Resistance Ratio Method Research Articles

Dynamic analysis of single–double-effect absorption chiller with variable thermal conductance during partial-load operation

• This study presents the dynamic analysis with variable thermal conductance. • Resistance ratio method is introduced to capture the variable thermal conductance. • The field test and simulation results have a good agreement. • An effective operation strategy that can improve the system performance is proposed. • The proposed operational approach increases the COP by as much as 32%. A numerical model for the dynamic analysis and control of a solar-assisted single–double-effect absorption chiller is presented. The mathematical model relies on energy and mass balances, which consider the heat and mass storage in each component. The resistance ratio method is introduced to capture the variation in the thermal conductance representing system disturbances and load variations according to the internal and external flow rates. The model was validated with reference to the outlet temperatures of hot, cooling, and chilled water from field test data for a given gas flow rate and corresponding inlet temperatures. The agreement between the field test and simulation results demonstrates the reliability of the model. Deviations between simulated and experimental temperatures mostly stays below 0.5 °C. The model was used to establish an effective operating strategy capable of minimizing the primary energy consumption without affecting the stability of the cooling output capacity and to verify the corresponding beneficial effect. The proposed operational approach increases the coefficient of performance by as much as 32 % compared with the previously implemented operation strategy, reaching up to a maximum value of 10.7 at 60 % cooling capacity.

Gene mutations in resistant strains of Mycobacterium tuberculosis isolated from pulmonary tuberculosis patients in Mazandaran and Golestan provinces of Iran - A cross-sectional study

Due to the significant prevalence of tuberculosis (TB) in Mazandaran and Golestan provinces in northern Iran, we aimed to investigate the gene mutations in resistant Mycobacterium tuberculosis isolated from pulmonary TB patients in these provinces of Iran. In this cross-sectional study, sputum of TB suspected patients were collected and cultured in a period of 3 months. The antibiotic-resistant cases identified using the resistance ratio method. Then, the DNAs of the resistant isolates were extracted manually by the CTAB-Proteinase K method and investigated for gene mutations using PCR and sequencing. Among 26 isolated M. tuberculosis, 4 isolates (15.38%) were resistant to antibiotics, while one (3.84%), 2 (7.69%), and one (3.84%) isolates were resistant to rifampin, isoniazid, and multidrug-resistant (MDR), respectively. The MDR isolate had a mutation in codon 315 of the KatG gene resulting in the conversion of serine to threonine, and a mutation in the codon 450 of the rpoB gene, causing the alteration of serine to leucine. In the rifampin-resistant isolate, a mutation occurred at the same locus converting serine to leucine. The low prevalence of antibiotic resistance in this study indicates the appropriate treatment of the patients, however, the single MDR isolate was identified in Mazandaran province.

English

The control of tuberculosis (TB) has become a global health challenge due to the emergence of multidrug-resistant tuberculosis (MDR-TB) in Mycobacterium tuberculosis (MTB). This highlights the need for faster and more accurate detection of tuberculosis cases. The study aims to detect MDR-TB strains of pulmonary tuberculosis using resistance ratio method and to compare the diagnostic value of drug susceptibility testing (DST) with line probe assay (LPA) using Genotype MTBDRplus. All the sputum samples were tested for Acid Fast Bacilli (AFB) by Ziehl-Neelsen’s staining method and were cultured on Lowenstein-Jensen (L-J) media. The identification and confirmation of M. tuberculosis were done using various biochemical tests. DST was carried against the first line of anti-TB drugs. MTB positive samples were subjected to LPA. A total of 57 samples were subjected to DST and LPA for the detection of drug resistance of MTB to RIF and INH after conventional detection methods were applied to all the samples. Among these 57 MTB samples, 11 (19.29%) were resistant to INH, 4 (7.14%) were resistant to RIF; eleven (19.29%) isolates were identified as MDR-TB. LPA revealed 54 MTB positive among 57 MTB culture-positive samples and 3 showed invalid results. In LPA, MDR-TB was found in10 samples (17.54%) in which one was RIF-resistant. The study concludes risk factors that resulted in the development of TB are biomedical, socio-cultural, and behavioral interactions. LPA can be used as a rapid diagnostic technique for the detection of MDR-TB. Key words: Tuberculosis (TB), multidrug resistance (MDR-TB), drug susceptibility testing (DST), line probe assay (LPA). &nbsp

