Clinical features and therapeutic implications of 104 episodes of monomicrobial Aeromonas bacteraemia

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.

A rare case of Aeromonas hydrophila catheter related sepsis in a patient with chronic kidney disease receiving steroids and dialysis: a case report and review of Aeromonas infections in chronic kidney disease patients

Aeromonas hydrophila (AH) is an aquatic bacterium. We present a case of fifty-five-year-old gentleman with chronic kidney disease (CKD) due to crescentic IgA nephropathy who presented to us with fever. He was recently pulsed with methyl prednisolone followed by oral prednisolone and discharged on maintenance dialysis through a double lumen dialysis catheter. Blood culture from peripheral vein and double lumen dialysis catheter grew AH. We speculate low immunity due to steroids and uremia along with touch contamination of dialysis catheter by the patient or dialysis nurse could have led to this rare infection. Dialysis catheter related infection by AH is rare. We present our case here and take the opportunity to give a brief review of AH infections in CKD patients.

Pneumonia caused by Aeromonas species in Taiwan, 2004-2011

We investigated the clinical characteristics of patients with pneumonia caused by Aeromonas species. Patients with pneumonia caused by Aeromonas species during the period 2004 to 2011 were identified from a computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed. Of the 84 patients with pneumonia due to Aeromonas species, possible Aeromonas pneumonia was diagnosed in 58 patients, probable Aeromonas pneumonia was diagnosed in 18 patients, and pneumonia due to Aeromonas was conclusively diagnosed in 8 patients. Most of the cases of Aeromonas pneumonia developed in men and in patients of advanced age. A. hydrophila (n = 50, 59.5 %) was the most common pathogen, followed by A. caviae (n = 24, 28.6 %), A. veronii biovar sobria (n = 7, 8.3 %), and A. veronii biovar veronii (n = 3, 3.6 %). Cancer (n = 37, 44.0 %) was the most common underlying disease, followed by diabetes mellitus (n = 27, 32.1 %). Drowning-associated pneumonia developed in 6 (7.1 %) patients. Of 47 patients who were admitted to the intensive care ward, 42 patients developed acute respiratory failure and 24 of those patients died. The overall in-hospital mortality rate was significantly associated with liver cirrhosis, cancer, initial presentation of shock, and usage of mechanical ventilation. In conclusion, Aeromonas species should be considered as one of the causative pathogens of severe pneumonia, especially in immunocompromised patients, and should be recognized as a cause of drowning-associated pneumonia. Cirrhosis, cancer, and shock as the initial presenting symptom are associated with poor outcome.

Skin and soft-tissue infections caused by Aeromonas species

This study investigated the clinical characteristics of patients with skin and soft-tissue infections (SSTIs) due to Aeromonas species. Patients with SSTIs caused by Aeromonas species during the period from January 2009 to December 2011 were identified from a computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed. A total of 129 patients with SSTIs due to Aeromonas species were identified. A. hydrophila (n = 77, 59.7 %) was the most common pathogen, followed by A. veronii biovar sobria (n = 22, 17.1 %), A. veronii biovar veronii (n = 20, 15.5 %), A. caviae (n = 9, 7.0 %), and A. schubertii (n = 1, 0.8 %). The most common isolates obtained from patients with polymicrobial infections were Klebsiella species (n = 33), followed by Enterococcus spp. (n = 24), Enterobacter spp. (n = 21), Escherichia coli (n = 17), Staphylococcus spp. (n = 17), Streptococcus spp. (n = 17), and Acinetobacter spp. (n = 15). Liver cirrhosis and concomitant bacteremia were more common among patients with monomicrobial Aeromonas SSTIs than among patients with polymicrobial SSTIs. Nine (7 %) patients required limb amputations. The in-hospital mortality rate was 1.6 %. In conclusion, Aeromonas species should be considered as important causative pathogens of SSTIs, and most infections are polymicrobial. In addition, the clinical presentation differs markedly between patients with monomicrobial and those with polymicrobial Aeromonas SSTIs.

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

The aim of the investigation was to describe the incidence of Aeromonas bacteremia in a city with a population of about 1.87 million inhabitants, located in southern Taiwan, between 2008 and 2010. Such data were compared with the incidences of Vibrio and Salmonella bacteremia in the same period and the incidence of Aeromonas bacteremia in other countries in the literature. The data revealed the average annual incidences of bacteremia due to Aeromonas, Vibrio, and Salmonella species were 76, 38, and 103 cases/million inhabitants, respectively. The incidence of Aeromonas bacteremia was higher than those in Western countries.

Aeromonas aquariorum septicemia and enterocolitis in a cirrhotic patient

Aeromonas aquariorum is a recently described Aeromonas species. We present a cirrhotic patient with septicemia and bloody diarrhea in whom A. aquariorum was isolated from the blood and stool. The species identification was based on sequence analysis of the partial rpoB and rpoD genes. The A. aquariorum isolates carried genes encoding hemolysin, aerolysin, and the cytotonic enterotoxin Alt. Significant A. aquariorum-induced cytotoxicity in intestinal epithelial cells was also demonstrated.

