Diagnostic and predictive value of the silkworm larvae plasma test for postoperative infection following gastrointestinal surgery

[Experimental study of silkworm larvae plasma colorimetry based on immune cascade reaction in accurate diagnosis of periprosthetic joint infection]

OBJECTIVE

To investigate the diagnostic efficacy of silkworm larvae plasma (SLP) colorimetry in the accurate diagnosis of periprosthetic joint infection (PJI).

METHODS

Ninety healthy male New Zealand white rabbits were used for knee arthroplasty with Swanson prosthesis. Then they were randomly divided into 3 groups according to different pathogenic bacteria: group A ( Staphylococcus aureus group), group B ( Staphylococcus epidermidis group) and group C ( Escherichia coli group), with 30 rats in each group. The PJI model was prepared by knee injection with 1 mL of pathogenic bacteria of different concentrations. Samples were taken before inoculation and at 7, 14, and 21 days after inoculation, and based on the 2018 PJI Philadelphia International Consensus diagnostic criteria, the success rate of modeling among 3 groups of experimental animals was determined. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic efficiency of SLP colorimetry were calculated.

RESULTS

At 21 days after inoculation, 26, 18, and 23 rabbits in groups A, B, and C were diagnosed as infection, respectively. The success rates of modeling were 86.7%, 60.0%, and 76.7%, respectively, showing no significant difference among the 3 groups ( χ ²=5.724, P=0.073). The results of PJI colorimetry showed that 1 false-positive animal (specificity 75.0%) appeared in group A at 7 days, and the specificity of SLP increased to 100.0% over time (on 14 and 21 days); on 14 and 21 days, another animal appeared false-negative results (sensitivity decreased from 100.0% to 96.2%). One false-positive animal appeared in group B at 7 days (specificity 91.7%), the specificity returned to 100.0% over time; 1 and 4 false-negative animals appeared at 14 and 21 days, respectively (sensitivity 94.4% and 83.3%, respectively). In group C, two false-positive animals (specificity 71.4%) were found at 7 days, and then returned to 100.0%. The diagnostic efficiency of groups A and C was very high at 21 days (96.7% and 100.0%), even for the low virulence Staphylococcus epidermidis in group B, the diagnostic efficiency could be maintained at 90.0% (21 days), and the overall diagnostic efficiency was very good (95.6%).

CONCLUSION

SLP colorimetry has high sensitivity, specificity, and diagnostic efficiency in the diagnosis of PJI, which is a potential diagnostic method.

Biomarkers of sepsis: time for a reappraisal

INTRODUCTION

Sepsis biomarkers can have important diagnostic, therapeutic, and prognostic functions. In a previous review, we identified 3370 references reporting on 178 different biomarkers related to sepsis. In the present review, we evaluate the progress in the research of sepsis biomarkers.

METHODS

Using the same methodology as in our previous review, we searched the PubMed database from 2009 until September 2019 using the terms "Biomarker" AND "Sepsis." There were no restrictions by age or language, and all studies, clinical and experimental, were included.

RESULTS

We retrieved a total of 5367 new references since our previous review. We identified 258 biomarkers, 80 of which were new compared to our previous list. The majority of biomarkers have been evaluated in fewer than 5 studies, with 81 (31%) being assessed in just a single study. Apart from studies of C-reactive protein (CRP) or procalcitonin (PCT), only 26 biomarkers have been assessed in clinical studies with more than 300 participants. Forty biomarkers have been compared to PCT and/or CRP for their diagnostic value; 9 were shown to have a better diagnostic value for sepsis than either or both of these biomarkers. Forty-four biomarkers have been evaluated for a role in answering a specific clinical question rather than for their general diagnostic or prognostic properties in sepsis.

CONCLUSIONS

The number of biomarkers being identified is still increasing although at a slower rate than in the past. Most of the biomarkers have not been well-studied; in particular, the clinical role of these biomarkers needs to be better evaluated.

Silkworm larvae plasma (SLP) assay for detection of bacteria: False positives secondary to inflammation in vivo

The silkworm larvae plasma (SLP) assay has been developed as a means to detect bacterial peptidoglycan as a surrogate for live bacteria. Here, we present results that indicate that generation of melanin by this assay is not fully reliable as a surrogate marker for bacterial count.

Diagnostic value of C-reactive protein to rule out infectious complications after major abdominal surgery: a systematic review and meta-analysis

PURPOSE

Infectious complications occur frequently after major abdominal surgery and have a major influence on patient outcome and hospital costs. A marker that can rule out postoperative infectious complications (PICs) could aid patient selection for safe and early hospital discharge. C-reactive protein (CRP) is a widely available, fast, and cheap marker that might be of value in detecting PIC. Present meta-analysis evaluates the diagnostic value of CRP to rule out PIC following major abdominal surgery, aiding patient selection for early discharge.

METHODS

A systematic literature search of Medline, PubMed, and Cochrane was performed identifying all prospective studies evaluating the diagnostic value of CRP after abdominal surgery. Meta-analysis was performed according to the PRISMA statement.

RESULTS

Twenty-two studies were included for qualitative analysis of which 16 studies were eligible for meta-analysis, representing 2215 patients. Most studies analyzed the value of CRP in colorectal surgery (eight studies). The pooled negative predictive value (NPV) improved each day after surgery up to 90% at postoperative day (POD) 3 for a pooled CRP cutoff of 159 mg/L (range 92-200). Maximum predictive values for PICs were reached on POD 5 for a pooled CRP cutoff of 114 mg/L (range 48-150): a pooled sensitivity of 86% (95% confidence interval (CI) 79-91%), specificity of 86% (95% CI 75-92%), and a positive predictive value of 64% (95% CI 49-77%). The pooled sensitivity and specificity were significantly higher on POD 5 than on other PODs (p < 0.001).

