Abundance and distribution of antibiotic resistance genes in a full-scale anaerobic-aerobic system alternately treating ribostamycin, spiramycin and paromomycin production wastewater

The occurrence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) has been intensively investigated for wastewater treatment systems treating single class of antibiotic in recent years. However, the impacts of alternately occurring antibiotics in antibiotic production wastewater on the behavior of ARGs in biological treatment systems were not well understood yet. Herein, techniques including high-capacity quantitative PCR and quantitative PCR (qPCR) were used to investigate the behavior of ARGs in an anaerobic-aerobic full-scale system. The system alternately treated three kinds of antibiotic production wastewater including ribostamycin, spiramycin and paromomycin, which referred to stages 1, 2 and 3. The aminoglycoside ARGs (52.1-79.3%) determined using high-capacity quantitative PCR were the most abundant species in all sludge samples of the three stages. The total relative abundances of macrolide-lincosamide-streptogramin (MLS) resistance genes and aminoglycoside resistance genes measured using qPCR were significantly higher (P < 0.05) in aerobic sludge than in sewage sludge. However, the comparison of ARGs acquired from three alternate stages revealed that MLS genes and the aminoglycoside ARGs did not vary significantly (P > 0.05) in both aerobic and anaerobic sludge samples. In aerobic sludge, one acetyltransferase gene (aacA4) and the other three nucleotidyltransferase genes (aadB, aadA and aadE) exhibited positive correlations with intI1 (r ² = 0.83-0.94; P < 0.05), implying the significance of horizontal transfer in their proliferation. These results and facts will be helpful to understand the abundance and distribution of ARGs from antibiotic production wastewater treatment systems.

Aminoglycoside-induced reduction in nucleotide mobility at the ribosomal RNA A-site as a potentially key determinant of antibacterial activity

Steady-state and time-resolved fluorescence techniques have been used to characterize the energetics and dynamics associated with the interaction of an E. coli 16 S rRNA A-site model oligonucleotide and four aminoglycoside antibiotics that exhibit a broad range of antibacterial activity. The results of these characterizations suggest that aminoglycoside-induced reduction in the mobility of an adenine residue at position 1492 of the rRNA A-site is a more important determinant of antibacterial activity than drug affinity for the A-site. This observation is consistent with a recently proposed model for the mechanism of protein synthesis inhibition by aminoglycosides that invokes a drug-induced alteration in the conformational equilibrium of the rRNA A-site (centered around the conserved adenine residues at positions 1492 and 1493), which, in turn, promotes an enhanced interaction between the rRNA and the minihelix formed by the tRNA anticodon and the mRNA codon, even when the anticodon is noncognate. Regarded as a whole, the results reported here indicate that the rational design of antibiotics that target the 16 S rRNA A-site requires consideration of not only the structure and energetics of the drug-RNA complex but also the dynamics associated with that complex.

Activity of some aminoglycoside antibiotics against true fungi, Phytophthora and Pythium species

AIMS

To investigate the in vitro antifungal and antioomycete activities of some aminoglycosides against true fungi and Phytophthora and Pythium species and to evaluate the potential of the antibiotics against Phytophthora late blight on plants.

METHODS AND RESULTS

Antifungal and antioomycete activities of aminoglycoside antibiotics (neomycin, paromomycin, ribostamycin and streptomycin) and a paromomycin-producing strain (Streptomyces sp. AMG-P1) against Phytophthora and Pythium species and 10 common fungi were measured in potato dextrose broth (PDB) and on seedlings in pots. Paromomycin was the most active against Phytophthora and Pythium species with a minimal inhibitory concentration of 1-10 microg ml(-1) in PDB, but displayed low to moderate activities towards other common fungi at the same concentration. Paromomycin also showed potent in vivo activity against red pepper and tomato late blight diseases with 80 and 99% control value, respectively, at 100 microg ml(-1). In addition, culture broth of Streptomyces sp. AMG-P1 as a paromomycin producer exhibited high in vivo activity against late blight at 500 microg freeze-dried weight per millilitre.

CONCLUSIONS

Among tested aminoglycoside antibiotics, paromomycin was the most active against oomycetes both in vitro and in vivo.

