In vitro antimicrobial susceptibility of clinical isolates of Aeromonas caviae, Aeromonas hydrophila and Aeromonas veronii biotype sobria

The Impact of Cefuroxime Susceptibility on Aeromonas Necrotizing Fasciitis Outcomes

Despite aggressive antibiotic therapy and surgical debridement, Aeromonas necrotizing fasciitis (NF) can lead to high amputation and mortality rates. Our study compares the different antibiotic minimum inhibitory concentrations (MICs) via Epsilometer tests (E-tests) between non-survivors and survivors of Aeromonas NF of limbs. A prospective review of 16 patients with Aeromonas NF was conducted for 3.5 years in a tertiary coastal hospital. E-tests were conducted for 15 antimicrobial agents to determine the MIC value for Aeromonas species. These patients were divided into non-survival and survival groups. The clinical outcomes, demographics, comorbidities, presenting signs and symptoms, laboratory findings, and microbiological results between the two periods were compared. A total of four patients died, whereas 12 survived, resulting in a 25% mortality rate. A higher proportion of bloodstream infections (100% vs. 41.7%; p = 0.042), monomicrobial infections (100% vs. 33.3%; p = 0.021), shock (100% vs. 33.3%; p = 0.021), serous bullae (50% vs. 0%; p = 0.009), liver cirrhosis (100% vs. 25%; p = 0.009), chronic kidney disease (100% vs. 33.3%; p = 0.021), lower susceptibility to cefuroxime (25% vs. 83.3%; p = 0.028), and ineffective antibiotic prescriptions (75% vs. 16.7%; p = 0.029) was observed in non-survivors. Aeromonas NF is an extremely rare skin and soft-tissue infection that is associated with high mortality, bacteremia, antibiotic resistance, and polymicrobial infection. Therefore, antibiotic regimen selection is rendered very challenging. To improve clinical outcomes and irrational antimicrobial usage, experienced microbiologists can help physicians identify specific pathogens and test MIC.

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.

Enteric Aeromonas Infection: a Common Enteric Bacterial Infection with a Novel Infection Pattern Detected in an Australian Population with Gastroenteritis

Aeromonas species are emerging human enteric pathogens. However, they are currently not routinely detected in many diagnostic laboratories, and information regarding Aeromonas enteric infections detected using molecular methods is lacking. Here, we investigated the detection of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis processed in a large Australian diagnostic laboratory between 2015 and 2019. These enteric pathogens were detected using quantitative real-time PCR (qPCR) methods. Furthermore, we compared the qPCR cycle threshold (CT) values obtained from fecal samples that tested positive for Aeromonas only by molecular detection with those of samples that tested positive by both molecular detection and bacterial isolation methods. Aeromonas species were found to be the second most common bacterial enteric pathogens among patients with gastroenteritis. We observed a unique pattern of three infection peaks for Aeromonas, which correlated with the age of the patients. Aeromonas species were the most common enteric bacterial pathogens in children younger than 18 months. Fecal samples that tested positive for Aeromonas only by molecular detection had significantly higher CT values than fecal samples that tested positive by both molecular detection and bacterial culture. In conclusion, our findings reveal that Aeromonas enteric pathogens exhibit an age-related three-peak infection pattern, distinguishing them from other enteric bacterial pathogens. Moreover, the high rate of Aeromonas enteric infection discovered in this study suggests that Aeromonas species should be routinely tested in diagnostic laboratories. Our data also show that combining qPCR with bacterial culture can enhance the detection of enteric pathogens. IMPORTANCE Aeromonas species are emerging human enteric pathogens. However, these species are currently not routinely detected in many diagnostic laboratories, and no studies have reported the detection of Aeromonas enteric infection using molecular methods. We investigated the presence of Aeromonas species and four other enteric bacterial pathogens in 341,330 fecal samples from patients with gastroenteritis using quantitative real-time PCR (qPCR) methods. Interestingly, we discovered that Aeromonas species were the second most common bacterial enteric pathogens in patients with gastroenteritis, exhibiting a novel infection pattern compared to those of other enteric pathogens. Furthermore, we found that Aeromonas species were the most prevalent enteric bacterial pathogens in children aged 6 to 18 months. Our data also revealed that qPCR methods exhibit higher sensitivity in detecting enteric pathogens compared to that of bacterial culture alone. Moreover, combining qPCR with bacterial culture enhances the detection of enteric pathogens. These findings emphasize the importance of Aeromonas species in public health.

Rational Use of Antibiotics and Education Improved Aeromonas Necrotizing Fasciitis Outcomes in Taiwan: A 19-Year Experience

BACKGROUND

Aeromonas necrotizing fasciitis (NF) causes high rates of amputation and mortality, even after aggressive surgical debridement and antibacterial therapy. This study investigated the effects of rational use of antibiotics and education by infectious disease (ID) physicians on Aeromonas NF treatment outcomes.

METHODS

Retrospective review for conducted for four years (period I, without an ID physician, December 2001 to December 2005) and 15 years (period II, with an ID physician, January 2006 to March 2021). In period II, the hospital-wide computerized antimicrobial approval system (HCAAS) was also implemented. A pretest-posttest time series analysis compared the two periods. Differences in clinical outcomes, demographics, comorbidities, signs and symptoms, laboratory findings, Aeromonas antibiotic susceptibility, and antibiotic regimens were compared between the two periods.

RESULTS

There were 19 patients in period I and 53 patients in period II. Patients had a lower rate of amputation or mortality in period II (35.8%) compared with period I (63.2%). Forty-four patients (61.1%) had polymicrobial infections. In the emergency room, the rate of misdiagnosis decreased from 47.4% in period I to 28.3% in period II, while effective empiric antibiotic usage increased from 21.1% in period I to 66.0% in period II. After the ID physician's adjustment, 69.4% received monotherapy in period II compared to 33.3% in period I.

CONCLUSIONS

Because Aeromonas NF had a high mortality rate and was often polymicrobial, choosing an antibiotic regimen was difficult. Using the HCAAS by an experienced ID physician can improve rational antibiotic usage and clinical outcomes in Aeromonas NF.

Culturomics revealed the bacterial constituents of the microbiota of a 10-year-old laboratory culture of planarian species S. mediterranea

The planarian species Schmidtea mediterranea is a flatworm living in freshwater that is used in the research laboratory as a model to study developmental and regeneration mechanisms, as well as antibacterial mechanisms. However, the cultivable microbial repertoire of the microbes comprising its microbiota remains unknown. Here, we characterized the bacterial constituents of a 10-year-old laboratory culture of planarian species S. mediterranea via culturomics analysis. We isolated 40 cultivable bacterial species, including 1 unidentifiable species. The predominant phylum is Proteobacteria, and the most common genus is Pseudomonas. We discovered that parts of the bacterial flora of the planarian S. mediterranea can be classified as fish pathogens and opportunistic human pathogens.

