BACTEC Radiometric Method Research Articles

Primary drug resistance in pulmonary tuberculosis cases by standard proportion method and BACTEC radiometric method

OBJECTIVE: The objective was to study anti-tubercular drug susceptibility level among 'newly diagnosed' pulmonary tuberculosis (TB) cases by two methods of drug sensitivity testing i.e., standard proportion method (SPM) and BACTEC radiometric method. MATERIALS AND METHODS: Sputum samples from fifty new cases of pulmonary TB were cultured and subjected to antitubercular drug susceptibility testing by using conventional SPM and radiometric method (BACTEC 460 TB system) and compared. RESULTS: Monoresistance was found to be 2%, 8%, 0% and 2% for Streptomycin (S), Isoniazid (H), Rifampicin® and Ethambutol (E), respectively. Any resistance (with or without resistance to other drugs) was 4%, 28%, 10% and 16% for S, H, R and E, respectively. Primary multidrug resistance was 10% (5/50) namely H + R, 6% (3/50); H + R + E, 2% (1/50); H + R + S, 0% (0/50) and H + R + E + S, 2% (1/50). H + E resistance was found in 10% (5/50) of isolates. CONCLUSION: Comparing with other studies, the levels of H, R and multi drug resistance (MDR) were within the expected levels in our study. However, more number of similar studies on drug resistance need to be undertaken regularly to assess the changing trends.

Role of the BACTEC radiometric method in the evaluation of patients with clinically probable tuberculous meningitis

Background:Confirmation of tuberculous meningitis (TBM) and initiation of treatment are often delayed due to limitations in isolating Mycobacterium tuberculosis from cerebrospinal fluid (CSF).Objectives:To evaluate the role of the BACTEC radiometric method in a clinical setting for the early diagnosis of TBM.Materials and Methods:Patients meeting criteria for clinically probable TBM over a 3 year period were included. Clinical features, results of CSF investigations (protein, glucose, cell count, Ziehl-Neelsen staining, culture in Löwenstein-Jensen (LJ) medium and BACTEC) and brain CT imaging were reviewed. Drug sensitivity was tested using BACTEC. Patients were started on standard treatment and functional outcome, and response at discharge and follow-up were assessed. Patients were divided according to whether or not M. tuberculosis was isolated by BACTEC and the clinical, radiological, and laboratory features compared.Results:Sixty patients were evaluated. The mean age was 30 years ± 11.7 years. Headache and fever were the most common symptoms and the mean duration was 26 days. CT findings were hydrocephalus (n=21), basal exudates (n=16), and tuberculoma (n=14). In 40 patients, M. tuberculosis was isolated by BACTEC and average 15 days was required for detection, whereas it was 30 days in LJ medium. Results of drug-sensitivity testing (n=32) were obtained average 7 days after isolation. Patients from whom M. tuberculosis had been isolated by BACTEC more often had tuberculomas in CT imaging (P=0.018).Conclusion:Use of the BACTEC method allows early confirmation in patients with clinically probable TBM. It can guide clinicians in the rational use of anti-tuberculosis treatment by confirming diagnosis and identifying drug- sensitivity.

COMPARATIVE EVALUATION OF BACTEC 460TB SYSTEM AND LOWENSTEIN-JENSEN MEDIUM FOR THE ISOLATION OF M. TUBERCULOSIS FROM CEREBROSPINAL FLUID SAMPLES OF TUBERCULOUS MENINGITIS PATIENTS

Purpose: To evaluate the role of the radiometric BACTEC 460TB system and the conventional Lowenstein-Jensen (LJ) medium for isolation of M. tuberculosis from cerebrospinal fluid (CSF) samples of tuberculous meningitis (TBM) patients. Methods: CSF specimens (n=2325) from suspected TBM patients were processed for isolation of mycobacteria by inoculating BACTEC 12B medium and the LJ medium. The isolation of mycobacteria in both media was confirmed by microscopy and biochemical identification. Drug sensitivity testing for the anti-TB drugs was carried out by BACTEC radiometric method. Results: Among the total 2325 CSF specimens processed by both methods, M. tuberculosis was isolated from 256 specimens. The isolation rates were 93% and 39% for the BACTEC system and LJ medium respectively. Both the media supported growth in 32% of the culture-positive specimens. BACTEC system alone yielded growth in 61% and LJ alone in 7%, of the culture-positive specimens. Among 205 isolates tested for drug susceptibility 81% were sensitive to all the drugs tested and 19% were resistant. Conclusions: The BACTEC 460TB system provides a highly sensitive and rapid tool for the isolation and drug susceptibility testing of M. tuberculosis, from CSF of TBM patients. Use of a solid medium in conjunction with the BACTEC 12B medium is essential for optimal recovery for M. tuberculosis from CSF specimens.

