Characterization of Mycobacterium tuberculosis Central Asian Strain 1 using mycobacterial interspersed repetitive unit genotyping

The shortcut of mycobacterial interspersed repetitive unit-variable number tandem repeat typing for Mycobacterium tuberculosis differentiation

The 24-loci mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) genotyping has been used as an international standard method for Mycobacterium tuberculosis (Mtb) genotyping. However, different optimized VNTR loci sets for improving the discrimination of specific Mtb genotypes have been proposed. In this regard, we investigated the efficacy of accumulation of the percentage differences (APDs) compared with the least absolute shrinkage and selection operator (LASSO) regression strategy to identify a customized genotype-specific VNTR loci set which provides a resolution comparable to 24-loci MIRU-VNTR in divergent Mtb populations. We utilized Spoligotyping and 24-loci MIRU-VNTR typing for genotyping 306 Mtb isolates. The APD and LASSO regression approaches were used to identify a customized VNTR set in our studied isolates. Besides, the Hunter-Gaston discriminatory index (HGDI), sensitivity, and specificity of each selected loci set were calculated based on both strategies. The selected loci based on LASSO regression compared with APD-based loci showed a better discriminatory power for identifying all studied genotypes except for T genotype, which APD-based loci showed promising discriminative power. Our findings suggested the LASSO regression rather than the APD approach is more effective in the determination of possible discriminative VNTR loci set to precise discrimination of our studied Mtb population and may be beneficial to be used in finding reduced number loci sets in other Mtb genotypes or sublineages. Moreover, we proposed customized genotype-specific MIRU-VNTR loci sets based on the LASSO regression and APD approaches for precise Mtb strains identification. As the proposed VNTR sets offered a comparable discriminatory power to the standard 24 MIRU-VNTR loci set could be promising alternatives to the standard genotyping for using in resource-limited settings.

A Prospective Cohort Study on the Prevalent and Recurrent Tuberculosis Isolates Using the MIRU-VNTR Typing

The study aims to describe the clustering characteristics of Mycobacterium tuberculosis (M.tb) strains circulating in eastern China and determine the ratio of relapse and reinfection in recurrent patients. We recruited sputum smear-positive pulmonary tuberculosis cases from five cities of Jiangsu Province, China, during August 2013 and December 2015. Patients were followed for the treatment outcomes and recurrence based on a cohort design. M.tb strains were isolated and genotyped using the 12-locus MIRU-VNTR. The Beijing family was identified by the extended Region of Difference (RD) analysis. The Hunter-Gaston Discriminatory Index (HGDI) was used to judge the resolution ability of MIRU-VNTR. The odds ratio (OR) together with 95% confidence interval (CI) were used to estimate the strength of association. We performed a cluster analysis on 2098 M.tb isolates and classified them into 545 genotypes and five categories (I, 0.19%; II, 0.43%; III, 3.34%; IV, 77.46%; V, 18.59%). After adjusting for potential confounders, the Beijing family genotype (OR = 118.63, 95% CI: 79.61–176.79, P = 0.001) was significantly related to the dominant strain infections. Patients infected with non-dominant strains had a higher risk of the pulmonary cavity (OR = 1.39, 95% CI: 1.01–1.91, P = 0.046). Among 37 paired recurrent cases, 22 (59.46%) were determined as endogenous reactivation, and 15 (40.54%) were exogenous reinfection. The type of M.tb strains prevalent in Jiangsu Province is relatively single. Beijing family strains infection is dominant in local tuberculosis cases. Endogenous reactivation appears to be a major cause of recurrent tuberculosis in Eastern China. This finding emphasizes the importance of case follow-up and monitoring after the completion of antituberculosis treatment.

Genetic diversity of Mycobacterium tuberculosis Central Asian Strain isolates from Nepal and comparison with neighboring countries

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) is an emerging threat for successful tuberculosis control worldwide. Central Asian Strain (CAS) has been reported as one of the dominant families contributing to MDR-TB in South Asia including Nepal, India and Pakistan. The aim of this study was to better understand the genetic characteristics of MDR-TB CAS family isolates circulating in Nepal and compare the results with neighboring countries.