Empyema caused by Aeromonas species in Taiwan

Strains of Aeromonas species are prevalent bacteria in coastal areas of southern Taiwan. Aeromonad is known as a cause of epidemic diarrheal disease, and the most common clinical manifestation is acute gastroenteritis. Extra-intestinal infections by Aeromonas species, such as pleural cavity, are rare. Herein, we described the six patients who developed Aeromonas spp.-related empyema, and was successfully treated with antimicrobial agent and drainage.

Biliary tract infections caused by Aeromonas species

This study investigated the clinical and microbiological characteristics of patients with Aeromonas infections of the biliary tract. Patients with bile cultures positive for Aeromonas species during the period July 2004 to December 2011 were identified from a computerized database of a hospital in Taiwan. Patients with Aeromonas infections of the biliary tract were further identified. During the study period, a total of 1,142 isolates of Aeromonas species were obtained from 750 patients. Of those patients, 91 (12.1 %) had Aeromonas infections of the biliary tract. The annual incidence (episodes per 10,000 patient-days) of biliary tract infections caused by all Aeromonas species was 0.31 in 2007, 0.12 in 2010, and 0.27 in 2011. A. hydrophila was the most common species isolated (n = 41, 45.1 %), followed by A. caviae (n = 30, 33.0 %), A. veronii biovar sobria (n = 15, 16.5 %), and A. veronii biovar veronii (n = 5, 5.5 %). The majority of patients (n = 77, 84.6 %) had polymicrobial infections. Hepatobiliary stones (n = 50, 54.9 %) and hepatobiliary cancer (n = 38, 41.8 %) were the most common underlying diseases, followed by diabetes mellitus (n = 29, 31.9 %) and liver cirrhosis (n = 7, 7.7 %). The in-hospital mortality rate was 8.8 %. Infection-related mortality was associated with underlying immunocompromised condition (p = 0.044) and use of mechanical ventilation (p = 0.004), but was not associated with inappropriate antibiotic usage or concomitant bacteremia (n = 8, 8.8 %). In conclusion, biliary tract infections caused by Aeromonas species are not uncommon and can develop in both immunocompromised and immunocompetent patients; however, patients with underlying hepatobiliary diseases are particularly susceptible to these infections.

Antibiotic therapy for inducible AmpC β-lactamase-producing Gram-negative bacilli: what are the alternatives to carbapenems, quinolones and aminoglycosides?

Some bacteria that possess chromosomally determined AmpC β-lactamases may express these enzymes at a high level following exposure to β-lactams, either by induction or selection for derepressed mutants. This may lead to clinical failure even if an isolate initially tests susceptible in vitro, a phenomenon best characterised by third-generation cephalosporin therapy for Enterobacter bacteraemia or meningitis. Several other Enterobacteriaceae, such as Serratia marcescens, Citrobacter freundii, Providencia spp. and Morganella morganii (often termed the 'ESCPM' group), may also express high levels of AmpC. However, the risk of clinical failure with β-lactams that test susceptible in vitro is less clear in these species than for Enterobacter. Laboratories frequently do not report β-lactam or β-lactamase inhibitor combination drug susceptibilities for ESCPM organisms, encouraging alternative therapy with quinolones, aminoglycosides or carbapenems. However, quinolones and carbapenems present problems with selective pressure for multiresistant organisms, and aminoglycosides with potential toxicity. The risk of emergent AmpC-mediated resistance for non-Enterobacter spp. appears rare in clinical studies. Piperacillin/tazobactam may remain effective and may be less selective for AmpC derepressed mutants than cephalosporins. The potential roles for agents such as cefepime or trimethoprim/sulfamethoxazole are also discussed. Clinical studies that better define optimal treatment for this group of bacteria are required.

Bacterial infections other than spontaneous bacterial peritonitis in cirrhosis

Cirrhotic patients are immunocompromised with a high risk of infection. Proinflammatory cytokines and hemodynamic circulation derangement further facilitate the development of serious consequences of infections. Other than spontaneous bacterial peritonitis, bacteremia and bacterial infections of other organ systems are frequently observed. Gram-negative enteric bacteria are the most common causative organism. Other bacterial infections, such as enterococci, Vibrio spp., Aeromonas spp., Clostridium spp., Listeria monocytogenes, Plesiomonas shigelloides and Mycobacterium tuberculosis are more prevalent and more virulent. Generally, intravenous third generation cephalosporins are recommended as empirical antibiotic therapy. Increased incidences of gram-positive and drug-resistant organisms have been reported, particularly in hospital-acquired infections and in patients receiving quinolones prophylaxis. This review focuses upon epidemiology, microbiology, clinical features and treatment of infections in cirrhosis other than spontaneous bacterial peritonitis, including pathogen-specific and liver disease-specific issues.

Fatal septicemia and endotoxic shock due to Aeromonas hydrophila

Background:

Although rare, bloodstream infections caused by Aeromonas tend to be very severe and progress rapidly.

