Treatment of chronic drug-resistant pulmonary tuberculosis with rifampin and ethambutol

Twenty patients with chronic pulmonary tuberculosis completed eight months of rifampin-ethambutol treatment. Half the patients received daily 600 mg. rifampin and 25 mg./kg. ethambutol for the first two months and subsequently 15 mg./kg. The others received the same dosage of ethambutol and 450 mg. rifampin daily. The average time of sputum conversion was seven weeks and 11 weeks in the two groups respectively. The patients tolerated these drug regimens well.Rifampin blood levels and urinary excretion were studied monthly during the therapy. They indicated that after a short period of treatment the elimination of this drug became faster owing to increased excretion of rifampin, and particularly of its desacetyl metabolite, in the bile. Liver damage resulted in a slower excretion rate. Rifampin should be taken on an empty stomach because simultaneous food intake reduces the peak blood concentration.     

In Vitro Effect of Rifampin on Mycobacteria

Rifampin inhibited 20 strains of Mycobacterium tuberculosis in concentrations of 0.005 to 0.02 mug/ml in 7H-9 broth with Tween 80 and killed all or nearly all of the inoculum in four to eight times greater concentrations. In the same medium without Tween 80, as well as on 7H-10 agar, about 16 to 64 times these amounts were required to produce the same effect. Rifampin was also active against M. kansasii and some of the nonchromogenic mycobacteria. The incidence of mycobacterial cells resistant to rifampin within the cultures studied was in the range of one to four per 10(8) to 10(9) colony-forming units with concentrations of 4 to 125 mug of rifampin per ml. Only one of the Battey cultures and that of M. fortuitum yielded cells resistant to rifampin at 125 mug/ml but not at 500 mug/ml. The same strains yielded more than double that number of organisms resistant to streptomycin and up to 100 times more organisms resistant to isoniazid. All three drugs stopped the growth or reduced the mycobacterial population in growing cultures after contact for 24 to 48 hr. Complete inhibition of growth was produced by rifampin at 1.0 mug/ml in an average of 6 days and by streptomycin at 5.0 mug/ml in 3 days. After an average contact of 10.7 days with rifampin, five of seven strains resumed growth and all strains began regrowth after exposure to streptomycin for 9.4 days. The marked susceptibility of M. tuberculosis and of atypical mycobacteria to rifampin in vitro and the relatively low incidence of resistant mutants suggests that this agent may have clinical usefulness in the treatment of tuberculosis and some other mycobacterioses.     

Antituberculous Therapy in Pregnancy: Risks to the Fetus

A total of 1,939 reported births to mothers who received isoniazid ethambutol, rifampin and streptomycin alone or in combination, for all or part of their pregnancies, were surveyed to determine teratogenicity of these agents. There was no significant increase in birth defects with isoniazid, ethambutol and rifampin, in contrast to the use of streptomycin which was associated with mild auditory and vestibular defects. Guidelines for the treatment of active tuberculosis in pregnancy are therefore established.     

Discriminative effect of rifampin of RNA replication of various RNA bacteriophages.

Rifampin interferes exclusively with RNA replication in vivo of the group I phages MS2, f2, and R17, whereas QbetaRNA replication is unaffected by the drug. In addition, rifampin has a discriminative effect of group I phage RNA replication. In the experimental system employed by us the antibiotic differentially interferes with the synthesis of minus RNA strands in f2, whereas it has almost no effect on the synthesis of progeny plus strands. In MS2, the drug differentially arrests the synthesis of progeny plus strands and almost fails to affect the synthesis of minus RNA strands. In R17 both steps of its RNA replication are affected by rifampin, although each step is only partially (approximately 50%) inhibited. The relation of the present results to the possible role of bacterial proteins and tertiary structure of phage RNA in the process of template recognition is discussed.     

Rifampin alone or with trimethoprim for contacts of children with Haemophilus influenzae type b infections.

