Reverse transcriptase inhibitors prevent liver abscess formation during Escherichia coli bloodstream infection.

The presence of bacteria in the bloodstream is associated with severe clinical outcomes. In mice, intravenous inoculation of Escherichia coli can lead to the formation of macroscopic abscesses in the liver. Abscesses are regions of severe necrosis and consist of millions of bacteria surrounded by inflammatory immune cells. Liver abscess susceptibility varies widely across strains of mice, but the host factors governing this variation are unknown. Here, we profiled hepatic transcriptomes in mice with varying susceptibility to liver abscess formation. We found that transcripts from endogenous retroviruses (ERVs) are robustly induced in the liver by E. coli infection and ERV expression positively correlates with the frequency of abscess formation. Hypothesizing that ERV-encoded reverse transcriptase may generate cytoplasmic DNA and heighten inflammatory responses, we tested whether nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) influence abscess formation. Strikingly, a single NRTI dose administered immediately following E. coli inoculation prevented abscess formation, leading to a concomitant 100,000-fold reduction in bacterial burden. We provide evidence that NRTIs inhibit abscess formation by preventing the tissue necrosis that facilitates bacterial replication. Together, our findings suggest that endogenous reverse transcriptases drive inflammatory responses during bacterial bloodstream infection to drive abscess formation. The high efficacy of NRTIs in preventing abscess formation suggests that the consequences of reverse transcription on inflammation should be further examined, particularly in infectious diseases where inflammation drives negative clinical outcomes, such as sepsis.

Genetic and immune determinants of E. coli liver abscess formation.

Systemic infections can yield distinct outcomes in different tissues. In mice, intravenous inoculation of Escherichia coli leads to bacterial replication within liver abscesses, while other organs such as the spleen clear the pathogen. Abscesses are macroscopic necrotic regions that comprise the vast majority of the bacterial burden in the animal, yet little is known about the processes underlying their formation. Here, we characterize E. coli liver abscesses and identify host determinants of abscess susceptibility. Spatial transcriptomics revealed that liver abscesses are associated with heterogenous immune cell clusters comprised of macrophages, neutrophils, dendritic cells, innate lymphoid cells, and T-cells that surround necrotic regions of the liver. Abscess susceptibility is heightened in the C57BL lineage, particularly in C57BL/6N females. Backcross analyses demonstrated that abscess susceptibility is a polygenic trait inherited in a sex-dependent manner without direct linkage to sex chromosomes. As early as 1 d post infection, the magnitude of E. coli replication in the liver distinguishes abscess-susceptible and abscess-resistant strains of mice, suggesting that the immune pathways that regulate abscess formation are induced within hours. We characterized the early hepatic response with single-cell RNA sequencing and found that mice with reduced activation of early inflammatory responses, such as those lacking the LPS receptor TLR4 (Toll-like receptor 4), are resistant to abscess formation. Experiments with barcoded E. coli revealed that TLR4 mediates a tradeoff between abscess formation and bacterial clearance. Together, our findings define hallmarks of E. coli liver abscess formation and suggest that hyperactivation of the hepatic innate immune response drives liver abscess susceptibility.

MicroRNA Interference in Hepatic Host-Pathogen Interactions.

The liver is well recognized as a non-immunological visceral organ that is involved in various metabolic activities, nutrient storage, and detoxification. Recently, many studies have demonstrated that resident immune cells in the liver drive various immunological reactions by means of several molecular modulators. Understanding the mechanistic details of interactions between hepatic host immune cells, including Kupffer cells and lymphocytes, and various hepatic pathogens, especially viruses, bacteria, and parasites, is necessary. MicroRNAs (miRNAs), over 2600 of which have been discovered, are small, endogenous, interfering, noncoding RNAs that are predicted to regulate more than 15,000 genes by degrading specific messenger RNAs. Several recent studies have demonstrated that some miRNAs are associated with the immune response to pathogens in the liver. However, the details of the underlying mechanisms of miRNA interference in hepatic host-pathogen interactions still remain elusive. In this review, we summarize the relationship between the immunological interactions of various pathogens and hepatic resident immune cells, as well as the role of miRNAs in the maintenance of liver immunity against pathogens.

