A novel synergistic enzyme-antibiotic therapy with immobilization of mycobacteriophage Lysin B enzyme onto Rif@UiO-66 nanocomposite for enhanced inhaled anti-TB therapy; Nanoenzybiotics approach

The emergence of antibiotic-resistant and phage-resistant strains of Mycobacterium tuberculosis (M. tuberculosis) necessitates improving new therapeutic plans. The objective of the current work was to ensure the effectiveness of rifampicin and the mycobacteriophage LysB D29 (LysB)enzyme in the treatment of multi-drug resistant tuberculosis (MDR-TB) infection, where new and safe metal-organic framework (MOF) nanoparticles were used in combination. UiO-66 nanoparticles were synthesized under mild conditions in which the antimycobacterial agent (rifampicin) was loaded (Rif@UiO-66) and LysB D29 enzyme immobilized onto Rif@UiO-66, which were further characterized. Subsequently, the antibacterial activity of different ratios of Rif@UiO-66 and LysB/Rif@uio-66 against the nonpathogenic tuberculosis model Mycobacterium smegmatis (M. smegmatis) was evaluated by minimum inhibitory concentration (MIC) tests. Impressively, the MIC of LysB/Rif@uio-66 was 16-fold lower than that of pure rifampicin. In vitro and in vivo toxicity studies proved that LysB/Rif@UiO-66 is a highly biocompatible therapy for pulmonary infection. A biodistribution assay showed that LysB/Rif@UiO-66 showed a 5.31-fold higher drug concentration in the lungs than free rifampicin. A synergistic interaction between UiO-66, rifampicin and the mycobacteriophage lysB D29 enzyme was shown in the computational method (docking). Therefore, all results indicated that the LysB/Rif@UiO-66 nanocomposite exhibited promising innovative enzyme-antibiotic therapy for tuberculosis treatment.

Effective Isolation and Characterization of Mycobacteriophages with the Ability to Lyse Mycobacterium avium subsp. paratuberculosis

Johne's disease (JD), a chronic infectious enteritis of ruminants, causes major economic losses in the dairy industry globally. This enteritis is caused by Mycobacterium avium subsp. Paratuberculosis (MAP). Currently there is no cure for JD and test-based culling has proved ineffective at preventing the spread. To isolate new mycobacteriophages (mbps) that can potentially be used to control JD transmission and infection on dairy farms, we optimized an isolation protocol by fecal spiking and the testing of different isolation solution compositions. Using this protocol, we successfully enhanced the yield of mbps from spiked fecal samples, elevating it from less than 1% to 59%. With this method, we isolated 14 mbps from 475 environmental samples collected from MAP-positive dairy farms, after in-sample enrichment with MAP and the fast-growing M. smegmatis. The sample sources included soil, manure pits, lactation barns, feces, milk, and drain water. After fingerprinting these mbps by restriction enzyme profiling, we concluded that 12 were distinct and novel. Further characterization of their host range revealed that eight were capable of lysing multiple MAP strains. We also studied the cross-resistance, lysogeny, the effect of pH and their antimycobacterial properties in milk replacer. Each novel mbp showed limited cross-resistance and prophage immunity and showed no reduction in the titer in a range of pHs after 4 h. The novel phages were also able to reduce the mycobacterial counts to zero after 8 h in milk replacer. In conclusion, these novel mbps could be considered to be used in the control strategies of JD on farms.

Mycobacteriophage D29 Lysin B exhibits promising anti-mycobacterial activity against drug-resistant Mycobacterium tuberculosis

IMPORTANCE

To combat the rapidly emerging drug-resistant M. tuberculosis, it is now essential to look for alternative therapeutics. Mycobacteriophages can be considered as efficient therapeutics due to their natural ability to infect and kill mycobacteria including M. tuberculosis. Here, we have exploited the mycolyl-arabinogalactan esterase property of LysB encoded from mycobacteriophage D29. This study is novel in terms of targeting a multi-drug-resistant pathogenic strain of M. tuberculosis with LysB and also examining the combination of anti-TB drugs and LysB. All the experiments include external administration of LysB. Therefore, the remarkable lytic activity of LysB overcomes the difficulty to enter the complex cell envelope of mycobacteria. Targeting the intracellularly located M. tuberculosis by LysB and non-toxicity to macrophages take the process of the development of LysB as a drug one step ahead, and also, the interaction studies with rifampicin and isoniazid will help to form a new treatment regimen against tuberculosis.

