Staphylococcus aureus nasal carriage in the community: a survey from central Italy

Recently, concern has increased regarding the spread of methicillin-resistant Staphylococcus aureus (MRSA) in the community. We studied 812 subjects from central Italy to establish the rates of nasal carriage of S. aureus, and antibiotic susceptibility patterns, in the community. The prevalence of S. aureus nasal carriage was 30.5%. Only one subject, with predisposing risk factors for acquisition, was identified as carrier of MRSA (prevalence of 0.12%). The presence of MRSA in the community of our area still appears to be a rare event. Among methicillin-susceptible S. aureus (MSSA) isolates, a surprisingly high rate (18%) of resistance to rifampin was observed.

Putative role of the orphan nuclear receptor SXR (steroid and xenobiotic receptor) in the mechanism of CYP3A4 inhibition by xenobiotics

Cytochrome P450 monooxygenase 3A4 (CYP3A4) is responsible for the metabolism of endogenous steroids and drugs in liver. Many inducers of human CYP3A4, such as rifampicin, bind to the orphan nuclear receptor SXR (steroid and xenobiotic receptor) as ligands and stimulate transcription on xenobiotic response elements located in the CYP3A4 promoter. Conversely, it is not known whether SXR mediates the transcriptional repression. We thus examined transcriptional repression of SXR and its interaction with corepressors, NCoR (nuclear receptor corepressor) and SMRT (silencing mediator for retinoid and thyroid receptors) using reporter assays in the absence and presence of ligand. Cotransfection of SMRT, but not NCoR, inhibited not only basal but also rifampicin-induced transcriptional activity of SXR on the CYP3A4 promoter through specific SMRT-SXR interaction in HepG2 cells. Interestingly, rifampicin also increased the interaction of SXR with SMRT as well as with coactivator SRC-1. On the other hand, the anti-fungal agent ketoconazole decreased SXR interaction with both SRC-1 and SMRT. Ketoconazole partially inhibited corticosterone-induced SXR-mediated transcription on the CYP3A4 promoter. Taken together, our results suggest that the differential interaction of coactivators and corepressors induced by various xenobiotics may alter SXR-mediated transcription. Further, the effects of ketoconazole on the CYP3A4 gene suppression may explain, in part, drug-induced inhibition of the CYP3A4 action at the transcriptional level.

The spectrum of spontaneous rifampin resistance mutations in the rpoB gene of Bacillus subtilis 168 spores differs from that of vegetative cells and resembles that of Mycobacterium tuberculosis

Mutations causing rifampin resistance in vegetative cells of Bacillus subtilis 168 have thus far been mapped to a rather restricted set of alterations at either Q469 or H482 within cluster I of the rpoB gene encoding the beta subunit of RNA polymerase. In this study, we demonstrated that spores of B. subtilis 168 exhibit a spectrum of spontaneous rifampin resistance mutations distinct from that of vegetative cells. In addition to the rpoB mutations Q469K, Q469R, and H482Y previously characterized in vegetative cells, we isolated a new mutation of rpoB, H482R, from vegetative cells. Additional new rifampin resistance mutations arising from spores were detected at A478N and most frequently at S487L. The S487L change is the predominant change found in rpoB mutations sequenced from rifampin-resistant clinical isolates of Mycobacterium tuberculosis. The observations are discussed in terms of the underlying differences of the DNA environment within dormant cells and vegetatively growing cells.

Antibiotic susceptibilities of Parachlamydia acanthamoeba in amoebae

Parachlamydia acanthamoeba are intracellular bacteria of amoebae and are considered potential etiological agents of human pneumonia. We have determined the in vitro antibiotic susceptibilities of two strains (strain Bn(9) and Hall's coccus) in Acanthamoeba polyphaga. The two strains were susceptible to tetracyclines, macrolides, and rifampin, but resistant to fluoroquinolones.