METHODS

A total of 145 MDR-TB CAS family isolates collected in Nepal from 2008 to 2013 were analyzed by spoligotyping and mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) analysis. In addition, we compared these data with published data from India and Pakistan to investigate a possible epidemiological link via construction of a minimum spanning tree (MST).

RESULTS

Spoligotyping analysis exhibited CAS1_Delhi SIT26 (n=60) as the predominant lineage among the MDR-TB CAS family in all three countries. However, the combined analysis with spoligotyping and MIRU-VNTR further discriminated 60 isolates into 49 different types and 5 clusters. Each cluster was composed of 14 isolates with a clustering rate of 23.3%, suggesting ongoing transmissions. Based on MST data from neighboring countries, we elucidated an evolutionary relationship between the two countries, Nepal and India, which could be explained by their open border.

CONCLUSION

This study identified the evolutionary relationships among MDR-TB CAS1_Delhi subfamily isolates from Nepal and those from neighboring countries.

Enhancing the differentiation of specific genotypes in Mycobacterium tuberculosis population

Today, significant attention is directed towards the global lineages and sublineages of Mycobacterium tuberculosis (Mtb). NEW-1 (SIT 127) and CAS1-Delhi (SIT 26) strains are recognized as growing and circulating Mtb genotypes, especially in Asian countries. It is crucial to develop or enhance Mtb genotyping methods for a more accurate and simple differentiation of these families. We used 24-loci mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing for genotyping 217 Mtb isolates. To select the optimal MIRU-VNTR loci, we calculated the Hunter-Gaston discriminatory index (HGDI), allelic diversity, and accumulation of percentage differences (APDs) between the strains among different groups of genotypes (NEW-1 and non-NEW-1; CAS1-Delhi and non-CAS). Finally, the minimum spanning tree was constructed for clustering analysis. In the NEW-1 population, loci with APD > 60% were found to have a high discriminatory power. VNTR loci with APD > 50% showed high discrimination power for the CAS population. Our findings suggest that APDs, which are valuable for the selection of VNTR loci sets, may improve the discriminatory power of MIRU-VNTR typing for identification of Mtb genotypes in specific regions.

Spoligotyping analysis of Mycobacterium tuberculosis in Khyber Pakhtunkhwa area, Pakistan

Background: Spoligotyping is a reproducible, reverse hybridization approach for genotyping of Mycobacterium tuberculosis complex (MTBC). Molecular typing of MTBC is helpful for understanding and controlling tuberculosis epidemics.

Methods: Spoligotyping was performed on 166 clinical isolates of Mycobacterium tuberculosis (MTB) collected from 25 districts of Khyber Pakhtunkhwa, Pakistan. Results were compared to SITVIT2, an online database developed by the Institut Pasteur de la Guadeloupe, France.

Results: Spoligotyping results showed that 145 strains (88%) displayed known patterns while 21 (12%) were new. Lineage 3/Central Asian strain (L3/CAS) was the predominant family (73%, χ²=19.9, P=0.001), followed by L2/Beijing (5.4%) and L4 (4.2%). L3/CAS1-Delhi was the major sublineage (82%) among the L3/CAS family (χ²=664, P=0.0001). Analysis showed that the majority of the clinical isolates with an unknown pattern had an evolutionary link with the L3/CAS strain, and nine (5.4%) of the unknown strains were epidemiologically linked and were tentatively named L3/CAS-KP (Khyber Pakhtunkhwa).

Conclusion: The present study demonstrated that L3/CAS is the predominant lineage of MTB, widely distributed in different areas of the Khyber Pakhtunkhwa province of Pakistan. Spoligotyping patterns of some clinical isolates could not be matched to other reported patterns in an international database. Other tools, such as mycobacterial interspersed repetitive unit–variable number tandem repeat (MIRU-VNTR), will be helpful in future investigations into the epidemiological characteristics of clinical isolates in the Khyber Pakhtunkhwa province.