Alginate-Encapsulated Mycobacteriophage: A Potential Approach for the Management of Intestinal Mycobacterial Disease

Encapsulated medication is a common method of administering therapeutic treatments. As researchers explore alternative therapies, it is likely that encapsulation will remain a feature of these novel treatments, particularly when routes of delivery are considered. For instance, alginate-encapsulation is often favoured where gastric digestion poses an obstacle. When exposed to cations (namely Ca2+), alginate readily forms gels that are resilient to acidic conditions and readily dissociate in response to mid-range pH. This action can be extremely valuable for the encapsulation of phages. The efficient delivery of phages to the intestine is important when considering mycobacteriophage (MP) therapy (or MP prophylaxis) for disseminated mycobacterial infections and chronic gastroenteritis conditions. This study presents the design and in vitro validation of an alginate-encapsulated MP capable of releasing phages in a pH-dependent manner. Ultimately, it is shown that encapsulated phages pretreated with simulated gastric fluid (SGF) are capable of releasing viable phages into simulated intestinal fluid (SIF) and thereby reducing the mycobacterial numbers in spiked SIF by 90%. These findings suggest that alginate encapsulation may be a viable option for therapeutic and prophylactic approaches to the management of intestinal mycobacterial disease, such as Johne's disease.

Intrapulmonary Treatment with Mycobacteriophage LysB Rapidly Reduces Mycobacterium abscessus Burden

Intrinsic and acquired antibiotic resistance in Mycobacterium abscessus presents challenges in infection control, and new therapeutic strategies are needed. Bacteriophage therapy shows promise, but variabilities in M. abscessus phage susceptibility limits its broader utility. We show here that a mycobacteriophage-encoded lysin B (LysB) efficiently and rapidly kills both smooth- and rough-colony morphotype M. abscessus strains and reduces the pulmonary bacterial load in mice. LysB aerosolization presents a plausible treatment for pulmonary M. abscessus infections.

Development of an antimicrobial formulation for control of specimen-related contamination in phage-based diagnostic testing for tuberculosis

AIMS

To develop and evaluate an antimicrobial supplement for use with phage-based tests for rapid detection of drug resistance of tuberculosis (TB).

METHODS AND RESULTS

An antimicrobial formulation containing nystatin, oxacillin and aztreonam (NOA) (final concentrations of 50,000 IU l(-1), 2 mg l(-1), and 30 mg l(-1) respectively) was developed. This formulation was tested for its influence on detection of a number of Mycobacterium tuberculosis (MTB) strains using the phage amplification (FASTPlaque) assay. Addition of the supplement did not lead to significant reduction in assay sensitivity. Antimicrobial efficacy was assessed with a range of Gram-positive and -negative organisms. The NOA supplement had a broad antimicrobial effect. The supplement was tested for its effect on growth of MTB culture, and on determination of rifampicin resistance using the phage-based methodology (FASTPlaque-Response). NOA did not significantly affect the growth of a range of rifampicin susceptible and resistant MTB strains, nor did it have an adverse effect on the number of interpretable results, nor the ability to discriminate between rifampicin susceptibility and resistance.

CONCLUSION, SIGNIFICANCE AND IMPACT OF STUDY

Use of NOA antimicrobial supplement with rapid phage-based tests for TB will increase the proportion of interpretable results obtained, and enable their wider implementation in disease-endemic countries by improved control of specimen-related contamination.

[A study of the bacteriophage-based assay for the detection of pyrazinamide resistance in Mycobacterium tuberculosis]

OBJECTIVE

To set up and evaluate the method of phage amplified biologically assay (PhaB) in rapid detection of pyrazinamide (PZA) resistance.

METHODS

The PhaB assay was developed and applied in detecting PZA resistance in 108 clinical isolates of Mycobacterium tuberculosis and the results were compared with those of the absolute concentration method. The minimum inhibitory concentration (MIC) was detected for all discrepancy isolates.

