A STUDY OF PNEUMOCOCCI AND ALLIED ORGANISMS IN HUMAN MOUTHS AND LUNGS AFTER DEATH

Bacterial Translocation and Sample Contamination in Postmortem Microbiological Analyses

The diagnostic value of postmortem bacteriology has been discussed controversially for decades. In the study herein, contamination during sampling procedures and postmortem translocation were investigated to interpret postmortem microbiology results. One hundred medicolegal autopsy cases in total were included. Radiology, histology, bacteriology, and biochemistry were performed in all cases. Based on all investigation findings, 4 groups of cases were identified: death unrelated to infection, true infections, false positive (contamination during sampling procedures, postmortem translocation and mixed situations), and undetermined. The results of this study indicate that postmortem bacteriology provides useful data supporting infection-related deaths, especially when potentially significant observations are accompanied by consistent autopsy, histology, and biochemistry. Result interpretation requires careful evaluation of number and type of isolated microorganisms.

The importance of microbiological testing for establishing cause of death in 42 forensic autopsies

Microorganisms have always been one of the great challenges of humankind, being responsible for both high morbidity and mortality throughout history. In a forensic setting microbiological information will always be difficult to interpret due to lack of antemortem information and changes in flora postmortem. With this study we aim to review the use of microbiological procedures at our forensic institute. In a retrospective study including 42 autopsies performed at our Institute, where microbiological test had been applied, analyses were made with regard to: type of microbiological tests performed, microorganisms found, histological findings, antemortem information, C-reactive protein measurement and cause of death. Fiftyone different microorganisms were found distributed among 37 cases, bacteria being the most abundant. Nineteen of the cases were classified as having a microbiological related cause of death. C-reactive protein levels were raised in 14 cases of the 19 cases, histological findings either supported or were a decisive factor for the classification of microbiologically related cause of death in 14 cases. As a multitude of abundant microorganisms are able to cause infection under the right circumstances, all findings should be compared to anamnestic antemortem information, before conclusions are drawn. A definite list of true pathogens is nearly impossible to compile.

Comprehensive postmortem analyses of intestinal microbiota changes and bacterial translocation in human flora associated mice

Background

Postmortem microbiological examinations are performed in forensic and medical pathology for defining uncertain causes of deaths and for screening of deceased tissue donors. Interpretation of bacteriological data, however, is hampered by false-positive results due to agonal spread of microorganisms, postmortem bacterial translocation, and environmental contamination.

Methodology/Principal Findings

We performed a kinetic survey of naturally occurring postmortem gut flora changes in the small and large intestines of conventional and gnotobiotic mice associated with a human microbiota (hfa) applying cultural and molecular methods. Sacrificed mice were kept under ambient conditions for up to 72 hours postmortem. Intestinal microbiota changes were most pronounced in the ileal lumen where enterobacteria and enterococci increased by 3–5 orders of magnitude in conventional and hfa mice. Interestingly, comparable intestinal overgrowth was shown in acute and chronic intestinal inflammation in mice and men. In hfa mice, ileal overgrowth with enterococci and enterobacteria started 3 and 24 hours postmortem, respectively. Strikingly, intestinal bacteria translocated to extra-intestinal compartments such as mesenteric lymphnodes, spleen, liver, kidney, and cardiac blood as early as 5 min after death. Furthermore, intestinal tissue destruction was characterized by increased numbers of apoptotic cells and neutrophils within 3 hours postmortem, whereas counts of proliferative cells as well as T- and B-lymphocytes and regulatory T-cells decreased between 3 and 12 hours postmortem.

Conclusions/Significance

We conclude that kinetics of ileal overgrowth with enterobacteria and enterococci in hfa mice can be used as an indicator for compromized intestinal functionality and for more precisely defining the time point of death under defined ambient conditions. The rapid translocation of intestinal bacteria starting within a few minutes after death will help to distinguish between relevant bacteria and secondary contaminants thus providing important informations for routine applications and future studies in applied microbiology, forensic pathology, and criminal medicine.

LACTOSE BROTH FOR ISOLATING BACTERIUM COLI FROM WATER

These authors suggest simplification of the technic by reducing the lactose content by addition of gentian violet, also Pasteurization in place of autoclaving. The announced value of gentian violet for preliminary enrichment of colon cultures is sustained, with cleaner plates and readier identification of colonies. Gentian violet has also advantages in ensuring keeping qualities in the broth.

