Appendiceal microbiome in uncomplicated and complicated acute appendicitis: A prospective cohort study

The microbiome of the appendix differs in patients with and without appendicitis: A prospective cohort study

BACKGROUND

Appendicitis seems to be a disease of infectious origin, but the detailed pathogenesis is unknown. We aimed to investigate the microbiome of the appendix lumen in patients with and without appendicitis, including a comparison of the subgroups of complicated versus uncomplicated appendicitis.

METHODS

This prospective observational cohort study included adult patients undergoing laparoscopic appendectomy for suspected appendicitis. According to histopathologic findings, the investigated groups consisted of patients with and without appendicitis, including subgroups of complicated versus uncomplicated appendicitis based on the surgical report. A swab of the appendix lumen was analyzed for genetic material from bacteria with shotgun metagenomics, and outcomes included analyses of microbiome diversity and differential abundance of bacteria.

RESULTS

A total of 53 swabs from patients with suspected appendicitis were analyzed: 42 with appendicitis (16 complicated) and 11 without appendicitis. When comparing patients with and without appendicitis, they were equally rich in bacteria (alpha diversity), but the microbiome composition was dissimilar between these groups (beta diversity) (P < .01). No consistent bacterial species were detected in all patients with appendicitis, but a least 3 genera (Blautia, Faecalibacterium, and Fusicatenibacter) and 2 species, Blautia faecis and Blautia wexlerae, were more abundant in patients without appendicitis. For the subgroups complicated versus uncomplicated appendicitis, both measures for microbiome diversity were similar.

CONCLUSION

The appendix microbiome composition of genetic material from bacteria in adult patients with and without appendicitis differed, but the microbiome was similar for patients with complicated versus uncomplicated appendicitis. Trial registration NCT03349814.

Three-Year Outcomes of Oral Antibiotics vs Intravenous and Oral Antibiotics for Uncomplicated Acute Appendicitis: A Secondary Analysis of the APPAC II Randomized Clinical Trial

Importance

Current short-term evidence has shown that uncomplicated acute appendicitis can be treated successfully with oral antibiotics alone, but longer-term results are lacking.

Objective

To assess the treatment effectiveness of oral antibiotic monotherapy compared with combined intravenous (IV) and oral antibiotics in computed tomography-confirmed uncomplicated acute appendicitis at a longer-term follow-up.

Design, Setting, and Participants

This secondary analysis of a predefined year 3 follow-up of the Appendicitis Acuta II (APPAC II) noninferiority, multicenter randomized clinical trial compared oral moxifloxacin with combined IV ertapenem plus oral levofloxacin and metronidazole for the treatment of uncomplicated acute appendicitis. The trial was conducted at 9 university and central hospitals in Finland from April 2017 to November 2018, with the last follow-up in November 2022. Participants included patients aged 18 to 60 years, who were randomized to receive either oral antibiotics monotherapy (n = 301) or combined IV and oral antibiotics (n = 298).

Interventions

Antibiotics monotherapy consisted of oral moxifloxacin, 400 mg/d, for 7 days. Combined IV and oral antibiotics consisted of IV ertapenem sodium, 1 g/d, for 2 days plus oral levofloxacin, 500 mg/d, and metronidazole, 500 mg 3 times/d, for 5 days.

Main Outcomes and Measures

The primary end point was treatment success, defined as the resolution of acute appendicitis and discharge from hospital without the need for surgical intervention and no appendicitis recurrence at the year 3 follow-up evaluated using a noninferiority design. The secondary end points included late (after 1 year) appendicitis recurrence as well as treatment-related adverse events, quality of life, length of hospital stay, and length of sick leave, which were evaluated using a superiority design.

