Linoleic acid and α-linolenic acid inhibit conjugative transfer of an IncX4 plasmid carrying mcr-1.

AIMS: The aim of this study was to determine the effects of unsaturated fatty acids on clinical plasmids. METHODS AND RESULTS: Two unsaturated fatty acids, linoleic acid (LA) and α-linolenic acid (ALA) at final concentration 0, 0·03, 0·3 and 3 mmol l-1 , respectively, were used to assess the effects on conjugative transfer of a mcr-1-harbouring plasmid pCSZ4 (IncX4) in conjugation experiment. The inhibitory mechanisms were analysed by molecular docking and the gene expression of virB11 was quantitated by qRT-PCR. Target plasmid diversity was carried out by TrwD/VirB11 homology protein sequence prediction analysis. Our results showed that LA and ALA inhibit plasmid pCSZ4 transfer by binding to the amino acid residues (Phe124 and Thr125) of VirB11 with dose-dependent effects. The expression levels of virB11 gene were also significantly inhibited by LA and ALA treatment. Protein homology analysis revealed a wide distribution of TrwD/VirB11-like genes among over 37 classes of plasmids originated from both Gram-negative and Gram-positive bacteria. CONCLUSIONS: This study demonstrates representing a diversity of plasmids that may be potentially inhibited by unsaturated fatty acids. SIGNIFICANCE AND IMPACT OF THE STUDY: Our work reported here provides additional support for application of curbing the spread of multiple plasmids by unsaturated fatty acids.

Epidemiology of tuberculosis among healthcare personnel in New York City.

BACKGROUND: We have updated the epidemiology of tuberculosis (TB) among healthcare personnel (HCP) in New York City (NYC), USA, during a period of declining TB burden.METHODS: Using routinely collected Health Department data for NYC TB cases from 2001 to 2014, we conducted a retrospective descriptive analysis. P values were calculated using Pearson's χ² or Fisher's exact test for categorical data; Wilcoxon rank-sum test was used to compare medians. We used the Cochran-Armitage test for trend and linear regression for trend analyses.RESULTS: HCP accounted for 6% of adults with TB throughout the study period and were more likely than other adults to be female (68% vs. 37%, P ≤ 0.0001), have extrapulmonary-only disease (31% vs. 23%, P ≤ 0.0001), have an isolate with multidrug resistance (4% vs. 2%, P = 0.0211), and report a previous history of latent TB infection (LTBI) (51% vs. 23%, P ≤ 0.0001). Compared to non-US-born HCP, US-born HCP were more likely to have HIV infection (18% vs. 8%, P = 0.0011) or a genotypically clustered isolate (67% vs. 37%, P ≤ 0.0001) and less likely to report history of prior LTBI (43% vs. 54%, P = 0.0128).CONCLUSIONS: Further research is needed to explore transmission and occupational risk among HCP. New approaches are needed to optimize completion of prophylaxis for HCP with LTBI.

Klebsiella pneumoniae ST307 with OXA-181: threat of a high-risk clone and promiscuous plasmid in a resource-constrained healthcare setting.

INTRODUCTION: Klebsiella pneumoniae with OXA-48-like enzymes were introduced into Tshwane Tertiary Hospital (TTH) (Pretoria, South Africa) during September 2015, causing nosocomial outbreaks. METHODS: PCR methodologies and WGS were used to characterize K. pneumoniae with carbapenemases (n = 124) from TTH (July 2015-December 2016). RESULTS: PCR was used to track K. pneumoniae ST307 with OXA-181 among 60% of carbapenemase-positive isolates in different wards/units over time and showed the transmission of IncX3 plasmids to other K. pneumoniae clones. WGS identified different ST307 clades: 307_OXA181 (consisting of two lineages, A and B) with OXA-181 on IncX3 plasmids (named p72_X3_OXA181) and clade 307_VIM with VIM-1 on IncFII plasmids. Clade 307_OXA181 lineage B was responsible for the rapid increase and transmission of OXA-181 K. pneumoniae in various wards/units throughout TTH, while the numbers of clade 307_OXA181 lineage A and clade 307_VIM remained low. Separate outbreaks were due to K. pneumoniae ST17 and ST29 with p72_X3_OXA181 plasmids. CONCLUSIONS: The high-risk clone K. pneumoniae ST307 with OXA-181 rapidly spread to different wards/units despite infection and prevention measures. ST307 clades and lineages seemingly acted differently in outbreak situations. This study also highlighted the threat of promiscuous plasmids such as p72_X3_OXA181.