CONCLUSION

Infectious complications after major abdominal surgery are very unlikely in patients with a CRP below 159 mg/L on POD 3. This can aid patient selection for safe and early hospital discharge and prevent overuse of imaging.

Sepsis biomarkers: a review

INTRODUCTION

Biomarkers can be useful for identifying or ruling out sepsis, identifying patients who may benefit from specific therapies or assessing the response to therapy.

METHODS

We used an electronic search of the PubMed database using the key words "sepsis" and "biomarker" to identify clinical and experimental studies which evaluated a biomarker in sepsis.

RESULTS

The search retrieved 3370 references covering 178 different biomarkers.

CONCLUSIONS

Many biomarkers have been evaluated for use in sepsis. Most of the biomarkers had been tested clinically, primarily as prognostic markers in sepsis; relatively few have been used for diagnosis. None has sufficient specificity or sensitivity to be routinely employed in clinical practice. PCT and CRP have been most widely used, but even these have limited ability to distinguish sepsis from other inflammatory conditions or to predict outcome.

Relations among circulating monocytes, dendritic cells, and bacterial translocation in patients with intestinal obstruction

BACKGROUND

Little evidence is available regarding the relations among circulating monocytes, dendritic cells (DCs), and bacterial translocation (BT) in patients with intestinal obstruction.

METHODS

We investigated alterations in DCs in mesenteric lymph nodes (MLNs), circulating immune cells (white blood cell, lymphocyte, and monocyte counts), and BT to MLNs in 21 patients undergoing abdominal surgery because of intestinal obstruction. We also examined whether BT correlated with the development of perioperative systemic inflammatory response syndrome (SIRS) and postoperative septic complications.

RESULTS

BT subsequent to intestinal obstruction was observed in 7 (33%) patients. Preoperative circulating immune cell counts were significantly lower in BT-positive patients than those in BT-negative patients. The presence of preoperative SIRS was also significantly related to BT-positive status. A preoperative monocyte count <290/mm(3) was the best predictive factor for BT in MLNs during intestinal obstruction: sensitivity 85.7%; specificity 92.3%; positive and negative predictive values 85.7% and 92.9%, respectively. The area under the receiver operating characteristic curve was 0.944. The expression of S-100 protein-positive DCs in MLNs significantly increased in BT-positive patients.

CONCLUSIONS

A significant inverse correlation was observed between the circulating monocyte count and the ratio of DCs among all cells in MLNs (r(2)= 0.259). Postoperative septic complications were 3.3 times more common in BT-positive patients than in BT-negative patients. A significant increase in the expression of DCs in MLNs was observed in patients with BT subsequent to intestinal obstruction. Our findings suggested that a low monocyte count (<290 /mm(3)) and the presence of preoperative SIRS might be useful factors for predicting BT in patients with intestinal obstruction.

Staphylococcus aureus peptidoglycan impairs fracture healing: an experimental study in rats

Staphylococcus aureus is the common organism causing musculoskeletal infections. Staphylococcus aureus peptidoglycan (SaPG) has been identified to increase the acute inflammatory response to wounding, increase reparative granulation tissue, and improve healing. The healing of bone fractures is a balanced process of granulation tissue that is calcified to obtain increasing stability. By increasing reparative collagen accumulation, however, SaPG may induce a shift towards immature fibrous callus production. Therefore, it was our hypothesis that SaPG would impair bone healing after fracture. In three groups, each of nine rats, a mid-diaphyseal osteotomy/fracture of the femoral bone was performed and then nailed. In one group of animals, SaPG was applied locally at the fracture site, and in another group SaPG was applied intraperitoneally (systemically). Control littermate received saline. The animals were sacrificed after 6 weeks, and the mechanical characteristics of the healing osteotomies were evaluated. We found that application of SaPG locally induced a hypertrophic and immature callus as evaluated by callus production, by bone mineral content and density, and by bending moment and rigidity. In the rats given SaPG intraperitoneally, bone healing went uneventful compared to the control rats. Collectively, these data show that SaPG induces an alteration in the normal bone healing response towards a less calcified callus production.

Peptidoglycan--an endotoxin in its own right?

Studies aimed at dissecting the complex pathophysiology of sepsis with multiple organ failure have traditionally focused on lipopolysaccharide of gram-negative bacteria, which is widely regarded as the classical endotoxin. However, gram-positive sepsis now accounts for up to 50% of all cases, calling for a shift of focus. Peptidoglycan (PepG) is the major cell wall component of gram-positive bacteria and has been increasingly recognized as an important proinflammatory molecule. During gram-positive infections, PepG reaches the circulation by bacterial breakdown or translocation from the intestine. Administration of PepG induces all the classical features of infectious illness and endotoxemia and may cause systemic inflammation with organ failure in animal models. Its potency, however, is crucially dependent on various features of its complex structure. PepG interacts with the innate immune system through receptors mainly expressed on monocytes/macrophages but may induce inflammatory changes in other cell types as well. Among the most extensively studied receptor systems are the nucleotide-binding oligomerization domains, the toll-like receptors, and the PepG recognition proteins. Based on the current available literature, we would like to propose that PepG must be regarded as an endotoxin in its own right and to encourage further work in the field of PepG signaling.