Molecular epidemiology of multidrug-resistant tuberculosis, New York City, 1995-1997

Epidemiologic Correlates of Pyrazinamide-Resistant Mycobacterium tuberculosis in New York City

Pyrazinamide (PZA) has important sterilizing activity in tuberculosis (TB) chemotherapy. We describe trends, risk factors, and molecular epidemiology associated with PZA-resistant (PZA(r)) Mycobacterium tuberculosis in New York City (NYC). From 2001 to 2008, all incident culture-positive TB cases reported by the NYC Department of Health and Mental Hygiene (DOHMH) were genotyped by IS6110-based restriction fragment length polymorphism and spoligotype. Multidrug-resistant (MDR) isolates underwent DNA sequencing of resistance-determining regions of pncA, rpoB, katG, and fabG1. Demographic and clinical information were extracted from the NYC DOHMH TB registry. During this period, PZA(r) doubled (1.6% to 3.6%) overall, accounting for 44% (70/159) of the MDR population and 1.4% (75/5511) of the non-MDR population. Molecular genotyping revealed strong microbial phylogenetic associations with PZA(r). Clustered isolates and those from acid-fast bacillus (AFB) smear-positive cases had 2.7 (95% confidence interval [CI] = 1.71 to 4.36) and 2.0 (95% CI = 1.19 to 3.43) times higher odds of being PZA(r), respectively, indicating a strong likelihood of recent transmission. Among the MDR population, PZA(r) was acquired somewhat more frequently via primary transmission than by independent pathways. Our molecular analysis also revealed that several historic M. tuberculosis strains responsible for MDR TB outbreaks in the early 1990s were continuing to circulate in NYC. We conclude that the increasing incidence of PZA(r), with clear microbial risk factors, underscores the importance of routine PZA drug susceptibility testing and M. tuberculosis genotyping for the identification, control, and prevention of increasingly resistant organisms.

A close-up on the epidemiology and transmission of multidrug-resistant tuberculosis in Poland

Multidrug-resistant tuberculosis (MDR-TB) poses a serious challenge to the global control of the disease. The purpose of this study was to characterize MDR-TB patients from Poland and to determine the extent of MDR-TB disease attributable to recent transmission. The study included all 46 patients diagnosed with MDR-TB in Poland in 2004 and followed up for 6 years (until 2011). For each patient, sociodemographic and clinical characteristics, treatment outcomes, and bacteriological data were collected by the review of medical and laboratory records. Mycobacterium tuberculosis isolates from all patients were characterized using spoligotyping, mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing, IS6110 restriction fragment length polymorphism (RFLP) analysis, and sequencing analysis of drug resistance-associated loci (katG, mabA-inhA, rpoβ, rpsL, and embB). The majority of patients were male (86.9%), 40-64 years of age (60.8%), with a history of TB treatment (84.8%), and producing smear-positive sputa (86.9%). Twenty-two (47.8%) patients suffered from concomitant diseases and 28 (60.8%) were alcohol abusers. Treatment outcome assessment revealed that 8 (17.4%) patients were cured or completed therapy, while 15 (32.6%) died of TB, 11 (23.9%) defaulted, 8 (17.4%) failed, and 1 (2.2%) was transferred and lost to follow-up. Upon genotyping, 10 (21.7%) isolates were allocated in four clusters. These were further subdivided by mutational profiling. Overall, in 6 (13%) patients, MDR-TB was a result of recent transmission. For 4 (8.7%) of these patients, a direct epidemiological link was established. The study shows that the transmission of MDR-TB occurs at a low rate in Poland. Of urgent need is the implementation of a policy of enforced treatment of MDR-TB patients in Poland.

Transmission of multidrug-resistant tuberculosis in the USA: a cross-sectional study

BACKGROUND

Multidrug-resistant (MDR) tuberculosis is a potential threat to tuberculosis elimination, but the extent of MDR tuberculosis disease in the USA that is attributable to transmission within the country is unknown. We assessed transmission of MDR tuberculosis and potential contributing factors in the USA.