The resurgence of disease: social and historical perspectives on the 'new' tuberculosis

The resurgence of tuberculosis is one of the most serious global public health challenges of the twenty-first century. This paper argues that the decline of tuberculosis since the nineteenth century is far better understood than its resurgence over the last twenty years. It is suggested that insights gained from the historical study of disease may provide a better analytical framework for understanding the contemporary dynamics of disease epidemiology than the current emphasis on the bio-medical and behavioural characteristics of individual patients. It is concluded that tuberculosis research requires a combination of advances in bio-medical knowledge with a broader understanding of the evolving relationship between disease and modern societies.

Antitubercular therapy decreases nitric oxide production in HIV/TB coinfected patients

BACKGROUND

Nitric oxide (NO) production is increased among patients with human immunodeficiency virus (HIV) infection and also those with tuberculosis (TB). In this study we sought to determine if there was increased NO production among patients with HIV/TB coinfection and the effect of four weeks chemotherapy on this level.

PATIENTS AND METHODS

19 patients with HIV/TB coinfection were studied. They were treated with standard four drug antitubercular therapy and sampled at baseline and four weeks. 20 patients with HIV infection but no opportunistic infections were disease controls and 20 individuals as healthy controls. Nitrite and citrulline, surrogate markers for NO, were measured it spectrophotometrically.

RESULTS

Mean age of HIV/TB patients was 28.4+6.8 years and CD4 count was 116+36.6/mm3. Mean nitrite level among HIV/TB coinfected was 207.6+48.8 nmol/ml. This was significantly higher than 99.7+26.5 nmol/ml, the value for HIV infected without opportunistic infections and 46.4+16.2 nmol/ml, the value for healthy controls (p value <0.01). Level of HIV/TB coinfected declined to 144.5+ 34.4 nmol/ml at four weeks of therapy (p value < 0.05). Mean citrulline among HIV/TB coinfected was 1446.8+468.8 nmol/ml. This was significantly higher than 880.8+ 434.8 nmol/ml, the value for HIV infected without opportunistic infections and 486.6+212.5 nmol/ml, the value for healthy controls (p value <0.01). Levels of HIV/TB infected declined to 1116.2+388.6 nmol/ml at four weeks of therapy (p value <0.05).

CONCLUSION

NO production is elevated among patients with HIV infection, especially so among HIV/TB coinfected, but declines significantly following 4 weeks of antitubercular therapy.

Interactions of rifamycin SV and rifampicin with organic anion uptake systems of human liver

The antibiotics rifamycin SV and rifampicin substantially reduce sulfobromophthalein (BSP) elimination in humans. In rats, rifamycin SV and rifampicin were shown to interfere with hepatic organic anion uptake by inhibition of the organic anion transporting polypeptides Oatp1 and Oatp2. Therefore, we investigated the effects of rifamycin SV and rifampicin on the OATPs of human liver and determined whether rifampicin is a substrate of 1 or several of these carriers. In complementary RNA (cRNA)-injected Xenopus laevis oocytes, rifamycin SV (10 micromol/L) cis-inhibited human organic anion transporting polypeptide C (SLC21A6) (OATP-C), human organic anion transporting polypeptide 8 (SLC21A8) (OATP8), human organic anion transporting polypeptide B (SLC21A9) (OATP-B), and human organic anion transporting polypeptide A (SLC21A3) (OATP-A) mediated BSP uptake by 69%, 79%, 89%, and 57%, respectively, as compared with uptake into control oocytes. In the presence of 100 micromol/L rifamycin SV, BSP uptake was almost completely abolished. Approximate K(i) values were 2 micromol/L for OATP-C, 3 micromol/L for OATP8, 3 micromol/L for OATP-B and 11 micromol/L for OATP-A. Rifampicin (10 micromol/L) inhibited OATP8-mediated BSP uptake by 50%, whereas inhibition of OATP-C-, OATP-B-, and OATP-A-mediated BSP transport was below 15%. 100 micromol/L rifampicin inhibited OATP-C- and OATP8-, OATP-B- and OATP-A-mediated BSP uptake by 66%, 96%, 25%, and 49%, respectively. The corresponding K(i) values were 17 micromol/L for OATP-C, 5 micromol/L for OATP8, and 51 micromol/L for OATP-A. Direct transport of rifampicin could be shown for OATP-C (apparent K(m) value 13 micromol/L) and OATP8 (2.3 micromol/L). In conclusion, these results show that rifamycin SV and rifampicin interact with OATP-mediated substrate transport to different extents. Inhibition of human liver OATPs can explain the previously observed effects of rifamycin SV and rifampicin on hepatic organic anion elimination.

