Aeromonas sobria sepsis complicated by rhabdomyolysis in an HIV-positive patient: case report and evaluation of traits associated with bacterial virulence

EspP2 Regulates the Adhesion of Glaesserella parasuis via Rap1 Signaling Pathway

Different levels of EspP2 expression are seen in strains of Glaesserella parasuis with high and low pathogenicity. As a potential virulence factor for G. parasuis, the pathogenic mechanism of EspP2 in infection of host cells is not clear. To begin to elucidate the effect of EspP2 on virulence, we used G. parasuis SC1401 in its wild-type form and SC1401, which was made EspP2-deficient. We demonstrated that EspP2 causes up-regulation of claudin-1 and occludin expression, thereby promoting the adhesion of G. parasuis to host cells; EspP2-deficiency resulted in significantly reduced adhesion of G. parasuis to cells. Transcriptome sequencing analysis of EspP2-treated PK15 cells revealed that the Rap1 signaling pathway is stimulated by EspP2. Blocking this pathway diminished occludin expression and adhesion. These results indicated that EspP2 regulates the adhesion of Glaesserella parasuis via Rap1 signaling pathway.

Aeromonas and Human Health Disorders: Clinical Approaches

The genus Aeromonas comprises more than 30 Gram-negative bacterial species and naturally inhabitants from aquatic environments. These microorganisms, commonly regarded as pathogens of fish and several other animals, have been gaining prominence on medical trial due to its ability to colonize and infect human beings. Besides water, Aeromonas are widely spreaded on most varied sources like soil, vegetables, and food; Although its opportunistic nature, they are able to cause infections on immunocompromised or immunocompetent patients. Aeromonas species regarded as potential human pathogens are usually A. hydrophila, A. caviae, and A. veronii biovar sobria. The main clinical manifestations are gastrointestinal tract disorders, wound, and soft tissue infections, as well as septicemia. Regarding to antibiotic responses, the bacteria present a diversified susceptibility profile and show inherence resistance to ampicillin. Aeromonas, as an ascending genus in microbiology, has been carefully studied aiming comprehension and development of methods for detection and medical intervention of infectious processes, not fully elucidated in medicine. This review focuses on current clinical knowledge related to human health disorders caused by Aeromonas to contribute on development of efficient approaches able to recognize and impair the pathological processes.

Clinical characteristics and risk factors of Aeromonas bloodstream infections in patients with hematological diseases

BACKGROUND

To analyze the clinical features, risk factors and outcomes of Aeromonas bloodstream infections (BSIs) in patients with hematological diseases to establish an effective optimal therapy against it.

METHODS

A retrospective study was performed by reviewing medical records of patients admitted to a tertiary blood disease hospital in China. Patients with hematological diseases who suffered from Aeromonas bacteremia during January 2002 to December 2020 were enrolled in this study.

RESULTS

A total of 63 patients who developed Aeromonas bacteremia were enrolled in the study, and 91.9% of patients were neutropenic at the onset of BSIs. The major complications were skin and soft tissue infection (SSTI) (22.2%), followed by gastroenteritis (19.0%) and pneumonia (14.3%). High carbapenem resistance rates (70.8% for imipenem, 71.4% for meropenem) were note among the cases. Furthermore, Aeromonas strains isolated from five individuals developed resistance to quinolone, β-lactams and tigecycline during the therapy. The 30-day mortality rate was 15.9%, while bacteremia with SSTI showed a much worse prognosis, with 50.0% (7/14) of the patients dying within 30 days of initiating the therapy. In the multivariate analysis, SSTI (OR = 28.72; 95% CI, 1.50-551.30; P = 0.026) and shock (OR = 47.58; 95% CI,1.06-2126.80; P = 0.046) were independent risk factors for mortality.

CONCLUSIONS

Aeromonas bacteremia usually occurred in patients with neutropenic status, and patients with SSTIs were more likely to show a worse prognosis. Carbapenems should be avoided in patients with Aeromonas BSIs and SSTIs given high resistance rate.

Aeromonas sobria Induces Proinflammatory Cytokines Production in Mouse Macrophages via Activating NLRP3 Inflammasome Signaling Pathways

