Infectious disease emergencies

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Molecular diagnostics in tuberculosis

Molecular diagnostics in tuberculosis has enabled rapid detection of Mycobacterium tuberculosis complex in clinical specimens, identification of mycobacterial species, detection of drug resistance, and typing for epidemiological investigation. In the laboratory diagnosis of tuberculosis, the nucleic acid amplification (NAA) test is rapid and specific but not as sensitive as culture of mycobacteria. The primary determinant of successful NAA testing for tuberculosis depends on the shedding of mycobacterial DNA in secretions from caseating granulomas and its dissemination into sterile body fluids or tissue biopsies. In multibacillary diseases with a high mycobacterial load, a positive Ziehl-Neelsen smear with a positive NAA test is diagnostic of active tuberculosis, whereas a positive Ziehl-Neelsen smear with a negative NAA test in the absence of inhibitors would indicate nontuberculous mycobacterial disease. The role of the NAA test is more important in paucibacillary diseases with low mycobacterial loads. The presence of polymerase chain reaction (PCR) inhibitors, however, especially in extrapulmonary specimens, may produce false-negative results. Although this problem can be overcome to some extent by extra extraction steps, the additional processing invariably leads to the loss of mycobacterial DNA. To circumvent this problem, a brief culture augmentation step is carried out before the NAA test is performed, which can enhance the mycobacterial load while concomitantly diluting inhibitors, thereby maintaining the sensitivity of the test without excessively increasing turnaround time. © Springer-Verlag 2005.postprin

Effect of applying the new clinical and laboratory standards institute ticarcillin/clavulanic acid, piperacillin, piperacillin/tazobactam and imipenem susceptibility breakpoints for Pseudomonas aeruginosa in Hong Kong

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Paradoxical deterioration during anti-tubercular treatment in a dialysis patient on maintenance steroid therapy

We report a 38-year-old Chinese woman with lupus nephritis on peritoneal dialysis and long-term maintenance steroid therapy. This patient developed paradoxical deterioration during anti-tubercular therapy for tuberculous lymphadenitis. The deterioration resolved spontaneously without change to pharmacotherapy. Paradoxical deterioration that may spontaneously resolve is a potential complication of anti-tubercular treatment in patients on long-term renal replacement therapy.published_or_final_versio

Emergence of NDM-1-producing Enterobacteriaceae in China

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Comparative host gene transcription by microarray analysis early after infection of the Huh7 cell line by SARS coronavirus and human coronavirus 229E

During the early stages of infection, SARS-CoV produces more severe perturbation of host cell gene expression in a human epithelial cell line of liver origin than the HCoV-229E.published_or_final_versio

Middle East respiratory syndrome coronavirus: another zoonotic betacoronavirus causing SARS-like disease

The source of the severe acute respiratory syndrome (SARS) epidemic was traced to wildlife market civets and ultimately to bats. Subsequent hunting for novel coronaviruses (CoVs) led to the discovery of two additional human and over 40 animal CoVs, including the prototype lineage C betacoronaviruses, Tylonycteris bat CoV HKU4 and Pipistrellus bat CoV HKU5; these are phylogenetically closely related to the Middle East respiratory syndrome (MERS) CoV, which has affected more than 1,000 patients with over 35% fatality since its emergence in 2012. All primary cases of MERS are epidemiologically linked to the Middle East. Some of these patients had contacted camels which shed virus and/or had positive serology. Most secondary cases are related to health care-associated clusters. The disease is especially severe in elderly men with comorbidities. Clinical severity may be related to MERS-CoV's ability to infect a broad range of cells with DPP4 expression, evade the host innate immune response, and induce cytokine dysregulation. Reverse transcription-PCR on respiratory and/or extrapulmonary specimens rapidly establishes diagnosis. Supportive treatment with extracorporeal membrane oxygenation and dialysis is often required in patients with organ failure. Antivirals with potent in vitro activities include neutralizing monoclonal antibodies, antiviral peptides, interferons, mycophenolic acid, and lopinavir. They should be evaluated in suitable animal models before clinical trials. Developing an effective camel MERS-CoV vaccine and implementing appropriate infection control measures may control the continuing epidemic. © 2015, American Society for Microbiology. All Rights Reserved.postprin

Clinical characteristics and risk factors of herpes zoster after bone marrow transplantation

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Medical treatment of viral pneumonia including SARS in immunocompetent adult

Since no randomized controlled trials have been conducted on the treatment of viral pneumonia by antivirals or immunomodulators in immunocompetent adults, a review of such anecdotal experience are needed for the more rational use of such agents. Case reports (single or case series) with details on their treatment and outcome in the English literature can be reviewed for pneumonia caused by human or avian influenza A virus (50 patients), varicella zoster virus (120), adenovirus (29), hantavirus (100) and SARS coronavirus (SARS-CoV) (841). Even with steroid therapy alone, the mortality rate appeared to be lower when compared with conservative treatment for pneumonia caused by human influenza virus (12.5% vs. 42.1%) and hantavirus (13.3% vs. 63.4%). Combination of an effective antiviral, acyclovir, with steroid in the treatment of varicella zoster virus may be associated with a lower mortality than acyclovir alone (0% vs. 10.3%). Combination of interferon alfacon-1 plus steroid, or lopinavir/ritonavir, ribavirin plus steroid were associated with a better outcome than ribavirin plus steroid (0% vs. 2.3% vs. 7.7%, respectively). Combination of lopinavir/ritonavir plus ribavirin significantly reduced the virus load of SARS-CoV in nasopharyngeal, serum, stool and urine specimens taken between day 10 and 15 after symptom onset when compared with the historical control group treated with ribavirin. It appears that the combination of an effective antiviral and steroid was associated with a better outcome. Randomized therapeutic trial should be conducted to ascertain the relative usefulness of antiviral alone or in combination with steroid. © 2004 The British Society. Published by Elsevier Ltd. All rights reserved.postprin

Successful control of vancomycin-resistant Enterococcus faecium outbreak in a neurosurgical unit at non-endemic region

Vancomycin-resistant enterococci (VRE) have emerged in many parts of the world, but have only been reported sporadically in Hong Kong. We report an outbreak of vancomycin-resistant Enterococcus faecium (VREfm) in a neurosurgical unit at a tertiary teaching hospital between 3 March and 3 April 2009 in Hong Kong. During the outbreak investigation, clinical samples from 193 (91.5%) of 211 patients who had stayed in the neurosurgical unit and 506 environmental samples were screened for VREfm. Besides the index case, another 3 (1.6%) out of 192 patients were found to be positive for VREfm. Two (0.4%) out of 506 environmental samples were positive for VREfm. All four clinical and two environmental isolates were found to be clonally related by pulse-field gel electrophoresis. The risk factors for nosocomial acquisition of VREfm included advanced age (P¼0.047), presence of nasogastric tubing (P¼0.002) and tracheostomy (Po0.001), and the use of b-lactam antibiotics (Po0.001) and vancomycin (P¼0.001). Contrary to other VRE outbreaks in which the spread was rapid, the neurosurgical patients’ immobilization because of coma and mechanical ventilation dependency, and the vigilant practice of hand hygiene by health-care workers successfully limited the number of secondary cases despite the delayed recognition of the index case. All patients with VREfm were labeled in the hospital network information system so that stringent infection control measures with contact precautions would be carried out once these patients were readmitted to prevent its spread in our locality.published_or_final_versio