SIGNIFICANCE AND IMPACT OF THE STUDY

Data from this study show that aminoglycoside antibiotics have in vitro and in vivo activities against oomycetes, suggesting that Streptomyces sp. AMG-P1 may be used as a biocontrol agent against oomycete diseases.

Drug targeting of HIV-1 RNA.DNA hybrid structures: thermodynamics of recognition and impact on reverse transcriptase-mediated ribonuclease H activity and viral replication

RNA degradation via the ribonuclease H (RNase H) activity of human immunodeficiency virus type I (HIV-1) reverse transcriptase (RT) is a critical component of the reverse transcription process. In this connection, mutations of RT that inactivate RNase H activity result in noninfectious virus particles. Thus, interfering with the RNase H activity of RT represents a potential vehicle for the inhibition of HIV-1 replication. Here, we demonstrate an approach for inhibiting the RNase H activity of HIV-1 RT by targeting its RNA.DNA hybrid substrates. Specifically, we show that the binding of the 4,5-disubstituted 2-deoxystreptamine aminoglycosides, neomycin, paromomycin, and ribostamycin, to two different chimeric RNA-DNA duplexes, which mimic two distinct intermediates in the reverse transcription process, inhibits specific RT-mediated RNase H cleavage, with this inhibition being competitive in nature. UV melting and isothermal titration calorimetry studies reveal a correlation between the relative binding affinities of the three drugs for each of the chimeric RNA-DNA host duplexes and the relative extents to which the drugs inhibit RT-mediated RNase H cleavage of the duplexes. Significantly, this correlation also extends to the relative efficacies with which the drugs inhibit HIV-1 replication. In the aggregate, our results highlight a potential strategy for AIDS chemotherapy that should not be compromised by the unusual genetic diversity of HIV-1.

Ribostamycin inhibits the chaperone activity of protein disulfide isomerase

In the process of screening of proteins binding to ribostamycin in bovine liver using the affinity column chromatography, we found that ribostamycin inhibited the chaperone activity of protein disulfide isomerase (PDI), but it did not inhibit the isomerase activity. PDI was identified by SDS-PAGE, Western blotting, and N-terminal amino acid sequence analysis. A 100:1 molar ratio of ribostamycin to PDI was almost sufficient to completely inhibit the chaperone activity of PDI. The binding affinity of ribostamycin to purified bovine PDI was determined by the Biacore system, which gave a K(D) value of 3.19 x 10(-4) M. This suggests that ribostamycin binds to region distinct from the CGHC motif of PDI. This is the first report to describe the inhibitor of the chaperone activity of PDI.

In vitro activity of mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid against Borrelia burgdorferi

The in vitro susceptibility profile of Borrelia burgdorferi is not yet well defined for several antibiotics. Our study explored the in vitro susceptibility of B. burgdorferi to mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid. Minimal inhibitory concentrations (MICs) and minimal borreliacidal concentrations (MBCs) were measured using a standardised colorimetric microdilution method and conventional subculture experiments. MIC values were lowest for mezlocillin (MIC(90), < or =0.06 mg/l) and meropenem (MIC(90), 0.33 mg/l). Vancomycin (MIC(90), 0.83 mg/l) was less effective in vitro. Borreliae proved to be resistant to aztreonam (MIC(90), >32 mg/l), teicoplanin (MIC(90), 6.6 mg/l), ribostamycin (MIC(90), 32 mg/l), and fusidic acid (MIC(90), >4 mg/l). The mean MBCs resulting in 100% killing of the final inoculum after 72 h of incubation were lowest for mezlocillin (MBC, 0.83 mg/l). This study gathered further data on the in vitro susceptibility patterns of the B. burgdorferi complex. The excellent in vitro effectiveness of acylamino-penicillin derivatives and their suitability for the therapy of Lyme disease is emphasised.