Clinically significant interactions with drugs used in the treatment of tuberculosis

Clinically significant interactions occurring during antituberculous chemotherapy principally involve rifampicin (rifampin), isoniazid and the fluoroquinolones. Such interactions between the antituberculous drugs and coadministered agents are definitely much more important than among antituberculous drugs themselves. These can be associated with consequences even amounting to therapeutic failure or toxicity. Most of the interactions are pharmacokinetic rather than pharmacodynamic in nature. The cytochrome P450 isoform enzymes are responsible for many interactions (especially those involving rifampicin and isoniazid) during drug biotransformation (metabolism) in the liver and/or intestine. Generally, rifampicin is an enzyme inducer and isoniazid acts as an inhibitor. The agents interacting significantly with rifampicin include anticoagulants, anticonvulsants, anti-infectives, cardiovascular therapeutics, contraceptives, glucocorticoids, immunosuppressants, psychotropics, sulphonylureas and theophyllines. Isoniazid interacts principally with anticonvulsants, theophylline, benzodiapines, paracetamol (acetaminophen) and some food. Fluoroquinolones can have absorption disturbance due to a variety of agents, especially the metal cations. Other important interactions of fluoroquinolones result from their enzyme inhibiting potential or pharmacodynamic mechanisms. Geriatric and immunocompromised patients are particularly at risk of drug interactions during treatment of their tuberculosis. Among the latter, patients who are HIV infected constitute the most important group. This is largely because of the advent of new antiretroviral agents such as the HIV protease inhibitors and the non-nucleoside reverse transcriptase inhibitors in the armamenterium of therapy. Compounding the complexity of drug interactions, underlying medical diseases per se may also contribute to or aggravate the scenario. It is imperative for clinicians to be on the alert when treating tuberculosis in patients with difficult co-morbidity requiring polypharmacy. With advancement of knowledge and expertise, it is hoped that therapeutic drug monitoring as a new paradigm of care can enable better management of these drug interactions.

Rapid indication of multidrug-resistant tuberculosis from liquid cultures using FASTPlaqueTB-RIF, a manual phage-based test

SETTING

A Mycobacteriology Reference Laboratory in Johannesburg, South Africa.

OBJECTIVE

To determine the ability of FASTPlaqueTB-RIF, a rapid bacteriophage-based test, to correctly identify rifampicin susceptibility in clinical strains of Mycobacterium tuberculosis after growth in the Bactec 460 semi-automated liquid culture system.

DESIGN

A comparative study of FASTPlaqueTB-RIF and conventional drug susceptibility methods, with selection bias to include sufficient rifampicin-resistant strains.

RESULTS

Rifampicin susceptibility results were available for 133 strains of M. tuberculosis. Using the Bactec 460 method, 42 of these strains were rifampicin-resistant and 91 strains were rifampicin-susceptible. A further one strain was found to have a mutation in the rpoB gene which was strongly indicative of rifampicin resistance. Sensitivity, specificity and overall accuracy for the FASTPlaqueTB-RIF were respectively 100%, 98.8% and 99.2% for detection of rifampicin resistance; 95.3% (41/43) of the rifampicin-resistant strains were also resistant to isoniazid (multidrug-resistant).

CONCLUSION

FASTPlaqueTB-RIF offers performance comparable to the Bactec 460 method, with results available within 2 days and without the need for specialised equipment. This makes FASTPlaqueTB-RIF a rapid test for rifampicin resistance suitable for widespread application. A combination of the FAST-PlaqueTB-RIF test with semi-automated liquid culture reduces the time required to report susceptibility results, enabling rapid and appropriate management of patients with MDR-TB. Rifampicin resistance was a good predictor of multidrug resistance in this population.

