Incidence of Aeromonas bacteremia in Southern Taiwan: vibrio and Salmonella bacteremia as comparators

Antibacterial Mechanism and Flavour Impact of Ultrasound and Plasma-Activated Water Combination on Aeromonas veronii in Crayfish

Aeromonas veronii is a foodborne pathogen commonly found in contaminated crayfish. In this study, the effects of ultrasound combined with plasma-activated water (US-PAW) against A. veronii and on the flavour of crayfish were investigated to evaluate their impact on crayfish preservation. In vitro, US and PAW showed a significantly synergistic inhibition against A. veronii growth and biofilm reformation at 7 min. Furthermore, PAW disrupted the membrane integrity of A. veronii, accompanied by enhanced outer membrane permeability, with bacteria exhibiting distortion, deformation, and the accelerated leakage of intracellular substances, which US-PAW further promoted. Additionally, US-PAW increased the intracellular levels of reactive oxygen species and hydrogen peroxide, disrupting cellular homeostasis. This resulted in a significant decrease in the activities of SOD and GSH, as well as a reduction in the intracellular ATP concentration and the activities of MDH and SDH. The results indicated that US-PAW treatment impairs the ability of A. veronii cells to generate sufficient energy to resist external stress, ultimately leading to bacterial death due to the inability to maintain normal physiological functions. According to the bacterial cell count and GC-MS analysed, US-PAW treatment increased the storage period of crayfish (infected with A. veronii) by 2 days, while reducing sulphur-containing volatiles within 24.64% during 6 days of storage at 4 °C. These conclusions provide a theoretical foundation for the industrial application of US-PAW to preserve crayfish.

Aeromonas characteristics in Iran, Southwest Asia; a systematic review and meta-analysis on epidemiology, reservoirs and antibiotic resistance profile from aquatic environments to human society during 2000-2023

BACKGROUND

As recent evidence shows the prevalence and transmission of Aeromonas species in Southwest Asia, and there is no updated information on the characteristics of Aeromonas in Iran, we conducted this review. We systematically searched biomedical databases (PubMed, Web of Sciences, Scopus, SID, ISC, and Google Scholar) to identify relevant studies investigating the prevalence, antibiotic resistance, and main reservoirs of Aeromonas in aquatic animals and human clinical specimens during 2000-2023 in Iran. Cochrane's Q test and I^2 statistical test was used to assess heterogeneity, and publication bias was assessed using funnel plots and random effects tests.

RESULTS

In Iran, among 8347 human clinical samples and 1802 animal and food samples, only 87 (1.04%) and 388 (21.53%) samples were positive for Aeromonas spp. respectively, and the most isolated species was A. hydrophila. The main reservoir for Aeromonas spp. were twenty-four genera of aquatic animals besides minced meat, pigeon stool and chicken meat. In Iran, Aeromonas spp. isolates showed maximum resistance to ampicillin, tetracycline, nalidixic acid and vancomycin. The heterogeneity test for prevalence of Aeromonas species on human samples and animals or food products was significant (88.1256, (5), P-value < 0.0001) and the heterogeneity rate was 97.34% with a confidence interval of 0.2-4.3 and (194.02, (10), P-value < 0.0001) and the heterogeneity rate was 94.85% with a confidence interval of 15,124 - 33,335 respectively.

CONCLUSIONS

According to these results, it is essential for exclusive attention to the prevalence and antibiotic resistance of Aeromonas in different provinces of Iran. Furthermore, special planning should be done for prevention, outbreak control and proper treatment of infections in the aquaculture industry and human societies.

Aeromonas veronii-associated bacteremia in the course of treatment of acute myeloid leukemia: a case report and review of the literature

PURPOSE

This study aimed to report a case of acute myeloid leukemia (AML) complicated by Aeromonas veronii infection-induced bacteremia and to review relevant literature on the etiology, prevention, treatment, and prognosis of bacteremia in immunocompromised populations, aiming to reduce mortality in individuals with hematologic and other end-stage diseases and improve patient outcomes.

METHODS AND RESULTS

We reported the case of a 23-year-old male patient with relapsed AML characterized by AML1:ETO and ASXL positivity, classified as a high-risk group. The patient presented with fever, abdominal pain, diarrhea, nausea, and vomiting after consuming partially cooked fish. The patient was admitted with high leucocytes, C-reactive protein, procalcitonin, and interleukin-6 levels. Peripheral blood high-throughput sequencing (Next-Generation Sequencing NGS) confirmed infection with Aeromonas veronii, while an abdominal CT scan indicated a liver abscess with gas formation. Culture of the drainage fluid from the ultrasound-guided liver abscess puncture demonstrated growth of Aeromonas veronii. Based on the sensitivity results, the patient was treated with intravenous ciprofloxacin and cefoperazone-sulbactam. After treatment with antibiotics, blood transfusion, liver protection, and azacitidine 100 mg ih, combined with dry white sand(interferon alpha-1B, interleukin-2, and thalidomide), the critical condition of the patient improved, and he was discharged. This study was approved by the Ethics Committee of Medical Research in the Second Affiliated Hospital of Henan University of Science and Technology. Informed consent was obtained from this patient and we have obscured the patient's identifying information. All methods were carried out in accordance with relevant guidelines and regulations.

CONCLUSION

When patients with a recurrence of AML have a history of consuming or contacting aquatic products, clinicians should be vigilant about Aeromonas veronii infection. The presence of Aeromonas veronii in peripheral blood must alert clinicians to the possibility of severe sepsis and septic shock. Early diagnosis and prompt treatment are crucial to reducing patient mortality.