Structural rearrangements of HIV-1 Tat-responsive RNA upon binding of neomycin B

Binding of human immunodeficiency virus type 1 (HIV-1) transactivator (Tat) protein to Tat-responsive RNA (TAR) is essential for viral replication and is considered a promising starting point for the design of anti-HIV drugs. NMR spectroscopy indicated that the aminoglycosides neomycin B and ribostamycin bind to TAR and that neomycin is able to inhibit Tat binding to TAR. The solution structure of the neomycin-bound TAR has been determined by NMR spectroscopy. Chemical shift mapping and intermolecular nuclear Overhauser effects define the binding region of the aminoglycosides on TAR and give strong evidence for minor groove binding. Based on 15 nuclear Overhauser effect-derived intermolecular distance restraints, a model structure of the TAR-neomycin complex was calculated. Neomycin is bound in a binding pocket formed by the minor groove of the lower stem and the uridine-rich bulge of TAR, which adopts a conformation different from those known. The neamine core of the aminoglycoside (rings I and II) is covered with the bulge, explaining the inhibition of Tat by an allosteric mechanism. Neomycin reduces the volume of the major groove in which Tat is bound and thus impedes essential protein-RNA contacts.

Neomycin inhibition of the hammerhead ribozyme involves ionic interactions

To investigate the properties of the neomycin-hammerhead interaction, inhibition of hammerhead activity was measured as a function of magnesium concentration and pH. The data are consistent with a simple competition between magnesium and neomycin with about five magnesium ions required to displace neomycin from the hammerhead. The pH dependence of the inhibition of hammerhead cleavage by neomycin and two related aminoglycosides was also determined. The data indicate that at least three of the five positively charged ammonium ions present on neomycin are critical for inhibiting hammerhead function. Taken together, these results suggest that the neomycin-hammerhead interaction is mostly ionic in character.

A novel approach to insertional mutagenesis of Haemophilus influenzae

Insertional mutagenesis of the Haemophilus influenzae chromosome was accomplished by a novel method employing a 2.2-kbp element, TSTE. This element, consisting of the neo gene of Tn5 flanked by Haemophilus-specific uptake sequences, was ligated to circularized chromosomal fragments before transformation into the homologous strain. Eight mutants defective in the production of haemocin were detected. This strategy provides an efficient mechanism for the insertional mutagenesis of H. influenzae.

Effect of aminoglycoside antibiotics on the electrical stimulation-induced contractile response of the guinea-pig ureter

Using electrical stimulation, we first investigated whether the movement of ureteral smooth muscle of the guinea-pig was myogenic in its control, or neurogenic. We then investigated the effects of aminoglycoside antibiotics (kanamycin, bekanamycin and ribostamycin) on the movement of ureteral smooth muscle induced by electrical stimulation. In these investigations, each ureter removed from the animal was cut into three approximately equal-sized segments, which are an upper segment (kidney side), a middle segment and a lower segment (urinary bladder side). Each segment was mounted in an organ bath filled with Krebs solution and the mechanical response induced by electrical stimulation of each segment was recorded isometrically. Each one of the upper, the middle and the lower segments was stimulated with rectangular pulses (50 volt, 0.1-3 msec durations, 40 Hz) for a period of 2 sec. Of all segments tested (ten in each group), none showed any response to the stimulation with pulses below 0.5 msec duration. While 2-3 segments out of ten of the upper, the middle and the lower ureteral segments showed a contractile response to stimulation with pulses of 1 msec duration, the rest of the segments showed no response to the same stimulation. This contractile response was not inhibited by tetrodotoxin which is known to block the nerve-mediated response. And also, all the ten samples of each upper, middle and lower segment never failed to show a contractile response to stimulation with pulses of 2 msec and 3 msec duration. Various drugs which are already known to block the nerve-mediated response (i.e., atropine, guanethidine, phentolamine, propranolol and tetrodotoxin) were tried, but none of them had an inhibitory effect on the contractile response. On the other hand, each one of kanamycin (KM), bekanamycin (AKM) and ribostamycin (RSM) in concentrations of 1 x 10(-5) g/ml-1 x 10(-3) g/ml produced a concentration-dependent decreasing effect in the magnitude of the electrical stimulation-induced contractile response of the ureteral segment. In addition, the decreasing effects of these antibiotics were also observed in the tetrodotoxin. From these results, we concluded that the contractile response of the ureter may be myogenic in its control, and the aminoglycoside antibiotics, KM, AKM and RSM, may act directly on the ureteral smooth muscle so as to decrease its contractile response.