Evaluation of the 15 and 24-loci MIRU-VNTR genotyping tools with spoligotyping in the identification of Mycobacterium tuberculosis strains and their genetic diversity in molecular epidemiology studies

BACKGROUND

The transmission dynamics of Mycobacterium tuberculosis (Mtb) using various genotyping tools has been studied globally and a particular tool for genotyping Mtb is the mycobacterial interspersed repetitive units-variable number tandem repeats (MIRU-VNTR). Tuberculosis (TB) remains an important public health problem worldwide and Sri Lanka being a country of tourist destination; because of major development projects undergoing, it has a high proportion of tourists and immigrants from Asia and Europe that are characterized with highest TB incidences and drug-resistant clinical isolates. Hence, in order to address the question of Mtb genetic diversity, we investigated the discriminatory power of both MIRU-VNTR typing of 15 and 24 loci with spoligotyping to differentiate Mtb isolates.

METHOD

Acid-fast bacilli positive sputum samples (n = 150) from first visit patients were collected. Decontamination of sputum and extraction of genomic DNA were carried out using standard techniques. The isolates were characterized by MIRU-VNTR for both the 15 and 24 loci and spoligotyping.

RESULTS

In our study population, MIRU-VNTR 15 and 24 loci did not show a significant difference among the identified M. tuberculosis strains. However, MIRU 24 loci yielded an additional strain LAM, which is of T1 origin. 15 loci strain grouping had more clusters of strains grouped together while 24 loci differentiated the same cluster of strains into distinct strain types.

CONCLUSION

We conclude that the use of 15-locus MIRU-VNTR typing is sufficient for a first-line epidemiological study to genotype M. tuberculosis, but the additional discriminatory power of 24 loci MIRU-VNTR has been able to differentiate samples within highly homologous groups.

Genetic diversity of Mycobacterium tuberculosis complex isolates circulating in an area with high tuberculosis incidence: Using 24-locus MIRU-VNTR method

We aimed to determine the genetic diversity, phylogenetic relationship and transmission dynamics of Mycobacterium tuberculosis complex (MTBC) genotypes in an area with high tuberculosis (TB) incidence. A set of 164 MTBC isolates from new TB patients of Golestan province, Iran, were subjected to genotyping using the standard 24-locus MIRU-VNTR method. Recent TB transmission was evaluated and phylogenetic relationships were analysed by minimum spanning tree and cluster-graph methods. Among the 164 isolates, 132 distinct patterns were detected. The 48 clustered isolates (29.3%) were distributed into 16 clusters ranging in size from 2 to 12 isolates. The most frequent genotype was Central Asian Strain/Delhi (CAS/Delhi) (n = 67, 40.8%), followed by NEW-1 (n = 53, 32.3%) and Beijing (n = 19, 11.6%) genotypes. Thirty five (72.9%) of NEW-1 isolates were recovered from immigrant patients and 84.2% (n = 16) of Beijing genotypes recovered from native cases. Statistically significant association was found between clustering and smoking (p = 0.047), drug addiction (p = 0.01) and prison history (p = 0.003). The estimated proportion of recent transmission was 19.5%. Presence of highly diverse MTBC isolates circulating in this province without a dominant genotype might be a consequence of importation of various genotypes in this area.

High diversity of multidrug-resistant Mycobacterium tuberculosis Central Asian Strain isolates in Nepal

OBJECTIVES

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) poses a major public health problem in Nepal. Although it has been reported as one of the dominant genotypes of MTB in Nepal, little information on the Central Asian Strain (CAS) family is available, especially isolates related to multidrug resistance (MDR) cases. This study aimed to elucidate the genetic and epidemiological characteristics of MDR CAS isolates in Nepal.

METHODS

A total of 145 MDR CAS isolates collected in Nepal from 2008 to 2013 were characterized by spoligotyping, mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) analysis, and drug resistance-associated gene sequencing.

RESULTS

Spoligotyping analysis showed CAS1_Delhi SIT26 as predominant (60/145, 41.4%). However, by combining spoligotyping and MIRU-VNTR typing, it was possible to successfully discriminate all 145 isolates into 116 different types including 18 clusters with 47 isolates (clustering rate 32.4%). About a half of these clustered isolates shared the same genetic and geographical characteristics with other isolates in each cluster, and some of them shared rare point mutations in rpoB that are thought to be associated with rifampicin resistance.

CONCLUSIONS

Although the data obtained show little evidence that large outbreaks of MDR-TB caused by the CAS family have occurred in Nepal, they strongly suggest several MDR-MTB transmission cases.

