Evaluación de las medidas de control adoptadas frente a la epidemia de tuberculosis multirresistente asociada al sida en un hospital hispanoamericano

The host-pathogen-environment triad: Lessons learned through the study of the multidrug-resistant Mycobacterium tuberculosis M strain

Multidrug-resistant tuberculosis is one of the major obstacles that face the tuberculosis eradication efforts. Drug-resistant Mycobacterium tuberculosis clones were initially disregarded as a public health threat, because they were assumed to have paid a high fitness cost in exchange of resistance acquisition. However, some genotypes manage to overcome the impact of drug-resistance conferring mutations, retain transmissibility and cause large outbreaks. In Argentina, the HIV-AIDS epidemics fuelled the expansion of the so-called M strain in the early 1990s, which is responsible for the largest recorded multidrug-resistant tuberculosis cluster of Latin America. The aim of this work is to review the knowledge gathered after nearly three decades of multidisciplinary research on epidemiological, microbiological and immunological aspects of this highly successful strain. Collectively, our results indicate that the successful transmission of the M strain could be ascribed to its unaltered virulence, low Th1/Th17 response, a low fitness cost imposed by the resistance conferring mutations and a high resistance to host-related stress. In the early 2000s, the incident cases due to the M strain steadily declined and stabilized in the latest years. Improvements in the management, diagnosis and treatment of multidrug-resistant tuberculosis along with societal factors such as the low domestic and international mobility of the patients affected by this strain probably contributed to the outbreak containment. This stresses the importance of sustaining the public health interventions to avoid the resurgence of this conspicuous multidrug-resistant strain.

Trends of Two Epidemic Multidrug-Resistant Strains of Mycobacterium tuberculosis in Argentina Disclosed by Tailored Molecular Strategy

Two Mycobacterium tuberculosis strains-M (sublineage 4.1) and Ra (sublineage 4.3)-have long prevailed in Argentina among patients with multidrug-resistant tuberculosis (MDR-TB). Recently, budget constraints have hampered the surveillance of MDR-TB transmission. Based on whole-genome sequence analysis, we used M- and Ra-specific single nucleotide polymorphisms to tailor two multiplex allele-specific polymerase chain reactions (PCRs), which we applied to 252 stored isolates (95% of all newly diagnosed MDR-TB cases countrywide, 2015-2017). Compared with the latest data available (2007-2009), the M strain has receded (80/324 to 20/252, P < 0.0001), particularly among cross-border migrants (12/58 to 0/53, P = 0.0003) and HIV-infected people (30/97 to 7/74, P = 0.0007), but it still accounts for 4/12 new cases of extensively drug-resistant TB. Differently, the Ra strain remained stable in frequency (39/324 to 33/252) and contributed marginally to the extensive drug-resistance load (1/12). Our novel strategy disclosed recent trends of the two major MDR-TB strains, providing meaningful data to allocate control interventions more efficiently.

Impact of Infection Control Measures to Control an Outbreak of Multidrug-Resistant Tuberculosis in a Human Immunodeficiency Virus Ward, Peru

Multidrug-resistant tuberculosis (MDRTB) rates in a human immunodeficiency virus (HIV) care facility increased by the year 2000-56% of TB cases, eight times the national MDRTB rate. We reported the effect of tuberculosis infection control measures that were introduced in 2001 and that consisted of 1) building a respiratory isolation ward with mechanical ventilation, 2) triage segregation of patients, 3) relocation of waiting room to outdoors, 4) rapid sputum smear microscopy, and 5) culture/drug-susceptibility testing with the microscopic-observation drug-susceptibility assay. Records pertaining to patients attending the study site between 1997 and 2004 were reviewed. Six hundred and fifty five HIV/TB-coinfected patients (mean age 33 years, 79% male) who attended the service during the study period were included. After the intervention, MDRTB rates declined to 20% of TB cases by the year 2004 (P = 0.01). Extremely limited access to antiretroviral therapy and specific MDRTB therapy did not change during this period, and concurrently, national MDRTB prevalence increased, implying that the infection control measures caused the fall in MDRTB rates. The infection control measures were estimated to have cost US$91,031 while preventing 97 MDRTB cases, potentially saving US$1,430,026. Thus, this intervention significantly reduced MDRTB within an HIV care facility in this resource-constrained setting and should be cost-effective.

HIV infection and geographically bound transmission of drug-resistant tuberculosis, Argentina

Disease trends are driven by HIV co-infection and transmission of a few strains within narrow geographic niches.