Susceptibility of Mycobacterium tuberculosis Strains to Gatifloxacin and Moxifloxacin by Different Methods

Background: Considering the potentials of gatifloxacin and moxifloxacin in the treatment of tuberculosis, the present study was aimed to define resistance to both these drugs. Methods: Fifty Mycobacterium tuberculosis isolates, consisting of 30 ofloxacin-susceptible and 20 ofloxacin-resistant strains, were tested for their susceptibility to gatifloxacin and moxifloxacin using different susceptibility testing methods, namely the absolute concentration method on Lowenstein-Jensen medium (LJ), the proportion susceptibility testing method (PST) on LJ and 7H11 agar media, and the BACTEC radiometric method. Result: The minimal inhibitory concentration (MIC) of gatifloxacin and moxifloxacin was 1 µg/ml by the absolute concentration method on LJ. In the PST method on LJ and 7H11, using a criterion of ≧1% growth as resistant, there was 100% agreement with the absolute concentration method at a concentration of 0.5 µg/ml for gatifloxacin, and 96% agreement with the BACTEC method at a concentration of 0.25 µg/ml. For moxifloxacin, results by the PST method showed 96% agreement with the absolute concentration method on LJ at a concentration of 1 µg/ml and 92% agreement at a concentration of 0.5 µg/ml for both the absolute concentration method on 7H11 and the BACTEC method. Conclusions: The MICs of gatifloxacin and moxifloxacin were much lower than the MICs of other quinolones like ofloxacin and ciprofloxacin. Additionally, these two drugs have shown a low mean MIC and low concentration as a definition of resistance, which might help in treating the patients with low levels of quinolone resistance.

Actinomycoses and Nocardia pulmonary infections

Actinomycosis and nocardiosis are uncommon pulmonary infections with distinct morphologic features. Both infections most commonly present as chronic, debilitating illnesses with radiographic manifestations simulating lung cancer or tuberculosis. Immunocompromised hosts, however, may develop fulminant disease resembling acute bacterial pneumonia. The purpose of this review is primarily to review the clinical features, diagnosis, and management of actinomycosis and nocardiosis. Treatment of actinomycosis is usually simple, requiring long-term, high-dose intravenous penicillin. Short-course chemotherapy, however, has recently been reported to be successful. Pulmonary nocardiosis is an important cause of opportunistic infection in immunosuppressed patients, and the incidence of this infection is increasing. The sulfonamides are still first-line agents in the management of nocardiosis, but resistance is most common among N. farcinica and N. otitidiscaviarum isolates. Carbapenems should be used as an alternative treatment for severely ill patients. Broth microdilution, E-test (AB Biodisk, Solna, Sweden) and BACTEC (Becton Dickinson, Sparks, Maryland, USA) radiometric method may be more useful in the routine clinical laboratory for antimicrobial testing of aerobic actinomycetes. The practical distinction between the two diseases is in the matter of therapy. Diagnosis depends on a high degree of suspicion so as to alert the microbiology and pathology laboratories to employ special methods to identify the organisms. Early recognition and prompt treatment usually results in complete cure.