Haemolysin Ahh1 secreted from Aeromonas dhakensis activates the NLRP3 inflammasome in macrophages and mediates severe soft tissue infection

Severe soft tissue infections caused by Aeromonas dhakensis, such as necrotizing fasciitis or cellulitis, are prevalent in southern Taiwan and around the world. However, the mechanism by which A. dhakensis causes tissue damage remains unclear. Here, we found that the haemolysin Ahh1, which is the major virulence factor of A. dhakensis, causes cellular damage and activates the NLR family pyrin domain containing 3 (NLRP3) inflammasome signalling pathway. Deletion of ahh1 significantly downregulated caspase-1, the proinflammatory cytokine interleukin 1β (IL-1β) and gasdermin D (GSDMD) and further decreased the damage caused by A. dhakensis in THP-1 cells. In addition, we found that knockdown of the NLRP3 inflammasome confers resistance to A. dhakensis infection in both THP-1 NLRP3-/- cells and C57BL/6 NLRP3-/- mice. In addition, we demonstrated that severe soft-tissue infections treated with antibiotics combined with a neutralizing antibody targeting IL-1β significantly increased the survival rate and alleviated the degree of tissue damage in model mice compared control mice. These findings show that antibiotics combined with therapies targeting IL-1β are potential strategies to treat severe tissue infections caused by toxin-producing bacteria.

Good Performance of Revised Scoring Systems in Predicting Clinical Outcomes of Aeromonas Bacteremia in the Emergency Department: A Retrospective Observational Study

BACKGROUND

Aeromonas species, Gram-negative, non-sporulating, facultative, and anaerobic bacilli, widely distributed in aquatic environments, derive various infections, including bacteremia. Most of these infections were opportunistic and found in patients with predisposing conditions. Among the infections, bacteremia remains with notable mortality, reported from 15% to 45%. However, predicting systems for assessing the mortality risk of this disease have yet to be investigated. We aimed to validate the performance of specific predictive scoring systems to assess the clinical outcomes of Aeromonas bacteremia and applied the revised systems to predict mortality risk.

METHODS

A retrospective observational study reviewed patients with bacteremia caused by Aeromonas spp. based on at least one positive blood culture sample collected in the emergency department from January 2012 to December 2020. The outcome was in-hospital mortality. We used seven predictive scoring systems to predict the clinical outcome. According to the effectiveness in predicting mortality, we revised three of the seven predictive scoring systems by specific characteristics to refine their risk-predicting performances.

RESULTS

We enrolled 165 patients with bacteremia caused by Aeromonas spp., including 121 males (73.3%) and 44 females (26.7%), with a mean age of 66.1 ± 14.9 years and an average length of hospital stay of 12.4 ± 10.9 days. The overall mortality rate was 32.7% (54/165). The non-survivors had significantly higher scores in MEDS (6.7 ± 4.2 vs. 12.2 ± 3.3, p < 0.001), NEWS (4.0 ± 2.8 vs. 5.3 ± 3.0, p = 0.008), and qSOFA (0.3 ± 0.6 vs. 0.6 ± 0.7, p = 0.007). Regarding mortality risk prediction, the MEDS demonstrated the best predictive power with AUC of ROC measured up to 0.834, followed by NEWS (0.626) and qSOFA (0.608). We revised the MEDS, NEWS, and qSOFA by hemoglobin and lactate. We found that the revised scores had better powerful performance, including 0.859, 0.767, and 0.691 of the AUC of ROC, if the revised MEDS ≥10, revised NEWS ≥8, and revised qSOFA ≥2, respectively.

CONCLUSIONS

MEDS, NEWS, and qSOFA were good tools for predicting outcomes in patients with Aeromonas spp. bacteremia. The revised MEDS, NEWS, and qSOFA demonstrated more powerful predicting performance than the original scoring systems. We suggested that patients with higher scores in revised MEDS (≥10), revised NEWS (≥8), and revised qSOFA (≥2) received early goal-directed therapy and appropriate broad-spectrum antibiotic treatment as early as possible to reduce mortality.

Ventilator-associated pneumonia due to Aeromonas hydrophila: A rare case report

Introduction

Aeromonas hydrophila is an opportunistic pathogen that can cause various infections, including pneumonia, in immunocompromised individuals. This case report presents a rare occurrence of ventilator-associated pneumonia (VAP) caused by Aeromonas hydrophila in an apparently non-immunocompromised patient.

Case presentation

The patient exhibited signs and symptoms of VAP and was successfully treated with intravenous ciprofloxacin. The discussion highlights the characteristics of Aeromonas species, its virulence factors, risk factors for infection, and antibiotic profile.

Conclusion

It emphasizes the need for awareness and suspicion of Aeromonas as a potential cause of VAP in ICU settings, as well as the importance of early detection and appropriate treatment for improved outcomes.

Transcriptomic insights into the immune response of the intestine to Aeromonas veronii infection in northern snakehead (Channa argus)

Intestinal inflammation is a protective response that is implicated in bacterial enteritis triggered by gastrointestinal infection. The immune mechanisms elicited in teleost against the infection of Aeromonas veronii are largely unknown. In this study, we performed a de novo northern snakehead (Channa argus) transcriptome assembly using Illumina sequencing platform. On this basis we performed a comparative transcriptomic analysis of northern snakehead intestine from A. veronii-challenge and phosphate buffer solution (PBS)-challenge fish, and 2076 genes were up-regulated and 1598 genes were down-regulated in the intestines infected with A. veronii. The Gene Ontology (GO) enrichment analysis indicated that the differentially expressed genes (DEGs) were enriched to 27, 21 and 20 GO terms in biological process, cellular component, and molecular function, respectively. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that 420 DEGs were involved in 194 pathways. Moreover, 33 DEGs were selected for quantitative real-time PCR analysis to validate the RNA-seq data. The results reflected the consistency of the expression levels between qRT-PCR and RNA-seq data. In addition, a time-course analysis of the mRNA expression of 33 immune-related genes further indicated that the intestinal inflammation to A. veronii infection simultaneously regulated gene expression alterations. The present study provides transcriptome data of the teleost intestine, allowing us to understand the mechanisms of intestinal inflammation triggered by bacterial pathogens. DATA AVAILABILITY STATEMENT: All data supporting the findings of this study are available within the article and Supplementary files. The RNA-seq raw sequence data are available in NCBI short read archive (SRA) database under accession number PRJNA615958.

