Life after meningitis: a qualitative study exploring survivors' experience of living with sequelae.

BACKGROUND: Around twenty percent of meningitis survivors experience after-effects. However, very little research on their psychological impact has been conducted. This report details a small explorative investigation into these psychological impacts. OBJECTIVE: To explore the impact sequelae have on the meningitis survivors affected. METHODS AND MEASURES: Thematic analysis of one-hundred individual user's blog posts, self-reporting one or more sequelae after a diagnosis of meningitis. RESULTS: Blog posters' experiences varied greatly. Common trends in experience were mapped onto three themes. 'Struggling to Adjust to the New Normal' captures blog posters' struggles in returning to their lives post-hospitalization. 'Navigating Possibilities for Positivity' explores how blog posters either reported positive change due to their illness experience or felt a pressure, or inability, to do so. 'The Impact of Knowledge and Support' overarching two sub-themes; 'Lack of Awareness Causing Further Suffering' and 'Validation Leads to Narrative Shift'. These sub-themes contrast differences in experience blog posters reported, with and without knowledge, of the cause of their symptoms and support in dealing with the resulting difficulties. CONCLUSIONS: Consistent and structured after-care would benefit patients experiencing sequelae. Suggestions of a possible format this could take are put forward. In addition, self-regulatory models of illness perception help explain some variations in blog posters experiences, with possible intervention plans based on these models also suggested. However, limitations, including the comparatively small and highly selected sample, mean that further research is necessary to validate the findings and assess their validity, widespread applicability, and financial feasibility.

Molecular Markers and Antimicrobial Resistance Patterns of Extraintestinal Pathogenic Escherichia coli from Camel Calves Including Colistin-Resistant and Hypermucoviscuous Strains.

Extraintestinal pathogenic Escherichia coli (ExPEC) strains are capable of causing various systemic infections in both humans and animals. In this study, we isolated and characterized 30 E. coli strains from the parenchymatic organs and brains of young (<3 months of age) camel calves which died in septicemia. Six of the strains showed hypermucoviscous phenotype. Based on minimum inhibitory concentration (MIC) values, seven of the strains were potentially multidrug resistant, with two additional showing colistin resistance. Four strains showed mixed pathotypes, as they carried characteristic virulence genes for intestinal pathotypes of E. coli: three strains carried cnf1, encoding cytotoxic necrotizing factor type 1, the key virulence gene of necrotoxigenic E. coli (NTEC), and one carried eae encoding intimin, the key virulence gene of enteropathogenic E. coli (EPEC). An investigation of the integration sites of pathogenicity islands (PAIs) and the presence of prophage-related sequences showed that the strains carry diverse arrays of mobile genetic elements, which may contribute to their antimicrobial resistance and virulence patterns. Our work is the first to describe ExPEC strains from camels, and points to their veterinary pathogenic as well as zoonotic potential in this important domestic animal.

Developing a PmSLP3-based vaccine formulation that provides robust long-lasting protection against hemorrhagic septicemia-causing serogroup B and E strains of Pasteurella multocida in cattle.

Background: Pasteurella multocida is a bacterial pathogen that causes a variety of infections across diverse animal species, with one of the most devastating associated diseases being hemorrhagic septicemia. Outbreaks of hemorrhagic septicemia in cattle and buffaloes are marked by rapid progression and high mortality. These infections have particularly harmful socio-economic impacts on small holder farmers in Africa and Asia who are heavily reliant on a small number of animals kept as a means of subsistence for milk and draft power purposes. A novel vaccine target, PmSLP-3, has been identified on the surface of hemorrhagic septicemia-associated strains of P. multocida and was previously shown to elicit robust protection in cattle against lethal challenge with a serogroup B strain. Methods: Here, we further investigate the protective efficacy of this surface lipoprotein, including evaluating the immunogenicity and protection upon formulation with a variety of adjuvants in both mice and cattle. Results: PmSLP-3 formulated with Montanide ISA 61 elicited the highest level of serum and mucosal IgG, elicited long-lasting serum antibodies, and was fully protective against serogroup B challenge. Studies were then performed to identify the minimum number of doses required and the needed protein quantity to maintain protection. Duration studies were performed in cattle, demonstrating sustained serum IgG titres for 3 years after two doses of vaccine and full protection against lethal serogroup B challenge at 7 months after a single vaccine dose. Finally, a serogroup E challenge study was performed, demonstrating that PmSLP-3 vaccine can provide protection against challenge by the two serogroups responsible for hemorrhagic septicemia. Conclusion: Together, these data indicate that PmSLP-3 formulated with Montanide ISA 61 is an immunogenic and protective vaccine against hemorrhagic septicemia-causing P. multocida strains in cattle.