Results

After exclusions, 599 patients (mean [SD] age, 36 [12] years; 336 males [56.1%]) were randomized; after withdrawal and loss to follow-up, 582 patients (99.8%) were available for the year 3 follow-up. The treatment success at year 3 was 63.4% (1-sided 95% CI, 58.8% to ∞) in the oral antibiotic monotherapy group and 65.2% (1-sided 95% CI, 60.5% to ∞) in the combined IV and oral antibiotics group. The difference in treatment success rate between the groups at year 3 was -1.8 percentage points (1-sided 95% CI, -8.3 percentage points to ∞; P = .14 for noninferiority), with the CI limit exceeding the noninferiority margin. There were no significant differences between groups in treatment-related adverse events, quality of life, length of hospital stay, or length of sick leave.

Conclusions and Relevance

This secondary analysis of the APPAC II trial found a slightly higher appendectomy rate in patients who received oral antibiotic monotherapy; however, noninferiority of oral antibiotic monotherapy compared with combined IV and oral antibiotics could not be demonstrated. The results encourage future studies to assess oral antibiotic monotherapy as a viable treatment alternative for uncomplicated acute appendicitis.

Trial Registration

ClinicalTrials.gov Identifier: NCT03236961.

Compilation of Evidence Supporting the Role of a T Helper 2 Reaction in the Pathogenesis of Acute Appendicitis

Despite being the most common abdominal surgical emergency, the cause of acute appendicitis (AA) remains unclear, since in recent decades little progress has been made regarding its etiology. Obstruction of the appendicular lumen has been traditionally presented as the initial event of AA; however, this is often the exception rather than the rule, as experimental data suggest that obstruction is not an important causal factor in AA, despite possibly occurring as a consequence of the inflammatory process. Type I hypersensitivity reaction has been extensively studied, involving Th2 lymphocytes, and cytokines such as IL-4, IL-5, IL-9 and IL-13, which have well-defined functions, such as a positive-feedback effect on Th0 for differentiating into Th2 cells, recruitment of eosinophils and the release of eosinophilic proteins and the production of IgE with the activation of mast cells, with the release of proteins from their granules. Cytotoxic activity and tissue damage will be responsible for the clinical manifestation of the allergy. AA histological features are similar to those found in allergic reactions like asthma. The intestine has all the components for an allergic immune response. It has contact with hundreds of antigens daily, most of them harmless, but some can potentially induce an allergic response. In recent years, researchers have been trying to assess if allergy is a component of AA, with their latest advances in the understanding of AA as a Th2 reaction shown by the authors of this article.

Intraoperative bacterial cultures fail to reliably predict the bacterial spectrum encountered during infectious complications after appendicitis

Acute appendicitis is a common surgical emergency. Complicated appendicitis usually warrants perioperative antibiotic treatment in order to prevent infectious complications. Whether routine microbiological testing benefits the individual patient is a topic of debate. The goal of our study was to assess perioperative antibiotic prescriptions as well as the benefit of microbiological testing during the appendectomy as a predictor for bacteria encountered in infectious complications. This is a retrospective analysis of 1218 consecutive patients that underwent appendectomy at a tertiary referral center between 2014 and 2021. The patient charts were systematically analyzed regarding intraoperative outcome, microbiologic results, and postoperative infectious complications. 1218 patients were included in this study of which 768 were uncomplicated appendicitis (UA) and 450 were complicated appendicitis (CA). Microbiological testing was performed in 39.2% of UA cases (33.6% of which grew bacteria) compared to 74.9% of CA cases (78.6% positive cultures). The strongest individual predictors for SSI were gangrenous and perforated appendicitis. A total of 58 surgical-site infections developed, of which 49 were intra-abdominal fluid collections or abscesses. Thirty-two patients had revision surgery or CT-guided drainage for SSI. In the cases where microbiological testing was done both during the appendectomy and the SSI, 13/18 showed different bacteria on culture testing. The infectious outcome was favorable in 98.3%. While microbiological testing offers insights into resistance patterns, it is of little benefit for the individual patient, given the low predictive value for bacteria found during SSI. Achieving source control combined with empiric antibiotic coverage leads to favorable outcomes independent of culture results.

