Direct SARS-CoV-2 Detection System Utilizing Simple-to-Use Capillary Gel Electrophoresis Sample-to-Result

AIM

We present a Direct SARS-CoV-2 Detection System that achieves sample-to-results in less than two hours in three simple steps.

METHODS

The Detection System includes Direct one-step Reverse Transcription PCR (RT-PCR) reagents (Qexp-MDx kit), a portable thermal cycler (Qampmini) with a preprogrammed chip and a simple-to-use Capillary Gel Electrophoresis system (Qsep Series Bio-Fragment Analyzer) with high fluorescence detection sensitivity to solve the problems associated with traditional real-time PCR (qPCR) systems which produces high false positive results.

RESULTS

The proposed simple-to-use detection platform can provide high detection sensitivity (identify less than 20 copies) and fast results (less than 120 minutes), which would be suitable for field testing applications.

CONCLUSION

Our high detection sensitivity platform provides fast and accurate results in 120 minutes without doing DNA/RNA extraction.

A strategy to recover a poor-quality ligase product

Over the last decades, PCR and molecular cloning have profoundly impacted various biological areas, from basic to pharmaceutical sciences. Presented in this study is a simple and step-by-step protocol that uses PCR to recover a poor-quality ligase product. In fact, a classic step that can be problematic in typical recombinant DNA manipulations can be the recovery of a product from a T4 DNA ligase reaction between two or more suitably prepared DNA fragments (sticky ends, blunt ends, TA cloning, etc.). This reaction can result in poor yields of the ligation product, due to various causes, mainly the preparation of the DNA fragments, and the poor yield can severely invalidate all subsequent steps. To overcome this problem, we designed a pair of PCR primers to amplify the entire ligase product into satisfactory amount. Of course, high-fidelity DNA polymerase must be used to obtain a faithful copy of the DNA of interest. The fragment thus amplified can then be inserted into a suitable vector and propagated by bacterial transformation. We applied this procedure to modify a synthetic gene by adding a His-Tag to its 5' end, and to insert this new construct into an expression cassette. This last step was achieved by employing a PCR cloning system. In our practical example, comprehensive PCR-based protocol with important tips were introduced. This methodological paper can serve as a roadmap for biologists who want to quickly/fully exploit the potential of the PCR-cloning to get desired constructs.

Fungal Profile in Non-Invasive Fungal Sinusitis Using PCR in Post-Covid Scenario at a Tertiary-Care Centre in India

OBJECTIVE

To detect the presence of Mucorales in the sinuses of healthy individuals and non-invasive fungal sinusitis patients.

MATERIALS AND METHODS

Post FESS specimens with appearance suggestive of fungal ball or allergic mucin from 30 immunocompetent patients was sent for KOH smear, HPE, fungal culture and PCR.

RESULTS

Fungal culture was positive for Aspergillus flavus in one specimen. PCR demonstrated Aspergillus (21), Candida (14), and Rhizopus in one case. HPE detected mainly Aspergillus in 13 specimens. No fungal presence in four cases.

DISCUSSION

There was no significant undetected Mucor colonisation. PCR proved to be the most sensitive test in reliably detecting the organisms. No significant variation in the pattern of fungi were detected between COVID-19 infected and non-infected, but for the slightly higher detection of candida in the COVID-19 infected group.

CONCLUSION

There was no significant presence of Mucorales in non-invasive fungal sinusitis patients in our study.

EVALUATION OF PHENOTYPIC AND MOLECULAR TECHNIQUE IN THE DETECTION OF EXTENDED SPECTRUM BETA-LACTAMASE (ESBL)-PRODUCING GRAM NEGATIVE BACILLI IN OGUN STATE, NIGERIA

Background

Molecular diagnosis though faster and more sensitive than phenotypic techniques, is more expensive. Resource limited settings are thus limited to using more of phenotypic rather than molecular methods in the routine detection of Extended Spectrum beta lactamases (ESBL).

Aim

This study aimed to evaluate the performance of double disc synergy test (DSST) and Epsilometer (E) test with Polymerase Chain Reaction (PCR) and to detect the risk factors associated with ESBL producing organisms among in-patients at Babcock University Teaching Hospital, Ilishan-Remo, Nigeria.

Methodology

Hospital-based cross-sectional study in which bacterial isolates of 165 in-patients were collected fromMarch 2018 to September 2019. The isolates were evaluated for ESBL production by the use of DDST, Etest and PCR. The performance evaluation was done. Questionnaire was used to assess the risk factors associated with ESBL, IBM SPSS Version 23 was used to analyze the data.