The effect of polyclonal and monoclonal based antibodies as promising potential therapy for treatment of sepsis: A systematic review.

While mortality caused by sepsis remains an unsolved problem, studies showed conflicting results about effectiveness of monoclonal and polyclonal antibodies in patients suffering sepsis. For this reason, this current study provides an update of review clinical randomized trial studies until March 2024. The main object of this study is to determine effects of monoclonal and polyclonal antibodies on mortality rate and hospitalization of patients suffering sepsis. Search of Scopus, Web of science, EMBASE, PubMed and Cochrane were performed and randomized controlled trials which conducted in patients with septic shock or bacterial sepsis were included. Two reviewers assessed all searched trials for eligibility according to already defined criteria and did data collection and analyses afterwards. Present study showed monoclonal and polyclonal antibodies are a safe strategy with mild-to-moderate adverse effects. However, most studies indicate no significant change among inter-and intra-group comparison (p > 0.05) and further studies are needed, results showed an increase in survival rate, ventilator-and ICU-free days, resolve organ dysfunction, mediating inflammation related cytokines.

Development of two multiplex PCR assays for rapid detection of eleven Gram-negative bacteria in children with septicemia.

AIM: This study aimed to develop a multiplex PCR assay for simultaneous detection of major Gram-negative etiologies of septicemia and evaluate its performance. METHODS: Multiplex PCR (mPCR) assays were developed targeting 11 bacterial strains. Species-specific primers were confirmed using known clinical isolates and standard strains. Gradient PCR was performed on each primer against its target bacterial gene to determine its optimal amplification condition. The minimum detectable DNA concentration of the two assays was evaluated by adjusting bacterial DNA concentration to 100 ng/µL and, tenfold serially diluting it up to 10 pg/µL with DNAse-free water. The diagnostic accuracy of mPCR assays was established by subjecting the assays to 60 clinical blood samples. RESULTS: Two mPCR assays were developed. Optimal primer annealing temperature of 55 °C was established and utilized in the final amplification conditions. The assays detected all targeted bacteria, with a 100 pg minimum detectable DNA concentration. Pathogens were not detected directly from whole blood, but after 4 h and 8 h of incubation, 41% (5/12) and 100% (12/12) of the bacteria were detected in culture fluids, respectively. The assays also identified Salmonella spp. and Klebsiella pneumoniae co-infections and extra pathogens (1 E. coli and 2 K. pneumoniae) compared with culture. The sensitivity and specificity of the mPCR were 100.0% (71.7-100.0) and 98.0% (90.7-99.0), respectively. The area under the ROC curve was 1.00 (1.00-1.00). CONCLUSIONS: The mPCR assays demonstrated substantial potential as a rapid tool for septicemia diagnosis alongside the traditional blood culture method. Notably, it was able to identify additional isolates, detect co-infections, and efficiently detect low bacterial DNA loads with high sensitivity, implying its value in enhancing efficiency of diagnosis of septicemia.

Mortality predictors in patients with suspected sepsis in the emergency department of a tertiary care hospital: a retrospective cohort study.