Trends in Simple and Complex Appendicitis in Children and the Potential Correlation to Common Viral Pathogens-A Retrospective Cohort Study between 2010 and 2019 in The Netherlands

The aim of this study was to evaluate the annual, seasonal and monthly trends in children with simple and complex appendicitis and their correlation to common viral pathogens in the Netherlands. A consecutive multicenter retrospective cohort study was performed between 2010 and 2019 including children (<18 years) surgically treated for appendicitis. The primary outcome was the distribution of children with simple and complex appendicitis per year, season and month. Relevant seasonal variation was defined as ≥5%. The secondary outcome was a positive correlation of the number of patients with simple and complex appendicitis to common viral pathogens (data anonymously provided by the Dutch Working Group on Clinical Virology from the Dutch Society for Clinical Microbiology (NVMM)). In total, 896 patients were included: N = 524 (58%) patients with simple and N = 372 (42%) with complex appendicitis. Of the children aged 0-5 years, 81% had complex appendicitis, versus 38% in 6-18 years (p < 0.001). An overall decline was demonstrated for both simple and complex appendicitis between 2010 and 2019. No seasonal variation was found for simple appendicitis. For complex appendicitis, the highest number of patients was found in spring, and lowest in summer (N = 372, spring 28.2 ± 5.1% versus summer 21.0 ± 5.8%, p = 0.011), but the variance was regarded as not relevant (<5% from baseline). A positive correlation was found between complex appendicitis with Adenovirus 40.41 (R = 0.356, 95%CI 0.045-0.604, p = 0.026) and simple appendicitis with Adenovirus NON 40.41 (R = 0.332, 95%CI 0.019-0.586, p = 0.039), but these correlations did not remain significant after a Bonferroni correction (p < 0.003). In conclusion, we found no relevant seasonal variation for simple or complex appendicitis, nor positive correlation with common viral pathogens.

Eosinophil Granule Proteins Involvement in Acute Appendicitis-An Allergic Disease?

Several pieces of evidence point to an allergic component as a trigger of acute appendicitis. As the Th2 immune response is characterized by eosinophil mobilization to the target organ and release of their cationic granule proteins, it is reasonable to investigate if the degranulation of eosinophils could be associated with the local injury. The primary aim of this study is to evaluate the participation of eosinophils granules proteins in acute appendicitis, both at local and systemic levels and the secondary aim is to evaluate the diagnostic accuracy of eosinophils granules proteins for the detection of acute appendicitis, as well as for distinguishing between complicated and uncomplicated acute appendicitis. Eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP) and eosinophil peroxidase (EP) are the most well-known eosinophil granule proteins. From August 2021 to April 2022, we present a prospective single-center study to evaluate the EDN, ECP, and EP concentrations simultaneously in appendicular lavage fluid (ALF) and the serum of 22 patients with acute phlegmonous appendicitis (APA), 24 with acute gangrenous appendicitis (AGA), and 14 normal controls. Concerning EDN, no differences were found between groups. ECP concentrations in ALF and serum were significantly higher in the histologically confirmed acute appendicitis compared to the control groups (p < 0.0001 and p < 0.0001, respectively). In ALF, no differences were found between ECP levels in APA: 38.85 ng/mL (IQR 26.50-51.77) and AGA 51.55 ng/mL (IQR 39.55-70.09) groups (p = 0.176). In the serum, no difference was found between ECP levels at APA: 39 ng/mL (IQR 21.30-56.90) and AGA: 51.30 ng/mL (IQR 20.25-62.59) (p = 0.100). For EP, the concentrations in ALF (p < 0.001) and serum (p < 0.001) were both higher in acute appendicitis compared to the control. In ALF, no difference was found between APA: 240.28 ng/mL (IQR 191.2-341.3) and AGA: 302.5 (IQR 227.7-535.85) (p = 0.236). In the serum, no differences were found between APA: 158.4 ng/mL (IQR 111.09-222.1) and AGA: 235.27 (IQR 192.33-262.51) (p = 0.179). Globally, the ALF concentrations were higher than serum concentrations, reflecting an intense inflammatory local reaction in AA. The optimal ECP cut-off for discriminating between acute appendicitis and the controls was >11.41 ng/mL, with a sensitivity of 93.5%, but with a specificity for identifying appendicitis of 21.4%, good discriminative power (AUC = 0.880). For EP, the optimal cut-off was >93.20 ng/mL, with a sensitivity of 87%, but with a specificity of 14.3% (AUC = 0.901), excellent discriminative power. For the diagnosis of perforated AA, the discriminative power of ECP and EP serum concentrations are weak (AUC = 0.562 and AUC = 0.664, respectively). Concerning the presence of peritonitis, the discriminative power of ECP and EP serum concentrations is acceptable, respectively: AUC = 0.724 and AUC = 0.735. Serum levels of EDN (p = 0.119), ECP (p = 0.586) and EP (p = 0.08) in complicated appendicitis were similar to uncomplicated appendicitis. Serum concentrations of ECP and EP can be added to decision-making AA diagnosis. A Th2-type immune response is present in AA. These data bring forward the role of an allergic reaction in the pathogenesis of acute appendicitis.

