Tuberculosis transmission in the 1990s

Association Between Cytomegalovirus Infection and Tuberculosis Disease: A Systematic Review and Meta-Analysis of Epidemiological Studies

BACKGROUND

Tuberculosis is one of the leading causes of mortality worldwide from an infectious disease. This review aimed to investigate the association between prior cytomegalovirus infection and tuberculosis disease.

METHODS

Six bibliographic databases were searched from their respective inception to 31 December 2021. Data were pooled using random-effects meta-analysis.

RESULTS

Of 5476 identified articles, 15 satisfied the inclusion criteria with a total sample size of 38 618 patients. Pooled findings showed that individuals with cytomegalovirus infection had a higher risk of tuberculosis disease compared to those not infected with cytomegalovirus (odds ratio [OR], 3.20; 95% confidence interval [CI], 2.18-4.70). Age was the only covariate that exerted a significant effect on the result of the association. Meta-analysis of risk estimates reported in individual studies showed a marked and significant correlation of cytomegalovirus infection with active tuberculosis (adjusted hazard ratio, 2.92; 95% CI, 1.34-4.51; adjusted OR, 1.14; 95% CI, .71-1.57). A clear dose-response relation was inferred between the levels of cytomegalovirus antibodies and the risks of tuberculosis events (OR for high levels of cytomegalovirus antibodies, 4.07; OR for medium levels of cytomegalovirus antibodies, 3.58).

CONCLUSIONS

The results suggest an elevated risk of tuberculosis disease among individuals with a prior cytomegalovirus infection.

Importance of cough and M. tuberculosis strain type as risks for increased transmission within households

RATIONALE

The degree to which tuberculosis (TB) is transmitted between persons is variable. Identifying the factors that contribute to transmission could provide new opportunities for TB control. Transmission is influenced by host, bacterial and environmental factors. However, distinguishing their individual effects is problematic because measures of disease severity are tightly correlated, and assessing the virulence of Mycobacterium tuberculosis isolates is complicated by epidemiological and clinical confounders.

OBJECTIVES

To overcome these problems, we investigated factors potentially associated with TB transmission within households.

METHODS

We evaluated patients with smear-positive (≥2+), pulmonary TB and classified M. tuberculosis strains into single nucleotide polymorphism genetic cluster groups (SCG). We recorded index case, household contact, and environmental characteristics and tested contacts with tuberculin skin test (TST) and interferon-gamma release assay. Households were classified as high (≥70% of contacts with TST≥10 mm) and low (≤40%) transmission. We used logistic regression to determine independent predictors.

RESULT

From March 2008 to June 2012, we screened 293 TB patients to enroll 124 index cases and their 731 contacts. There were 23 low and 73 high transmission households. Index case factors associated with high transmission were severity of cough as measured by a visual analog cough scale (VACS) and the Leicester Cough Questionnaire (LCQ), and cavitation on chest radiograph. SCG 3b strains tended to be more prevalent in low (27.3%) than in high (12.5%) transmission households (p = 0.11). In adjusted models, only VACS (p<0.001) remained significant. SCG was associated with bilateral disease on chest radiograph (p = 0.002) and marginally associated with LCQ sores (p = 0.058), with group 3b patients having weaker cough.

CONCLUSIONS

We found differential transmission among otherwise clinically similar patients with advanced TB disease. We propose that distinct strains may cause differing patterns of cough strength and cavitation in the host leading to diverging infectiousness. Larger studies are needed to verify this hypothesis.

Cough aerosols of Mycobacterium tuberculosis predict new infection: a household contact study

RATIONALE

Airborne transmission of Mycobacterium tuberculosis results from incompletely characterized host, bacterial, and environmental factors. Sputum smear microscopy is associated with considerable variability in transmission.

OBJECTIVES

To evaluate the use of cough-generated aerosols of M. tuberculosis to predict recent transmission.

METHODS

Patients with pulmonary tuberculosis (TB) underwent a standard evaluation and collection of cough aerosol cultures of M. tuberculosis. We assessed household contacts for new M. tuberculosis infection. We used multivariable logistic regression analysis with cluster adjustment to analyze predictors of new infection.