Dual ß-Lactam Combinations Highly Active against Mycobacterium abscessus Complex In Vitro.

As a consequence of a growing population of immunocompromised individuals, including transplant recipients and cystic fibrosis patients, there has been a dramatic increase in chronic infections caused by Mycobacterium abscessus complex (MABC) strains that are usually recalcitrant to effective antibiotic therapy. The recent rise of macrolide resistance in MABC has further complicated this clinical dilemma, dramatizing the need for novel agents. The repurposing of current antibiotics is one rapid path from discovery to patient care. In this study, we have discovered that dual ß-lactams, and specifically the combination of ceftazidime with either ceftaroline or imipenem, are synergistic and have clinically relevant activities, with MIC50s of 0.25 (ceftaroline with 100 µg/ml ceftazidime) and 0.5 µg/ml (imipenem with 100 µg/ml ceftazidime) against clinical MABC isolates. Similar synergy was observed in time-kill studies against the M. abscessus ATCC 19977 strain using clinically achievable concentrations of either imipenem (4 µg/ml) or ceftaroline (2 µg/ml), as the addition of ceftazidime at concentrations of ≥50 µg/ml showed a persistent bactericidal effect over 5 days. Treatment of THP-1 human macrophages infected with three different M. abscessus clinical isolates supported the in vitro findings, as the combination of 100 µg/ml ceftazidime and 0.125 µg/ml ceftaroline or 100 µg/ml ceftazidime and 0.25 µg/ml imipenem dramatically reduced the CFU counts to near baseline levels of infection. This study's finding that there is synergy between certain ß-lactam combinations against M. abscessus infection provides optimism toward identifying an optimum dual ß-lactam treatment regimen.IMPORTANCE The emergence of chronic MABC infections among immunocompromised populations and their inherent and acquired resistance to effective antibiotic therapy have created clinical challenges in advancing patients for transplant surgery and treating those with disease. There is an urgent need for new treatment regimens, and the repurposing of existing antibiotics provides a rapid strategy to advance a laboratory finding to patient care. Our recent discoveries that dual ß-lactams, specifically the combination of ceftazidime with ceftaroline or ceftazidime with imipenem, have significant in vitro MIC values and kill curve activities and are effective against infected THP-1 human macrophages provide optimism for a dual ß-lactam treatment strategy against MABC infections. The unexpected synergistic activities reported in this study create a new path of discovery to repurpose the large family of ß-lactam drugs.

Tuberculosis disease among Mexico-born individuals living in New York City, 2001-2014.

SETTING: Tuberculosis (TB) has decreased substantially in New York City (NYC), but progress has slowed in recent years. Continued declines will require novel approaches tailored to foreign-born populations. OBJECTIVE: To describe TB epidemiology among the Mexico-born population of NYC to inform interventions in this community. DESIGN: The study included NYC patients with TB disease identified from 2001 to 2014. Incidence rates were compared by country of birth groupings. Demographic and patient characteristics were analyzed for all Mexico-born TB patients. Patients were compared by Mycobacterium bovis vs. non-M. bovis TB strain. Culture-confirmed patients were compared by genotype clustering status. RESULTS: From 2001 to 2014, 621 Mexico-born TB patients were identified in NYC. TB rates were significantly higher among Mexico-born vs. US-born persons every year. Mexico-born patients had lived in the United States for a median 7 years at diagnosis. The geographic distribution of Mexico-born TB patients was similar to that of the total Mexico-born population. Overall, 71% of patients reported previous employment; 52% of non-M. bovis patients were clustered based on genotyping results. CONCLUSIONS: Our results provide a foundation to inform future interventions in the Mexico-born population. Additional work is needed to explore possible local TB transmission and health care-seeking practices.

Exploring genotype concordance in epidemiologically linked cases of tuberculosis in New York City.