BACKGROUND: Sepsis remains a worldwide major cause of hospitalization, mortality, and morbidity. To enhance the identification of patients with suspected sepsis at high risk of mortality and adverse outcomes in the emergency department (ED), the use of mortality predictors is relevant. This study aims to establish whether quick sofa (qSOFA) and the severity criteria applied in patients with suspicion of sepsis in a monitored ED are in fact predictors of mortality. METHODS: We performed a retrospective cohort study among adult patients with suspicion of sepsis at the ED of a tertiary care hospital in Brazil between January 1st, 2019 and December 31, 2020. All adult patients (ages 18 and over) with suspected sepsis that scored two or more points on qSOFA score or at least one point on the severity criteria score were included in the study. RESULTS: The total of patients included in the study was 665 and the average age of the sample was 73 ± 19 years. The ratio of men to women was similar. Most patients exhibited qSOFA ≥ 2 (58.80%) and 356 patients (53.61%) scored one point in the severity criteria at admission. The overall mortality rate was 19.7% (131 patients) with 98 patients (14.74%) having positive blood cultures, mainly showing Escherichia coli as the most isolated bacteria. Neither scores of qSOFA nor the severity criteria were associated with mortality rates, but scoring any point on qSOFA was considered as an independent factor for intensive care unit (ICU) admission (qSOFA = 1 point, p = 0.02; qSOFA = 2 points, p = 0.03, and qSOFA = 3 points, p = 0.04). Positive blood cultures (RR, 1.63;95% CI, 1.10 to 2.41) and general administration of vasopressors at the ED (RR, 2.14;95% CI, 1.44 to 3.17) were associated with 30-day mortality. The administration of vasopressors at the ED (RR, 2.25; CI 95%, 1.58 to 3.21) was found to be a predictor of overall mortality. CONCLUSIONS: Even though an association was found between qSOFA and ICU admission, there was no association of qSOFA or the severity criteria with mortality. Therefore, patients with a tendency toward greater severity could be identified and treated more quickly and effectively in the emergency department. Further studies are necessary to assess novel scores or biomarkers to predict mortality in sepsis patients admitted to the ED's initial care.

Protective efficacy and immune responses of largemouth bass (Micropterus salmoides) immunized with an inactivated vaccine against the viral hemorrhagic septicemia virus genotype IVa.

Viral hemorrhagic septicemia virus (VHSV) poses a significant threat to the aquaculture industry, prompting the need for effective preventive measures. Here, we developed an inactivated VHSV and revealed the molecular mechanisms underlying the host's protective response against VHSV. The vaccine was created by treating VHSV with 0.05% formalin at 16°C for 48 h, which was determined to be the most effective inactivation method. Compared with nonvaccinated fish, vaccinated fish exhibited a remarkable increase in survival rate (99%) and elevated levels of serum neutralizing antibodies, indicating strong immunization. To investigate the gene changes induced by vaccination, RNA sequencing was performed on spleen samples from control and vaccinated fish 14 days after vaccination. The analysis revealed 893 differentially expressed genes (DEGs), with notable upregulation of immune-related genes such as annexin A1a, coxsackievirus and adenovirus receptor homolog, V-set domain-containing T-cell activation inhibitor 1-like, and heat shock protein 90 alpha class A member 1 tandem duplicate 2, indicating a vigorous innate immune response. Furthermore, KEGG enrichment analysis highlighted significant enrichment of DEGs in processes related to antigen processing and presentation, necroptosis, and viral carcinogenesis. GO enrichment analysis further revealed enrichment of DEGs related to the regulation of type I interferon (IFN) production, type I IFN production, and negative regulation of viral processes. Moreover, protein-protein interaction network analysis identified central hub genes, including IRF3 and HSP90AA1.2, suggesting their crucial roles in coordinating the immune response elicited by the vaccine. These findings not only confirm the effectiveness of our vaccine formulation but also offer valuable insights into the underlying immunological mechanisms, which can be valuable for future vaccine development and disease management in the aquaculture industry.

Prussian Blue Analogues-Derived Molecularly Imprinted Nanozyme Array for Septicemia Detection.

