Archive for September, 2013

Genetic Characterization of Legionella pneumophila Isolated from a Common Watershed in Comunidad Valenciana, Spain.

PLoS One. 2013 Apr 25;8(4):e61564.

Sánchez-Busó L, Coscollá M, Pinto-Carbó M, Catalán V, González-Candelas F.

Source

Genomics and Health Joint Unit CSISP, FISABIO-University of Valencia/Cavanilles Institute, Valencia, Spain.

Abstract

Legionella pneumophila infects humans to produce legionellosis and Pontiac fever only from environmental sources. In order to establish control measures and study the sources of outbreaks it is essential to know extent and distribution of strain variants of this bacterium in the environment. Sporadic and outbreak-related cases of legionellosis have been historically frequent in the Comunidad Valenciana region (CV, Spain), with a high prevalence in its Southeastern-most part (BV). Environmental investigations for the detection of Legionella pneumophila are performed in this area routinely. We present a population genetics study of 87 L. pneumophila strains isolated in 13 different localities of the BV area irrigated from the same watershed and compare them to a dataset of 46 strains isolated in different points of the whole CV. Our goal was to compare environmental genetic variation at two different geographic scales, at county and regional levels. Genetic diversity, recombination and population structure were analyzed with Sequence-Based Typing data and three intergenic regions. The results obtained reveal a low, but detectable, level of genetic differentiation between both datasets, mainly, but not only, attributed to the occurrence of unusual variants of the neuA locus present in the BV populations. This differentiation is still detectable when the 10 loci considered are analyzed independently, despite the relatively high incidence of the most common genetic variant in this species, sequence type 1 (ST-1). However, when the genetic data are considered without their associated geographic information, four major groups could be inferred at the genetic level which did not show any correlation with sampling locations. The overall results indicate that the population structure of these environmental samples results from the joint action of a global, widespread ST-1 along with genetic differentiation at shorter geographic distances, which in this case are related to the common watershed for the BV localities.

PDF

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3636276/pdf/pone.0061564.pdf

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September 30, 2013 at 8:33 am

Setting and Revising Antibacterial Susceptibility Breakpoints

Clin. Microbiol. Rev. July 2007 V.20  N.3 P.391-408

John Turnidge1,* and David L. Paterson2,3,4

1Division of Laboratory Medicine, Women’s and Children’s Hospital, North Adelaide, Australia

2Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania

3University of Queensland, Brisbane, Australia

4Queensland Health Pathology Services, Royal Brisbane and Women’s Hospital, Brisbane, Australia

SUMMARY

Clinical microbiology laboratories need to communicate results of antibacterial susceptibility testing to prescribers. Sophisticated prescribers who are knowledgeable of the pharmacokinetics and pharmacodynamics of antibacterials may desire no more information than the MIC of the drug in question. However, most prescribers require interpretation of antibacterial susceptibility testing results. Breakpoints can assist in determining if an antibacterial is potentially useful in the treatment of a bacterial infection. Breakpoints should be set prior to an antibacterial being used clinically. Breakpoint setting requires integration of knowledge of the wild-type distribution of MICs, assessment of the pharmacokinetics/pharmacodynamics of the antibacterial, and study of the clinical outcome of infections when the antibacterial is used. It is mandatory that breakpoints be reviewed when antibacterial agents have been in clinical use for some time, particularly if mechanisms of bacterial resistance to the drug have been described. In general, greater amounts of information on the pharmacokinetics and pharmacodynamics of an antibacterial are available when breakpoints need to be revised. However, the opportunity to conduct randomized clinical studies of an antibacterial declines after the drug has been released commercially. Well-designed observational clinical studies are therefore necessary in order to provide reliable data to inform those reevaluating breakpoints. Breakpoint-setting organizations may also play a role in developing phenotypic tests for detection of resistance mechanisms, as this information may complement use of the breakpoint in some circumstances.

PDF

http://cmr.asm.org/content/20/3/391.full.pdf+html

 

September 30, 2013 at 8:30 am

Legionnaires’ disease case-finding algorithm, attack rates, and risk factors during a residential outbreak among older adults: an environmental and cohort study.

BMC Infect Dis. 2013 Jun 27;13(1):291.

Silk BJ, Foltz JL, Ngamsnga K, Brown E, Muñoz MG, Hampton L, Jacobs-Slifka K, Kozak NA, Underwood JM, Krick J, Travis T, Farrow O, Fields BS, Blythe D, Hicks LA.