Methyltransferase Erm(37) Slips on rRNA to Confer Atypical Resistance in Mycobacterium tuberculosis

Members of the Mycobacterium tuberculosis complex possess a resistance determinant, erm(37) (also termed ermMT), which is a truncated homologue of the erm genes found in a diverse range of drug-producing and pathogenic bacteria. All erm genes examined thus far encode N(6)-monomethyltransferases or N(6),N(6)-dimethyltransferases that show absolute specificity for nucleotide A2058 in 23 S rRNA. Monomethylation at A2058 confers resistance to a subset of the macrolide, lincosamide, and streptogramin B (MLS(B)) group of antibiotics and no resistance to the latest macrolide derivatives, the ketolides. Dimethylation at A2058 confers high resistance to all MLS(B) and ketolide drugs. The erm(37) phenotype fits into neither category. We show here by tandem mass spectrometry that Erm(37) initially adds a single methyl group to its primary target at A2058 but then proceeds to attach additional methyl groups to the neighboring nucleotides A2057 and A2059. Other methyltransferases, Erm(E) and Erm(O), maintain their specificity for A2058 on mycobacterial rRNA. Erm(E) and Erm(O) have a full-length C-terminal domain, which appears to be important for stabilizing the methyltransferases at their rRNA target, and this domain is truncated in Erm(37). The lax interaction of the M. tuberculosis Erm(37) with its rRNA produces a unique methylation pattern and confers resistance to the ketolide telithromycin.

Growth, Congo Red Agar Colony Morphotypes and Antibiotic Susceptibility Testing of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies (subsp.) paratuberculosis (MAP) is the causative agent of Johne's disease in ruminants and has been associated with Crohn's disease in humans. We sought to test growth rates and susceptibilities of various strains of MAP in two available growth media. Paired comparison design. Using the BACTEC macrobroth radiometric growth system and Congo Red-staining agar media, we determined inherent differences in growth characteristics of three bovine and two human strains of MAP and compared susceptibility results obtained in each growth system. Significant differences were observed in growth rate as well as mycobactin J dependence between strains and between a laboratory-adapted isolate of the same strain in the macrobroth system. Similarly, colonial morphology and Congo Red staining on agar media were observed. Two strains, one human and one bovine, demonstrated a 100% rough transparent colony with white coloration on Congo Red agar, while one bovine isolate exclusively grew as a smooth opaque colony with red coloration on Congo Red agar. The remaining strains exhibited mixtures of these two colonial morphotypes on agar media. Comparative susceptibility results between the BACTEC radiometric macrobroth method and the agar proportionality method showed good correlation for most antibiotics/inhibitors tested. However, erratic or poor growth in the macrobroth system prevented minimal inhibitory concentration determinations for two bovine strains by this method. This study demonstrates the variability in the colonial morphology of MAP on Congo Red agar as well as the correlation of antibiotic susceptibility results between the BACTEC macro broth method and the agar proportionality method. This study also emphasizes the need for the development of improved, standardized culture and susceptibility test methods for MAP.

In vitro activity of sitafloxacin (DU-6859a) alone, or in combination with rifampicin, against Mycobacterium ulcerans.

The antimicrobial effect of sitafloxacin (DU-6859a), used either singly or in combination with rifampicin, was evaluated in vitro against Mycobacterium ulcerans. Growth of M. ulcerans was measured by plate counts and the BACTEC radiometric method. The MICs and MBCs of sitafloxacin for M. ulcerans were in the range 0.125-0.5 mg/L. The values for other fluoroquinolones were two- to four-fold higher than for sitafloxacin. Combination of sitafloxacin and rifampicin exhibited synergy with five of the eight strains, whereas the combination of ofloxacin and rifampicin resulted in additive effects only. These results suggest that the combination of sitafloxacin and rifampicin has potential in the treatment of M. ulcerans infection.

Selection of in vitro mutants of pyrazinamide-resistant Mycobacterium tuberculosis

Mutations within the pncA gene coding for pyrazinamidase of Mycobacterium tuberculosis can cause pyrazinamide (PZA) resistance. The effect of drug concentrations on PZA resistance in a clinical isolate of M. tuberculosis was studied in vitro. Serial passage at gradually increased concentrations of PZA from 200 to 500 μg/ml was performed using BACTEC radiometric method. Thirteen in vitro-selected variant strains were assembled and sequence analysis showed that 12 of the 13 variants had a novel single point mutation within the pncA gene by deletion at nucleotide 381 (G), codon 127. This lead to a frameshift that affected the function of the pyrazinamidase resulting in PZA resistance regardless of different PZA concentrations used. One variant had a silent mutation at nucleotide 6 (G→A) and remains PZA sensitive. We conclude that the mutation location found is an important position for full resistance, at least in this strain. The lack of further mutations even after exposure to higher PZA concentrations implies a critical value for development of resistance—a level exceeded in tissues in clinical treatment regimes.