Aeromonas sobria, a common conditional pathogenic bacteria, is widely distributed in the environment and causes gastroenteritis in humans or septicemia in fish. Of all Aeromonas species, A. sobria is the most frequently isolated from human infections especially in immunocompromised subjects. Innate immunity is the first protection system of organism to resist non-specific pathogens invasion; however, the immune response process of hosts against A. sobria infection re\mains unexplored. The present study established an A. sobria infection model using primary mouse peritoneal macrophages (PMφs). The adherence and cytotoxicity of A. sobria on PMφs were determined by May-Grünwald Giemsa staining and LDH release measurement. Pro-inflammatory cytokine expression levels were measured using qPCR, western blotting, and ELISA methods. We also investigated the levels of ASC oligomerization and determined the roles of active caspase-1 in IL-1β secretion through inhibition assays and explored the activated pattern recognition receptors through immunofluorescence. We further elucidated the roles of activated inflammasome in regulating the host's inflammatory response through inhibition combined with ELISA assays. Our results showed that A. sobria induced lytic cell death and LDH release, whereas it had no adhesive properties on PMφs. A. sobria triggered various proinflammatory cytokine transcription level upregulation, and IL-1β occupied the highest levels. The pro-IL-1β protein expression levels increased in a dose-dependent manner with MOI ranging from 1 to 100. This process was regulated by ASC-dependent inflammasome, which cleavage pro-IL-1β into active IL-1β p17 with activated caspase-1 p20. Meanwhile, the expression levels of NLRP3 receptor significantly increased, location analysis revealed puncta-like surrounding nuclear, and inhibition of NLRP3 inflammasome downregulated caspase-1 activation and IL-1β secretion. Blocking of NLRP3 inflammasome activation through K⁺ efflux and cathepsin B or caspase approaches downregulated A. sobria-induced proinflammatory cytokine production. Overall, these data indicated that A. sobria induced proinflammatory cytokine production in PMφs through activating NLRP3 inflammasome signaling pathways.

Clinical features and outcome of Aeromonas sobria bacteremia in pediatric and adult patients with hematologic malignancies: A single-center retrospective study in Peru

Background

Previous studies have found that healthcare-associated bacteremia (HAB) by Aeromonas species is associated with mortality. However, there is limited data on this outcome in patients with hematologic malignancies. This study aimed to identify the clinical features of patients with malignant hematologic diseases diagnosed with Aeromonas sobria bacteremia and to evaluate whether the type of bacteremia, community-acquired bacteremia (CAB) or HAB, is associated with mortality.

Methods

We retrospectively reviewed the clinical records of pediatric and adult patients between January 2000 and December 2017. Clinical characteristics were compared between CAB and HAB. Additionally, we stratified based on age group. Survival outcomes were assessed with Kaplan-Meier curves and a multivariate Cox regression analysis.

Results

A total of 37 patients (median age 24 years) were identified; 23 (62%) had HAB and 14 (38%) had CAB. Overall, the most common presenting symptom was abdominal pain (41%). Acute lymphoblastic leukemia (n = 12/15, 80%) and acute myeloid leukemia (n = 8/22, 36%) were the primary hematologic malignancies in pediatric and adult patients, respectively. CAB patients had worse overall survival (OS) rates at 30 days in all (43% versus HAB 91%, p = 0.006) and adult patients (30% versus HAB 92%, p = 0.002). Cox regression analysis found that quick Sequential Organ Failure Assessment and CAB were statistically significant factors associated with mortality. Low antimicrobial-resistant was noted, except for ciprofloxacin (n = 5/37, 14%).

Conclusion

Our study found a worse OS among patients with hematologic malignancies and CAB by Aeromonas sobria. Our results suggest that patients with CAB present with a worse disease severity. These findings should aid clinicians to determine the survival prognosis in this population.

A Klebsiella pneumoniae liver abscess presenting with myasthenia and tea-colored urine: A case report and review of 77 cases of bacterial rhabdomyolysis

RATIONALE

Rhabdomyolysis is a well-known syndrome in clinical practice, although rhabdomyolysis caused by a liver abscess is rarely reported and the patient may lack symptoms that are associated with a primary site of infection. Early recognition of this possibility is needed to avoid diagnostic delay and facilitate treatment. We report the case of a 71-year-old woman with a Klebsiella pneumoniae (KP) pyogenic liver abscess who presented with myasthenia and tea-colored urine and also review the 77 reported cases of bacterial rhabdomyolysis.

PATIENT CONCERNS

The patient was 71 years old and presenting with a 7-day history of myasthenia and a 3-day history of tea-colored urine, but without fever or abdominal pain.

DIAGNOSES

Laboratory testing in our case revealed rhabdomyolysis, and blood culture revealed KP. Abdominal ultrasonography revealed a hypoechoic enclosed mass, and computed tomography (CT) revealed an enclosed low-density mass (8.3 × 6.6 × 6.1 cm). The main diagnoses were a pyogenic liver abscess with rhabdomyolysis.

INTERVENTIONS

Empirically intravenous piperacillin-sulbactam and intravenous potassium treatment, as well as fluid infusions and other supportive treatments were provided after admission. After the diagnosis was confirmed and susceptibility test results were available, we adjusted the antibiotics to cefoperazone and sulbactam, which were maintained for 6 weeks.

OUTCOMES

The patient's symptoms relieved and the abnormal laboratory parameters corrected. Follow-up abdominal ultrasonography at 24 months after her discharge revealed that the abscess had disappeared.

LESSONS

Early recognition and careful consideration of the underlying cause of rhabdomyolysis are critical to improving the patient's prognosis. Thus, physicians should carefully consider the underlying cause in elderly patients who present with rhabdomyolysis, as they may lack symptoms of a primary infection.

