Necrotizing fasciitis caused by Aeromonas hydrophila

Aeromonas hydrophila orbital cellulitis as post cesarean sepsis-An unthinkable eye opener

Peripartum orbital cellulitis and pan ophthalmitis are rare complications. Here we report one such case and the need for aggressive management of postpartum infections especially post cesarean.

Garvicin KS, a Broad-Spectrum Bacteriocin Protects Zebrafish Larvae against Lactococcus garvieae Infection

Bacteriocins are emerging as a viable alternative to antibiotics due to their ability to inhibit growth or kill antibiotic resistant pathogens. Herein, we evaluated the ability of the bacteriocin Garvicin KS (GarKS) produced by Lactococcus garvieae KS1546 isolated from cow milk to inhibit the growth of fish and foodborne bacterial pathogens. We found that GarKS inhibited the growth of five fish L. garvieae strains isolated from infected trout and eels. Among fish pathogens, GarKS inhibited the growth of Streptococcus agalactiae serotypes Ia and Ib, and Aeromonas hydrophila but did not inhibit the growth of Edwardsiella tarda. In addition, it inhibited the growth of A. salmonicida strain 6421 but not A. salmonicida strain 6422 and Yersinia ruckeri. There was no inhibition of three foodborne bacterial species, namely Salmonella enterica, Klebsiella pneumoniae, and Escherichia coli. In vitro cytotoxicity tests using different GarKS concentrations showed that the highest concentration of 33 µg/mL exhibited low cytotoxicity, while concentrations ≤3.3 µg/mL had no cytotoxicity on CHSE-214 and RTG-2 cells. In vivo tests showed that zebrafish larvae treated with 33 µg/mL and 3.3 µg/mL GarKS prior to challenge had 53% and 48% survival, respectively, while concentrations ≤0.33 µg/mL were nonprotective. Altogether, these data show that GarKS has a broad inhibitory spectrum against Gram positive and negative bacteria and that it has potential applications as a therapeutic agent for a wide range of bacterial pathogens. Thus, future studies should include clinical trials to test the efficacy of GarKS against various bacterial pathogens in farmed fish.

Emergency amputation necessitated within 24 hours by a human bite: a case report

We herein review and analyze the diagnosis, treatment, and outcome of a severe infection caused by a human bite. A 68-year-old man was bitten on the forearm by a 3-year-old child. Rapid progression of infection, severe local and systemic poisoning, and diverse clinical manifestations were observed at presentation. Based on the medical history, physical signs, imaging examinations (X-ray films, color Doppler ultrasound, and computed tomography), laboratory examinations, and multidisciplinary consultation, the patient was diagnosed with gas gangrene or gas gangrene-like changes. Twenty-four hours after the injury, an emergency amputation was performed (open amputation with wound closure after 1 week). After the operation, the patient was sent to the intensive care unit for isolation and further anti-infection and anti-shock treatments. His condition gradually improved after treatment and he was discharged without further complications. Bacteriological and pathological examinations indicated Aeromonas hydrophila infection leading to extensive necrotizing fasciitis of the limb and severe systemic poisoning. In addition, pre-existing myelodysplastic syndrome progressing to acute myeloid leukemia was identified as a possible predisposing factor. Human bites can cause serious infections requiring timely treatment, particularly in patients with predisposing comorbidities.

Necrotizing fasciitis secondary to lake water inoculation with Aeromonas sobria: A case report

RATIONALE

Necrotizing fasciitis (NF) is a rapidly progressing bacterial soft tissue infection with a high mortality rate. It is characterized by significant soft tissue destruction with associated sepsis. The mainstay of treatment is coverage with appropriate broad-spectrum antibiotic therapy and emergent surgical debridement.

PATIENT CONCERNS

A previously healthy 66-year-old female presented with a deep laceration to her right, posterior calf with subsequent contamination with lake water. After the wound was irrigated and closed, the patient developed NF.

DIAGNOSIS

Laceration of the right lower extremity complicated by NF secondary to Aeromonas sobria.

INTERVENTIONS

The patient underwent emergent surgical debridements with intravenous broad-spectrum antibiotics and negative pressure wound therapy. The lower extremity was reconstructed with split-thickness skin grafts.

OUTCOMES

The patient's initial penetrating trauma was closed in the emergency room, and the patient was discharged home with antibiotics. She returned the next day with unstable vitals and was admitted to the intensive care unit. Her condition continued to deteriorate, and she underwent serial surgical debridements. Her condition improved and was discharged home after 13 days in the hospital.

LESSONS LEARNED

Close monitoring for NF is important for tissue infections sustained in aquatic environments. Timely identification and surgical management of NF increases overall survival.

Necrotizing Fasciitis Caused by Aeromonas hydrophila With Catastrophic Progression

Necrotizing fasciitis is a severe deep soft tissue infection with poor disease prognosis. The Aeromonas species is characterized as gram-negative, facultative, anaerobic small bacilli that are ubiquitously distributed in aquatic environments. Necrotizing fasciitis caused by this species is rare but has an extremely high mortality rate, especially in immunocompromised individuals. This study presents the case of a 39-year-old man with alcoholic liver cirrhosis, Child-Pugh class B, with necrotizing fasciitis caused by Aeromonas hydrophila. Despite debridement and bilateral above-knee amputation performed immediately, rapid progression to bilateral upper limbs and trunk was noted in 24 hours. The patient expired from septic shock with multiple organ failure in less than 48 hours following initial presentation. Two similar cases with different medical intervention and results have been reported in the literature and are further discussed in the present study. This allows the authors to suggest potential solutions for an improved clinical outcome.