Postmortem bacteriology in forensic pathology: diagnostic value and interpretation

The proof of a pathogenetic germ can be of evidential value for the medico-legal expertise concerning etiopathogenetic conclusions towards a causal relationship between infection and fatal outcome. In specific cases the forensic pathologist may be confronted with the decision whether cultures for postmortem bacteriological investigations should be obtained at autopsy. The present review surveys the value and practicability of postmortem bacteriological cultures in the light of the literature. The most promising media for postmortem bacteriological cultures are spleen and heart blood. In contrast, postmortem lung culture results are often unreliable due to frequently false positive results. The collection of specimens from at least two different sampling sites should be the standard procedure in cases where an underlying (potentially fatal) infection is presumed. Multiple postmortem cultures from different sampling sites raise the probability to identify the etiologic agent of antemortem infection. A careful correlation of culture results from different anatomical sampling sites with autopsy and histological findings is essential for the differentiation between vitally acquired infection and postmortem contamination. Various factors (e.g. the time interval between death and sampling of specimens, agonal spread of microorganisms or preceding antibiotic therapy prior to death) may limit the diagnostic utility of postmortem culture results. Contamination of specimens may, e.g. originate from inadequate sampling techniques, use of unsuitable transport media or postmortem growth of bacteria. The number of contaminated postmortem cultures increases when bowel manipulation or evisceration occurs prior to sampling and is depending on the anatomy of the sampling site. Polymicrobial growth can be considered contamination in the majority of cases. For the medico-legal expertise a thorough histological examination of inner organs and tissues is needed; the histological section has to represent the sampling site for culture. The presence of an underlying infection can be proven when postmortem bacteriological cultures yield a primary infectious pathogen and a cellular response in the affected tissue can be detected on the histopathological level. Postmortem bacteriology can be regarded as a reliable diagnostic tool for postmortem quality control of preceding diagnostic and therapeutic procedures and can serve as an additional indicator of nosocomial infections within a specific hospital environment. From the medico-legal point of view, a more widespread application of this valuable investigative procedure, that adds to diminish the number of otherwise unresolved deaths in forensic autopsy practice, is desirable.

Escherichia coli pneumonia in the elderly with reference to the role of E. coli K1 capsular polysaccharide antigen

Escherichia coli pneumonia occurred in 17 elderly patients over a two-year period. All cases were documented by transtracheal aspiration. Six of the 17 E. coli organisms causing pneumonia contained K1 capsular polysaccharide. E. coli K1 organisms did not appear to be more virulent than non-K1 strains as measured by incidence of bacteremia, shock and death. E. coli K1 pneumonia was usually community- acquired (five of six cases) and occurred in patients with a prior history of urinary infection. Non-K1 E. coli pneumonia occurred in the hospital setting in eight of 11 patients, and a gastrointestinal source of infection was likely in five patients. All patients were treated with appropriate initial antibiotic therapy, and 71 percent of patients survived.

Infections acquired in medical wards. A report from the Public Health Laboratory Service

A co-operative study was made of the incidence of infection acquired by patients in medical wards. Records were collected of 6740 admissions to 21 wards in 13 hospitals.

There were 384 clinical infections (5·7 per 100 patients admitted); 135 of them (35%) were infections of the lower respiratory tract, 72 (19%) were septic skin lesions or infected wounds, and 81 (21%) were urinary tract infections.

Infection was believed to have contributed to the death of 59 patients—17% of those infected or 8% of those dying in hospital. Nearly three-quarters of the deaths were attributed to ‘pneumonia’.

Acquired infections were most common and most severe at the extremes of age. There was an excess of males over females in staphylococcal infections and in infections of the lower respiratory tract, and of females over males in urinary tract infections.

The incidence of infection was above average in patients suffering from malignant disease, diabetes, rheumatoid arthritis, cerebral thrombosis and haemorrhage, and from diseases of the urinary tract and of the skin.

There were 110 acquired infections with Staph, aureus and 12 deaths were attributed to them. Over half of these infections were due to staphylococcal strains which caused only one clinical infection in a ward in the course of a year.

Pneumonia was difficult to diagnose in severely ill or moribund patients, and its clinical significance was hard to assess. It was not possible to obtain a reliable estimate of the part played by bacterial infection in its causation.