Comparing genotype results of tuberculosis (TB) isolates from individuals diagnosed with TB can support or refute transmission; however, these conclusions are based upon the criteria used to define a genotype match. We used a genotype-match definition which allowed for variation in IS6110 restriction fragment length polymorphism (RFLP) to support transmission between epidemiologically linked persons. Contacts of individuals with infectious TB (index cases) diagnosed in New York City from 1997 to 2003 who subsequently developed TB (contact cases) from 1997 to 2007 were identified. For each contact case and index case (case-pair), isolate genotypes (spoligotype and RFLP results) were evaluated. Isolates from case-pairs were classified as exact or non-exact genotype match. Genotypes from non-exact match case-pairs were reviewed at the genotyping laboratory to determine if the isolates met the near-genotype-match criteria (exactly matching spoligotype and similar RFLP banding patterns). Of 118 case-pairs identified, isolates from 83 (70%) had exactly matching genotypes and 14 (12%) had nearly matching genotypes (supporting transmission), while the remaining 21 (18%) case-pairs had discordant genotypes (refuting transmission). Using identical genotype-match criteria for isolates from case-pairs epidemiologically linked through contact investigation may lead to underestimation of transmission. TB programmes should consider the value of expanding genotype-match criteria to more accurately assess transmission between such cases.

Targeting Alpha Toxin and ClfA with a Multimechanistic Monoclonal-Antibody-Based Approach for Prophylaxis of Serious Staphylococcus aureus Disease.

UNLABELLED: Staphylococcus aureus produces numerous virulence factors, each contributing different mechanisms to bacterial pathogenesis in a spectrum of diseases. Alpha toxin (AT), a cytolytic pore-forming toxin, plays a key role in skin and soft tissue infections and pneumonia, and a human anti-AT monoclonal antibody (MAb), MEDI4893*, has been shown to reduce disease severity in dermonecrosis and pneumonia infection models. However, interstrain diversity and the complex pathogenesis of S. aureus bloodstream infections suggests that MEDI4893* alone may not provide adequate protection against S. aureus sepsis. Clumping factor A (ClfA), a fibrinogen binding protein, is an important virulence factor facilitating S. aureus bloodstream infections. Herein, we report on the identification of a high-affinity anti-ClfA MAb, 11H10, that inhibits ClfA binding to fibrinogen, prevents bacterial agglutination in human plasma, and promotes opsonophagocytic bacterial killing (OPK). 11H10 prophylaxis reduced disease severity in a mouse bacteremia model and was dependent on Fc effector function and OPK. Additionally, prophylaxis with 11H10 in combination with MEDI4893* provided enhanced strain coverage in this model and increased survival compared to that obtained with the individual MAbs. The MAb combination also reduced disease severity in murine dermonecrosis and pneumonia models, with activity similar to that of MEDI4893* alone. These results indicate that an MAb combination targeting multiple virulence factors provides benefit over a single MAb neutralizing one virulence mechanism by providing improved efficacy, broader strain coverage, and protection against multiple infection pathologies. IMPORTANCE: Alternative strategies to broad-spectrum antibiotics are required to combat the antibiotic resistance epidemic. Previous attempts at active or passive immunization against Staphylococcus aureus targeting single antigens have failed in clinical trials despite positive preclinical data. To provide broad disease and isolate coverage, an effective immunization strategy likely must target multiple virulence mechanisms of the pathogen. Herein, we tested a multimechanistic MAb combination targeting alpha toxin (AT) and clumping factor A (ClfA) that neutralizes AT-mediated cytotoxicity, blocks fibrinogen binding by ClfA, prevents bacterial agglutination, targets the bacteria for opsonophagocytic killing, and provides broad isolate coverage in a lethal-bacteremia model. Although each MAb alone was effective in bacteremia against some individual isolates, the MAb combination provided improved protection against other isolates. These results illustrate the importance of targeting multiple virulence mechanisms and highlight the potential for an MAb combination targeting AT and ClfA to effectively prevent S. aureus disease.

Molecular Characterization by Using Next-Generation Sequencing of Plasmids Containing blaNDM-7 in Enterobacteriaceae from Calgary, Canada.