Expression of a Shiga-Like Toxin during Plastic Colonization by Two Multidrug-Resistant Bacteria, Aeromonas hydrophila RIT668 and Citrobacter freundii RIT669, Isolated from Endangered Turtles (Clemmys guttata)

Aeromonas hydrophila RIT668 and Citrobacter freundii RIT669 were isolated from endangered spotted turtles (Clemmys guttata). Whole-genome sequencing, annotation and phylogenetic analyses of the genomes revealed that the closest relative of RIT668 is A. hydrophila ATCC 7966 and Citrobacter portucalensis A60 for RIT669. Resistome analysis showed that A. hydrophila and C. freundii harbor six and 19 different antibiotic resistance genes, respectively. Both bacteria colonize polyethylene and polypropylene, which are common plastics, found in the environment and are used to fabricate medical devices. The expression of six biofilm-related genes—biofilm peroxide resistance protein (bsmA), biofilm formation regulatory protein subunit R (bssR), biofilm formation regulatory protein subunit S (bssS), biofilm formation regulator (hmsP), toxin-antitoxin biofilm protein (tabA) and transcriptional activator of curli operon (csgD)—and two virulence factors—Vi antigen-related gene (viaB) and Shiga-like toxin (slt-II)—was investigated by RT-PCR. A. hydrophila displayed a > 2-fold increase in slt-II expression in cells adhering to both polymers, C. freundii adhering on polyethylene displayed a > 2-fold, and on polypropylene a > 6-fold upregulation of slt-II. Thus, the two new isolates are potential pathogens owing to their drug resistance, surface colonization and upregulation of a slt-II-type diarrheal toxin on polymer surfaces.

Comprehensive Analysis Reveals the Evolution and Pathogenicity of Aeromonas, Viewed from Both Single Isolated Species and Microbial Communities

The genus Aeromonas is a common gastrointestinal pathogen associated with human and animal infections. Due to the high level of cross-species similarity, their evolutionary dynamics and genetic diversity are still fragmented. Hereby, we investigated the pan-genomes of 29 Aeromonas species, as well as Aeromonas species in microbial communities, to clarify their evolutionary dynamics and genetic diversity, with special focus on virulence factors and horizontal gene transfer events. Our study revealed an open pan-genome of Aeromonas containing 10,144 gene families. These Aeromonas species exhibited different functional constraints, with the single-copy core genes and most accessory genes experiencing purifying selection. The significant congruence between core genome and pan-genome trees revealed that core genes mainly affected evolutionary divergences of Aeromonas species. Gene gains and losses revealed a high level of genome plasticity, exhibited by hundreds of gene expansions and contractions, horizontally transferred genes, and mobile genetic elements. The selective constraints shaped virulence gene pools of these Aeromonas strains, where genes encoding hemolysin were ubiquitous. Of these strains, Aeromonas aquatica MX16A seemed to be more resistant, as it harbored most resistance genes. Finally, the virulence factors of Aeromonas in microbial communities were quite dynamic in response to environment changes. For example, the virulence diversity of Aeromonas in microbial communities could reach levels that match some of the most virulent Aeromonas species (such as A. hydrophila) in penetrated-air and modified-air packaging. Our work shed some light onto genetic diversity, evolutionary history, and functional features of Aeromonas, which could facilitate the detection and prevention of infections.IMPORTANCE Aeromonas has long been known as a gastrointestinal pathogen, yet it has many species whose evolutionary dynamics and genetic diversity had been unclear until now. We have conducted pan-genome analysis for 29 Aeromonas species and revealed a high level of genome plasticity exhibited by hundreds of gene expansions and contractions, horizontally transferred genes, and mobile genetic elements. These species also contained many virulence factors both identified from single isolated species and microbial community. This pan-genome study could elevate the level for detection and prevention of Aeromonas infections.

Multidrug-resistant Aeromonas hydrophila causing fatal bilateral necrotizing fasciitis in an immunocompromised patient: a case report

BACKGROUND

Aeromonas hydrophila is a water-dwelling, gram-negative rod-shaped bacterium, associated with diarrheal illness and, less commonly, necrotizing skin and soft tissue infections, especially among immunocompromised patients. Necrotizing fasciitis is associated with a high mortality rate, especially when caused by Aeromonas spp. Our patient was infected with an extremely aggressive form of multidrug-resistant Aeromonas spp. that produced both an extended-spectrum β-lactamase and an AmpC enzyme. Aeromonads are being recognized as important emerging pathogens because of their inherent antibiotic resistance profiles compounded by other virulence factors. These difficult-to-treat organisms can have significant implications in both clinical and public health settings.

CASE PRESENTATION

A 37-year-old Caucasian male with immunosuppression due to aplastic anemia being treated with cyclosporine, presented to hospital with relapsed disease. While in hospital, he subsequently developed overwhelming sepsis secondary to bilateral lower extremity necrotizing fasciitis. The necrotizing fasciitis was caused by a multidrug-resistant strain of A. hydrophila. Despite broad-spectrum antibiotics and aggressive surgical debridement, he succumbed to this severe invasive infection.