METHODS

In a cross-sectional study, clinical, demographic, epidemiological, and Mycobacterium tuberculosis genotype data were obtained during routine surveillance of all verified cases of MDR tuberculosis reported from eight states in the USA (California from Jan 1, 2007, to Dec 31, 2009; Texas from Jan 1, 2007, to March 31, 2009; and the states of Colorado, Maryland, Massachusetts, New York, Tennessee, and Washington from Jan 1, 2007 to Dec 31, 2008). In-depth interviews and health-record abstraction were done for all who consented to ascertain potential interpersonal connections.

FINDINGS

168 cases of MDR tuberculosis were reported in the eight states during our study period. 92 individuals (55%) consented to in-depth interview. 20 (22%) of these individuals developed MDR tuberculosis as a result of transmission in the USA; a source case was identified for eight of them (9%). 20 individuals (22%) had imported active tuberculosis (ie, culture-confirmed disease within 3 months of entry into the USA). 38 (41%) were deemed to have reactivation of disease, of whom 14 (15%) had a known previous episode of tuberculosis outside the USA. Five individuals (5%) had documented treatment of a previous episode in the USA, and so were deemed to have relapsed. For nine cases (10%), insufficient evidence was available to definitively classify reason for presentation.

INTERPRETATION

About a fifth of cases of MDR tuberculosis in the USA can be linked to transmission within the country. Many individuals acquire MDR tuberculosis before entry into the USA. MDR tuberculosis needs to be diagnosed rapidly to reduce potential infectious periods, and clinicians should consider latent tuberculosis infection treatment-tailored to the results of drug susceptibility testing of the putative source case-for exposed individuals.

FUNDING

Centers for Disease Control and Prevention.

Mycobacterium tuberculosis genotype Beijing: About 15 strains and their part in MDR-TB outbreaks in Algeria

Within the framework of epidemiological surveillance by molecular typing tools conducted in the NRL on multi-resistant strains, the application of spoligotyping on a group of 390 strains consisting of 389 DR-MTB strains and 1 susceptible strain isolated from patients made it possible to detect the presence of 15 strains belonging to the Beijing genotype. All 15 strains were genotyped by MTBDRplus. Among the 15 strains, 11 were typed by RFLP and 9 by MIRU-VNTR. After analysis of the profiles obtained by the software MIRU-VNTRplus, two spoligotypes (st No. 1 and st No. 265) and four RFLP profiles and a complete identity profile by MIRU-VNTR, information collected on patients allowed the research team to detect a family tie among patients of three different families, as well as one nosocomial TB transmission. The percentage of Beijing strains found among the patients in this study was 3.8%; this figure does not reflect the reality because it was calculated from an essay on MDR-TB. To get an idea of the prevalence of Beijing TB strains in this country, a more extensive study is currently being considered.

Use of tuberculosis genotyping for postoutbreak monitoring

CONTEXT

Review of routinely collected tuberculosis genotyping results following a known outbreak is a potential mechanism to examine the effectiveness of outbreak control measures.

OBJECTIVE

To assess differences in characteristics between outbreak and postoutbreak tuberculosis cases.

DESIGN

Retrospective.

SETTING

United States.

PARTICIPANTS

All tuberculosis cases identified as a result of >5-person outbreaks investigated by the Centers for Disease Control and Prevention during 2003 to 2007 (original outbreak cases), and subsequent culture-positive tuberculosis cases with matching Mycobacterium tuberculosis genotypes reported in the same county during 2004 to 2008 (postoutbreak cases).

MAIN OUTCOME MEASURE

Proportion of demographic, social, and clinical characteristics of tuberculosis outbreak cases compared to postoutbreak cases. SECONDARY: Proportion of demographic, social, and clinical characteristics of epidemiologically linked versus nonlinked cases.