Results

The participants' isolates yielded 50/165 (30.3%) that were ESBL positive by DDST, 47/165 (28.9%) by E-test and 48/165(29.1%) by PCR. Sensitivity and specificity of DSST was 100% and 98.3% while that of E-test was 98% and 100% respectively. Age, antibiotics intake without prescription, being on ventilator, urethral catheterization and nasogastric tubes were all significantly associated with presence of ESBL (p value <0.05).

Conclusion

Phenotypic tests remain reliable for the routine detection of ESBL in the absence of molecular methods. Rational use of instrumentation and antibiotics is advocated based on the risk factors detected from this study.

Molecular identification and biological control of Ralstonia solanacearum from wilt of papaya by natural compounds and Bacillus subtilis: An integrated experimental and computational study

Ralstonia solanacearum is a harmful pathogen that causes severe wilt disease in several vegetables. In the present study, we identified R. solanacearum from wilt of papaya by 16S rRNA PCR amplification. Virulence ability of R. solanacearum was determined by amplification of approximately 1500 bp clear band of hrpB gene. Further, in-vitro seed germination assay showed that R. solanacearum reduced the germination rate up to 26.21%, 34% and 33.63% of cucumber, bottle guard and pumpkin seeds, respectively whereas shoot and root growth were also significantly decreased. Moreover, growth inhibition of R. solanacearum was recorded using antibacterial compound from medicinal plant and antagonistic B. subtilis. Petroleum ether root extract of Rauvolfia serpentina showed highest 22 ± 0.04 mm diameter of zone of inhibition where methanolic extract of Cymbopogon citratus and ethanolic extract of Lantana camara exhibited 20 ± 0.06 mm and 20 ± 0.01 mm zone of inhibition against R. solanacearum, respectively. In addition, bioactive compounds of B. subtilis inhibited R. solanacearum growth by generating 17 ± 0.09 mm zone of inhibition. To unveil the inhibition mechanism, we adopted chemical-protein interaction network and molecular docking approaches where we found that, rutin from C. citratus interacts with citrate (Si)-synthase and dihydrolipoyl dehydrogenase of R. solanacearum with binding affinity of -9.7 kcal/mol and -9.5 kcal/mol while quercetin from B. subtillis interacts with the essential protein F0F1 ATP synthase subunit alpha of the R. solancearum with binding affinity of -6.9 kcal/mol and inhibit the growth of R. solanacearum. Our study will give shed light on the development of eco-friendly biological control of wilt disease of papaya.

Comparison of chest HRCT severity score in PCR positive and PCR negative clinically suspected COVID-19 Patients

Background

The limitations and false-negative results of Real-time Polymerase chain reaction (RT PCR) in diagnosing COVID-19 infection demand the need for imaging modalities such as chest HRCT to improve the diagnostic accuracy and assess the severity of the infection.

Objectives

The study aimed to compare the chest HRCT severity scores in RT-PCR positive and negative cases of COVID-19.

Methods

This cross-sectional study included 50 clinically suspected COVID-19 patients. Chest HRCT and PCR testing of all 50 patients were done and the chest HRCT severity scores for each lung and bronchopulmonary segments were compared in patients with positive and negative PCR results. Chi-square and Mann Whitney U test were used to assess differences among study variables

Results

Chest HRCT severity score was more in PCR negative patients than in those with PCR positive results. However, the difference was not significant (p=0.11). There was a significant association in severity scores of the anterior basal segment of the left lung (p=0.022) and posterior segment upper lobe of right lung (p=0.035) with PCR results. This association was insignificant for other bronchopulmonary segments (p>0.05).

Conclusion

CR negativity does not rule out infection in clinically suspected COVID-19 patients. The use of chest HRCT helps to determine the extent of lung damage in clinically suspected patients irrespective of PCR results. Guidelines that consider clinical symptoms, chest HRCT severity score and PCR results for a confirmed diagnosis of COVID-19 in suspected patients are needed.

Establishment and Validation of Theileria annulata Sporozoite Ak-93 Infection in Laboratory-Reared Hyalomma anatolicum Tick Using In Vivo and In Vitro Assays

Background:

Tropical Theileriosis caused by Theileria annulata is a tick-borne disease which transmitted by the ixodid tick members of the genus Hyalomma. Studies on different aspects of disease require to access infective sporozoite of parasite which produced by tick vector. This study was carried out to establish of T. annulata life cycle to achieve T. annulata infected ticks.

