In-vitro activity of three new fluoroquinolones and synergy with ansamycins against Mycobacterium leprae

A naturally occurring, gram-negative, nonobligate predator bacterial strain 679-2, exhibits broad-spectrum antimicrobial activity that is due, in part, to the production of three extracellular compounds. Antimicrobialactivity-directed fractionation of a culture of strain 679-2 against a panel of microorganisms has led to the isolation of three compounds: pyrrolnitrin, maculosin, and a new compound, which we have named banegasine. Although pyrrolnitrin is well known in the literature, it has not been found in cells with the herbicide maculosin. Further, this is the first report of production of maculosin by a prokaryote. Both maculosin and banegasine, which displayed no antimicrobial activities alone, were found to potentiate the antimicrobial activity of pyrrolnitrin. Based on 16S rRNA sequence, cellular fatty acid composition, and biochemical and cultural characteristics, strain 679-2 appears to represent a new genus and species of eubacteria, Aristabacter necator. The potent, broad-spectrum antimicrobial activity of predator strain 679-2 may be due to synergism between metabolites.

Section: Vol 47 2003 Synergistic Antimicrobial Activity Of Metabolimentioning

confidence: 99%

“…FIC values were calculated by using the following formula: FIC ϭ (MIC Drug A in combination/MIC Drug A alone) ϩ (MIC Drug B in combination/MIC Drug B alone). Synergy was defined as an FIC value of Յ0.5, whereas FIC values between 0.5 to 1.0 were considered to be the result of additive antimicrobial effects (2,12,18).…”

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confidence: 99%

Synergistic Antimicrobial Activity of Metabolites Produced by a Nonobligate Bacterial Predator

Cain

Lee²,

Waldo

et al. 2003

“…Furthermore, synergism was observed when levofloxacin was combined with either rifabutin or KRM-1648 but not when it was combined with rifampin. The superiority of rifabutin and KRM-1648 over rifampin against M. leprae has been shown earlier (6,7). However, at this stage we cannot explain why levofloxacin exhibits synergism with rifabutin and KRM-1648 but not with rifampin.…”

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confidence: 69%

“…Recently, we have also observed parallelism between the ATP levels, [ 3 H]thymidine uptake values, microscopic counts, and phenolic glycolipid (PGL-1) levels of M. leprae cells incubated in DH medium. Using this system, we have evaluated the antileprosy activities of several compounds, and the in vitro susceptibility results were confirmed by the established mouse footpad system (5)(6)(7)(8). On the basis of these results, it is safe to suggest that the increase in metabolic activity of M. leprae observed in the present studies is an indication of the increase in cell numbers in primary cultures, as seen in control cultures to which no drugs were added.…”

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confidence: 99%

In vitro activity of levofloxacin, singly and in combination with rifamycin analogs, against Mycobacterium leprae

Dhople

Ibáñez

1995

The in vitro susceptibility of Mycobacterium leprae to levofloxacin was studied by using two biochemical parameters to measure the metabolic activity of the organism. Levofloxacin consistently exhibited twofold greater bactericidal activity than ofloxacin, with the MIC being 0.75 g/ml. When combined with one of the three rifamycin analogs, synergism was obtained with KRM-1648 and rifabutin but not with rifampin.The frontline drugs against leprosy since 1947 have been either dapsone, clofazimine, or rifampin. In 1981, the World Health Organization recommended the use of multidrug therapy consisting of these three drugs (20), and this has resulted in the reduction of the global prevalence of leprosy by about 57% (17). However, there are still 3.1 million cases of leprosy in the world, and about 600,000 new cases are being detected annually (17). Thus, the research will have to continue to develop new bactericidal drugs and also to formulate new multidrug therapy regimens for the treatment of multibacillary leprosy that will give better results in much shorter time.The use of fluoroquinolones in the treatment of mycobacterial diseases, including tuberculosis, is now well accepted (13,19,21). Grosset and associates (10, 11) have found ofloxacin to be the most active agent against Mycobacterium leprae in both mice and patients with leprosy. They have shown that about 99.99%, or 4 logs, of M. leprae viable on day zero were killed by 22 doses of ofloxacin. Except for rifampin, no other drug thus far tested in humans with leprosy has demonstrated such a degree of bactericidal activity (14). Recently, Tomioka and Saito (18) have reported that use of the combination of ofloxacin and rifampin gave a significant increase in their efficacies. Using an in vitro system (7) and a mouse footpad model (5), we have observed a synergistic effect when ofloxacin was combined with rifabutin but not when it was combined with rifampin.Ofloxacin exists as two optically active isomers because of the asymmetric center at the C-3 of the oxazine ring, and levofloxacin (the optically active L isomer of ofloxacin) has shown high levels of antibacterial activity against a number of bacterial species both in vitro and in mice (9). Recently, Heifets and associates (16) have observed a twofold greater inhibitory activity of levofloxacin over that of ofloxacin against extracellular as well as intracellular tubercle bacilli.The aim of the present study was therefore to evaluate the activity of levofloxacin in comparison with that of ofloxacin against M. leprae in an in vitro system and also to study its synergism when it was combined with rifamycin analogs.Antimicrobial agents. Levofloxacin and ofloxacin were obtained from the R. W. Johnson Pharmaceutical Research Institute (Raritan, N.J.). Stock solutions of levofloxacin and ofloxacin were prepared by first dissolving them in small amounts of 0.1 M NaOH and then diluting those solutions with distilled water to obtain appropriate working solutions. Three rifamycin analogs were tested: rifampin (Sigm...