TLR2 Promotes Monocyte/Macrophage Recruitment Into the Liver and Microabscess Formation to Limit the Spread of Listeria Monocytogenes.

TLR2 signaling plays a critical protective role against acute Listeria monocytogenes (Lm) infection by up-regulating inflammatory cytokines and promoting macrophage antimicrobial capabilities. However, the underlying mechanism by which TLR2 regulates hepatic macrophage-mediated anti-Lm immune responses remains poorly understood. In this study, we found that both the absolute number and proportion of monocyte/macrophage (Mo/MΦ) in the liver and spleen of Tlr2-/- mice were significantly lower compared to wild type mice. Changes in TLR2 signaling in both hepatocytes and Mo/MΦs were associated with the infiltration of Mo/MΦs in response to Lm-infection. Analyses by proteome profiler array and ELISA revealed that hepatocytes recruited Mo/MΦs via TLR2-dependent secretion of CCL2 and CXCL1, which was confirmed by receptor blocking and exogenous chemokine administration. Importantly, we found that TLR2 contributed to macrophage mobility in the liver through a TLR2/NO/F-actin pathway, facilitating the formation of macrophage-associated hepatic microabscesses. Moreover, TLR2 activation induced the expression of several PRRs on hepatic macrophages associated with the recognition of Lm and augmented macrophage bacterial clearance activity. Our findings provide insight into the intrinsic mechanisms of TLR2-induced Mo/MΦ migration and mobility, as well as the interaction between macrophages and hepatocytes in resistance to Lm infection.

Serotype and virulence genes of Klebsiella pneumoniae isolated from mink and its pathogenesis in mice and mink.

In the study, 15 K. pneumoniae strains were isolated from the mink experiencing respiratory distress in mideastern Shandong province, China, and the prevalence of K. pneumoniae in the sampled mink was 11.9% (15/126). Fourteen (93.33%) of the 15 K. pneumoniae isolates were identified as serotype K2 and hypermucoviscosity phenotype. The 12 virulence-associated genes of the K. pneumoniae isolates were tested. The prevalence of the wabG gene for the isolates were 100% (15/15), the ureA gene 100% (15/15), the rmpA gene 93.33% (14/15), the aerobactin gene 93.33% (14/15), the uge gene 93.33% (14/15), the IucB gene 80% (12/15) and the ybtA gene 13.33% (2/15). But the other five genes, fim, iroNB, wcaG, alls and kfuBC, gave a negative PCR reaction in the 15 isolates, respectively. The animal experiments using K. pneumoniae-SD-12 and K. pneumoniae-SD-21 demonstrated that the serotype K2 was high virulence for mice and mink. These finding implied there exist potential threat that K. pneumoniae pathogens could transmit to human, especially the fur animal farm workers and residents lived near the fur animal farms. Therefore, the etiology and epidemiological surveillance of K. pneumoniae in mink should be strengthened for people's public health.

Genomewide association study of liver abscess in beef cattle.