CONCLUSIONS

Necrotizing fasciitis caused by Aeromonas spp. is a rare infection that may have a poor clinical outcome, particularly if the diagnosis is delayed and/or the organism is highly virulent and multidrug resistant. Enhanced education of clinicians and microbiologists is required to prevent unnecessary complications and improve survival.

Oral Microbiota of the Snake Bothrops lanceolatus in Martinique

In Martinique, Bothrops lanceolatus snakebite, although relatively uncommon (~30 cases/year), may result in serious complications such as systemic thrombosis and local infections. Infections have been hypothesized to be related to bacteria present in the snake’s oral cavity. In this investigation, we isolated, identified, and studied the susceptibility to beta-lactams of bacteria sampled from the oral cavity of twenty-six B. lanceolatus specimens collected from various areas in Martinique. Microbiota from B. lanceolatus oral cavity was polymicrobial. Isolated bacteria belonged to fifteen different taxa; the most frequent being Aeromonas hydrophyla (present in 50% of the samples), Morganella morganii, Klebsiella pneumoniae, Bacillus spp., and Enterococcus spp. Analysis of antibiotic susceptibility revealed that 66.7% of the isolated bacteria were resistant to amoxicillin/clavulanate. In contrast, the majority of isolated bacteria were susceptible to the third-generation cephalosporins (i.e., 73.3% with cefotaxime and 80.0% with ceftazidime). Microbiota from B. lanceolatus oral cavity is polymicrobial with bacteria mostly susceptible to third-generation cephalosporins but rarely to amoxicillin/clavulanate. In conclusion, our findings clearly support that first-line antibiotic therapy in the B. lanceolatus-bitten patients, when there is evidence of infection, should include a third-generation cephalosporin rather than amoxicillin/clavulanate.

Bone graft donor site infection with a rare organism, Aeromonas Hydrophila. A typical location, presentation and organism with 2 years follow-up. Case report

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A. Hydrophila found in immunocompromised patients, burns or aquatic trauma patients.

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Aeromonas produce β-lactamase making it resistant to usual prophylactic antibiotics.

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Early surgical and antibiotic treatment is essential.

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Following a multidisciplinary approach, these patients avoid catastrophic results.

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Combined case report with detailed review of A. Hydrophila from recent literature.

Introduction

Aeromonas are Gram-negative bacilli often causing necrotizing fasciitis or sepsis in immunocompromised patients. Aeromonas Hydrophila is most often found in immunocompromised patients or those with burns or aquatic trauma. When patients present with a discharge and infection on bone graft donor site and progressive sepsis, an Aeromonas hydrophila infection should be considered in the differential diagnosis.

Presentation of case

We report here a rare case of Aeromonas hydrophila with surgical site sepsis/infection in an immunocompromised 69 years old female, with several comorbids. Here we are reporting infection on donor surgical graft site, sparing major surgical site with the implant. After getting culture report of exudates from the wound that grew A. hydrophila, immediate wound debridement and antibiotic beads insertion was performed with appropriate antimicrobial therapy and regular wound dressing. She was followed for around 2 years.

Discussion

This is the first report to our knowledge of A. Hydrophila infection in bone graft donor site. Aeromonas most often cause gastrointestinal and soft tissue infections, and bacteremia in immunocompromised patients. Early surgical intervention is essential to reducing mortality in deep soft tissue infections caused by this organism. Aeromonas have shown resistance to penicillin but are sensitive to other broad-spectrum antibiotics.

Conclusion

Early suspicion, diagnosis, and treatment with potent antibiotics are needed to prevent any further complications resulting from infection by this emerging aggressive pathogen.

Intestinal bacteria in bioaerosols and factors affecting their survival in two oxidation ditch process municipal wastewater treatment plants located in different regions

Samples from two oxidation ditch process municipal wastewater treatment plants (MWTPs) (HJK and GXQ) in two regions of China were analysed for bacteria, particles, total organic carbon, and water-soluble ions in bioaerosols. Diversity and potential pathogen populations were evaluated by high-throughput sequencing. Bioaerosol sources, factors affecting intestinal bacterial survival, and the relationship between bioaerosols and water were analysed by Source tracker and partial least squares-discriminant, principal component, and canonical correspondence analyses. Culturable bacteria concentrations were 110-846 and 27-579 CFU/m³ at HJK and GXQ, respectively. Intestinal bacteria constituted 6-33% of bacteria. Biochemical reaction tank, sludge dewatering house (SDH), and fine screen samples showed the greatest contribution to bioaerosol contamination. Enterobacter aerogenes was the main intestinal bacteria (> 99.5%) in HJK and detected at each sampling site. Enterobacter aerogenes (98.67% in SDH), Aeromonas sp. (76.3% in biochemical reaction tank), and Acinetobacter baumannii (99.89% in fine screens) were the main intestinal bacteria in GXQ. Total suspended particulate masses in SDH were 229.46 and 141.6 μg/m³ in HJK and GXQ, respectively. Percentages of insoluble compounds in total suspended particulates decreased as height increased. The main soluble ions in bioaerosols were Ca²⁺, Na⁺, Cl^-, and SO₄^2-, which ranged from 3.8 to 27.55 μg/m³ in the MWTPs. Water was a main source of intestinal bacteria in bioaerosols from the MWTPs. Bioaerosols in HJK but not in GXQ were closely related. Relative humidity and some ions positively influenced intestinal bacteria in bioaerosols, while wind speed and solar illumination had a negative influence.