Abstract

BACKGROUND:

During a Legionnaires’ disease (LD) outbreak, combined epidemiological and environmental investigations were conducted to identify prevention recommendations for facilities where elderly residents live independently but have an increased risk of legionellosis.

METHODS:

Survey responses (n = 143) were used to calculate attack rates and describe transmission routes by estimating relative risk (RR) and 95% confidence intervals (95% CI). Potable water collected from five apartments of LD patients and three randomly-selected apartments of residents without LD (n = 103 samples) was cultured for Legionella.

RESULTS:

Eight confirmed LD cases occurred among 171 residents (attack rate = 4.7%); two visitors also developed LD. One case was fatal. The average age of patients was 70 years (range: 62–77). LD risk was lower among residents who reported tub bathing instead of showering (RR = 0.13, 95% CI: 0.02–1.09, P = 0.03). Two respiratory cultures were characterized as L. pneumophila serogroup 1, monoclonal antibody type Knoxville (1,2,3), sequence type 222. An indistinguishable strain was detected in 31 (74%) of 42 potable water samples.

CONCLUSIONS:

Managers of elderly-housing facilities and local public health officials should consider developing a Legionella prevention plan. When Legionella colonization of potable water is detected in these facilities, remediation is indicated to protect residents at higher risk. If LD occurs among residents, exposure reduction, heightened awareness, and clinical surveillance activities should be coordinated among stakeholders. For prompt diagnosis and effective treatment, clinicians should recognize the increased risk and atypical presentation of LD in older adults.

PDF

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3700825/pdf/1471-2334-13-291.pdf

September 29, 2013 at 10:55 pm

Concepts in Immunology and Diagnosis of Hydatid Disease

Clin. Microbiol. Rev. January 2003 16:18-36

Wenbao Zhang1,2, Jun Li1 and Donald P. McManus1,*

1Molecular Parasitology Laboratory, Australian Centre for International and Tropical Health and Nutrition, The Queensland Institute of Medical Research and The University of Queensland, Brisbane, Queensland 4029, Australia

2Veterinary Research Institute, Xinjiang Academy of Animal Science, Urumqi, Xinjiang 830000, People’s Republic of China

SUMMARY

Echinococcosis is a cosmopolitan zoonosis caused by adult or larval stages of cestodes belonging to the genus Echinococcus (family Taeniidae). The two major species of medical and public health importance are Echinococcus granulosus and E. multilocularis, which cause cystic echinococcosis (CE) and alveolar echinococcosis (AE), respectively. Both CE and AE are both serious diseases, the latter especially so, with a high fatality rate and poor prognosis if managed inappropriately. This review discusses new concepts and approaches in the immunology and diagnosis of CE, but comparative reference has also been made to AE infection and to earlier pivotal studies of both diseases. The review considers immunity to infection in the intermediate and definitive hosts, innate resistance, evasion of the immune system, and vaccination of intermediate and definitive hosts, and it particularly emphasizes procedures for diagnosis of CE and AE, including the value of immunodiagnostic approaches. There is also discussion of the new advances in recombinant and related DNA technologies, especially application of PCR, that are providing powerful tools in the fields of vaccinology and molecular diagnosis of echinococcosis.

PDF

http://cmr.asm.org/content/16/1/18.full.pdf+html

September 29, 2013 at 10:50 pm

Pneumococcal Vaccination and Revaccination of Older Adults

Clinical Microbiology Review April 2003  V.16  N.2 P.308-318

Andrew S. Artz1,2,*, William B. Ershler1 and Dan L. Longo3

1The Institute for Advanced Studies in Aging and Geriatric Medicine, Washington, D.C.

2The University of Chicago Hospitals, Chicago, Illinois

3National Institute on Aging, Baltimore, Maryland

SUMMARY

As individuals advance in age, the risk of infection, bacteremia, and mortality caused by Streptococcus pneumoniae rises. Retrospective data demonstrate that the licensed penumococcal polysaccharide vaccine (PPV) is effective in older persons in reducing serotype-specific invasive disease. PPV demonstrates good immunogenicity in older adults, generally comparable to that in younger subjects, although certain cohorts respond less well. The response to PPV is T cell independent, however, and does not elicit immunologic memory. The duration of the anti-capsular polysaccharide antibody response appears to wane as early as 3 years after vaccination. In older persons, revaccination induces an antibody response, although it may not be as strong as that from the initial vaccine. While revaccination of older adults has been recommended, clinical efficacy has not yet been proven. Measures of antibody function may be at least as important in determining protection as are quantitative antibody levels. Additional studies of immunogenicity, particularly regarding revaccination, will facilitate the design of an optimal pneumococcal vaccination policy. Research into conjugate- and protein-based pneumococcal vaccines, which elicit T-cell-dependent responses and induce immunologic memory, is needed in older persons. In the meantime, administering to PPV to recommended groups should be a public health priority.

