Tuberculosis outbreak in Eastern Norway

BACKGROUND

Tuberculosis is a rare disease in Norway, especially among those who are born here. Contact tracing for cases of pulmonary tuberculosis is essential to find others who are ill or infected, and to prevent further infection. This article describes the investigation of an outbreak in which many of those infected or ill were Norwegian adolescents.

MATERIAL AND METHOD

Nine persons directly or indirectly associated with the same educational institution were diagnosed with tuberculosis in 2013. Genetic testing of tuberculosis bacteria linked a further 13 cases of the disease reported in Eastern Norway during the period 2009-2013 to the outbreak. Information from the Norwegian Surveillance System for Communicable Diseases (MSIS) was used to investigate the outbreak, and information was also retrieved on exposure and contact networks.

RESULTS

The first patient at the educational institution had long-term symptoms before diagnosis. Contact tracing for this case included 319 persons, of whom eight were ill, 49 infected and 37 received preventive therapy. The extent of contract tracing for the remaining 21 cases varied and included a total of 313 persons, of whom two were found to be ill (included in the 21 cases), 30 were infected and 12 received preventive therapy.

INTERPRETATION

Delayed diagnosis led to an unusually large tuberculosis outbreak in a Norwegian context. The extent of contact tracing varied with no obvious relation to the infectiousness of the index patient. The outbreak demonstrates the importance of continued vigilance with regard to tuberculosis as a differential diagnosis, also among patients born in Norway.

Description of the largest cluster of tuberculosis notified in Norway 1997-2011: is the Norwegian tuberculosis control programme serving its purpose for high risk groups?

Background

Approximately 90% of new tuberculosis (TB) cases notified in Norway are asylum seekers and other immigrants from high-incidence countries. Asylum seekers are screened upon arrival at the National Immigration Centre. Other immigrants receive a letter from the Municipal Health Services requesting that they present for screening in their municipality of residence. In order to identify potential areas where the TB control programme could be better adapted for these groups, we studied the largest cluster of TB cases (“cluster X”) notified in Norway until 2011.

Methods

Cases were defined as TB notifications reported to MSIS between January 1997 and December 2011 with identical IS6110 RFLP assigned to cluster X. We described the cases in cluster X by using data from the Norwegian Surveillance System for Communicable Diseases (MSIS). Missing or incomplete information in MSIS was obtained from the National Reception Centre, Oslo University Hospital and Municipal Health services.

Results

Of a total of 44 individuals meeting the case definition, 36 originated from Somalia and eight from other high-incidence countries. Twenty nine were asylum seekers and 15 were other immigrants. Upon arrival, 18/44 had been diagnosed with latent TB infection (LTBI), 9/44 tested negative for LTBI and 4/44 had been diagnosed with active TB. Results of TB-screening upon arrival were not available for the remaining 13/44 (one asylum seeker and 12 other immigrants). Five of the 12 other immigrants had still not been screened for TB after staying one year or longer in Norway.

Conclusions

Most cases in cluster X with available results of TB-screening were already infected at arrival, indicating that their disease could be due to endogenous reactivation, rather than recent transmission after arrival to Norway. TB-status upon arrival was unknown for many of the other immigrants due to lack of initial screening. The reasons why conduction of the initial screening among other immigrants is failing should be explored and methods to simplify the TB screening at arrival should be implemented.

Evolution of extensively drug-resistant Mycobacterium tuberculosis from a susceptible ancestor in a single patient

Background

Mycobacterium tuberculosis is characterized by a low mutation rate and a lack of genetic recombination. Yet, the rise of extensively resistant strains paints a picture of a microbe with an impressive adaptive potential. Here we describe the first documented case of extensively drug-resistant tuberculosis evolved from a susceptible ancestor within a single patient.

Results

Genome sequences of nine serial M. tuberculosis isolates from the same patient uncovered a dramatic turnover of competing lineages driven by the emergence, and subsequent fixation or loss of single nucleotide polymorphisms. For most drugs, resistance arose through independent emergence of mutations in more than one clone, of which only one ultimately prevailed as the clone carrying it expanded, displacing the other clones in the process. The vast majority of mutations identified over 3.5 years were either involved in drug resistance or hitchhiking in the genetic background of these. Additionally, RNA-sequencing of isolates grown in the absence of drug challenge revealed that the efflux-associated iniBAC operon was up-regulated over time, whereas down-regulated genes include those involved in mycolic acid synthesis.