Enterobacteriaceae with blaNDM-7 are relatively uncommon and had previously been described in Europe, India, the United States, and Japan. This study describes the characteristics of Enterobacteriaceae (Klebsiella pneumoniae [n = 2], Escherichia coli [n = 2], Serratia marcescens [n = 1], and Enterobacter hormaechei [n = 1] isolates) with blaNDM-7 obtained from 4 patients from Calgary, Canada, from 2013 to 2014. The 46,161-bp IncX3 plasmids with blaNDM-7 are highly similar to other blaNDM-harboring IncX3 plasmids and, interestingly, showed identical structures within the different isolates. This finding may indicate horizontal transmission within our health region, or it may indicate contact with individuals from areas of endemicity within the hospital setting. Patients infected or colonized with bacteria containing blaNDM-7 IncX3 plasmids generate infection control challenges. Epidemiological and molecular studies are required to better understand the dynamics of transmission, the risk factors, and the reservoirs for bacteria harboring blaNDM-7. To the best of our knowledge, this is the first report of S. marcescens and E. hormaechei with blaNDM-7.

Acquisition of second-line drug resistance and extensive drug resistance during recent transmission of Mycobacterium tuberculosis in rural China.

Multidrug-resistant tuberculosis (MDR-TB) is prevalent in countries with a high TB burden, like China. As little is known about the emergence and spread of second-line drug (SLD) -resistant TB, we investigate the emergence and transmission of SLD-resistant Mycobacterium tuberculosis in rural China. In a multi-centre population-based study, we described the bacterial population structure and the transmission characteristics of SLD-resistant TB using Spoligotyping in combination with genotyping based on 24-locus MIRU-VNTR (mycobacterial interspersed repetitive unit-variable-number tandem repeat) plus four highly variable loci for the Beijing family, in four rural Chinese regions with diverse geographic and socio-demographic characteristics. Transmission networks among genotypically clustered patients were constructed using social network analysis. Of 1332 M. tuberculosis patient isolates recovered, the Beijing family represented 74.8% of all isolates and an association with MDR and simultaneous resistance between first-line drugs and SLDs. The genotyping analysis revealed that 189 isolates shared MIRU-VNTR patterns in 78 clusters with clustering rate and recent transmission rate of 14.2% and 8.3%, respectively. Fifty-three SLD-resistant isolates were observed in 31 clusters, 30 of which contained the strains with different drug susceptibility profiles and genetic mutations. In conjunction with molecular data, socio-network analysis indicated a key role of Central Township in the transmission across a highly interconnected network where SLD resistance accumulation occurred during transmission. SLD-resistant M. tuberculosis has been spreading in rural China with Beijing family being the dominant strains. Primary transmission of SLD-resistant strains in the population highlights the importance of routine drug susceptibility testing and effective anti-tuberculosis regimens for drug-resistant TB.

Epidemiology and molecular characterization of bacteremia due to carbapenem-resistant Klebsiella pneumoniae in transplant recipients.

We conducted a retrospective study of 17 transplant recipients with carbapenem-resistant Klebsiella pneumoniae bacteremia, and described epidemiology, clinical characteristics and strain genotypes. Eighty-eight percent (15/17) of patients were liver or intestinal transplant recipients. Outcomes were death due to septic shock (18%), cure (24%) and persistent (>7 days) or recurrent bacteremia (29% each). Thirty- and 90-day mortality was 18% and 47%, respectively. Patients who were cured received at least one active antimicrobial agent and underwent source control interventions. Forty-one percent (7/17) of patients had intra-abdominal infections; all except one developed persistent/recurrent bacteremia despite drainage. Two patients tolerated persistent bacteremia for >300 days. All patients except one were infected with sequence type 258 (ST258), K. pneumoniae carbapenemase (KPC)-2-producing strains harboring a mutant ompK35 porin gene; the exception was infected with an ST37, KPC-3-producing strain. Seventy-one percent (12/17) of patients were infected with ST258 ompK36 mutant strains. In two patients, persistent bacteremia was caused by two strains with different ompK36 genotypes. Three ompK36 mutations were associated with significantly higher carbapenem minimum inhibitory concentrations than wild-type ompK36. Pulse-field gel electrophoresis identified a single ST258 lineage; serial strains from individual patients were indistinguishable. In conclusion, KPC-K. pneumoniae bacteremia exhibited highly diverse clinical courses following transplantation, and was caused by clonal ST258 strains with different ompK36 genotypes.