Case Report:

We report a case of an 81-year-old man with fetal septicemia and endotoxin shock caused by Aeromonas hydrophila. The patient had dilated cardiomyopathy, paroxysmal atrial fibrillation, interstitial pneumonitis and renal dysfunction was admitted to our hospital with chest pain and dyspnea. Transthoracic echocardiography demonstrated impaired left ventricular wall motion and severe mitral regurgitation due to tethering. Cardiac catheterization revealed severe stenotic lesions in the left anterior descending artery and the right coronary artery. Surgery for coronary artery bypass grafts and mitral annuloplasty were performed. However, 2 days after surgery, he suddenly developed a high-grade fever and his hemodynamics deteriorated rapidly. His blood cultures revealed gram-negative Bacillus and the endotoxin concentration in the blood was elevated. Despite intensive support efforts, the patient died 1 day after the sudden change. His blood culture revealed A. hydrophila.

Conclusions:

Whenever Aeromonas is found in a patient’s bloodstream, clinicians should start appropriate and intensive treatment immediately.

Fulminant Aeromonas hydrophila infection during acute lymphoblastic leukemia treatment

Aeromonas hydrophila septicemia has a fulminant course and it has been usually reported in immunocompromised hosts and rarely among children with leukemia. High morbidity and mortality is associated with A hydrophila infections. We describe the case of a child with acute lymphoblastic leukemia who presented with septicemia due to A hydrophila. The patient presented with fever and skin discoloration during a febrile neutropenia episode, which rapidly evolved into bacteremia and extensive thigh suppuration, fasciitis, and myonecrosis. Apart from antibiotic treatment, surgical debridement to relieve compartment pressure and prevent further lower extremity compromise was promptly performed. Despite long delays in chemotherapy and an extensive tissue gap, primary closure of the involved area was possible with full cosmetic and functional limb recovery, and the patient has remained in clinical remission for more than 7 years.

Fulminant necrotizing fasciitis caused by Aeromonas sobria in neutropenic patients

Infection with Aeromonas species has been reported to occur in neutropenic patients. Necrotizing fasciitis caused by Aeromonas species is uncommon but potentially life-threatening. We herein describe three cases of fulminant necrotizing fasciitis caused by Aeromonas sobria in neutropenic patients. These cases shared many clinical characteristics, including shock, coagulopathy, multiple organ failure and rapidly deteriorating and eventually fatal clinical courses. In all cases, Aeromonas sobria was resistant to most antibiotics, except quinolones. Our experience suggests that necrotizing fasciitis caused by Aeromonas sobria is a distinctive and fatal entity. As the use of quinolones is not usually considered in cases of febrile neutropenia, it is important to adjust the antibiotics in time when culture results become available. In some cases, early treatment with quinolones and surgical intervention should be considered, especially when this complication occurs in patients with profound neutropenia.

Different clinical characteristics among Aeromonas hydrophila, Aeromonas veronii biovar sobria and Aeromonas caviae monomicrobial bacteremia

This study aimed to compare the clinical presentations of Aeromonas hydrophila, A. veronii biovar sobria and A. caviae monomicrobial bacteremia by a retrospective method at three hospitals in Taiwan during an 8-yr period. There were 87 patients with A. hydrophila bacteremia, 45 with A. veronii biovar sobria bacteremia and 22 with A. caviae bacteremia. Compared with A. hydrophila and A. veronii biovar sobria bacteremia, A. caviae bacteremia was more healthcare-associated (45 vs 30 and 16%; P = 0.031). The patients with A. caviae bacteremias were less likely to have liver cirrhosis (27 vs 62 and 64%; P = 0.007) and severe complications such as shock (9 vs 40 and 47%; P = 0.009) and thrombocytopenia (45 vs 67 and 87%; P = 0.002). The APACHE II score was the most important risk factor of Aeromonas bacteremia-associated mortalities. The APACHE II scores of A. caviae bacteremias were lower than A. hydrophila bacteremia and A. veronii biovar sobria bacteremia (7 vs 14 and 16 points; P = 0.002). In conclusion, the clinical presentation of A. caviae bacteremia was much different from A. hydrophila and A. veronii biovar sobria bacteremia. The severity and mortality of A. caviae bacteremia were lower than A. hydrophila or A. veronii biovar sobria bacteremia.

Aeromonas spp. clinical microbiology and disease

Members of the genus Aeromonas inhabit various aquatic environments and are responsible for, and are implicated in, a number of intestinal and extra-intestinal infections in humans as well as other animals. This review focuses on invasive human infection and disease and summarizes available findings regarding the microbiology and detection of Aeromonas spp., with emphasis on successful identification and diagnosis, and the control of disease in the population. Antimicrobial resistance and therapy of Aeromonas spp. is also discussed.

Bacteremia caused by Aeromonas species [corrected] complex in the Caribbean Islands of Martinique and Guadeloupe

Aeromonas species are Gram-negative bacilli of the water environment whose survival appears facilitated by warm climates. There have been no reports on Aeromonas species in the [corrected] Caribbean to date. Our aim was to describe clinical and bacteriological features in patients presenting with such bacteremia in Martinique and Guadeloupe. During a 14-year period, we retrospectively identified 37 patients. The mean age was 55 years and in 89% of cases underlying disease such as digestive diseases, cutaneous wounds, and malignancy were identified. One case was related to severe strongyloidiasis and one with snake bite. Polymicrobial bacteremia was identified in 38%, essentially with Enterobacteriaceae. All Aeromonas isolates were resistant to amoxicillin but extended-spectrum beta-lactam and fluoroquinolone were active against more than 95%. During hospitalization 10 patients died (27%). Older age, occurrence of multiorgan failure, and impaired renal function were associated with in-hospital mortality.