Rifampin and rifabutin drug interactions: an update

Rifampin is a potent inducer of cytochrome P-450 oxidative enzymes. A few examples of well-documented clinically significant interactions include interactions with warfarin, oral contraceptives, cyclosporine, glucocorticoids, ketoconazole or itraconazole, theophylline, quinidine sulfate, digitoxin or digoxin, verapamil hydrochloride, human immunodeficiency virus-related protease inhibitors, zidovudine, delavirdine mesylate, nifedipine, and midazolam. Recent reports have demonstrated clinically relevant interactions with numerous other drugs, such as buspirone hydrochloride, zolpidem tartrate, simvastatin, propafenone hydrochloride, tacrolimus, ondansetron hydrochloride, and opiates. Rifabutin reduces serum concentrations of antiretroviral agents, but less so than rifampin. To avoid a reduced therapeutic response, therapeutic failure, or toxic reactions when rifampin is added to or discontinued from medication regimens, clinicians need to be cognizant of these interactions. Enhanced knowledge of known interactions will continue to develop, including research on the induction of specific cytochrome P-450 isoenzymes and on the importance of the P-glycoprotein transport system. New rifampin and rifabutin interactions will be discovered with further investigations.

[Testing Mycobacterium tuberculosis for drug sensitivity using different methods]

Testing 35 Mycobacteria tuberculosis strains isolated from patients for drug sensitivity on the Löwenstein-Yersen, Middlebrook 7 H11 midia and by using the polymerase chain reaction demonstrated a correlations of the results obtained by these methods. In laboratory practice, the use of all possible of guidelines for testing Mycobacteria tuberculosis for drug sensitivity.

Molecular characterization of multiple-drug-resistant Mycobacterium tuberculosis isolates from northwestern Russia and analysis of rifampin resistance using RNA/RNA mismatch analysis as compared to the line probe assay and sequencing of the rpoB gene

This investigation evaluated the potential of RNA/RNA mismatch analysis for the detection of rifampin resistance among 38 multiple-drug-resistant (MDR) isolates of Mycobacterium tuberculosis from northwestern Russia. The results obtained were compared with a commercialized line probe assay and rpoB sequencing, and the genetic diversity of the isolates was also investigated in parallel using spoligotyping and variable number of tandem DNA repeats (VNTR). The mismatch analysis revealed 3 distinct RNA cleavage profiles permitting the subdivision of the strains into mutation groups 1 to 3, the most common being group 1 (28 of 38 isolates) that contained a majority of strains with a TCG531>TTG (Ser->Leu) mutation, followed by group 2 (6 of 38 isolates) characterized by different mutations in the codon CAC526 (His), and group 3 (4 of 38 isolates), all characterized by a GAC516(Asp) mutation. Spoligotyping revealed the Beijing type to be the most prevalent among mismatch group 1 (24 out of 28 strains), suggesting that the most frequent rpoB mutation among the Beijing family in our setting was TCG531 >TTG (Ser->Leu). All the Beijing type isolates were also characterized by a unique VNTR pattern made up of exact tandem repeats (ETR)-A to E of 42435. We conclude that the Beijing genotype constitutes the major family of MDR-TB isolates currently circulating in northwestern Russia, and that the in-house RNA/RNA mismatch analysis may be successfully used for rapid and reliable diagnosis of rifampin-resistant tuberculosis in this setting.

Comparison of selection for mutants with reduced susceptibility to ABT-773, erythromycin and rifampicin in respiratory tract pathogens

Attempts were made to select mutants on agar media containing the new ketolide ABT-773, erythromycin or rifampicin, at concentrations above the MICs, from Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae, including erythromycin-resistant strains. ABT-773 did not select for mutants in four strains, whereas in eight strains the frequencies at 72 h were < or = 10(-9). ABT-773 MICs were 0.015-4 mg/L for mutants, except those selected from inducible Erm(A) S. aureus. Mutants selected on ABT-773 or erythromycin were cross-resistant to ABT-773, erythromycin and, sometimes, clindamycin. The susceptibility profiles indicate that different mutations were selected and that ABT-773 and erythromycin may interact with the ribosome differently.

