Infectious disease trends among immunocompromised hosts

With our rapidly ageing population and advancing treatments for patients with haematological, oncologic and rheumatological diseases, there are increasing numbers of immunocompromised patients presenting to primary care and general hospitals with opportunistic infections. This review considers the trends of these infections across four representative subgroups: fungal infections following haematopoietic stem cell transplant; viral infections post solid organ transplant; mycobacterial infections during treatment with targeted biological agents; and bacterial infections as a cause of fever in neutropenia. We also consider the impact of host, pathogens, environments and treatments on the epidemiology and outcomes of these infections.

Tracking the emergence of pandemic Influenza A/H1N1/2009 and its interaction with seasonal influenza viruses in Singapore

<p><b>INTRODUCTION</b>Since the emergence of the pandemic influenza A/H1N1/2009 virus in April 2009, diagnostic testing in many countries has revealed the rapid displacement and then replacement of circulating seasonal influenza viruses by this novel virus.</p><p><b>MATERIALS AND METHODS</b>In-house seasonal and pandemic influenza-specific polymerase chain reaction assays were introduced and/or developed at the Molecular Diagnosis Centre (MDC) at the National University Hospital (NUH), Singapore. These assays have been used to test all samples received from in-patients, out-patients, staff and visitors for suspected pandemic influenza A/H1N1/2009 infection.</p><p><b>RESULTS</b>Prior to the arrival of the pandemic A/H1N1/2009 virus in Singapore at the end of May 2009, seasonal influenza A/H3N2 predominated in this population, with very little seasonal influenza A/H1N1 and B viruses detected. Within about 1 month of its arrival in Singapore (mainly during June to July 2009), this pandemic virus rapidly displaced seasonal influenza A/H3N2 to become the predominant strain in the Singaporean population served by MDC/NUH.</p><p><b>CONCLUSIONS</b>Realtime molecular techniques have allowed the prompt detection of different influenza subtypes during this current pandemic, which has revealed the displacement/replacement of previously circulating seasonal subtypes with A/H1N1/2009. Although some of this may be explained by immunological cross-reactivity between influenza subtypes, more studies are required.</p>

Methicillin-resistant Staphylococcus aureus control at the National University Hospital, Singapore: a historical perspective

<p><b>INTRODUCTION</b>The National University Hospital (NUH) was the first restructured public hospital in Singapore. As the most recently established hospital in Singapore, it has a unique record of alert organisms including methicillin-resistant Staphylococcus aureus (MRSA).</p><p><b>MATERIALS AND METHODS</b>We performed a critical review of multiple data sources including surveillance reports, task force reports, published abstracts and manuscripts concerning MRSA in NUH.</p><p><b>RESULTS</b>Three themes emerged: 1) the MRSA rates have remained relatively stable through the life of the hospital despite the increased complexity of patients and intermittent intensified control efforts; 2) the major MRSA task forces were driven by surgeons and 3) a scientific approach to epidemiology has a critical role in understanding and planning interventions.</p><p><b>CONCLUSION</b>Although containment of MRSA can be accomplished to a certain degree through mobilisation of existing resources, higher goals such as eradication would require massive infusions of infrastructural, scientific and human resources to have a chance of success.</p>

Twentieth century influenza pandemics in Singapore

<p><b>INTRODUCTION</b>Singapore was substantially affected by three 20th Century pandemics. This study describes the course of the pandemics, and the preventive measures adopted.</p><p><b>MATERIALS AND METHODS</b>We reviewed and researched a wide range of material including peer-reviewed journal articles, Ministry of Health reports, Straits Settlements reports and newspaper articles. Monthly mortality data were obtained from various official sources in Singapore.</p><p><b>RESULTS</b>The 1918 epidemic in Singapore occurred in 2 waves--June to July, and October to November--resulting in up to 3500 deaths. The 1957 epidemic occurred in May, and resulted in widespread morbidity, with 77,000 outpatient attendances in government clinics alone. The 1968 epidemic occurred in August and lasted a few weeks, with outpatient attendances increasing by more than 65%. The preventive measures instituted by the Singapore government during the pandemics included the closure of schools, promulgation of public health messages, setting up of influenza treatment centres, and screening at ports. Students, businessmen and healthcare workers were all severely affected by the pandemics.</p><p><b>CONCLUSIONS</b>Tropical cities should be prepared in case of a future pandemic. Some of the preventive measures used in previous pandemics may be applicable during the next pandemic.</p>

Screening for vancomycin-resistant enterococci using stools sent for Clostridium difficile cytotoxin assay is effective: results of a survey of 300 Patients in a large Singapore Teaching Hospital

<p><b>INTRODUCTION</b>To assess the efficacy of screening stools sent for Clostridium difficile cytotoxin assay (CDTA) for surveillance of vancomycin-resistant enterococci (VRE).</p><p><b>MATERIALS AND METHODS</b>From April to May 2005, all stools submitted for CDTA were also cultured for VRE using vancomycin containing culture media. Isolates were identified to species level and vancomycin resistance confirmed, followed by polymerase chain reaction (PCR) for detection of vancomycin resistance genes and DNA fingerprinting. Over 2 consecutive days during that period, stool specimens or rectal swabs were also obtained from all patients in high-risk units (haematology, oncology, renal and intensive care). Fifty-one patients in each group were compared in terms of VRE risk factors previously identified.</p><p><b>RESULTS AND DISCUSSION</b>The prevalence of VRE in both groups was similar [3/204 (1.5%) in the CDTA arm and 1/97 (1.0%) in the high-risk arm; P = 1.0, Fisher's exact test]. Prevalence of risk factors for VRE colonisation, including age, duration of hospitalisation, exposure to antibiotics, exposure to surgical procedures, presence of malignancy and diabetes mellitus was similar in both groups (P > 0.05). Only renal failure (P < 0.05) was more common in the high-risk group. All 4 isolates of VRE identified were genetically distinct by variable number tandem repeat (VNTR) typing; 3 were Enterococcus faecium (2 with the vanB gene, 1 with vanA) and one E. faecalis.</p><p><b>CONCLUSION</b>Less than 2% of our high-risk patients are VRE carriers. In-hospital VRE screening using stools sent for CDTA is a simple, reasonable surrogate for screening individual high-risk patients as the patient risk profile is similar and the yield comparable in a low-prevalence setting.</p>