RESULTS

The results showed that the optimal detecting condition was pH 5.5, PZA 200 microg/ml and 48 h. Of the 108 strains of Mycobacterium tuberculosis, 28 strains were PZA-susceptible and 80 strains were PZA-resistant detected by PhaB; while 32 strains were PZA-susceptible and 76 strains were PZA-resistant by absolute concentration method. Twenty-eight of the 108 strains were PZA-susceptible and 71 were PZA-resistant by the two methods. The concordant isolates of determination of PZA resistance were 99 by the two methods and the concordance rates was 91.7%. There were 9 strains in discordant isolates, of which 7 were the same with MIC method and gene chip in drug susceptibility. If the results of absolute concentration method was the gold standard, the sensitivity, specificity, positive and negative predictive values, as well as accuracy of PhaB assay was 94.7%, 84.8%, 93.4%, 87.5% and 91.7% respectively.

CONCLUSION

The PhaB assay can be used as a rapid screening method for detection of drug susceptibility of PZA in clinical isolates of Mycobacterium tuberculosis.

[The in vitro killing of intracellular Mycobacterium smegmatis by Mycobacteriophage]

OBJECTIVE

To study the effect of Mycobacteriophage on the lysis of intracellular Mycobacterium smegmatis.

METHODS

Peritoneal macrophages from BALB/C mice were incubated with Mycobacterium smegmatis for 4 h, and the extracellular bacteria were removed. Then the infected macrophages were treated for 2 h with normal saline, or different doses of Mycobacteriophages (2.1 x 10(7) PFU, 2.1 x 10(6) PFU, and 2.1 x 10(5) PFU, respectively), all in a volume of 0.1 ml, and then the extracellular phages and Mycobacterium smegmatis were removed by washing. After incubation for 24 h, the number of viable intracellular bacteria was determined. The intracellular changes after infection of host bacteria by bacteriophages in the macrophages were observed by electron microscopy.

RESULTS

The logarithm 10 of viable intracellular bacteria unit was 5.74 +/- 0.18 in the saline group, 4.77 +/- 0.08 in the high dose phage group (P < 0.01), 4.97 +/- 0.17 in the moderate dose phage group (P < 0.01), and 5.33 +/- 0.13 in the low dose phage group (P > 0.05). Electron microscopy confirmed the infection of intracellular bacteria by the bacteriophages and the production of filial bacteriophages.

CONCLUSIONS

Mycobacteriophages phagocytosed by macrophages are capable of killing the infected mycobacteria. The result suggests that the use of Mycobacteriophages is a potentially novel strategy in the treatment of intracellular bacterial infection.

[Comparison between bacteriophage-based assay and BACTEC-960 system in detection of ethambutol resistance in Mycobacterium tuberculosis]

OBJECTIVE

To set up phage amplified biologically assay (PhaB) for rapid detection ethambutol (EMB) resistance and to evaluate the use of PhaB in the detection of EMB resistance.

METHODS

To detect the EMB resistance of 138 clinical isolates of Mycobacterium tuberculosis (MTB) by PhaB and compare it with the results of BACTEC-960 system. The minimal inhibitory concentration (MIC) was detected for all the discrepant isolates.

RESULTS

Of all the 138 strains of MTB clinical isolates, 114 strains were EMB-susceptible and 24 strains were EMB-resistant with BACTEC-960 system while 118 strains were EMB-susceptible and 20 strains were EMB-resistant with PhaB. 112 of the 138 strains were EMB-susceptible and 18 strains were EMB-resistant with the two methods. The concordant isolates in determination of EMB resistance were 130 strains in the two methods and the concordance rate was 94.2%. The disconcordant isolates were 8 strains and the discrepancy rate was 5.8%. The sensitivity, specificity, positive and negative predictive value as well as overall accuracy for the PhaB assay was 75.0% (18/24), 98.2% (112/114), 90.0% (18/20), 94.9% (112/118) and 94.2% (130/138) respectively if the judgment standard was adopted by BACTEC-960 method.

CONCLUSIONS

The PhaB assay can be used for detection of EMB resistance in isolates of MTB easily and quickly in three days. This method do not need special instrument and may be used in rapid screening method for EMB resistance of MTB.

