Post-mortem microbiology in sudden death: sampling protocols proposed in different clinical settings

BACKGROUND

Autopsies, including minimally invasive autopsies, are a powerful tool for determination of the cause of death. When a patient dies from an infection, microbiology is crucial to identify the causative organism. Post-mortem microbiology (PMM) aims to detect unexpected infections causing sudden deaths; confirm clinically suspected but unproven infection; evaluate the efficacy of antimicrobial therapy; identify emergent pathogens; and recognize medical errors. Additionally, the analysis of the thanatomicrobiome may help to estimate the post-mortem interval.

AIMS

The aim was to provide advice in the collection of PMM samples and to propose sampling guidelines for microbiologists advising autopsy pathologists facing different sudden death scenarios.

SOURCES

A multidisciplinary team with experts in various fields of microbiology and autopsies on behalf of the ESGFOR (ESCMID - European Society of Clinical Microbiology and Infectious Diseases - study group of forensic and post-mortem microbiology and in collaboration with the European Society of Pathology) developed this narrative review based on a literature search using MedLine and Scopus electronic databases supplemented with their own expertise.

CONTENT

These guidelines address measures to prevent sample contamination in autopsy microbiology; general PMM sampling technique; protocols for PMM sampling in different scenarios and using minimally invasive autopsy; and potential use of the evolving post-mortem microbiome to estimate the post-mortem interval.

IMPLICATIONS

Adequate sampling is paramount to identify the causative organism. Meaningful interpretation of PMM results requires careful evaluation in the context of clinical history, macroscopic and histological findings. Networking and closer collaboration among microbiologists and autopsy pathologists is vital to maximize the yield of PMM.

[Importance of the forensic autopsy in the diagnosis of septic shock: a case report]

Septic shock sometimes starts with unspecific symptoms that hamper the clinical diagnosis and, therefore an appropriate treatment. When the septic shock follows a fulminating course with a fatal outcome, the etiological diagnosis has to be conducted post-mortem. Sudden unexpected deaths in children and young adults are frequently the object of medico-legal autopsies. Some sudden unexpected deaths have an infectious origin, which requires further analyses, including microbiology, to establish the cause of death. Here, the case of a fatal septic shock in a 19-month old male infant is presented. After a mild foot injury, an infection by Streptococcus pyogenes progressed to septic shock with a fatal outcome as post-mortem studies demonstrated.

Association between individual and combined SNPs in genes related to innate immunity and incidence of CMV infection in seropositive kidney transplant recipients

In this study, we assessed the association between single-nucleotide polymorphisms (SNPs) in seven candidate genes involved in orchestrating the immune response against cytomegalovirus (CMV) and the 12-month incidence of CMV infection in 315 CMV-seropositive kidney transplant (KT) recipients. Patients were managed either by antiviral prophylaxis or preemptive therapy. CMV infection occurred in 140 patients (44.4%), including 13 episodes of disease. After adjusting for various clinical covariates, patients harboring T-allele genotypes of interleukin-28B (IL28B) (rs12979860) SNP had lower incidence of CMV infection (adjusted hazard ratio [aHR]: 0.66; 95% confidence interval [CI]: 0.46-0.96; p-value = 0.029). In the analysis restricted to patients not receiving prophylaxis, carriers of the TT genotype of toll-like receptor 9 (TLR9) (rs5743836) SNP had lower incidence of infection (aHR: 0.61; 95% CI: 0.38-0.96; p-value = 0.035), whereas the GG genotype of dendritic cell-specific ICAM 3-grabbing nonintegrin (DC-SIGN) (rs735240) SNP exerted the opposite effect (aHR: 1.86; 95% CI: 1.18-2.94; p-value = 0.008). An independent association was found between the number of unfavorable SNP genotypes carried by the patient and the incidence of CMV infection. In conclusion, specific SNPs in IL28B, TLR9 and DC-SIGN genes may play a role in modulating the susceptibility to CMV infection in CMV-seropositive KT recipients.

