Clinical significance and outcome of Aeromonas spp. infections among 204 adult patients

A Systematic Review and Meta-Analysis of Aeromonas-Associated Diarrhea Among Children in Asia

Background: Diarrheal illness is a prominent public health worry in developing countries, resulting in high mortality among children. Sociodemographic characteristics and geographic settings are the main effective factors for the increased incidence of childhood diarrhea. Aeromonas is a neglected organism capable of causing dysentery and diarrhea. The aim of this systematic review and meta-analysis was to determine the prevalence of Aeromonas as an agent in the causation of diarrhea in Asian children. Methods: We conducted a systematic review using Web of Science, PubMed, Wiley Online Library, Science Direct, and Google Scholar for peer-reviewed articles published between January 2000 and February 2023. We considered studies that found Aeromonas in diarrheal stool. A random-effects model was used to determine the pooled prevalence of Aeromonas. Results: Our search returned 2,057 articles, with 17 articles from seven Asian nations being included in the systematic review. The pooled prevalence of Aeromonas was 4.5% (95% confidence interval [CI]: 2.9%-6.8%), with heterogeneity (I2 = 96.85; p < 0.001). There was a greater prevalence in areas with high population living in poverty (12.2%; 95% CI: 5.8%-24%) and lower-middle-income countries (5.0%; 95% CI: 2.7%-9.0%). In addition, the prevalence of Aeromonas was greater in South Asia (10.0%; 95% CI: 5.6%-17.2%), in India (12.9%; 95% CI: 6.8%-23%), and in countries with open defecation rate of 5%-25% (11.3%; 95% CI: 6.3%-19.2%). Conclusion: The prevalence of Aeromonas-associated diarrhea in children in Asia estimated in the present study highlighted the high burden of Aeromonas in some parts of Asia.

Clinical Presentation and Outcomes Following Infection With Vibrio spp, Aeromonas spp, Chromobacterium violaceum, and Shewanella spp Water-Associated Organisms in Tropical Australia, 2015-2022

Background

Water-associated bacterial infections cause a wide spectrum of disease. Although many of these infections are typically due to human host commensal Staphylococcal or Streptococcal spp, water exposure can result in infections with environmental gram negatives such as Vibrio spp, Aeromonas spp, Chromobacterium violaceum, and Shewanella spp (collectively VACS).

Methods

We performed a retrospective analysis of the epidemiology, clinical presentation, and outcomes of deep and superficial infections associated with VACS organisms in our health service between 1 January 2015 and 31 December 2023.

Results

We identified 317 patient episodes of infection with VACS organisms over this period. Of these, Aeromonas spp (63%) was the most common, followed by Vibrio spp (19%), Shewanella spp (13%), and C violaceum (5%). The majority were isolated from males (74.4%) and involved the lower limb (67.5%). Mild infections were more common than severe presentations, with only 15 (4.7%) admissions to the intensive care unit and 8 (2.5%) deaths. Colonization occurred in 6.9% of patients, in contrast to the perceived severity of some of these bacteria. Copathogens were common and included Staphylococcus aureus (48%) and enteric bacteria (57%). The majority of patients (60%) had no documented water exposure. Initial empiric antimicrobial therapy presumptively covered the susceptibilities of the isolated organisms in 47.3% of patients; however, a lack of VACS-covering empirical therapy was not associated with readmission.

Conclusions

The isolation of a VACS organism in our setting was often not associated with documented water exposure, which has implications for empiric antimicrobial therapy. Severe disease and death were uncommon.

Evaluation of the prevalence of Aeromonas spp., Campylobacter spp., and Clostridioides difficile in immunocompromised children with diarrhea

AIM

Diarrhea is a common disease in immunocompromised patients and can be associated with greater morbidity and even mortality. Therefore, the present study was designed to determine the prevalence of Aeromonas spp., Campylobacter spp., and C. difficile among immunocompromised children.