Conclusions

We observed both rapid acquisitions of resistance to antimicrobial compounds mediated by individual mutations as well as a gradual increase in fitness in the presence of antibiotics, likely driven by stable gene expression reprogramming. The rapid turnover of resistance mutations and hitchhiking neutral mutations has major implications for inferring tuberculosis transmission events in situations where drug resistance evolves within transmission chains.

Electronic supplementary material

The online version of this article (doi:10.1186/s13059-014-0490-3) contains supplementary material, which is available to authorized users.

Phenotypic and genomic characterization of pneumococcus-like streptococci isolated from HIV-seropositive patients

Accurate differentiation between pneumococci and other viridans streptococci is essential given their differences in clinical significance. However, classical phenotypic tests are often inconclusive, and many examples of atypical reactions have been reported. In this study, we applied various phenotypic and genotypic methods to discriminate between a collection of 12 streptococci isolated from the upper respiratory tract of HIV-seropositive individuals in 1998 and 1999. Conventional phenotypic characterization initially classified these streptococci as Streptococcus pneumoniae, as they were all sensitive to optochin and were all bile soluble. However, they did not agglutinate with anti-pneumococcal capsular antibodies and were also far more resistant to antimicrobial agents than typeable pneumococci isolated in the same period. Genotypic characterization of these isolates and control isolates by both multilocus sequence analysis (MLSA) and comparative genomic hybridization (CGH) showed that only a single isolate was genetically considered to be a true S. pneumoniae isolate, and that the remaining 11 non-typable isolates were indeed distinct from true pneumococci. Of these, 10 most closely resembled a subgroup of Streptococcus mitis isolates genetically, while one strain was identified as a Streptococcus pseudopneumoniae isolate. CGH also showed that a considerable part of the proposed pneumococcal core genome, including many of the known pneumococcal virulence factors, was conserved in the non-typable isolates. Sequencing of part of the 16S rRNA gene and investigation for the presence of ply by PCR corroborated these results. In conclusion, our findings confirm the close relationship between streptococci of the Mitis group, and show that both MLSA and CGH enable pneumococci to be distinguished from other Mitis group streptococci.

Molecular epidemiology and drug resistance of widespread genotypes of Mycobacterium tuberculosis in northwestern Russia

SETTING

Four administrative territories (Archangel Oblast, Murmansk Oblast, Republic of Karelia, Republic of Komi) in the northwestern federal region of Russia.

OBJECTIVE

To describe the genetic diversity and level of drug resistance in Mycobacterium tuberculosis isolates from new cases of pulmonary tuberculosis.

DESIGN

A total of 176 isolates of M. tuberculosis were tested for drug susceptibility and typed with insertion sequence (IS) 6110 restriction fragment length polymorphism (RFLP) and spoligotyping.

RESULTS

The Beijing family was found to be the most prevalent (47.1%), most frequently clustered and significantly associated with drug resistance to all first-line anti-tuberculosis drugs (isoniazid, rifampicin, ethambutol, streptomycin and pyrazinamide) and ethionamide, when compared to the T and Haarlem families of M. tuberculosis, which were also prevalent in the study population. Some RFLP clusters (4/10) included isolates that originated from patients residing in different territories, and cases infected with multiple strains of M. tuberculosis were apparently present in the collection.

CONCLUSION

The M. tuberculosis population in northwestern Russia appears to be genetically diverse and geographically widespread. Although dominated by isolates assigned to the Beijing family, other families also contribute to the current epidemic, and multiple strain infections may represent a problem in many cases. Extended genetic studies should be encouraged.

[Drug resistance in tuberculosis]

BACKGROUND

The emergence of drug-resistant tuberculosis is one of the main challenges in the global combat against tuberculosis. The objective of the article is to discuss the main causes for emergence of drug resistance, describe the epidemiology of drug-resistant tuberculosis with focus on the situation in Norway and advise on how this should be managed.

MATERIAL AND METHOD

This review is based on relevant published literature, data from surveillance of the disease in Norway and current national and international recommendations for prevention and control of tuberculosis.

RESULTS

Tuberculosis can normally be treated effectively with a standardized combination of drugs for six months. The long duration of treatment is a challenge and incorrect treatment causes development of resistant tuberculosis. The objectives of tuberculosis treatment are to cure the patient, to stop transmission of the bacteria and prevent emergence of drug resistance. The total number of patients diagnosed with multidrug resistant tuberculosis (MDR)-TB in Norway is low, although a threefold increase has occurred in the last decade compared to in previous decades. Most patients were born abroad. Treatment of MDR-TB takes up to two years, is costly and has more side effects. Treatment of MDR-TB is associated with lower cure rate and higher fatality; although in Norway most cases are cured.