Methods:

Laboratory rabbit and calf were used for rearing of Hyalomma anatolicum different instars. Unfed nymphs were fed on T. annulata infected calf. Clinical signs, Giemsa stained smears and Polymerase Chain Reaction (PCR) methods were used for detection of infection in blood and tick specimens. Susceptible calf was used for confirmation of sporozoites maturation and infectivity in bioassay test.

Results:

Hyalomma anatolicum two and three-host strategies of life cycle was lasted 90 and 116 days respectively. The PCR confirmed T. annulata infection in blood and tick samples. Maturation of T. annulata sporozoites was confirmed in bioassy test. First clinical symptom of disease was seen earlier in the case of transmission of disease through feeding of live ticks in comparison with blood injection method.

Conclusion:

Complete life cycle of T. annulata was done and confirmed by clinical signs, microscopic examination, molecular methods and bioassay test. According to published reports to date, this is the first report of establishment of H. anatolicum tick infection with T. annulata using susceptible calf under controlled conditions in Iran.

Detection of Antibiotic Resistance Genes Among Multiple Drug Resistant Pseudomonas Aeruginosa Isolated from Clinical Sources in Selected Health Institutions in Kwara State

BACKGROUND

Pseudomonas aeruginosa (P. aeruginosa) is a frequent nosocomial pathogen that causes severe diseases in many clinical and community settings. Strains of P. aeruginosa are associated with increased morbidity, mortality and healthcare costs. The rapid emergence of antimicrobial resistance among these strains is a public health crisis. Moreover, there is a paucity of data on the characterization of P. aeruginosa isolates from human clinical samples in Kwara State.

OBJECTIVES

The objectives of this study are to investigate the occurrence of metallo β-lactamase enzyme, multiple antibiotic resistant P. aeruginosa among clinical samples and detection of antibiotic resistance genes among them.

METHODS

Two hundred and thirty-five samples comprising of 145 males and 90 females human clinical specimens were collected aseptically from five selected health institutions within Kwara State, Nigeria. The samples were cultured immediately using standard microbiological procedures. Multiple drug resistance patterns of the micro-organisms to different antibiotics were determined using the Bauer Kirby disc diffusion technique. Metallo β-lactamase production was determined using E - test strip and the DNA samples of the multiple resistant P. aeruginosa strains were extracted and subjected to Polymerase Chain Reaction (PCR) for resistant genes determination. Data were subjected to descriptive statistics using Statistical Package for Social Sciences (SPSS) software.

RESULTS

A total of 145 isolates were identified for P. aeruginosa from the clinical samples. Thirty were positive for metallo β-lactamase production; 11 (8%) males and 19 (13%) females. Absolute resistance to ceftazidime (100%), gentamicin (100%), ceftriaxone (100%) were observed while low resistance to ciprofloxacin (12.4%), piperacillin (6.9%) and imipenem (6.9%). All isolates were sensitive to colistin. The prevalence of various encoding genes blaVIM, , blaCTX-M and blaTEM were 34.4%, 46.7%, 16.7% and 37.7% respectively.

CONCLUSION

This study has shown that there is a high occurrence of metallo β-lactamase enzyme producing and antibiotic-resistant strains of P. aeruginosa in clinical specimens from the studied area. Necessary measures must, therefore be implemented to stop the problems of this antibiotic resistance.

Adaptive Immunity and the Tumor Microenvironment

The adaptive immune response is a 500-million-year-old (the "Big Bang" of Immunology) collective set of rearranged and/or selected receptors capable of recognizing soluble and cell surface molecules or shape (B cells, antibody), endogenous and extracellular peptides presented by Major Histocompatibility (MHC) molecules including Class I and Class II (conventional αβ T cells), lipid in the context of MHC-like molecules of the CD1 family (NKT cells), metabolites and B7 family molecules/butyrophilins with stress factors (γδT cells), and stress ligands and absence of MHC molecules (natural killer, NK cells). What makes tumor immunogenic is the recruitment of initially innate immune cells to sites of stress or tissue damage with release of Damage-Associated Molecular Pattern (DAMP) molecules. Subsequent maintenance of a chronic inflammatory state, representing a balance between mature, normalized blood vessels, innate and adaptive immune cells and the tumor provides a complex tumor microenvironment serving as the backdrop for Darwinian selection, tumor elimination, tumor equilibrium, and ultimately tumor escape. Effective immunotherapies are still limited, given the complexities of this highly evolved and selected tumor microenvironment. Cytokine therapies and Immune Checkpoint Blockade (ICB) enable immune effector function and are largely dependent on the shape and size of the B and T cell repertoires (the "adaptome"), now accessible by Next-Generation Sequencing (NGS) and dimer-avoidance multiplexed PCR. How immune effectors access the tumor (infiltrated, immune sequestered, and immune desserts), egress and are organized within the tumor are of contemporary interest and substantial investigation.