Growth-inhibitory activity of natural and synthetic isothiocyanates against representative human microbial pathogens.

AIMS: The aim of this study was to test the growth inhibition activity of isothiocyanates (ITCs), defence compounds of plants, against common human microbial pathogens. METHODS AND RESULTS: In this study, we have tested the growth-inhibitory activity of a diverse collection of new and previously known representative ITCs of various structural classes against pathogenic bacteria, fungi and moulds by a serial dilution method. Generally, the compounds were more active against Gram-positive bacteria and fungi exhibiting species-specific bacteriostatic or bactericidal effect. The most active compounds inhibited the growth of both drug-susceptible and multi-drug-resistant (MDR) pathogens at micromolar concentrations. In the case of Mycobacterium tuberculosis, some compounds were more active against MDR, rather than against susceptible strains. The average antimicrobial activity for some of the new derivatives was significantly higher than that previously reported for the most active ITC compounds. The structure-activity relationship (SAR) established for various classes of ITC with Bacillus cereus (model organism for B. anthracis) followed a distinct pattern, thereby enabling prediction of new more efficient inhibitors. Remarkably, tested bacteria failed to develop resistance to ITC. While effectively inhibiting microbial growth, ITCs displayed moderate toxicity towards eukaryotic cells. CONCLUSIONS: High antimicrobial activity coupled with moderate toxicity grants further thorough studies of the ITC compounds aimed at elucidation of their cellular targets and inhibitory mechanism. SIGNIFICANCE AND IMPACT OF THE STUDY: This systematic study identified new ITC compounds highly active against common human microbial pathogens at the concentrations comparable with those for currently used antimicrobial drugs (e.g. rifampicin and fluconazole). Tested representative pathogens do not develop resistance to the inhibitors. These properties justify further evaluation of ITC compounds as potential antimicrobial agents for medicinal use and for industrial applications.

Infertility, in vitro fertilization and congenital tuberculosis.

Congenital tuberculosis (CTB) due to maternal genitourinary (GU) TB infection is a rare occurrence, as infection of the genital tract in women generally leads to infertility. Increasing availability of assisted reproductive technology creates the potential for CTB to emerge as a significant problem. We describe five infants (two sets of twins and a singleton birth) conceived by in vitro fertilization who developed CTB. All five infants were born to mothers who had immigrated to the United States from India and none had GU TB diagnosed before the birth of their infected infants.

Retreatment tuberculosis in a South African community: the role of re-infection, HIV and antiretroviral treatment.

BACKGROUND: Limited data exist on the impact of human immunodeficiency virus (HIV) or antiretroviral treatment (ART) on retreatment tuberculosis (TB). METHODS: Retreatment TB episodes between 2001 and 2010 in a high HIV and TB burden community were linked to first-episode treatment outcomes, HIV status and ART use. Genotypic analysis of Mycobacterium tuberculosis isolates distinguished re-infection from reactivation TB. RESULTS: A total of 2027 TB episodes occurred in 1755 adults: 564 were retreatment cases. New patients who interrupted or failed initial treatment, were HIV-positive or were not on ART more frequently developed retreatment TB (respectively P < 0.001, P = 0.01 and P = 0.02). Time intervals between successive diagnoses were shorter in patients who interrupted/failed treatment compared to those with favourable initial treatment outcomes (P < 0.001), but did not vary by HIV status or ART use. Genotypic data were available for 40 successive diagnoses, of which 19 had matching M. tuberculosis strains. Matching strains were associated with HIV-negative status (P < 0.001), treatment interruption/failure (P = 0.04) and shorter intervals between diagnoses (P = 0.02). HIV-positive patients and patients on ART were more likely to have non-matched strains (P = 0.01 and P = 0.03). CONCLUSION: Among HIV-negative patients, retreatment TB was predominantly due to reactivation following poor initial treatment outcomes. In HIV-positive patients re-infection TB was more common, particularly among those on ART.

Recent transmission of W-Beijing family Mycobacterium tuberculosis in rural eastern China.