The Isolation of Aeromonas Species and Other Common Enteric Bacterial Pathogens from Patients with Gastroenteritis in an Australian Population

Aeromonas species are emerging human enteric pathogens. However, systematic analysis of Aeromonas species infection in human gastroenteritis in comparison with other enteric bacterial pathogens in the Australian population is lacking. Here we analysed the isolation of Aeromonas species and other bacterial pathogens in five consecutive years (2015–2019) from 375,842 stool samples of patients with gastroenteritis in a large Australian diagnostic laboratory and identified a subset (48 isolates) of Aeromonas isolates to species level, using multilocus phylogenetic analysis. Aeromonas species were the third most common bacterial pathogens, following Campylobacter and Salmonella species. Aeromonas infection rate was significantly correlated with increasing age (p < 0.001). Aeromonas species were more often isolated in warm seasons and in males than females (p < 0.001). Five Aeromonas species were identified. Most of the infections were from three species, namely Aeromonas veronii (52%), Aeromonas caviae (27%) and Aeromonas hydrophila (12.5%). The majority of patients with Aeromonas species infection did not have a documented overseas travel history. The findings from this study support the importance of Aeromonas species in human gastroenteritis and suggest that the sources of Aeromonas infection in Australian patients should be further investigated.

Prevalence, Virulence Gene Distribution and Alarming the Multidrug Resistance of Aeromonas hydrophila Associated with Disease Outbreaks in Freshwater Aquaculture

The study aims to evaluate the infection prevalence, virulence gene distribution and antimicrobial resistance of Aeromonas hydrophila associated in diseased outbreaks of cultured freshwater fish in Northern Vietnam. The confirmed A. hydrophila were screened for the presence of the five pitutative-virulence genes including aerolysin (aerA), hemolysin (hlyA), cytotonic enterotoxin (act), heat-labile cytotonic enterotoxin (alt), and heat-stable enterotoxin (ast), and examined the susceptibility to 16 antibiotics. A total of 236 A. hydrophila isolates were recovered and confirmed from 506 diseased fish by phenotypic tests, PCR assays, and gyrB, rpoB sequenced analyses, corresponding to the infection prevalence at 46.4%. A total of 88.9% of A. hydrophila isolates harbored at least one of the tested virulence genes. The genes aerA and act were most frequently found (80.5% and 80.1%, respectively) while the ast gene was absent in all isolates. The resistance to oxacillin, amoxicillin and vancomycin exhibited the highest frequencies (>70%), followed by erythromycin, oxytetracycline, florfenicol, and sulfamethoxazole/trimethoprim (9.3–47.2%). The multiple antibiotic resistance (MAR) index ranged between 0.13–0.88 with 74.7% of the isolates having MAR values higher than 0.2. The results present a warning for aquaculture farmers and managers in preventing the spread of A. hydrophila and minimizing antibiotic resistance of this pathogen in fish farming systems.

Independent Predictors of Mortality for Aeromonas Necrotizing Fasciitis of Limbs: An 18-year Retrospective Study

Necrotizing fasciitis (NF) of the limbs caused by Aeromonas species is an extremely rare and life-threatening skin and soft tissue infection. The purpose of this study was to evaluate the specific characteristics and the independent predictors of mortality in patients with Aeromonas NF. Sixty-eight patients were retrospectively reviewed over an 18-year period. Differences in mortality, demographics data, comorbidities, symptoms and signs, laboratory findings, microbiological analysis, empiric antibiotics treatment and clinical outcomes were compared between the non-survival and the survival groups. Twenty patients died with the mortality rate of 29.4%. The non-survival group revealed significant differences in bacteremia, monomicrobial infection, cephalosporins resistance, initial ineffective empiric antibiotics usage, chronic kidney disease, chronic hepatic dysfunction, tachypnea, shock, hemorrhagic bullae, skin necrosis, leukopenia, band polymorphonuclear neutrophils >10%, anemia, and thrombocytopenia. The multivariate analysis identified four variables predicting mortality: bloodstream infection, shock, skin necrosis, and initial ineffective empirical antimicrobial usage against Aeromonas. NF caused by Aeromonas spp. revealed high mortality rates, even through aggressive surgical debridement and antibacterial therapies. Identifying those independent predictors, such as bacteremia, shock, progressive skin necrosis, monomicrobial infection, and application of the effective antimicrobial agents against Aeromonas under the supervision of infectious doctors, may improve clinical outcomes.

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

目的

分析患有血液系统疾病患者气单胞菌血流感染的临床及实验室特征，为该类患者气单胞菌感染的防治提供依据。

方法

回顾性分析中国医学科学院血液病医院2014年1月至2018年12月5年发生气单胞菌血症的血液系统疾病患者，收集患者临床感染特征、菌株耐药性、发生季节、治疗及转归情况等相关信息。

结果

共42例血液病患者发生气单胞菌血流感染，其中39例（92.9%）血流感染发生于粒细胞缺乏（粒缺）期，平均发热时间为4（1~27）d，22例（52.4%）患者症状仅为发热，6例（14.3%）伴消化道症状（腹痛、腹泻、恶心、上消化道出血），8例（19.0%）伴肺部感染，13例（31.0%）伴皮肤软组织感染。7例（16.7%）患者死亡，且均伴皮肤软组织感染。气单胞菌对碳青霉烯类抗菌药物的耐药率为68.3%~70.7%，而对头孢菌素类、喹诺酮类及氨基糖苷类抗菌药物的耐药率均小于10%。

结论

血液系统疾病合并气单胞菌血流感染主要发生在粒缺期，主要以发热为主，当伴有皮肤软组织感染时死亡率高。抗菌药物选择应依据药敏结果，避免使用碳青霉烯类抗菌药物。

Isolation, Identification and Characteristics of Aeromonas veronii From Diseased Crucian Carp (Carassius auratus gibelio)

Aeromonas species often cause disease in farmed fish. In the present study, dominant bacteria were isolated from diseased crucian carp (Carassius auratus gibelio). Based on this, a bacterial isolate was tentatively named CFJY-623. This isolate was identified as Aeromonas veronii based on analysis of its morphological, physiological, and biochemical features, as well as 16S rRNA and gyrB gene sequences. Six virulence genes related to pathogenicity including aerolysin, cytotonic enterotoxins, elastase, glycerophospholipid: cholesterol acyltransferase, lipase, and serine protease were identified in this A. veronii isolate. The median lethal dosage (LD50) of the CFJY-623 isolate for crucian carp was determined as 1.31 × 107 CFU/mL. Artificial experimental infection showed that the CFJY-623 isolate caused considerable histological lesions in the fish, including tissue cell degeneration, necrosis, and inflammatory cell infiltrating. Drug sensitivity testing showed that the isolate was susceptible to aminoglycosides, carbapenemes, and nitrofurans. Exploring its growing features showed that this isolate exhibited a high level of environmental adaptability. These results provided a scientific basis for the identification of A. veronii and treatment for fish infected by this pathogen.