Vertical and horizontal assemblage patterns of bacterial communities in a eutrophic river receiving domestic wastewater in southeast China

Bacterial communities in rivers receiving untreated domestic wastewater may show specific spatial assemblage patterns due to a wide range of physicochemical conditions created by periodic algal bloom. However, there are significant gaps in understanding environmental forces that drive changes in microbial assemblages in polluted rivers. In this study, we applied high-throughput sequencing of 16S rRNA gene amplicons to perform comprehensive spatio-temporal profiling of bacterial community structure in a local river segment receiving domestic wastewater discharge in southeast China. Multivariate statistics were then used to analyse links between bacterial community structure and environmental factors. Non-metric multidimensional scaling (NMDS) plots showed that the bacterial community structure was different between upstream and downstream sections of the river. While the upstream water contained a high proportion of bacteria degrading xenobiotic aromatic compounds, the downstream water experiencing stronger algal bloom had a more diverse bacterial community which included the genus Aeromonas comprising 14 species, most of which are human pathogens. Least discriminant analysis (LDA) effect size revealed that the surface water was mainly inhabited by aerobic microorganisms capable of degrading aromatic compounds, and also contained bacterial genera including pathogenic species. In contrast, in the bottom water we found, along with aromatic compound-degrading species, anaerobic denitrifiers and Fe³⁺-reducing and fermentative bacteria. Variance partitioning canonical correspondence analysis (VPA) showed that nutrient ratios had a stronger contribution to bacterial dissimilarities than other major physicochemical factors (temperature, pH, dissolved oxygen, total organic carbon, and chlorophyll a). These results show that microbial communities in rivers continuously receiving domestic wastewater have specific longitudinal and vertical assemblage patterns and may contain pathogenic species presenting a high threat to public health. These factors should be taken into consideration while developing pollution management strategies.

Aeromonas dhakensis, an Increasingly Recognized Human Pathogen

Aeromonas dhakensis was first isolated from children with diarrhea in Dhaka, Bangladesh and described in 2002. In the past decade, increasing evidence indicate this species is widely distributed in the environment and can cause a variety of infections both in human and animals, especially in coastal areas. A. dhakensis is often misidentified as A. hydrophila, A. veronii, or A. caviae by commercial phenotypic tests in the clinical laboratory. Correct identification relies on molecular methods. Increasingly used matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) may be able to identify Aeromonas specie rapidly and accurately. A. dhakensis has shown its potent virulence in different animal models and clinical infections. Although several virulence factors had been reported, no single mechanism is conclusive. Characteristically A. dhakensis is the principal species causing soft tissue infection and bacteremia, especially among patients with liver cirrhosis or malignancy. Of note, A. dhakensis bacteremia is more lethal than bacteremia due to other Aeromonas species. The role of this species in gastroenteritis remains controversial. Third generation cephalosporins and carbapenems should be used cautiously in the treatment of severe A. dhakensis infection due to the presence of AmpC ββ-lactamase and metallo-β-lactamase genes, and optimal regimens may be cefepime or fluoroquinolones. Studies of bacterial virulence factors and associated host responses may provide the chance to understand the heterogeneous virulence between species. The hypothesis A. dhakensis with varied geographic prevalence and enhanced virulence that compared to other Aeromonas species warrants more investigations.

Cross-talk among flesh-eating Aeromonas hydrophila strains in mixed infection leading to necrotizing fasciitis

Necrotizing fasciitis (NF) caused by flesh-eating bacteria is associated with high case fatality. In an earlier study, we reported infection of an immunocompetent individual with multiple strains of Aeromonas hydrophila (NF1-NF4), the latter three constituted a clonal group whereas NF1 was phylogenetically distinct. To understand the complex interactions of these strains in NF pathophysiology, a mouse model was used, whereby either single or mixed A. hydrophila strains were injected intramuscularly. NF2, which harbors exotoxin A (exoA) gene, was highly virulent when injected alone, but its virulence was attenuated in the presence of NF1 (exoA-minus). NF1 alone, although not lethal to animals, became highly virulent when combined with NF2, its virulence augmented by cis-exoA expression when injected alone in mice. Based on metagenomics and microbiological analyses, it was found that, in mixed infection, NF1 selectively disseminated to mouse peripheral organs, whereas the other strains (NF2, NF3, and NF4) were confined to the injection site and eventually cleared. In vitro studies showed NF2 to be more effectively phagocytized and killed by macrophages than NF1. NF1 inhibited growth of NF2 on solid media, but ExoA of NF2 augmented virulence of NF1 and the presence of NF1 facilitated clearance of NF2 from animals either by enhanced priming of host immune system or direct killing via a contact-dependent mechanism.