Pyrazinamide-monoresistant Mycobacterium tuberculosis in the United States.

Mycobacterium bovis is naturally resistant to the antituberculosis drug pyrazinamide (PZA). To determine whether all Mycobacterium tuberculosis complex isolates demonstrating PZA monoresistance were truly M. bovis, we examined the phenotype and genotype of isolates reported as PZA monoresistant in five counties in California from January 1996 through June 1999. Isolates reported by local laboratories to be PZA monoresistant were sent to the state reference laboratory for repeat susceptibility testing using the BACTEC radiometric method and to the Centers for Disease Control and Prevention for pncA sequencing and PCR-restriction fragment length polymorphism (RFLP) analysis of the oxyR gene. Of 1,916 isolates, 14 were reported as PZA monoresistant and 11 were available for retesting. On repeat testing, 6 of the 11 isolates were identified as PZA-susceptible M. tuberculosis, 1 was identified as PZA-monoresistant M. bovis, and 1 was identified as M. bovis BCG. The three remaining isolates were identified as PZA-monoresistant M. tuberculosis. Sequencing of the pncA and oxyR genes genotypically confirmed the two M. bovis and the six susceptible M. tuberculosis species. Each of the three PZA-monoresistant M. tuberculosis isolates had different, previously unreported, pncA gene mutations: a 24-bp deletion in frame after codon 88, a base substitution at codon 104 (Ser104Cys), and a base substitution at codon 90 (Ile90Ser). This study demonstrates that PZA monoresistance is not an absolute marker of M. bovis species but may also occur in M. tuberculosis, associated with a number of different mutational events in the pncA gene. It is the first report of PZA-monoresistant M. tuberculosis in the United States.

In vitro activity of KRM-1648, either singly or in combination with ofloxacin, against Mycobacteriumulcerans

The antimicrobial effect of a benzoxazinorifamycin, KRM-1648, either alone or in combination with ofloxacin, was evaluated in vitro against two type strains and six clinical isolates of Mycobacterium ulcerans. Growth of M. ulcerans was measured by plate counts and the BACTEC radiometric method. The minimal inhibitory concentration as well as minimal bactericidal concentration of KRM-1648 against M. ulcerans was between 0.012 and 0.025 mg/l, while corresponding values for rifampicin and rifabutin were in the range of 0.1–0.8 mg/l and 0.1–0.4 mg/l respectively. When combined with ofloxacin, KRM-1648 exhibited strong synergistic activity while only additive effects were observed with the combination of rifampicin (or rifabutin) and ofloxacin. These results suggest that KRM-1648 has a great potential in the treatment of M. ulcerans infection.

Comparison of the in vitro activities of rifapentine and rifampicin against Mycobacterium tuberculosis complex.

The in vitro activity of rifapentine for 44 clinical isolates of Mycobacterium tuberculosis complex was compared with that of rifampicin using the Bactec radiometric method and the absolute concentration method for susceptibility testing. Twenty-nine M. tuberculosis, 11 Mycobacterium bovis and four Mycobacterium africanum strains were studied. Control tests showed that rifapentine was stable for 14 days in 7H9 broth and for 3 weeks in 7H10 agar medium. The 44 M. tuberculosis complex strains were more susceptible to rifapentine than to rifampicin, irrespective of the testing method. In the radiometric system, the MIC50 and MIC90 of rifapentine for M. tuberculosis complex strains were one or two two-fold dilutions lower than those of rifampicin (0.06-0.125 mg/L versus 0.25 mg/L, respectively). By the absolute concentration method, the MIC50 and MIC90 of rifapentine for M. tuberculosis complex strains were two two-fold dilutions lower than those of rifampicin (0.125-0.25 mg/L versus 0.5-1 mg/L, respectively). The MIC90 of rifapentine for the 44 M. tuberculosis complex strains was always 0.25 mg/L, irrespective of the method used, but the radiometric method was more reliable and more reproducible than the agar 7H10 method.