Wild Nutria (Myocastor coypus) Is a Potential Reservoir of Carbapenem-Resistant and Zoonotic Aeromonas spp. in Korea

The emergence and spread of antibiotic-resistant Aeromonas spp. is a serious public and animal health concern. Wild animals serve as reservoirs, vectors, and sentinels of these bacteria and can facilitate their transmission to humans and livestock. The nutria (Myocastor coypus), a semi-aquatic rodent, currently is globally considered an invasive alien species that has harmful impacts on natural ecosystems and carries various zoonotic aquatic pathogens. This study aimed to determine the prevalence of antibiotic-resistant zoonotic Aeromonas spp. in wild invasive nutrias captured in Korea during governmental eradication program. Three potential zoonotic Aeromonas spp. (A. hydrophila, A. caviae, and A. dhakensis) were identified among isolates from nutria. Some strains showed unexpected resistance to fluoroquinolones, third-generation cephalosporins, and carbapenems. In carbapenem-resistant isolates, the cphA gene, which is related to intrinsic resistance of Aeromonas to carbapenems, was identified, and phylogenetic analysis based on this gene revealed the presence of two major groups represented by A. hydrophila (including A. dhakensis) and other Aeromonas spp. These results indicate that wild nutrias in Korea are a potential reservoir of zoonotic and antibiotic-resistant Aeromonas spp. that can cause infection and treatment failure in humans. Thus, measures to prevent contact of wild nutrias with livestock and humans are needed.

Severe acute cellulitis and sepsis caused by Aeromonas spp. in a dog on immunosuppressive therapy

OBJECTIVE

To describe the clinical presentation, diagnostic investigation, and medical management of a dog on immunosuppressive therapy that developed a severe soft tissue infection attributed to Aeromonas hydrophila/caviae.

CASE SUMMARY

A 5-year-old female neutered Border Collie dog was presented for investigation of a rapidly growing skin lesion. The dog had been diagnosed with immune-mediated thrombocytopenia and was receiving immunosuppressive therapy for 5 weeks. Physical examination at initial presentation revealed no abnormalities except a 6 cm raised, erythematous, firm, and painful swelling on the ventral abdomen. Within 12 hours of admission, the lesion had expanded to cover much of the ventrum and some areas had begun to slough. The patient had also become obtunded and exhibited pyrexia, tachypnea, tachycardia as well as extreme pain around the lesion. The dog's clinical signs and hematology results were consistent with sepsis. Histopathology showed severe acute suppurative cellulitis and panniculitis and a heavy growth of A. hydrophila/caviae was obtained on tissue culture. The infection was treated with trimethoprim sulphadiazine, based on culture and susceptibility results.

UNIQUE INFORMATION PROVIDED

This is the first reported case of severe panniculitis and cellulitis caused by Aeromonas spp. in a dog. Aeromonas spp. should be considered a differential diagnosis for cases of severe soft tissue infection, especially in immune-compromised animals or those with a history of aquatic exposure.

Aeromonas sobria peritonitis in a peritoneal dialysis (PD) patient: a case report and review of the literature

Background

Peritonitis is a common cause of catheter removal and mortality in the patient undergoing peritoneal dialysis (PD). Various pathogenic organisms have been identified as the etiology of PD-related peritonitis, among which Aeromonas sobria is a rare one. Several studies have indicated that Aeromonas sobria might be of particular clinical significance because of its enterotoxin production. We here present a case of peritonitis due to Aeromonas sobria in a PD patient and review of the related literature.

Case presentation

A 37-year-old man with chronic renal failure who was secondary to chronic glomerulonephritis had been on PD for approximately 6 months without any episode of peritonitis. In July 2015, he was admitted to the hospital for fever, vomiting, abdominal pain, diarrhea and cloudy dialysate several hours after eating stinky tofu. The peritoneal effluent culture yielded Aeromonas sobria. The patient was given intraperitoneal amikacin and intravenous levofloxacin for 10 days. And the patient’s symptoms such as diarrhea, abdominal pain were relieved and the cloudy effluent turned to be clear. Unfortunately, peritoneal dialysis catheter was blocked because of fibrin clot formation in the setting of inflammation, and finally it was removed.

Conclusions

Aeromonas species are rare causes of PD-related peritonitis, however they should not be ignored. Clinicians should be aware of monitoring the hygiene protocol and retraining patients at regular intervals, especially for such rare cases.

Taxonomy, virulence genes and antimicrobial resistance of Aeromonas isolated from extra-intestinal and intestinal infections

BACKGROUND

Clinical characteristics (taxonomy, virulence genes and antimicrobial resistance ) of Aeromonas in isolated from extra-intestinal and intestinal infections were investigated to describe epidemiology, associated virulence factors and optimal therapy options.

METHODS

Clinical samples (n = 115) of Aeromonas were collected from a general hospital in Beijing between the period 2015 and 2017. Taxonomy was investigate by Multilocus phylogenetic analysis (MLPA), 10 putative virulence factors by use of polymerase chain reaction (PCR) and antimicrobial resistance to 15 antibiotics by use of the microbroth dilution method.

RESULTS

The most common species of Aeromonas detected in samples of intestinal tract included; A. caviae (43.9%), A. veronii (35.7%), and A. dhakensis (12.2%). Prevalent species of Aeromonas collected from extra-intestinal infections included; A. hydrophila (29.4%), A. caviae (29.4%), and A. dhakensis (23.5%). A. hydrophila were detected in 1% of stool samples and 29.4% (5/17) of extra-intestinal infections. A. hydrophila strains in extra-intestinal infections were related to malignancy. The most common medical conditions among patients with Aeromonas infections included malignancy and liver-transplant related cholecystitis. Multiple drug resistance (MDR) was prevalent in extra-intestinal isolates (82.3%, 14/17) and was greater than the prevalence in intestinal isolates (30.6%, 30/98) (P < 0.05). Resistant rates of extra-intestinal isolates were 70.6, 35.3, 23.5 and 5.9% for ceftriaxone, ciprofloxacin, gentamicin and imipenem, respectively, and were higher than found in previous studies. Despite differences in the number and type of virulence genes among samples of Aeromonas, no significant correlation was found between invasion and virulent genes in intestinal or extra-intestinal infections.