DISCUSSION

The global situation also affects Norway. Early diagnosis of infectious cases and close monitoring of patients under treatment, by direct observation of medication, can prevent new cases of MDR-TB.

School based screening for tuberculosis infection in Norway: comparison of positive tuberculin skin test with interferon-gamma release assay

Background

In Norway, screening for tuberculosis infection by tuberculin skin test (TST) has been offered for several decades to all children in 9th grade of school, prior to BCG-vaccination. The incidence of tuberculosis in Norway is low and infection with M. tuberculosis is considered rare. QuantiFERON^®TB Gold (QFT) is a new and specific blood test for tuberculosis infection. So far, there have been few reports of QFT used in screening of predominantly unexposed, healthy, TST-positive children, including first and second generation immigrants. In order to evaluate the current TST screening and BCG-vaccination programme we aimed to (1) measure the prevalence of QFT positivity among TST positive children identified in the school based screening, and (2) measure the association between demographic and clinical risk factors for tuberculosis infection and QFT positivity.

Methods

This cross-sectional multi-centre study was conducted during the school year 2005–6 and the TST positive children were recruited from seven public hospitals covering rural and urban areas in Norway. Participation included a QFT test and a questionnaire regarding demographic and clinical risk factors for latent infection. All positive QFT results were confirmed by re-analysis of the same plasma sample. If the confirmatory test was negative the result was reported as non-conclusive and the participant was offered a new test.

Results

Among 511 TST positive children only 9% (44) had a confirmed positive QFT result. QFT positivity was associated with larger TST induration, origin outside Western countries and known exposure to tuberculosis. Most children (79%) had TST reactions in the range of 6–14 mm; 5% of these were QFT positive. Discrepant results between the tests were common even for TST reactions above 15 mm, as only 22 % had a positive QFT.

Conclusion

The results support the assumption that factors other than tuberculosis infection are widely contributing to positive TST results in this group and indicate the improved specificity of QFT for latent tuberculosis. Our study suggests a very low prevalence of latent tuberculosis infection among 9th grade school children in Norway. The result will inform the discussion in Norway of the usefulness of the current TST screening and BCG-policy.

Screening for tuberculosis infection among newly arrived asylum seekers: comparison of QuantiFERONTB Gold with tuberculin skin test

Background

QuantiFERON^®TB Gold (QFT) is a promising blood test for tuberculosis infection but with few data so far from immigrant screening. The aim of this study was to compare results of QFT and tuberculin skin test (TST) among newly arrived asylum seekers in Norway and to assess the role of QFT in routine diagnostic screening for latent tuberculosis infection.

Methods

The 1000 asylum seekers (age ≥ 18 years) enrolled in the study were voluntarily recruited from 2813 consecutive asylum seekers arriving at the national reception centre from September 2005 to June 2006. Participation included a QFT test and a questionnaire in addition to the mandatory TST and chest X-ray.

Results

Among 912 asylum seekers with valid test results, 29% (264) had a positive QFT test whereas 50% (460) tested positive with TST (indurations ≥ 6 mm), indicating a high proportion of latent infection within this group. Among the TST positive participants 50% were QFT negative, whereas 7% of the TST negative participants were QFT positive. There was a significant association between increase in size of TST result and the likelihood of being QFT positive. Agreement between the tests was 71–79% depending on the chosen TST cut-off and it was higher for non-vaccinated individuals.

Conclusion

By using QFT in routine screening, further follow-up could be avoided in 43% of the asylum seekers who would have been referred if based only on a positive TST (≥ 6 mm). The proportion of individuals referred will be the same whether QFT replaces TST or is used as a supplement to confirm a positive TST, but the number tested will vary greatly. All three screening approaches would identify the same proportion (88–89%) of asylum seekers with a positive QFT and/or a TST ≥ 15 mm, but different groups will be missed.

Impact of immigration on the molecular epidemiology of Mycobacterium tuberculosis in a low-incidence country

RATIONALE

Programs to prevent the incidence rate of tuberculosis (TB) from increasing in many low-incidence countries are challenged by international travel and immigration from high-burden countries.

OBJECTIVES

The current study aimed to determine the effect of such immigration on the genetic diversity of Mycobacterium tuberculosis isolates in an entire nation's population during 1994-2005.

METHODS

A total of 3,131 patients were notified with TB during the 12-year period. Of these, 2,284 (73%) had TB verified by culture, and isolates from 2,173 (96%) of these were analyzed by IS6110 restriction fragment length polymorphism.

