Natural disasters — a microbe's paradise

Impact of wars and natural disasters on emerging and re-emerging infectious diseases

Emerging Infectious Diseases (EIDs) and Re-Emerging Infectious Diseases (REIDs) constitute significant health problems and are becoming of major importance. Up to 75% of EIDs and REIDs have zoonotic origin. Several factors such as the destruction of natural habitats leading humans and animals to live in close proximity, ecological changes due to natural disasters, population migration resulting from war or conflict, interruption or decrease in disease prevention programs, and insufficient vector control applications and sanitation are involved in disease emergence and distribution. War and natural disasters have a great impact on the emergence/re-emergence of diseases in the population. According to a World Bank estimation, two billion people are living in poverty and fragility situations. Wars destroy health systems and infrastructure, curtail existing disease control programs, and cause population movement leading to an increase in exposure to health risks and favor the emergence of infectious diseases. A total of 432 catastrophic cases associated with natural disasters were recorded globally in 2021. Natural disasters increase the risk of EID and REID outbreaks by damaging infrastructure and leading to displacement of populations. A Generic National Action Plan covering risk assessment, mechanism for action, determination of roles and responsibilities of each sector, the establishment of a coordination mechanism, etc. should be developed.

Detection of the 'Big Five' mold killers of humans: Aspergillus, Fusarium, Lomentospora, Scedosporium and Mucormycetes

Fungi are an important but frequently overlooked cause of morbidity and mortality in humans. Life-threatening fungal infections mainly occur in immunocompromised patients, and are typically caused by environmental opportunists that take advantage of a weakened immune system. The filamentous fungus Aspergillus fumigatus is the most important and well-documented mold pathogen of humans, causing a number of complex respiratory diseases, including invasive pulmonary aspergillosis, an often fatal disease in patients with acute leukemia or in immunosuppressed bone marrow or solid organ transplant recipients. However, non-Aspergillus molds are increasingly reported as agents of disseminated diseases, with Fusarium, Scedosporium, Lomentospora and mucormycete species now firmly established as pathogens of immunosuppressed and immunocompetent individuals. Despite well-documented risk factors for invasive fungal diseases, and increased awareness of the risk factors for life-threatening infections, the number of deaths attributable to molds is likely to be severely underestimated driven, to a large extent, by the lack of readily accessible, cheap, and accurate tests that allow detection and differentiation of infecting species. Early diagnosis is critical to patient survival but, unlike Aspergillus diseases, where a number of CE-marked or FDA-approved biomarker tests are now available for clinical diagnosis, similar tests for fusariosis, scedosporiosis and mucormycosis remain experimental, with detection reliant on insensitive and slow culture of pathogens from invasive bronchoalveolar lavage fluid, tissue biopsy, or from blood. This review examines the ecology, epidemiology, and contemporary methods of detection of these mold pathogens, and the obstacles to diagnostic test development and translation of novel biomarkers to the clinical setting.

Outbreaks of Serratia marcescens and Serratia rubidaea bacteremia in a central Kathmandu hospital following the 2015 earthquakes

Background

Human infections with Serratia spp. are generally limited to Serratia marcescens and the Serratia liquefaciens complex. There is little data regarding the infections caused by the remaining Serratia spp., as they are seldom isolated from clinical specimens.

Methods

In this health care setting in Kathmandu, Nepal routine blood culture is performed on all febrile patients with a temperature >38°C or when there is clinical suspicion of bacteremia. During 2015 we atypically isolated and identified several Serratia spp. We extracted clinical data from these cases and performed whole genome sequencing on all isolates using a MiSeq system (Ilumina, San Diego, CA, USA).

Results

Between June and November 2015, we identified eight patients with suspected bacteremia that produced a positive blood culture for Serratia spp., six Serratia rubidaea and five Serratia marcescens. The S. rubidaea were isolated from three neonates and were concentrated in the neonatal intensive care unit between June and July 2015. All patients were severely ill and one patient died. Whole genome sequencing confirmed that six Nepalese S. rubidaea sequences were identical and indicative of a single-source outbreak.

Conclusions

Despite extensive screening we were unable to identify the source of the outbreak, but the inferred timeline suggested that these atypical infections were associated with the aftermath of two massive earthquakes. We speculate that deficits in hygienic behavior, combined with a lack of standard infection control, in the post-earthquake emergency situation contributed to these unusual Serratia spp. outbreaks.