RESULTS

Six outbreaks with 111 outbreak cases and 110 postoutbreak cases were identified. Differences between outbreak and postoutbreak cases were gender (69% vs 85% male; P < .01), birth origin (3% vs 11% foreign-born; P = .02), disease severity (48% vs 62% sputum smear-positive; P = .04), homelessness (38% vs 51%; P = .05), and injection drug use (4% vs 11%; P = .04). For 5 of the 6 outbreaks, the status of epidemiologic relationships among postoutbreak cases was available (n = 89). The postoutbreak cases with a known epidemiologic link to the original outbreak were in younger persons (aged 39 vs 47 years; P < .01), and a larger proportion reported injection drug use (18% vs 4%; P = .04) or noninjection drug use (44% vs 18%; P < .01) than those without a reported link.

CONCLUSIONS

Health jurisdictions can utilize genotyping data to monitor and define the characteristics of postoutbreak cases related to the original outbreak.

Thioridazine cures extensively drug-resistant tuberculosis (XDR-TB) and the need for global trials is now!

Thioridazine (TDZ) has been shown to have in vitro activity against multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains of Mycobacterium tuberculosis, to promote the killing of intracellular MDR and XDR strains and to cure the mouse of antibiotic-susceptible and -resistant pulmonary tuberculosis (TB) infections. Recently, TDZ was used to cure 10 of 12 XDR-TB patients in Buenos Aires, Argentina. At the time of writing, it is being used for the therapy of non-antibiotic-responsive terminal XDR-TB patients in Mumbai, India, on the basis of compassionate therapy and although it is too early to determine a cure, the patients have improved appetite, weight gain, are afebrile and free of night sweats, and their radiological picture shows great improvement. Because XDR-TB is essentially a terminal disease in many areas of the world and no new effective agents have yet to yield successful clinical trials, global clinical trials for the therapy of XDR-TB are urgently required.

Lower gastrointestinal tract tuberculosis: an important but neglected disease

PURPOSE

Difficulties in early and accurate diagnosis of intestinal tuberculosis lead to frequent misdiagnosis even in endemic areas. This study aimed to investigate clinical and laboratory characteristics of patients with lower gastrointestinal tract tuberculosis (LGITB).

MATERIALS AND METHODS

Patients who met the criteria for LGITB in a medical center from 1997 to 2006 were identified and their medical records reviewed.

RESULTS

A number of 4,567 patients with culture or histology-proven tuberculosis were identified, and 30 (0.66%) were diagnosed with LGITB. Principal co-morbidities were type II diabetes mellitus (23%) and alcoholism (23%). Twenty-two (73%) had radiographic findings suggestive of pulmonary tuberculosis, which was culture-proven in 13. Mycobacterial cultures from stool or sputum had diagnostic yields of about 50%, comparable to that of histological studies of colonoscopic or surgical biopsies. Multidrug-resistant tuberculosis (MDRTB) was identified in four patients, including two alcoholics. Fourteen underwent surgery; two (14%) received right hemicolectomy under the diagnosis of colon cancer without pre- or intraoperative histological study. The 1-year mortality was 20% but was 50% in patients with MDRTB.

CONCLUSIONS

A high rate of alcoholism and diabetes mellitus and a high percentage of MDRTB among alcoholics were observed in our patients with LGITB. The diagnostic yields of stool or sputum mycobacterial culture (50%) were similar to that of intestinal histological study. Pre- or intraoperative histological examination could prevent unnecessarily extensive surgery.

Molecular genetics of para-aminosalicylic acid resistance in clinical isolates and spontaneous mutants of Mycobacterium tuberculosis

The emergence of Mycobacterium tuberculosis resistant to first-line antibiotics has renewed interest in second-line antitubercular agents. Here, we aimed to extend our understanding of the mechanisms underlying para-aminosalicylic acid (PAS) resistance by analysis of six genes of the folate metabolic pathway and biosynthesis of thymine nucleotides (thyA, dfrA, folC, folP1, folP2, and thyX) and three N-acetyltransferase genes [nhoA, aac(1), and aac(2)] among PAS-resistant clinical isolates and spontaneous mutants. Mutations in thyA were identified in only 37% of the clinical isolates and spontaneous mutants. Overall, 24 distinct mutations were identified in the thyA gene and 3 in the dfrA coding region. Based on structural bioinformatics techniques, the altered ThyA proteins were predicted to generate an unfolded or dysfunctional polypeptide. The MIC was determined by Bactec/Alert and dilution assay. Sixty-three percent of the PAS-resistant isolates had no mutations in the nine genes considered in this study, revealing that PAS resistance in M. tuberculosis involves mechanisms or targets other than those pertaining to the biosynthesis of thymine nucleotides. The alternative mechanism(s) or pathway(s) associated with PAS resistance appears to be PAS concentration dependent, in marked contrast to thyA-mutated PAS-resistant isolates.