How to optimise the yield of forensic and clinical post-mortem microbiology with an adequate sampling: a proposal for standardisation

Post-mortem microbiology (PMM) is an important tool in forensic pathology, helping to determine the cause and manner of death, especially in difficult scenarios such as sudden unexpected death (SD). Currently, there is a lack of standardization of PMM sampling throughout Europe. We present recommendations elaborated by a panel of European experts aimed to standardize microbiological sampling in the most frequent forensic and clinical post-mortem situations. A network of forensic microbiologists, pathologists and physicians from Spain, England, Belgium, Italy and Turkey shaped a flexible protocol providing minimal requirements for PMM sampling at four practical scenarios: SD, bioterrorism, tissue and cell transplantation (TCT) and paleomicrobiology. Biosafety recommendations were also included. SD was categorized into four subgroups according to the age of the deceased and circumstances at autopsy: (1) included SD in infancy and childhood (0-16 years); (2) corresponded to SD in the young (17-35 years); (3) comprised SD at any age with clinical symptoms; and (4) included traumatic/iatrogenic SD. For each subgroup, a minimum set of samples and general recommendations for microbiological analyses were established. Sampling recommendations for main bioterrorism scenarios were provided. In the TCT setting, the Belgian sampling protocol was presented as an example. Finally, regarding paleomicrobiology, the sampling selection for different types of human remains was reviewed. This proposal for standardization in the sampling constitutes the first step towards a consensus in PMM procedures. In addition, the protocol flexibility to adapt the sampling to the clinical scenario and specific forensic findings adds a cost-benefit value.

IL28RA polymorphism (rs10903035) is associated with insulin resistance in HIV/HCV-coinfected patients

Hepatitis C virus (HCV) infection is associated with insulin resistance (IR), although mechanisms leading to IR in these patients are not completely understood. The aim of this study was to evaluate the association of interleukin 28B (IL28B) and interleukin 28 receptor alpha (IL28RA) polymorphisms with IR among human immunodeficiency virus (HIV)/HCV-coinfected patients. We carried out a cross-sectional study on 203 patients. IL28B (rs8099917) and IL28RA (rs10903035) polymorphisms were genotyped by GoldenGate(®) assay. IR was defined as homeostatic model assessment (HOMA) values ≥3.00. Univariate and multivariate generalized linear models (GLM) were used to compare HOMA values and the percentage of patients with IR according to IL28B and IL28RA genotypes. In total, 32% (n = 65/203) of the patients had IR. IL28B rs8099917 TT was not significantly associated with HOMA values and IR. In contrast, rs10903035 AA was significantly associated with high HOMA values taking into account all patients (P = 0.024), as well as the subgroups of patients with significant fibrosis (P = 0.047) and infected with HCV genotype 3 (P = 0.024). Additionally, rs10903035 AA was significantly associated with IR (HOMA ≥3.00) in all patients (adjusted odds ratio (aOR) = 2.02; P = 0.034), in patients with significant fibrosis (aOR = 2.86; P = 0.039) and HCV genotype 3 patients (aOR = 4.89; P = 0.031). In conclusions, IL28RA polymorphism (rs10903035) seems to be implicated in the glucose homeostasis because AA genotype increases the likelihood of IR, but this association was different depending on hepatic fibrosis and HCV genotype.

European mitochondrial haplogroups are not associated with hepatitis C virus (HCV) treatment response in HIV/HCV-coinfected patients

OBJECTIVES

Mitochondria are multifunctional organelles with a key role in the innate immune response against viral infections. Mitochondrial DNA (mtDNA) haplogroups have been related to AIDS progression and CD4 T-cell recovery in HIV-infected patients, and to a delay in the development of liver fibrosis in HIV/hepatitis C virus (HCV)-coinfected patients. We performed a study to investigate whether mtDNA haplogroups may be associated with HCV treatment response in HIV/HCV-coinfected patients on pegylated interferon (pegIFN) plus ribavirin (RBV).

METHODS

We performed a retrospective study in 304 patients who completed a course of HCV therapy. mtDNA polymorphisms were genotyped using Sequenom's MassARRAY platform. The interleukin-28B (IL-28B) polymorphism (rs12980275) was genotyped using the GoldenGate® assay. Sustained virological response (SVR) was defined as an undetectable HCV viral load at week 24 after the end of treatment. The statistical analysis was carried out using on-treatment data.