Epidemiology of Aeromonas Species Bloodstream Infection in Queensland, Australia: Association with Regional and Climate Zones

Aeromonas species can cause severe bloodstream infection (BSI) however, few studies have examined their epidemiology in non-selected populations. The objective of this study was to describe the incidence and determinants of Aeromonas species BSI in Queensland, Australia. A retrospective population-based cohort study was conducted during 2000-2019. Aeromonas species BSI were identified by laboratory surveillance and clinical and outcome information through data linkages to statewide databases. A total of 407 incident Aeromonas species BSI were identified with an age- and sex-standardized incidence of 5.2 per million residents annually. No trend in annual incidence rate during two decades of surveillance was demonstrated. Significant variable monthly occurrences were observed with highest rates during warmer, wetter months, and lowest rates during winter and dry periods. There was significant variability in incidence accordingly to region and climate zones, with higher rates observed in tropical north regions and lowest in southeastern corner. The highest incidence was observed in very remote and hot areas in Queensland. Cases were infrequent in children and risk was highest in elderly and males. Seventy-eight patients died within 30 days with a case-fatality rate of 19%. Older age, non-focal infection, higher Charlson score, and monomicrobial bacteremia were independent risk factors for death. Demographic and climatic changes may increase the burden of these infections in future years.

In-hospital mortality associated with necrotizing soft tissue infection due to Vibrio vulnificus: a matched-pair cohort study

Background

It remains unclear whether Vibrio vulnificus necrotizing soft tissue infection (NSTI) is associated with higher mortality compared with non-Vibrio NSTI. This study’s objective was to compare outcomes including in-hospital mortality and prognosis between patients with V. vulnificus NSTI and those with non-Vibrio NSTI.

Method

A retrospective 1:2 matched-pair cohort study of hospitalized patients with NSTI diagnosed by surgical finding was conducted in two tertiary hospitals in southern Taiwan between January 2015 and January 2020. In-hospital outcomes (mortality, length of stay) were compared between patients with and without V. vulnificus infection. We performed multiple imputation using chained equations followed by multivariable regression analyses fitted with generalized estimating equations to account for clustering within matched pairs. All-cause in-hospital mortality and length of stay during hospitalization were compared for NSTI patients with and without V. vulnificus.

Result

A total of 135 patients were included, 45 in V. vulnificus NSTI group and 90 in non-Vibrio group. The V. vulnificus NSTI patients had higher mortality and longer hospital stays. Multivariable logistic regression analysis revealed that V. vulnificus NSTI was significantly associated with higher in-hospital mortality compared with non-Vibrio NSTI (adjusted odds ratio = 1.52; 95% confidence interval 1.36–1.70; p < 0.01).

Conclusion

Vibrio vulnificus NSTI was associated with higher in-hospital mortality and longer hospital stay which may increase health care costs, suggesting that preventing V. vulnificus infection is essential.

Isolation, identification and virulence gene characterization of Aeromona dhakensis isolated from sea lion (Zalophus californianus)

Species of Aeromonas are ubiquitous pathogens of fish and aquatic animals and can infect humans and other animals through the food chain. However, there are few reports of marine mammalian infections. In 2020, a sea lion (Zalophus californianus) died acutely at an aquarium in Harbin, Heilongjiang Province, China. In order to explore the cause of death, we dissected the animal and observed pathological changes. Ogans were aseptically collected and used for bacterial isolation and culture. This revealed that the sea lion had died of sepsis caused by a bacterial infection. Isolated bacteria were investigated by morphology, biochemical phenotype and molecular identification, and this determined the pathogen as A. dhakensis. The isolate contained six virulence genes, hlyA, aerA, act, lafA, ela, fla, and was susceptible to most antibiotics. This is the first report of A. dhakensis associated with septicemia in pinnipeds and a description of its virulence and resistance profiles. Its presence in aquatic environments poses a potential threat to marine mammals.

Comparison of Surgical Outcomes and Predictors in Patients with Monomicrobial Necrotizing Fasciitis and Sepsis Caused by Vibrio vulnificus, Aeromonas hydrophila, and Aeromonas sobria

Background: Monomicrobial necrotizing fasciitis caused by Vibrio vulnificus, Aeromonas hydrophila, and Aeromonas sobria are often associated with high mortality rates. The purpose of this study was to compare the independent predictors related to outcomes between Vibrio vulnificus and Aeromonas species necrotizing fasciitis. Patients and Methods: Monomicrobial necrotizing fasciitis caused by Vibrio vulnificus (60 patients) and Aeromonas species (31 patients) over an 11-year period were reviewed retrospectively. Differences in mortality, patient characteristics, clinical presentations, and laboratory data were compared between the Vibrio vulnificus and Aeromonas species groups, and between the death and the survival subgroups of patients with Aeromonas species. Results: Six patients in the Vibrio vulnificus group (10%) and 11 in the Aeromonas species group (32.3%) died. Fifty-nine patents had bacteremia and 16 patients died (27.1%). Patients who had Vibrio vulnificus had a higher incidence of bacteremia. The patients who had Aeromonas species presenting with bacteremia were significantly associated with death. The death subgroup of patients with Aeromonas necrotizing fasciitis had a higher incidence of bacteremia, higher counts of banded leukocytes, lower platelet counts, lower total lymphocyte counts, and lower serum albumin level than the survival subgroup. Conclusions: Monomicrobial necrotizing fasciitis caused by Aeromonas species was characterized by more fulminating and higher mortality than that of Vibrio vulnificus, even after early fasciotomy and third-generation cephalosporin antibiotic therapy. Those risk factors, such as bacteremia, shock, lower platelet counts, lower albumin levels, and antibiotic resistance were associated with mortality, which should alert clinicians to pay more attention to and aggressively treat those patients with Aeromonas and Vibrio necrotizing fasciitis.

Aeromonas: the multifaceted middleman in the One Health world

Aeromonas is at the interface of all the One Health components and represents an amazingly sound test case in the One Health approach, from economic loss in aquaculture tochallenges related to antibiotic-resistant bacteria selected from the environment. In human health, infections following leech therapy is an outstanding example of such One Health challenges. Aeromonads are not only ubiquitous environmental bacteria, able to rapidly colonize and cause opportunistic infections in humans and animals, they are also capable of promoting interactions and gene exchanges between the One Health components. This makes this genus a key amplifier of genetic transfer, especially of antibiotic resistance genes.