Management of pediatric multidrug-resistant tuberculosis and latent tuberculosis infections in New York City from 1995 to 2003

BACKGROUND

Few studies have assessed the management and outcomes of multidrug-resistant tuberculosis (MDR-TB) in the pediatric population. Treatment of children with second-line TB drugs is complicated by potential toxicities of these agents.

METHODS

We performed a retrospective study of children <15 years of age treated for MDR-TB or MDR-latent TB infection (LTBI) from 1995 to 2003. We reviewed the New York City Department of Health and Mental Hygiene (DOHMH) computerized TB registry to characterize demographic characteristics, clinical presentations, treatment, and outcomes of the study subjects.

RESULTS

Twenty subjects with MDR-TB (mean age 2.7 years) and 51 with MDR-LTBI (mean age 9.8 years) were studied. The most commonly used second-line TB drugs were cycloserine, quinolone agents, and ethionamide, which were used in 70%, 69%, and 54% of subjects, respectively. Sixteen (80%) of 20 MDR-TB and 38 (75%) of 51 MDR-LTBI cases completed treatment. A greater proportion of subjects receiving care at a DOH clinic completed treatment for LTBI (36/41, 88%), when compared with subjects treated at non-DOH sites [(2/9, 22%) P < 0.001]. Review of the TB registry indicated that no subjects had recurrent disease or progression of LTBI to active disease during the study period and for 2 years thereafter.

CONCLUSIONS

Children with MDR-TB and LTBI were best cared for in public health settings. A multicenter registry for pediatric MDR-TB and MDR-LTBI would be desirable to obtain accurate rates of toxicity and cure.

Management of multidrug-resistant tuberculosis: Update 2007

Multidrug-resistant tuberculosis (MDR-TB) with bacillary resistance to at least isoniazid and rifampicin in vitro is a worldwide phenomenon. Hot spots of the disease are found scattered in different continents. Prevention of its development through good tuberculosis control programmes operating under the directly observed therapy, short-course (DOTS) strategy is of paramount importance. However, with established MDR-TB, treatment with alternative and specific chemotherapy is necessary to achieve a beneficial outcome. Such an approach on a programme basis is currently known as the 'DOTS-Plus' strategy. Second-line (reserve) drugs utilized in the treatment of MDR-TB are generally less potent and more toxic, perhaps with the notable exceptions of some fluoroquinolones and injectable agents. Surgery has a distinct adjunctive role for the management of MDR-TB in selected patients. The emergence of extensively drug-resistant tuberculosis (XDR-TB), that is, MDR-TB with additional bacillary resistance to the fluoroquinolones and injectables, has provided a very alarming challenge to global health, as the disease currently has a low cure rate and high mortality. In order to combat XDR-TB, strengthening of DOTS and DOTS-Plus programmes is mandatory, especially in the face of surging HIV infection. Furthermore, more attention needs to be focused on developing new drugs with potent bactericidal and sterilizing activities and low side-effects, and above all, drugs that are affordable for communities worldwide.