CONCLUSIONS

Overall results of this study support a role for Aeromonas spp. as a potential causative infectious agent of gastroenteritis, and malignancy, liver cirrhosis, post liver transplantation in immunocompromised patients. A. hydrophila was more prevalent in samples of extra-intestinal infections when compared to samples of intestinal infections, and was especially prominent in samples of patients presenting with malignancy. Aeromonas isolates from extra-intestinal samples had high rates of drug resistance but 3rd generation cephalosporins, fluoroquinolones and aminoglycosides remain as options to treat severe diarrhea. However, increasing MDR of extra-intestinal infection samples warrants monitoring.

Speciation, clinical profile & antibiotic resistance in Aeromonas species isolated from cholera-like illnesses in a tertiary care hospital in north India

Background & objectives:

Aeromonas species have been reported to cause various illnesses in humans such as wound infections, septicaemia, peritonitis and pneumonia. Their role in causation of cholera-like illness is also being increasingly recognized. This retrospective study was done to know the presence of Aeromonas as a cause of acute diarrhoea in a tertiary care hospital and to find the common species of Aeromonas causing diarrhoea and their antibiotic susceptibility patterns.

Methods:

Fifty isolates of Aeromonas were obtained over a period of 15 yr from 2000 to 2014 from patients of suspected acute gastroenteritis resembling cholera. Biotyping was done for 35 of these isolates available in culture collection, based on a panel of 13 biochemical reactions. Antibiogram was put up for all of these isolates by disk diffusion methods and interpreted according to the Clinical and Laboratory Standards Institute guidelines.

Results:

Of the 50 patients of Aeromonas-related acute gastroenteritis, 13 (26%) had typical features of cholera with rice water stools and severe dehydration. Eight patients (16%) had dysentery-like picture. One patient died of severe dehydration and septicaemia. The most common species were found to be Aeromonas caviae (34%) followed by Aeromonas veronii biovar veronii (29%), Aeromonas veronii biovar sobria (26%) and Aeromonas hydrophila (9%). All tested isolates were uniformly susceptible to cefepime, amikacin, azithromycin and meropenem; 14 per cent were susceptible to amoxicillin, 32 per cent to nalidixic acid, 60 per cent to co-trimoxazole, 54 per cent to ciprofloxacin, 60 per cent to ofloxacin, 74 per cent to chloramphenicol, 76 per cent to ceftriaxone, 74 per cent to cefotaxime, 88 per cent to gentamicin and 86 per cent to furoxone.

Interpretation & conclusions:

Aeromonas is an important, often neglected pathogen capable of causing a variety of gastrointestinal tract symptoms such as acute diarrhoea and dysentery and may even mimic cholera. It is, therefore, pertinent to recognize this pathogen as an important agent in the causation of severe diarrhoea.

Unusual Severe Extra-Intestinal Manifestations of a Common Enteric Pathogen-Aeromonas Spp

INTRODUCTION

Aeromonas spp. are halophilic, Gram-negative bacilli. They are widely distributed in the soil and aquatic environment and have been associated with various extra-intestinal infections, such as skin and soft-tissue infections, meningitis, bacteraemia etc. The most common species associated with extra-intestinal infection is Aeromonas hydrophila.

AIM

To get the overview of clinical presentations, underlying predisposing factors associated with the extra-intestinal infections caused by Aeromonas species and their antimicrobial susceptibility pattern.

MATERIALS AND METHODS

Extra-intestinal cases of Aeromonas spp. admitted during December 2015 to October 2016 in the tertiary care hospital of South Karnataka coastal region were analysed retrospectively. The isolates were identified by Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) VITEK^®MS and antimicrobial susceptibility testing was performed by VITEK^®2 system (bioMérieux, Inc., Durham, NC) respectively. Clinical manifestations and management of the cases were noted from the clinical records. Clinical and microbiological findings presented as mean±standard deviation, frequency and percentage.

RESULTS

We included 26 cases in this study, from whom Aeromonas spp. were isolated alone or with another microorganism. Most widespread infection was Skin and Soft Tissue Infection (SSTI) (24, 92.3%). In 50% (12/24) cases, SSTI developed due to trauma. In 45.8% (11/24), underlying co-morbid conditions were present. The common site of infection was lower extremities (16/24, 66.7%) and 62.5% (15/24) of them presented with severe gangrene of the affected site. Other than SSTI, we encountered with two cases of keratitis and cholangitis respectively. A. hydrophila were frequently isolated species (23/26, 88.5%). The analysis of antimicrobial susceptibility showed, 13% isolates were Multidrug Resistant (MDR). Carbapenem resistance was also noted.

CONCLUSION

We had isolated Aeromonas spp. from different extra-intestinal sites. Most common extra-intestinal manifestation by this organism was post-traumatic wound infection. Clinical spectrum of this infection confused the clinician with other organisms like group B Streptococcus, Clostridium spp. etc., and mislead them in empirical management. Finally with the microbiological support all the cases were treated either conservatively or in combination with surgical debridement or amputation depending on the situation.

Aeromonas Hydrophila Endocarditis with Ruptured Mycotic Aneurysm of Right Renal Artery

Aeromonas hydrophila has been infrequently reported as a cause of infection in humans. It has been associated with a variety of clinical syndromes but Aeromonas-related endocarditis is extremely rare. We present the case of a 76-year-old diabetic patient who was admitted to our hospital due to severe lumbar pain resistant to nonsteroidal anti-inflammatory drugs accompanied by fever (up to 38.5°C). The vital signs were normal and the physical examination was unremarkable except for tenderness over right flank. Laboratory investigation showed a mild leukocytosis (white blood cell count of 11,360×10⁶/L) with elevation of inflammatory markers. Cardiac ultrasound showed a large vegetation on the mitral valve. Abdominal computed tomogrpahy revealed a ruptured aneurysm of the right renal artery. Multiple sets of blood culture grew A. hydrophila.