Pancreaticobiliary Cancers and Aeromonas Isolates Carrying Type Ⅲ Secretion System Genes ascF-ascG Are Associated With Increased Mortality: An Analysis of 164 Aeromonas Infection Episodes in Southern Taiwan

This prospective study aimed to investigate the clinical and microbiological characteristics of different Aeromonas species. Clinical isolates of Aeromonas species between 2016 to 2018 were collected in a university hospital in southern Taiwan. The species was determined by rpoD or gyrB sequencing. A total of 222 Aeromonas isolates from 160 patients in 164 episodes were identified. The crude in-hospital mortality was 17.2%. The most frequently isolated species was Aeromonas veronii (30.6%), followed by A. caviae (24.8%), A. hydrophila (23%), and A. dhakensis (16.7%). The major clinical manifestations were primary bacteremia (31.1%), skin and soft tissue infection (22.6%), and biliary tract infection (18.3%). The most common underlying diseases were malignancy (45.1%), diabetes mellitus (27.4%), and liver cirrhosis or chronic hepatitis (26.2%). A. hydrophila and A. dhakensis predominated in the skin and soft tissue infection (p<0.0001), whereas A. vernoii and A. caviae prevailed in primary bacteremia and biliary tract infections (p=0.012). Pneumonia, malignancy, and ascF-ascG genotype were independent factors associated with mortality. Ertapenem susceptibility was decreased in A. sobria (42.9%), A. veronii (66.7%), A. dhakensis (73%), and A. hydrophila (84.3%). Cefotaxime resistance was found in 30.9% of A. caviae and 18.9% of A. dhakensis isolates, much more prevalent than the other species. The metallo-β-lactamase blaCphA was almost invariably present in A. dhakensis, A. hydrophila, and A. veronii (100%, 100% and 89.9%, respectively). Amp-C β-lactamases such as blaMOX and blaAQU-1 were identified in all A. caviae and 91.9% of A. dhakensis isolates. Cefepime, fluoroquinolones and tigecycline showed good in vitro activity against aeromonads.

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.

Bacteriology and mortality of necrotizing fasciitis in a tertiary coastal hospital with comparing risk indicators of methicillin-resistant Staphylococcus aureus and Vibrio vulnificus infections: a prospective study

BACKGROUND

Vibrio vulnificus has been reported as the leading causative pathogen of necrotizing fasciitis (NF) and related fatality in the coastal area. Necrotizing fasciitis caused by methicillin-resistant Staphylococcus aureus (MRSA) and V. vulnificus have high mortality rates. The purpose of this prospective study was to clarify the clinical characteristics between death and survival NF patients, to investigate bacteriologic profile and mortality of NF patients, and to compare risk indicators of MRSA and V. vulnificus NF patients.

METHODS

This prospective study was conducted in 184 consecutive NF patients over a period of three years in a tertiary coastal hospital. Differences in mortality, laboratory findings, microbiology and clinical outcomes were compared between the death and survival groups, and the V. vulnificus and MRSA subgroups.

RESULTS

Twenty patients died, resulting in a mortality rate of 10.9%, and there were 108 patients with a monomicrobial infection (58.7%). The death group had a significantly higher incidence of shock at emergency room and bacteremia than did the survival group. Vibrio species (40 cases) and S. aureus (31 cases) were the two major pathogens. Significant differences with respect to hepatic dysfunction, shock, the event with seawater or seafood contact, bacteremia, C-reactive protein, mean platelet counts, and the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score were observes between V. vulnificus and MRSA groups.

CONCLUSIONS

NF patients with both hepatic dysfunction and diabetes mellitus, bacteremia and shock have significantly higher mortality. We should be aware of the increasing incidence of monomicrobial NF and higher mortality rates of Gram-negative pathogens in the warm coastal area. LRINEC score is not a suitable diagnostic indicator for V. vulnificus NF, which is more rapidly progressive and fulminant than MRSA NF. NF needed team works by early suspicion, immediate surgical intervention and aggressive care, which can successfully decrease mortality.

UvrY is required for the full virulence of Aeromonas dhakensis

Aeromonas dhakensis is an emerging human pathogen which causes fast and severe infections worldwide. Under the gradual pressure of lacking useful antibiotics, finding a new strategy against A. dhakensis infection is urgent. To understand its pathogenesis, we created an A. dhakensis AAK1 mini-Tn10 transposon library to study the mechanism of A. dhakensis infection. By using a Caenorhabditis elegans model, we established a screening platform for the purpose of identifying attenuated mutants. The uvrY mutant, which conferred the most attenuated toxicity toward C. elegans, was identified. The uvrY mutant was also less virulent in C2C12 fibroblast and mice models, in line with in vitro results. To further elucidate the mechanism of UvrY in controlling the toxicity in A. dhakensis, we conducted a transcriptomic analysis. The RNAseq results showed that the expression of a unique hemolysin ahh1 and other virulence factors were regulated by UvrY. Complementation of Ahh1, one of the most important virulence factors, rescued the pore-formation phenotype of uvrY mutant in C. elegans; however, complementation of ahh1 endogenous promoter-driven ahh1 could not produce Ahh1 and rescue the virulence in the uvrY mutant. These findings suggest that UvrY is required for the expression of Ahh1 in A. dhakensis. Taken together, our results suggested that UvrY controls several different virulence factors and is required for the full virulence of A. dhakensis. The two-component regulator UvrY therefore a potential therapeutic target which is worthy of further study.