Simple new test for presumptive differentiation between genus Candida and genus Prototheca

A differential test was made between genus Candida and genus Prototheca using a new and very simple differential test. A total of 59 strains of Candida and 78 strains of Prototheca were used. The basis of the test was the differential use of a disc carrying 60 mcg of Ribostamycin to which all the Candida were resistant and the Prototheca inhibited.

Effects of cations, polyamines and other aminoglycosides on gentamicin C2. Binding to ribosomes from sensitive and resistant Escherichia coli strains

Gentamicin C2 interacts cooperatively with ribosomes from a sensitive Escherichia coli strain in a multiphasic way with several classes of sites. It is shown that this binding is highly-dependent on Mg++ and natural endogenous polyamine concentrations. The differences observed between ribosomes from sensitive and resistant strains may be explained by the absence of specific cooperative gentamicin interactions with resistant ribosomes. The effects of other aminoglycoside antibiotics are discussed in terms of structure-activity relationships.

In vitro activity of ribostamycin against Prototheca sp

The in vitro activity of ribostamycin against algae of the genus Prototheca was evaluated by minimum inhibitory concentration (MIC) studies on solid media. Concentrations of 4 mcg/ml were required to inhibit 100% of the P. zopfii strains; 16 mcg/ml inhibited 100% of the P. stagnora strains and 95% of the P. wickerhamii strains. These values are inferior to plasma concentrations obtained after injection of ribostamycin. It is likely that this antibiotic could be effective in the treatment of protothecosis in man.

[Ribostamycin in chronic and recurrent bronchopulmonary and urinary infections]

Results in the treatment of mostly Gram-negative infections of the respiratory apparatus (30 subjects) and the urinary apparatus (20 subjects) with ribostamycin are reported. These were regarded as good overall, as shown by the bacteriological findings. An extremely high sensitivity to the antibiotic was noted in isolated germs from both types of infection. This good response in vitro was matched by an equally encouraging bacteriological result in vivo.

Inhibition of candidacidal activity of human neutrophil leukocytes by aminoglycoside antibiotics

We have tested the effect of five aminoglycoside antibiotics (gentamicin, sisomicin, tobramycin, ribostamycin, and amikacin) on the candidacidal activity of human neutrophils in vitro; all of them are inhibitory and can be grouped into three significantly different levels of toxicity. Gentamicin in the most toxic and sisomicin is the least toxic.

Aminoglycoside antibiotics. 3. Epimino derivatives of neamine, ribostamycin, and kanamycin B

2',3'-Epimino analogues of neamine, ribostamycin, and kanamycin B possessing little or no intrinsic antimicrobial activity were designed to enhance the activity of kanamycin A against bacterial strains that elaborate aminoglycoside 3'-phosphotransferases. Routes were devised for their synthesis from the parent antibiotics and the 2'',3''-epimino analogue of kanamycin B also was prepared. None of these analogues was active against phosphotransferase-producing bacteria, although the kanamycin B derivatives showed very weak activity against nonresistant strains. At 8 and 32 microgram/mL, the 2',3'-epimino analogue of neamine produced a small synergistic effect on the activity of kanamycin A against a strain of Escherichia coli that produces aminoglycoside 3'-phosphotransferase II. The N3-(carbobenzyloxy) derivative of this analogue produced a small effect against the same strain, and it, as well as the 2'',3''-epimino analogue of kanamycin B, slightly enhanced the activity of kanamycin A against a strain of Proteus rettgeri that elaborates a similar enzyme.

Ribostamycin production by a mutant of butirosin producing bacteria

By the use of our improved colony selection technique, xylostasin and ribostamycin producing mutants were isolated from nitrosoguanidine treated Bacillus circulans B15M, a producer of butirosins A and B. Among these structurally related aminoglycosides, ribostamycin is the well-known product of a Steptomyces and has not been isolated as a bacterial metabolite. A selected mutant of strain 306, which produces xylostasin and ribostamycin, was futher mutagenized in expectation of getting an improved strain having the ability to accumulate a large amount of ribostamycin in the culture broth. One mutant, strain 451, derived from strain 306, produced ribostamycin free of xylostasin.