RESISTENSI Mycobacterium Tuberculosis TERHADAP OBAT ANTI TUBERKULOSIS

Patients infected with resistant Mycobacterium tuberculosis strain will be very difficult to cure by standard treatment. To evaluatethe drug resistance of Mycobacterium tuberculosis. A Cross sectional study was performed from January until July 2005. Samples wereobtained from sputum of the suspect tuberculosis. All samples were cultured in Lowenstein-Jensen Media and followed by sensitivity testaccording to resistance ratio method. Of 236 samples, there were 30% positive cultures. The percentage of mono-resistance to Isoniazidwas 70%, to Rifampicin 64.3%, to Ethambutol 62.8% and Streptomycin 64.3%. The percentage of Multi Drug Resistant Tuberculosis(MDR-TB) was 20–40% and the percentage of poly-resistant (Ethambutol and Streptomycin) was 47.1%. The percentage of suspecttuberculosis with positive culture was 30%. There were also found high percentage of mono-resistant, poly-resistant and MDR-TB.

Drug susceptibility profiles of Mycobacterium tuberculosis isolates from Gulbarga, South India

Aim of the workDrug resistance surveillance is a useful tool to assess the effective functioning of tuberculosis (TB) control program. This study was undertaken to know the first line anti tuberculosis drug susceptibility profile of Mycobacterium tuberculosis clinical isolates from the Gulbarga district of South India. MethodsDrug susceptibility test was performed for 102 clinical isolates of M. tuberculosis belonging to new (n=62), treated (n=22) and unknown treatment category (n=18) of TB. All the isolates were tested for susceptibility to first line anti-tuberculosis drugs by minimum inhibitory concentration (MIC) and resistance ratio method (for streptomycin). ResultsThe susceptibility profile of M. tuberculosis to all five first line anti-tubercular drugs was found to be 60.78% (62/102). Overall, multi drug resistance (resistance to at least isoniazid and rifampicin) was observed in 8.82% (9/102) isolates and was found to be higher for treated cases (18.18%). ConclusionsHigh level of drug resistance observed in new cases for isoniazid, rifampicin and ethambutol suggests need for the implementation of drug resistance surveillance studies in order to document the success of the tuberculosis control program in reducing the level of drug resistance.

Multidrug-resistant pulmonary & extrapulmonary tuberculosis: A 13 years retrospective hospital-based analysis.

Background & objectives:Multidrug-resistant tuberculosis (MDR-TB) is a public health problem of great significance in India. In the present study an attempt was made to analyse the progression of MDR-TB pattern during a course of 13 years (2000-2012) among the patient population at a tertiary care centre in New Delhi, India.Methods:Mycobacterial isolates obtained on Lowenstein-Jensen (L-J) medium/BacT/ALERT 3D were identified using AccuProbe molecular identification system, routine biochemical tests or GenoType Mycobacteria CM. Antimycobacterial susceptibility testing was performed using resistance ratio method on L-J medium (2000-2004) and one per cent proportion method on BacT/ALERT 3D system (2005-2012).Results:Of the total 14,849 samples subjected to mycobacterial culture, 6569 pulmonary and 8280 extrapulmonary, 2364 were detected positive for mycobacteria. The average percentage positivity rate was 15.9 per cent (18.9 and 13.6% in case of pulmonary and extrapulmonary samples, respectively). Our study revealed a significant increase (P<0.001) in multidrug resistance by 12 per cent (4.7% in 2000 to 19.8% in 2012). MDR-TB was more in case of pulmonary (28.2%) than extrapulmonary (11.6%) TB (P<0.001). Only 6.5 per cent (154) of mycobacterial isolates were non-tuberculous mycobacteria and rapid growers represented by Mycobacterium fortuitum and M. abscessus were the most commonly isolated species.Interpretation & conclusions:Increase in prevalence of MDR-TB by 12 per cent in the past 13 years is alarming. Policy modifications may have to be done to strengthen the existing TB control programmes to encourage contact tracing and culture and drug susceptibility testing for all smear positive pulmonary cases to ensure early and appropriate therapy.

