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Methicillin-resistant Staphylococcus aureus (MRSA) is a human pathogen that has diverse molecular heterogeneity. Most MRSA strains in the United States are pulsed-field gel electrophoresis USA100 sequence type (ST) 5 and USA300 ST8. Infections with MRSA ST239-III are common and found during health care-associated outbreaks. However, this strain has been rarely reported in the United States. As part of a study supported by the Prevention Epicenter Program of the Centers for Disease Control and Prevention (Atlanta, GA, USA), which evaluated transmission of MRSA among hospitals in Ohio, molecular typing identified 78 (6%) of 1,286 patients with MRSA ST239-III infections. Ninety-five percent (74/78) of these infections were health care associated, and 65% (51/78) of patients had histories of invasive device use. The crude case-fatality rate was 22% (17/78). Identification of these strains, which belong to a virulent clonal group, emphasizes the need for molecular surveillance. [ABSTRACT FROM AUTHOR]

Mutations in the staphylococcal virulence regulator gene agr frequently occur during Staphylococcus aureus infection. Whether agr-defective strains are fit for colonization, an important prerequisite for infection, is unknown. Screening by means of assays to detect delta-hemolysin activity and agr autoinducing peptide production indicated that 15 ( approximately 9%) of 160 healthy human subjects were colonized with an agr-defective strain or a mixture of agr-positive and -defective S. aureus strains. The presence of identical agr-defective strains in family members suggests that these strains are transmissible. Additionally, carriage of an agr-defective strain was associated with hospitalization, raising the possibility that such strains may be selected in a nosocomial setting. Copyright © 2008 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

We describe the genotypic and phenotypic characteristics of a mono-rifampin-resistant (RIF(R)) Mycobacterium tuberculosis strain cluster (designated AU-RIF(R)) and the acquisition of additional drug resistance. Drug susceptibility, sequences of regions that determine drug resistance, and basic clinical data were examined. A rare codon duplication (514(TTC)) in rpoB conferring high levels of RIF(R) (minimum inhibitory concentration of >256 microg/mL) in 29 isolates was identified. AU-RIF(R) strains developed secondary resistance to isoniazid and 7 resistance combinations to 6 different antibiotics. Patients infected with AU-RIF(R) strains were primarily immunocompromised. These data suggest that host factors, such as HIV status, may allow dissemination of mono-RIF(R) strains and facilitate the accumulation of additional drug resistance. Copyright © 2008 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

We studied genetic relationships among 5069 Mycobacterium tuberculosis strains recovered from patients enrolled in 4 population-based studies in the United States and Europe, by analysis of 36 synonymous single-nucleotide polymorphisms (SNPs). All strains were assigned to 1 of 9 major genetic clusters based on sSNP profile. The same 9 genetic clusters were revealed by analysis of 227 nonsynonymous SNPs, 121 intergenic SNPs, and concatenated profiles of 578 SNPs available for a subset of 48 representative strains. IS6110 profiles, spoligotypes, and mycobacterial interspersed repetitive unit patterns were nonrandomly associated with SNP-based phylogenetic lineages, together indicating a strongly clonal population structure. Isolates of the 9 genetic clusters were not distributed with equal frequency in all localities, reflecting geographic subdivision. The SNP-based phylogenetic framework provides new insight into the worldwide evolution of M. tuberculosis and a gateway for investigating genotype-disease phenotype relationships in large samples of strains. Copyright © 2006 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

One multidrug-resistant Mycobacterium tuberculosis (MDRTB) strain, strain W, caused several nosocomial outbreaks in New York City (NYC) during 1 January 1990-31 July 1993. We reviewed all MDRTB cases verified during 1 August 1993-31 December 1999 that had isolates with either this DNA pattern or a variant of this strain, and we compared them to the outbreak cases. Of 427 DNA-confirmed cases from 1990-1999, 161 (37%) were from 1 August 1993-31 December 1999; these 161 cases, from 56 hospitals and 2 correctional sites, constituted 28% of all MDRTB cases in NYC during this period. Compared with those from 1 January 1990-31 July 1993, patients from 1 August 1993-31 December 1999 were less likely to be infected with human immunodeficiency virus, to have been born in the United States, to be homeless, to have been incarcerated, and to have epidemiological links; 16% of patients had nosocomial- and 9% had community-exposure links. This strain was disseminated widely in the community during the outbreaks; postoutbreak cases likely represent reactivated disease among individuals infected during the outbreak periods in the community. Copyright © 2003 Infectious Diseases Society of America [ABSTRACT FROM AUTHOR]