Limitations in the use of rifampicin-gelatin grafts against virulent organisms

OBJECTIVE

Efficacy and duration of antibacterial activity of rifampicin-gelatin grafts against virulent organisms were evaluated in an animal model.

MATERIALS AND METHODS

Rifampicin-gelatin grafts were prepared with impregnation of Gelseal (Vascutek Ltd, Scotland) graft in 1 mg/mL rifampicin solution. Rifampicin-gelatin grafts (6 cm long; n = 24) and plain Gelseal grafts as controls (n = 4) were implanted into the canine abdominal aorta with inoculation of Staphylococcus epidermidis, Escherichia coli, or methicillin-resistant Staphylococcus aureus (MRSA), and the rifampicin-gelatin grafts were retrieved after 1 to 4 weeks. Disks cut from the retrieved rifampicin-gelatin grafts were placed on agar plates streaked with one of the organisms, and the graft antibacterial activity was assessed with the width of the inhibition zone.

RESULTS

In in vitro tests, initial inhibition zones (inhibition zone of 24 hours after incubation) of rifampicin-gelatin grafts against S epidermidis, MRSA, and E coli were 40.0 +/- 0.3 mm, 36.0 +/- 0.2 mm, and 11.8 +/- 0.1 mm, respectively. In the implantation, S epidermidis -inoculated rifampicin-gelatin grafts had no findings of graft infection, and no colony growth was recognized on the plates streaked with the perigraft fluids. Initial inhibition zones of S epidermidis -inoculated rifampicin-gelatin grafts retrieved at 1 or 2 weeks were 20.1 +/- 1.1 mm and 7.6 +/- 1.0 mm, respectively. In E coli -inoculated and MRSA-inoculated rifampicin-gelatin grafts, all of the eight animals had perigraft abscess, and blood culture test results probed septicemia in five animals with patent grafts at death. Inhibition zones against E coli or MRSA were not formed on the plates streaked with the same organism, whereas initial inhibition zones of E coli -inoculated and MRSA-inoculated rifampicin-gelatin grafts on S epidermidis -streaked plates were 8.0 +/- 0.2 mm and 18.5 +/- 0.5 mm, respectively. In the MRSA group, however, recolonization of high minimal inhibitory concentration strains developed within the inhibition zones as early as 24 hours. Histologically, neither organisms nor inflammatory cells were found in S epidermidis -inoculated rifampicin-gelatin grafts and tissue ingrowth was recognized at 2 to 4 weeks, whereas E coli -inoculated and MRSA-inoculated rifampicin-gelatin grafts had aggressive neutrophil infiltration into the graft interstices, revealing establishment of uncontrollable graft infection.

CONCLUSION

These results suggested that rifampicin-gelatin grafts are clearly valid for S epidermidis infection, whereas no efficacy was recognized against either MRSA or E coli graft infection because of early development of high minimal inhibitory concentration MRSA strains or poor susceptibility.

Nested PCR for diagnosis of tuberculous lymphadenitis and PCR-SSCP for identification of rifampicin resistance in fine-needle aspirates

An accurate diagnosis of tuberculosis and multidrug resistance is important for the control of tuberculosis, which remains a major public health problem. Fine-needle aspiration (FNA) has provided an alternative tool for bacterial examination. This study was performed to investigate the usefulness of one-step polymerase chain reaction (PCR) and PCR-SSCP as a routine test for the detection of Mycobacterium tuberculosis and rifampicin-resistant strain in FNA. Ziehl-Neelsen stain (Z-N) and PCR were processed using the aspirates of tuberculous lymphadenitis for the detection of M. tuberculosis. PCR-SSCP was done for the identification of rpoB mutation. M. tuberculosis was detected in 49/63 (77.8%) by PCR and 25/63 (39.7%) by Z-N. There were 26 cases with PCR(+)/Z-N(-) and two cases with PCR(-)/Z-N(+). Twelve cases showed negativity against both. In 7/22 (31.8%), rpoB mutation was observed. In conclusion, PCR is more sensitive in the detection of M. tuberculosis in FNA than Z-N. PCR-SSCP could also be used in FNA in the prediction of multidrug resistance.