Correlation Between Pathogenic Determinants Associated with Clinically Isolated Non-Typhoidal Salmonella

Non-typhoidal and Typhoidal Salmonella are bacterial pathogens source of worldwide and major disease burden. Virulent determinants of specific serovars belonging to non-typhoidal Salmonella have been extensively studied in different models, yet the pathogenesis of this group of bacteria and the development of clinical symptoms globally remains underexplored. Herein, we implemented microbiological and molecular procedures to investigate isolate virulence traits and molecular diversity, likely in association with disease severity. Our results show that selected clinical isolates from a tertiary referring hospital, depending on the richness of the environment and isolate serotypes, exhibited different, and sometimes controversial, virulence properties. The tested strains were susceptible to Ceftriaxone (90%) with decreasing reactivity to Trimethoprim–Sulfamethoxazole (72%), Chloramphenicol (64%), Ampicillin (48%), Gentamicin (44%), and Ciprofloxacin (2%). Disc susceptibility results partially correlated with minimum inhibitory concentration (MIC); however, special attention must be given to antimicrobial treatment, as a rise in multi-resistant isolates to Trimethoprim–Sulfamethoxazole (2/38 µg/mL), Minocycline (8 µg/mL) and Ampicillin (16 µg/mL) has been noticed, with two isolates resistant to Ceftazidime (16 µg/mL). By comparison to previous molecular epidemiology studies, the variation in the gene profiles of endemic pathogens supports the need for continuous and up-to-date microbiological and molecular reports.

Different types of bullae of limbs with necrotizing fasciitis predict different outcome: a prospective study

Study objective

Necrotizing fasciitis (NF) is an uncommon life-threatening necrotizing skin and soft tissue infection. Bullae are special skin manifestations of NF. This study was conducted to analyze the differences between different types of bullae of limbs with NF for providing the information to emergency treatment.

Methods

From April 2015 to August 2018, patients were initially enrolled based on surgical confirmation of limbs with NF. According to the presence of different bullae types, patients were divided into no bullae group (Group N), serous-filled bullae group (Group S), and hemorrhagic bullae group (Group H). Data such as demographics, clinical outcomes, microbiological results, presenting symptoms/signs, and laboratory findings were compared among these groups.

Results

In total, 187 patients were collected, with 111 (59.4%) patients in Group N, 35 (18.7%) in Group S, and 41 (21.9%) in Group H. Group H had the highest incidence of amputation, required intensive care unit care, and most patients infected with Vibrio species. In Group N, more patients were infected with Staphylococcus spp. than Group H. In Group S, more patients were infected with β-hemolytic Streptococcus than Group H. Patients with bacteremia, shock, skin necrosis, anemia, and longer prothrombin time constituted higher proportions in Group H and S than in Group N.

Conclusions

In southern Taiwan, patients with NF accompanied by hemorrhagic bullae appear to have more bacteremia, Vibrio infection, septic shock, and risk for amputation. If the physicians at the emergency department can detect for the early signs of NF as soon as possible, and more patient’s life and limbs may be saved.

Genomic Analysis of Aeromonas veronii C198, a Novel Mcr-3.41-Harboring Isolate from a Patient with Septicemia in Thailand

The resistance of Gram-negative bacteria to colistin, mediated by plasmid-borne mcr genes, is an emerging public health concern. The complete genome sequence (4.55 Mb) of a clinical isolate of Aeromonas veronii biovar veronii obtained from a patient with septicemia was determined using short-read and long-read platforms. This isolate (C198) was found to harbor a novel mcr-3 gene, designated mcr-3.41. Isolate C198 revealed adjacent mcr-3.41 and mcr-3-like genes. It contained one chromosome and two plasmids, both of which encoded a RepB replication protein. Other antimicrobial resistance genes, including bla_cphA3, bla_OXA-12, tetA, rsmA, and adeF, were also present. Isolate C198 was resistant to amoxicillin–clavulanate, ampicillin–sulbactam and tetracycline, and showed intermediate resistance to trimethoprim–sulfamethoxazole. The isolate was susceptible to piperacillin–tazobactam, carbapenem, third-generation cephalosporins, fluoroquinolones, chloramphenicol, and aminoglycosides. Putative virulence genes in the C198 genome encoded type II, III, and VI secretion systems; type IV Aeromonas pili; and type I fimbria, flagella, hemagglutinin, aerolysin, and hemolysins. Multilocus sequence typing revealed a novel sequence type (ST), ST720 for C198. Phylogenetic analysis of the single nucleotide polymorphisms in C198 demonstrated that the strain was closely related to A. veronii 17ISAe. The present study provides insights into the genomic characteristics of human A. veronii isolates.

Predictors for gram-negative monomicrobial necrotizing fasciitis in southern Taiwan

BACKGROUND

Necrotizing fasciitis (NF) is a rare and life-threatening necrotizing skin and soft-tissue infection. Infectious pathogens of NF must be detected early and treated rapidly to prevent loss of limb or a fatal outcome. This study aimed to detect more reliable predictors between gram-negative and gram-positive monomicrobial NF of limbs.

METHODS

A total of 100 patients with limb monomicrobial NF were diagnosed prospectively from April 2015 to July 2018. These monomicrobial NF pathogens can be divided into gram-negative and gram-positive groups according to the result of Gram staining and final bacterial reports. Data such as demographics, seawater or seafood contact history, infectious location, comorbidities, presenting signs and symptoms, and laboratory findings were recorded and compared.

RESULTS

A total of 55 patients were infected with gram-negative organisms and 45 patients with gram-positive organisms. Among the 55 cases of monomicrobial gram-negative NF, 48 (87.3%) were caused mainly by Vibrio spp. (38, 69.1%) and Aeromonas spp. (10, 18.2%). A higher incidence of chronic kidney disease, cerebrovascular accident, tachypnea, and septic shock; a higher rate of band forms of leukocytes of more than 3%, serum lactate of more than 20 mg/dL, and C-reactive protein level of less than 150 mg/dL; prolonged prothrombin time; and a lower fibrinogen level were observed in patients with gram-negative infection. In a multivariate analysis, a higher incidence of seawater or seafood contact history (odds ratio [OR]: 66.301; 95% confidence interval [CI]: 7.467-588.702), a higher rate of hyperlactatemia (OR: 7.904; 95% CI: 1.231-50.744), and a low fibrinogen level (OR: 1.013; 95% CI: 1.004-1.023) indicated gram-negative infection.

CONCLUSIONS

In southern Taiwan, NF of limbs mainly affected the lower limbs, exhibited monomicrobial infection, and was predominated by gram-negative bacteria. Gram-negative monomicrobial NF of limbs often occurred in individuals with the more seawater or seafood contact history, hyperlactatemia, and low fibrinogen levels.