RESULTS

The SVR rates were 52.6% (160 of 304) for all patients, and 37.8% (46 of 201) for patients with HCV genotype 1 or 4 vs. 81.4% (83 of 102) for patients with HCV genotype 2 or 3 (P < 0.001). No significant associations were found between mtDNA haplogroup and SVR when all patients were included in the analysis and when patients were stratified by HCV genotype (i.e. those with genotypes 1/4 and 2/3 analysed separately) or IL-28B rs12980275 genotype.

CONCLUSIONS

European mtDNA haplogroups were not related to HCV treatment response in HIV/HCV-coinfected patients on pegIFN-α/RBV therapy.

IL28RA polymorphism is associated with early hepatitis C virus (HCV) treatment failure in human immunodeficiency virus-/HCV-coinfected patients

Due to the poor rate of response to hepatitis C virus (HCV) with pegylated interferon and ribavirin treatment in HCV/HIV coinfected patients, key factors for predicting failure would be useful. We performed a retrospective study on 291 patients on HCV treatment, who had early virological response (EVR) data. IL28B and IL28RA polymorphisms were performed using the GoldenGate(®) assay. Unfavourable genotypes at IL28B (rs12980275 AG/GG and rs8099917 GT/GG) and an unfavourable allele at IL28RA (rs10903035 G) were associated with early treatment failure. However, only the rs12980275 AG/GG genotype and rs10903035 G allele remained independently associated with early failure in the overall population (OR = 4.15 (95% CI = 1.64-10.54) and OR = 2.00 (95% CI = 1.19-3.36), respectively) as well as in GT1/4 patients (OR = 5.07 (95% CI = 1.81-14.22) and OR = 2.03 (95% CI = 1.13-3.66), respectively). Next, a decision tree showed early treatment failure increased from 37.1% to 65.5% when the unfavourable rs12980275 AG/GG and rs10903035 AG/GG genotypes and HCV-RNA≥ 500.000 IU/mL were taken into account in GT1/4 patients. In contrast, the failure rate decreased from 37.1% to 11.9% when the favourable rs12980275 AA and rs10903035 AA genotypes were detected. The percentage of patients correctly classified was 78.4%, and AUROC was 0.802 ± 0.028. Regarding GT3 patients, the presence of the GCGCA haplotype (all unfavourable alleles) was associated with early treatment failure, while no association was observed for the IL28B polymorphisms. In conclusion, the IL28RA polymorphism was associated with early treatment failure independently of the IL28B SNPs. The combination of IL28B and IL28RA polymorphisms might be a valuable tool for predicting early treatment failure before starting HCV treatment.

Sequencing and gene expression of the porcine ITIH SSC13 cluster and its effect on litter size in an Iberian × Meishan F2 population

The aim of the present study was to identify polymorphisms and to analyze endometrial gene expression of the porcine SSC13 ITIH cluster that could explain differences in prolificacy of 255 F(2) sows derived from an Iberian (Ib)×Meishan (Me) intercross in which QTL for the number of piglets born alive (NBA) and total number of piglets born (TNB) were previously detected on this chromosome. Sequencing of ITIH-1, -3, and -4 mRNAs was done and several polymorphisms segregating within the Ib×Me population were found in all three genes. Significant associations with NBA were found for two SNPs from ITIH-1, four from ITIH-3, and four SNPs from ITIH-4 (p<0.05). Haplotypes for the significant SNPs were calculated by segregation analysis and a marker assisted association test indicated that the alleles coming from the Meishan breed had a favorable effect on NBA for all three genes. Interestingly, some of the significant SNPs were located within the von Willebrand domain of the ITIH proteins, the binding site of molecules essential for the synthesis of the extracellular matrix during cumulus expansion. Gene expression analyses also revealed differences in the expression level of the ITIH-3 gene regarding the prolificacy performance (high or low) and the uterus sample (apical or basal).

