Molecular markers demonstrate that the first described multidrug-resistant Mycobacterium bovis outbreak was due to Mycobacterium tuberculosis.
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We genetically characterized multidrug-resistant Mycobacterium tuberculosis complex strains which caused a nosocomial outbreak of tuberculosis affecting six human immunodeficiency virus (HIV)-positive patients and one HIV-negative staff member (E. Bouvet, E. Casalino, G. Mendoza-Sassi, S. Lariven, E. Vallee, M. Pernet, S. Gottot, and F. Vachon, AIDS 7:1453-1460, 1993). The strains showed all the phenotypic characteristics of Mycobacterium bovis. They presented a high copy number of IS6110, the spacers 40 to 43 in the direct repeat locus, and the mtp40 fragment. They lacked the G-A mutation at position 285 in the oxyR gene and the C-G mutation at position 169 in the pncA gene. These genetic characteristics revealed that these were dysgonic, slow-growing M. tuberculosis strains mimicking the M. bovis phenotype, probably as a consequence of cellular alterations associated with the multidrug resistance. Spoligotyping and IS6110 restriction fragment length polymorphism (RFLP) analysis confirmed that the outbreak was due to a single strain. However, the IS6110 RFLP pattern of the strain isolated from the last patient, diagnosed three years after the index case, differed slightly from the patterns of the other six strains. A model of a possible genetic event is presented to explain this divergence. This study stresses the value of using several independent molecular markers to identify multidrug-resistant tubercle bacilli. (+info)
DNA banding pattern polymorphism in vancomycin-resistant Enterococcus faecium and criteria for defining strains.
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The degree of DNA banding pattern polymorphism exhibited by vancomycin-resistant Enterococcus faecium (VREM) strains isolated on a renal unit over an 11-month period was investigated. Thirty VREM strains from different patients were analyzed by pulsed-field gel electrophoresis (PFGE; with extended run and optimal pulse times), ribotyping, plasmid profile analysis, biotyping, pyrolysis mass spectrometry, and antibiogram analysis. PFGE resolved 17 banding patterns which formed four distinct clusters at the 82% similarity level. Intercluster band differences ranged from 14 to 31 bands. The strains in one cluster, which contained seven patterns that differed from each other by one to seven bands and from the common pattern by five bands, were confirmed to be a single strain by four of the five other typing methods. The strains in a second cluster with eight patterns, which differed from each other by 1 to 12 bands, contained two subclusters. This subdivision was supported by ribotyping and biotyping. However, it was unclear whether these subclusters represented distinct strains. In one strain, marked polymorphism (patterns that differed from each other by up to four bands) was observed in the ribotype pattern. This study demonstrates the high degree of DNA banding pattern polymorphism found for some strains of VREM and illustrates the complexity involved in defining such strains. (+info)
Evidence for nasal carriage of methicillin-resistant staphylococci colonizing intravascular devices.
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Nasal surveillance cultures were performed for 54 patients exhibiting >/=10(3) CFU of methicillin-resistant coagulase-negative staphylococci per ml in central venous catheter (CVC) rinse cultures over a 6-month period. Forty-two of the nasal cultures yielded growth of methicillin-resistant coagulase-negative staphylococci, and 33 of the 42 cultures contained organisms that belonged to the same species as the CVC isolates. Of the 33 same-species isolates, 20 appeared to be identical strains by pulsed-field gel electrophoresis analysis. These data suggest that measures should be taken to reduce cross-contamination between the respiratory tract and intravascular devices. However, the potential interest in detecting methicillin-resistant coagulase-negative staphylococcus carriage in high-risk patients is hampered by the lack of sensitivity of nasal surveillance cultures. (+info)
Nosocomial group A streptococcal infections associated with asymptomatic health-care workers--Maryland and California, 1997.
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Group A Streptococcus (GAS), a common cause of pharyngitis and uncomplicated skin and soft tissue infections, can cause serious invasive infections (including necrotizing fasciitis and streptococcal toxic-shock syndrome [STSS]) and death. Since 1965, at least 15 postoperative or postpartum GAS outbreaks attributed to asymptomatic carriage in health-care workers (HCWs) have been reported. This report describes two nosocomial outbreaks of GAS infection in Maryland and California during 1996-1997; the findings suggest that early infection-control measures that include active surveillance may interrupt transmission and prevent morbidity and mortality. (+info)
Candidemia at selected Canadian sites: results from the Fungal Disease Registry, 1992-1994. Fungal Disease Registry of the Canadian Infectious Disease Society.