Necrotizing soft tissue infections in the intensive care unit

Necrotizing soft tissue infection is a severe illness that is associated with significant morbidity and mortality. It is often caused by a wide spectrum of pathogens and is most frequently polymicrobial. Care for patients with necrotizing soft tissue infection requires a team approach with expertise from critical care, surgery, reconstructive surgery, and rehabilitation specialists. The early diagnosis of necrotizing soft tissue infection is challenging, but the keys to successful management of patients with necrotizing soft tissue infection are early recognition and complete surgical debridement. Early initiation of appropriate broad-spectrum antibiotic therapy must take into consideration the potential pathogens. Critical care management components such as the initial fluid resuscitation, end-organ support, pain management, nutrition support, and wound care are all important aspects of the care of patients with necrotizing soft tissue infection. Soft tissue reconstruction should take into account both functional and cosmetic outcome.

A survival benefit of combination antibiotic therapy for serious infections associated with sepsis and septic shock is contingent only on the risk of death: a meta-analytic/meta-regression study

OBJECTIVE

To assess whether a potential benefit with combination antibiotic therapy is restricted to the most critically ill subset of patients, particularly those with septic shock.

DATA SOURCES

OVID MEDLINE (1950-October 2009), EMBASE (1980-October 2009), the Cochrane Central Register of Controlled Trials (to third quarter 2009), the ClinicalTrial.gov database, and the SCOPUS database.

STUDY SELECTION

Randomized or observational studies of antimicrobial therapy of serious bacterial infections potentially associated with sepsis or septic shock. Fifty studies met entry criteria.

DATA EXTRACTION

Study design, mortality/clinical response, and other variables were extracted independently by two reviewers. When possible, study datasets were split into mutually exclusive groups with and without shock or critical illness.

DATA SYNTHESIS

Although a pooled odds ratio indicated no overall mortality/clinical response benefit with combination therapy (odds ratio, 0.856; 95% confidence interval, 0.71-1.03; p = .0943; I = 45.1%), stratification of datasets by monotherapy mortality risk demonstrated substantial benefit in the most severely ill subset (monotherapy risk of death >25%; odds ratio of death, 0.51; 95% confidence interval, 0.41-0.64; I = 8.6%). Of those datasets that could be stratified by the presence of shock/critical illness, the more severely ill group consistently demonstrated increased efficacy of a combination therapy strategy (odds ratio, 0.49; 95% confidence interval, 0.35-0.70; p < .0001; I = 0%). An increased risk of death was found in low-risk patients (risk of death <or=15% in the monotherapy arm) exposed to combination therapy (odds ratio, 1.53; 95% confidence interval, 1.16-2.03; p = .003; I = 8.2%). Meta-regression indicated that efficacy of combination therapy was dependent only on the risk of death in the monotherapy group.

CONCLUSION

Combination antibiotic therapy improves survival and clinical response of high-risk, life-threatening infections, particularly those associated with septic shock but may be detrimental to low-risk patients.

Aeromonas and Pseudomonas: antibiotic and heavy metal resistance species from Iskenderun Bay, Turkey (northeast Mediterranean Sea)

We studied the susceptibility patterns to 15 different antibiotics and six heavy metals in Aeromonas spp. and Pseudomonas spp. isolated from Iskenderun Bay, Turkey (northeast Mediterranean Sea). A high percentage of Aeromonas isolates showed resistance to cefazolin (66.6%) and trimethoprim-sulphamethoxazole (66.6%). Amongst the Pseudomonas isolates, there was a high incidence of resistance to nitrofurantoin (86.2%), cefazolin (84.8%) and cefuroxime (71.7%). Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from 25 to >3,200 microg/ml. The Aeromonas spp. and Pseudomonas spp. showed high resistance to copper of 98.3% and 75.4%, respectively, and low resistance to lead of 1.7% and 7.2%, respectively. Our results show that antibiotic and heavy metal resistant Aeromonas spp. and Pseudomonas spp. were widespread in Iskenderun Bay in 2007 and 2008. The increasing presence of antibiotic and heavy metal resistant Aeromonas spp. and Pseudomonas spp. may become a potential human health hazard.

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.

Different clinical characteristics between polymicrobial and monomicrobial Aeromonas bacteremia--a study of 216 cases

BACKGROUND

Part of Aeromonas bacteremia is polymicrobial infection. However, a clinical comparison of monomicrobial and polymicrobial Aeromonas bacteremia has not hitherto been reported.

METHODS

A retrospective analysis of medical records of patients with Aeromonas bacteremia at three large referral hospitals in Taiwan for an 8-year period (2001-2008) was conducted.