We carried out a nonrandomized, unblinded study to compare the efficacy of rifampin alone with that of rifampin in combination with trimethoprim in the eradication of the Haemophilus influenzae type b (HIB) carrier state among contacts of patients with invasive HIB infection. The study population comprised 17 index patients admitted to hospital with severe HIB infections and 233 contacts, 43 of whom had nasopharyngeal colonization with HIB of the same biotype as that of the index patient. Rifampin in a daily dose of 20 mg/kg (maximum 600 mg) for 4 days eradicated the carrier state in 86% of cases, as did the combination of rifampin at the same dosage and trimethoprim in a daily dose of 5 mg/kg (maximum 160 mg) for 4 days.     

Effectiveness of the antibiotics chloramphenicol and rifampin in the treatment of Streptococcus pneumoniae-induced meningitis and systemic infections

Streptococcus pneumoniae, a common pathogen in pediatric infections, has become resistant to penicillin and make these infections difficult to treat. Rifampin and chloramphenicol have been recommended as alternative therapies, since they are less costly and more accessible to communities with limited resources. However, their use may be restricted by the differing levels of resistance found in target populations. The objective was to determine minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) for chloramphenicol and rifampin in strains of S. pneumoniae. These strains were newly isolated from children under age 5 that had demonstrated systemic infections and meningitis. A subgroup of 107 isolates of S. pneumoniae was selected from 324 strains isolated during a period of 2 years (1994-1996). Among these isolates, 60 were penicillin-resistant and 47 were susceptible; 53 isolates were from children with meningitis. MIC and MBC for chloramphenicol and rifampicin were obtained by standard methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). S. pneumoniae ATCC strain 49619 served as the control. An isolate was considered susceptible to chloramphenicol when MIC = 4 microg/ml and resistant when MIC = 8 microg/ml. A strain was considered susceptible to rifampin when MIC = 1 microg/ml and resistant when MIC = 4 microg/ml. MBC was determined by recording the lower concentration of the antibiotic that inhibited 99.9% of the initial inoculum. Chloramphenicol resistance was found in 21% of the 107 isolates. In the group susceptible to penicillin, 11% were resistant to chloramphenicol and in the group resistant to penicillin 28% was resistant to chloramphenicol as well. MBC was found > 4 microg/ml in 28% of the isolates susceptible to penicillin and in 60% of the resistant isolates. No isolates were found resistant to rifampin. However, 2 penicillin resistant isolates showed CBM > 1 microg/ml to rifampin, and one with CIM = 1 microg/ml had a MBC to rifampicin of 16 microg/ml. Meningitis isolates showed higher CIM and CBM than the group of total isolates. These data suggest that chloramphenicol is not recommended for invasive infections caused by S. pneumoniae in Colombia. Rifampin is a more effective therapy in combination with other antibiotics for treatment of this kind of infections. Further studies are necessary to clarify the significance of low levels of MBC to rifampin found in some strains, since this may affect the efficacy of therapies that include this antibiotic.     

Tear lipocalin: potential for selective delivery of rifampin

The potential of ligand binding proteins as drug carriers and delivery systems has recently sparked great interest. We investigated the potential of tear lipocalin (TL) to bind the antibiotic, rifampin, and the environmental conditions for controlled release. To determine if TL binds rifampin, gel filtration was used to isolate protein fractions of tears. Rifampin was detected by absorbance spectroscopy in the elution fractions containing TL. The bound complex of rifampin-TL generates optical activity at about 360 nm, indicating a unique conformation at the binding site. Rifampin has a higher affinity for TL (Kd=128 microM) than albumin. Rifampin is released from the TL calyx in acidic conditions and is displaced by palmitic acid. Autooxidation of free rifampin begins in minutes but is delayed by at least 3 h in the presence of TL. These properties are conducive to stabilization and delivery of rifampin to tubercles that are acidic and rich in fatty acids. These studies show the potential of TL as a carrier for rifampin with controlled release to a targeted environment.     