Genetic diversity and molecular epidemiology of multidrug-resistant Mycobacterium tuberculosis in Minas Gerais State, Brazil

Background

We aimed to characterize the genetic diversity of drug-resistant Mycobacterium tuberculosis (MTb) clinical isolates and investigate the molecular epidemiology of multidrug-resistant (MDR) tuberculosis from Minas Gerais State, Brazil.

Methods

One hundred and four MTb clinical isolates were assessed by IS6110-RFLP, 24-locus mycobacterial interspersed repetitive units variable-number tandem repeats (MIRU-VNTR), TB-SPRINT (simultaneous spoligotyping and rifampicin-isoniazid drug-resistance mutation analysis) and 3R-SNP-typing (analysis of single-nucleotide polymorphisms in the genes involved in replication, recombination and repair functions).

Results

Fifty-seven different IS6110-RFLP patterns were found, among which 50 had unique patterns and 17 were grouped into seven clusters. The discriminatory index (Hunter and Gaston, HGDI) for RFLP was 0.9937. Ninety-nine different MIRU-VNTR patterns were found, 95 of which had unique patterns and nine isolates were grouped into four clusters. The major allelic diversity index in the MIRU-VNTR loci ranged from 0.6568 to 0.7789. The global HGDI for MIRU-VNTR was 0.9991. Thirty-two different spoligotyping profiles were found: 16 unique patterns (n = 16) and 16 clustered profiles (n = 88). The HGDI for spoligotyping was 0.9009. The spoligotyped clinical isolates were phylogenetically classified into Latin-American Mediterranean (66.34 %), T (14.42 %), Haarlem (5.76 %), X (1.92 %), S (1.92 %) and U (unknown profile; 8.65 %). Among the U isolates, 77.8 % were classified further by 3R-SNP-typing as 44.5 % Haarlem and 33.3 % LAM, while the 22.2 % remaining were not classified. Among the 104 clinical isolates, 86 were identified by TB-SPRINT as MDR, 12 were resistant to rifampicin only, one was resistant to isoniazid only, three were susceptible to both drugs, and two were not successfully amplified by PCR. A total of 42, 28 and eight isolates had mutations in rpoB positions 531, 526 and 516, respectively. Correlating the cluster analysis with the patient data did not suggest recent transmission of MDR-TB.

Conclusions

Although our results do not suggest strong transmission of MDR-TB in Minas Gerais (using a classical 100 % MDR-TB identical isolates cluster definition), use of a smoother cluster definition (>85 % similarity) does not allow us to fully eliminate this possibility; hence, around 20–30 % of the isolates we analyzed might be MDR-TB transmission cases.

Multi-drug resistant Mycobacterium tuberculosis complex genetic diversity and clues on recent transmission in Punjab, Pakistan

Multi-Drug Resistant Tuberculosis (MDR-TB), i.e. bacilli resistant to rifampicin (RIF) and isoniazid (INH), is a major Public Health concern in Pakistan according to WHO estimates (3.5% and 32% of new and retreated cases, respectively). Previous Pakistanis reports identified a correlation between being MDR and belonging to Beijing or EAI lineages in one study, and belonging to "H4"-Ural Euro-American sublineage in another study. In addition, MDR-TB transmission was suspected in Karachi. We tested MDR characteristics on a Punjab sample of 278 clinical isolates (without selection for Multi-Drug Resistance) including new and retreated cases collected from 2008 to 2012. All samples were characterized by a new, microbead-based method named "TB-SPRINT" (molecular diagnostic including spoligotype identification, and genetic resistance determinants to first-line anti-TB drugs RIF and INH). Isolates from 2011 to 2012 (n=100) were further analyzed using 24-loci MIRU-VNTR. We detected 8.7% MDR isolates (CI95%=[5.0; 12.5]), mainly among CAS lineage that predominates in this central-East region of Pakistan. Out of 20 MDR-TB cases, 12 different TB-SPRINT profiles were identified, limiting the suspicion of MDR-TB transmission. 24 MIRU-VNTR confirmed the unrelatedness of isolates with different TB-SPRINT profiles and discriminated 3 isolates with identical TB-SPRINT profiles. In conclusion, our study did not confirm any of the correlations between Multi-Drug Resistance and lineage or sublineage in Punjab, Pakistan. MDR-TB isolates were diverse indicating that transmission is not pervasive. TB-SPRINT proved useful as a first step for detecting MDR-TB likely transmission events, before more extensive genotyping such as 15 or 24 MIRU-VNTR and thorough epidemiological investigation.