Aeromonas wound infection in a healthy boy, and wound healing with polarized light

Introduction. At emergency departments, history taking is often very brief. We present a case of an Aeromonas wound infection, that illustrates the importance of careful history taking. We also report the first successful use of polarized light as additional therapy for healing of this infectious wound.

Case presentation. A healthy boy was diagnosed with a wound infection, after a fall onto rocks. At first, it remained unmentioned that there had been contact with ditchwater, so he was treated with amoxicillin-clavulanic acid. Only after the finding of an Aeromonas strain in the wound culture, and treatment with a fluoroquinolone, did he recover. Wound healing was aided with the use of polarized light, and with good effect. To our knowledge, this is the first report on the effect of polarized light on the healing of infectious wounds.

Conclusion. Careful history taking is essential for adequate empiric therapy when faced with wounds and wound infections. Aeromonas infections are associated with water exposure, and should be treated with fluoroquinolones. Polarized light seems to have a good result on healing of infectious wounds.

Involvement of Acylated Homoserine Lactones (AHLs) of Aeromonas sobria in Spoilage of Refrigerated Turbot (Scophthalmus maximus L.)

One quorum sensing strain was isolated from spoiled turbot. The species was determined by 16S rRNA gene analysis and classical tests, named Aeromonas sobria AS7. Quorum-sensing (QS) signals (N-acyl homoserine lactones (AHLs)) were detected by report strains and their structures were further determined by GC-MS. The activity changes of AHLs on strain growth stage as well as the influence of different culture conditions on secretion activity of AHLs were studied by the punch method. The result indicated that strain AS7 could induce report strains to produce typical phenotypic response. N-butanoyl-dl-homoserine lactone (C₄-HSL), N-hexanoyl-dl-homoserine lactone (C₆-HSL), N-octanoyl-dl-homoserine lactone (C₈-HSL), N-decanoyl-dl-homoserine lactone (C10-HSL), N-dodecanoyl-dl-homoserine lactone (C12-HSL) could be detected. The activities of AHLs were density-dependent and the max secretion level was at pH 8, sucrose culture, 1% NaCl and 32 h, respectively. The production of siderophore in strain AS7 was regulated by exogenous C₈-HSL, rather than C₆-HSL. Exogenous C₄-HSL and C₈-HSL accelerated the growth rate and population density of AS7 in turbot samples under refrigerated storage. However, according to the total viable counts and total volatile basic nitrogen (TVB-N) values of the fish samples, exogenous C₆-HSL did not cause spoilage of the turbot fillets. In conclusion, our results suggested that QS was involved in the spoilage of refrigerated turbot.

Molecular Cloning and Functional Characterization of Mannose Receptor in Zebra Fish (Danio rerio) during Infection with Aeromonas sobria

Mannose receptor (MR) is a member of pattern-recognition receptors (PRRs), which plays a significant role in immunity responses. Much work on MR has been done in mammals and birds while little in fish. In this report, a MR gene (designated as zfMR) was cloned from zebra fish (Danio rerio), which is an attractive model for the studies of animal diseases. The full-length cDNA of zfMR contains 6248 bp encoding a putative protein of 1428 amino acids. The predicted amino acid sequences showed that zfMR contained a cysteine-rich domain, a single fibronectin type II (FN II) domain, eight C-type lectin-like domains (CTLDs), a transmembrane domain and a short C-terminal cytoplasmic domain, sharing highly conserved structures with MRs from the other species. The MR mRNA could be detected in all examined tissues with highest level in kidney. The temporal expression patterns of MR, IL-1β and TNF-α mRNAs were analyzed in the liver, spleen, kidney and intestine post of infection with Aeromonas sobria. By immunohistochemistry assay, slight enhancement of MR protein was also observed in the spleen and intestine of the infected zebra fish. The established zebra fish-A. sobria infection model will be valuable for elucidating the role of MR in fish immune responses to infection.

Aeromonas sobria necrotizing fasciitis and sepsis in an immunocompromised patient: a case report and review of the literature

Introduction

Aeromonas veronii biovar sobria is a rare cause of bacteremia, with several studies indicating that this isolate may be of particular clinical significance since it is enterotoxin producing. A wide spectrum of infections has been associated with Aeromonas species in developing countries that include gastroenteritis, wound infections, septicemia and lung infections. This infection, caused by Aeromonas species, is usually more severe in immunocompromised than immunocompetent individuals. We here describe a case of soft tissue infection and severe sepsis due to Aeromonas sobria in an immunocompromised patient.

Case presentation

A 74-year-old Caucasian man with a clinical history of chronic lymphocytic leukemia and immune thrombocytopenia, periodically treated with steroids, was admitted to our Intensive Care Unit because of necrotizing fasciitis and multiorgan failure due to Aeromonas sobria, which resulted in his death. The unfortunate coexistence of a Candida albicans infection played a key role in the clinical course.

Conclusion

Our experience suggests that early recognition and aggressive medical and surgical therapy are determinants in the treatment of severe septicemia caused by an Aeromonas sobria in an immunocompromised patient.