METHODS

This study was conducted on 130 stool samples from patients with diarrhea who had defects in the immune system and were referred to Hazrat Masoumeh Children's Hospital in Qom. Demographic information, clinical symptoms, immune status, and duration of chemotherapy were also recorded for each child. DNAs were extracted from the stool, and then direct PCR assays were done by specific primers for the detection of Aeromonas spp., Campylobacter spp., and toxigenic C. difficile, including tcdA/B and cdtA/B genes. Co-infection in patients was also evaluated.

RESULTS

60.8% and 39.2% were male and female, respectively, with a m ± SD age of 56.72 ± 40.49 months. Most cases of immunocompromised states were related to Acute Lymphocytic Leukemia (77.7%) and Non-Hodgkin Lymphoma (14.6%). 93.1% of patients were undergoing chemotherapy during the study. Among patients, most clinical symptoms were related to bloody diarrhea (98.5%) and fever (92.3%). Based on PCR, 14.6, 9.2, and 1.5% were positive for Aeromonas spp., C. difficile, and C. jejuni, respectively. Among the C. difficile-positive cases, the tcdA gene was only detected in one patient. In total, three co-infections were identified, which included Aeromonas spp./C. difficile (tcdA+), C. jejuni/C. difficile, and C. jejuni/Aeromonas spp.

CONCLUSIONS

This is the first study in Iran to investigate the simultaneous prevalence of some pathogens in immunocompromised children with diarrhea. Because Aeromonas spp., Campylobacter spp., and C. difficile are not routinely detected in some laboratories, infections caused by them are underappreciated in the clinic. Our results showed that these pathogens are present in our region and can cause gastroenteritis in children, especially those with underlying diseases. Therefore, increasing the level of hygiene in some areas and controlling bacterial diarrheal diseases should be given more attention by health officials.

Case Report: A rare infection of multidrug-resistant Aeromonas caviae in a pediatric case with acute lymphoblastic leukemia and review of the literature

Aeromonas caviae infection of the bloodstream and intestine is a rare and severe opportunistic infection in immunocompromised people. In Southwest China, we first reported a case of bloodstream and intestinal infection with multidrug-resistant (MDR) Aeromonas caviae in a 4-year-old child with T-cell acute lymphoblastic leukemia. Blood and stool cultures were used to identify the infection. The selection of antibiotics was based on clinical expertise and medication sensitivity tests. We used linezolid, levofloxacin, and polymyxin B to treat the patient aggressively. Aeromonas caviae infection is uncommon in juvenile acute lymphoblastic leukemia. Doctors should be aware of the likelihood of opportunistic infection during the post-chemotherapy bone marrow suppression period. We further conducted a review of the literature and performed a detailed analysis of Aeromonas infection in pediatric leukemia. It is becoming increasingly apparent that antibiotic is abused domestically and abroad, resulting in the sharp increase of MDR bacteria. In general, most of the Aeromonas isolates are susceptible to third- or fourth-generation cephalosporins, aminoglycosides, quinolones, and carbapenem, but drug-resistant strains are being reported increasingly. We summarized the drug resistance rate of Aeromonas caviae and Aeromonas hydrophila in China in the last 10 years. Early recognition and effective treatment will improve prognosis and reduce mortality.

Practice of standardization of CLSI M45 A3 antimicrobial susceptibility testing of Infrequently Isolated or Fastidious Bacteria strains isolated from blood specimens in Guangdong Province 2017-2021