Mycobacterium tuberculosis Central Asian Strain (CAS) lineage strains in Pakistan reveal lower diversity of MIRU loci than other strains

Mycobacterium tuberculosis (MTB) Central Asian Strain (CAS) lineage strains are predominant in South Asia. Mycobacterial interspersed repetitive units-variable number of tandem repeats (MIRU-VNTR) typing is an effective way of determining genetic diversity of strains. A maximum of 24 loci-based MIRU-VNTR typing can be used, however, it is important to investigate the relevance of specific MIRU loci for regional strains for more cost-effective MIRU typing. MIRU-VNTR typing was performed on MTB strains from Pakistan. Strains were comprised of CAS (n=113) and non-CAS lineages (n=87) - both multi-drug resistant (MDR) and drug susceptible. Hunter Gaston Discriminatory Index (HGDI) for each MIRU loci was interpreted as poor, moderate or highly discriminatory. Results were analyzed using Bionumerics software and miru-vntrplus database link. Clustering analysis revealed 185 different MIRU types. Eight clusters of 2 strains each were present amongst MDR (3 clusters) and drug susceptible (5 clusters) isolates. MDR clusters had orphan and Haarlem strains, whereas drug susceptible strain clusters were comprised of CAS and Beijing lineage strains. The HGDI for 15 loci-based MIRU typing of all isolates was 0.620, whereas HGDI for CAS was lower than non-CAS lineage strains (p-value: 0.023). HGDI of 8 MIRU-VNTR loci (Qub 26b, 10, 26, 4156, Mtub 04, 16, 31 and ETR-A) were all highly discriminatory. The average HGDI based on these 8 loci was significantly lower for CAS than non-CAS strains (P value: 0.03). The lower discriminatory index for CAS using both 15 and 8 MIRU loci-based analysis suggests less genetic diversity in these isolates than in other lineages. The eight highly discriminatory MIRU loci for CAS may help in monitoring the transmission of MTB strains in regions with high CAS lineage prevalence.

Molecular epidemiology and genotyping of Mycobacterium tuberculosis isolated in Baghdad

Tuberculosis (TB) remains a major health problem in Iraq but the strains responsible for the epidemic have been poorly characterized. Our aim was to characterize the TB strains circulating in Bagdad (Iraq). A total of 270 Mycobacterium tuberculosis complex (MTBC) strains isolated between 2010 and 2011 from TB patients attending the Center of Chest and Respiratory diseases in Baghdad were analyzed by Spoligotyping. The analysis indicated that 94.1% of the isolates belong to known genotype clades: CAS 39.6%, ill-defined T clade 29.6%, Manu 7.4%, Haarlem 7%, Ural 4.1%, LAM 3.3%, X 0.7%, LAM7-TUR 0.7%, EAI 0.7%, S 0.7%, and unknown 5.9%. Comparison with the international multimarker database SITVIT2 showed that SIT 309 (CAS1-Delhi) and SIT1144 (T1) were the most common types. In addition, 44 strains were included in SITVIT2 database under 16 new Spoligotype International Types (SITs); of these, 6 SITs (SIT3346, SIT3497, SIT3708, SIT3790, SIT3791, and SIT3800) (n = 32 strains) were created within the present study and 10 were created after a match with an orphan in the database. By using 24-loci MIRU-VNTR-typing on a subset of 110 samples we found a high recent transmission index (RTI) of 33.6%. In conclusion, we present the first unifying framework for both epidemiology and evolutionary analysis of M. tuberculosis in Iraq.