Enhanced killing of intracellular multidrug-resistant Mycobacterium tuberculosis by compounds that affect the activity of efflux pumps

Whereas human neutrophils are effective and efficient killers of bacteria, macrophages such as those derived from monocytes are almost devoid of killing activity. Nevertheless, monocytes can be transformed into effective killers of mycobacteria or staphylococci when exposed to clinical concentrations of a phenothiazine or to inhibitors of efflux pumps (reserpine and verapamil), or to ouabain, an inhibitor of K(+) transport. Because the rates of multidrug-resistant Mycobacterium tuberculosis (MDR-TB) continue to escalate globally, and because no new effective drug has been made available for almost 40 years, compounds that enhance the killing activity of monocytes against MDR-TB are obviously needed. This review covers the specific characteristics of MDR-TB, identifies a variety of agents that address these characteristics and therefore have potential for managing MDR-TB. Because the mechanism by which these agents enhance the killing of intracellular bacteria is important for the intelligent design of new anti-tubercular agents, the review correlates the mechanisms by which these agents manifest their effects. Lastly, a model is presented which describes the mechanisms by which distinct efflux pumps of the phagosome-lysosome complex are inhibited by agents that are known to inhibit K(+) flux. The model also predicts the existence of a K(+) activated exchange (pump) that is probably located in the membrane that delineates the lysosome. This putative pump, which is immune to inhibitors of K+ flux, is identified as being the cause for the acidification of the lysosome thereby activating its hydrolytic enzymes. Because the non-killer macrophage can be transformed into an effective killer by a variety of compounds that inhibit K(+) transport, perhaps it would be wise to develop drugs that enhance the killing activity of these cells inasmuch as this approach would not be subject to any resistance, as is the eventual case for conventional antibiotics.

Strain-specific differences in two large Mycobacterium tuberculosis genotype clusters in isolates collected from homeless patients in New York City from 2001 to 2004

We studied two large Mycobacterium tuberculosis genotype clusters associated with recent outbreaks in homeless persons to determine factors associated with these tuberculosis (TB) strains. Isolates from all culture-positive TB cases diagnosed from 1 January 2001 to 31 December 2004 were genotyped. Patients whose isolates had identical restriction fragment length polymorphism patterns and spoligotypes were considered clustered. Health department records were reviewed and reinterviews attempted for clustered cases. Patients with the Cs30 and BEs75 strains were compared to other genotypically clustered cases and to each other. The two largest genotype clusters among homeless persons were the Cs30 strain (n = 105) and the BEs75 strain (n = 47). Fifty-one (49%) patients with the Cs30 strain and 28 (60%) with the BEs75 strain were homeless. Compared to patients with the BEs75 strain, patients with the Cs30 strain were less likely to be respiratory acid-fast bacillus smear positive (51% versus 72%). Furthermore, patients with the BEs75 strain were more likely to be HIV infected (74% versus 42%), which suggests that most patients with this strain advanced to disease after recent infection. Cases in clusters of strains that have been circulating in the community over a long time period, such as the Cs30 strain, require additional investigation to determine whether clustering is a result of recent transmission or reactivation of remote infection.

Molecular epidemiology of tuberculosis after declining incidence, New York City, 2001-2003

Tuberculosis incidence in New York City (NYC) declined between 1992 and 2000 from 51.1 to 16.6 cases per 100,000 population. In January 2001, universal real-time genotyping of TB cases was implemented in NYC. Isolates from culture-confirmed tuberculosis cases from 2001 to 2003 were genotyped using IS6110 and spoligotype to describe the extent and factors associated with genotype clustering after declining TB incidence. Of 2408 (91.8%) genotyped case isolates, 873 (36.2%) had a pattern indistinguishable from that of another study period case, forming 212 clusters; 248 (28.4%) of the clustered cases had strains believed to have been widely transmitted during the epidemic years in the early 1990s in NYC. An estimated 27.4% (873 minus 212) of the 2408 cases were due to recent infection that progressed to active disease during the study period. Younger age, birth in the United States, homelessness, substance abuse and presence of TB symptoms were independently associated with greater odds of clustering.

Universal genotyping in tuberculosis control program, New York City, 2001-2003

Real-time universal genotyping decreased unnecessary treatment.