An Update on the Genus Aeromonas: Taxonomy, Epidemiology, and Pathogenicity

The genus Aeromonas belongs to the Aeromonadaceae family and comprises a group of Gram-negative bacteria widely distributed in aquatic environments, with some species able to cause disease in humans, fish, and other aquatic animals. However, bacteria of this genus are isolated from many other habitats, environments, and food products. The taxonomy of this genus is complex when phenotypic identification methods are used because such methods might not correctly identify all the species. On the other hand, molecular methods have proven very reliable, such as using the sequences of concatenated housekeeping genes like gyrB and rpoD or comparing the genomes with the type strains using a genomic index, such as the average nucleotide identity (ANI) or in silico DNA–DNA hybridization (isDDH). So far, 36 species have been described in the genus Aeromonas of which at least 19 are considered emerging pathogens to humans, causing a broad spectrum of infections. Having said that, when classifying 1852 strains that have been reported in various recent clinical cases, 95.4% were identified as only four species: Aeromonas caviae (37.26%), Aeromonas dhakensis (23.49%), Aeromonas veronii (21.54%), and Aeromonas hydrophila (13.07%). Since aeromonads were first associated with human disease, gastroenteritis, bacteremia, and wound infections have dominated. The literature shows that the pathogenic potential of Aeromonas is considered multifactorial and the presence of several virulence factors allows these bacteria to adhere, invade, and destroy the host cells, overcoming the immune host response. Based on current information about the ecology, epidemiology, and pathogenicity of the genus Aeromonas, we should assume that the infections these bacteria produce will remain a great health problem in the future. The ubiquitous distribution of these bacteria and the increasing elderly population, to whom these bacteria are an opportunistic pathogen, will facilitate this problem. In addition, using data from outbreak studies, it has been recognized that in cases of diarrhea, the infective dose of Aeromonas is relatively low. These poorly known bacteria should therefore be considered similarly as enteropathogens like Salmonella and Campylobacter.

[Clinical features and laboratory data analysis of Aeromonas bacteremia with hematological diseases]

Objective: To investigate the clinical and laboratory features of Aeromonas bacteremia in patients with hematological diseases, and provide evidence for the prevention and treatment of Aeromonas infection. Methods: A retrospective study of patients with bloodstream infection of Aeromonas in our hospital from January 2014 to December 2018 was carried out. The clinical characteristics, antimicrobial susceptibility, infection seasons, antimicrobial therapy and evolution were analyzed. Results: A total of 42 patients with hematological diseases had Aeromonas bloodstream infection within 5 years. Among them, 39 cases (92.9%) of bloodstream infection occurred in the stage of neutropenia. The median time of fever was 4 (1-27) d, 22 (52.4%) patients only had fever, 6 (14.3%) with gastrointestinal symptoms (abdominal pain, diarrhea, nausea, upper gastrointestinal bleeding) , 8 (19.0%) with pulmonary infection, 13 (31.0%) with skin and soft tissue infections. Seven patients (16.7%) died with skin and soft tissue infection. The resistance of Aeromonas to carbapenems was 68.3%-70.7%, while the resistance rate to cephalosporins, quinolones and aminoglycosides were less than 10%. Conclusions: Aeromonas bacteremia in patients with hematological diseases mainly occur in the neutropenia stage, usually with symptom like fever. The mortality is increased when accompanied by skin and soft tissue infection. Antibiotic use should be based on susceptibility results, and avoid the use of carbapenems.

Aeromonas Isolates from Fish and Patients in Tainan City, Taiwan: Genotypic and Phenotypic Characteristics

The present study aimed to isolate Aeromonas from fish sold in the markets as well as in sushi and seafood shops and compare their virulence factors and antimicrobial characteristics with those of clinical isolates. Among the 128 fish isolates and 47 clinical isolates, Aeromonas caviae, A. dhakensis, and A. veronii were the principal species. A. dhakensis isolates carried at least 5 virulence genes, more than other Aeromonas species. The predominant genotype of virulence genes was hlyA lip alt col ela in both A. dhakensis and A. hydrophila isolates, alt col ela in A. caviae isolates, and act in A. veronii isolates. A. dhakensis, A. hydrophila, and A. veronii isolates more often exhibited hemolytic and proteolytic activity and showed greater virulence than A. caviae isolates in Caenorhabditis elegans and the C2C12 cell line. However, the link between the genotypes and phenotypes of the studied virulence genes in Aeromonas species was not evident. Among the four major clinical Aeromonas species, nearly all (99.0%) A. dhakensis, A. hydrophila, and A. veronii isolates harbored bla _CphA, which encodes a carbapenemase, but only a minority (6.7%, 7/104) were nonsusceptible to carbapenem. Regarding AmpC β-lactamase genes, bla _AQU-1 was exclusively found in A. dhakensis isolates, and bla _MOX3 was found only in A. caviae isolates, but only 7.6% (n = 6) of the 79 Aeromonas isolates carrying bla _AQU-1 or bla _MOX3 exhibited a cefotaxime resistance phenotype. In conclusion, fish Aeromonas isolates carry a variety of combinations of virulence and β-lactamase resistance genes and exhibit virulence phenotypes and antimicrobial resistance profiles similar to those of clinical isolates.IMPORTANCE Aeromonas species can cause severe infections in immunocompromised individuals upon exposure to virulent pathogens in the environment, but the characteristics of environmental Aeromonas species remain unclear. Our study showed that several pathogenic Aeromonas species possessing virulence traits and antimicrobial resistance similar to those of Aeromonas isolates causing clinical diseases were present in fish intended for human consumption in Tainan City, Taiwan.

In vitro and in vivo antibacterial activity of tigecycline against Vibrio vulnificus

BACKGROUND/PURPOSE

The aim of this study is to investigate the role of tigecycline in Vibrio vulnificus infection.

METHODS

Eight randomly selected clinical V. vulnificus isolates were studied to obtain the minimal inhibitory concentrations (MICs) of minocycline, cefotaxime, and tigecycline, and the time-kill curves of tigecycline alone or in combination with other drugs. A peritonitis mouse model was used for the evaluation of the therapeutic efficacy of tigecycline alone or cefotaxime in combination with minocycline or tigecycline.