OBJECTIVE: To understand the degree of recent transmission of tuberculosis (TB) and determine the risk factors associated with recent transmission stratified by W-Beijing genotype in rural China. DESIGN: A cross-sectional study of bacteriologically confirmed TB patients registered in two rural counties of eastern China over a 1-year period. RESULTS: Of 351 patient isolates, spoligotyping identified 243 (69.2%) as W-Beijing family strains, and 53 (15.1%) and 15 (4.3%) as members of T1 Family and Family 33, respectively. Insertion sequence (IS) 6110 based restriction fragment length polymorphism typing revealed that 31 clusters together accounted for 80 of the 351 isolates. Strains with the W-Beijing genotype were more likely to be clustered than non-Beijing strains (42.3% vs. 8.3%, P < 0.001). The proportion of cases due to recent transmission was estimated at 23.1% (32.1% W-Beijing genotype vs. 2.8% non-W-Beijing genotype). Multivariate analysis showed that bacille Calmette-Guérin (BCG) vaccination (aOR 2.97), multidrug resistance (aOR 5.45) and body mass index (aOR 1.13) were independent predictors for clustering among W-Beijing isolates. CONCLUSIONS: The low clustering proportions highlight the role of endogenous reactivation of TB as a main concern in rural eastern China. Our findings also suggest that W-Beijing strains were associated with recent transmission in this population, where multidrug resistance and BCG vaccination may play an important role in the mechanism of TB transmission.

Disseminated tuberculosis in human immunodeficiency virus infection: ineffective immunity, polyclonal disease and high mortality.

BACKGROUND: Disseminated tuberculosis (TB) is a major cause of death in patients with the acquired immune-deficiency syndrome (AIDS), but its pathogenesis and clinical features have not been defined prospectively. METHODS: Human immunodeficiency virus (HIV) infected adults with a CD4 count ≥ 200 cells/µl and bacille Calmette-Guérin scar underwent immunologic evaluation and subsequent follow-up. RESULTS: Among 20 subjects who developed disseminated TB, baseline tuberculin skin tests were ≥15 mm in 14 (70%) and lymphocyte proliferative responses to Mycobacterium tuberculosis were positive in 14 (70%). At the time of diagnosis, fever ≥2 weeks plus ≥5 kg weight loss was reported in 16 (80%) patients, abnormal chest X-rays in 7/17 (41%), and positive sputum cultures in 10 (50%); median CD4 count was 30 cells/µl (range 1-122). By insertion sequence (IS) 6110 analysis, 14 (70%) blood isolates were clustered and 3/8 (37%) concurrent sputum isolates represented a different strain (polyclonal disease). Empiric TB treatment was given to eight (40%) patients; 11 (55%) died within a month. CONCLUSIONS: Disseminated TB in HIV occurs with cellular immune responses indicating prior mycobacterial infection, and IS6110 analysis suggests an often lethal combination of reactivation and newly acquired infection. Control will require effective prevention of both remotely and recently acquired infection, and wider use of empiric therapy in patients with advanced AIDS and prolonged fever.

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.

[Analysis of chromosome deletions of TbDl, RD6 and pks15/1 in clinical strains of Mycobacterium tuberculosis].

Deletions are very important sources of the variability among members of the mycobacterial tuberculosis complex (MTC). Deletion analysis of MTC clinical isolates was performed to clarify phylogenetic relationships and help to identify epidemiologically significant groups of the MTC. In this study, the variability of the TbDl, RD6 and pks15/1 chromosome loci in clinical MTC strains and comparison of those results with IS6110-RFLP (restriction fragment length polymorphism), sSNP (synonymous single nucleotide polymorphism), PGG (Principal Genetic Group) typing data were used to determine if these chromosome regions constitute good molecular markers for some of the epidemiologically important groups of the MTC. In the present study, 122, 61 and 294 clinical isolates were tested for the TbDl, RD6 and pks15/1 deletions, respectively. Specific probes were designed and used in RFLP analysis as well as sequencing techniques were applied. We found that all strains with intact TbDl region belonged to the sSNP cluster I, PGG 1 (katG463Leu and gyrA95Thr). The RD6 deletion was not determined to be a strict characteristic feature of any specific genetic group of the tested M.tb strains, but presence of this deletion is presumed for strains of high virulence, and associated with principal genetic groups 2 or 3. The genetic event that led to this deletion likely occurred in the strain that belongs to PGG 1. Identification of strains with an intact pksl5/1 gene cluster provided a potential marker for virulence. An intact pks15/1 gene cluster is required for the biosynthesis of the phenolic glycolipids (PGL-tb), production of which by clinical isolates was correlated with virulence.