Multidrug-Resistant Aeromonas veronii Recovered from Channel Catfish (Ictalurus punctatus) in China: Prevalence and Mechanisms of Fluoroquinolone Resistance

To emphasize the importance of the appropriate use of antibiotics in aquaculture systems, the prevalence of resistance to 25 antimicrobials was investigated in 42 Aeromonas veronii strains isolated from farm-raised channel catfish in China in 2006-2012. All experiments were based on minimal inhibitory concentrations (MICs), and susceptibility was assessed according to the Clinical and Laboratory Standards Institute. Some isolates displayed antibiotic resistance to the latest-generation fluoroquinolones (i.e., ciprofloxacin, levofloxacin, and norfloxacin) in vitro. Therefore, we screened for genes conferring resistance to fluoroquinolones and performed conjugation experiments to establish the resistance mechanisms. The antibiotic resistance rates were 14.29-21.42% to three kinds of fluoroquinolones: ciprofloxacin, levofloxacin, and norfloxacin. Among the 42 strains isolated, 15 carried the qnrS2 gene. The MICs of the fluoroquinolones in transconjugants with qnrS2 were more than fourfold higher compared with the recipient. Among the fluoroquinolone-resistant A. veronii strains, eight had point mutations in both gyrA codon 83 (Ser⁸³→Ile⁸³) and parC codon 87 (Ser⁸⁷→Ile⁸⁷). However, five isolates with point mutations in parC codon 52 remained susceptible to the three fluoroquinolones. In conclusion, the mechanisms of fluoroquinolone resistance in A. veronii isolates may be related to mutations in gyrA codon 83 and parC codon 87 and the presence of the qnrS2 gene.

Antibiogram characterization and putative virulence genes in Aeromonas species isolated from pig fecal samples

Aeromonas species are broadly distributed in nature and agricultural environments and have been isolated from feces, bedding, and drinking water of healthy pigs. We assessed the incidence, virulence properties, and antimicrobial resistance profile of Aeromonas spp., isolated from pig feces. Antibiogram was done using the disc diffusion methods, and polymerase chain reaction was used for the detection of putative virulence genes. Identification of isolates revealed three phenotypic species with percentage distribution as follows: Aeromonas hydrophila 23 (45.1 %), Aeromonas caviae 16 (31.4 %), and Aeromonas sobria 12 (23.5 %). All Aeromonas isolates in the study were absolutely susceptible to cefotaxime and resistant to penicillin. A. cavaie and A. sobria demonstrated absolute susceptibility against ciprofloxacin and streptomycin. Aeromonas species showed varied susceptibility to cephalothin as follows: A. hydrophila 78.3 %, A. cavaie 93.7 %, and A. sobria 91.7 %. The percentage distribution of virulence genes among Aeromonas isolates were as follows: Aerolysin (aer) 74.5 %, flagellin gene (fla) 68.6 %, cytotoxin (hly A) 43.1 %, lipase (lip) 39.2 %, enterotoxic activities (ast) 31.3 %, and cytotonic gene (alt) 13.7 %. Reports from this study shows that Aeromonas species isolated from pig fecal samples are multi-drug resistant and possess virulence potential which may result to possible risk of human or animal infection and likely contamination of food and water from this sources.

Detection of antibiotic resistance, virulence gene determinants and biofilm formation in Aeromonas species isolated from cattle

This study aimed to assess the antibiogram of Aeromonas strains recovered from cattle faeces and the potential pathogenic status of the isolates. The antibiogram of the Aeromonas isolates demonstrated total resistance to clindamycin oxacillin, trimethoprim, novobiocin and ticarcillin. However, Aeromonas strains were sensitive to cefotaxime, oxytetracycline and tobramycin. The Aeromonas strains from Lovedale and Fort Cox farms were found to possess some virulence genes. The percentage distribution was aer 71.4%, ast 35.7%, fla 60.7%, lip 35.7% and hlyA 25% for Lovedale farm and aer 63.1%, alt 10.5%, ast 55.2%, fla 78.9%, lip 21% and hlyA 35.9% for Fort Cox farm. Class 1 integron was present in 27% of Aeromonas isolates; the bla TEM gene was present in 34.8%, while the blaP1 class A β-lactamase gene was detected in 12.1% of the isolates. Approximately 86% of the isolates formed a biofilm on microtitre plates. The presence of multiple antibiotic resistance and virulence genes in Aeromonas isolates from cattle faeces reveals the pathogenic and infectious importance of these isolates and is of great significance to public health. The possession of a biofilm-forming capability by such isolates may lead to difficulty during the management of infection related to Aeromonas species.

Ocorrência de Aeromonas spp. em alimentos de origem animal e sua importância em saúde pública

Aeromonas spp. são bactérias Gram negativas, opor-tunistas, de natureza ubíqua, isoladas principalmente de amostras de água. Até o presente momento foram reconhecidas 31 espé-cies, sendo as de maior importância médica Aeromonas hydrophila, Aeromonas caviae e Aeromonas veronii. A patogenicidade do gênero é considerada multifatorial, sendo este produtor de diversos tipos de toxinas e com envolvimento de outros fatores capazes de facilitar a penetração e o estabelecimento do agente no hospedeiro, causando doença. O objetivo desta revisão é elucidar o papel dos alimentos de origem animal como fontes de contaminação de bactérias do gênero Aeromonas para o ser humano. Isolamentos de aeromonas de diversos produtos de origem animal têm sido relatados, como carne, leite e seus derivados, além de frutos do mar, e em ambientes de processamento, como abatedouros, frigorífcos e laticínios. Tem-se buscado determinar fontes de contaminação dos alimentos, e a água foi definida como o principal disseminador. Aeromonas já foi defnida como sendo a causadora de diversas enfermidades, desde afecções gastrointestinais até casos de meningite e morte. Considerando os alimentos de origem animal como importantes veículos de transmissão para o ser humano e o reconhecimento da água como fonte de disseminação do agente, torna-se imprescindível o tratamento adequado da água utilizada nos estabelecimentos processadores de alimentos para a segurança alimentar.

Relative frequency, characteristics, and antimicrobial susceptibility patterns of Vibrio spp., Aeromonas spp., Chromobacterium violaceum, and Shewanella spp. in the northern territory of Australia, 2000-2013

Vibrio, Aeromonas, Chromobacterium violaceum, and Shewanella (VACS) are water-associated Gram-negative organisms that can cause a variety of infections. The frequency, patient characteristics, and antimicrobial susceptibilities for 468 isolates from 442 patients from the Northern Territory were reviewed. Aeromonas spp. (312 of 468; 67%) were most commonly isolated followed by Vibrio spp. (71 of 468; 15%), Shewanella spp. (61 of 468; 13%), and C. violaceum (24 of 468; 5%). A strong male predominance was found (male to female ratio of 2.3:1). Skin and soft tissue isolations (373 of 468; 80%) from lower limb infections (222 of 371; 60%) were the most common clinical manifestation. The episodes were usually polymicrobial (281 of 468; 60%). Coisolates included Staphylococcus aureus (137 of 468; 29%), β-hemolytic streptococci (74 of 468; 16%), enterobacteriaceae (111 of 468; 24%), non-fermentative Gram-negative bacilli (35 of 468; 7%), and other VACS organisms (37 of 468; 8%). Antimicrobial resistance of VACS organisms to ciprofloxacin (0-4%), cefepime (0-3%), and gentamicin (0-0.8%) and Vibrio spp., Aeromonas spp., and Shewanella to cotrimoxazole (0-3%) was rarely shown. For water-associated lower limb skin and soft tissue infections in the tropics, clinicians should consider empirical antimicrobial therapy with agents active against S. aureus and VACS organisms.