TO STUDY INCIDENCE OF MULTI DRUG RESISTANT TUBERCULOSIS IN MUMBAI

Ionized and Rifampicin, the two most potent anti-tuberculosis drugs are rendered ineffective in Multidrug-resistant Tuberculosis (MDR-TB). India, China and Russia contribute to more than 62% of MDR-TB globally. In India, endemic areas like Mumbai are “hotspots” for the dissemination of MDR-TB. The aim of the study was to investigate the incidence of MDR-TB in cases of pulmonary tuberculosis in Mumbai. Total hundred and two clinical isolates of.Tuberculosiswas tested in the study. Drug susceptibility testing of these strains were carried by Resistance Ratio method to ant tuberculosis drugs namely Ionized, Streptomycin andEthambutol and by absolute concentration method for Rifampicinand Pyrazinamide. In our study highest resistance (46 %) was observed to INH followed by RF (42.16 %), SM (29.41 %) and EMB (25.49 %). While, resistance to Pyrazinamide (PZ) was least (7.8%). MDR TB cases were found to be 41.18%.There was significant difference between resistance pattern of INH and EMB, INH and SM, PZ and EMB, PZ and SM, EMB and RF, PZ and RF. (chi square with Yates correction =8.5, p<0.01).Detection of MDR TB strain would not only eliminate non-essential use of antibiotics, but would also help in the selection of most effective drug regimen and guide therapy in chronic cases. Article DOI: https://dx.doi.org/10.20319/lijshls.2015.s11.122138 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Unipolar Resistive Switching in ZrO2 Thin Films

Unipolar resistive switching behaviors including bistable memory switching and monostable threshold switching were found in ZrO2 thin films fabricated by a simple sol–gel method with the Ti/ZrO2/Pt structure. The multilevel resistive switching behaviors were also revealed by varying the compliance current from 9 to 38 mA. Physical mechanisms based on a conductive filament model were proposed to explain the resistive switching phenomena and the device breakdown. A figure of merit Z = ρa/ρf was defined as a criterion for evaluating OFF/ON resistance ratio, where ρf and ρa represent the resistivities of the conductive filament and the fracture region of the filament, respectively. The advantages such as unipolar resistive switching, multilevel resistive switching, good scalability, low operation voltage (<5 V), high OFF/ON resistance ratio (>103), nondestructive readout, long retention (>104 s), and simple fabrication method make the ZrO2-based resistive switching device a promising candidate for next-generation nonvolatile memory applications.

Anti-tuberculosis drug resistance pattern among pulmonary tuberculosis patients with or without HIV infection in Mwanza, Tanzania

Anti-tuberculosis drug resistance is a major problem in tuberculosis (TB) control, particularly multi-drug resistance TB (MDR-TB). The objective of this study was to determine the prevalence of primary and acquired anti-TB drug resistance among newly diagnosed pulmonary TB (PTB) and relapse cases. Sputa were collected from newly diagnosed and relapse PTB patients. Drug susceptibility tests (DST) were performed on sputum culture positive isolates of Mycobacterium tuberculosis using resistance ratio method on four first-line anti-TB drugs: rifampicin, isoniazid, ethambutol and streptomycin. Demographic and anthropometric information was collected and HIV status was determined. Of the 523 culture positive isolates, DST results were available for 503 (96%), 455 were new and 48 were relapse cases. Resistance to at least one of the four drugs was observed in 7.8% (39/503) of the isolates, 7.3% (33/455) were new and 12.5% (6/48) were from relapse cases. Mono resistance to isoniazid was higher in both among new 45.5% (15/33) and relapse 50.0% (3/6) cases. Resistance to rifampicin and streptomycin alone was equal 4/33 (12.1%) and only among new cases. Resistance to ethambutol alone was only one among new cases. Overall MDR-TB prevalence was 2.4% (12/503), nine were new and three were relapse cases. MDR-TB was 17.9% (7/39) for rifampicin and isoniazid. Prevalence of HIV was 43.3% and was similar among new and relapse cases and not risk factor for drug resistance. Majority of PTB patients (52%) had BMI below 18 kg/m2. Those with BMI greater than 18 kg/m2 were more likely to develop drug resistance than those with BMI below 18 kg/m2 (P=0.004). With the resurgence of TB and the high prevalence of HIV among TB patients, prevalence of drug resistance is still low both among new and relapses cases. Despite the current low drug resistance, there is a need for continuous monitoring of the resistance.