“…This suggests the bactericidal activity of VUF-8514 on M leprae. On the other hand, VUF-8842 had no inhibitory effect on the metabolic activity of M leprae even at 0.32 ,ug/ml-the highest concentration tested to compare against rifampin, whose MIC against M leprae has been shown to be 0.3 ,ug/ml (10). In subsequent studies, no growth inhibition of M keprae was observed even when the concentration of VUF-8842 in the DH medium was raised up to 2.56 ,ug/ml.…”

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confidence: 90%

In vitro activities of 2,2'-bipyridyl analogs against Mycobacterium leprae

Dhople

Ibáñez

Dhople

1994

In vitro susceptibility ofMycobacterium leprae to two bipyridyl analogs was studied by using two biochemical parameters to measure the metabolic activity of the organism. VUF-8514 at 0.16 ,uglml, but not VUF-8842, completely inhibited the metabolic activity of M. keprae, and the action was bactericidal. When compared to rifampin (MIC 0.3 ,ug/ml), VUF-8514 was equally bactericidal against M. keprae. The aim of the present study was to evaluate the activities of these analogs, in comparison to that of rifampin, against M. leprae in an in vitro culture system. Antimicrobial agents. The 2,2'-bipyridyl analogs, VUF-8514 (isoquinoline derivative) and VUF-8842 (1,10-phenanthroline derivative) were obtained from H. Timmerman of Free University, Amsterdam, The Netherlands. The structural formulae and chemistry of these compounds have been described earlier (3)(4)(5) (7). ATP determinations were carried out by the firefly bioluminescent technique described earlier (8), while the procedure of Khanolkar and coworkers (17) was followed for the measurement of thymidine uptake.The effect of drug on M. leprae in primary culture was evaluated after incubating cultures for 4 weeks at 34°C. To determine if the effects were bacteriostatic or bactericidal, the cells from 4-week-old primary cultures were washed twice with fresh DH medium and then suspended in fresh DH medium without the drug and incubated at 34°C for four more weeks. At this time, ATP and [3H]thymidine uptake assays were again performed.Sampling for the assays from primary and subcultures was done as described previously. The results presented here were derived from three separate experiments, using different M. leprae strain in each experiment. In each experiment, triplicate assays were done for each concentration of every drug including rifampin.Susceptibility of M. leprae to bipyridyls. In the control cultures (without drugs), metabolic activity of M. leprae in primary cultures at 4 weeks was 143% of that at zero hour (Table 1). When the cells from these primary cultures were transferred to fresh DH medium, the activity in subcultures was 134% of the original at zero hour of these subcultures (143% increase in primary cultures was adjusted to 100% at zero hour for subcultures). With VUF-8514 at concentrations of 0.08 ,ug/ml and below, the metabolic activity of M. keprae in primary cultures as well as in subcultures was the same in control cultures. However, when the concentration of VUF-8514 in primary cultures was 0.16 ,ug/ml and higher, no metabolic activity could be detected, suggesting the MIC of VUF-8514 against M. leprae was 0.16 ,ug/ml. When these cells from primary cultures were transferred to fresh drug-free DH medium, cells failed to exhibit any metabolic activity, even after 4 weeks. This suggests the bactericidal activity of VUF-8514 on M leprae. On the other hand, VUF-8842 had no inhibitory effect on the metabolic activity of M leprae even at 0.32 ,ug/ml-the highest concentration tested to compare against rifampin, whose MIC against M leprae has been ...