In 2001, New York City implemented genotyping to its tuberculosis (TB) control activities by using IS6110 restriction fragment length polymorphism (RFLP) and spoligotyping to type isolates from culture-positive TB patients. Results are used to identify previously unknown links among genotypically clustered patients, unidentified sites of transmission, and potential false-positive cultures. From 2001 to 2003, spoligotype and IS6110-based RFLP results were obtained for 90.7% of eligible and 93.7% of submitted isolates. Fifty-nine (2.4%) of 2,437 patient isolates had false-positive culture results, and 205 genotype clusters were identified, with 2–81 cases per cluster. Cluster investigations yielded 57 additional links and 17 additional sites of transmission. Four additional TB cases were identified as a result of case finding initiated through cluster investigations. Length of unnecessary treatment decreased among patients with false-positive cultures.

Trends in Drug-Resistant Mycobacterium tuberculosis in New York City, 1991-2003

BACKGROUND

Two drug-resistance surveys showed a very high prevalence of drug resistance among isolates obtained from patients with tuberculosis in 1991 and 1994 in New York, New York.

METHODS

A cross-sectional survey in April 1997 and a survey of incident cases in April-June 2003 were conducted. The trend in the proportion of drug resistance in the 4 surveys was examined separately for prevalent and incident cases. Risk factors for drug resistance in incident cases were also assessed.

RESULTS

The number of patients was 251 in the 1997 survey and 217 in the 2003 survey. Among prevalent cases, the percentage of cases with resistance to any antituberculosis drug decreased from 33.5% in 1991 to 23.8% in 1994 and to 21.5% in 1997 (P < .001, by test for trend); cases of multidrug-resistant tuberculosis also decreased significantly, from 19% in 1991 to 6.8% in 1997 (P < .001, by test for trend). Among incident cases in the 4 surveys, the decrease in resistance to any antituberculosis drugs was not statistically significant; however, the decrease in multidrug-resistant tuberculosis (from 9% in 1991 to 2.8% in 2003) was statistically significant (P = .002, by test for trend). However, in 2003, a worrisome increase in incident cases of multidrug-resistant tuberculosis (an increase of 23%) was seen among previously treated patients with pulmonary tuberculosis not born in the United States. Human immunodeficiency virus infection, a strong predictor for drug resistance in 1991 and 1994, was not associated with drug resistance in subsequent surveys.

CONCLUSIONS

Intensive case management, including directly observed therapy, adherence monitoring, and periodic medical review to ensure appropriate treatment for each patient, should be sustained to prevent acquired drug resistance.

Multidrug-resistant tuberculosis at an HIV testing center in Haiti

OBJECTIVE

Tuberculosis is the major opportunistic infection of HIV/AIDS in developing countries. We investigated the prevalence rate of multidrug-resistant (MDR) tuberculosis at an HIV voluntary counseling and testing (VCT) center in Port-au-Prince, Haiti.

DESIGN AND METHODS

A cross-sectional prevalence study of MDR-tuberculosis was conducted at a VCT Center. All patients reporting at least 5 days of cough were screened for tuberculosis, including sputum culture. All Mycobacteria tuberculosis isolates underwent drug susceptibility testing.

RESULTS

Between January 2000 and December 2002, isolates from 330 patients underwent drug susceptibility testing. MDR-tuberculosis was documented in 16 (6%) of 281 patients with primary tuberculosis and 10 (20%) of 49 patients with recurrent tuberculosis. In patients with primary disease, 11 (10%) of 115 HIV-infected patients had MDR-tuberculosis compared with five (3%) of 166 HIV-negative patients, (risk ratio 3.2; 95% confidence interval 1.1-8.9; P = 0.0331).

CONCLUSION

Multidrug resistance was prevalent among patients found to have pulmonary tuberculosis at an HIV testing center in Port-au-Prince. Patients with primary pulmonary tuberculosis who were HIV-co-infected were more likely to have multidrug resistance than HIV-negative patients. Assiduous attention to tuberculosis infection control measures at HIV testing centers in developing countries is critical to prevent nosocomial MDR-tuberculosis transmission. Measures may include appropriate ventilation, outdoor seating, ultra-violet lights, and rapid on-site screening for tuberculosis.

Drug-resistant tuberculosis: a disease of target populations in Houston, Texas

OBJECTIVES

To analyse the traditional and molecular epidemiology of drug-resistant tuberculosis (DRTB) in Houston and Harris County, Texas in the setting of decreasing disease incidence.