应用专一性寡核苷酸微阵列可靠地检测结核分枝杆菌利福平耐药性

DNA微阵列代表聚合酶链反应产物诊断测序的发展方向 .根据结核分枝杆菌rpoB基因利福平抗药性决定区域内点突变及其它重排的特征 .研制一种快速地鉴定结核分枝杆菌利福平耐药菌株的中等密度微阵列方法 .利福平抗药性通过使荧光标记扩增遗传物质与微阵列杂交测定 .检测5 3株利福平耐药结核分枝杆菌和 15株利福平敏感结核分枝杆菌 .微阵列方法的检测结果与药物敏感性试验和DNA测序结果完全一致 .临床标本PCR扩增后仅 1 5h可检出利福平耐药临床分离株 .表明寡核苷酸微阵列是高效的、专一性的方法 ,可作为检测利福平抗药性的快速方法以弥补传统培养方法的不足     

Characterization of rpoB mutations associated with rifampin resistance in Mycobacterium tuberculosis from eastern China

Aims:  The aim of this study was to investigate the features of rpoB gene mutations associated with Rifampin (RIF) resistance in Mycobacterium tuberculosis ( M. tuberculosis ) in eastern China.
Methods and Results:  The mutations of rpoB gene in 56 clinical isolates of M. tuberculosis resisted to one to four first-line drugs (rifampin, isonicotinyl hydrazide, ethambutol and streptomycin) were analysed by polymerase chain reaction single strand conformation polymorphism analysis (PCR-SSCP) and DNA sequencing. The results of PCR-SSCP showed 52 isolates were positive (existing rpoB mutation) including 47 isolates resisted to RIF. Subsequent results of DNA sequencing showed that 54 isolates had rpoB gene mutation including 49 isolates resisted to RIF. The most frequently mutated sites were at codons 526 (73·2%), 513 (10·7%) and 531 (3·5%).
Conclusions:  The rpoB codon 526 was the most frequently mutated site of RIF-resistant M. tuberculosis strains in eastern China and its frequency is significantly higher ( P  < 0·0001) compared with that in other areas of China and in other geographic regions worldwide.
Significance and Impact of the Study:  Our results reveal that geographic variation is responsible for rpoB mutations in M. tuberculosis and the resulting information will be helpful to improve a novel rapid molecular drug resistance screening approach for MDR TB.     

Effect of rifampin on the structure and membrane attachment of the nucleoid of Escherichia coli

Deoxyribonucleic acid (DNA) of Escherichia coli was found to be attached to the cell membrane at about 20 points. This was determined by fractionation of X-irradiated cells with the M band (magnesium-Sarkosyl crystals) technique. The number of attachment points was computed from the relationship between the amount of DNA in M bands and the number of double-strand breaks introduced by the X-ray treatment. The number of attachment points was decreased fourfold by treatment of cells with rifampin. This effect was apparently due to the action of the drug on ribonucleic acid (RNA) polymerase since the drug did not affect a mutant whose RNA polymerase is resistant to rifampin. This suggests that there may be two classes of attachment points of DNA on the membrane, some of which are removed by rifampin treatment and some which are not. Rifampin treatment also resulted in the uncondensing of isolated nucleoids and in an axial appearance of the nucleoids in ultrathin sections. The results suggest that RNA polymerase plays a role, direct or indirect, in maintaining the structure of the bacterial nucleoid and in some of its attachment to the membrane.     

In Vitro Chemotherapeutic Combinations Against Isoniazid-Resistant Mycobacterium tuberculosis and Mycobacterium fortuitum

It is an acceptable medical practice to use second-line antimycobacterial drugs in combination with isoniazid in treatment of isoniazid-resistant tuberculosis. Recent investigations have demonstrated the importance of determining chemotherapeutic interaction in instances of multiple antibiotic use. We studied the inhibitory effect of combinations of isoniazid with ethambutol, rifampin, ethionamide, cycloserine, viomycin, and kanamycin against three isoniazid-resistant strains of Mycobacterium tuberculosis and three strains of M. fortuitum. The isobologram technique with drug concentrations of 0.4 to 100 mug/ml was used. With the exception of single instances in which kanamycin plus isoniazid (M. tuberculosis strain 9999) and ethionamide plus isoniazid (M. fortuitum strain 2080) seemed to have a synergistic effect, neither synergy nor antagonism was noted for any of the combinations. These studies show that the combined use of isoniazid and a second line antimycobacterial agent results in vitro in indifferent inhibitory activity.     