Antibiogram profiling and pathogenic status of Aeromonas species recovered from Chicken

Poultry meat and its products are widely consumed by humans globally, however, Aeromonas infections in poultry have been reported in different parts of the world with devastating effects. This study was carried out to assess the antibiogram and biofilm forming potential of Aeromonas isolated from chicken fecal samples. Aeromonas isolates were screened for antibiotic susceptibility using antibiotics disk and biofilm producing potentials on abiotic surfaces. Nineteen isolates recovered from chicken feces were 100% sensitive to ciprofloxacin, gentamicin and the tetracyclines. About 53% of Aeromonas isolates were resistant to erythromycin and 47% resistant to streptomycin. Eight isolates (42.1%) were found to be moderate producers of biofilm, 31.6% (6/19) were weak producers of biofilm, 10.5% (2/19) were non biofilm producers while 15.8% (3/19) were strong producers. The present investigation shows a prevalence of potentially pathogenic Aeromonas strains in chicken feces, suggesting potential group at risk for Aeromonas infection which could be dissemination to other animals or humans with close contact and the wider community.

Multidrug-resistant (MDR) Aeromonas recovered from the metropolitan area of Valencia (Spain): diseases spectrum and prevalence in the environment

Aeromonas infections are rare in Europe and often related to traveller's diarrhoea. A total of 185 Aeromonas isolates from river water, fish and clinical sources, recovered during a 1-year period, were used to investigate the disease spectrum and impact of multidrug-resistant (MDR) strains. They were all identified by biochemical tests and 25% of them were also identified by sequencing of the 16S rRNA gene. The minimum inhibitory concentrations (MICs) of 21 antimicrobials were determined for all isolates by broth microdilution/E-strips methods, and susceptibility was assessed according to the Clinical and Laboratory Standards Institute (CLSI). Strains pathogenicity was determined by using Swiss Webster mice as the animal model. Aeromonas diseases had an incidence of around 20 cases/million inhabitants in the metropolitan area of Valencia (Spain). Acute gastroenteritis in children with no history of travel abroad was the main pathology. These cases were related to A. caviae, A. veronii biovar sobria, A. hydrophila and A. dhakensis. A significant incidence of A. caviae in humans was found, while the other species were equally present in clinical and environmental origins. A. jandaei, A. bestiarum and A. media had mainly an environmental distribution. The prevalence of MDR Aeromonas was maximal in clinical samples, and resistance phenotypes were significantly related to this source. 7.2% of environmental Aeromonas was resistant to at least five drugs; most of them were moderately virulent for mice and, in addition, belonged to clinically significant species. The present study demonstrates a diseases spectrum similar to that reported in tropical countries, and also that pathogenic and heavily MDR Aeromonas are present in environmental reservoirs. MDR Aeromonas from any source analysed were susceptible to aztreonam, netilmicin, cefotaxime, ceftazidime, cefepime and fluoroquinolones.

Leech therapy for epidermoid cysts and review of the literature

Hirudo medicinalis sucks blood directly through the external mammalian skin. We recently observed a healthy 64-year-old Iranian man, who presented with numerous asymptomatic multilobular oval-to-round well-defined 0.5 to 1.5 cm cystic lesions with central umbilication (central black eschar) over the upper portion of his chest. We made the diagnosis of epidermoid cyst, giant comedone and leech bite on the basis of the constellation of clinical features. The patient was treated with oral ciprofloxacin at a dose of 2 g daily, and 2% topical erythromycin solution. Despite improvement, the evidence of cystic lesions persisted. There was no history of similar lesions in any other family member. There was no history of trauma. The patient was not using any topical or systemic medication. Two weeks before his visit, he had a history of leech therapy under the supervision of a general practitioner. His medical history was significant for leech therapy of the lesions, five days previously. He was followed up for another two weeks and after disappearance of the inflammation, with the patient under local anesthesia, the well-circumscribed mass was completely evacuated with a sharp curette and comedone extractor. The patient was subsequently lost to follow-up.

CONCLUSION

Considering the efficacy of leeches, it would be favorable to breed a germ-free leech. In Iran, the use of the leeches in surgery, in recent years, has been infrequent. It appears that the positive effects of this ancient remedy may now be explained through scientific methods, promising potentially even more uses of this admirable creature in medicine.

Necrotizing soft-tissue infections

NSTI is a life-threatening, surgical, and medical emergency. Clinical presentation, at least in the initial phase, can be misleading. Various studies have shown that delay in surgical debridement is associated with increased mortality. A high index of suspicion is important in early recognition and in instituting prompt therapy without delay. Early diagnosis, aggressive surgical debridement, aggressive supportive care, and optimal presumptive antibiotic therapy significantly improve morbidity and mortality associated with NSTIs.

Emerging Aeromonas species infections and their significance in public health

Aeromonas species are ubiquitous bacteria in terrestrial and aquatic milieus. They are becoming renowned as enteric pathogens of serious public health concern as they acquire a number of virulence determinants that are linked with human diseases, such as gastroenteritis, soft-tissue, muscle infections, septicemia, and skin diseases. Proper sanitary procedures are essential in the prevention of the spread of Aeromonas infections. Oral fluid electrolyte substitution is employed in the prevention of dehydration, and broad-spectrum antibiotics are used in severe Aeromonas outbreaks. This review presents an overview of emerging Aeromonas infections and proposes the need for actions necessary for establishing adequate prevention measures against the infections.

