Staphylococcus Aureus Osteomyelitis as an Inducer of Tolerance to Escherichia Coli Pyelonephritis: an Experimental Study

The high incidence of osteomyelitis in vulnerable populations like those with multiple injuries or elderly undergoing joint arthroplasties generates the question what may be their responses to subsequent infection by high virulent isolates. Rabbits were subject to two operations at three week intervals; sham osteomyelitis and sham pyelonephritis (group S); sham osteomyelitis and Escherichia coli pyelonephritis (group P); and Staphylococcus aureus osteomyelitis and E. coli pyelonephritis (group OP). Survival was recorded; cytokine stimulation of circulating mononuclear cells (PBMCs) and tissue myeloperoxidase (MPO) activity and bacterial growth were monitored. In some experiments, dalbavancin treatment was given before pyelonephritis. Healthy PBMCs were pre-treated with bone homogenate, S. aureus or both. Mortality of groups S, P and OP after induction of pyelonephritis was 0%, 50% and 8.3% respectively. Tumour necrosis factor-alpha (TNFα) production by PBMCs was significantly lower in the OP group at 48 hours. E. coli bacterial load was similar in groups P and OP at death or sacrifice whereas the MPO activity of group OP was decreased. Production of TNFα was further decreased among dalbavancin treated rabbits; in these rabbits tissue MPO was increased. TNFα production decreased when healthy PBMCs pre-treated with bone homogenate, S. aureus (HKSA) or both were stimulated with E. coli (HKEC); production was further decreased in the presence of anti-TLR4 and anti-TLR9. It is concluded that staphylococcal osteomyelitis modulated the innate immune responses of the host leading to protection from death by highly virulent E. coli. Tolerance to TLR ligands is the most likely mechanism of action. © 2020, The Author(s)

Experimental Models of Partial Intestinal Obstruction in Young Mice, Establishment, and Evaluation

Background: Partial small bowel obstruction (SBO) is a common, potentially hazardous, surgical entity caused by numerous factors in humans. A number of techniques have been reported as efficient to simulate partial SBO in murine models. However, there is little data concerning their long-term survival. Our study presents a novel technique and evaluates its long-term efficiency compared with other commonly used techniques. Materials and methods: Sixty C57BL/6 mice aged 6 to 8 wk were randomly divided into five intervention groups: ligation, intestinal ring, partial ligation, microclips, and the novel triple suture technique. The ring groups were subdivided into narrow, medium, and wide ring and partial ligation groups were subdivided at 1/3, 1/2, and 2/3 of the lumen. Survival cutoff time was set at 4 wk. Animals were then euthanized and small bowel muscle layer thickness was histopathologically evaluated. Results: None of the animals of the ligation and the ring groups reached the cutoff survival time. The mortality rate of the partial ligation and the microclips groups at the 4-week period were 33.3% and 0%, respectively. However, elimination of the performed intervention was revealed at the time of euthanasia and no alterations of the muscle layer were revealed at histopathology. The “triple suture” group had a survival rate of 90% until euthanasia and the sutures were apparent in all cases. Macroscopic evaluation showed small to mild proximal lumen dilatation in 6 of 10 animals. Histopathological evaluation of the specimens confirmed the partial obstruction. Conclusions: The “triple suture” technique is a new, robust, reliable, and inexpensive technique for experimental long-standing partial SBO, with very low mortality. © 2020 Elsevier Inc

Endoscopic versus surgical treatment for thoracopancreatic fistulas complicating chronic pancreatitis: A systematic review