Comparison of Proportion and Resistance Ratio Methods for Drug Susceptibility Testing of &lt;i&gt;Mycobacterium tuberculosis&lt;/i&gt; Isolated from Patients Attending National Tuberculosis Centre, Nepal

Background: Tuberculosis (TB) is among the most serious infectious cause of global morbidity and mortality. Emergence of Multi-drug resistant tuberculosis (MDR-TB) is posing an increased threat to TB control programs. Drug susceptibility testing (DST) of Mycobacterium tuberculosis (M. tuberculosis) isolates is important for tackling such problems. Setting: National Tuberculosis Centre (NTC), Thimi, Bhaktapur, Nepal. Objectives: Comparative evaluation of two in vitro DST methods in determining susceptibility of M. tuberculosis isolates from patients attending NTC, to front-line anti-TB drugs: (Isoniazid-INH, Rifampicin-RFP, Streptomycin-SM, and Ethambutol-EMB). Methodology: This study was conducted from Sep 2006-Jun 2007. A total of 862 sputum samples (diagnosis or follow up cases) collected from patients (type of patients or their categories was not differentiated in this study) attending NTC bacteriology lab for sputum direct smear microscopy were analyzed using fluorescence microscopy. All smear positive samples, smear negative samples requested for culture were cultured. All culture positive samples confirmed as M. tuberculosis by biochemical tests were processed for DST by both proportion (PR) and resistance ratio (RR) methods. Results: Out of 862 sputum samples analyzed, 226 (26.2%) samples were positive for Acid Fast Bacilli (AFB) by fluorescence microscopy. Among 323 samples 226 smear positive samples and 97 smear negative samples requested for culture), 221 (68.4%) were culture positive, 92 (28.5%) were culture negative and 10 (3.1%) were contaminated. Out of 221 isolates of M. tuberculosis, 57.5% were resistant to one or more drugs by the PR method and 56.6% by the RR method. Similarly, MDR isolates were 29.9% and 29% by PR and RR methods respectively. On correlation analysis using Mc Nemar Chi-square test, no significant difference between the two tests were observed (p&gt;0.05). The results showed high agreement between both methods and agreement rates to INH, RFP, SM and EMB were 93.2%, 93.7%, 93.2% and 94.1% respectively. Similarly, the agreement rates between both methods using kappa analysis showed kappa (k) value of 0.86, 0.85, 0.86 and 0.84 for INH, RFP, SM and EMB respectively, which is believed to be good agreement between both methods (k=0.80 to 1.00: Very good agreement). Conclusion: In conclusion, this study showed that both the Proportion and Resistance ratio methods are equally good for determining drug susceptibility of M. tuberculosis. Keywords: Mycobacterium tuberculosis; Drug Susceptibility Testing; Proportion Method; Resistance Ratio Method. DOI: 10.3126/saarctb.v5i1.3078 SAARC J. Tuber. Lung Dis. HIV/AIDS 2008 Vol.5(1) 13-20

AC electrical resistance measurements of PdH x samples versus composition x

A brief introduction on the transport properties of PdH x system will be presented. The resistance ratio method is the most frequent technique used to measure the interstitial loading of hydrogen atoms into palladium. Using this technique a series of AC electrical resistance measurements of PdH x , demonstrating a stoichiometric values x > 1 obtained by electrochemical method at room temperature and pressure is presented. A full description of the used electrochemical method for preparing the samples PdH x with composition x > 1 and the analysis to determine the achieved composition will be presented. Conclusions on the electrical resistance of PdH x versus composition x and correlated physical phenomena have been done. In particular, these studies show the importance of the electrochemical processes efficiency. In order to have an accurate calculation of x value, precise efficiency amplitude estimation is needed. Our analysis underline the systematic underestimation of the x value in the well known PdH x relative electrical resistance versus x at room temperature as reported in literature.

Evaluation of MGIT 960-Based Antimicrobial Testing and Determination of Critical Concentrations of First- and Second-Line Antimicrobial Drugs with Drug-Resistant Clinical Strains of Mycobacterium tuberculosis

The objectives of this study were to (i) compare agreement of the MGIT 960 system for first-line drugs with a methodology (the resistance ratio method [RRM]) that had been used in clinical trials, relating drug susceptibility to clinical outcome; (ii) compare the performance of the MGIT 960, RRM, and microtiter plate assay (MPA) methodologies for second-line drug testing; and (iii) define critical concentrations for ciprofloxacin and moxifloxacin for liquid-culture-based testing. The large collection of clinical isolates of Mycobacterium tuberculosis (n = 247) used included 176 (71%) multidrug-resistant isolates. The results for MGIT 960 and the RRM for rifampin and isoniazid (n = 200) were in excellent (99 to 100%) agreement for all strains. For streptomycin, 97% of the results at the critical concentration and 92% at high concentration, and for pyrazinamide 92% of results overall, were concordant, but for ethambutol, fewer than 85% (65% for the critical concentration and 84% for the high concentration) of the MGIT-based results were concordant with those for the RRM. The MGIT 960, RRM, and MPA assays (n = 133) correlated well for most second-line drugs tested. For susceptibility to ofloxacin, the MGIT 960 and MPA results were in full agreement. The amikacin and rifabutin results obtained by MGIT 960 agreed with the RRM results in 131 (99%) cases, and for capreomycin, they agreed for 129 of 133 isolates tested (97%). For prothionamide testing, only a limited number of drug-resistant isolates were available for testing and drawing definitive conclusions. We propose critical concentrations of 1.0 microg/ml and 0.125 microg/ml for ciprofloxacin and moxifloxacin, respectively, for liquid-culture-based testing.