METHODS

Case-control study of 193 patients with DRTB and 1977 patients with drug-susceptible TB (DSTB) identified from a population-based surveillance, 1995-2001.

RESULTS

In a multivariate logistic regression, the following risk factors were found to be predictors of having DRTB (P< or =0.05): human immunodeficiency virus (HIV) seropositivity, Hispanic ethnicity, Asian ethnicity, history of past TB; whereas being foreign born, having a history of past TB, and younger age were predictors of MDRTB. There were 15 patients who acquired drug resistance while on therapy, and they were significantly more likely than controls to be HIV-seropositive, be of Asian ethnicity, have smear-positive pulmonary disease and present with pleural effusion on chest radiograph. No difference in 6-month mortality between DRTB and DSTB cases was found. During the study period, the incidence of DRTB remained constant.

CONCLUSIONS

In Houston, there is a steady, low-level, incidence of DRTB which disproportionately affects specific subpopulations, with no evidence of increased mortality at 6 months.

Tuberculosis due to resistant Haarlem strain, Tunisia

Multidrug-resistant tuberculosis was diagnosed in 21 HIV-negative, nonhospitalized male patients residing in northern Tunisia. A detailed investigation showed accelerated transmission of a Mycobacterium tuberculosis clone of the Haarlem type in 90% of all patients. This finding highlights the epidemic potential of this prevalent genotype.

Targeted hybridization of IS6110 fingerprints identifies the W-Beijing Mycobacterium tuberculosis strains among clinical isolates

Targeted IS6110-based RFLP genotyping can be applied to rapidly identify specific groups of biomedically/epidemiologically relevant Mycobacterium tuberculosis clinical isolates. One such group is the W-Beijing strain family (also known as Beijing/W), implicated in significant nosocomial and community outbreaks worldwide. Using previously defined criteria, we developed a simple and accurate method to identify members of the W-Beijing family, based on rehybridization of Southern blot membranes used previously in routine IS6110 DNA fingerprint analysis. The hybridization probe constructed ("W-Beijing polyprobe") contains the PCR-amplified fragments specific for three M. tuberculosis chromosomal loci used for the identification of W-Beijing strains. The targets include the dnaA-dnaN and NTF regions and the direct repeat locus. A total of 526 selected clinical isolates (representative of 253 different IS6110-defined strain types) were analyzed using the W-Beijing polyprobe. A total of 148 isolates from this collection were found to be members of the W-Beijing phylogenetic lineage, comprising 106 strains from the W-Beijing family (46 clusters) and 42 related isolates. Rehybridization results were confirmed by computer-assisted analysis. The sensitivity and specificity of this method were estimated at 98.7% and 99.7%, respectively. This study demonstrates that the W-Beijing polyprobe can accurately and reliably discriminate members of the W-Beijing phylogenetic lineage and the W-Beijing family of M. tuberculosis strains.

Effects of genetic variability of Mycobacterium tuberculosis strains on the presentation of disease

The nature of the variability in the clinical and epidemiological consequences of Mycobacterium tuberculosis infection remains poorly understood. Environmental and host factors that contribute to the outcome of infection and disease presentation are well recognised, but the role of bacterial factors has been more elusive. The rapid increase in the understanding of the molecular basis of M tuberculosis over the past decades has revived research into its pathogenesis. DNA fingerprinting techniques have been used to distinguish between strains of M tuberculosis, and efforts to characterise the strains present within populations have led to increased understanding of their global distribution. This research has shown that in certain areas a small number of strains are causing a disproportionate number of cases of the disease. The sequencing of the complete genome of M tuberculosis has accelerated the development of molecular techniques to differentiate strains according to their genetic polymorphisms. Investigation into the reasons why some strains are predominant by genetic strain-typing techniques may clarify which bacterial factors contribute to disease. This knowledge has the potential to influence control and prevention strategies for tuberculosis in the future. However, there are still limitations in these techniques and their results. This review discusses molecular epidemiology and genetic studies, and their contribution to the understanding of the links between genotypic and phenotypic characteristics of M tuberculosis strains.