Identifying the emerging human pathogen Scedosporium prolificans by using a species-specific monoclonal antibody that binds to the melanin biosynthetic enzyme tetrahydroxynaphthalene reductase

The dematiaceous (melanized) fungus Scedosporium prolificans is an emerging and frequently fatal pathogen of immunocompromised humans and which, along with the closely related fungi Pseudallescheria boydii, Scedosporium apiospermum and S. aurantiacum in the Pseudallescheria-Scedosporium complex, is a contributing aetiology to tsunami lung and central nervous system infections in near-drowning victims who have aspirated water laden with spores. At present, the natural habitat of the fungus is largely unknown, and accurate detection methods are needed to identify environmental reservoirs of infectious propagules. In this study, we report the development of a monoclonal antibody (mAb) (CA4) specific to S. prolificans, which does not cross-react with closely related fungi in the Pseudallescheria-Scedosporium complex or with a wide range of mould and yeast species pathogenic to humans. Using genome sequencing of a soil isolate and targeted gene disruption of the CA4 antigen-encoding gene, we show that mAb CA4 binds to the melanin-biosynthetic enzyme tetrahydroxynaphthalene reductase. Enzyme-deficient mutants produce orange-brown or green-brown spore suspensions compared with the black spore suspension of the wild-type strain. Using mAb CA4 and a mAb (HG12) specific to the related fungi P. boydii, P. apiosperma, S. apiospermum and S. aurantiacum, we demonstrate how the mAbs can be used in combination with a semiselective isolation procedure to track these opportunistic pathogens in environmental samples containing mixed populations of human pathogenic fungi. Specificity of mAb CA4 was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of fungi isolated from estuarine muds.

Increased Incidence of Escherichia Coli Bacteremia Post-Christchurch Earthquake 2011: Possible Associations

Introduction

Earthquakes are natural events that contribute to the transmission of infectious diseases. The aim of this research was to determine whether the observed increase in Escherichia coli (E. coli) bloodstream infections (BSI) during the period March-June 2011 was associated with the February 2011 Christchurch earthquake.

Methods

Descriptive statistics and spatial distributional analysis techniques were used to quantify patients with E. coli BSI in 2009-2011.

Results

E. coli BSI acquired from non-catheter related urinary tract infection (UTI) was the predominant infection type, with the greatest increase during March-June 2011. Bacteremia incidence was higher in females than in males for 2009-2011. In 2011, the median age of patients was 75 years, and an increase in males acquiring such infections was noted. Spatial distributional analysis failed to show direct association between bacteremia cases and liquefaction-related land damage or drinking water contamination. A higher incidence of E. coli BSI post-earthquake in the eastern suburbs, which tend towards a higher level of socioeconomic deprivation, was observed.

Conclusion

A number of possible factors contributing to the observed increase in E. coli BSI acquired from UTI in 2011 were considered. Individuals with higher deprivation indices, males and the elderly may be particularly vulnerable to the effects of a major disaster with subsequent breakdown of infrastructure. These findings have important implications in natural disaster situations, and justify development of strategies to identify UTI and pyelonephritis risk factors and to manage E. coli bacteremia incidence rates.

SchousboeM, LyndsJ, AmbroseC. Increased incidence of Escherichia Coli bacteremia post-Christchurch earthquake 2011: possible associations. Prehosp Disaster Med. 2013;28(3):1-8.

Tracking the emerging human pathogen Pseudallescheria boydii by using highly specific monoclonal antibodies

Pseudallescheria boydii has long been known to cause white grain mycetoma in immunocompetent humans, but it has recently emerged as an opportunistic pathogen of humans, causing potentially fatal invasive infections in immunocompromised individuals and evacuees of natural disasters, such as tsunamis and hurricanes. The diagnosis of P. boydii is problematic since it exhibits morphological characteristics similar to those of other hyaline fungi that cause infectious diseases, such as Aspergillus fumigatus and Scedosporium prolificans. This paper describes the development of immunoglobulin M (IgM) and IgG1 kappa-light chain monoclonal antibodies (MAbs) specific to P. boydii and certain closely related fungi. The MAbs bind to an immunodominant carbohydrate epitope on an extracellular 120-kDa antigen present in the spore and hyphal cell walls of P. boydii and Scedosporium apiospermum. The MAbs do not react with S. prolificans, Scedosporium dehoogii, or a large number of clinically relevant fungi, including A. fumigatus, Candida albicans, Cryptococcus neoformans, Fusarium solani, and Rhizopus oryzae. The MAbs were used in immunofluorescence and double-antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) to accurately differentiate P. boydii from other infectious fungi and to track the pathogen in environmental samples. Specificity of the DAS-ELISA was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of environmental isolates.