Non-pathogenic microflora of a spring water with regenerative properties

The Comano spring water (Comano, Italy) has been demonstrated to improve skin regeneration, not only by increasing keratinocyte proliferation and migration, but also by modulating the regenerated collagen and elastic fibers in the dermis. However, such biological properties may not be entirely explained by its mineral composition only. As the non-pathogenic bacterial populations have demonstrated an active role in different biological processes, the potential presence of non-pathogenic bacterial species within the Comano spring water was investigated in order to identify any possible correlation between these bacterial populations and the demonstrated biological properties of this water. The water was collected at the spring using an aseptic procedure and multiple cultures were carried out. A total of 9 different strains were isolated, which were Aeromonas hydrophila, Brevundimonas vesicularis, Chromobacterium violaceum, Citrobacter youngae, Empedobacter brevis, Pantoea agglomerans, Pseudomonas putida, Pseudomonas stutzeri and Streptococcus mitis. All the isolated bacterial strains, although showing a rare potential virulence, demonstrated peculiar and favorable metabolic attitudes in controlling environmental pollution. The therapeutical effects of certain spring waters are currently being proven as correlated not only to their peculiar mineral composition, but also to the complex activity of their resident non-pathogenic bacterial populations. Although the present study provided only preliminary data, some of the non-pathogenic bacterial populations that were identified in the Comano spring water are likely to produce molecular mediators with a role in the wound healing process that, thus far, remain unknown. Numerous other unknown bacterial species, comprehensively termed DNA-rich 'dark matter', are likely to contribute to the Comano water regenerative properties as well. Therefore, the non-pathogenic bacterial populations of the Comano spring water are possibly credited for its demonstrated regenerative properties.

A Severe Accident Caused by an Ocellate River Stingray (Potamotrygon motoro) in Central Brazil: How Well Do We Really Understand Stingray Venom Chemistry, Envenomation, and Therapeutics?

Freshwater stingrays cause many serious human injuries, but identification of the offending species is uncommon. The present case involved a large freshwater stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in the Araguaia River in Tocantins, Brazil. Appropriate first aid was administered within ~15 min, except that an ice pack was applied. Analgesics provided no pain relief, although hot compresses did. Ciprofloxacin therapy commenced after ~18 h and continued seven days. Then antibiotic was suspended; however, after two more days and additional tests, cephalosporin therapy was initiated, and proved successful. Pain worsened despite increasingly powerful analgesics, until debridement of the wound was performed after one month. The wound finally closed ~70 days after the accident, but the patient continued to have problems wearing shoes even eight months later. Chemistry and pharmacology of Potamotrygon venom and mucus, and clinical management of freshwater stingray envenomations are reviewed in light of the present case. Bacterial infections of stingray puncture wounds may account for more long-term morbidity than stingray venom. Simultaneous prophylactic use of multiple antibiotics is recommended for all but the most superficial stingray wounds. Distinguishing relative contributions of venom, mucus, and bacteria will require careful genomic and transcriptomic investigations of stingray tissues and contaminating bacteria.

Necrotizing soft tissue infection following a peripheral bypass

BACKGROUND

Necrotizing soft tissue infection (NSTI), formerly referred to as necrotizing fasciitis, is a rare but serious postoperative complication. NSTI following arterial bypass is seen only once in the literature (for a coronary artery bypass) and is not mentioned following peripheral bypass. Although surgical site infections have been studied extensively, there are limited published data on postoperative NSTI and no data for NSTI following peripheral arterial bypass.

CASE PRESENTATION

Here we present the first, to our knowledge, reported instance of an NSTI following a lower extremity peripheral bypass. Despite the continued function of the bypass, the patient became rapidly systemically ill with a focus at the surgical site. Because of prompt surgical debridement, the patient survived this severe infection, though did require an above the knee amputation to control the rapid spread of the disease. The patient, a native of American Samoa, was infected with organisms infrequently associated with NSTI, Morganella morganii and Aeromonas hydrophila. This article discusses the diagnosis and treatment of this rare postoperative complication, along with a brief review of the microbiology of the disease.

CONCLUSIONS

NSTI is a rare but lethal postoperative complication. To our knowledge, this is the first reported case of an NSTI following an arterial peripheral bypass. This patient survived because of prompt and aggressive intervention.

Tetanus after envenomations caused by freshwater stingrays

Injuries caused by freshwater stingray are common in several regions of South America, although they are underreported. The riverside inhabitants are the main victims in the Amazonian and Midwest regions of South America. The fishermen are injured mainly in the new focus of colonization of the rivers by freshwater stingrays. With the increasing population in these regions, where freshwater stingrays are found, there has been a significant increase in injuries within the general population. The highest increase occurred among tourists from other regions, where these animals are not known, when visiting these areas. The envenomations from the stingray causes prolonged and intense pain, both local and regionally. Generally these are associated with other local inflammatory manifestations, such as swelling and erythema. The injury often progresses to necrosis and it is considered potentially tetanogenic. A secondary infection is also a frequent local complication and most frequently is caused by Aeromonas species, usually Aeromonas hydrophila. Herein we report the first 2 cases of tetanus after freshwater stingray injuries: a 51-year-old men who had tetanus and recovered without sequel and the second a 67-year-old men who had severe tetanus and a deep, necrotizing soft-tissue infection with sepsis, septic shock and evolution to death.

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.