RESULTS

The MIC of minocycline, cefotaxime, and tigecycline for eight clinical V. vulnificus isolates was 0.06-0.12 μg/mL, 0.03-0.06 μg/mL, and 0.03-0.06 μg/mL, respectively. In time-killing studies, at the concentration of 1 × MIC, the inhibitory effect of tigecycline persisted for 24 hours in five of eight isolates. With 2 × MIC and trough level, the inhibitory effect was noted in all isolates for 24 hours. With the combination of minocycline plus cefotaxime and tigecycline plus cefotaxime at 1/2 × MIC, the bactericidal effect was noted in 25% and 62.5% of eight isolates and synergism in 50% and 75% of isolates. With a low (1.25 × 10⁵ CFU/mL) inoculum, all infected mice survived with tigecycline alone, tigecycline plus cefotaxime, or minocycline plus cefotaxime on the 14^th day. At the inoculum of 1.25 × 10⁶ CFU, the survival rate was 33.3% on the 14^th day in the tigecycline plus cefotaxime-treated group, but none of the mice treated by tigecycline alone or minocycline plus cefotaxime survived (33.3% vs. 0%, p = 0.01 by Fisher's exact test).

CONCLUSION

Our in vitro combination and animal studies indicate that tigecycline could be an option for the treatment of invasive V. vulnificus infections.

Clinical characteristics in adult patients with Salmonella bacteremia and analysis of ciprofloxacin-nonsusceptible isolates

BACKGROUND/PURPOSE

The purpose of this study is to describe clinical characteristics of Salmonella bacteremia in adult patients and analyze ciprofloxacin-nonsusceptible isolates.

METHODS

A total of 101 Salmonella blood isolates from adult patients were collected from January 2011 to December 2013 in MacKay Memorial Hospital. Eight ciprofloxacin-nonsusceptible Salmonella blood isolates were screened for carbapenemase and other β lactamase genes. Isolates were examined by PCR for the quinolone resistance-determining region (QRDR) of all subunits for DNA gyrase (gyrA and gyrB) genes and topoisomerase IV (parC and parE) genes.

RESULTS

There were 22 (21.78%) S. enterica serovar B, 5 (4.95%) S. enterica serovar C1, 7 (6.93%) S. enterica serovar C2, 65 (64.36%) S. enterica serovar D, and 2 (1.98%) S. enterica serovar Typhi (S. typhi) isolates. β-lactamase gene screening and sequencing yielded only one blaCMY-2-positive isolate. In multivariate risk factor analysis, renal insufficiency [odds ratio (OR) 3.774; p = 0.020] and heart disease (OR 2.922; p = 0.027) were more common among elderly patients (≥65 years). Independent risk factors for ciprofloxacin-nonsusceptible strains included S. enterica serovar C2 (OR 28.430; p = 0.032), renal insufficiency (OR 13.927; p = 0.032), and immunosuppression agent usage (OR 60.082; p = 0.006). 87.50% (7/8) of isolates had gyrA mutation, 62.50% (5/8) had parC mutation, and none had gyrB and parE mutations. Isolates with both Ser83Phe/Asp87Asn gyrA and Thr57Ser/Ser80Ile parC mutation genes were highly ciprofloxacin-resistant (minimum inhibitory concentration ≥4 mg/L).

CONCLUSIONS

Elderly patients with renal insufficiency and heart disease were at risk for Salmonella bacteremia. Those for ciprofloxacin-nonsusceptible strains included S. enterica serovar C2, renal insufficiency, and immunosuppression agent usage. The 8 ciprofloxacin-nonsusceptible isolates carried gyrA and parC mutations, which cause resistance that poses a major concern.

Monomicrobial Necrotizing Fasciitis Caused by Aeromonas hydrophila and Klebsiella pneumoniae

OBJECTIVE

To compare specific characteristics and clinical outcomes of monomicrobial necrotizing fasciitis caused by Aeromonashydrophila and Klebsiella pneumoniae.

MATERIAL AND METHODS

Cases of monomicrobial necrotizing fasciitis caused by A. hydrophila (n = 11) and K. pneumoniae (n = 7) over an 8-year period were retrospectively reviewed. Differences in mortality, patient characteristics, clinical presentations, and laboratory data were compared between the A. hydrophila and the K. pneumoniae groups.

RESULTS

The clinical signs and symptoms at the time of presentation did not differ significantly (p > 0.05) between the two groups. The A. hydrophila group had a significantly shorter interval between contact and admission (1.55 ± 0.52 vs. 5.14 ± 2.12 days, p < 0.001) and significant lower total white blood cell counts (10,245 ± 5,828 vs. 19,014 ± 11,370 cells/mm(3), p < 0.045) than the K. pneumoniae group in the emergency room. Hepatic dysfunction was associated with mortality in patients with A. hydrophila infection, while diabetes mellitus was associated with mortality in patients with K. pneumoniae infection. Overall, 5 (45.5%) patients in the A. hydrophila group and 3 (42.8%) in the K. pneumoniae group died.

CONCLUSION

The initial clinical course of A. hydrophila monomicrobial necrotizing fasciitis was characterized by more rapidly progressive disease than that of the K. pneumoniae infection. Patients with hepatic dysfunction and necrotizing fasciitis should be suspected of having A. hydrophila infection, and diabetic patients with necrotizing fasciitis should be suspected of having K. pneumoniae infection initially.

Virulence diversity among bacteremic Aeromonas isolates: ex vivo, animal, and clinical evidences

Background

The objective of this study was to compare virulence among different Aeromonas species causing bloodstream infections.