Drug resistance in tuberculosis

A drug-resistant strain of Mycobacterium tuberculosis is defined as one differing from the tight distribution of wild strains that have not come into contact with the drug concerned. Sensitivity tests are performed by the absolute concentration method, the resistance ratio method or the proportion method. The hypothesis underlying the proportion method is that there are appreciable differences in inoculum size so that there should be an association between the proportion on drug-free medium and the proportion on drug-containing medium. This hypothesis was not supported by a study on ethionamide-resistant strains. It indicated that variation in the proportion on drug-free medium was due to clumping of the bacilli in the inoculum rather than to differences in the number of bacilli. Hence, the use of the proportion method introduces errors in susceptibility testing. While the method can produce reliable results, it is more time consuming than a minimal inhibitory concentration determination, and should not be adopted as a standard method.

Increase in Electrical Resistivity of Copper and Aluminum Fine Lines

The resistivities of thin films and fine lines of copper (Cu) and aluminum (Al) were measured by a resistance ratio method (referred to as “RR method” hereafter), which measures the ratio of room-temperature resistance to liquid-nitrogen-temperature resistance. This method can predict resistivity exactly without the need for precise and detailed line or film dimension measurements. Thinner films and finer lines have higher resistivities in the case of both Cu and Al, with Cu showing larger resistivity increases (films and lines) than Al . From the present data, we estimated the electron mean free path of Cu to be 55 nm, which is close to most of the previously reported values, and that of Al to be 22 nm. Line resistivities depend not only on the line width but also on line thickness. We propose a simple equation for expressing line resistivity in terms of line thickness and width.

A novel channel resistance ratio method for effective channel length and series resistance extraction in MOSFETs

A resistance ratio method for electrical effective channel length and series resistance extraction is developed and verified on an advanced 0.35 μm LDD CMOS technology. This method avoids the gate bias range optimization required in the widely used “shift-and-ratio” (S&R) method, which is usually technology specific, while retaining the single transistor algorithm nature of S&R.

In Vitro Susceptibility Testing of Mycobacterium tuberculosis Strains to Trifluoperazine

The presence of calmodulin-like protein (CAMLP) has been demonstrated in mycobacteria and it has been observed that there is a positive correlation between levels of CAMLP, phospholipids as well as lipids and growth. Thus the use of trifluoperazine, which is a calmodulin antagonist, would inhibit the growth of mycobacterial cells.The authors carried out In Vitro susceptibility testing of Mycobacterium tuberculosis strains to trifluoperazine with their minimum inhibitory concentrations (MIC) determination. 70 strains of M. tuberculosis isolated from cases of pulmonary as well as extrapulmonary tuberculosis were included. The following antimycobacterial drugs: streptomycin, isonized, rifampicin, ethambutol were tested on Lowerstein and Jenson (LJ) slopes using the resistance ratio method and the proportion method for pyrazinamide testing. All strains and the control H37RV were cultured into Youmans and Karlson's liquid medium and MICS were determined for trifluoperazine.Trifluoperazine MICs ranged between 8-32 μg/ml for strains susceptible to routine antimycobacterial drugs while strains resistant to streptomycin and iso-niazid had lower MIC values, between 8-16 μg/ml. As trifluoperazine is already in human use for psychotic disorders, its antitubercular activity could pave the way for human trials as an antitubercular drug.

Comparison of three molecular assays for rapid detection of rifampin resistance in Mycobacterium tuberculosis.