Potential application of algicidal bacteria for improved lipid recovery with specific algae

The utility of specific strains of natural algicidal bacteria isolated from shallow wetland sediments was evaluated against several strains of algae with potential immediate or future commercial value. Two strains of bacteria, Pseudomonas pseudoalcaligenes AD6 and Aeromonas hydrophila AD9, were identified and demonstrated to have algicidal activity against the microalgae Neochloris oleoabundans and Dunaliella tertiolecta. These bacteria were further evaluated for the potential to improve lipid extraction using a mild solvent extraction approach. Aeromonas hydrophila AD9 showed a nearly 12-fold increase in lipid extraction with D. tertiolecta, while both bacteria showed a sixfold improvement in lipid extraction with N. oleoabundans.

Necrotizing fasciitis: eight-year experience and literature review

Objectives

To describe clinical, laboratory, microbiological features, and outcomes of necrotizing fasciitis.

Methods

From January 1, 2004 to December 31, 2011, 115 patients (79 males, 36 females) diagnosed with necrotizing fasciitis were admitted to Mackay Memorial Hospital in Taitung. Demographic data, clinical features, location of infection, type of comorbidities, microbiology and laboratory results, and outcomes of patients were retrospectively analyzed.

Results

Among 115 cases, 91 survived (79.1%) and 24 died (20.9%). There were 67 males (73.6%) and 24 females (26.4%) with a median age of 54 years (inter-quartile ranges, 44.0–68.0 years) in the survival group; and 12 males (50%) and 12 females (50%) with a median age of 61 years (inter-quartile ranges, 55.5–71.5 years) in the non-surviving group. The most common symptoms were local swelling/erythema, fever, pain/tenderness in 92 (80%), 87 (76%) and 84 (73%) patients, respectively. The most common comorbidies were liver cirrhosis in 54 patients (47%) and diabetes mellitus in 45 patients (39%). A single organism was identified in 70 patients (61%), multiple pathogens were isolated in 20 patients (17%), and no microorganism was identified in 30 patients (26%). The significant risk factors were gender, hospital length of stay, and albumin level.

Discussion

Necrotizing fasciitis, although not common, can cause notable rates of morbidity and mortality. It is important to have a high index of suspicion and increase awareness in view of the paucity of specific cutaneous findings early in the course of the disease. Prompt diagnosis and early operative debridement with adequate antibiotics are vital.

Modulation of host immune defenses by Aeromonas and Yersinia species: convergence on toxins secreted by various secretion systems

Like other pathogenic bacteria, Yersinia and Aeromonas species have been continuously co-evolving with their respective hosts. Although the former is a bonafide human pathogen, the latter has gained notararity as an emerging disease-causing agent. In response to immune cell challenges, bacterial pathogens have developed diverse mechanism(s) enabling their survival, and, at times, dominance over various host immune defense systems. The bacterial type three secretion system (T3SS) is evolutionarily derived from flagellar subunits and serves as a vehicle by which microbes can directly inject/translocate anti-host factors/effector proteins into targeted host immune cells. A large number of Gram-negative bacterial pathogens possess a T3SS empowering them to disrupt host cell signaling, actin cytoskeleton re-arrangements, and even to induce host-cell apoptotic and pyroptotic pathways. All pathogenic yersiniae and most Aeromonas species possess a T3SS, but they also possess T2- and T6-secreted toxins/effector proteins. This review will focus on the mechanisms by which the T3SS effectors Yersinia outer membrane protein J (YopJ) and an Aeromonas hydrophila AexU protein, isolated from the diarrheal isolate SSU, mollify host immune system defenses. Additionally, the mechanisms that are associated with host cell apoptosis/pyroptosis by Aeromonas T2SS secreted Act, a cytotoxic enterotoxin, and Hemolysin co-regulated protein (Hcp), an A. hydrophila T6SS effector, will also be discussed.

Enterobacter asburiae and Aeromonas hydrophila: soft tissue infection requiring debridement

Enterobacter asburiae and Aeromonas hydrophila are gram-negative bacilli that have been isolated in soil and water. Enterobacter asburiae can cause an array of diseases, and exposure to A hydrophila can cause soft tissue infections, including necrotizing faciitis.A healthy-appearing 22-year-old man presented with an innocuous soft tissue injury to his leg due to an all-terrain vehicle crash. He received intravenous antibiotics and was discharged with prophylactic oral antibiotics. After the rapid onset of high fevers (102°F-103°F) <24 hours postinjury, he returned to the emergency department. Emergent surgical debridement was performed, and broad-spectrum intravenous antibiotics were started. Fevers persisted, and the patient underwent repeat extensive surgical debridement and antibiotic bead placement <30 hours after the initial surgical debridement and broad-spectrum antibiotics. Intraoperative cultures found E asburiae and A hydrophila in the wound. Following a long course of antibiotics and a skin graft, he fully recovered and had no functional deficits 1 year postoperatively.Extensive research revealed that these organisms are rare in soft tissue infections. E asburiae is opportunistic but has not been reported as a primary wound organism, and A hydrophila infections have been reported following motor vehicle crashes involving wound contamination. At presentation, it is challenging to determine rare organisms in a timely fashion; however, emergent extensive surgical intervention of an accelerated aberrant disease process should be considered to avoid catastrophic outcomes.