Fourteen percent of U.S. cattle slaughtered in 2011 had liver abscesses, resulting in reduced carcass weight, quality, and value. Liver abscesses can result from a common bacterial cause, , which inhabits rumen lesions caused by acidosis and subsequently escapes into the blood stream, is filtered by the liver, and causes abscesses in the liver. Our aim was to identify SNP associated with liver abscesses in beef cattle. We used lung samples as a DNA source because they have low economic value, they have abundant DNA, and we had unrestricted access to sample them. We collected 2,304 lung samples from a beef processing plant: 1,152 from animals with liver abscess and 1,152 from animals without liver abscess. Lung tissue from pairs of animals, 1 with abscesses and another without, were collected from near one another on the viscera table to ensure that pairs of phenotypically extreme animals came from the same lot. Within each phenotype (abscess or no abscess), cattle were pooled by slaughter sequence into 12 pools of 96 cattle for each phenotype for a total of 24 pools. The pools were constructed by equal volume of frozen lung tissue from each animal. The DNA needed to allelotype each pool was then extracted from pooled lung tissue and the BovineHD Bead Array (777,962 SNP) was run on all 24 pools. Total intensity (TI), an indicator of copy number variants, was the sum of intensities from red and green dyes. Pooling allele frequency (PAF) was red dye intensity divided TI. Total intensity and PAF were weighted by the inverse of their respective genomic covariance matrices computed over all SNP across the genome. A false discovery rate ≤ 5% was achieved for 15 SNP for PAF and 20 SNP for TI. Genes within 50 kbp from significant SNP were in diverse pathways including maintenance of pH homeostasis in the gastrointestinal tract, maintain immune defenses in the liver, migration of leukocytes from the blood into infected tissues, transport of glutamine into the kidney in response to acidosis to facilitate production of bicarbonate to increase pH, aggregate platelets to liver injury to facilitate liver repair, and facilitate axon guidance. Evidence from the 35 detected SNP associations combined with evidence of polygenic variation indicate that there is adequate genetic variation in incidence rate of liver abscesses, which could be exploited to select sires for reduced susceptibility to subacute acidosis and associated liver abscess.

Absceso hepático secundario a una perforación duodenal por espina de pescado: descripción de un caso / Liver abscess secondary to duodenal perforation by fishbone: report of a case

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Transfer of CMY-2 Cephalosporinase from Escherichia coli to Virulent Klebsiella pneumoniae Causing a Recurrent Liver Abscess.

A CMY-2-producing capsular type K2 Klebsiella pneumoniae strain (TVGHKP93) with multidrug resistance was isolated from a recurrent liver abscess in a patient who also carried a CMY-2-producing Escherichia coli strain (TVGHEC01) in the stool. TVGHKP93 retained its high virulence compared with that of the isogenic strain (TVGHKP60) with wild-type resistance from the first liver abscess. Our conjugation experiment showed the successful transfer of the blaCMY-2-carrying plasmid from TVGHEC01 into TVGHKP60. The transconjugant showed both high virulence and the multidrug-resistant phenotype, as did TVGHKP93.

TREM-1 promotes survival during Klebsiella pneumoniae liver abscess in mice.

Klebsiella pneumoniae liver abscess (KPLA) is prevalent in East Asia. Liver abscess can develop after translocation of K. pneumoniae from a patient's bowel into the liver via the portal circulation. TREM-1 (triggering receptor expressed on myeloid cells 1) amplifies inflammatory signaling during infection, but its role in KPLA is poorly understood. We used an animal study to characterize the role of TREM-1 in KPLA. We compared survival rates, bacterial burdens in tissues, inflammatory cytokine levels, and histology findings between wild-type and Trem-1 knockout (KO) mice after oral inoculation of capsular type K1 K. pneumoniae. Translocation of K. pneumoniae to mesenteric lymph nodes and liver was examined, and intestinal permeability, antimicrobial peptide expression, and the clearance of K. pneumoniae in the small intestine were determined. In the absence of TREM-1, KPLA model mice showed increased K. pneumoniae dissemination, enhanced liver and systemic inflammation, and reduced survival. Impaired bacterial clearance in the small intestine causes enhanced K. pneumoniae translocation, which renders Trem-1 KO mice more susceptible to K. pneumoniae oral infection. In conclusion, TREM-1-mediated bacterial clearance in the small intestine is an important immune response against K. pneumoniae. TREM-1 deficiency enhances K. pneumoniae translocation in the small intestine and increases mortality rates in mice with KPLA.