Comparison of three isolation systems for the culture of mycobacteria from respiratory and non-respiratory samples

Aims—To compare the recovery of mycobacteria from clinical samples using the MB/BacT rapid culture system with that obtained using egg medium or the Bactec radiometric method. Methods—The three methods were...

Standardized BACTEC method to measure clarithromycin susceptibility of Mycobacterium genavense.

A standardized clarithromycin susceptibility test for Mycobacterium genavense is reported. The BACTEC radiometric broth dilution test method recommended for Mycobacterium avium complex was modified to develop a reliable and reproducible procedure. Test development involved optimization of medium pH and inoculum densities for antibiotic vials as well as growth control vials. MIC control organisms included Mycobacterium simiae, Mycobacterium avium, and Mycobacterium xenopi. Growth control vials required two to three inoculum dilutions, which varied for each species. Clarithromycin MICs and MBCs for 12 isolates and 1 colonial variant of M. genavense ranged from < or = 0.06 to 0.25 microg/ml.

Multicenter evaluation of mycobacteria growth indicator tube (MGIT) compared with the BACTEC radiometric method, BBL biphasic growth medium and Löwenstein—Jensen medium

OBJECTIVE: To evaluate the new BBL mycobacteria growth indicator tube (MGIT) in comparison with other media. METHODS: MGIT was evaluated in 10 Italian centers on 433 clinical samples, mainly of respiratory origin and mainly smear positive, in comparison with Löwenstein---Jensen and with one or more other methods represented, according to participating centers, by the BACTEC radiometric method or by the biphasic BBL Septi-Chek AFB system. While MGIT and Löwenstein---Jensen were used for all the samples, 285 of them were also inoculated in BACTEC vials and 274 in biphasic bottles. Of these samples, 132 were investigated with all the four methods. RESULTS: Although less rapid and sensitive than the radiometric method, the results of MGIT were equal when compared with the other two media with respect to overall isolation yield; furthermore, it allowed the detection of growth in significantly shorter times. CONCLUSIONS: The results of this study indicate the value of MGIT for the detection of mycobacteria and, thanks to its extreme simplicity of use, its suitability for small and large laboratories. Its combined use with a solid medium can substantially improve the diagnosis of mycobacterial infection.

Comparison of a biphasic non-radiometric system with Lowenstein-Jensen and Bactec-460 system for recovery of mycobacteria from clinical specimens

Setting: The resurgence of tuberculosis and the increase of Mycobacterium avium complex infections have renewed interest in developing more efficient systems for isolation of mycobacteria. The Bactec radiometric method enhances the recovery and shortens the detection time of mycobacteria; however, many clinical laboratories are subject to severe restrictions on the utilization of 14C radiolabelled culture media. Objective: To compare the biphasic MB-Check system in the recovery of mycobacteria from clinical specimens with the Bactec-460 system and Lowenstein-Jensen (LJ) medium. Design: The MB-Check was evaluated for routine use in a clinical laboratory by comparing the rates and times for isolation of mycobacteria from 1840 clinical specimens with results obtained using the other systems. The isolated organisms were identified by standard procedures and specific deoxyribonucleic acid (DNA) probes. Results: The rate of recovery of all mycobacteria with the MB-Check system was 84.8%, compared to 87.5% for the Bactec-460 system and only 64.2% on LJ. Of the 147 M. tuberculosis isolates recovered by all methods combined, 92.5 % were recovered by MB-Check, 87.1% by Bactec and 79.6% on LJ. Of the 109 isolates of nontuberculous mycobacteria (NTM) recovered by all methods combined, 44% were recovered on LJ, 75% by MB-Check and 88% by Bactec ( P < 0.001). A combination of the Bactec and MB-Check systems allowed recovery of 99.2% of isolates. The Bactec system showed a faster detection time than the other two methods. Conclusion: The MB-Check and Bactec systems were more efficient than LJ medium for the isolation of both M. tuberculosis and NTM. The performance of the MB-Check system and the ease with which processing, inspection, detection, and isolation can be performed, indicated that the biphasic approach for cultivation of mycobacteria is feasible and practical. The MB-Check system is more suitable than Bactec system for laboratories that have a small number of specimens or in situations where the disposal of radioactive waste is a problem.