Analysis of candidate genes underlying two epistatic quantitative trait loci on SSC12 affecting litter size in pig

The previous results from a genome scan for total number of piglets born and number of piglets born alive in a F(2) Iberian by Meishan intercross showed several single and epistatic QTL. One of the most interesting results was obtained for SSC12, where two QTL affecting both traits showed epistatic interaction. In this study, we proposed two genes (SLC9A3R1 and NOS2) as biological and potentially positional candidates underlying these QTL. Both cDNAs were characterized and 23 polymorphisms were detected. A chromosome scan was conducted with 12 markers, plus one SNP in SLC9A3R1 and one in NOS2, covering 110 cM of SSC12. The epistatic QTL (QTL1 at 15 cM and QTL2 at 97 cM) were confirmed, and SLC9A3R1 and NOS2 were mapped around the QTL1 and QTL2 regions respectively. Several SNPs in both genes were tested with standard animal model and marker assisted association tests. The most significant results were obtained with the NOS2 haplotype defined by one missense SNP c.2192C > T (Val to Ala) and a 15 bp duplication at the 3'UTR. This duplication seems to include AU-rich elements, and could be a target site for miRNA, therefore there are statistical and biological indications to consider this haplotype as the potential causal mutation underlying QTL2. SLC9A3R1 results were not conclusive. Although the interaction between the SNPs was not significant, we cannot reject the possibility of interaction of the NOS2 haplotype with other polymorphisms closely linked to the SL9A3R1 SNPs analysed.

Extracorporeal renal lithotripsy: Evolution of residual lithiasis treated with thiazides

OBJECTIVES

To analyze the evolution of residual lithiasis after renal extracorporeal shock wave lithotripsy (ESWL) and to show the prolonged efficacy of thiazides in the treatment of residual lithiasis in patients with calcium lithiasis.

METHODS

We performed a longitudinal, analytical, 36-month study in 100 patients with residual calcium lithiasis after ESWL randomly distributed into two groups: 50 patients treated with placebo (controls, group 1) and 50 treated with hydrochlorothiazide, 50 mg/24 hr (group 2). All patients in both groups underwent imaging studies (simple radiography of the urinary tract and renal ultrasonography) and a metabolic urinary study.

RESULTS

The percentage of global expulsion of lithiasis during the follow-up period was significantly greater (chi-square exponent = 19.938, P = 0.001) in the patients treated with thiazides (72%) than in the control group (36%), although a large number of patients in this group underwent new ESWL sessions. During the follow-up period, we performed ESWL on 42% of the patients in group 1 and 18% of group 2, a statistically significant difference (chi-square exponent = 6.881, P = 0.032).

CONCLUSIONS

The results of our study have shown that residual lithiasis progresses in 58% of patients undergoing observation, and new ESWL sessions will be necessary in 42%. We observed a significant relationship between the presence of a urinary lithogenic pattern and the progression of the residual lithiasis. The administration of thiazides stabilizes or reduces the growth of residual lithiasis and favors its spontaneous elimination, thus reducing the need for new sessions of ESWL. This effect of thiazides is highly significant in patients presenting with hypercalciuria.

[The role of thiazides in the prophylaxis of recurrent calcium lithiasis]

OBJECTIVE

To show the prolonged efficacy of thiazides in the prophylaxis and treatment of recurrences in patients with calcium oxalate and phosphate lithiasis.

METHODS

A randomised prospective study is conducted, with a three-year follow-up, in 150 patients diagnosed with recurrent calcium lithiasis. The patients are divided into three groups: A) 50 cases subject to observation with no treatment, B) 50 cases treated with 50 mg/day of hydrochlorothiazide, and C) 50 cases treated with 50 mg of hydrochlorothiazide and 20 mlEq of potassium citrate/day. Each group is subject to a renal study with imaging techniques and a urinary metabolic study at baseline, 12, 24 and 36 months.