Septicemia, a severe bacterial infection, poses significant risks to human health. Early detection of septicemia by tracking specific biomarkers is crucial for a timely intervention. Herein, we developed a molecularly imprinted (MI) TiO2-Fe-CeO2 nanozyme array derived from Ce[Fe(CN)6] Prussian blue analogues (PBA), specifically targeting valine, leucine, and isoleucine, as potential indicators of septicemia. The synthesized nanozyme arrays were thoroughly characterized using various analytical techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscope, and energy-dispersive X-ray. The results confirmed their desirable physical and chemical properties, indicating their suitability for the oxidation of 3,3',5,5'-tetramethylbenzidine serving as a colorimetric probe in the presence of a persulfate oxidizing agent, further highlighting the potential of these arrays for sensitive and accurate detection applications. The MITiO2 shell selectively captures valine, leucine, and isoleucine, partially blocking the cavities for substrate access and thereby hindering the catalyzed TMB chromogenic reaction. The nanozyme array demonstrated excellent performance with linear detection ranges of 5 µM to 1 mM, 10-450 µM, and 10-450 µM for valine, leucine, and isoleucine, respectively. Notably, the corresponding limit of detection values were 0.69, 1.46, and 2.76 µM, respectively. The colorimetric assay exhibited outstanding selectivity, reproducibility, and performance in the detection of analytes in blood samples, including C-reactive protein at a concentration of 61 mg/L, procalcitonin at 870 ng/dL, and the presence of Pseudomonas aeruginosa bacteria. The utilization of Ce[Fe(CN)6]-derived MITiO2-Fe-CeO2 nanozyme arrays holds considerable potential in the field of septicemia detection. This approach offers a sensitive and specific method for early diagnosis and intervention, thereby contributing to improved patient outcomes.

Genomic characterization of Aeromonas spp. isolates from striped catfish with motile Aeromonas septicemia and human bloodstream infections in Vietnam.

Aeromonas spp. are commonly found in the aquatic environment and have been responsible for motile Aeromonas septicemia (MAS) in striped catfish, resulting in significant economic loss. These organisms also cause a range of opportunistic infections in humans with compromised immune systems. Here, we conducted a genomic investigation of 87 Aeromonas isolates derived from diseased catfish, healthy catfish and environmental water in catfish farms affected by MAS outbreaks in eight provinces in Mekong Delta (years: 2012-2022), together with 25 isolates from humans with bloodstream infections (years: 2010-2020). Genomics-based typing method precisely delineated Aeromonas species while traditional methods such as aerA PCR and MALDI-TOF were unable identify A. dhakensis. A. dhakensis was found to be more prevalent than A. hydrophila in both diseased catfish and human infections. A. dhakensis sequence type (ST) 656 followed by A. hydrophila ST251 were the predominant virulent species-lineages in diseased catfish (43.7 and 20.7 %, respectively), while diverse STs were found in humans with bloodstream infections. There was evidence of widespread transmission of ST656 and ST251 on striped catfish in the Mekong Delta region. ST656 and ST251 isolates carried a significantly higher number of acquired antimicrobial resistance (AMR) genes and virulence factors in comparison to other STs. They, however, exhibited several distinctions in key virulence factors (i.e. lack of type IV pili and enterotoxin ast in A. dhakensis), AMR genes (i.e. presence of imiH carbapenemase in A. dhakensis), and accessory gene content. To uncover potential conserved proteins of Aeromonas spp. for vaccine development, pangenome analysis has unveiled 2202 core genes between ST656 and ST251, of which 78 proteins were in either outer membrane or extracellular proteins. Our study represents one of the first genomic investigations of the species distribution, genetic landscape, and epidemiology of Aeromonas in diseased catfish and human infections in Vietnam. The emergence of antimicrobial resistant and virulent A. dhakensis strains underscores the needs of enhanced genomic surveillance and strengthening vaccine research and development in preventing Aeromonas diseases in catfish and humans, and the search for potential vaccine candidates could focus on Aeromonas core genes encoded for membrane and secreted proteins.

Non O1 non O139 Vibrio cholerae septicemia in a patient with carcinoma pancreas-a case report and literature review, 2020-2023.