Ampicillin and amoxicillin use and the risk of Klebsiella pneumoniae liver abscess in Taiwan.

BACKGROUND: Klebsiella pneumoniae liver abscess (KPLA) is prevalent in East Asia. Use of amoxicillin/ampicillin may lead to overgrowth of K. pneumoniae in the intestine and predispose to KPLA. We used an animal study and nationwide population-based database to investigate the association between ampicillin/amoxicillin use and KPLA in Taiwan. METHODS: In an animal study, ampicillin or sterile water was administered orogastrically in serotype K1 K. pneumoniae-colonized mice and the outcome was compared. We identified 855 cases with liver abscess and selected 3420 age- and sex-matched control subjects from the National Health Insurance Research Database. Conditional logistic regression was used to estimate the adjusted odds ratios (ORs) for the association between recent use of ampicillin/amoxicillin and KPLA. RESULTS: Ampicillin administration predisposed K. pneumoniae-colonized mice to increased bacterial burden, liver abscess and necrosis, and lethality. The population-based study showed that the adjusted OR associating the use of ampicillin/amoxicillin within the past 30 days with KPLA was 3.5 (95% confidence interval, 2.5-5.1). No association was found with use in the past 31-90 days. CONCLUSIONS: Ampicillin/amoxicillin therapy started within the past 30 days was associated with increased risk for KPLA. We should avoid the overuse of these antibiotics to prevent undesired disease in the endemic area.

HepG2 cells infected with Klebsiella pneumoniae show DNA laddering at apoptotic and necrotic stages.

Virulent Klebasiella pneumoniae (KP) inflicts severe liver abscesses in infected patients. This study investigated how the bacterial infection affected cell survival at the molecular level, in a cultured cell model. A strain of KP highly virulent in mice was isolated from a patient with liver abscess, and was used to infect HepG2 cells. The infected cells were examined for their viability, DNA fragmentation, and proteins involved in apoptosis or necrosis. We found that the infection decreased the viability of HepG2 cells at 4 hours (h) to 12 h post infection (pi). DNA ladders appeared 6-16 h pi and flow cytometry analysis showed apoptosis at 3-5 h pi, secondary necrosis at 6-9 h pi and primary necrosis at 8-9 h pi. Cleavages of Caspase 7, Caspase 9, α-Fodrin, and PARP were evident at 2-4 h pi. At 7 h pi, we observed the following: increased nuclear AIF, the release from mitochondria of cytosolic Apaf-1 and Cyt c, increased DFF40 expression, decreased DFF45, decreased BcL-xL and the release of Endo G from mitochondria to nucleus. Cellular ATP concentration decreased at 4-8 h pi, accompanied by increased Calpain-2 expression. In summary, infected HepG2 cells underwent apoptosis early after infection and progressed to secondary necrosis and primary necrosis. Nuclear fragmentation corresponded to Caspase 7 activation and the appearance of Endo G and DFF40 in the nucleus, with a concomitant decrease in DFF45. Mitochondrial release of Cyt c together with activation of Caspase 9 and Apaf-1 in cytosol was also observed. Early-hour cleavage of poly(ATP-ribose) polymerase (PARP) followed by the later activation of PARP corresponded to the appearance of DNA laddering, and the depletion of cellular ATP was associated with the appearance of necrosis.

Purine nucleoside phosphorylase deficiency with fatal course in two sisters.

Purine nucleoside phosphorylase (PNP) deficiency is a rare combined immunodeficiency disorder presenting with clinically recurrent infections, failure to thrive, various neurological disorders, malignancies, and autoimmune diseases. Here, we report two sisters with a fatal course of PNP deficiency due to delay in diagnosis. The first patient developed a liver abscess by Aspergillus fumigatus and the second patient developed Mycobacterium tuberculosis complex lymphadenitis and probable pulmonary tuberculosis due to disseminated BCG infection. The patients also suffered from sclerosing cholangitis. Mutation analysis of the PNP gene from both sisters revealed a homozygous mutation for a G>A at nucleotide 349 (349 G>A transition), which changes alanine 117 to theronine in exon 4 (A117T). An increased awareness of early signs, symptoms, and abnormal laboratory findings of PNP deficiency will establish the early prognosis and treatment.