A novel approach for extracting DNA from formalin-fixed paraffin-embedded tissue using microwave

Background

Formalin-fixed paraffin-embedded (FFPE) tissue is the gold standard procedure for tissue preservation. However, the extraction of DNA is a cumbersome procedure as the extracted DNA is fragmented because of the cross-linking effect of formalin. Hence, the aim of the present study is to extract DNA from FFPE tissues using different techniques with a specific objective of comparing the extracted DNA, both quantitatively and qualitatively.

Method

Ten samples of FFPE tissues were retrieved from the archives of the Department of Oral Pathology. Total genomic DNA was extracted by different methods which included QIAamp DNA FFPE Tissue Kit, Norgen DNA FFPE Tissue Kit, phenol-chloroform method, mineral oil-based extraction, M/10 NaOH solution method, and microwave method. A 280-base pair sequence was selected for evaluation of downstream amplification.

Results

The statistical analysis was performed using unpaired student's t-test to compare the DNA yields and quality obtained by microwave methods with other methods using SPSS software. Total genomic DNA retrieved by the microwave method was superior to other methods both qualitatively and quantitatively.

Conclusion

DNA extraction from FFPE tissues is an onerous task as irreversible bonds form between the nucleic acid during fixation which are difficult to break during DNA retrieval. Hence, the microwave method provides good total genomic DNA which gives better downstream results when compared with other methods.

A fast and reliable polymerase chain reaction method based on short interspersed nuclear elements detection for the discrimination of buffalo, cattle, goat, and sheep species in dairy products

Objective

Aim of present study was the set up of a fast and reliable protocol using species-specific markers for the quali-quantitative analysis of DNA and the detection of ruminant biological components in dairy products. For this purpose, the promoter of the gene coding for the α-lactoalbumin (LALBA) was chosen as possible candidate for the presence of short interspersed nuclear elements (SINEs).

Methods

DNA was isolated from somatic cells of 120 individual milk samples of cattle (30), Mediterranean river buffalo (30), goat (30), and sheep (30) and the gene promoter region (about 600/700 bp) of LALBA (from about 600 bp upstream of exon 1) has been sequenced. For the development of a single polymerase chain reaction (PCR) protocol that allows the simultaneous identification of DNA from the four species of ruminants, the following internal primers pair were used: 5′-CACTGATCTTAAAGCTCAGGTT-3′ (forward) and 5′-TCAGA GTAGGCCACAGAAG-3′ (reverse).

Results

Sequencing results of LALBA gene promoter region confirmed the presence of SINEs as monomorphic “within” and variable in size “among” the selected species. Amplicon lengths were 582 bp in cattle, 592 bp in buffalo, 655 in goat and 729 bp in sheep. PCR specificity was demonstrated by the detection of trace amounts of species-specific DNA from mixed sources (0.25 ng/μL).

Conclusion

We developed a rapid PCR protocol for the quali-quantitative analysis of DNA and the traceability of dairy products using a species-specific marker with only one pair of primers. Our results validate the proposed technique as a suitable tool for a simple and inexpensive (economic) detection of animal origin components in foodstuffs.

Frequency of Human Papillomavirus Genotypes 6, 11, 16, 18 And 31 in Paraffin-Embedded Tissue Samples of Invasive Breast Carcinoma, North- East of Iran

BACKGROUND &OBJECTIVE

Breast cancer is the most common female malignancy. Detection of DNA of human papillomaviruses (HPVs) in breast carcinomas suggests that the virus may play a role in the pathogenesis of this disease. The aim of this study was to evaluate the frequency of HPVs genotypes 6, 11, 16, 18 and 31 in paraffin-embedded tissue samples of invasive breast carcinomas.

METHODS

Three hundred and twenty six paraffin-embedded tissue samples of breast cancer were studied. PCR was performed using specific primers for HPV genotypes.