Non-O1/non-O139 Vibrio cholerae, a comparably poorly studied pathogen is culpable of sporadic but serious infections. We report a case of non O1 non O139 Vibrio cholerae septicemia in a middle aged male recently diagnosed with carcinoma pancreas. He underwent biliary tract interventional procedure for hematemesis three weeks before the presentation. Now, he presented with fever, abdominal pain, hematemesis and melena. Endoscopy revealed severe portal hypertensive gastropathy and mild hemobilia. Blood culture grew Vibrio cholerae, identified as non O1 non O139 by serogrouping. He recovered successfully with timely diagnosis, appropriate antibiotics and supportive measures.

The rates of septicemia in older adults with prostate cancer treated with abiraterone or enzalutamide: A population-based study.

INTRODUCTION: Prostate cancer (PCa) is the most common non-cutaneous tumor among American men. Androgen receptor signaling inhibitors such as abiraterone and enzalutamide have been approved for similar disease states among patients with advanced PCa. Existing data suggest using steroids is associated with an increased risk of infection. Because abiraterone is usually prescribed with prednisone, we sought to compare the risk of septicemia in patients using abiraterone vs. enzalutamide. MATERIALS AND METHODS: We utilized the SEER-Medicare-linked data and used negative binomial regression models to compare the changes in the rates of septicemia-related hospitalizations six months pre- and post-abiraterone and enzalutamide initiation. RESULTS: We found that the incidence of septicemia-related hospitalizations increased 2.77 fold within six months of initiating abiraterone (incidence rate ratio [IRR]: 2.77, 95% confidence interval [CI]: 2.17-3.53) 1.97 fold within six months of starting enzalutamide (IRR: 1.97, 95% CI: 1.43-2.72). However, the difference in the changes did not reach statistical significance (interaction IRR: 0.71, 95% CI: 0.48-1.06). DISCUSSION: The findings suggest that both abiraterone and enzalutamide are associated with an increased risk of septicemia-related hospitalizations. However, the difference in the increase of septicemia risk following the two treatments did not reach statistical significance. Further studies are warranted to understand the mechanisms at play.

Multifaceted manifestations: A case report of MRSA pneumonia with sepsis, pyelonephritis, and ileus muscle abscess.

Methicillin-resistant staph aureus (MRSA) infections are challenging to treat, and with the emergence of community-associated MRSA (CA-MRSA) strains, early consideration of this pathogen in populations without typical risk factors is critical. Here we present a case of CA-MRSA pneumonia that resulted in Community-acquired pneumonia (CAP) with septic shock, pyelonephritis, and muscle abscess.

Septicemia caused by Enterococcus coli in a pregnant woman after cerclage-A case report.

The objective of this case report is to discuss a case of septicemia caused by Escherichia coli following cervical cerclage. The study described a case of a 42-year-old female patient who visited the Ante-natal Clinic for a follow-up appointment during the 8th week of gestation. The patient had previously undergone successful in vitro fertilization treatment following 16 years of primary infertility. A routine ultrasound scan revealed cervical dilatation of 2-3 cm. The patient was advised to undergo cervical cerclage insertion. Two days after the surgery, she presented with pneumonia and also experienced vaginal bleeding, necessitating the removal of the cervical cerclage. Unfortunately, the patient suffered a stillbirth. Her condition deteriorated the following day, leading to septic shock and multiple organ dysfunction. After receiving the treatment, the patient was discharged; 2 days after being discharged the patient's blood culture and sensitivity results indicated a significant growth of Escherichia coli and a diagnosis of toxic myocarditis. Following 2 months of intensive treatment, the patient showed significant improvement; however, there was the presence of some mild renal impairment and he was ultimately discharged home. Maternal sepsis poses a significant risk to the health and lives of pregnant women. Escherichia coli stands out as a primary causative agent after cervical cerclage.

[Urosepsis: pathophysiology, diagnosis, and management-an update]. / Urosepsis: Pathophysiologie, Diagnose und Management ­ ein Update.