Background: Thoracopancreatic fistulae are a rare complication of chronic pancreatitis. The aim of the present study is to evaluate potential risk factors for endoscopic treatment failure and explore the safety of surgery when utilized either upfront or as a “bail-out” procedure after failed endoscopic treatment. Method: A comprehensive literature search was conducted on the MedLine, Scopus, Embase, and Web of Knowledge databases for cases of thoracopancreatic fistulae. Data regarding patient demographics, fistula anatomy, and treatment interventions performed were extracted for further analysis. Results: The study pool consisted of 75 case reports and 19 case series published between the years 1972 and 2020. Duct disruption in the pancreatic body was most commonly encountered (41.1%), and a left pleural effusion was the most common manifestation (46%). Endoscopic treatment was attempted for 104 patients with an overall success rate of 42.3% (n = 44). Predictive factors for eventual success of endoscopic treatment were the ability of endoscopic retrograde cholangiopancreatography to diagnose the thoracopancreatic leak (odds ratio 9.76, 95% confidence interval 2.71–35.09, P <.001), the use of pancreatic duct stents (odds ratio 22.1, 95% confidence interval 7.92–61.61, P <.001), and the use of sphincterotomy (odds ratio 7.96, 95% confidence interval 2.1–30.1, P <.001). Conversely, the presence of pancreatic duct calculi was associated with endoscopic treatment failure (odds ratio 0.34, 95% confidence interval 0.12–0.94, P =.03). Pooled results suggest that surgical outcomes were comparable between the primary and salvage surgery groups. Conclusion: A step-up approach from endoscopic management to salvage surgery may be effectively employed in cases of thoracopancreatic fistulae refractory to endoscopic treatment. © 2021 Elsevier Inc

Daptomycin as adjunctive treatment for experimental infection by Acinetobacter baumannii with resistance to colistin

The emergence of Acinetobacter baumannii with resistance to colistin (ABRC) led to the investigation of daptomycin as an adjunctive to colistin for these isolates. In this study, one ABRC carbapenemase-producing bloodstream isolate was examined. Minimum inhibitory concentrations (MICs) were >512, >512 and 8 µg/mL for imipenem, daptomycin and colistin, respectively. First, a ‘humanised’ model of the pharmacokinetics of daptomycin and colistin was developed in 18 male C57BL/6 mice. Then, 112 mice were infected by intraperitoneal injection of the ABRC isolate and were randomly assigned into four groups of once-daily treatment for 7 days: group A, controls treated with saline; group B, treated with 20 mg/kg colistin; group C, treated with 50 mg/kg daptomycin; and group D, treated with both agents. Survival was recorded for 7 days in ten mice per group. The remaining mice were sacrificed at regular time intervals following bacterial challenge and the bacterial outgrowth in the liver, lung and right kidney was determined. Mean serum concentrations of daptomycin at 15, 30 and 60 min post-dose were 121.8, 110.3 and 100.4 µg/mL, respectively. The respective concentrations of colistin were 13.9, 9.1 and 7.5 µg/mL. The 7-day mortality in groups A, B, C and D was 100%, 50%, 100% and 0%, respectively. Tissue outgrowth of the right kidney was significantly decreased in group D compared with group B after 72 h. Daptomycin used in combination with colistin leads to prolonged survival in an experimental infection by ABRC. Failure of colistin alone is probably related to rebound of tissue outgrowth. © 2019 Elsevier Lt

An animal model of limitation of gut colonization by carbapenemase-producing Klebsiella pneumoniae using rifaximin

Current knowledge suggests that infection by carbapenem-resistant enterobacteria is preceded by gut colonization. It is hypothesized that colonization is eradicated by non-absorbable antibiotics like rifaximin. We investigated the effect of rifaximin against carbapenem-resistant Klebsiella pneumoniae (CRKP) in vitro and in a mouse model. We studied the in vitro efficacy of rifaximin against 257 CRKP clinical isolates, 188 KPC producers and 69 OXA-48 producers, by minimum inhibitory concentration and time-kill assays. We then developed a model of gut colonization by feeding 30 C57Bl6 mice with 108 cfu of one KPC-KP isolate for 7 days; mice were pre-treated orally with saline, omeprazole or ampicillin. Then, another 60 mice with established KPC-2 gut colonization received orally for 7 consecutive days rifaximin 180 mg/kg dissolved in ethanol and 4% bile or vehicle. On days 0, 3 and 7 stool samples were collected; mice were sacrificed for determination of tissue outgrowth. At a concentration of 1000 μg/ml rifaximin inhibited 84.8% of CRKP isolates. Α 3 × log10 decrease of the starting inoculum was achieved by 100, 250 and 500 μg/ml of rifaximin after 24 h against 25, 55 and 55% of isolates. Pre-treatment with ampicillin was necessary for gut colonization by KPC-KP. Treatment with rifaximin succeeded in reducing KPC-KP load in stool and in the intestine. Rifaximin inhibits at clinically meaningful gut concentrations the majority of CRKP isolates and is efficient against gut colonization by KPC-KP. © 2022, The Author(s)