[Neuromuscular blocking properties of tobramycin, dibekacin and ribostamycin in man (author's transl)]

Neuromuscular blocking properties of tobramycin (Tobracin 60mg), dibekacin (Panmycin 100 mg) and ribostamycin (Vistamycin 1g) were studied in man during anesthesia and surgery by observing the effects of these antibiotics on muscle twitch tension. These antibiotics alone did not show any neuromuscular blocking action in the therapeutic doses. The neuromuscular blocking action of d-tubocurarine chloride was potentiated by the intravenous administration of 1g of ribostamycin. Tobramycin 60mg did not show remarkable effect, but dibekacin 100mg produced a slight potentiating effect on the action of d-tubocurarine. The enhancement of the action of d-tubocurarine was anatagonized by edrophonium and calcium. The action of succinylcholine chloride was not affected by tobramycin or ribostamycin, but it was potentiated transitorily by dibekacin. It is advisable to pay attention to possible respiratory depression when ribostamycin and dibekacin and used in combination with non-depolarizing muscle relaxants and/or anesthetics.

Amikacin, an aminoglycoside with marked activity against antibiotic-resistant clinical isolates

A total of 319 clinical isolates known to be resistant to one or more aminoglycoside antibiotics were tested for their susceptibility to 10 aminoglycosides. The percentages of isolates found by an agar dilution method to be susceptible were: amikacin, 83.7%; tobramycin, 41.4%; butirosin A, 33.2%; dideoxykanamycin B, 32.6%; gentamicin C, 27.3%; lividomycin A, 17.6%; neomycin B, 10.7%; paromomycin, 10.3%; kanamycin A, 10.0%; and ribostamycin, 7.2%. The effectiveness of the antibiotics was related to their degree of resistance to bacterial enzymes; e.g., of the nine enzymes known to inactivate antibiotics containing 2-deoxystreptamine, amikacin was affected by one enzyme, tobramycin by five, and gentamicin and kanamycin by six. Examination of cell-free extracts from the 52 strains resistant to amikacin revealed that only four contained the amikacin-inactivating enzyme aminoglycoside-6'-acetyltransferase, a finding indicating that this mechanism of resistance is rare. Other experiments suggest that most amikacin-resistant strains, which are almost invariably resistant to all aminoglycosides, lack the ability to accumulate effectively either amikacin or presumably the other antibiotics intracellularly.

In vitro activity of amikacin and ten other aminoglycoside antibiotics against gentamicin-resistant bacterial strains

Sixty-nine strains of gentamicin-resistant gram-negative bacilli obtained from different geographical sources were tested for susceptibility to 11 aminoglycoside antibiotics. From the results of determinations of minimal inhibitory concentrations, patterns of resistance were established for 45 strains of Enterobacteriaceae and 24 strains of Pseudomonas aeruginosa. Overall, 81% of the strains were sensitive to amikacin and 33% of the strains were sensitive to butirosin, the next most active compound. Results indicated that 54% of the P. aeruginosa strains were sensitive to amikacin and 33% were sensitive to tobramycin. From resistance patterns, enzymes responsible for inactivation of the antibiotics were deduced. The most common enzyme was aminoglycoside nucleotidyltransferase(2''), either alone or combined with either aminoglycoside phosphotransferase(3')-I or aminoglycoside phosphotransferase(3')-II. Aminoglycoside acetyltransferase(2) was identified exclusively in strains of Providencia stuartii. Specific enzymes could not be identified for 30 strains, 21 of which were P. aeruginosa.

[Studies on the disc method for the determination of bacterial sensitivity to ribostamycin (author's transl)]

The MICs of ribostamycin (RSM) were determined by the two-fold serial agar-dilution method of 109 bacterial strains of 20 species. The diameters of inhibition zones of these bacterial strains by the 50 mug RSM disc were also measured. The relation between the MIC and the diameter of the inhibition zone was found to be expressed as a primary regression line in all cases of the conventional method (cultured for about 16 hours), delayed assay method (cultured for about 24 hours) and rapid methods (5 approximately 6 hours and 3 approximately 4 hours culture methods). Thus, it was confirmed that the single-disc method can be employed for the susceptibility test of RSM. Subsequently, variations of MICs obtained by the disc-diffusion method were compared with those obtained by the serial agar-dilution method.