MEASUREMENTS AND MAIN RESULTS

From May 2009 to January 2011, we enrolled 96 sputum culture-positive index TB cases and their 442 contacts. Only 43 (45%) patients with TB yielded M. tuberculosis in aerosols. Contacts of patients with TB who produced high aerosols (≥10 CFU) were more likely to have a new infection compared with contacts from low-aerosol (1-9 CFU) and aerosol-negative cases (69%, 25%, and 30%, respectively; P = 0.009). A high-aerosol patient with TB was the only predictor of new M. tuberculosis infection in unadjusted (odds ratio, 5.18; 95% confidence interval, 1.52-17.61) and adjusted analyses (odds ratio, 4.81; 95% confidence interval, 1.20-19.23). Contacts of patients with TB with no aerosols versus low and high aerosols had differential tuberculin skin test and interferon-γ release assay responses.

CONCLUSIONS

Cough aerosols of M. tuberculosis are produced by a minority of patients with TB but predict transmission better than sputum smear microscopy or culture. Cough aerosols may help identify the most infectious patients with TB and thus improve the cost-effectiveness of TB control programs.

Variability of infectious aerosols produced during coughing by patients with pulmonary tuberculosis

RATIONALE

Mycobacterium tuberculosis is transmitted by infectious aerosols, but assessing infectiousness currently relies on sputum microscopy that does not accurately predict the variability in transmission.

OBJECTIVES

To evaluate the feasibility of collecting cough aerosols and the risk factors for infectious aerosol production from patients with pulmonary tuberculosis (TB) in a resource-limited setting.

METHODS

We enrolled subjects with suspected TB in Kampala, Uganda and collected clinical, radiographic, and microbiological data in addition to cough aerosol cultures. A subset of 38 subjects was studied on 2 or 3 consecutive days to assess reproducibility.

MEASUREMENTS AND MAIN RESULTS

M. tuberculosis was cultured from cough aerosols of 28 of 101 (27.7%; 95% confidence interval [CI], 19.9-37.1%) subjects with culture-confirmed TB, with a median 16 aerosol cfu (range, 1-701) in 10 minutes of coughing. Nearly all (96.4%) cultivable particles were 0.65 to 4.7 μm in size. Positive aerosol cultures were associated with higher Karnofsky performance scores (P = 0.016), higher sputum acid-fast bacilli smear microscopy grades (P = 0.007), lower days to positive in liquid culture (P = 0.004), stronger cough (P = 0.016), and fewer days on TB treatment (P = 0.047). In multivariable analyses, cough aerosol cultures were associated with a salivary/mucosalivary (compared with purulent/mucopurulent) appearance of sputum (odds ratio, 4.42; 95% CI, 1.23-21.43) and low days to positive (per 1-d decrease; odds ratio, 1.17; 95% CI, 1.07-1.33). The within-test (kappa, 0.81; 95% CI, 0.68-0.94) and interday test (kappa, 0.62; 95% CI, 0.43-0.82) reproducibility were high.

CONCLUSIONS

A minority of patients with TB (28%) produced culturable cough aerosols. Collection of cough aerosol cultures is feasible and reproducible in a resource-limited setting.

Drug resistance among Mycobacterium tuberculosis strains in immigrants: is there a real threat everywhere?

A study was performed to determine the impact of drug resistance in tuberculosis among immigrant patients in Madrid, Spain. During the period 1995-2001, the relative proportion of isolates from immigrant patients increased from 4.4% to 24.2%. No differences between immigrants and Spanish-born patients were detected for resistance to any first-line anti-tuberculous drug. More studies are required to determine the actual incidence of resistant tuberculosis in immigrants.

Cough-generated aerosols of Mycobacterium tuberculosis: a new method to study infectiousness

The concentration and size distribution of infectious aerosols produced by patients with pulmonary tuberculosis (TB) has never been directly measured. We aimed to assess the feasibility of a method that we developed to collect and quantify culturable cough-generated aerosols of Mycobacterium tuberculosis. Subjects were recruited from a referral hospital and most had multidrug-resistant TB. They coughed into a chamber containing microbial air samplers while cough frequency was measured during two 5-minute sessions. Cough-generated aerosol cultures were positive in 4 of 16 subjects (25%) with smear-positive pulmonary TB. There was a rapid decrease in the cough-generated aerosol cultures within the first 3 weeks of effective treatment. Culture-positive cough aerosols were associated with lack of treatment during the previous week (p = 0.007), and there was a trend in the association with cough frequency (p = 0.08). The size distributions of these aerosols were variable, but most particle sizes were in the respirable range. Quantification of viable cough-generated aerosols is feasible and offers a new approach to study infectiousness and transmission of M. tuberculosis and other airborne pathogens.