PDF

http://cmr.asm.org/content/16/2/308.full.pdf+html

September 29, 2013 at 2:00 pm

Human Papillomavirus and Cervical Cancer

Clinical Microbiology Review January 2003 V.16 N.1 P.1-17

Eileen M. Burd*

Henry Ford Hospital, Detroit, Michigan

SUMMARY

Of the many types of human papillomavirus (HPV), more than 30 infect the genital tract. The association between certain oncogenic (high-risk) strains of HPV and cervical cancer is well established. Although HPV is essential to the transformation of cervical epithelial cells, it is not sufficient, and a variety of cofactors and molecular events influence whether cervical cancer will develop. Early detection and treatment of precancerous lesions can prevent progression to cervical cancer. Identification of precancerous lesions has been primarily by cytologic screening of cervical cells. Cellular abnormalities, however, may be missed or may not be sufficiently distinct, and a portion of patients with borderline or mildly dyskaryotic cytomorphology will have higher-grade disease identified by subsequent colposcopy and biopsy. Sensitive and specific molecular techniques that detect HPV DNA and distinguish high-risk HPV types from low-risk HPV types have been introduced as an adjunct to cytology. Earlier detection of high-risk HPV types may improve triage, treatment, and follow-up in infected patients. Currently, the clearest role for HPV DNA testing is to improve diagnostic accuracy and limit unnecessary colposcopy in patients with borderline or mildly abnormal cytologic test results.

PDF

http://cmr.asm.org/content/16/1/1.full.pdf+html

September 29, 2013 at 1:59 pm

Comparative Genomics Reveal That Host-Innate Immune Responses Influence the Clinical Prevalence of Legionella pneumophila Serogroups.

PLoS One. 2013 Jun 27;8(6):e67298.

Khan MA, Knox N, Prashar A, Alexander D, Abdel-Nour M, Duncan C, Tang P, Amatullah H, Dos Santos CC, Tijet N, Low DE, Pourcel C, Van Domselaar G, Terebiznik M, Ensminger AW, Guyard C.

Source

Public Health Ontario, Toronto, Ontario, Canada ; Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.

Abstract

Legionella pneumophila is the primary etiologic agent of legionellosis, a potentially fatal respiratory illness. Amongst the sixteen described L. pneumophila serogroups, a majority of the clinical infections diagnosed using standard methods are serogroup 1 (Sg1). This high clinical prevalence of Sg1 is hypothesized to be linked to environmental specific advantages and/or to increased virulence of strains belonging to Sg1. The genetic determinants for this prevalence remain unknown primarily due to the limited genomic information available for non-Sg1 clinical strains. Through a systematic attempt to culture Legionella from patient respiratory samples, we have previously reported that 34% of all culture confirmed legionellosis cases in Ontario (n = 351) are caused by non-Sg1 Legionella. Phylogenetic analysis combining multiple-locus variable number tandem repeat analysis and sequence based typing profiles of all non-Sg1 identified that L. pneumophila clinical strains (n = 73) belonging to the two most prevalent molecular types were Sg6. We conducted whole genome sequencing of two strains representative of these sequence types and one distant neighbour. Comparative genomics of the three L. pneumophila Sg6 genomes reported here with published L. pneumophila serogroup 1 genomes identified genetic differences in the O-antigen biosynthetic cluster. Comparative optical mapping analysis between Sg6 and Sg1 further corroborated this finding. We confirmed an altered O-antigen profile of Sg6, and tested its possible effects on growth and replication in in vitro biological models and experimental murine infections. Our data indicates that while clinical Sg1 might not be better suited than Sg6 in colonizing environmental niches, increased bloodstream dissemination through resistance to the alternative pathway of complement mediated killing in the human host may explain its higher prevalence.

PDF

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3694923/pdf/pone.0067298.pdf

September 29, 2013 at 1:56 pm

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