Methodology/Principal Findings

Nine of four species of Aeromonas blood isolates, including A. dhakensis, A. hydrophila, A. veronii and A. caviae were randomly selected for analysis. The species was identified by the DNA sequence matching of rpoD. Clinically, the patients with A. dhakensis bacteremia had a higher sepsis-related mortality rate than those with other species (37.5% vs. 0%, P = 0.028). Virulence of different Aeromonas species were tested in C. elegans, mouse fibroblast C2C12 cell line and BALB/c mice models. C. elegans fed with A. dhakensis and A. caviae had the lowest and highest survival rates compared with other species, respectively (all P values <0.0001). A. dhakensis isolates also exhibited more cytotoxicity in C2C12 cell line (all P values <0.0001). Fourteen-day survival rate of mice intramuscularly inoculated with A. dhakensis was lower than that of other species (all P values <0.0001). Hemolytic activity and several virulence factor genes were rarely detected in the A. caviae isolates.

Conclusions/Significance

Clinical data, ex vivo experiments, and animal studies suggest there is virulence variation among clinically important Aeromonas species.

Aeromonas stool isolates from individuals with or without diarrhea in southern Taiwan: Predominance of Aeromonas veronii

BACKGROUND

Although aeromonads are important pathogens causing invasive infections in southern Taiwan, Aeromonas-associated intestinal infections have been rarely mentioned.

PURPOSE

The aim of this study was to understand the frequency of isolation and clinical significance of aeromonads recovered from adult stool samples in southern Taiwan.

METHODS

During a 15-month study period, 514 adults with diarrhea and 167 asymptomatic controls were prospectively screened for the presence of aeromonads in stools. The identity of Aeromonas species was determined by the rpoD sequencing. Clinical information was retrieved from medical records, and in vitro cytotoxicity assay and polymerase chain reaction detection of putative virulent genes were performed.

RESULTS

Thirteen (2.5 %) of 514 diarrheal patients and six (3.6%) of 167 asymptomatic controls had Aeromonas isolates in their stools. Of 11 diarrheal patients with available clinical information, Aeromonas veronii, the predominant species, was noted in six patients, and another potential enteropathogen was present in four patients. The cytotoxicity of A. veronii isolates to the HT-29 cell line was more potent in the isolates from diarrheal patients than those from asymptomatic controls (p = 0.015). The cytotoxicity of A. veronii isolates was more potent than that of A. caviae from symptomatic patients (p = 0.001). Putative virulence markers, including AHCYTONE, ascV, ascF-ascG, and aexT, were detected exclusively in A. veronii. The presence of the ascV gene was associated with cytotoxicity in A. veronii isolates. All Aeromonas isolates were susceptible to varied antimicrobial agents, except ampicillin/sulbactam.

CONCLUSION

A. veronii is the predominant species in stools from individuals with or without diarrhea in southern Taiwan.

Monomicrobial Aeromonas and Vibrio bacteremia in cirrhotic adults in southern Taiwan: Similarities and differences

BACKGROUND/PURPOSE

Aeromonas and Vibrio are important water-borne pathogens causing substantial morbidity and mortality in cirrhotic patients in Taiwan, but the differences in clinical manifestations of Aeromonas and Vibrio bacteremia have not been reported in detail.

METHODS

From January 2003 to September 2013, cirrhotic patients with monomicrobial Aeromonas or Vibrio bacteremia at a medical center in Taiwan were included in this study.

RESULTS

The study population consisted of 77 cirrhotic patients with Aeromonas bacteremia and 48 patients with Vibrio bacteremia. Both pathogens clustered during the summer season; Vibrio bacteremia was more correlated with higher temperatures (Vibrio: r(2) = 0.95, p < 0.0001; Aeromonas: r(2) = 0.74, p = 0.006) and was associated with ingestion of undercooked seafood (p = 0.03) or cutaneous exposure (p < 0.001). Vibrio bacteremia mainly occurred in mildly or moderately decompensated cirrhosis (Child-Pugh class A and B: 45.8% vs. 20.8%, p = 0.003), and caused more soft-tissue infections (31.3% vs. 5.2%; p < 0.001) and renal dysfunction (1.6 ± 1.2 mg/dL vs. 1.3 ± 0.8 mg/dL, p = 0.006). Sepsis-related mortality was similar in the cases of Vibrio and Aeromonas bacteremia (14.6% vs. 14.3%, p = 0.96), but those with Vibrio bacteremia underwent a fulminant course, as evidenced by a shorter time from bacteremia onset to death (3.1 days vs. 8.2 days, p = 0.04).

CONCLUSION

In cirrhotic patients, bacteremia caused by Aeromonas and Vibrio species clustered in summer months and caused similar mortality, but Vibrio bacteremia led to a more severe and fulminant sepsis.

Clinical manifestations of bacteremia caused by Aeromonas species in southern Taiwan

Aim

This study is conducted to investigate the clinical characteristics of patients with bacteremia caused by Aeromonas species.

Materials and Methods

Patients with bacteremia caused by Aeromonas species during the period 2009 to 2013 were identified from a computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed.

Results

A total of 91 patients with bacteremia due to Aeromonas species were identified. In addition to 16 (17.6%) primary bacteremia, the most common source of secondary infection is peritonitis (n = 27, 29.7%), followed by biliary tract infection (n = 18, 19.8%), and SSTI (n = 12, 13.2%), pneumonia (n = 9, 9.9%), catheter-related bloodstream infection (n =  5, 5.5%), and genitourinary tract infection (n = 4, 4.4%). A. hydrophila (n = 35, 38.5%) was the most common pathogen, followed by A. veronii biovar sobria (n = 31, 34.1%), A. caviae (n = 14, 15.4%), and A. veronii biovar veronii (n = 9, 9.9%). Forty-three (47.3%) patients were classified as healthcare-associated infections (HCAI) causes by Aeromonas species, and patients with HCAI were more likely to have cancer, and receive immunosuppressant than patients with community-acquired bacteremia. The overall outcomes, including rate of ICU admission, acute respiratory failure, and mortality were 33.3%, 28.6%, and 23.1%, respectively. Multivariate analysis showed that the in-hospital day mortality was significantly associated only with underlying cancer (P <.001), and initial shock (P <.001).

Conclusions

Aeromonas species should be considered one of the causative pathogens of healthcare-associated bacteremia, especially in immunocompromised patients. In addition, it can be associated with high fatality. Cancer and initial shock were the poor prognostic factors.