Association of modulation of pro-inflammatory responses by dectin-2 with preterm delivery: An experimental model

Problem: Pro-inflammatory responses of pathogen recognition receptors (PRR) are implicated in preterm delivery (PTD). Dectin-2 is one PRR recognizing unselective carbohydrate structures; its participation in PTD has never been studied before. Method of study: In an experimental model, PTD was induced in female pregnant wild-type (WT) mice and mice with homologous deficiency for dectin-2 by the intraperitoneal injection of bacterial lipopolysaccharide (LPS) on day 14 of pregnancy. Time to delivery and fetal mortality were recorded. Challenged mice were killed for tissue collection and splenocyte isolation 6 hours later. Concentrations of tumour necrosis factor-alpha (TNFα), interleukin (IL)-1α, and IL-1β were measured. Results: Delivery was induced significantly earlier in WT than dectin-2-/- mice; however, fetal mortality was higher among dectin-2-/- mice. Candida albicans challenge could not lead to these changes. Sacrifice experiments showed that LPS challenge led to significant increase of TNFα, IL-1α, and IL-1β in maternal tissues of WT; this was further enhanced for TNFα and IL-1β in dectin-2-/- mice. Pre-treatment with the prostaglandin inhibitor diclofenac delayed time to delivery of WT mice, but not of dectin2-/- mice. TNFα stimulation of splenocytes of dectin2-/- mice was enhanced with the addition of anti-TLR4 and decreased in the presence of lipid A. Conclusions: Dectin-2 delays LPS-induced PTD by enhancing the production of pro-inflammatory cytokines. © 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Lt

Immunomodulation Through Beta-D-glucan in Chemically-induced Necrotizing Pancreatitis

Background: Although the ability of β-D-glucan and monophosphoryl lipid A (MPLA) to modulate immune responses has been studied in human primary cells, their effect on sterile inflammation models such as necrotizing pancreatitis has never been investigated. Materials and methods: 85 male New Zealand rabbits were assigned into following groups: A: control, B: pretreatment with β-D-glucan 3 d before pancreatitis, C: pretreatment with MPLA 3 d before pancreatitis, D: pretreatment with β-D-glucan and laminarin 3 d before pancreatitis, E: treatment with β-D-glucan 1 d after pancreatitis, and F: MPLA 1 d after pancreatitis. Pancreatitis was induced by sodium taurocholate injection into the pancreatic duct and parenchyma. Survival was recorded for 21 d. On days 1, 3, and 7, blood was collected for amylase measurement. Peripheral blood mononuclear cells were isolated and stimulated for tumor necrosis factor alpha and interleukin 10 production. Pancreatic necrosis and tissue bacterial load were assessed. Results: 21-d survival was prolonged after pretreatment or treatment with β-D-glucan; this benefit was lost with laminarin administration. At sacrifice, pancreatic inflammatory alterations were more prominent in the control group. Bacterial load was lower after pretreatment or treatment with β-D-glucan and MPLA. Tumor necrosis factor alpha production from stimulated peripheral blood mononuclear cells was significantly decreased, whereas interleukin 10 production remained unaltered after pretreatment or treatment with β-D- glucan. Conclusions: β-D-glucan reduces mortality of experimental pancreatitis in vivo. This is mediated through attenuation of cytokine production and prevention of bacterial translocation. © 2020 Elsevier Inc