An evaluation of mycophage therapy, chemotherapy and vaccination for control of subsp. infection

The control of ovine Johne's disease (OJD) is important for domestic trade, the viability of farming units and possibly also for public health. Current strategies in Australia have included quarantine and pasture spelling to decrease prevalence and shedding rates and reduce numbers of Mycobacterium paratuberculosis (Mptb) ingested by susceptible sheep. However, alternative procedures are needed and vaccination with Gudair has recently commenced. This review examines prospects for the control of OJD by chemotherapy, vaccination and mycophages. Current chemotherapeutic regimes for treatment of M. paratuberculosis in ruminants are prohibitively expensive and of dubious efficacy, and apart from environmental concerns, mycophage therapy lacks a track record of success against intracellular bacteria. There is substantial evidence that live and killed mycobacterial vaccines reduce the incidence of clinical disease and shedding rates in OJD. An appraisal of recent experimental results suggests that neonatal vaccination with a defined dose of M. paratuberculosis offers the best prospects for the induction of protective Th1-type immunity.

[Study on the method for rapid detection of Mycobacterium tuberculosis by phage amplified biologically assay]

OBJECTIVE

To set up a method for rapid detection of Mycobacterium tuberculosis (MTB) by phage amplified biologically (PhaB) assay and to investigate the optimal test condition.

METHODS

Various test conditions were compared in order to observe the influence on detective results after MTB was infected by Mycobacteriophage. The test condition established was used for detection of sputum samples, and the results were compared with BIOTEC Lab test.

RESULTS

The bacterial concentration of MTB in 200 - 500/ml was detected by PhaB assay at 1 x 10(9) plaque forming unite (PFU)/ml of Mycobacteriophage, 37 degrees C for 60 min. The optimal concentration of virucidal for inactivation of Mycobacteriophage was 100 mmol/ml for 5 min at room temperature. The bacteriolytic plaque was clear at the concentration of 1 x 10(8)/ml indicator cells. Bacterium inactivated by heat can not be infected by Mycobacteriophage. Positive result was observed for control strains of H(37)Rv, H(37)Ra and M. bovis while negative result was obtained for 7 strains of non-Mycobacterium and 16 control strains of non-Tuberculosis Mycobacteria (NTM). The 4 strains of NTM (M. fortuitum, M. intrcellulare, M. aurum, M. phlei) showed positive reaction at higher concentrations (> 1 x 10(5)/ml). The repetition test showed that the differentiation coefficient in batch and inner was all under 15%. There was a significantly difference (P < 0.01) in positive rate between two digestion-decontamination procedure with N-acetyl-cysteine-NaOH liquefacient (94%) and NaOH liquefacient (62%). The positive rate of the samples cultured one day (65%) was significantly higher than that of the samples without preculture (40%). The results for detection of clinical samples by two reagents, ours and BIOTEC Lab, were nearly the same.

CONCLUSION

Because its rapidity, simplicity, and sensitivity, PhaB assay can be used for rapid detection of MTB, but the condition of test is very important.

[A study of standardization to the rapid detection of Mycobacterium tuberculosis based on phage amplified biologically assay]

OBJECTIVE

To evaluate the phage amplified biologically (PhaB) assay in the rapid detection of Mycobacteria tuberculosis in samples.

METHODS

The conditions of the PhaB assay, including various infection times prior to addition of virucide and the effect of the inactivation agents which could inactive the extracellular phages, were investigated and compared. The sensitivity, specificity and accuracy of PhaB assay were tested when it was used in rapid detection of Mycobacterium tuberculosis. Some agents of the method, including Mycobacteriophage, virucide and help cells (Mycobacterium smegmatis) were investigated at different times when they were preserved at 4 degrees C.

RESULTS

(1) The optimal infection time prior to addition of virucide was between 3 and 4 hours. Four percent FAS (ferrous ammonium sulphate) could inactive 1 x 10(9) PFU (plaque-forming unit) in five minutes. (2) The samples were positive when 80 - 200 CFU of Mycobacterium tuberculosis were present. However, the positive rate of non-Tuberculosis Mycobateria (NTM) was varied. All bacteria lived in the respiratory tract were negative. (3) The important agents used in this test showed optical effect when they were preserved at 4 degrees C.

CONCLUSIONS

The method based on mycobacteriophage-amplified biologically assay could rapidly detect Mycobacterium tuberculosis, and it was effective, accurate, and simple to perform. It was appropriate for using in developing countries, compared with a variety of molecular techniques.