RESULTS

There were 154 patients with monomicrobial Aeromonas bacteremia and 62 patients with polymicrobial Aeromonas bacteremia. In the polymicrobial infections, E. coli was the most common combined pathogen (42%), followed by Klebsiella spp. (24%) and Enterobacter spp. (16%). Multivariate logistic regression analysis revealed solid cancer as the risk factor for polymicrobial Aeromonas bacteremia, with male gender and cirrhosis as risk factors for monomicrobial Aeromonas bacteremia. However, of all types of solid cancer, hepatoma was associated with monomicrobial Aeromonas bacteremia. APACHE II score was the most important prognostic factor in both groups.

CONCLUSION

Aeromonas bacteremia in patients with cirrhosis or male gender tended to be monomicrobial. Polymicrobial Aeromonas bacteremia was associated with solid cancers. In either polymicrobial or monomicrobial Aeromonas bacteremia, prognosis could be predicted according to disease severity measured by APACHE II score.

Aeromonas spontaneous bacterial peritonitis: a highly fatal infectious disease in patients with advanced liver cirrhosis

BACKGROUND/PURPOSE

Aeromonas infections, rarely reported in Western countries, are not uncommon infectious diseases in Taiwan. The clinical manifestations and prognostic factors of Aeromonas spontaneous bacterial peritonitis (SBP) in patients with liver cirrhosis were investigated.

METHODS

We reviewed the medical charts and microbiological records of liver cirrhosis patients with Aeromonas SBP between January 1990 and December 2005, in a medical center in southern Taiwan.

RESULTS

Thirty-one liver cirrhosis patients developed Aeromonas SBP within a 16-year period. The majority (26, 84%) had concurrent Aeromonas bacteremia. A. sobria (55%) and A. hydrophila (45%) were the causative species. The predominant clinical manifestations included fever (84%), abdominal pain (74%), hypotension on admission (48%), altered mental status (45%), and acute renal failure (42%). Gram-negative bacilli were found in Gram staining of ascitic fluids in 27% of 26 patients, while aeromonads were isolated from ascitic fluids in 55% of 31 patients. The yield rate of ascitic fluid cultures decreased greatly, if paracentesis was performed at > 3 hours after the administration of antimicrobial therapy. All but one patient received in-vitro-active antimicrobial agents within 48 hours, but the all-cause mortality rate was 56%. Initial high Pitt's bacteremia score was independently associated with a fatal outcome in multivariate analysis.

CONCLUSION

Aeromonas SBP is a fatal disease, and must be included in the differential diagnosis of SBP in patients with advanced liver cirrhosis in endemic areas.

Burn wounds infected by contaminated water: case reports, review of the literature and recommendations for treatment

First-aid education for the management of burns advocates cool running water over burnt skin to limit soft tissue damage. However, the water used may itself constitute a risk. We report three cases of severe invasive and necrotizing infection in patients who used or immersed themselves in contaminated water in an attempt to extinguish the fire following acute major burns. Wound cultures from all patients yielded Aeromonas hydrophila and two yielded Bacillus cereus. One patient had a complex polymicrobial infection, including zygomycosis with Rhizomucor variabilis. All patients were treated aggressively with wound débridement, including one patient who required bilateral lower limb amputations to control progressive infection. All infections were successfully treated and all patients survived their burn injuries. We review the management of burns complicated by exposure to contaminated water leading to burn wound infections. We describe commonly reported organisms from various water sources, the appropriate initial empirical antimicrobial chemotherapy and present the clinician with a proposed algorithm for managing these serious infections.

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.

Prospective nationwide study of Aeromonas infections in France

We report a systematic prospective multicenter nationwide study of clinical Aeromonas infections in France. During 6 months (May to October 2006), 78 cases of aeromonosis were reviewed for risk factors and clinical, microbiological, and antimicrobial susceptibility data. They included wound infections (44%), bacteremia (26%), enteritis (19%), respiratory tract infections (6%), and miscellaneous (5%) infections.

Necrotizing fasciitis in southeast Taiwan: clinical features, microbiology, and prognosis

OBJECTIVES

To determine the spectrum of microorganisms, clinical features, and risk factors of necrotizing fasciitis in southeast Taiwan.

METHODS

We retrospectively studied patients diagnosed with necrotizing fasciitis and fully treated in our hospital for the period January 1995 to December 2006.

RESULTS

The mean age of the patients was 58.2+/-14.2 years. The affected anatomical sites were primarily peripheral (91 patients, 85.8%). Sixty patients (56.6%) had a type 1 infection, 17 patients (16.0%) had type 2, and eight patients (7.5%) had type 3. Diabetes mellitus was the most common comorbidity. A single pathogen was identified as the infectious agent in 64 patients (60.4%), multiple pathogens were identified in 21 patients (19.8%), and no organism was identified in 21 patients (19.8%). Streptococcus pyogenes was the most common pathogen. The average hospital stay was 28.0+/-23.1 days. Patients received a mean of 2.3+/-1.2 debridements, and five patients (4.7%) eventually underwent an amputation. The overall mortality was 17.0%. Predictors of mortality included advanced age, class C liver cirrhosis, ascites, higher serum creatinine, and lower hemoglobin and platelet levels.

CONCLUSIONS

Monobacterial infections are more common in our patients. Accurate early diagnosis and extensive surgical debridement are essential for a favorable outcome.