Bacteriological conversion in twenty urinary tuberculosis patients treated with ofloxacin, rifampin and isoniazid: a 10-year follow-up study

Twenty patients with urinary tuberculosis were treated with ofloxacin (200 mg/day, 6 months), rifampin (600 mg/day, 3 months) and isoniazid (300 mg/day, 3 months) between 1989 and 1990. All patients were new cases, diagnosed by observation and/or isolation of Mycobacterium tuberculosis in one of the three morning urine samples. Bacteriological culture conversion (negativization) was assessed as a clinical guide of efficacy, comparing it, as the only parameter, against a control group (150 patients) with urinary tuberculosis who received conventional therapy. Bacteriological follow-up studies were performed in both groups monthly for 6 months, then again 6 months later and then every year for 10 years after completion of treatment. In the 20 patients, the initial culture was positive with over 100 colonies per culture (>50%); the smear was positive in 45% of the patients (most were 2+). All strains were susceptible to rifampin, isoniazid and ofloxacin. Two patients discontinued treatment. Beginning with the first month of treatment, the bacteriological conversion was 100%, 89.5% and 100% in the remaining controls. In the control group, which received conventional treatment, the conversion was: 90%, 87%, 93% and 100% in the remaining controls. Treatment with ofloxacin resulted in a bacteriological conversion similar to that following conventional treatment (p>0.05, Fisher's exact test). After 10 years of patient follow-up, we conclude that ofloxacin, in combination with rifampin and isoniazid (both for 3 months only is effective against M. tuberculosis, providing satisfactory bacteriological and clinical efficacy. Electronic Publication     

Intralaboratory comparison of drug susceptibility testing of Mycobacterium tuberculosis by BACTEC and conventional methodology

The BACTEC radiometric method of drug susceptibility testing of Mycobacterium tuberculosis is a reliable and rapid diagnostic tool in clinical mycobacteriology. However, large scale comparative studies have also shown that the level of agreement with standard methodology was less satisfactory with strains resistant to ethambutol and streptomycin than with strains resistant to rifampin and to isoniazid. Since disagreement with drug resistance strains is far more frequent than with drug susceptible strains, it was felt that only the comparison of a large number of resistant strains would be needed to further refine this new technique. The analysis of BACTEC-derived data for isoniazid and rifampin shows that the level of agreement with conventional methodology falls well within accepted limits. Statistical analysis of the radiometric versus conventional comparisons shows no significant differences between the two methods in the case of isoniazid, rifampin, and ethambutol (3 mg/L). Streptomycin and two other ethambutol concentrations tested showed lower levels of agreement and significant statistical differences with conventional methodology.     

Antimicrobial activity of tigecycline alone or in combination with rifampin against Staphylococcus epidermidis in biofilm

Staphylococcus epidermidis is a commensal inhabitant of the healthy human skin, but in the recent years, it has been recognized as a nosocomial pathogen especially in immunocompromised patients. The pathogenesis of S. epidermidis is thought to be based on its capacity to form biofilms on the surface of medical devices, where bacterial cells may persist, protected from host defence and antimicrobial agents. Rifampin has been shown to be one of the most active antimicrobial agents in the eradication of the staphylococcal biofilm. However, this antibiotic should not be used in monotherapy. Therefore, one of the objectives of our research was to study the efficacy of the tigecycline/rifampin combination against methicillin-resistant S. epidermidis embedded in biofilms. Of the 80 clinically significant S. epidermidis isolates, 75 strains possess the ability to form a biofilm. These bacteria formed the biofilm via ica-dependent mechanisms. However, other biofilm-associated genes, including aap (encoding accumulation-associated protein) and bhp (coding cell wall-associated protein), were present in 85 and 29 % of isolates, respectively. The biofilm structures of S. epidermidis strains were also analyzed in confocal laser scanning microscopy (CLSM) and the obtained image demonstrated differences in their architecture. In vitro studies showed that the MIC value for tigecycline against S. epidermidis growing in the biofilm ranged from 0.125 to 2 μg/mL. Tigecycline in combination with rifampin demonstrated higher activity against bacteria embedded in biofilms than tigecycline alone.     

