotoxin inhibitors.     

Changes of methicillin-resistant Staphylococcus aureus (MRSA) phagotypes in Gdansk in 1990-1998

The aim of the study was the assessment of changes in the occurrence of various MRSA phagotypes in hospitals in the Gdańsk area in 1990-1998. The study was carried out on 175 MRSA strains: 45 strains isolated in 1990-1995 and 130 in 1997-1998. The studied staphylococci were obtained from various clinical materials from patients in 18 hospitals. Phagotyping was done with a set of 10 experimental phages from MRSA strains obtained from the Central Public Health Laboratory in London. Drug-resistance was determined by the disc-diffusion method and in case of strains with medium susceptibility to fusidic acid the minimal inhibitory concentration (MIC) was determined by serial dilutions on solid medium. The study showed among MRSA strains isolated in 1997-1998 a new, previously not known strains with phage pattern MR25/M5 predominated (57.7%). Its presence was found in various hospitals in that area. MRSA belonging to MR25/M5 phagotype were mostly resistant to doxycycline, gentamycin, erythromycin, clindamycin, ciprofloxacin, rifampicin and were resistant or only had medium susceptibility to fusidic acid. The MIC values for strains with medium susceptibility to fusidic acid (4-8 micrograms/ml) showed an evident decrease of the susceptibility to this antibiotic, formerly common in MRSA. At the same time, in 1997-1998 a considerable decrease was observed of the number of MRSA strains belonging to MR8/MR12/MR25/30/33/38/M5/622 phagotype (from 31.1% to 0.8%), and disappearance of strains with phagotypes MR25/56B/M3 and MR8/MR25/622, which in 1990-1995 accounted for 15.6% of the studied staphylococci.