MEASUREMENTS AND MAIN RESULTS

Only 31% of the included strains were isolated from nonimmigrants, the remaining 69% were isolated from immigrants. Although the incidence increased throughout the period, the genetic diversity remained high. A total of 135 clusters were identified; the percentage of recent disease was reduced among nonimmigrants, and remained stable among the immigrants during the study period. Although 69% of the isolates originated from immigrants from high-incidence countries, the established TB control program in the receiving country was adequate for the prevention of disease transmission. On average per year, only 2 nonimmigrants and 13 immigrants developed disease as a result of infection within the country by imported M. tuberculosis.

CONCLUSIONS

Twelve years of M. tuberculosis importation as a result of immigration from high-incidence countries had little influence on the transmission of this pathogen in the receiving low-incidence country. To prevent future increase of transmission of TB, the current control strategies of low-incidence countries are adequate but must be maintained.

Drug resistance of Mycobacterium tuberculosis in the Sunamganj District of Bangladesh

Spread of drug-resistant tuberculosis (TB) threatens TB-control programmes, and all countries need to monitor the patterns and trends of anti-TB drug resistance. Such data assess the quality of control programmes and help forecast future trends of drug resistance. It will also help to establish guidelines for TB therapy. The aim of the current study was to describe the rate of drug-resistant Mycobacterium tuberculosis in the Sunamganj District of Bangladesh. Bacterial isolates were collected from sputum smear positive (ss+) patients who attended the National TB Programme from November 2003 to December 2004. A total of 95 isolates was tested for susceptibility to streptomycin (SM), isoniazid (INH), rifampicin (RMP) and ethambutol (EMB) at the National Reference Laboratory for Mycobacteria at the Norwegian Institute of Public Health (NIPH), Oslo. The total resistance among new cases to any drug was 31%. For SM it was 18%, INH 23%, RMP 2%, EMB 10% and 2% were multidrug-resistant (MDR). The National Tuberculosis Programme (NTP) in Sunamganj is still effective, although the high resistance to INH is alarming. An increased risk of treatment failure has been demonstrated in areas with high levels of INH resistance, and a high proportion of INH resistant cases may develop resistance to RMP during treatment.

Candidemia in Norway (1991 to 2003): results from a nationwide study

A long-term, nationwide prospective candidemia study has been ongoing in Norway since 1991. All medical microbiological laboratories in the country have participated. During the period 1991 to 2003 a total of 1,393 episodes of candidemia occurred in 1,348 patients. The incidence of candidemia episodes per 100,000 inhabitants increased from approximately 2 episodes in the early 1990s to 3 episodes in 2001 to 2003. The average annual incidences varied markedly between the age groups. The incidence was high in patients aged < 1 year and in patients aged > or = 70 years. In patients > or = 80 years of age, the incidence has increased during the last 3 years from an annual average of 6.5 to 15.6 cases/100,000 inhabitants in 2003. Four Candida species (C. albicans [70%], C. glabrata [13%], C. tropicalis [7%], and C. parapsilosis [6%]) accounted for 95.5% of the isolates. The species distribution has been constant during the 13-year study period. The distribution of the most important species varied with the age of the patient. In patients < 1 year of age, the majority of episodes were caused by C. albicans (91%). The occurrence of C. glabrata increased with age. In patients > or = 80 years of age, approximately 1/3 of all episodes were due to this species. All C. albicans strains were susceptible to fluconazole. The percentage of yeast isolates with decreased susceptibility to fluconazole (MICs > or = 16 microg/ml) was 10.7% during the first period of this study (1991 to 1996) and 11.7% during the second period (1997 to 2003).

[Creatinine and calcium in urine and blood after brief exposure to magnetic fields]

In this experimental study, 35 males were exposed to artificial magnetic fields. The fields were produced by a set of Helmholz coils internally isolated by a Faraday cage which effectively eliminated electrical fields. Each participant stayed inside the coils for 40 minutes on two occasions with an interval of seven days, but was actually only once exposed to a static magnetic field (9.6 mT) and oscillating magnetic fields of variable frequency and strength. Urine and blood samples were taken before and after exposure, and before and after non-exposure. Analysis detected significant changes in serum creatinine level after exposure (p < 0.0001). The changes in serum creatinine level in the nonexposed situation were significantly smaller than the changes found in the exposed situation (p < 0.0001). The changes i urine creatinine after 40 minutes of exposure was also found to be significant (p < 0.01). Exposure to magnetic fields may induce biological reactions.