[Recent transmission of tuberculosis in an area with low incidence: epidemiological and molecular study]

BACKGROUND

Few reports have analysed the transmission of tuberculosis in rural areas with a low incidence of disease.

PATIENTS AND METHOD

A population-based molecular epidemiological study of patients with tuberculosis, diagnosed by culture, was conducted in Segovia (Spain) between 1995 and 1999. Clinical, demographic and epidemiological data were reviewed. Patients whose clinical isolates of Mycobacterium tuberculosis had identical restriction-fragment-length-polymorphism (RFLP) patterns with IS6110 and spoligotyping were included in clusters.

RESULTS

Of 96 patients with positive-culture for M. tuberculosis complex, 6 were considered as false-positive results. The mean incidence rate was 12.3 cases/100,000 inhabitants. Median age was 50.3 (SD: 23.1), 14% was HIV-infected, and 92% of them were living in urban areas (p < 0.01). There were no cases of primary resistance to isoniazid. DNA fingerprint was performed in 87 samples. We identified 8 clusters including 24 patients (27.7%). Clusters had between 2 and 6 cases. Patients aged < 35 years (OR = 3.1; CI 95%, 1.0-9.6) and with lung involvement (OR = 6.8; CI 95%, 1.3-46.4) were more represented in the clusters. Classical epidemiological investigation confirmed a recent transmission in 33% of clustered cases.

CONCLUSIONS

The use of both classical and molecular epidemiology reveals the existence of recent transmission cases of tuberculosis in an area with a low incidence of the disease.

Risk factors for development of tuberculosis after isoniazid chemoprophylaxis in human immunodeficiency virus-infected patients

The long-term benefit of isoniazid chemoprophylaxis in human immunodeficiency virus (HIV)-infected patients and risk factors for isoniazid failure were studied in 131 HIV-infected patients who received >9 months of isoniazid preventive therapy. During a median follow-up of 43 months, 8 patients developed tuberculosis (TB) (6%; 0.61 cases per 100 patient-years). Only the persistence of risk factors for exposure to TB was statistically associated with development of disease (relative hazard, 3.17; 95% confidence interval, 1.56-17; P<.001). Our data suggest reinfection as the main cause of TB after isoniazid prophylaxis.

[Characteristics of tuberculosis in a general hospital during the period 1993-1998. Analysis of resistance and HIV coinfection]

AIM

The epidemiologic and clinical characteristics, presence of HIV coinfection, and sensitivity to tuberculostatic drugs were analyzed in a series of tuberculosis patients attended in our center.

PATIENTS AND METHODS

Retrospective study of tuberculosis cases attended in a third- level hospital from 1993 to 1998.

RESULTS

During the study period, 268 cases of tuberculosis were diagnosed in our center. A progressive decrease in the incidence of this disease has occurred since 1995. Among the jailed population, we also found a decrease in cases of tuberculosis and there were no cases of resistance. In the total population, only 8 isolates (3.27%) showed resistance to some of the antituberculosis drugs studied (isoniazid, rifampicin, ethambutol, streptomycin). A tendency toward a decrease in resistance was also observed starting from 1995, with no new cases detected in the last two years. There was a 1.3% rate of primary resistance to isoniazid. Multiresistance was detected in only 4 patients, two of whom died. The rate of HIV coinfection was 38.8%. In 39% of cases the form of presentation was exclusively pulmonary and in 25% it was disseminated.

CONCLUSIONS

There was a 50% decrease in tuberculosis cases during the period studied. The rate of HIV coinfection was 38.8%, one of the highest in the literature, indicating that HIV serology should be included in the protocol for studying tuberculosis in our setting. Given the low rate of resistance detected, we recommend a three-drug regimen for antituberculosis treatment.

[Transmission of tuberculosis in the prisons of Madrid]

BACKGROUND

Prisons are recognized as high-risk settings for tuberculosis transmission. The purpose of this study was to describe the characteristics of prisoners with tuberculosis and to determine the extent of transmission of tuberculosis in the prison population of Madrid.

PATIENTS AND METHODS

Patients with positive culture for Mycobacterium tuberculosis between 1997 and 1998 from the prison system of Madrid were included. The medical records for these patients were reviewed, and they were also interviewed. Patients were included in clusters when their isolates contained 1) six or more IS6110 bands in an identical pattern or 2) five or fewer IS6110 bands that matched identically and had an identical spoligotyping pattern.