A novel mutation in NCF1 in an adult CGD patient with a liver abscess as first presentation.

Chronic granulomatous disease (CGD) is an immunodeficiency caused by defects in the nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase complex and is usually diagnosed in early childhood. CGD patients suffer from severe, recurrent infections with bacteria, fungi and yeasts. We report a 25-year-old female with protracted fever because of a Staphylococcus aureus liver abscess, which did not resolve until breakthrough into the stomach. Despite her age, CGD was considered on diagnosis on the basis of the clinical symptoms. Analysis of the NADPH-oxidase activity confirmed CGD as the underlying condition. Western blotting revealed the absence of p47(phox) and subsequent sequencing of the p47(phox)-encoding gene, neutrophil cytosolic factor (NCF1), identified a deletion of 837C in the maternal NCF1 allele. The paternal allele contained a stopcodon because of a conversion between NCF1 and one of its PsiNCF1 pseudogenes. The patient had one novel mutation, c.837delC, and one conversion in NCF1, resulting in the complete absence of the p47(phox) component of the NADPH-oxidase complex. This p47(phox)-deficient CGD patient had the highest age at diagnosis reported thus far.

Greater omentum flaps and granulocyte transfusions as combined therapy of liver abscess in chronic granulomatous disease.

We report the case of a 17-year-old boy with gp91phax-deficient chronic granulomatous disease who developed a liver abscess due to Staphylococcus aureus. Despite treatment with appropriate antibiotics and gamma interferon for three months as well as incision and drainage, the abscess persisted unchanged in size. After surgical debridement, the abscess cavity was filled with two pedunculated greater omentum flaps as a direct feeder road of granulocytes to the infectious focus. An average of 48.5 x 10(9) granulocytes a day harvested from G-CSF-prestimulated donors were transfused for a total of 8 days without side effects. Ultrasound 3 months later showed no residual abscess. Combination of greater omentum flaps and transfusion of G-CSF-prestimulated granulocytes may be the optimal treatment for liver abscesses refractory to conventional therapy.

[Multiple liver abscesses in chronic granulomatosis]. / Multiple Leberabszesse bei chronischer Granulomatose.

We report on a case of a three year old boy, suffering from chronic granulomatosis disease, which led to repeated bacterial infections and finally to multiple liver abscesses. Diagnosis was based on the nitroblue-tetrazolium-test and histology. Antibiotic therapy over many weeks was not successful in spite of an adequate choice of medication against staphylococcal microorganisms and of good intracellular penetration, applicated parenterally. Only treatment by chloramphenicol after previous surgical drainage of the abscesses led to a dramatic clinical improvement and regression of the liver abscesses. The subsequent chemoprophylaxis with trimethoprim/sulfamethoxazole for at lest two years left the patient without clinical symptoms.

Chronic granulomatous disease in an adult with recurrent abscesses.

Chronic granulomatous disease (CGD), produced by an inherited defect in the bactericidal capacity of polymorphonuclear neutrophils, is associated with recurrent abscess formation in regional lymph nodes, pulmonary parenchyma, and liver requiring surgical drainage. It is now becoming increasingly recognized that this is not a uniformly fatal disease of childhood. Instead, patients with milder forms of the disease are being detected during adulthood. General surgeons should be aware of the possibility of this diagnosis in a patient with recurrent pyogenic abscesses requiring drainage. Making the diagnosis of CGD is important because with chronic prophylactic antibiotic therapy and early aggressive treatment of recognized infections, the morbidity and mortality of patients can be favorably influenced. We describe a 27-year-old man with recurrent liver abscesses who was subsequently found to have CGD.