Characterization of Aeromonas species isolated from an estuarine environment

Thirty water samples were collected, at two week intervals, from the estuary of the River Cocó. The aim was to characterize the presence, distribution and types of Aeromonas spp, in the estuary of the River Cocó, Ceara, Brazil (03°46’28.83’’S e 38°26’36.52’’S). Aeromonas were identified in 19 (63%) samples analyzed by plating and CFU counts. Presence/absence tests were positive for 11 (37%) of the samples resulting in the detection of Aeromonas in a total of 23 (77%) of samples. CFU counts varied from < 10 to 1.4 x 10⁴ CFU mL^-1. From the isolated strains seven species of Aeromonas were identified: A. caviae (29/69), A. veronii bv. sobria (13/69), A. veronii bv. veronii (8/69), A. trota (6/69), A. media (5/69), A. sobria (4/69) and A. hydrophila and Aeromonas sp. (2/69). Of the 38 strains tested, 23 (60%) showed resistance to at least one of the eight antimicrobials. Multiple resistance to antibiotics was observed in A. caviae, A. media , A. sóbria and A. veronii bv. sobria. Aeromonas caviae showed the highest multiple resistance, being resistant to four antibiotics. The presence of those microorganisms may contribute to the occurrence of gastroenteritis, mainly in children, since they are considered opportunists.

The genus Aeromonas: taxonomy, pathogenicity, and infection

Over the past decade, the genus Aeromonas has undergone a number of significant changes of practical importance to clinical microbiologists and scientists alike. In parallel with the molecular revolution in microbiology, several new species have been identified on a phylogenetic basis, and the genome of the type species, A. hydrophila ATCC 7966, has been sequenced. In addition to established disease associations, Aeromonas has been shown to be a significant cause of infections associated with natural disasters (hurricanes, tsunamis, and earthquakes) and has been linked to emerging or new illnesses, including near-drowning events, prostatitis, and hemolytic-uremic syndrome. Despite these achievements, issues still remain regarding the role that Aeromonas plays in bacterial gastroenteritis, the extent to which species identification should be attempted in the clinical laboratory, and laboratory reporting of test results from contaminated body sites containing aeromonads. This article provides an extensive review of these topics, in addition to others, such as taxonomic issues, microbial pathogenicity, and antimicrobial resistance markers.

Severe soft tissue infections

Severe skin and soft tissue infections (SSTIs) frequently require management in the ICU, in part related to associated septic shock or toxic shock syndrome or associated organ failure. Four fundamental management principles are key to a successful outcome in caring for patients who have severe SSTIs, including (1) early diagnosis and differentiation of necrotizing versus nonnecrotizing SSTI, (2) early initiation of appropriate empiric broad-spectrum antimicrobial therapy with consideration of risk factors for specific pathogens and mandatory coverage for methicillin-resistant Staphylococcus aureus (MRSA), (3) source control (ie, early aggressive surgical intervention for drainage of abscesses and debridement of necrotizing soft tissue infections), and (4) pathogen identification and appropriate de-escalation of antimicrobial therapy. MRSA has emerged as the most common identifiable cause of severe SSTIs; therefore, initiation of empiric anti-MRSA antimicrobials is warranted in all cases of severe SSTIs. In addition, appropriate critical care management-including fluid resuscitation, organ support and nutritional support-is a necessary component in treating severe SSTIs.

Case reports: fatal necrotizing fasciitis caused by Aeromonas sobria in two diabetic patients

We report two rare cases of Aeromonas sobria necrotizing fasciitis with sepsis in patients with diabetes. In both cases, immediate fasciotomy was performed and appropriate empiric antimicrobial therapy and intensive care were administered. However, the two patients died on Day 2 and Day 11, respectively, after admission as a result of multiple organ failure. When patients present with a rapid onset of skin necrosis and progressive sepsis, an Aeromonas sobria infection or Vibrio infection should be considered in the differential diagnosis.

Necrotizing fasciitis and sepsis caused by Aeromonas hydrophila after crush injury of the lower extremity

BACKGROUND

Aeromonas hydrophila is a motile gram-negative bacillus found in water sources that typically causes minor skin infections or gastroenteritis in humans. There are sporadic reports of cases of sepsis or necrotizing fasciitis caused by A. hydrophila but no other cases of severe infection secondary to trauma. The mortality rate of septic shock caused by A. hydrophila approaches 100%.

METHODS

Case report and review of pertinent literature.

RESULTS AND CONCLUSIONS

A patient recently seen at our institution illustrates the features of necrotizing fasciitis and sepsis caused by A. hydrophila after an open femur fracture. We describe the aggressive multi-modality treatment necessary to maximize the likelihood of survival.

Necrotizing soft-tissue infections and sepsis caused by Vibrio vulnificus compared with those caused by Aeromonas species

BACKGROUND

Vibrio and Aeromonas species, which can cause necrotizing fasciitis and primary septicemia, are members of the Vibrionaceae family and thrive in aquatic environments. Because the clinical symptoms and signs of necrotizing fasciitis and sepsis caused by these two bacteria are similar, the purposes of this study were to describe the clinical characteristics of Vibrio vulnificus and Aeromonas infections, to analyze the risk factors for death, and to compare the effects of surgical treatment on the outcome.

METHODS

The cases of thirty-two patients with necrotizing soft-tissue infections and sepsis caused by Vibrio vulnificus (seventeen patients) and Aeromonas species (fifteen patients) were retrospectively reviewed over a four-year period. Surgical débridement or immediate limb amputation was initially performed in all patients. Demographic data, underlying diseases, laboratory results, and clinical outcome were analyzed for each patient in both groups.