[Analysis and evaluation of phage amplified biologically assay, DNA sequencing analysis and single-strand conformational polymorphism for the drug susceptibility testing of Mycobacterium tuberculosis]

OBJECTIVE

To rapidly identify drug-resistant Mycobacterium tuberculosis using phenotypic and genotypic methods and to evaluate the clinical significance of rapid phenotypic susceptibility test by phage amplified biologically assay (PhaB).

METHODS

PhaB, DNA sequencing and polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) were performed on the 91 rifampicin (RFP)-resistant strains (including 82 multi-drug resistant Mycobacterium tuberculosis strains), 42 RFP-susceptible strains, 75 ofloxacin (OFLX)-resistant strains and 40 OFLX-susceptible strains at the same time.

RESULTS

The results obtained using PhaB assay, DNA sequencing and PCR-SSCP were compared with the absolute concentration method. For RFP susceptibility, the accordance, sensitivity and specificity of PhaB were 93%, 92% and 95% respectively; the accordance, sensitivity and specificity of DNA sequencing were 93%, 90% and 100% respectively; those of PCR-SSCP were 90%, 86% and 100% respectively. For OFLX susceptibility, the accordance, sensitivity and specificity of PhaB assay were 95%, 95% and 95%; those of DNA sequencing were 80%, 71% and 98% respectively; those of PCR-SSCP were 75%, 63% and 98% respectively.

CONCLUSIONS

PhaB assay is a low-cost, rapid, and sensitive method and shows high accordance with absolute concentration technology. It can give drug susceptibility test results within 48 - 96 h, and is a promising technology in clinical laboratory.

[Application of rapid detection for rifampin resistance in clinical isolates of Mycobacterium tuberculosis by phage amplified biologically assay]

OBJECTIVE

To set up a rapid detection method for rifampin susceptibility with phage amplified biologically (PhaB) assay and to evaluates its value in the detection of rifampin resistance in clinical isolates of Mycobacterium tuberculosis.

METHODS

The assay was established to detect rifampin resistance in 524 clinical isolates of Mycobacterium tuberculosis, and the result was compared to that of the absolute concentration method. The minimum inhibitory concentration (MIC) was detected by BACTEC MGIT 960 method for the discrepant isolates.

RESULTS

Rifampin susceptibility results were available for 524 strains of Mycobacterium tuberculosis. A total of 223 strains were found to be rifampin resistant and 301 strains were rifampin susceptible detected by PhaB assay, but 211 and 313 strains were respectively found to be rifampin resistant and susceptible by conventional methods. There were 198 and 288 rifampin resistant and susceptible strains both detected by the two methods. The drug susceptibility of 35 strains was the same in 38 discrepant isolates by the PhaB assay and absolute concentration method. The sensitivity, specificity, positive and negative predictive values as well as the overall accuracy for the PhaB assay was 93.8%, 92.0%, 88.8%, 95.7% and 92.7% respectively if the judgment standard was adopted by conventional methods.

CONCLUSION

The result of PhaB assay was available within 2 days. This method, which is simple and does not need special equipment, can be used for rapid screening for rifampin resistance from Mycobacterium tuberculosis.

Rapid diagnosis of pulmonary tuberculosis by mycobacteriophage assay

We evaluated FASTPlaqueTB, a recently introduced bacteriophage assay for rapid detection of Mycobacterium tuberculosis complex in sputum specimens, using 169 non-duplicate sputum specimens from patients suspected of pulmonary tuberculosis. The results of 160 specimens were analysed. FASTPlaqueTB assay detected tuberculosis in 77% (46/60) of culture-positive cases. Among the AFB smear-positive cases (n = 47) it had a sensitivity of 76% and specificity of 60% while among AFB smear-negative cases (n = 113) its sensitivity and specificity were 78% and 98%, respectively. The overall sensitivity and specificity of the technique were 77% and 96%, respectively, and the positive and negative predictive values were respectively 92% and 87%. The overall efficiency of the test was 89%. Test results were available in 48 h.

Recent advances in molecular methods for early diagnosis of tuberculosis and drug-resistant tuberculosis

Tuberculosis (TB) remains the main infectious cause of deaths in the world. Due to the slow metabolism of the causative agent, Mycobacterium tuberculosis, the isolation, identification and drug susceptibility testing requires several weeks. New techniques have improved specificity, turnaround time and cost effectiveness. Although these methods yield results within hours from sample collection, the clinical significance of each positive result requires rigorous evaluation in most cases. Herein the advantages and disadvantages of the most promising molecular techniques for detection of TB and drug resistance are discussed.