Clinical significance of spontaneous Aeromonas bacterial peritonitis in cirrhotic patients: a matched case-control study

BACKGROUND

Although Aeromonas species are known to cause bacteremia in patients with cirrhosis, less is known about spontaneous bacterial peritonitis (SBP) caused by Aeromonas species in these patients.

METHODS

We performed a retrospective, matched case-control study (1:2 ratio) consisting of patients presenting with SBP due to Aeromonas species from January 1997 through December 2006. Control subjects were patients with SBP caused by other organisms and were matched to the patients by age (+/- 1 year) and sex.

RESULTS

We identified 43 patients with SBP due to Aeromonas species, 40 (93%) of whom had Aeromonas hydrophila infection and 3 (7%) of whom had Aeromonas sorbia infection. There were 81 control subjects, of whom 38 (47%) were infected with Escherichia coli, 25 (31%) were infected with Klebsiella species, 12 (15%) were infected with Streptococcus species, and 6 (7%) were infected with other bacteria. Baseline Child-Pugh class and model for end-stage liver disease score did not differ between groups. A significant increase in the incidence of infection during the warm season (July-September) was observed in the group with SBP due to Aeromonas species, compared with the group with SBP due to other bacteria (63% vs. 25%; P < .001). Diarrheal episodes were significantly more frequent in the group with SBP due to Aeromonas species (26% vs. 6%; P = .002). There were no statistically significant differences between groups with regard to appropriateness of initial antibiotic therapy,3-day mortality, and 30-day cumulative survival. In the group with Aeromonas infection, the in-hospital mortality rate was 23%; septic shock was the only independent prognostic factor of in-hospital mortality (odds ratio, 34.5;95% confidence interval, 1.9-640.6; P = .02).

CONCLUSION

Aeromonas species should be considered to be a causative organism of SBP in cirrhotic patients presenting with diarrheal episodes during the warm season. Compared with SBP caused by other organisms, SBP due to Aeromonas species was not associated with more-advanced cirrhosis.

Shewanella soft tissue infection: case report and literature review

OBJECTIVE

To better understand the clinical characteristics of soft tissue infections caused by Shewanella in humans.

METHODS

We report a case of Shewanella soft tissue infection and review the English literature from a search of PubMed.

RESULTS

A total of 27 adults (mean age 61.1+/-16.0 years) with soft tissue infections caused by Shewanella were included for analysis. Limb involvement was found in 22 (81.5%) patients, while scalp, face, perineum, lacrimal sac, and abdominal wall involvement were each found in one patient. Chronic ulcer over the leg (14 cases (51.9%)), steroid use (four cases (14.8%)), and liver cirrhosis (three cases (11.1%)) were the major underlying conditions. Shewanella bacteremia was found in 14 out of 22 patients with soft tissue infections involving the limbs. Two patients died of septicemia, giving a mortality rate of 7.4%.

CONCLUSIONS

Shewanella soft tissue infections usually develop in immunocompromised patients with a preexisting cutaneous ulcer (particularly over the legs) after marine environment or seawater exposure. In view of the possible catastrophic consequences, education on the prevention of Shewanella soft tissue infections in at-risk people (e.g., the immunocompromised or elderly with a cutaneous ulcer) relating the need to avoid exposure to the marine environment or seawater may be of importance.

In vitro activities of tigecycline against clinical isolates of Aeromonas, Vibrio, and Salmonella species in Taiwan

All 198 Salmonella isolates (58.6% of isolates were resistant to tetracycline), 92 Vibrio isolates (4.4% of isolates were resistant to tetracycline), and 200 of 201 Aeromonas isolates (39.3% of isolates were resistant to tetracycline; 1 A. caviae isolate had a tigecycline MIC of 4 mug/ml) in our study were susceptible to tigecycline, by U. S. Food and Drug Administration criteria for Enterobacteriaceae.

[Aeromonas spp. infections: retrospective study in Nîmes University Hospital, 1997-2004]

OBJECTIVE

Retrospective study of patients presenting Aeromonas spp. infections admitted to Nîmes hospital from January 1997 to December 2004.

PATIENTS AND METHOD

Aeromonas spp. infections were collected from the database of the bacteriology department. The Aeromonas species, suceptibility phenotype, epidemiological data, site and type (nosocomial or not) of infection, and evolution were collected from medical files.

RESULTS

Thirty infections were notified corresponding to 22 male and eight female of 50.6 years old (mean) and a mean stay duration of 31 days. Skin and soft tissues (50%), digestive tract (26.7%), bones and articulations (10%), blood stream (6.7%), urinary tract (3.3%) and lymph nodes (3.3%) were the sites of infection. Ten infections were nosocomial, four were associated with medical leeches. All strains were resistants to amoxicillin and amoxicillin- clavulanic acid, whereas resistance rate to other beta-lactams was under 10% and all were suceptible to fluoroquinolones and aminoglycosides. All patients received antibiotic treatment: 31% a single molecule, 69% an association and 62% needed a second line treatment. Strain was suceptible to the antibiotic in 78.5% of cases. Only one death occured not directly linked to Aeromonas infection.