Rifampin disrupts conjugal and chromosomal deoxyribonucleic acid metabolism in Escherichia coli K-12 carrying some IncIalpha plasmids.

The effects of rifampin and chloramphenicol on the transfer of ColIdrd-1 have been examined to determined whether transfer requires the synthesis of an untranslated species of ribonucleic acid (RNA), as proposed in models for the transfer of another IncIalpha plasmid, R64drd-11. When RNA synthesis was inhibited throughout mating by rifampin, ColI transfer between dna+ bacteria occurred at the normal rate for about 10 min and then stopped abruptly. Conjugational deoxyribonucleic acid (DNA) synthesis in dnaB mutants indicates that plasmid DNA was made in the rifampin-treated donors to replace the transferred material but the DNA tended to be unstable. In the presence of chloramphenicol, transfer of ColI gradually diminished over a longer period. Rifampin, but not chloramphenicol, was found to have unpredicted effects on chromosomal DNA metabolism in unmated dna+ and dnaB bacteria when they harbor any of three IncIalpha plasmids (ColIdrd-1, R144drd-3, and R64drd-11). Replication of the bacterial chromosome in such cells stopped abruptly about 15 min after the addition of rifampin, and at 41 degrees C, but not 37 degrees C, this was followed by extensive DNA breakdown. These findings suggest that curtailment of IncIalpha plasmid transfer by the drug results from a general disruption of DNA metabolism rather than from inhibition of a species of RNA essential for transfer.     

The waning of dependence in infant free-ranging yellow baboons (Papio cynocephalus) of Mikumi National Park

Development toward independence during the early years of baboon life is reflected in the infant's transition from riding on its mother to walking on its own during progressions from one location to another. This transition was studied during the first year of life in 55 infants from two differently sized troops living in Mikumi National Park, Tanzania. There was a nearly linear transition in the first year from almost 100% ventral riding to almost 100% walking. The amount of dorsal riding started near zero, reached a plateau lasting from about the 15th to the 26th wk of life, and then gradually declined to zero. Dorsal riding did not replace ventral; rather, dorsal riding increased in frequency until it occurred about as often as ventral riding. Prolonged ventral riding by infants of the smaller of the two troops may have been due to spacing differences or to greater nervousness among members of the smaller troop. There were no significant differences in riding or walking associated with the time of day or the infant's sex. The rate of transition from riding to walking was greatest from about the fifth to the seventh months, which may be especially significant time in the early development of independence.     

Mechanism of Action of Rifampin on Mycobacterium smegmatis

Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase (EC 2.7.7.6) isolated from a rifampin-sensitive strain of Mycobacterium smegmatis was 90% inhibited by 1 mug of rifampin per ml; enzyme from a rifampin-resistant mutant was not affected by this concentration of antibiotic. Inhibition of phenylalanine-1-(14)C incorporation by rifampin in growing cultures was complete about 6 min after addition of antibiotic. Under the same conditions, uracil-2-(14)c incorporated was blocked after 1.5 to 2 min. Rifampin kills M. smegmatis very slowly. When rifampin-inhibited cultures were transferred to a rifampin-free medium, there was a partial resumption of uracil-2-(14)C incorporation, even in the presence of chloramphenicol. We conclude that a primary event in the inhibition of M. smegmatis by rifampin is the block of DNA-dependent RNA polymerase.