Detection of mutations associated with isoniazid and rifampin resistance in Mycobacterium tuberculosis isolates from Samara Region, Russian Federation

High incidence rates of isoniazid-, rifampin-, and multiple-drug-resistant tuberculosis have been reported in countries of the former Soviet Union (FSU). Genotypic (unlike phenotypic) drug resistance assays do not require viable cultures but require accurate knowledge of both the target gene and the mutations associated with resistance. For these assays to be clinically useful, they must be able to detect the range of mutations seen in isolates from the population of tuberculosis patients to which they are applied. Two novel macroarrays were applied to detect mutations associated with rifampin (rpoB) and isoniazid (katG and inhA) resistance. In a sample of 233 isolates from patients in Samara, central Russia, 46.5% of isolates possessed mutations in both the rpoB and the katG (or inhA) genes. Combined results from the macroarrays demonstrated concordance in 95.4 and 90.4% of phenotypically defined rifampin- and isoniazid-resistant isolates, respectively. The contribution of different mutations to resistance was comparable to that reported previously for non-FSU countries, with 90% of rifampin-resistant isolates and 93% of isoniazid resistant isolates due to rpoB531 and katG315 mutations, respectively. The percentage of phenotypically resistant rifampin isolates with no mutations in the rpoB codons 509 to 536 was 4.2%, which was similar to previous reports. Novel macroarrays offer a rapid, accurate, and relatively cheap system for the identification of rifampin-, isoniazid-, and multiple-drug-resistant Mycobacterium tuberculosis isolates.

Major factors affecting the emergence and re-emergence of infectious diseases

The diversity of infectious disease threats currently facing humanity is unprecedented because of the remarkable emergence and reemergence of pathogens worldwide. Because of population mobility, globalization of commerce and the food supply, and the effects of the HIV/AIDS pandemic, infections in the developing world must be addressed to prevent infections in industrialized countries. Because pathogens do not recognize national boundaries, the rapidity with which individuals can circumnavigate the globe incubating infections makes the control of communicable diseases an enormous challenge for governments as well as for the public and primary health care systems. A global strategy for dealing with infectious disease threats must be developed and implemented as soon as possible.

Tuberculosis in New York city: recent lessons and a look ahead

In the late 1980s and early 1990s, after decades of decline, the incidence of tuberculosis began to rise in New York city, reaching a peak of 3811 cases by 1992. The epidemic took root in a setting of inadequate treatment regimens, homelessness, a diminished public-health system, and the onset of the HIV/AIDS epidemic. In addition, a subepidemic of drug-resistant tuberculosis occurred throughout New York city, most notably in a series of well documented nosocomial outbreaks. By 1994, using broadened initial treatment regimens, directly observed therapy, and improved US Centers for Disease Control and Prevention guidelines for hospital control and disease prevention, New York city began to effectively halt the progression of the epidemic. By 2002, tuberculosis rates in New York city reached an historic low of 1084. However, given the presence of a large reservoir of latently infected individuals in the city and an ongoing tuberculosis pandemic, New York city continues to face significant challenges from this persistent pathogen.

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.

DNA fngerprinting of Mycobacterium tuberculosis: lessons learned and implications for the future

DNA fingerprinting of Mycobacterium tuberculosis--a relatively new laboratory technique--offers promise as a powerful aid in the prevention and control of tuberculosis (TB). Established in 1996 by the Centers for Disease Control and Prevention (CDC), the National Tuberculosis Genotyping and Surveillance Network was a 5-year prospective, population-based study of DNA fingerprinting conducted from 1996 to 2000. The data from this study suggest multiple molecular epidemiologic and program management uses for DNA fingerprinting in TB public health practice. From these data, we also gain a clearer understanding of the overall diversity of M. tuberculosis strains as well as the presence of endemic strains in the United States. We summarize the key findings and the impact that DNA fingerprinting may have on future approaches to TB control. Although challenges and limitations to the use of DNA fingerprinting exist, the widespread implementation of the technique into routine TB prevention and control practices appears scientifically justified.