The concentration of antimicrobial agents in environments like water and food has increased rapidly, which led to a rapid increase in antimicrobial resistance levels in the environment. Monitoring of bacterial resistance levels is considered as a necessary means to control the bacterial resistance. Reference standards are critical for antimicrobial susceptibility testing. CLSI M45 A3 standard defines pathogenic microorganisms that cause infections less frequently than those covered by CLSI M02, M07, and M100 as Infrequently Isolated or Fastidious Bacteria and specifies antimicrobial susceptibility testing methods. Our study investigated the epidemiology and antimicrobial susceptibility testing data of Infrequently Isolated or Fastidious Bacteria strains isolated from blood specimens in 70 hospitals in Guangdong Province between 2017 and 2021. We defined testing methods other than those specified in CLSI M45 A3 as "Non-Standardized." The proportion of standardized antimicrobial susceptibility testing for penicillin increased significantly (Corynebacterium spp. 17.4% vs. 50.0% p < 0.05; Micrococcus spp. 50.0% vs. 77.8% p < 0.05; Abiotrophia spp. and Granulicatella spp. 21.4% vs. 90.9% p < 0.001), while for cefotaxime (Corynebacterium spp. 0.0% vs. 45.2% p < 0.05; Abiotrophia spp. and Granulicatella spp. 0.0% vs. 14.3% p = 0.515) and vancomycin increased finitely. Non-standardized methods were used for all other antimicrobials. Due to limitations in the economic and medical environment, some clinical laboratories are unable to fully comply with CLSI M45 A3 standard. We recommend that CLSI should add breakpoints for disk diffusion method to improve the standardization of antimicrobial susceptibility testing.

Nosocomial infections by diverse carbapenemase-producing Aeromonas hydrophila associated with combination of plumbing issues and heat waves

BACKGROUND

Aquatic opportunistic pathogen Aeromonas hydrophila, known to persist in low-nutrient chlorinated waters, can cause life-threatening infections. Two intensive care units experienced a cluster of Aeromonas infections following outdoor temperature spikes coinciding with recurrent plumbing issues, with fatalities due to severe underlying comorbidities co-occurring with extensively-drug resistant (XDR) Aeromonas.

METHODS

We investigated this cluster using whole genome sequencing to assess genetic relatedness of isolates and identify antimicrobial resistance determinants. Three A. hydrophila were isolated from patients staying in or adjacent to rooms with plumbing issues during or immediately after periods of elevated outdoor temperatures. Sinks and faucets were swabbed for culture.

RESULTS

All A. hydrophila clinical isolates exhibited carbapenem resistance but were not genetically related. Diverse resistance determinants corresponding to extensively-drug resistant were found, including co-occurring KPC-3 and VIM-2, OXA-232, and chromosomal CphA-like carbapenemase genes, contributing to major treatment challenges. All 3 patients were treated with multiple antibiotic regimens to overcome various carbapenemase classes and expired due to underlying comorbidities. Environmental culture yielded no Aeromonas.

CONCLUSIONS

While the investigation revealed no singular source of contamination, it supports a possible link between plumbing issues, elevated outdoor temperatures and incidence of nosocomial Aeromonas infections. The diversity of carbapenemase genes detected in these wastewater-derived Aeromonas warrants heightened infection prevention precautions during periods of plumbing problems especially with heat waves.

Construction of an aerolysin-based multi-epitope vaccine against Aeromonas hydrophila: an in silico machine learning and artificial intelligence-supported approach

Aeromonas hydrophila, a gram-negative coccobacillus bacterium, can cause various infections in humans, including septic arthritis, diarrhea (traveler's diarrhea), gastroenteritis, skin and wound infections, meningitis, fulminating septicemia, enterocolitis, peritonitis, and endocarditis. It frequently occurs in aquatic environments and readily contacts humans, leading to high infection rates. This bacterium has exhibited resistance to numerous commercial antibiotics, and no vaccine has yet been developed. Aiming to combat the alarmingly high infection rate, this study utilizes in silico techniques to design a multi-epitope vaccine (MEV) candidate against this bacterium based on its aerolysin toxin, which is the most toxic and highly conserved virulence factor among the Aeromonas species. After retrieval, aerolysin was processed for B-cell and T-cell epitope mapping. Once filtered for toxicity, antigenicity, allergenicity, and solubility, the chosen epitopes were combined with an adjuvant and specific linkers to create a vaccine construct. These linkers and the adjuvant enhance the MEV's ability to elicit robust immune responses. Analyses of the predicted and improved vaccine structure revealed that 75.5%, 19.8%, and 1.3% of its amino acids occupy the most favored, additional allowed, and generously allowed regions, respectively, while its ERRAT score reached nearly 70%. Docking simulations showed the MEV exhibiting the highest interaction and binding energies (-1,023.4 kcal/mol, -923.2 kcal/mol, and -988.3 kcal/mol) with TLR-4, MHC-I, and MHC-II receptors. Further molecular dynamics simulations demonstrated the docked complexes' remarkable stability and maximum interactions, i.e., uniform RMSD, fluctuated RMSF, and lowest binding net energy. In silico models also predict the vaccine will stimulate a variety of immunological pathways following administration. These analyses suggest the vaccine's efficacy in inducing robust immune responses against A. hydrophila. With high solubility and no predicted allergic responses or toxicity, it appears safe for administration in both healthy and A. hydrophila-infected individuals.