Antibacterial activity of ribostamycin on Enterobacteriaceae

The study of the inhibitory activity of ribostamvcin (Vistamycin), an antibiotic derived from Streptomyces ribosidificus, on 161 strains of Gram-negative bacilli shows that the antibacterial spectrum of this antibiotic is identical to that of kanamycin. If controlled clinical studies confirm that ribostamycin is less toxic than kanamycin on the otovestibular system, this antibiotic will constitute a real therapeutic advance.

Neuromuscular blocking properties of some antibiotics in man

Neuromuscular blocking properties of ribostamycin (1 gm), dibecacin (100 mg) and tobramycin (60 mg) were studied in a man during anesthesia and surgery by observing the effects of these antibiotics on muscle twitch tension. These drugs alone did not show any neuromuscular blocking action in those therapeutic doses. However, during the recovery phase of d-tubocurarine block the intravenous administration of 1 gm of ribostamycin caused a fairly rapid decrease in twitch tension. Tobramycin 60 mg did not show any remarkable effect, but dibecacin 100 mg produced a slight potentiating effect on the action of d-tubocurarine. The enhancement of the action of d-tubocurarine was antagonized promptly by edrophonium and more slowly by calcium.

Aminoglycoside 3'-phosphotransferase III, a new phosphotransferase. Resistance mechanism

The aminoglycoside phosphotransferase of Pseudomonas aeruginosa 21-75 was purified by affinity chromatography using dibekacin-Sephadex 4B or lividomycin A-Sepharose 4B followed by DEAE Sephadex A-50 chromatography. It had activities of both the known aminoglycoside 3'-phosphotransferases I and II, and transferred phosphate from ATP to the 3'-hydroxyl group of kanamycin A, ribostamycin and butirosin A and 5-hydroxyl group of lividomycin A. This enzyme was designated aminoglycoside 3'-phosphotransferase III. It showed strong substrate inhibition by kanamycin A and ribostamycin when their concentration exceeded 6 muM. Purification and characterization of this enzyme are reported.

[Studies on the therapeutic effects of lividomycin in respiratory infections (author's transl)]

Therapeutic effects of lividomycin (LVDM) were studied in 33 patients with respiratory infections including pneumonia, lung abscess, chronic bronchitis, etc. LVDM was intramuscularly administered at the dose of 1 or 2 g per day for consecutive 4 to 25 days. The results obtained are summarized below: 1. At the end of the first week of the treatment, rate of improvement in such parameters as cough, sputum, rales, fever and blood sedimentation rate were 69%, 56.7%, 60%, 79.2% and 70% respectively. Also, in 16% of the patients, abnormal shadow noted in X-ray film of the chest was disappeared and in 20% of the patients, size of the same was reduced during the first week of treatment. 2. Therapeutic effects of LVDM were evaluated synthetically and were graded as excellent, good, fair and ineffective. LVDM was effective in about 70 per cent of the patients, that is, excellent results were obtained in 4 patients, good in 12 patients, fair in 6 patients, and in 10 patients this antibiotic was ineffective. 3. In one patient with slight loss of high frequency perception was observed on the audiogram, but no other ototoxic effects such as subjective hearing loss, tinnitus, etc. In addition, no untoward effects on renal and hepatic function were observed. 4. The MIC values of LVDM for clinically isolated 20 strains of Pseudomonas aeruginosa were examined, using kanamycin for comparison. The MIC values of LVDM for many strains were superior to those of kanamycin. In view of the test results mentioned above, LVDM would appear to be useful medication for the treatment of some of respiratory infections.

Bioconversion of ribostamycin (SF-733). II. Isolation and structure of 3-N-acetylribostamycin, a microbiologically inactive product of ribostamycin produced by Streptomyces ribosidificus

The isolation and structure determination of 3-N-acetylribostamycin, a microbiologically inactive derivative, produced enzymatically from ribostamycin by Streptomyces ribosidificus is described. The location of the acetyl group was established by mass and NMR spectrometry of the new compound and its derivatives, and by optical rotation studies conducted on N-ethoxycarbonyl-2-deoxystreptamine. The latter compound was obtained by partial acid hydrolysis of tri-N-ethoxycarbonyl-N-acetylribostamycin.