RESULTS

Of total 206 (63.2%) samples positive for Beta-globin gene, 54 (26.2%) were HPV-positive and 152 (73.8%) were negative for HPV. Distribution of HPV genotypes were as follows: 19 (25.7%) were positive for genotype 11, 5 (6.8%) were positive for genotype 6; and 2 cases (2.7%) were positive for both genotypes 6 and 11. Samples were also screened for HPV genotypes 16, 18 and 31 but none was positive.

CONCLUSION

The current study confirmed the association of HPV and breast cancer. However, all samples were negative for high-risk HPV types 16, 18 and 31.

Importin 8 regulates the transport of mature microRNAs into the cell nucleus

Mature microRNAs (miRNAs), ∼ 22-nucleotide noncoding RNAs regulating target gene expression at the post-transcriptional level, have been recently shown to be transported into the nucleus where they modulate the biogenesis of other miRNAs or their own expression. However, the mechanism that governs the transport of mature miRNAs from cytoplasm to nucleus remains unknown. Here, we report that importin 8 (IPO8), a member of the karyopherin β (also named the protein import receptor importin β) family, plays a critical role in mediating the cytoplasm-to-nucleus transport of mature miRNAs. Specifically knocking down IPO8 but not other karyopherin β family proteins via siRNA significantly decreases the nuclear transport of various known nucleus-enriched miRNAs without affecting their total cellular levels. IPO8-mediated nuclear transport of mature miRNAs is also dependent on the association of IPO8 with the Argonaute 2 (Ago2) complex. Cross-immunoprecipitation and Western blot analysis show that IPO8 is physically associated with Ago2. Knocking down IPO8 via siRNA markedly decreases the nuclear transport of Ago2 but does not affect the total cellular Ago2 level. Furthermore, dissociating the binding of miRNAs with Ago2 by trypaflavine strongly reduces the IPO8-mediated nuclear transport of miRNAs.

Comparison of Culture and PCR Methods for Diagnosis of Mycobacterium tuberculosis in Different Clinical Specimens

Background:

Tuberculosis remains a global epidemic, especially in developing countries, including Iran. Rapid diagnosis of active Mycobacterium tuberculosis infection plays a critical role in controlling the spread of tuberculosis. Conventional methods may take up to several weeks or longer to produce results. In addition to multiplicity of steps involved in conventional detection, including isolation, identification and drug susceptibility testing, the slow growth rate of M. tuberculosis is also responsible for this lengthy time.

Objectives:

The aim of this study was to compare the polymerase chain reaction (PCR) and culture methods for the detection of M. tuberculosis in different clinical specimens.

Materials and Methods:

This study was performed on different samples (urine, gastric aspirate, bronchoalveolar lavage, pleural fluid, cerebrospinal fluid, ascetic fluid and joint fluid specimens) of tuberculosis suspected patients. M. tuberculosis DNA was extracted directly from different samples using two different protocols. Next, PCR was performed using three sets of specific primers to detect members of Mycobacterium genus, M. tuberculosis complex and non-tuberculosis Mycobacteria. The results were then compared with that of the culture method, which is considered as the gold standard method.

Results:

The concordance rate between the three sets of primers was calculated and IS6110/buffer PCR method showed good agreement with the LJ culture method (κ = 0.627, P < 0.0001). The sensitivity of IS6110/buffer PCR was 58.33%, with specificity of 77.78%; the positive and negative predictive values were 100% and 78.26%, respectively. Buffer method for DNA extraction was proved to give a higher accuracy to PCR in comparison with the boiling method.

Conclusions:

PCR method is a valuable, cost-effective and alternative tool for quick diagnosis of active tuberculosis in different clinical specimens.

The Study of DNA Methylation of bax Gene Promoter in Breast and Colorectal Carcinoma Cell Lines

BACKGROUND

The Bcl-2 protein family members have known as essential controllersof mitochondrial pathway of apoptosis. Bax has been implicated as potential tumor suppressor in certain solid tumors such as breast and colorectal carcinoma. DNA methylation of promoter associated CpG islands has known as a common mechanism for gene inactivation in tumor cells.

METHODS

The Methylation Specific PCR (MSP) has used to find the methylation profile of the bax gene promoter CpG islands in colorectal and breast cancer cell lines.

RESULTS

We have not detected any kind of "CpG islands hypermethylation" in promoter region of the bax gene in T47D, MCF7 (as ER positive), MDA-MB-231 and MDA-MB-468 (as ER negative) breast carcinoma-derived cell lines and colorectal cancer cell lines H29 and Caco II.

CONCLUSION

It seems that CpG island methylation could not play the main role in down-regulation of bax gene in breast and colon cancers.