Rapid screening of Mycobacterium tuberculosis for susceptibility to rifampicin and streptomycin

OBJECTIVE

To investigate rapid detection of drug-resistant tuberculosis using the genotypic Inno-LiPA Rif TB assay and a novel, low-cost, bacteriophage-based susceptibility assay.

DESIGN

The performance of the microwell phage replication assay (MPRA) on 18 isolates from suspected multidrug-resistant tuberculosis patients was compared to the LiPA assay performed directly on sputum specimens. Mutations in the rpoB gene identified by LiPA that confer resistance to rifampicin (RMP) were confirmed by DNA sequencing, while susceptibilities were confirmed by the proportion method and BACTEC. A further 19 isolates undergoing routine screening for both RMP and streptomycin susceptibility were included for comparison.

RESULTS

Susceptibility to RMP was determined for 17/18 (94.4%) sputum specimens tested by LiPA. Correlation between MPRA, molecular and conventional methods was 100% for the detection of RMP susceptibility. However, for susceptibility to streptomycin one discrepant result was found: an isolate susceptible to streptomycin by the proportion method was found resistant by MPRA to 2 microg/ml of streptomycin. Similarly, an isolate initially resistant by MPRA upon re-testing was found susceptible in agreement with the conventional method.

CONCLUSION

LiPA enables rapid detection of drug-resistant infection, while MPRA offers simple, low-tech testing of drug susceptibilities that may be appropriate for application in low-income countries.

Evaluation of a bacteriophage-based assay (phage amplified biologically assay) as a rapid screen for resistance to isoniazid, ethambutol, streptomycin, pyrazinamide, and ciprofloxacin among clinical isolates of Mycobacterium tuberculosis

Rapid molecular assays for the detection of mutations associated with rifampin resistance in Mycobacterium tuberculosis are commercially available. However, they are complex and expensive and have predictive values of 90 to 95%. Molecular assays for other drugs are less predictive of resistance. Ideally, assays based on phenotypic markers should be used for susceptibility testing, but these can take weeks to complete. We previously described a rapid phenotypic assay, the phage amplified biologically (PhaB) assay, for the rapid determination of rifampin and isoniazid susceptibility in clinical isolates of M. tuberculosis. In this study, we extended the assay to the study of ethambutol, pyrazinamide, streptomycin, and ciprofloxacin. After the optimization of antibiotic concentrations and incubation conditions, the assay was applied to each drug for a total of 157 isolates. The correlations between the results of the PhaB assay and the resistance ratio method were 94% for isoniazid, 96% for streptomycin, 100% for ciprofloxacin, 88% for ethambutol, and 87% for pyrazinamide. For ciprofloxacin, ethambutol, and pyrazinamide, significantly better correlations were found when a 90% reduction in plaque count was used as the cutoff. Turnaround times for the PhaB assay were 2 to 3 days, compared with 10 days for the resistance ratio method. We believe that this low-cost assay may have widespread applicability for the rapid screening of drug resistance in M. tuberculosis isolates, especially in developing countries.

Evaluation of reverse transcription-PCR and a bacteriophage-based assay for rapid phenotypic detection of rifampin resistance in clinical isolates of Mycobacterium tuberculosis

New rapid phenotypic assays for the detection of rifampin resistance in Mycobacterium tuberculosis have recently been described, but most of these require liquid cultures, which reduces the utility of many tests in terms of turnaround times. In the United Kingdom, over 90% of rifampin-resistant isolates are also resistant to isoniazid, so rifampin resistance can be used as a sensitive marker for multidrug-resistant tuberculosis. In this study, two new rapid phenotypic assays were compared to the standard resistance ratio method on 91 clinical isolates of M. tuberculosis. One, the phage amplified biologically (PhaB) assay, has been described previously and is based on the inability of susceptible isolates of M. tuberculosis to support the replication of bacteriophage D29 in the presence of inhibitory doses of rifampin. The other employed reverse transcription (RT)-PCR to demonstrate a reduction in inducible dnaK mRNA levels in susceptible isolates treated with rifampin. After incubation for 18 h with 4 microg of rifampin per ml, the PhaB assay showed concordance with the resistance ratio method for 46 of 46 (100%) susceptible and 31 of 31 (100%) resistant isolates, while RT-PCR showed concordance for 46 of 48 (96%) susceptible and 35 of 36 (97%) resistant isolates. We believe these assays provide a reliable rapid means of susceptibility testing with a total turnaround time of only 48 h, although the PhaB assay is better in terms of its lower technical demand and cost and its applicability to tuberculosis susceptibility testing in developing countries.