Intraspecific variation in the 16S rRNA gene sequences of Mycoplasma agalactiae and Mycoplasma bovis strains

Intraspecific variation in the 16S rRNA genes of 17 Mycoplasma agalactiae and eight Mycoplasma bovis isolates was investigated to determine the degree of sequence variation in these two species and to determine whether the polymorphisms in the 16S rRNA genes could be used for the construction of an evolutionary tree and as epidemiological markers. A high degree of variation was found within isolates (between operons) and between isolates of both species. In contrast to M. capripneumoniae no distinct evolutionary pattern could be seen, probably because there are functional systems for gene conversion in M. agalactiae and M. bovis. However, the non-European isolates of M. agalactiae shared three characteristic nucleotides and European isolates from the same or neighbouring countries were very similar. Differences within isolates included both polymorphic positions and sequence length differences between operons. The amount of variation within isolates of the respective species ranged from zero to seven polymorphisms for M. agalactiae and from zero to four polymorphisms for M. bovis. The high degree of variation suggests the potential for misdiagnosis of species in diagnostic PCR assays based on the 16S rRNA gene sequences. All isolates of both species had a thymidine in position 912 (E. coli numbering) that causes streptomycin resistance in several bacterial species and which is characteristic for the members of the hominis group. As expected, when five M. agalactiae and three M. bovis isolates were tested for streptomycin susceptibility, they all demonstrated streptomycin resistance. M. agalactiae and M. bovis were found to have high intraspecific variation in their 16S rRNA gene and the polymorphisms patterns indicate that gene conversion takes place.

Potential of rifamides to inhibit TNF-induced NF-kappaB activation

Rifamides are important components in the treatment of tuberculosis. However, it is well documented that these drugs can have immunosuppressive activity, a property of these drugs that is particularly relevant to AIDS patients. In this study, we have shown that a number of rifamide analogues have the potential to block tumour necrosis factor (TNF)- or phorbol myristate acetate-induced NF-kappaB activation. As TNF is important in the host defence against tuberculosis, suppression of this activity may provide a potential mechanism of rifamide immunosuppressive activity.

Penetration of rifampin through Staphylococcus epidermidis biofilms

Rifampin penetrated biofilms formed by Staphylococcus epidermidis but failed to effectively kill the bacteria. Penetration was demonstrated by a simple diffusion cell bioassay and by transmission electron microscopic observation of antibiotic-affected cells at the distal edge of the biofilm.

Tuberculosis in Thai prisons: magnitude, transmission and drug susceptibility

BACKGROUND

Because of the human immunodeficiency virus (HIV) epidemic, tuberculosis has reemerged as a major public health problem in Thailand. Prison inmates are at high risk for developing tuberculosis because of the high prevalence of HIV infection.

OBJECTIVES

To determine the magnitude, transmission, and drug susceptibility of tuberculosis in Thai prisons.

SETTINGS

Four provincial prisons in Southern Thailand.

DESIGN

Cross-sectional, descriptive, clinical and molecular study.

RESULTS

Miniature chest roentgenograms were performed on 304 (6.4%) of 4751 inmates screened for a > or = 2 week history of chronic cough and fever. At least 17 (35%) of 49 inmates who had a miniature chest roentgenogram compatible with tuberculosis were HIV-positive. The prevalence of smear-positive pulmonary tuberculosis was 568 per 100,000 inmates, which was eight times higher than that in the general population. Eight (38%) of 21 culture-positive Mycobacterium tuberculosis isolates had DNA fingerprints matching those of another inmate who was housed in the same room or in the same dormitory unit; 39% of the M. tuberculosis isolates were resistant to isoniazid; three of these isolates were also borderline resistant to rifampicin.