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BACKGROUND: Candida species are important bloodstream pathogens that are being isolated with increasing frequency. Despite the availability of effective antifungal therapy, the mortality rate associated with Candida infection remains high. With the objective of describing the epidemiology of candidemia, the Canadian Infectious Disease Society conducted a study of candidemia in Canada. METHODS: Fourteen medical centres across Canada identified all patients with candidemia from March 1992 to February 1994 through blood culture surveillance for Candida spp. Patient-related data for invasive fungal infection were compiled retrospectively by chart review using a standardized data-recording form developed for the Fungal Disease Registry of the Canadian Infectious Disease Society. Cases of Candidemia were studied in relation to underlying medical conditions, predisposing factors, concurrent infection, antimicrobial agents, antifungal treatment and deaths. RESULTS: In total, 415 cases of candidemia were identified, 48 (11.6%) in children and 367 (88.4%) in adults. The causative pathogens were C. albicans in 286 cases (68.9%), C. parapsilosis in 43 (10.4%), C. glabrata in 34 (8.2%), C. tropicalis in 27 (6.5%) and other Candida species in 18 (4.3%); polymicrobial candidemia occurred in 7 cases (1.7%). The overall mortality rate was 46%, and the rate of deaths clinically related to candidemia was 19%. However, only 13 (27%) of the children died. A univariate analysis indicated that significant risk factors for death were age greater than 60 years, therapy for concomitant bacterial infection, stay in an intensive care unit, concurrent malignant disease, cytotoxic chemotherapy and granulocytopenia, although only age and stay in an intensive care unit emerged as significant risk factors in the multivariate analysis. After adjustment for other predictors of death, only infection with C. parapsilosis was associated with a lower mortality rate than infection with C. albicans. Treatment was given in 352 (84.8%) of cases. Amphotericin B was the preferred agent in 244 cases (69.3% of those treated); fluconazole was used in 101 cases (28.7%) and ketoconazole in 5 cases (1.4%). INTERPRETATION: Candidemia in Canada is caused predominantly by C. albicans. The mortality rate associated with candidemia is high, but it varies with the species of Candida and is lower in children than in adults. Age greater than 60 years and stay in an intensive care unit were the most significant risk factors for overall mortality. (+info)
The economic impact of Staphylococcus aureus infection in New York City hospitals.
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We modeled estimates of the incidence, deaths, and direct medical costs of Staphylococcus aureus infections in hospitalized patients in the New York City metropolitan area in 1995 by using hospital discharge data collected by the New York State Department of Health and standard sources for the costs of health care. We also examined the relative impact of methicillin-resistant versus -sensitive strains of S. aureus and of community-acquired versus nosocomial infections. S. aureus-associated hospitalizations resulted in approximately twice the length of stay, deaths, and medical costs of typical hospitalizations; methicillin-resistant and -sensitive infections had similar direct medical costs, but resistant infections caused more deaths (21% versus 8%). Community-acquired and nosocomial infections had similar death rates, but community-acquired infections appeared to have increased direct medical costs per patient ($35,300 versus $28,800). The results of our study indicate that reducing the incidence of methicillin-resistant and -sensitive nosocomial infections would reduce the societal costs of S. aureus infection. (+info)
Proficiency of clinical laboratories in and near Monterrey, Mexico, to detect vancomycin-resistant enterococci.
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Early detection of vancomycin-resistant enterococci is important for preventing its spread among hospitalized patients. We surveyed the ability of eight hospital laboratories in and near Monterrey, Mexico, to detect vancomycin resistance in Enterococcus spp. and found that although laboratories can reliably detect high-level vancomycin resistance, many have difficulty detecting low-level resistance. (+info)
Why do antimicrobial agents become ineffectual?
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Antibiotic resistance has evolved over the past 50 years from a merely microbiological curiosity to a serious medical problem in hospitals all over the world. Resistance has been reported in almost all species of gram-positive and -negative bacteria to various classes of antibiotics including recently developed ones. Bacteria acquire resistance by reducing permeability and intracellular accumulation, by alteration of targets of antibiotic action, and by enzymatic modification of antibiotics. Inappropriate use of an antibiotic selects resistant strains much more frequently. Once resistant bacteria has emerged, the resistance can be transferred to other bacteria by various mechanisms, resulting in multiresistant strains. MRSA is one of the typical multiresistant nosocomial pathogens. A study of the PFGE pattern of endonuclease-digested chromosomal DNA showed that MRSA of a few clones were disseminated among newborns in the NICU of a Japanese hospital. In this regard, it is important to choose appropriate antibiotics and then after some time, to change to other classes to reduce the selection of resistant strains. Since the development of epoch-making new antibiotics is not expected in the near future, it has become very important to use existing antibiotics prudently based on mechanisms of antibiotic action and bacterial resistance. Control of nosocomial infection is also very important to reduce further spread of resistant bacteria. (+info)