Light and electron microscope studies of mycobacterium--mycobacteriophage interactions. III. Further studies on the ultrathin sections

The process of multiplication of mycobacteriophage B-1 in its host cell was studied by means of an improved technic of ultrathin sectioning. The appearance of the nuclear apparatus was not altered throughout the latent period. Phage-shaped dense particles appeared about 30 minutes after infection in less dense areas neighboring the nuclear apparatus and occasionally at the margin of the nuclear apparatus. The less dense areas, which may correspond to the phage multiplication foci according to the authors' interpretation, were not filled with such arrays of fine-stranded fibrils as are seen in the nuclear apparatus. Empty phage heads could frequently be seen within and outside the lysed cells, along with the mature phage particles, at the end of the latent period. Moreover, it was indicated that empty head membranes may possibly exist within the cells during the latent period

Alteration of colony morphology of mycobacteria associated with lysogeny

White, Arthur (University of Louisville, Louisville, Ky.), Frances Foster, and Linda Lyon. Alteration of colony morphology of mycobacteria associated with lysogeny. J. Bacteriol. 84:815-818. 1962.-Smooth colonies of mycobacteria were obtained from previously rough strains after exposure to phages R(1) and D-32 in a higher frequency than could be expected from selection of mutants alone. A high proportion of the smooth colonies were lysogenized. Smooth lysogenized strains maintained both lysogeny and smooth morphology after repeated subcultures on agar or in Tween media. The available evidence suggests that lysogeny with certain mycobacteriophages alters colony morphology by a means other than selection of mutants.

INFECTION OF MYCOBACTERIUM SMEGMATIS WITH D29 PHAGE DNA

DNA extracted from D29 mycobacteriophage produced plaques when plated on Mycobacterium smegmatis 607. The host bacterium did not require alternation such as conversion to protoplasts; cells susceptible to infection with intact phage were susceptible to DNA. The bases found in calf thymus DNA constituted the bases of D29 DNA, adenine being paired with thymine and guanine with cytosine. The dissymmetry ratio (A + T/G + C) was 0.56, and the buoyant density in CsCl was 1.722 with a GC content of 63.77 per cent. The efficiency of plating of the DNA is very much lower than that of intact D29, and it penetrates the host at a slower rate. As does intact phage, D29 DNA requires calcium ions for productive infection of 607. D29 DNA is significantly inactivated by incubation with RNAase, but the inactivation probably results from a complexing with the DNA rather than from enzyme hydrolysis.

[Phage typing of Mycobacterium tuberculosis strains coming from Nicaragua (preliminary report)]

Fifty Nicaraguan strains of Mycobacterium tuberculosis were classified with a scheme of 9 specific phages. A preliminary distribution of characteristic phagotypes of the area is reported, with prevalence of phagotype I (intermedial) (66%), presence of phagotype A (34%) and absence of the rest of the types. Inclusions of phagotypes Bo4 and F-o-WJ within the classification scheme, as well as practical usefulness of the technique in studies directed to disease control, are valued.

[Study using phagetype markers of Mycobacterium tuberculosis strains from Ethiopia. A preliminary study]

Twenty strains of Mycobacterium tuberculosis from Addis Ababa (Ethiopia) are studied by means of the phage typing technique in mycobacteria. The results obtained show the preliminary distribution of phage types belonging to type I (intermediate) and absence of the remaining types. The lysis pattern of autochthonous M. tuberculosis is characterized by a prevalence of sensitivity to phages DS6A, GS4E, BG1, and D34. The early results of sensitivity obtained with phage Bo4 and its assessment within the current scheme for M. tuberculosis classification.

