A Study of Post-Mortem Microbiology And Clinicopathological Features in Sudden Unexpected Death of Infant and Childhood (Sudi/Sudc)

Post-mortem microbiology (PMM) has been part of autopsy protocol for investigating of
Sudden Unexpected Death of Infant and Childhood (SUDI and SUDC) to detect
unexpected infections causing sudden death. Despite identifying pathogenic isolates, the
interpretation is challenging due to multiple factors; often leaving the cause of death
unexplained. In addition, there are substantial gaps in identifying risk factors and
understanding the pathogenesis. To date, this is the first cross-sectional study on Malaysian
SUDI and SUDC focusing on PMM, autopsy findings and virulence of bacterial isolates.
This study aimed to describe the associations between post-mortem bacterial isolates and
clinicopathological features in SUDI and SUDC in Klang Valley. Specifically, it focused
on detailing the clinicopathological features and bacterial isolates, identifying types of
bacteria, sampling sites, and growth culture outcomes, as well as determining the
associations and virulence genes of these bacterial isolates. Autopsy data of all <5-year-old
SUDI and SUDC cases performed in two tertiary centres in Klang Valley from 2018-2022
were extracted and analysed. Archived bacterial isolates were revived on culture media,
subjected to phenotypic observation, molecular confirmation, and subsequent whole
genome sequencing for virulence genes identification. A total of 118 SUDI and SUDC
cases were identified, with majority of deaths occurring in <1-year-old 95/118 (80.5%)
(p<0.05). Out of this total, 106 (89.8%) autopsies were conducted. PMM samplings were
performed in 94 (88.7%) of these autopsies. A total of 217 PMM samplings were able to
isolate microbial cultures in 92 (97.9%) of these 94 cases, identifying 179 (82.5%)
organisms. The commonest positive sampling sites were from lower respiratory tract
99/217 (45.6%) and hemoculture (blood/spleen/liver) 72/217 (33.2%). Bacterial isolates
account for the largest proportion of isolates at 163/179 (91.1%) with Klebsiella spp.
34/163 (20.9%), S. aureus 22/163 (13.5%) and E. coli 20/163 (12.3%) predominating.
Klebsiella species with tissue haemorrhage and inflammation was associated with age
group <1-year-old (p<0.001). PMM samplings detected unexpected infections contributory
to death in 81/92 (88.0%) with bacterial aetiologies in 75/81 (92.6%), which contributes
significantly to <1-year-old death (p<0.05). Virulence genes identified were related to
adherence, exoenzyme, immune modulation, effector delivery system, exotoxin, biofilm,
nutritional/metabolic factor, stress survival, antimicrobial activity/competitive advantage,
regulation and invasion. Antimicrobial resistance genes observed were related to
macrolide-lincosamide-streptogramin (MLS), rifampin, elfamycin, fluoroquinolones,
fosfomycin, aminocoumarins, sulfaanomide and betalactams. Klebsiella pneumoniae
isolates were found to have the greatest number of virulence factors, while Staphylococcus
aureus and E. coli have the highest number of AMR genes amongst gram-positive (15/21,
71.4%) and negative (12/21, 57.1%) bacteria respectively. Infants <1-year-old are generally
predisposed to bacterial infections due to immaturity of the immune system. However, in
most cases infants do not display a noticeable infection focus. Hence, PMM remains to
have critical value in SUDI/SUDC investigations. Identification of infective causes
warrants a public health intervention so that further risk assessment can be done in the
community to identify the source of the pathogen and provide insight into the epidemiology
and socio-demographic factors. This may help in recognizing possible associated risk
factors and thus, preventing further deaths.