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.

Dissecting bloodstream infections in febrile neutropenic patients with hematological malignancies, a decade-long single center retrospective observational study (2009-2019)

BACKGROUND

The use of ill-suited antibiotics is a significant risk factor behind the increase in the mortality, morbidity, and economic burden for patients who are under treatment for hematological malignancy (HM) and bloodstream infections (BSI). Such unfitting treatment choices intensify the evolution of resistant variants which is a public health concern due to possible healthcare-associated infection spread to the general population. Hence, this study aims to evaluate antibiograms of patients with BSI and risk factors associated with septicemia.

METHODS

A total of 1166 febrile neutropenia episodes (FNE) among 513 patients with HM from the National Center for Cancer Care and Research (NCCCR), Qatar, during 2009-2019 were used for this study. The socio-demographic, clinical, microbial, and anti-microbial data retrieved from the patient's health records were used.

RESULTS

We analyzed the sensitivity of gram-negative and gram-positive bacilli reported in HM-FN-BSI patients. Out of the total 512 microorganisms isolated, 416 (81%) were gram-negative bacteria (GNB), 76 (15%) were gram-positive bacteria (GPB) and 20 (4%) were fungi. Furthermore, in 416 GNB, 298 (71.6%) were Enterobacteriaceae sp. among which 121 (41%) were ESBL (Extended Spectrum Beta-Lactamase) resistant to Cephalosporine third generation and Piperacillin-Tazobactam, 54 (18%) were Carbapenem-resistant or multidrug-resistant organism (MDRO). It's noteworthy that the predominant infectious agents in our hospital include E. coli, Klebsiella species, and P. aeruginosa. Throughout the study period, the mortality rate due to BSI was 23%. Risk factors that show a significant correlation with death are age, disease status, mono or polymicrobial BSI and septic shock.

CONCLUSION

Decision pertaining to the usage of antimicrobials for HM-FN-BSI patients is a critical task that relies on the latest pattern of prevalence, treatment resistance, and clinical outcomes. Analysis of the antibiogram of HM-FN-BSI patients in Qatar calls for a reconsideration of currently followed empirical antibiotic therapy towards better infection control and antimicrobial stewardship.

A retrospective study of Aeromonas hydrophila infections at a university tertiary hospital in Saudi Arabia

BACKGROUND

Aeromonas hydrophila can cause a wide range of diseases and is mainly found in patients with underlying diseases. Globally the data on Aeromonas infections is limited, and no studies have been published about the situation in Saudi Arabia. The aim of this study was to investigate the risk factors, clinical presentation, treatment, and outcomes of Aeromonas infections in Saudi Arabia.

METHODS

A retrospective study was performed at a tertiary university hospital with 1000 beds in Jeddah, Saudi Arabia. All patients 14 years and older with Aeromonas-positive cultures between January 1, 2015, and December 31, 2022 were included. Patient information was extracted from the electronic health records, including patient demographics, comorbidities, presenting symptoms, source of infection, human immunodeficiency virus status, culture results and antimicrobial susceptibility, use of immunosuppressive medication, and 30-day mortality.