DISCUSSION

Most of Aeromonas spp. infection sites were cutaneous and digestive. Nosocomial infections associated with medical leeches are not so uncommon and strict conditions of storage and administration are necessary. According to the susceptibility phenotype of our strains which is similar to literature data, a third generation cephalosporin or a fluoroquinolone should be used evenly associated with an aminoglycoside.

Predictive model of antimicrobial-resistant Gram-negative bacteremia at the ED

BACKGROUND

Despite numerous studies identifying the risk factors related to gram-negative antimicrobial resistance, an epidemiological model to reliably predict antimicrobial gram-negative resistance in clinics, before the bacterial culture result is available, has not yet been developed.

OBJECTIVES

The aim of this study was to develop a predictive model to assist physicians in selecting appropriate antimicrobial agents before the details of the microbiology and drug susceptibility are known.

MATERIALS AND METHODS

A prospective study was conducted between June 1, 2001, and May 31, 2002, at the emergency department (ED) of National Taiwan University Hospital. Enrollees were patients with gram-negative bacteremia (GNB) at ED. Other information collected included demographic characteristics, underlying comorbidities, hospital exposure and health care-associated factors, and details of initial presentation. Two primary outcomes were defined, including cefazolin-resistant (CZ-RES) GNB and ceftriaxone-resistant (CTX-RES) GNB. Two thirds of the data was randomly allocated to a derivation data set (for developing predictive models), and the rest, to a validation data set (for testing model validity). Simplified models, using a coefficient-based scoring method, were also developed for clinical applications.

RESULTS

Based on 695 episodes of GNB, predictors of CZ-RES GNB were time since last hospitalization (increased risk for durations <1 month), prior infection with a CTX-RES strain, post-transplantation immunosuppressant use, residence in a nursing home or history of stroke with repeated choking, and poor oxygen saturation (<95%) at admission to ED. Cirrhosis showed a protective effect by reducing the odds of antimicrobial-resistant GNB. The area under receiver operating characteristic (ROC) curve for the CZ-RES model was 0.76 (95% confidence interval, 0.71-0.81). The CTX-RES model included all the variables that were in the CZ-RES model plus abnormal leukocyte count (<1000 or >15,000 /mm3) at entry to ED. In this case, however, previous hospitalization within the last 2 weeks was a key factor. The area under this ROC curve was 0.82 (95% confidence interval, 0.76-0.88). There was lacking of difference in the area under the ROC curve between the 2 final (simplified) models either based on the derivation or validation data sets.

CONCLUSION

We have developed 2 models for predicting risk of antimicrobial gram-negative infection by identifying and quantifying associated risk factors. These models could be used by physicians to determine the most appropriate choice of antibiotic for first-line therapy, particularly in situations where the culture result is not yet known.

Aeromonas infection in critically ill burn patients

Aeromonas infection in burn patients is extremely uncommon. Here we report on four cases of Aeromonas infection in burn patients admitted to the BICU at the Singapore General Hospital burn unit between June 2001 and May 2006. Two patients had positive blood cultures, and the other two had tissue samples with growth. There was no history of exposure to soil or fresh water in all patients. The average age of patients was 35 years (range 24-41) and the average % TBSA was 48% (range 35-80). Cultures were isolated between days 2 and 4 post burn. There was one mortality in the series. Increasing antibiotic resistance was noted among isolates of Aeromonas. Continued vigilance is essential to detect infection early, even in the absence of a suggestive history, with adequate debridement and appropriate antibiotic therapy.

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.

Secondary Aeromonas peritonitis is associated with polymicrobial ascites culture and absence of liver cirrhosis compared to primary Aeromonas peritonitis

Aeromonas peritonitis remains a rare condition. In this study we describe the clinical features of primary and secondary Aeromonas peritonitis, and compare the differences between these two diseases entities. Patients with Aeromonas peritonitis were identified from microbiological and medical records during the period between March 1994 and March 2003. Clinical characteristics, laboratory data, microbiological results, treatment and outcome of patients were obtained by retrospective chart review. 22 and 27 patients with primary or secondary peritonitis caused by Aeromonas species were identified. All except two of these patients were adults, with a median age of 62.4 (31-76) vs 65.8 (8-85) years, respectively. Males were predominant (82 vs 78%). Peritonitis was community acquired in 73% and 56% of patients in these two groups, respectively. Significantly higher prevalence of underlying liver cirrhosis (96 vs 7%, p<0.001), which was Child-Pugh class C in 91% of cases, in primary peritonitis was noted. Primary peritonitis was more likely to be monomicrobial (100 vs 15%, p<0.001) and complicated by bacteremia (50 vs 7%, p=0.011). A source of intraabdominal infection should be sought when Aeromonas peritonitis occurs in a patient who has no history of liver cirrhosis or who has a polymicrobial result of ascites culture.