RESULTS

Culture-proven tuberculosis was diagnosed in 97 prisoners (case rate: 693 per 100.000 per year). Isolates from 73 (75%) patients were available for fingerprinting. The mean age of these patients was 33 yr (SD: 6,9), 92% were male, and 14% were immigrants. Seventy-one percent (71%) of patients were HIV-positive, 32% were active intravenous drug users and 70% nonintravenous drug users in the last two years. Primary drug resistance to isoniazid was 1,8%. Forty-one percent of prisoners (41%) were grouped in 9 clusters. Epidemiological links were found in 37% of clustered patients. Risk factors for clustering were not detected.

CONCLUSION

The results suggest recent transmission of tuberculosis in the prisons of Madrid. It is essential that correctional facilities comply fully with the recomendations for prevention and control of tuberculosis.

Recent Developments in Epidemiology, Treatment, and Diagnosis of Tuberculosis

The resurgence in cases of active tuberculosis in North America in the past decade has prompted increases in funding for tuberculosis treatment, research, and education. As a result, the number of new cases of tuberculosis has declined and cases occur in smaller pockets of well-characterized populations, such as communities of foreign-born persons and socioeconomically disadvantaged groups. New strategies for the treatment of both active and latent tuberculosis may soon include the newly licensed, long-acting rifamycin, rifapentine, but further studies are needed to determine optimal dosing regimens for this agent. Experts in tuberculosis and HIV infection have made headway in defining the optimal therapy for each current therapeutic option, and recently published guidelines are a useful document for clinicians. Rifabutin-based regimens are one approach toward achieving the optimal treatment of both diseases simultaneously. Finally, newly licensed molecular diagnostic tests for direct use on clinical specimens are intriguing, but their clinical utility remains to be defined.

Multi-drug resistant tuberculosis in Finland--a forecast

Since the collapse of the Soviet system, travel between the St Petersburg district and the Baltic states and Finland has increased substantially. Although it is difficult to obtain exact figures on the number of cases of tuberculosis (TB) and multi-drug resistant (MDR) TB in these countries, there is strong evidence of growing epidemics, bringing added epidemiological threat to Finland. The purpose of this study is to produce a short-term "worst case" forecast of the spatial development of a threatened MDR-TB epidemic in Finland. The method applied is a chorological multistep procedure using statistical and geographical methods and a simulation technique. Instead of focusing on populations of carriers and susceptibles, emphasis is placed on identifying the primary influences directing the epidemic as a spatial process. This was done by dividing Finland into small-area units and by assigning the risk of obtaining MDR-TB to each unit based on socioeconomic and structural characteristics of the population. The simulated 6 year cumulative distribution of new MDR-TB cases showed a marked concentration of cases in the capital region and in a cluster of municipalities along the west coast. Although socioeconomic factors are important in explaining the distribution of cases, frequent and widespread international contacts seemed to be equally important at the beginning of the epidemic.

Nosocomial transmission of Mycobacterium bovis resistant to 11 drugs in people with advanced HIV-1 infection

BACKGROUND

Since 1990, several nosocomial outbreaks of multidrug-resistant (MDR) tuberculosis have occurred, none of which have involved Mycobacterium bovis. We describe an epidemic of nosocomial and primary MDR M bovis tuberculosis from December, 1993, to February, 1995, among HIV-1-infected patients in a district of Madrid.

METHODS

We undertook genetic characterisation of the M bovis strain and investigated its presence in a tuberculosis epidemic in a Madrid hospital in a case-controlled study. We assessed 19 cases diagnosed with MDR tuberculosis due to M bovis during the study period. For the control group, we randomly selected 33 patients with HIV-1 infection and isolation of a strain of M tuberculosis susceptible to isoniazid, rifampicin, or both, who were treated in Ramón y Cajal Hospital. Infection-control policies and practices were implemented.

FINDINGS

We detected 19 cases in HIV-1-infected patients of primary MDR tuberculosis produced by M bovis resistant to 11 antituberculosis drugs. We found phenotypic and genotypic similarities in the strains of M bovis. In the case group, the index case and two other cases had had previous contact with another hospital that had had an MDR tuberculosis outbreak. All patients died after a mean of 44 days (range 2-116), despite multidrug treatment with first-line and second-line antituberculosis drugs. The cases with M bovis MDR tuberculosis were significantly more likely than controls to have been admitted to a hospital ward at the same time as patients already infected with MDR tuberculosis during the 10 months before their diagnosis (adjusted odds ratio 94.6 [95% CI 9.4-956.3], p < 0.0001). Advanced HIV-1 immunosuppression was associated with the development of MDR tuberculosis. Implementation of control measures stopped the epidemic.