RESULTS

In total 24 patients were identified with Aeromonas hydrophila-positive cultures, 22 of which were males (91.7%), and most (75%) had hospital-acquired infections. The 30-day mortality was 20.8%. All Aeromonas cultures were susceptible to gentamicin, cefepime, and ciprofloxacin, while the majority were resistant to ceftazidime (83.3%) and meropenem (62.5%). The most common disease presentation was skin and soft tissue infection (33.3%), the most common clinical sign was fever (58.3%), and the most common symptom was abdominal pain (37.5%). Comorbidities were very common (median 3, range 1-7). Pitt bacteremia score (p < 0.001), Charlson weighted comorbidity index (p < 0.02), international normalized ratio (p < 0.005), and the number of comorbidity factors (p < 0.05) were all associated with 30-day mortality due to Aeromonas infection. The number of comorbidities had the best predictive value (83.3%) of 30-day mortality (p < 0.05, Odds ratio 3.253, 95% confidence interval: 1.088-9.729).

CONCLUSIONS

Aeromonas hydrophila is an important pathogen to consider in nosocomial infections. The number of comorbidities had the best predictive value of 30-day mortality. The susceptibility pattern of this organism indicates that, in Saudi Arabia, when an Aeromonas infection is suspected, treatment with quinolone along with other broad-spectrum antibiotics should be started until the culture and susceptibility results are known.

Accurate Identification and Virulence Detection of Aeromonas: a Single-Center Retrospective Study on the Clinical Features and Outcomes Associated with Aeromonas Bacteremia in Southwestern China

In this study, Aeromonas spp. were re-identified, and the clinical aspects associated with Aeromonas bacteremia, as well as drug resistance and virulence genes, were elucidated. A total of 188 isolates were classified into 7 Aeromonas spp. using housekeeping gene sequencing, which was the standard to assess the accuracy of the VITEK MALDI-TOF system and the VITEK2 Compact system. The VITEK MS system and housekeeping gene sequencing had a 39.89% clear coincidence rate, whereas the VITEK2 Compact system and the standard had a 2.13% coincidence rate. Aeromonas bacteremia was associated with septic shock, hematologic malignancy, and post-hepatitic cirrhosis. Hematological malignancy, hypoproteinemia, systemic steroid use, central venous catheterization, and virulence genes act and ast were linked to poor outcomes. Aeromonas bacteremia had a 37.5% mortality rate; however, differences in mortality rates among Aeromonas spp. were observed. According to the broth microdilution method, over 90% of isolates were sensitive to most antimicrobials, except ceftriaxone (83.33%) and imipenem (83.33%). Polymerase chain reaction and DNA sequencing verified the presence of drug resistance genes; bla_CphA was detected in 3 isolates, while bla_NDM-1 was found in one isolate. In summary, common methods for identifying Aeromonas spp. are ineffective. Immunocompromised patients have a higher risk of infection and mortality. Furthermore, carbapenem resistance is a serious problem.

Clonal Dissemination of Aeromonas hydrophila With Binary Carriage of blaKPC-2-Bearing Plasmids in a Chinese Hospital

Dissemination of the Klebsiella pneumoniae carbapenemase (KPC)-encoding gene among Enterobacterales is common but relatively rare in Aeromonas spp. In this study, we characterized two KPC-2-producing Aeromonas hydrophila strains (Ah2101 and Ah2111), each isolated from a patient in different intensive care units (ICUs) of a Chinese hospital. Whole-genome sequencing (WGS) revealed simultaneous carriage of the bla_KPC−2 and imiH genes, both of which encode high-level carbapenem resistance in these two A. hydrophila isolates. The two isolates were shown to be clonally related and each isolate harbored two distinguishable bla_KPC−2-bearing plasmids, only one of which was transferrable to A. hydrophila, but not Escherichia coli EC600 via conjugation. The genetic element that contains bla_KPC−2 in these two plasmids, namely ISKpn27-Δbla_TEM−1-bla_KPC−2-ISKpn6, was structurally identical, commonly detected in Enterobacterales, and associated with Tn3-based transposons. In addition, more than sixty putative genes that encode various virulence factors were identified in these two A. hydrophila isolates. This is the first study that reports clonal dissemination of carbapenem-resistant A. hydrophila strains carrying structurally different bla_KPC−2-bearing plasmids. Further investigation is warranted to monitor the future transmission of bla_KPC−2-bearing plasmids in A. hydrophila in clinical settings.