Prevalence and Antimicrobial Resistance Patterns of Aeromonas Strains Isolated from Drinking Water Samples in Istanbul, Turkey

The aim of this study was to determine the prevalence and the resistance patterns of Aeromonas spp. in drinking water in Istanbul, Turkey. We investigated a total of 1,680 drinking water samples (840 tap water and 840 domestic water tank samples) for Aeromonas strains between June 2002 and October 2005. A total of 147 Aeromonas strains were isolated from 49 (6%) of 840 tap water samples and from 98 (12%) of 840 domestic water tank samples. Antibiotic susceptibility of Aeromonas strains was determined by the disc diffusion method, according to the CLSI (Clinical Laboratory Standards Institute) recommendation. Among the 147 Aeromonas strains, the prevalence was: A. hydrophila 68 (46%), A. sobria 50 (34%), A. caviae 11 (8%), A. salmonicida 9 (6%), A. veronii 5 (3%) and A. jandaei 4 (3%). Approximately 55% of the strains were resistant to ampicillin, 48% to erythromycin, 41% to amoxicillin-clavulanic acid, 28% to ceftazidime, 27% to cefoxitin, 26% to ceftriaxone and cefotaxime, 22% to piperacillin, 14% to trimethoprim-sulfamethoxazole, 12% to tetracycline, 11% to aztreonam, 8% to meropenem, 6% to imipenem, 2% to nalidixic acid, 1% to ciprofloxacin, tobramycin and gentamicin. None of the strains were resistant to amikacin and netilmicin. In conclusion, Aeromonas spp. isolated from drinking water in Istanbul have a resistance potential and the antibiotic resistance rates of A. hydrophila, A. sobria and A. caviae were usually higher than those of other Aeromonas strains. It should be kept in mind that these microorganisms in drinking water might be a potential risk for public health.

Biochemical and molecular characterization of tetracycline-resistant Aeromonas veronii isolates from catfish

Eighty-one tetracycline-resistant Aeromonas sp. strains were isolated from farm-raised catfish. Morphological and biochemical characteristics indicated that 23 of the 81 aeromonads were Aeromonas hydrophila, 7 isolates were Aeromonas trota, 6 isolates were Aeromonas caviae, 42 isolates were Aeromonas veronii, and 3 isolates were Aeromonas jandaei. However, the AluI and MboI restriction fragment length polymorphism (RFLP) patterns of the PCR-amplified 1.4-kb 16S rRNA gene from all 81 tetracycline-resistant aeromonads from catfish were identical to the RFLP banding patterns of A. veronii ATCC 35626, indicating that all 81 isolates were strains of A. veronii. A multiplex PCR assay successfully amplified the 5 tetracycline-resistant genes (tetA to E) from the genomic DNA of all 81 isolates. The assay determined that tetE was the dominant gene occurring in 73/81 (90.0%) of the aeromonads. Plasmids (2.0 to 20 kb) were isolated from 33 of the 81 isolates. Dendrogram analysis of the SpeI pulsed-field gel electrophoresis identified 15 distinct macrorestriction patterns among the isolates. Our results indicate the need for use of 16S rRNA in the identification of Aeromonas spp. and the prevalence of catfish as a reservoir of tet genes.

Prevalence of environmental Aeromonas in South East Queensland, Australia: a study of their interactions with human monolayer Caco-2 cells

AIMS

To investigate the prevalence of Aeromonas in a major waterway in South East Queensland, Australia, and their interactions with a gut epithelial model using Caco-2 cells.

METHODS AND RESULTS

A total of 81 Aeromonas isolates, collected from a major waterway in South East Queensland, Australia, were typed using a metabolic fingerprinting method, and tested for their adhesion to HEp-2 and Caco-2 cells and for cytotoxin production on Vero cells and Caco-2 cells. Aeromonas hydrophila had the highest (43%) and Aeromonas veronii biovar sobria had the lowest (25%) prevalence. Four patterns of adhesion were observed on both HEp-2 and Caco-2 cell lines. Representative isolates having different phenopathotypes (nine strains) together with two clinical isolates were tested for their translocation ability and for the presence of virulence genes associated with pathogenic Escherichia coli. The rate and degree of translocation across Caco-2 monolayers varied among strains and was more pronounced with LogA pattern. Translocation was associated with the adherence of strains to Caco-2 cells microvilli, followed by internalization into Caco-2 cells. Two Aer. veronii biovar sobria strains were positive for the presence of heat-labile toxin genes, with one strain also positive for Shiga-like toxin gene.

CONCLUSIONS

Pathogenic strains of Aeromonas carrying one or more virulence characteristics are highly prevalent in the waterways studied and are capable of translocating across a human enterocyte cell model.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study indicates that Aeromonas strains carrying one or more virulence properties are prevalent in local waterways and are capable of translocating in a human enterocyte cell culture model. However, their importance in human gastrointestinal disease has yet to be verified under competitive conditions of the gut.

Aeromonas bacteremia in an elderly immunocompetent patient

We report the case of an elderly immunocompetent patient with Aeromonas hydrophila bacteremia without evidence of portal of entry. Despite several risk factors for a poor outcome, such as impaired renal function, two positive blood cultures, and community-acquired infections, the patient survived. Antimicrobial susceptibility was normal. Unknown polycystic liver disease was discovered and misdiagnosed as a hepatic abscess at the time of the bacteremia which was confirmed by repeated CT scans. Because of the absence of other risk factors for Aeromonas bacteremia, hepatic polycystic disease may take part in the onset of Aeromonas sp bacteremia as well as immunosenescence.