Infection or Inflammation: Are Uncomplicated Acute Appendicitis, Acute Cholecystitis, and Acute Diverticulitis Infectious Diseases?

Background: It is recognized increasingly that common surgical infections of the peritoneal cavity may be treated with antibiotic agents alone, or source control surgery with short-course antimicrobial therapy. By extension, testable hypotheses have emerged that such infections may not actually be infectious diseases, but rather represent inflammation that can be treated successfully with neither surgery nor antibiotic agents. The aim of this review is to examine extant data to determine which of uncomplicated acute appendicitis (uAA), uncomplicated acute calculous cholecystitis (uACC), or uncomplicated mild acute diverticulitis (umAD) might be amenable to management using supportive therapy alone, consistent with the principles of antimicrobial stewardship. Methods: Review of pertinent English-language literature and expert opinion. Results: Only two small trials have examined whether uAA can be managed with observation and supportive therapy alone, one of which is underpowered and was stopped prematurely because of challenging patient recruitment. Data are insufficient to determine the safety and efficacy of non-antibiotic therapy of uAA. Uncomplicated acute calculous cholecystitis is not primarily an infectious disease; infection is a secondary phenomenon. Even when bactibilia is present, there is no high-quality evidence to suggest that mild disease should be treated with antibiotic agents. There is evidence to indicate that antibiotic prophylaxis is indicated for urgent/emergency cholecystectomy for uACC, but not in the post-operative period. Uncomplicated mild acute diverticulitis, generally Hinchey 1a or 1b in current nomenclature, does not benefit from antimicrobial agents based on multiple clinical studies. The implication is that umAD is inflammatory and not an infectious disease. Non-antimicrobial management is reasonable. Conclusions: Among the considered disease entities, the evidence is strongest that umAD is not an infectious disease and can be treated without antibiotic agents, intermediate regarding uACC, and lacking for uAA. A plausible hypothesis is that these inflammatory conditions are related to disruption of the normal microbiome, resulting in dysbiosis, which is defined as an imbalance of the natural microflora, especially of the gut, that is believed to contribute to a range of conditions of ill health. As for restorative pre- or probiotic therapy to reconstitute the microbiome, no recommendation can be made in terms of treatment, but it is not recommended for prevention of primary or recurrent disease.

The Gut Microbiome of Children during the COVID-19 Pandemic

The gut microbiome has been shown to play a critical role in maintaining a healthy state. Dysbiosis of the gut microbiome is involved in modulating disease severity and potentially contributes to long-term outcomes in adults with COVID-19. Due to children having a significantly lower risk of severe illness and limited sample availability, much less is known about the role of the gut microbiome in children with COVID-19. It is well recognized that the developing gut microbiome of children differs from that of adults, but it is unclear if this difference contributes to the different clinical presentations and complications. In this review, we discuss the current knowledge of the gut microbiome in children with COVID-19, with gut microbiome dysbiosis being found in pediatric COVID-19 but specific taxa change often differing from those described in adults. Additionally, we discuss possible mechanisms of how the gut microbiome may mediate the presentation and complications of COVID-19 in children and the potential role for microbial therapeutics.