Urinary tract infections vary widely in their clinical spectrum, ranging from uncomplicated cystitis to septic shock. Urosepsis accounts for 9-31% of all cases of septicemia and is often associated with nosocomial infections. A major risk factor for urosepsis is the presence of obstructive uropathy, caused by conditions such as urolithiasis, tumors, or strictures. The severity and course of urosepsis depend on both the virulence of the pathogen and the patient's specific immune response. Prompt therapy, including antimicrobial treatment and eradication of the infection source, along with supportive measures for circulatory and respiratory stabilization, and adjunctive therapies such as hemodialysis and glucocorticoid therapy, is crucial. Due to demographic changes, an increase in cases of urosepsis is expected-thus, it is of utmost importance for urologists to be familiar with targeted diagnostics and effective treatment.

Microbial Community Changes in Silkworms Suspected of Septicemia and Identification of Serratia sp.

Diseases that occur in silkworms include soft rot, hardening disease, digestive diseases, and sepsis. However, research on the causes of bacterial diseases occurring in silkworms and the resulting changes in the microbial community is lacking. Therefore, we examined the morphological characteristics of sepsis and changes in the microbial community between silkworms that exhibit a unique odor and healthy silkworms; thus, we established a relationship between disease-causing microorganisms and sepsis. After producing a 16S rRNA amplicon library for samples showing sepsis, we obtained information on the microbial community present in silkworms using next-generation sequencing. Compared to that in healthy silkworms, in silkworms with sepsis, the abundance of the Firmicutes phylum was significantly reduced, while that of Proteobacteria was increased. Serratia sp. was dominant in silkworms with sepsis. After bacterial isolation, identification, and reinfection through the oral cavity, we confirmed this organism as the disease-causing agent; its mortality rate was 1.8 times higher than that caused by Serratia marcescens. In summary, we identified a new causative bacterium of silkworm sepsis through microbial community analysis and confirmed that the microbial community balance was disrupted by the aberrant proliferation of certain bacteria.

Critical Illness Polyneuropathy in a Child: A Case Report.

Critical illness polyneuropathy (CIP) and myopathy (CIM) are underreported conditions in critically ill children with prolonged intensive care unit stays and mechanical ventilation. We report a case of a 10-year-old boy with pneumococcal meningoencephalitis with severe sepsis and multiorgan dysfunction. The child required prolonged ventilation, sedation, and inotropic support. He had repeated extubation failures and the development of quadriparesis with areflexia. Electrophysiology studies were consistent with CIP with acute motor and sensory axonal polyneuropathy and elevated muscle enzymes. He was treated with supportive measures and physiotherapy along with management of the underlying condition. He recovered slowly over 68 days with a good recovery with a modified Rankin's scale score of 4 on discharge. There is a need to pay attention to all critically ill children and should have a high index of suspicion for the development of CIP/CIM which can have an impact on course and outcome.

Case Report: Ambergris coprolite and septicemia in a male sperm whale stranded in La Palma (Canary Islands).

On the 21st of May 2023, a dead adult male sperm whale (Physeter macrocephalus) of 13 m in length and estimated weight of around 18,000 kg was reportedly stranded at Playa Los Nogales, La Palma, Canary Islands, Spain. A necropsy was performed 48hpm. A 50 cm diameter and 9.5 kg coprolite was found obstructing the caudal colon-rectal lumen. Necro-hemorrhagic lesions were found in heart muscles and three different bacteria of intestinal origin were isolated and identified (Edwarsiella tarda, Hathewaya limosa and Clostridium perfringens). It is reported a lethal septicemia of intestinal origin associated with ambergris coprolite as cause of death in this sperm whale.

Chromobacterium sp. septicemia in Sweden. A clinical case report.

BACKGROUND: Chromobacterium is a genus of fourteen species with validly published names, most often found in soil and waters in tropical and subtropical regions around the world. The most well-known species of the genus, C. violaceum, occasionally causes clinically relevant infections; cases of soft tissue infections with septicemia and fatal outcomes have been described. CASE PRESENTATION: Here, we present a clinical case report of a 79-year-old man from Sweden with a soft-tissue infection and septicemia. The pathogen was identified as a strain of Chromobacterium species, but not C. violaceum. The patient was treated with clindamycin and ciprofloxacin and recovered well. CONCLUSIONS: This case report demonstrates the potential of Chromobacterium species as infectious agents in immunocompetent patients. It also indicates the existence of a novel species.