Aeromonas hydrophila subsp. dhakensis isolated from feces, water and fish in Mediterranean Spain

Eight Aeromonas hydrophila-like arabinose-negative isolates from diverse sources (i.e., river freshwater, cooling-system water pond, diseased wild European eels, and human stools) sampled in Valencia (Spain) during 2004–2005, were characterized by 16S rRNA gene sequencing and extensive biochemical testing along with reference strains of most Aeromonas species. These isolates and all reference strains of A. hydrophila subsp. dhakensis and A. aquariorum showed a 16S rRNA sequence similarity of 99.8–100%, and they all shared an identical phenotype. This matched exactly with that of A. hydrophila subsp. dhakensis since all strains displayed positive responses to the Voges-Prokauer test and to the use of dl-lactate. This is the first report of A. hydrophila subsp. dhakensis recovered from environmental samples, and further, from its original isolation in India during 1993–1994. This was accurately identified and segregated from other clinical aeromonads (A. hydrophila subsp. hydrophila, A. caviae, A. veronii biovars veronii and sobria, A. trota, A. schubertii and A. jandaei) by using biochemical key tests. The API 20 E profile for all strains included in A. hydrophila subsp. dhakensis was 7047125. The prevalence of this species in Spanish sources was higher for water (9.4%) than for feces (6%) or eels (1.3%). Isolates recovered as pure cultures from diseased eels were moderately virulent (LD₅₀ of 3.3×10⁶ CFU fish⁻¹) to challenged eels in experimental trials. They were all resistant to ticarcillin, amoxicillin-clavuranic acid, cefoxitin, and imipenem, regardless of its source. Our data point to A. hydrophila subsp. dhakensis as an emerging pathogen for humans and fish in temperate countries.

Characterization of pathogenic Aeromonas veronii bv. veronii associated with ulcerative syndrome from chinese longsnout catfish (Leiocassis longirostris Günther)

273 bacterial strains were isolated from 20 Chinese longsnout catfish samples. The biochemical characteristics of all strains conformed to the species description of Aeromonas veronii bv. veronii on the basis of Vitek GNI+ card. Furthermore, 16S rDNA, gyrB and rpoD sequences of the representative strain PY50 were sequenced and showed high similarity with A. veronii bv. veronii in Genbank. Antibiotic-resistance of the representative strain PY50 was assessed by the Kirby-Bauer disk diffusion method, and the results showed it was susceptible and moderately susceptible to 13 and 4 of the 21 antimicrobial agents tested. Extracellular products of strain PY50 contained gelatinase, lecithinase, elastase, most of lipase and lipopolysaccharide. Virulence of strain PY50 and extracellular products to Chinese longsnout catfish were also tested, and LD50 were about 3.47×10(4) CFU per fish and 11.22 μg per fish in intraperitoneal injection respectively. This is the first report that A. veronii bv. veronii was the pathogenic agent of ulcerative syndrome in Chinese longsnout catfish.

Outbreak of Abortions and Infertility in Thoroughbred Mares Associated with Waterborne Aeromonas hydrophila

At a thoroughbred equine breeding farm near Hissar (Haryana), three mares aborted in their seventh month of pregnancy. The vaginal swabs of all aborted mares, and stomach contents, heart blood, liver, spleen and placenta of aborted fetuses yielded pure culture of Aeromonas hydrophila. In addition, A. hydrophila was also isolated from the vaginal swabs of three repeat breeding mares and faecal sample of a diarrheic foal. The source of infection was possibly water supply as all the water samples collected from taps, mother tank and storage tank were found to be positive for A. hydrophila. The antibiogram of all the isolates was similar showing resistance to ampicillin, carbenicillin, gentamicin, kanamycin and amikacin but sensitive to chloramphenicol, ciprofloxacin, cefuroxime, ceftriaxone, cotrimoxazole, cotrimazine, nitrofurantoin, streptomycin and tetracycline. All the 20 sera samples collected from three aborted and three repeat breeding, and eight in-contact mares, a diarrheic foal, three cows and two male buffaloes maintained at the same farm contained antibodies against A. hydrophila with titres ranging from 80 to 640. The water supply was instantly chlorinated using 0.05% sodium hypochlorite for three consecutive days and all the culturally positive mares were treated with intravaginal administration of 1 g ciprofloxacin, while the foal was given nitrofurantoin for three days. After one month, A. hydrophila could not be isolated either from mares or from their environment and antibody titre in all the seropositive animals showed a declining trend. Later, all the aborted and repeat breeding mares were confirmed to be pregnant. Thus, the present study indicated that water-borne A. hydrophila might be associated with equine abortions and infertility, and diarrhea in newborn foals.

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.

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.

Development of imipenem resistance in an Aeromonas veronii biovar sobria clinical isolate recovered from a patient with cholangitis

Several imipenem-susceptible and -resistant Aeromonas veronii biovar sobria isolates with different morphologies and antimicrobial susceptibilities recovered from bile samples of a patient with cholangitis were analysed. These isolates belonged to the same clone and the imipenem-resistant strains showed overexpression of the imiS gene, encoding a chromosomal carbapenemase. These results should make clinicians aware of the possible emergence of multidrug-resistant A. veronii biovar sobria, perhaps as a consequence of previous treatment of a urinary tract infection with amoxicillin plus clavulanic acid.

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.

Multiresistant waterborne pathogens isolated from water reservoirs and cooling systems

AIMS

To determine the incidence of multiple antibiotic-resistant strains of the emergent human pathogens Legionella pneumophila, Pseudomonas aeruginosa and mesophilic Aeromonas species among those isolated from water reservoirs and industrial cooling systems.

METHODS AND RESULTS

Water from four natural water reservoirs and four industrial cooling towers was sampled for 1 year period. The total heterotrophs, mesophilic Aeromonas, Pseudomonas spp. and Legionella spp. counts were performed as recommended by standard procedures, and the sensitivity of the isolates to 27 antibiotics was tested. A total of 117 Aeromonas, 60 P. aeruginosa and 15 L. pneumophila strains were isolated and identified by means of biochemical tests and DNA probes. 46.4% of Aeromonas, and 100% of P. aeruginosa isolates presented multiple resistance. Legionella pneumophila strains were generally sensitive to the drugs used.

CONCLUSIONS

Antibiotic-resistant pathogenic bacteria belonging to P. aeruginosa and mesophilic Aeromonas species are common in natural aquatic environments. Thus, the risk of waterborne diseases owing to domestic and industrial uses of freshwater should be re-examined from the increase of bacterial resistance point of view.

SIGNIFICANCE AND IMPACT OF THE STUDY

These data confirm the emergence of bacteria resistant to antibiotics in aquatic environments.