Clonality of the immunoglobulin heavy chain genes in B cell non-hodgkin lymphoma using semi-nested PCR

BACKGROUND

Identification of gene rearrangements and clonality analysis are important techniques for the diagnosis of malignant lymphoproliferative diseases. These methods have various sensitivities based on the type of primer used and method of determination of polymerase chain reaction (PCR) products. This study aimed at determining the clonality of B cell non-Hodgkin lymphoma in Iranian patients using PCR method and 2 primers of FR2 and FR3.

MATERIALS AND METHODS

Paraffin embedded blocks of 67 patients with B cell lymphoma and 19 cases with lymphoid hyperplasia of the lymph nodes who presented to NRITLD, Masih Daneshvari Hospital were retrospectively reviewed. After extracting the genomic DNA using phenol and chloroform, clonal analysis was performed using semi-nested PCR by using two primers: FR2 and FR3. PCR products were determined using 2 techniques of heteroduplex analysis, polyacrylamide gel and silver staining and the conventional method of agarose gel and ethidium bromide staining. Appearance of 1 or 2 bands in the desired location were considered as a sign of clonality.

RESULTS

Monoclonal gene rearrangement was observed in 62 out of 67 patients (92.5%) as one or two discrete bands appeared within 60-120 base pairs (bp) and 200-300 bp range. Of the mentioned patients, 53 cases (79.1%) had FR2 and 51 (76.1%) had FR3 rearrangement. Heteroduplex analysis along with silver nitrate staining detected 3 out of the remaining 5 cases of lymphoma to be monoclonal. These cases had been reported negative by the conventional technique. In total, 65 out of 67 patients (97%) showed monoclonal gene rearrangement using both the abovementioned techniques. All hyperplasia cases were polyclonal by this method.

CONCLUSION

Our study showed that evaluation and detection of clonality using PCR, FR2 and FR3 primers along with heteroduplex analysis is a rapid sensitive technique for the diagnosis of malignant lymphomas.

Comparative Study of FISH, PCR and Cytogenetics on 25 Patients Submitted to Bone Marrow Transplantation (BMT) for Chronic Myelogenous Leukemia (CML); Which Tests can we Use in Routine Analysis Post BMT?

Chronic Myeloid Leukaemia (CML) shows an excellent response to allogeneic bone marrow transplantation (BMT) with a 60-80% long term disease free survival in recipients of unmanipulate marrow. The most frequent cause of treatment failure is leukaemic relapse, due to the re-emergence of malignant recipient clones. Clinical and haematological relapse is usually preceded by molecular evidence of relapse. Early detection of molecular relapse may allow intervention with immunotherapy such as donor lymphocyte infusions (DLI). This study was undertaken to compare results from two centres who employ either Fluorescent In Situ Hybridisation (FISH) or polymerase chain reaction (PCR) analysis of DNA polymorphisms as their routine method of detecting residual host cells following BMT for CML in order to establish (1) if these methods are equivalent for routine laboratory use in reporting of chimaerism results to the referring clinician, and (2) if these methods are beneficial for indicating new and early therapeutic strategies. FISH analyses for the X and Y chromosomes (in sex mismatched patients) and/or FISH for BCR and ABL loci were compared with short tandem repeat PCR (STR-PCR) and conventional karyotyping in serial analyses in 25 patients submitted to BMT for Philadelphia positive (Ph) CML. Comparison of all results on samples assessed between 1 and 13 years post BMT indicated that FISH and PCR, performed on the same bone marrow samples displayed similar results in more than 90% of patients in first 3 years after BMT which increased to a concordance rate of 100% in long term survivors. In contrast, comparison of FISH or PCR versus cytogenetic analysis indicated a low concordance rate, with less than 50% of samples showing similar results during all the follow-up period. Eighty percent of recipients (22 patients) had evidence of mixed chimaerism following BMT (initial level of positivity 1-6% recipient cells) during the follow-up period. This low percentage of recipient cells remained stable in 7 patients, while 9 patients reverted to a donor profile. All 16 patients are in haematological remission. In addition the 3 patients with complete donor chimaerism remain in remission. In the remaining 6 patients, a progressive increase in recipient cells occurred (progressive mixed chimaerism, PMC), and was followed by haematological relapse. We conclude that FISH and PCR can be used to monitor CML patients post BMT and transient or stable low level mixed chimaerism is not associated with leukaemia relapse, but PMC is predictive of imminent relapse and its detection may help to illucidate the timing of early intervention with donor lymphocyte infusion.