RESULTS

The patients treated with thiazides (Groups B and C) obtain a significant reduction in lithiasis recurrence compared with the control group (Group A). The most common abnormality found in the metabolic study was hypercalciuria, 52% of cases; 16% present a mixed lithogenic pattern. The number of recurrences and need for new sessions of extracorporeal lithotripsy in patients with hypercalciuria treated with thiazides is significantly smaller than in Group A (p=0.003).

CONCLUSIONS

We observe a significant relation between lithogenic pattern and lithiasis recurrence. Thiazides help us to control lithogenic factors and recurrences in patients with calcium lithiasis. This effect is prolonged and significant in patients with hypercalciuria.

Virological analysis in the diagnosis of sudden children death: A medico-legal approach

Infections are considered to be an important cause of unexpected death in children. It has also been assumed that respiratory viruses are involved in the genesis of sudden infant death syndrome (SIDS). The Spanish National Institute of Toxicology and Forensic Sciences act as the forensic reference centre for Spain. We analyse the experience of this centre in the virological study of 64 cases of sudden children death where viral serology, virological cultures, herpesviruses polymerase chain reaction (PCR) and electron microscopy were performed. According to pathological findings, death could only be attributed to an adenovirus infection in one amygdalitis with upper airways stenosis and asphyxia. Human herpes virus 6 (HHV-6) was detected by PCR in one case with pathological findings characteristic of SIDS. Recent infection by respiratory syncytial virus (RSV), Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were also detected. Meanwhile, 85.9% of the cases yielded negative viral results. Twenty-eight infants were finally categorised as SIDS. Pathological findings of infection were detected in 12 patients despite the negativity of viral analyses. Although viral infection is an uncommon cause of sudden children death, a complete microbiological investigation will help to solve the puzzle of SIDS. Definitive guidelines for microbiological analyses need to be updated whilst new pathogens are discovered or new techniques are implemented in order to clarify unsolved cases.

Latex agglutination for bacterial antigens and meningococcus PCR: two useful tools in legal sudden deaths

Bacterial infections are considered to be a major cause of sudden deaths. The recognition of infections caused by Neisseria meningitidis is an essential duty of medicolegal offices due to the risk of secondary cases. Since other microorganisms, such as Haemophilus influenzae and Streptococcus pneumoniae, are also involved in infectious sudden deaths, the identification of the pathogen responsible for death is essential in order to establish a positive diagnosis while also preventing secondary meningococcal cases. However, because of the unreliability of culture methods used for autopsy specimens and the fragile nature of the microorganisms, other techniques were used. In this study, the detection of specific antigens of N. meningitidis (serogroups A, B, C, Y and W135), H. influenzae type b, S. pneumoniae and Group B Streptococcus was undertaken in 40 samples from sudden death cases in legal procedures with a latex agglutination test. In addition, a meningococcus polymerase chain reaction (PCR) assay (ctrA, crgA and siaD genes) was also used as a corroboration method for positive N. meningitidis agglutinations. Eleven cases of sudden death were confirmed to be due to meningococcus while one case was confirmed to have been caused by H. influenzae type b fulminant epiglottitis. Rapid laboratory diagnosis of meningococcal infection allowed contacts management and notification to the health authorities. From the point of view of the authors, forensic diagnosis of unascertained deaths should include latex agglutination and meningococcus PCR when a fulminant infection by N. meningitidis or H. influenzae is suspected as well as in deaths where the cause is unclear.

[Malignant fibrohistiocytoma of the spermatic cord]

A malignant fibrous histiocytoma (MFH) of the spermatic cord is presented and a review of the literature has been performed. The patient here presented survived for eight years and is probably cured of his tumour. In general, MFHs of the spermatic cord have a good prognosis, even when they attain a big size. They have a worse evolution when satellite nodules are present. Although more experience is needed. It is our feeling, that a spermatic MFH smaller than 8 cm, without any satellite nodule and less than 25% nuclei positive to MIB-1 (cell proliferation marker), may have a conservative therapy, including only tumorectomy.