Tuberculosis among Tibetans increased in New York City between 1995 and 1999. We examined characteristics of 68 Tibetan patients compared to 702 non-Tibetan patients from Nepal, India, or China, diagnosed between January 1995 and December 1999. The number of Tibetan patients increased each year after 1995 whereas non-Tibetans remained stable during the same period. Tibetans were younger (27 vs. 44 years), more likely to be infectious (63% vs. 46%), have multidrug resistance (7% vs. 2%) and shorter time to diagnosis after arrival (9 vs. 79 months, p < 0.01). For Tibetan patients, 68% of identified contacts were evaluated. The prevalence of tuberculosis infection was 65%. In contrast, among non-Tibetan patients 88.8% of contacts were evaluated and 45.2% were infected. Outreach efforts with community leaders and educational presentations at community events have been implemented in an effort to ensure continuity of care and completion of treatment. [ABSTRACT FROM AUTHOR]

Objective: To investigate a multi-institutional outbreak of highly resistant tuberculosis and evaluate patient outcome.Design: Epidemiologic investigation of every tuberculosis case reported in New York City.Setting: Patients cared for at all public and nonpublic institutions from January 1, 1990, to August 1, 1993 (43 months).Patients: We reviewed medical and public health records and conducted clinical, epidemiologic, drug susceptibility, and restriction fragment length polymorphism (RFLP) analyses. A case was defined as tuberculosis in a patient with an isolate resistant to isoniazid, rifampin, ethambutol hydrochloride, and streptomycin (and rifabutin, if sensitivity testing included it), and, if RFLP testing was done, a pattern identical to or closely related to strain W.Main Outcome Measures: Patient survival and the conversion of sputum cultures from positive to negative.Results: Of the 357 patients who met the case definition, 267 had identical or nearly identical RFLP patterns; isolates from the other 90 patients were not available for RFLP testing. Among these 267 patients, 86% were human immunodeficiency virus (HIV)-infected, 7% were HIV-negative, and 7% had unknown HIV status. All-cause mortality was 83%. Epidemiologic linkages were identified for 70% of patients, of whom 96% likely had nosocomially acquired disease at 11 hospitals. Survival was prolonged among patients who received medications to which their isolate was susceptible, especially capreomycin sulfate, and among patients with a CD4+ T-lymphocyte count greater than 0.200 x 10(9)/L (200/microL). Treatment with isoniazid and a fluoroquinolone antibiotic was also independently associated with longer survival.Conclusions: This outbreak accounted for nearly one fourth of the cases of multidrug-resistant tuberculosis in the United States during a 43-month period. Most patients had nosocomially acquired disease, were infected with HIV, and unless promptly and appropriately treated, died rapidly. With appropriate directly observed treatment, especially combinations including an injectable medication, even severely immunocompromised patients had culture conversion and prolonged, tuberculosis-free survival. [ABSTRACT FROM AUTHOR]

Consecutive single-patient methicillin-resistant Staphylococcus aureus (MRSA) isolates (270) from 12 hospitals (8217 beds) in metropolitan New York City were collected during May 1996. In 11 of 12 hospitals, MRSA was most frequent in the general medical services. DNA typing ("fingerprinting") revealed that mecA:Tn554:PFGE (pulsed-field gel electrophoresis) type I:A:A accounted for 113 (42%) of 270 isolates, was detected in all hospitals, and was the predominant clone in 9. Thirteen of 15 I:E:F isolates were from 1 hospital, and the remaining 2 were from another hospital of the same health system. Type V:NH:E was isolated from 22 (79%) of the 28 patients with AIDS, including 8 of 9 patients from an additional hospital. Subtype V:NH:E2 was recovered from 11 patients, 9 of whom had AIDS, including all 5 AIDS patients from one floor of a nursing home affiliated with a third hospital. By using both mecA:Tn554 probes and PFGE, MRSA clusters and outbreaks may be detected and provide a rationale for appropriate infection control intervention. [ABSTRACT FROM AUTHOR]

Fluoroquinolones are potent antibacterial agents being used clinically against multidrug-resistant tuberculosis. Treatment failure is thought to arise from acquisition of fluoroquinolone resistance by Mycobacterium tuberculosis. A collection of 13 resistant clinical isolates of M. tuberculosis was examined for ciprofloxacin sensitivity relative to controls exhibiting the same IS6110 DNA type. Specific alleles were associated with distinct levels of drug susceptibility for 11 isolates that contained nucleotide changes expected to alter the amino acid sequence of the A subunit of DNA gyrase. Five different gyrA (ciprofloxacin resistance) alleles were present among 7 isolates having the W DNA subtype. These isolates, which are representative of an outbreak strain, constitute a panel of organisms that can be used to evaluate contributions of gyrase and DNA topoisomerase IV to resistance. [ABSTRACT FROM AUTHOR]