Molecular characterization of class 1 integrons and antimicrobial resistance in Aeromonas strains from foodborne outbreak-suspect samples and environmental sources in Taiwan

One hundred thirty-three Aeromonas spp. isolates were examined for multiple antibiotic resistance phenotypes and prevalence of class 1 integron sequences. Twenty-four (18.0%) of these isolates contained class 1 integron. Seven different class 1 integrons were found among 24strains, with a total of 10 different gene cassettes encoding for resistance to trimethoprim (dfr12 and dfr2d), aminoglycosides (aadA1 and aadA2), beta-lactam antibiotics (oxa2), chloramphenicol (catB3 and catB8), quaternary ammonium amines (qacE2), and 2 ORFs (orfD and orfF) with unknown function. Rate of antibiotic resistance was different between integron-positive and integron-negative strains. Trimethoprim and trimethoprim-sulphamethoxazole resistances were commonly associated with integron, and all of integron-positive isolates were multiple resistant to more than 3 agents. Resistance to as many as 10 antimicrobial agents were observed in integron-positive strains. Several cassette arrays of class 1 integrons identified in this study were not previously reported in Aeromonas strains. This study demonstrates the wide distribution of class 1 integron in Aeromonas spp. isolated from foodborne outbreak-suspect samples and environmental sources in Taiwan.

[Extraintestinal infection due to Aeromonas spp.: review of 38 cases]

INTRODUCTION

Aeromonas spp. typically cause gastroenteritis, but can occasionally produce extraintestinal infections. The aim of this study was to determine the clinical and microbiological characteristics of extraintestinal infections caused by Aeromonas spp. in our area.

PATIENTS AND METHODS

The clinical histories of patients with extraintestinal infections by Aeromonas spp. diagnosed in Hospital Universitario de Guadalajara (Guadalajara, Spain) from January 1990 to December 2005 were reviewed. Identification and susceptibility testing of the strains were performed by the MicroScan WalkAway-40 automated method (DadeBerhing).

RESULTS

Thirty-eight cases of extraintestinal infections were diagnosed: 18 abdominal infections, 11 skin and soft tissue infections, 3 urinary tract infections, and 3 episodes of bacteremia with no primary focus. The species most frequently found was A. hydrophila (16 cases). Infection occurred most often in patients with underlying diseases (76.3%), including malignancy (34.2%) and diabetes mellitus (21%). Polymicrobial infections were detected in 50% and the etiology was nosocomial in 21%. The mortality rate was 16.2%. Gentamicin, amikacin, cefotaxime and ciprofloxacin had the highest activity against the Aeromonas species isolated.

CONCLUSIONS

Aeromonas spp. as the causative infectious agent should be kept in mind in patients with infections of the biliary system, surgical wounds in the abdomen and posttraumatic cellulitis. Extraintestinal infection is usually polymicrobial, appears most commonly in patients with underlying diseases, and generally has a good prognosis. The most active antibiotics in vitro were gentamicin, amikacin, cefotaxime and ciprofloxacin.

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.

Genome sequence of Aeromonas hydrophila ATCC 7966T: jack of all trades

The complete genome of Aeromonas hydrophila ATCC 7966(T) was sequenced. Aeromonas, a ubiquitous waterborne bacterium, has been placed by the Environmental Protection Agency on the Contaminant Candidate List because of its potential to cause human disease. The 4.7-Mb genome of this emerging pathogen shows a physiologically adroit organism with broad metabolic capabilities and considerable virulence potential. A large array of virulence genes, including some identified in clinical isolates of Aeromonas spp. or Vibrio spp., may confer upon this organism the ability to infect a wide range of hosts. However, two recognized virulence markers, a type III secretion system and a lateral flagellum, that are reported in other A. hydrophila strains are not identified in the sequenced isolate, ATCC 7966(T). Given the ubiquity and free-living lifestyle of this organism, there is relatively little evidence of fluidity in terms of mobile elements in the genome of this particular strain. Notable aspects of the metabolic repertoire of A. hydrophila include dissimilatory sulfate reduction and resistance mechanisms (such as thiopurine reductase, arsenate reductase, and phosphonate degradation enzymes) against toxic compounds encountered in polluted waters. These enzymes may have bioremediative as well as industrial potential. Thus, the A. hydrophila genome sequence provides valuable insights into its ability to flourish in both aquatic and host environments.

Antimicrobial susceptibilities of Aeromonas spp. isolated from environmental sources

Aeromonas spp. are ubiquitous aquatic bacteria that cause serious infections in both poikilothermic and endothermic animals, including humans. Clinical isolates have shown an increasing incidence of antibiotic and antimicrobial drug resistance since the widespread use of antibiotics began. A total of 282 Aeromonas pure cultures were isolated from both urban and rural playa lakes in the vicinity of Lubbock, Texas, and several rivers in West Texas and New Mexico. Of these, at least 104 were subsequently confirmed to be independent isolates. The 104 isolates were identified by Biolog and belonged to 11 different species. The MICs of six metals, one metalloid, five antibiotics, and two antimicrobial drugs were determined. All aeromonads were sensitive to chromate, cobalt, copper, nickel, zinc, cefuroxime, kanamycin, nalidixic acid, ofloxacin, tetracycline, and sulfamethoxazole. Low incidences of trimethoprim resistance, mercury resistance, and arsenite resistance were found. Dual resistances were found in 5 of the 104 Aeromonas isolates. Greater numbers of resistant isolates were obtained from samples taken in March versus July 2002 and from sediment versus water. Plasmids were isolated from selected strains of the arsenite- and mercury-resistant organisms and were transformed into Escherichia coli XL1-Blue MRF'. Acquisition of the resistance phenotypes by the new host showed that these resistance genes were carried on the plasmids. Mercury resistance was found to be encoded on a conjugative plasmid. Despite the low incidence of resistant isolates, the six playa lakes and three rivers that were sampled in this study can be considered a reservoir for antimicrobial resistance genes.

Aeromonas infection of the hepatobiliary system: report of 15 cases and review of the literature

Aeromonas species cause both intestinal and extraintestinal disease. We reviewed hospital laboratory and medical records to identify patients with Aeromonas infection of the hepatobiliary or pancreatic system. Analysis of data from our hospital, as well as a review of the published literature, yielded a total of 41 episodes in 39 patients, and the features of these episodes are described. The most common manifestation of Aeromonas hepatobiliary infection among all reported cases was cholangitis (29 of 41 episodes). The majority of infections in our hospital occurred in patients with underlying immunosuppression or malignancy (13 of 15 patients), including 4 liver transplant recipients, and nosocomial infection was not infrequent (8 of 17 episodes). Infection occurred most commonly in patients with obstruction of the biliary tract due to stones, tumor, or stricture and was associated with a relatively high mortality rate (11.8%). Antibiotic susceptibility testing revealed that gentamicin, imipenem, and ciprofloxacin had the highest activity against the Aeromonas species isolated.