Trans-Cinnamaldehyde Primes More Robust Channel Catfish Immune Responses to Edwardsiella ictaluri Infection.

Infection with Edwardsiella ictaluri, a causative agent of enteric septicemia of catfish, threatens profitable catfish production through inventory losses. We previously demonstrated that trans-cinnamaldehyde (TC) enhances the survival of catfish following E. ictaluri infection. The present study was conducted to investigate catfish immune responses to TC feeding and E. ictaluri infection. The expression of 13 proinflammatory, innate, and adaptive immune-related genes was evaluated over time in two sets of experiments using real-time polymerase chain reaction (PCR). In the first experiment, catfish were fed a basal diet with or without TC supplementation, while in the second they were fed a TC-supplemented or normal diet followed by infection with E. ictaluri. The catfish group infected with E. ictaluri and fed a TC-diet showed significant changes in the expression of innate and adaptive immune-related genes compared to control group. At 21 and 28 days post-infection, recovered fish showed significant increases in the expression of IgM in the anterior kidney and spleen. These results suggest that the supplemental dietary intake of TC can improve the immune status of catfish via engaging innate and adaptive immune responses and the production of memory cells in immunocompetent tissues. Together, this study provides an important foundation for the potential application of TC as an antimicrobial alternative in aquaculture.

Redefining piscine lactococcosis.

Piscine lactococcosis is a significant threat to cultured and wild fish populations worldwide. The disease typically presents as a per-acute to acute hemorrhagic septicemia causing high morbidity and mortality, recalcitrant to antimicrobial treatment or management interventions. Historically, the disease was attributed to the gram-positive pathogen Lactococcus garvieae. However, recent work has revealed three distinct lactococcosis-causing bacteria (LCB)-L. garvieae, L. petauri, and L. formosensis-which are phenotypically and genetically similar, leading to widespread misidentification. An update on our understanding of lactococcosis and improved methods for identification are urgently needed. To this end, we used representative isolates from each of the three LCB species to compare currently available and recently developed molecular and phenotypic typing assays, including whole-genome sequencing (WGS), end-point and quantitative PCR (qPCR) assays, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), API 20 Strep and Biolog systems, fatty acid methyl ester analysis (FAME), and Sensititre antimicrobial profiling. Apart from WGS, sequencing of the gyrB gene was the only method capable of consistent and accurate identification to the species and strain level. A qPCR assay based on a putative glycosyltransferase gene was also able to distinguish L. petauri from L. garvieae/formosensis. Biochemical tests and MALDI-TOF MS showed some species-specific patterns in sugar and fatty acid metabolism or protein profiles but should be complemented by additional analyses. The LCB demonstrated overlap in host and geographic range, but there were relevant differences in host specificity, regional prevalence, and antimicrobial susceptibility impacting disease treatment and prevention. IMPORTANCE: Lactococcosis affects a broad range of host species, including fish from cold, temperate, and warm freshwater or marine environments, as well as several terrestrial animals, including humans. As such, lactococcosis is a disease of concern for animal and ecosystem health. The disease is endemic in European and Asian aquaculture but is rapidly encroaching on ecologically and economically important fish populations across the Americas. Piscine lactococcosis is difficult to manage, with issues of vaccine escape, ineffective antimicrobial treatment, and the development of carrier fish or biofilms leading to recurrent outbreaks. Our understanding of the disease is also widely outdated. The accepted etiologic agent of lactococcosis is Lactococcus garvieae. However, historical misidentification has masked contributions from two additional species, L. petauri and L. formosensis, which are indistinguishable from L. garvieae by common diagnostic methods. This work is the first comprehensive characterization of all three agents and provides direct recommendations for species-specific diagnosis and management.