Multidrug-resistant Mycobacterium tuberculosis (MDR-TB) is an emerging problem of great importance to public health, with higher mortality rates than drug-sensitive TB, particularly in immunocompromised patients. MDR-TB patients require treatment with more-toxic second-line drugs and remain infectious for longer than patients infected with drug-sensitive strains, incurring higher costs due to prolonged hospitalization. It is estimated that 90% of United Kingdom rifampin-resistant isolates are also resistant to isoniazid, making rifampin resistance a useful surrogate marker for multidrug resistance and indicating that second- and third-line drugs to which these isolates are susceptible are urgently required. Resistance in approximately 95% of rifampin-resistant isolates is due to mutations in a 69-bp region of the rpoB gene, making this a good target for molecular genotypic diagnostic methods. Two molecular assays, INNO-LiPA Rif.TB (Innogenetics, Zwijndrecht, Belgium) and MisMatch Detect II (Ambion, Austin, Tex.), were performed on primary specimens and cultures to predict rifampin resistance, and these methods were compared with the resistance ratio method. A third method, the phenotypic PhaB assay, was also evaluated in comparison to cultures in parallel with the genotypic assays. In an initial evaluation 16 of 16, 15 of 16, and 16 of 16 rifampin-resistant cultures (100, 93.8, and 100%, respectively), were correctly identified by line probe assay (LiPA), mismatch assay, and PhaB assay, respectively. Subsequently 38 sputa and bronchealveolar lavage specimens and 21 isolates were received from clinicians for molecular analysis. For the 38 primary specimens the LiPA and mismatch assay correlated with culture and subsequent identification and susceptibility tests in 36 and 38 specimens (94.7 and 100%), respectively. For the 21 isolates submitted by clinicians, both assays correlated 100% with routine testing.

A resistance ratio method for alloy homogeneity control

A simple and rapid method has been developed for the homogeneity control of binary alloys in which the alloying element is in solid solution. This is based on the well-known resistance ratio method for the characterization of high-purity metals, but using resistances determined under liquid nitrogen rather than liquid helium. Resistances are measured by the four-point method using a sample holder for up to eight wire samples, connected to a high precision resistance meter. The sensitivity of the resistance ratio to the composition depends on the matrix and alloying elements, but can be high for dilute alloys, decreasing as the concentration increases. It is also influenced by lattice defects and impurities, which prevent absolute measurements of the composition. Two examples of use are given: cobalt segregation was detected in casting of V-1% Co alloy and was confirmed by neutron activation analysis, and homogeneity checks were carried out on a series of CuCr alloys containing 8 to 60 ppm Cr with a precision of 4 ppm Cr (standard deviation) or better.

Comparison of improved BACTEC and Lowenstein-Jensen media for culture of mycobacteria from clinical specimens

A 4-month trial involving 2,563 routine clinical specimens was conducted to compare the improved BACTEC TB system (12B medium) with the conventional Lowenstein-Jensen (LJ) media for the isolation, identification, and susceptibility testing of mycobacteria. One hundred sixty-two mycobacterial isolates were recovered, 147 (91%) with BACTEC and 118 (73%) with LJ media. Of these, 62 were Mycobacterium tuberculosis complex strains, 59 (95%) of which were isolated with BACTEC and 54 (87%) of which were isolated with LJ media. Of the remaining 100 isolates, which were mycobacteria other than tuberculosis (MOTT), BACTEC and LJ media detected 88 and 64%, respectively. The contamination rate was significantly higher in BACTEC (5%) than in LJ media (3.3%). The mean isolation time for M. tuberculosis complex with BACTEC was 15.5 days, compared with 25.6 days with LJ. For MOTT, the mean isolation times were 5.8 and 21.4 days, respectively. Identification of 32 M. tuberculosis complex isolates and 38 isolates of MOTT by the BACTEC NAP (p-nitro-alpha-acetylamino-beta-hydroxypropiophenone) inhibition test gave 100% agreement with conventional biochemical identifications. The results of susceptibility testing of 18 M. tuberculosis complex isolates with BACTEC agreed completely with those obtained by the resistance ratio method.

Frost Resistance of Subalpine Eucalyptus Species. II. Experiments Using the Resistance Index Method of Damage Assessment

Frost damage to leaves of Eucalyptus pauciflora seedlings was measured by an electrical resistance ratio method. Leaves were exposed to below-freezing temperatures by a liquid bath apparatus that allowed accurate temperature control. Unhardened seedlings exposed to an 18/9°C temperature regime with 12 h-photo- and thermoperiod did not harden significantly, the minimum temperature producing 50% leaf death (T50) remaining higher than - 5° An 18/4°C regime lowered the T50 to - 14° in 50 d, but exposure of hardened seedlings to 18/9°C produced rapid dehardening back to a T50 higher than - 5°. Rapid (1-2°C min-I) cooling to the frost minimum was much more damaging than was the standard (2-4°C h-I) rate used in the experiments.