RESULTS

Six patients in the Vibrio vulnificus group and four patients in the Aeromonas group died. The patients who died had significantly lower serum albumin levels than did the patients who survived (p < 0.05). The patients with a combination of hepatic dysfunction and diabetes mellitus had a higher mortality rate than those with either hepatic disease or diabetes mellitus alone (p < 0.05). The patients with Vibrio vulnificus infections had a significantly lower systolic blood pressure at presentation (p = 0.006). The patients with Aeromonas infections who died had significantly lower white blood-cell counts (p = 0.03) with significantly fewer numbers of segmented white blood cells than those who died in the Vibrio vulnificus group (p = 0.01).

CONCLUSIONS

The contact history of patients with a rapid onset of cellulitis can alert clinicians to a differential diagnosis of soft-tissue infection with Vibrio vulnificus (contact with seawater or raw seafood) or Aeromonas species (contact with fresh or brackish water, soil, or wood). Early fasciotomy and culture-directed antimicrobial therapy should be aggressively performed in those patients with hypotensive shock, leukopenia, severe hypoalbuminemia, and underlying chronic illness, especially a combination of hepatic dysfunction and diabetes mellitus.

Clinical significance and distribution of putative virulence markers of 116 consecutive clinical Aeromonas isolates in southern Taiwan

OBJECTIVES

The objectives of this study were to elucidate the clinical manifestations of Aeromonas infections and the association of putative virulence genes with clinical invasiveness.

METHODS

116 consecutive clinical Aeromonas isolates collected from July 1999 to June 2001 in a medical center in southern Taiwan were included. All isolates were identified by biochemical phenotyping and their genomic sequences encoding eight putative virulence factors, including cytolytic enterotoxin (AHCYTOEN), aerolysin (aerA), hemolysin (hlyA), heat-labile enterotoxin (alt), heat-stable enterotoxin (ast), and components of type III secretion system (ascV, aexT and ascF-ascG) were analyzed using polymerase chain reaction and colony blot hybridization. The association of clinical diseases of the patients with the putative virulence genes in the isolates was analyzed.

RESULTS

Sixty-two percent of Aeromonas isolates caused clinically evident infections, of which the major clinical manifestations were primary bacteremia (40%), followed by soft tissue infections (27%), and hepatobiliary tract infections (15%). Liver cirrhosis (36%), malignancy (25%), and hepatobiliary diseases (13%) were the major underlying diseases in patients with Aeromonas bacteremia. The majority (64%) of patients with Aeromonas hepatobiliary infections had underlying hepatobiliary diseases, whereas 71% of those with soft tissue infections had antecedent water- or soil-related injuries. The crude fatality rate for Aeromonas infections was 26%. Aeromonas hydrophila complex was the most common (52%) of the three major complex groups investigated, followed by Aeromonas sobria complex (24%) and Aeromonas caviae complex (23%). None of the eight putative virulence factors was associated with invasiveness or bacteremia.

CONCLUSIONS

Primary bacteremia, soft tissue infections, and hepatobiliary tract infections are the three major clinical manifestations of invasive Aeromonas infections in southern Taiwan. This study found no association between the presence of AHCYTOEN, aerA, hlyA, alt, ast, ascV, aexT or ascF-ascG genes in Aeromonas isolates and the development of extra-intestinal infections or bacteremia.

Necrotizing fasciitis caused by Aeromonas hydrophilia in an immunocompetent child

Necrotizing fasciitis is a rapidly progressive and potentially fatal infection. It is characterized by extensive subcutaneous and muscle necrosis. Aeromonus hydrophilia is a gram-negative faculatively anaerobic bacillus that is part of the normal flora of nonfecal sewage and is found in most water systems, soil, and fresh brackish water. Necrotizing fasciitis caused by A. hydrophilia have occurred in children who had underlying systemic diseases or immune dysfunction. We report a 14-year-old boy without underlying systemic diseases or immunodeficiency who developed necrotizing fasciitis secondary to A. hydrophilia and he was successfully treated with extensive surgical debridement and systemic antibiotics.

Septic arthritis due to Aeromonas hydrophila: case report and review of the literature

Aeromonas hydrophila is a rare human pathogen, and worldwide, soft tissue infections following water-related injuries are the most common. However, septic arthritis due to A. hydrophila remains uncommon with only seven cases previously reported in the English literature. In this report, we describe the important clinical features, microbiological findings and management of severe septic arthritis of the knee due to A. hydrophila in a healthy 13-year-old girl following an injury sustained in a private fresh water lake. A review of seven previously reported cases of septic arthritis due to A. hydrophila and the present case suggests that the infection commonly affected the knee and the meta-/intercarpal-phalangeal joint and was frequently rapidly progressive following trauma in fresh water and or associated with leukaemia. Second and third generation cephalosporins, gentamicin, trimethoprim, ciprofloxacin and appropriate orthopaedic management should be promptly instituted. After chemical treatment and chlorination, fresh water becomes free of coliforms, but A. hydrophila persists more compared with the other strains of aeromonas, namely A. sobria and A. caviae. Seawater injuries, unlike freshwater injuries, are not usually associated with aeromonas infections. Further workup on the mechanisms of A. hydrophila resistance to chlorination could probably yield useful information in achieving new procedures of preventing and controlling such infections in public and private fresh water recreational facilities.