Aeromonas and Human Health Disorders: Clinical Approaches

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Infections caused by Aeromonas species in hospitalized patients: A case series

The Aeromonads are ubiquitous Gram-negative bacilli that cause community acquired, and healthcare associated infections. In this retrospective study we analysed clinical and microbiological characteristics of thirty-six culture proven Aeromonas infections. The most common species isolated was A.hydrophila. Clinical presentation included syndromes like skin and soft tissue infections (SSTI), urinary tract infections, and central line associated bloodstream infections (CLABSI). Most of the isolates were sensitive to aminoglycosides [97.2%], followed by 3 rd generation cephalosporins, quinolones and carbapenems. Overall mortality was 13.88% (5 out of 36 patients). A high index of suspicion is required for diagnosis and better outcomes.

Application of Modified Carbapenem Inactivation Method and Its Derivative Tests for the Detection of Carbapenemase-Producing Aeromonas

PURPOSE

Infection and transmission of carbapenem-resistant Aeromonas is a serious threat to public health. Rapid and accurate detection carbapenem-resistant of these organisms is essential for reasonable treatment and infection control. This study aimed to find a simple and effective method to detect carbapenem-resistant phenotype in Aeromonas.

METHODS

A total of 131 clinical preserved Aeromonas strains were used in this study. The carbapenemase genes were detected by PCR. Modified carbapenem inactivation method (mCIM) in conjunction with EDTA-modified carbapenem inactivation method (eCIM) and simplified carbapenem inactivation method (sCIM) were performed to detect carbapenemases. We also designed a simple method, carbapenem inactivation method using supernatant (CIM-s), to detect the carbapenemase activity in the medium.

RESULTS

Of the 131 Aeromonas strains, 79 contained carbapenemase genes, including 68 blaCphA , 6 blaKPC-2 , 2 blaNDM-1 and 3 blaKPC-2+CphA . However, routine antibiotic susceptibility testing could not completely identify carbapenemase-producing Aeromonas. In phenotypic assays, the sensitivity and specificity of mCIM were 100%. The combined mCIM and eCIM could distinguish serine carbapenemase and metallo-β-carbapenemases except co-producing organisms. The sensitivity and specificity of sCIM were 92.4% and 100%, respectively, which could not detect CphA totally. CIM-s results indicate that these carbapenemases could secrete into the medium to perform their hydrolytic activities and had a sensitivity and specificity of 97.5% and 100%, respectively.

CONCLUSION

The combination of mCIM and eCIM can effectively detect and distinguish different types of carbapenemase in Aeromonas, and could be used as an important supplement approach to the antibiotic susceptibility testing.

Comparison of the Multiple Platforms to Identify Various Aeromonas Species

We compared several identification methods for Aeromonas genus members, including traditional biochemical testing, multiplex-PCR amplification, mass spectrometry identification, whole-genome sequencing, multilocus phylogenetic analysis (MLPA), and rpoD, gyrA, and rpoD-gyrA gene sequencing. Isolates (n = 62) belonging to the Aeromonas genus, which were came from the bacterial bank in the laboratory, were used to assess the identification accuracy of the different methods. Whole-genome sequencing showed that the Aeromonas spp. isolates comprised A. caviae (n = 21), A. veronii (n = 18), A. dhakensis (n = 8), A. hydrophila (n = 7), A. jandaei (n = 5), A. enteropelogenes (n = 2), and A. media (n = 1). Using the whole-genome sequencing results as the standard, the consistency of the other methods was compared with them. The results were 46.77% (29/62) for biochemical identification, 83.87% (52/62) for mass spectrometric identification, 67.74% (42/62) for multiplex-PCR, 100% (62/62) for MLPA typing, 72.58% for gyrA, and 59.68% for rpoD and gyrA-rpoD. MLPA was the most consistent, followed by mass spectrometry. Therefore, in the public health laboratory, both MLPA and whole-genome sequencing methods can be used to identify various Aeromonas species. However, rapid and relatively accurate mass spectrometry is recommended for clinical lab.