Mycobacteriophage vector systems

Successful application of molecular genetic approaches to the study of mycobacteria necessitates the introduction of recombinant DNA molecules into mycobacterial cells. Efficient methods of introducing DNA into Mycobacterium smegmatis protoplasts have been developed, and the construction of mycobacteriophage recombinant DNA vectors has been initiated. Novel Escherichia coli-Mycobacterium shuttle vectors, termed shuttle phasmids, have been constructed. These vectors were constructed by inserting E. coli cosmids into nonessential regions of mycobacteriophage DNAs. Shuttle phasmids are multifunctional vectors that replicate in E. coli as plasmids and replicate in mycobacteria as phage. The presence of the bacteriophage lambda cos sequences permits the use of the lambda in vitro packaging system for efficient cloning of additional genes into these vectors. Temperate shuttle phasmids have been constructed that can infect and lyse mycobacterial cells or lysogenize mycobacterial cells to stably integrate and express cloned DNA into mycobacterial genomes. Shuttle phasmids can be transduced into a wide variety of mycobacterial species and thus should permit the development of molecular genetic systems for the mycobacteria.

Bacteriophage typing of Mycobacterium tuberculosis cultures from incidents of suspected laboratory cross-contamination

Bacteriophage typing was performed on 235 Mycobacterium tuberculosis cultures submitted from 31 laboratories. In each instance, either the attending physician questioned the misdiagnosis of tuberculosis or the laboratory supervisor suspected that laboratory cross-contamination had occurred. Phage typing data confirmed these suspicions. Phage typing is a useful adjunct in the investigation of suspected cross-contamination of laboratory cultures of M. tuberculosis.

Preliminary studies on bacteriophage typing of Mycobacterium tuberculosis strains isolated in Salamanca (Spain)

A phage typing of 202 strains of Mycobacterium tuberculosis isolated in Central and Northwest Spain was carried out. The commonest phage type was A (64%) and within this type A (45%). This was followed in frequency by phage type B (26%) and in last place type I (10%). No relationship was observed between the phage type and the geographical or anatomical origin of the strains.

Phage typing of the Mycobacterium avium-intracellulare-scrofulaceum complex. A study of strains of diverse geographic and host origin

A total of 339 strains of the Mycobacterium avium-intracellulare-scrofulaceum complex were phage typed using our previously described technique and 11 typing phages. These included 235 strains of human origin obtained from state health laboratories in Virginia, Georgia, Florida, and Arkansas, 26 strains isolated from persons with AIDS, 38 strains isolated from animals, and 40 environmental isolates. A phage-typing scheme was developed that denotes sensitivity to 8 primary typing phages: the JF group (JF1, JF2, JF3, and JF4), phage D302, and the AN group (AN3, AN9, and AN1-8). The 3 auxiliary phages (VC3, VA6, and D32) define subgroups of the strains sensitive to the AN phages. A total of 99 strains were sensitive to at least 1 phage. Of 31 serotype 1 or 2 strains from animals, 13 were sensitive to AN phages but resistant to JF phages. In contrast, 7/33 serotype 4 or 8 strains from animals or from persons with AIDS were sensitive to JF phages but not to the AN phages. Of the clinical isolates not associated with AIDS, 78/235 were phage sensitive. These strains could be divided roughly into 4 groups: sensitive to AN phages, sensitive to JF phages, sensitive to phage D302, and sensitive to multiple phages. Only 1 of the environmental isolates was phage sensitive. The results indicate that phage typing can subdivide this heterogeneous group of organisms and is a useful tool for epidemiological studies.

The usefulness of phage typing Mycobacterium tuberculosis isolates

Mycobacteriophage typing of Mycobacterium tuberculosis isolates was used as an epidemiologic aid in investigating the transmission of tuberculosis in community, industrial, and institutional outbreaks. The technique was also useful in other situations, e.g., documenting congenital transmission of infection and distinguishing exogenous reinfection from endogenous reactivation. Additional studies are indicated to further explore the value of phage typing for tracking the transmission of tuberculosis in the community.

Phage-typing and drug-resistance patterns as tools in mycobacterial epidemiology

Phage-typing by itself was not sufficient to delineate the boundaries of a mini-epidemic of tuberculosis in upstate New York. Drug-resistance patterns were needed as well. In a small upstate community, 79% of 14 isolates tested were resistant to one or more of the antituberculosis drugs. Of 15 isolates with phage types determined, 47% were type 1(13), 27% were type 7(7, 13), and 27% were type 1(7, 12, 13). By combining phage-typing and sensitivity testing, we were able to demonstrate that 4 or possibly 5 of the 7 phage-type 1(13) strains are epidemiologically related.