Use of BACTEC radiometric culture method and polymerase chain reaction for the rapid screening of faeces and tissues for Mycobacterium paratuberculosis.

The BACTEC radiometric culture method for detection of Mycobacterium paratuberculosis was evaluated on faeces from cattle on a farm in quarantine for Johne's disease. A multiplex polymerase chain reaction (PCR) based on the IS900 sequence specific for M paratuberculosis and a genus specific 16S rRNA region was developed and used to test cultures showing evidence of mycobacterial growth in the BACTEC liquid radiometric culture medium. Using the BACTEC-PCR combination, confirmation of M paratuberculosis from faeces and tissue of clinically affected animals was achieved within 2 to 4 weeks and 1 week, respectively, a substantial improvement on traditional culture and identification methods. The PCR provided rapid exclusion of M paratuberculosis when other Mycobacterium spp were grown. The radiometric culture medium proved to be very sensitive for culturing Mycobacterium spp.

Synergistic activities of clarithromycin and antituberculous drugs against multidrug-resistant Mycobacterium tuberculosis.

The rise of multidrug-resistant Mycobacterium tuberculosis has complicated therapy for tuberculosis and led us to search for a potentially active combination of drugs against these strains. The susceptibilities of 12 strains of multidrug-resistant M. tuberculosis to standard antituberculous drugs (isoniazid, rifampin, ethambutol, and pyrazinamide), clarithromycin, and its metabolite, 14-hydroxyclarithromycin, were determined by use of the BACTEC radiometric method. All strains were resistant to at least two of the antituberculous drugs. Clarithromycin and 14-hydroxyclarithromycin MICs were in the range indicating resistance at > or = 8.0 micrograms/ml for all strains. Combination testing by the BACTEC method was performed with various concentrations of isoniazid, rifampin, and ethambutol, and with clarithromycin/14-hydroxyclarithromycin at fixed concentrations of 2.0/0.5 micrograms/ml, respectively. Addition of clarithromycin/14-hydroxyclarithromycin to these antituberculous drug mixtures resulted in a 4- to 32-fold reduction in MICs of isoniazid, rifampin, and ethambutol and made resistant strains susceptible. Fractional inhibitory concentrations ranged from 0.23 to 0.50 for all strains, suggesting a synergistic interaction between standard antituberculous drugs and clarithromycin/14-hydroxyclarithromycin. The ability of clarithromycin/14-hydroxyclarithromycin to enhance the activities of isoniazid, ethambutol, and rifampin in vitro suggests that this combination may be efficacious in the treatment of multidrug-resistant M. tuberculosis infections.

In vitro activity of the new difluorinated quinolone sparfloxacin (AT-4140) against Mycobacterium tuberculosis compared with activities of ofloxacin and ciprofloxacin

MICs of the new fluoroquinolone drugs ofloxacin, ciprofloxacin, and sparfloxacin (AT-4140) for 10 strains of Mycobacterium tuberculosis were determined by using both a BACTEC radiometric method and testing on solid 7H11 agar medium. Radiometric MICs by 7H12 broth testing ranged from 0.5 to 1.0, 0.25 to 0.5, and 0.1 to 0.2 microgram/ml for ofloxacin, ciprofloxacin, and sparfloxacin respectively, whereas MICs in solid medium ranged from 0.5 to 1.0, 0.5 to 1.0, and 0.2 to 0.5 microgram/ml, respectively. The bactericidal action of the quinolones compared with their reported peak concentrations in human serum showed that sparfloxacin is the most bactericidal, followed by ciprofloxacin and ofloxacin. Our results suggest the potential of the new difluorinated quinolone sparfloxacin for use against the tubercle bacillus and indicate that further determination of its antimycobacterial spectrum and intracellular efficacy may be fruitful.

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.