First genome sequence of Aeromonas hydrophilia novel sequence type 658 strain isolated from livestock in South Africa

OBJECTIVES

The underlying resistance mechanisms, defence systems, mobilome, virulome, clonality and global phylogenetic relationship of a novel sequence type (ST) 658 Aeromonas hydrophilia (A34a) isolated from a pig abattoir in South Africa was determined using whole-genome sequence (WGS) technology.

METHODS

Following isolation on chromogenic agar (CHROMID® CARBA SMART), microbial identification and antibiotic susceptibility testing were performed using a VITEK®2 platform. Genotyping involved WGS performed with an Illumina MiSeq platform.

RESULTS

The antibiotic resistome agreed with the resistance phenotype of the isolate and included antibiotic resistance determinants for β-lactams (bla_CPHA3 and bla_OXA-724). BLASTn analysis of resistome-encoding contigs affirmed chromosomally-mediated resistance. BURST algorithmic analysis identified the novel ST658 as a satellite variant. Virulome analysis predicted virulence genes of Aeromonas whose expression are critical for establishing infection in the host. Global phylogenomic analyses showed strain A34a is closely related to two international isolates from Sri Lanka (Ae25) and the USA (RU34A), although there is little to suggest that it was imported from abroad.

CONCLUSION

This is the first report on the genomic analysis of a novel ST658 A. hydrophilia, offering useful insights into its pathogenicity and global phylogenetics.

Distinct Antimicrobial Resistance Profiling Of Clinically Important Aeromonas Spp. In Southwest China: A Seven-Year Surveillance Study

Background

Co-evolution of host and aeromonads has diversified their spectrums of diseases and antibiograms, while a paucity of data was concerning about this diversity in China. To fill this gap, this study was aimed to investigate and compare antimicrobial resistance (AMR) patterns of clinically important Aeromonas spp. from various clinical sources.

Methods

A multicenter retrospective surveillance study was conducted in Chongqing from 2011 to 2017. Data of strains were retrieved from the database of China Antimicrobial Resistance Surveillance System (CARSS). Whonet 5.6 and Graphpad Prism 6 Software were adopted to determine and compare distribution and AMR patterns.

Results

Among 1135 Aeromonas strains, Aeromonas hydrophila complex (65.6%, 745/1135) was the most predominant species, followed by Aeromonas veronii complex (16.7%, 190/1135) and Aeromonas caviae complex (15.3%, 174/1135). Sputum was the most frequent source of strains (27.7%), followed by wound (20.8%), bloodstream (10.8%) and urine (8.8%). Urinary strains demonstrated the highest resistance rates to ceftriaxone (65.6%), ceftazidime (52.1%), cefepime (38.3%), ciprofloxacin (47.7%) and trimethoprim-sulfamethoxazole (56.6%). Similar AMR pattern was observed in intestinal strains, with corresponding resistance rates of 29.4%, 28.9%, 22.2%, 27.3% and 45%, respectively. However, respiratory, bloodstream and skin strains exhibited resistance rates of less than 20% to most of the antimicrobials tested. In terms of species, approximately 30% of Aeromonas hydrophila complex and Aeromonas caviae complex strains were resistant to ceftriaxone and trimethoprim-sulfamethoxazole, while Aeromonas veronii complex strains harbored resistance rates of less than 20% to all tested antimicrobials. Although antibiograms of these species were distinct, they remained constant from 2011 to 2017.

Conclusions

Distinct AMR patterns between species and sources highlighted the predominance of Aeromonas hydrophila complex and high resistance of strains in urine and intestine to extended-spectrum cephalosporins, ciprofloxacin and trimethoprim-sulfamethoxazole in Southwest China. Temporally constant AMR patterns should not relax the vigilance of antimicrobial resistance in clinically important Aeromonas species.