Mycobacterium tuberculosis belonging to family LAM and sublineage RD(Rio): common strains in Southern Brazil for over 10 years

A sublineage of Mycobacterium tuberculosis called RD(Rio) was described in 2007. Although only recently described, this strain may have been present previously in the population, and its identification in clinical isolates will elucidate bacterial transmission dynamics and host-pathogen interactions. This study evaluated the clonal diversity of the RD(Rio) sublineage in clinical isolates from Rio Grande-RS obtained between 1998 and 2001. Among the 45 samples analyzed by the MIRU-VNTR method, there were six clusters with two samples each and 33 orphan strains with unique pattern. The strains were distributed across several different lineages including LAM (34.04%), × (14.89%), Haarlem (12.77%), UgandaI (10.64%), S (4.26%), NEW-1 (2.13%) and Cameroon (2.13%); 14.89% of the strains matched to multiple lineages. RD(Rio) strains were present in 28.9% of the samples and 81.25% of the identified strains belonged to the LAM family. The high clonal diversity observed in this study is a constant feature in this region. The RD(Rio) sublineage has been in Rio Grande-RS since 1998. The continued monitoring of RD(Rio) in clinical isolates will enhance the understanding of its epidemiological significance.

MIRU-VNTR profiles of three major Mycobacterium tuberculosis spoligotypes found in western India

We performed 12 loci MIRU-VNTR on 327 Mycobacterium tuberculosis (Mtb) isolates belonging to three major spoligotypes MANU1, CAS1_Delhi and Beijing from Mumbai, western India and two proximal rural locations. Complete allele and drug susceptibility data was available for 232 isolates. These included 143 MANU1 (ST100), 65 CAS1_Delhi (ST26) and 24 Beijing (ST1) isolates. Of the 232 isolates, 26 were rural consisting 6 CAS1_Delhi and 20 MANU1 isolates. Using eBURST multi-locus sequence typing (MLST), cluster analyses was performed for each of the spoligotypes and drug susceptibility profiles. MANU1 MLST consisted of 90 related isolates (clustered and grouped) and 53 singletons; CAS1_Delhi MLST consisted of 44 related isolates and 21 singletons; Beijing MLST consisted of 10 related isolates and 14 singletons. Although the number of related isolates were different in MANU1 (63%), CAS1_Delhi (68%) and Beijing (42%) clusters, it was not statistically significant. Furthermore, it was observed that while MANU1 and CAS1_Delhi singletons (n = 74) had only 12 (16%) MDR isolates, the Beijing MLST had 8/14 (57%) MDR singleton isolates. Phylogenetic ananlysis using minimum spanning tree (MST) and a UPGMA radial tree revealed MANU1 had the largest number of nodes as compared to the CAS1_Delhi and Beijing spoligotypes. Additionally the CAS isolates were more homogeneous than the MANU1 isolates. The 12 loci MIRU-VNTR was used to provide greater discrimination than spoligotyping, but 6 of the 12 loci provided less than 50% discriminatory power. The highest discrimination was achieved using locus 26 (80%). Our results concur with recent reports that the most discriminatory MIRU-VNTR combination varied across different lineages. The results also highlight the need for more robust genetic markers for studying the transmission of Mtb in endemic regions like India.

Molecular epidemiology of Mycobacterium tuberculosis clinical isolates in Southwest Ireland

Tuberculosis has had significant effects on Ireland over the past two centuries, causing persistently higher morbidity and mortality than in neighbouring countries until the last decade. This study describes the results of genotyping and drug susceptibility testing of 171 strains of Mycobacterium tuberculosis complex isolated between January 2004 and December 2006 in a region of Ireland centred on the city of Cork. Spoligotype comparisons were made with the SpolDB4 database and clustered 130 strains in 23 groups, forty-one strains showed unique Spoligotyping patterns. The commonest spoligotypes detected were ST0137 (X2) (16.9%), and ST0351 (15.8%) ('U' clade). The major spoligotype clades were X (26.2%), U (19.3%), T (15.2%), Beijing (5.9%), Haarlem (4.7%), LAM (4.1%), BOVIS (1.75%), with 12.9% unassigned strains. A 24-locus VNTR genotyping produced 15 clusters containing 49 isolates, with high discrimination index (HGDI>0.99). A combination of Spoligotyping and VNTR reduced the number of clustered isolates to 47 in 15 clusters (27.5%). This study identified ST351 as common among Irish nationals, and found a low rate of drug resistance with little evidence of transmission of drug resistant strains. Strain clustering was significantly associated with age under 55 years and Irish nationality. Only strains of Euro-American lineage formed clusters. Molecular typing did not completely coincide with the results of contact investigations.