INTERPRETATION

An M bovis primary MDR tuberculosis epidemic that cannot be treated effectively and with high mortality has emerged in Europe and has been transmitted between hospitals.

Tuberculosis in the hospice--a cause for concern?

Open pulmonary tuberculosis has been increasingly seen in HIV-infected patients in this hospice. Multidrug-resistant tuberculosis is a new and serious threat and two cases have occurred in our hospice in the past two years. This infection poses a health risk to staff, patients, relatives and volunteers. Palliative care teams in the hospice and community must have an index of suspicion for this infection, take active measures to ensure patient compliance with tuberculosis treatment and be prepared to implement infection control guidelines when needed.

Multidrug-resistant tuberculosis in an HIV-positive man in the United Kingdom

Multidrug-resistant Mycobacterium tuberculosis infection (MDR-TB) in those who are HIV positive has until now been largely a North American phenomenon. We report a fatal case in London.

Synthesis of a pentasaccharide fragment of Polysaccharide II of Mycobacterium tuberculosis

Stereocontrolled, stepwise synthesis of decyl glycosides of alpha-(1-->2)-linked di- to pentaglucosides (1-5) is described; these constitute fragments of Polysaccharide II of Mycobacterium tuberculosis. Phenyl 3,4,6-tri-O-acetyl-2-O-benzyl-1-thio-alpha-D- glucopyranoside (7) was used as the single key intermediate, obtained from 1,3,4,6-tetra-O-acetyl-2-O-benzyl-beta-D-glucopyranose (6) and PhSSiMe3. Halogenolysis of 7 afforded the isolated beta bromide (10) and beta chloride (13). Solvolysis of 10 with decanol without heavy metal salts gave decyl 3,4,6-tri-O-acetyl-2-O-benzyl-alpha-D-glucopyranoside (14) in a highly stereoselective reaction, in high yield. Subsequent, iterative hydrogenolytic removal of the O-benzyl group and glycosylation with the beta-chloride 13 under catalysis by silver salts afforded the protected di- to penta-saccharide glycosides 16, 19, 21, and 23, which were conventionally deblocked.

Anergy, AIDS and tuberculosis

Human immunodeficiency virus causes an immunological 'state of anergy'. This state is due to a defective function of antigen-presenting cells, a depletion of CD4+ helper cells, a reduction in the production of soluble factors required for signal transduction, and a decrease in cytotoxic cell activation. The human immunodeficiency virus epidemic has resulted in a global resurgence of tuberculosis. Tuberculin skin testing is negative in 58% of the patients with acquired immunodeficiency syndrome who develop tuberculosis. The mechanism leading to a state of anergy and the mechanism leading to dissemination of dormant tuberculosis appear to be identical.

Inner-city tuberculosis in the USA

Tuberculosis (TB) has become more common during the past five years in several areas of the USA. Occurrence has been facilitated by the increasing number of patients with concurrent HIV infection, by cases due to multiple-drug-resistant strains, by incomplete TB therapy among homeless and non-compliant patients, and by cases in immigrants from other countries where TB prevalence is high. These features mean that the major burden of TB today is being borne by inner-city health care facilities that care for the poor. This is illustrated by data from Atlanta, Georgia, where a large proportion of the new cases recognized in the metropolitan area are reported by Grady Memorial Hospital, the public hospital serving the indigent and working poor of the inner city. Similar patterns are recognized in the other USA cities where TB has again become a blight. In view of these epidemiological features, minimizing inner-city TB will require careful attention to diagnosis and isolation procedures in the hospital. Engineering changes at hospitals providing acute care of TB have recently been ordered by the federal government. These promise to be very expensive, and primarily affect the public hospitals, which can least afford them. Innovative treatment programmes are essential, as follow-up after acute care is difficult in this setting. Directly observed therapy can help, but for some cases the era of the TB hospital may have returned. Current attention focuses on legal and ethical issues associated with detaining non-compliant and recalcitrant patients to complete their therapy. Bacille Calmette Guerin (BCG) vaccine is not a priority for this setting at this time.(ABSTRACT TRUNCATED AT 250 WORDS)