Suspected transmission of methicillin-resistant Staphylococcus aureus between domestic pets and humans in veterinary clinics and in the household.

OBJECTIVE: To describe MRSA infection and colonization in household pets, and transmission of MRSA between animals and humans. METHODS: MRSA infection and colonization in household pets and human contacts were evaluated during investigations initiated after identification of MRSA infection or colonization of a household pet in order to determine if there had been transmission between animals and humans. All MRSA isolates were screened for Panton-Valentine leukocidin (PVL) genes by use of polymerase chain reaction, and isolate relatedness was determined by use of pulsed-field gel electrophoresis (PFGE). RESULTS: Investigations of six situations where MRSA was identified in one or more animals in a household or veterinary facility were performed. MRSA was isolated from 8 animals (5 dogs and 3 cats) with clinical infections, 1 cat that was in contact with 2 infected cats and 14/88 (16%) of household contacts or veterinary personnel. Both animal-to-human and human-to-animal transmission were suspected. An indistinguishable MRSA isolate was recovered from at least one human that was in contact with each animal case. All isolates were classified as Canadian epidemic MRSA-2, the predominant community-associated MRSA clone in humans in Canada. No isolates possessed genes encoding for the PVL. CONCLUSIONS: Transmission of MRSA between humans and animals, in both directions, was suspected. MRSA appears to be an emerging veterinary and zoonotic pathogen.

An outbreak of methicillin-resistant Staphylococcus aureus skin infections resulting from horse to human transmission in a veterinary hospital.

There are increasing reports of methicillin-resistant Staphylococcus aureus (MRSA) infection and colonization in horses and evidence that MRSA can be transmitted between horses and humans. The objective of this study was to investigate reports of skin infection in personnel working with a foal with community-associated MRSA colonization and subsequent infection. Clinical diagnostic specimens were collected from individuals reporting skin lesions following contact with the affected foal. Nasal and groin screening swabs were collected from other veterinary personnel that attended a voluntary screening clinic. MRSA skin infections were identified in three neonatal intensive care unit personnel. Nasal colonization was subsequently identified in 10/103 (9.7%) other veterinary hospital personnel. Isolates were indistinguishable by pulsed field gel electrophoresis, classified as Canadian epidemic MRSA-5, possessed SCCmecIV, were negative for the Panton-Valentine leukocidin and were multidrug resistant. Transmission to veterinary personnel despite short-term contact with standard protective barriers highlights the potential importance of MRSA as an emerging zoonotic pathogen, and indicates that further evaluation of interspecies transmission of MRSA and means to prevent zoonotic infection are required.

Transmission trends for human immunodeficiency virus associated tuberculosis in New York City.

SETTING: Since 1992, tuberculosis (TB) control measures have reduced incidence rates in New York City and elsewhere. Nevertheless, trends have not been uniform in all demographic groups. OBJECTIVE: To characterize the epidemiology of human immunodeficiency virus (HIV) associated TB in New York during the 1990s, we analyzed social, demographic and clinical characteristics and genetic data on Mycobacterium tuberculosis isolates among persons with known HIV-status. DESIGN: A retrospective case-control study to compare patients with HIV-associated TB and patients with TB alone. RESULTS: Of 546 patients (70.5%) in the Department of Health Tuberculosis Control Registry treated for TB, 385 also had documented HIV status; 198 were HIV-infected (51%) and 187 (49%) were not. Genotype analysis of the 385 M. tuberculosis isolates identified 200 (52%) clustered strains, representing recent transmission. Although the overall percentage of TB cases associated with restriction fragment length polymorphism (RFLP) clustering fell over the period studied, HIV-associated cases were still much more likely to be associated with clustering than non-HIV-associated cases. CONCLUSIONS: Continued attention is required to contain the spread of TB in this vulnerable population.