During 2003–2009, the National Tuberculosis (TB) Laboratory Network in Argentina gave 830 patients a new diagnosis of multidrug-resistant (MDR) TB and 53 a diagnosis of extensively drug- resistant (XDR) TB. HIV co-infection was involved in nearly one third of these cases. Strain genotyping showed that 7 major clusters gathered 56% of patients within restricted geographic areas. The 3 largest clusters corresponded to epidemic MDR TB strains that have been undergoing transmission for >10 years. The indigenous M strain accounted for 29% and 40% of MDR and XDR TB cases, respectively. Drug-resistant TB trends in Argentina are driven by spread of a few strains in hotspots where the rate of HIV infection is high. To curb transmission, the national TB program is focusing stringent interventions in these areas by strengthening infection control in large hospitals and prisons, expediting drug resistance detection, and streamlining information-sharing systems between HIV and TB programs.

Molecular epidemiology of Mycobacterium tuberculosis, Buenos Aires, Argentina

To analyze the molecular epidemiology of Mycobacterium tuberculosis strains at a hospital in Buenos Aires, Argentina, and mutations related to multidrug-resistant and extensively drug-resistant tuberculosis, we conducted a prospective case-control study. Our findings reinforce the value of incorporating already standardized molecular methods for rapidly detecting resistance.

Guía de práctica clínica de la Sociedad Andaluza de Enfermedades Infecciosas (SAEI) sobre el tratamiento de la tuberculosis

The therapeutic scheme for initial pulmonary tuberculosis recommended by the SAEI is as follows: Initial phase, isoniazid, rifampin and pyrazinamide given daily for 2 months. In HIV(+) patients and immigrants from areas with a rate of primary resistance to isoniazid > 4%, ethambutol should be added until susceptibility studies are available. Second phase (continuation phase): rifampin and isoniazid, given daily or intermittently for 4 months in the general population. HIV(+) patients (< or = 200 CD4) and culture-positive patients after 2 months of treatment should receive a 7-month continuation phase. A 6-month regimen is recommended for extrapulmonary tuberculosis, with the exception of tuberculous meningitis, which should be treated for a minimum of 12 months and bone/joint tuberculosis, treated for a minimum of 9 months. Treatment regimens for multidrug resistant tuberculosis are based on expert opinion. These would include a combination of still-useful first-line drugs, injectable agents, and alternative agents, such as quinolones. Patients who present a special risk of transmitting the disease or of non-adherence should be treated with directly observed therapy.

HIV infection and multidrug-resistant tuberculosis: the perfect storm

BACKGROUND

Multidrug-resistant (MDR) tuberculosis (TB) has emerged as a global epidemic, with ~425,000 new cases estimated to occur annually. The global human immunodeficiency virus (HIV) infection epidemic has caused explosive increases in TB incidence and may be contributing to increases in MDR-TB prevalence.

METHODS

We reviewed published studies and available surveillance data evaluating links between HIV infection and MDR-TB to quantify convergence of these 2 epidemics, evaluate the consequences, and determine essential steps to address these epidemics.

RESULTS

Institutional outbreaks of MDR-TB have primarily affected HIV-infected persons. Delayed diagnosis, inadequate initial treatment, and prolonged infectiousness led to extraordinary attack rates and case-fatality rates among HIV-infected persons. Whether this sequence occurs in communities is less clear. MDR-TB appears not to cause infection or disease more readily than drug-susceptible TB in HIV-infected persons. HIV infection may lead to malabsorption of anti-TB drugs and acquired rifamycin resistance. HIV-infected patients with MDR-TB have unacceptably high mortality; both antiretroviral and antimycobacterial treatment are necessary. Simultaneous treatment requires 6-10 different drugs. In HIV-prevalent countries, TB programs struggle with increased caseloads, which increase the risk of acquired MDR-TB. Surveillance data suggest that HIV infection and MDR-TB may converge in several countries.

CONCLUSIONS

Institutional outbreaks, overwhelmed public health programs, and complex clinical management issues may contribute to the convergence of the MDR-TB and HIV infection epidemics. To forestall disastrous consequences, infection control, rapid case detection, effective treatment, and expanded program capacity are needed urgently.

Tuberculous meningitis in HIV-infected patients: drug susceptibility and clinical outcome

The objective of this study was to identify prognostic factors of death in patients with tuberculous meningitis (TM) and show the impact of infection by multidrug-resistant strains on the outcome of this disease. We retrospectively analysed clinical charts of HIV-infected patients with culture-confirmed TM attending our institution during 1996-2004. The following variables were associated with death during hospitalization: neurological signs at admission, a CD4 T-cell count less than 50 cells/microl and infection by multidrug-resistant strains.