Carbapenem resistance in Pseudomonas aeruginosa from cystic fibrosis patients

The evolution of imipenem resistance was evaluated in Pseudomonas aeruginosa sequentially isolated from 42 patients with cystic fibrosis. Susceptibility was determined using a commercial microdilution system and imipenem resistance was confirmed by the agar dilution technique. Resistance to imipenem increased during the years from 1988 to 1992. A total of 12 patients (28.5%) carried resistant strains (11.6% of the total P. aeruginosa isolates) but only two of them were treated with the carbapenem. The other patient under imipenem treatment did not harbour resistant isolates. Sixty-four per cent of the imipenem resistant isolates were also meropenem resistant and showed low susceptibility to the other beta-lactams and tobramycin and amikacin. Twenty-one strains were selected for biochemical study. Imipenem susceptible strains showed normal OprD in two strains and diminished OprD in two more. Five strains with MIC of imipenem of 4-8 mg/L lacked OprD while another two had a band with decreased density. All strains with MIC higher than 8 completely lacked this band in western-blot analysis. Imipenem MICs of 0.5-2 mg/L only slightly increased to 1-4 mg/L when a pattern of beta-lactamase derepression was observed. While those with imipenem MICs between 8-16 mg/L increased the imipenem MIC to 16-64 mg/L in the population with a beta-lactamase derepression phenotype.

Value of ploidy pattern and nuclear texture in the diagnosis of primary hyperparathyroidism

OBJECTIVE

To determine if there are subvisual differences (quantitation of DNA and study of chromatin texture) that distinguish single-gland parathyroid disease (adenoma) from multiple-gland disease (hyperplasia).

STUDY DESIGN

Forty-eight parathyroid glands from 41 patients with primary hyperparathyroidism were studied. Cytometric differences between the chief cells and clear cells were sought. An image cytometer was used to study histologic sections stained with DNA stain reagent. In each case a total of 200 cells were measured in consecutive fields. To distinguish chief cells from clear cells, a sample of 15,600 cells collected in consecutive fields in 78 histologic sections was analyzed.

RESULTS

The results indicated that none of the continuous variables differentiated between single-gland and multiple-gland parathyroid disease. The most common ploidy pattern was diploid (25/45), followed by hypodiploid (7/45) and polyploid (5/45). A tetraploid population > 3% was found in 18/45 of the cases and was more frequent in single-gland lesions (15/34) than in multiple-gland lesions (3/11). The most significant discrete variables were growth pattern and binucleation or multinucleation. Clear and chief cells were classified correctly in 61.3% of the crossover validation tests using the standard deviation of nuclear shape karyometric variable and in 76.3% using the standard deviation of maximal correlation coefficient karyometric variable. Although ploidy pattern did not show significant differences, polyploidy, aneuploidy and tetraploidy > 3% were slightly more common in chief cells.

CONCLUSION

In primary hyperparathyroidism there are no subvisual differences that can distinguish adenoma from hyperplasia. Nonetheless, by cytometry, most parathyroid cells can be classified correctly as clear or chief cells.

[1st Spanish epidemic of plasmid resistance to 3d generation cephalosporins: the implication of SHV-2]

BACKGROUND

The first spanish outbreak of bacterial strains showing resistance to third generation cephalosporins and due to the presence of the extended spectrum beta-lactamase SHV-2 is reported. This outbreak was observed in Madrid during the years 1988-1990 and involved the San Carlos University Hospital with the same type of isolates at the Ramón y Cajal University Hospital.

METHODS

The screening for extended-spectrum beta-lactamases was performed by the double-disk synergy test. Analytical isoelectric focusing and susceptibility tests were performed in all the strains showing a presumptive extended-spectrum beta-lactamase.

RESULTS

Fifty-nine strains belonging to four bacterial species (Klebsiella pneumoniae, 61%; Serratia marcescens, 31%; Klebsiella oxytoca, 5%, and Escherichia coli, 3%) showed a beta-lactamase of point isoelectric 7.6; the susceptibility tests demonstrated more resistance to cefotaxime and ceftriaxone than to ceftazidime and aztreonam.

CONCLUSIONS

The biochemical, kinetic and isoelectrofocusing parameters demonstrated the presence of a SHV-2 enzyme. The blind application of NCCLS breakpoints would lead to false "susceptibility" results in over 40% of the cases.