CONCLUSION

The prevalence of pulmonary tuberculosis in these prisons was high. A substantial proportion were acquired in the prisons. Isoniazid (INH) resistance was common, and theoretically precludes the use of INH-preventive therapy for contacts of these cases. Active case finding should be done and directly observed therapy implemented to prevent the spread of tuberculosis into the community.

Treatment of childhood tuberculosis with a six month directly observed regimen of only two weeks of daily therapy

BACKGROUND

Recommended treatment of childhood tuberculosis is 6 months in duration with at least 3 drugs. We studied a regimen requiring as few as 58 doses, given entirely by directly observed therapy (DOT), under program conditions.

METHODS

An observational trial was conducted to determine the effectiveness of a completely DOT 6-month regimen for pulmonary, pleural and lymph node tuberculosis in children with the use of 2 weeks of daily isoniazid, rifampin and pyrazinamide therapy; then 6 weeks of twice weekly isoniazid, rifampin and pyrazinamide therapy; followed by 16 weeks of twice weekly isoniazid and rifampin. All therapy was given by workers from the health department, and patients were followed by the Children's Tuberculosis Clinic in Houston, TX. Patients were evaluated for changes in symptoms, weight, clinical or radiographic findings and adherence to therapy.

RESULTS

Of the 175 evaluable children (159 pulmonary/thoracic node, 4 pleural, 12 cervical lymph node), 81% of children completed treatment in 6 months. Of the 33 patients who received extended treatment, 3 did so because of physician choice, 17 had an inadequate response to initial therapy, 2 had significant adverse reactions to drugs and 16 had poor adherence to the DOT. Only 37% of patients had complete resolution of disease at the end of treatment, but all continued to improve after therapy was stopped. There was only 1 patient who relapsed after 4 years.

CONCLUSION

This regimen had results comparable with those of 6-month regimens with longer durations of daily therapy. Determining treatment response in pediatric tuberculosis is difficult because of the slow resolution of chest radiograph abnormalities. DOT is an important aspect of treatment but does not solve all problems with treatment adherence.

Antimicrobial activity of prosthetic heart valve sewing cuffs coated with minocycline and rifampin

Prosthetic heart valve sewing cuffs coated with minocycline and rifampin exhibited in vitro zones of inhibition against all 52 tested clinical isolates responsible for prosthetic valve endocarditis. An in vitro elution study of these coated sewing cuffs demonstrated residual zones of inhibition against Staphylococcus epidermidis for at least 4 weeks.

The effects of rifampicin on the pharmacokinetics and pharmacodynamics of orally administered nilvadipine to healthy subjects

AIMS

To study the effects of rifampicin on the pharmacokinetics and pharmacodynamics of nilvadipine.

METHODS

Five healthy adult volunteers received nilvadipine (4 mg) orally before and after a 6 day treatment with rifampicin. Blood and urine were collected and assayed for plasma nilvadipine and urinary 6beta-hydroxycortisol and cortisol.

RESULTS

The treatment with rifampicin reduced the mean (+/- s.d.) AUC of nilvadipine from 17.4 +/- 8.4 to 0.6 +/- 0.4 microg l-1 h (mean difference -16.8 microg l-1 h, 95% CI -9.4, 24.2 microg l-1 h). While the administration of nilvadipine alone elicited a significant (P < 0.05) hypotensive (mean difference for diastolic blood pressure -8 mmHg, 95% CI -4, -12 mmHg) and reflex tachycardia (mean difference 5 beats min-1, 95% CI 1, 9 beats min-1), the treatment with rifampicin abolished these responses. The urinary 6beta-hydroxycortisol/cortisol ratio showed a significant (P < 0.05) increase from 10.3 +/- 4.0 to 50.3 +/- 24.6 by rifampicin: mean difference 40.1, 95% CI 20.4, 59.8.

CONCLUSIONS

Because rifampicin may greatly decrease the oral bioavailability of nilvadipine, caution is needed when these two drugs are to be coadministered.