Aeromonas veronii biovar veronii septicaemia and acute suppurative cholangitis in a patient with hepatitis B

Aeromonas veronii-associated endogenous endophthalmitis: a case report

BACKGROUND

Aeromonas veronii is a very rare and highly pathogenic microorganism. We investigate the clinical characteristics and significance of endogenous endophthalmitis caused by Aeromonas veronii in our patient.

CASE PRESENTATION

A 30-year-old Asian women with systemic lupus erythematosus, uremia, and hypertension developed acute infectious endophthalmitis caused by Aeromonas veronii. After emergency vitrectomy and antibiotic therapy, the clinical condition worsened requiring enucleation.

CONCLUSIONS

Aeromonas veronii can cause infection in the human eye, which can manifest as acute endophthalmitis. Early diagnosis and targeted therapy are important for successful treatment.

Lp-pPG-611.1-LPS as an immune enhancer provides effective protection against Aeromonas veronii infection in Carassius auratus

Aeromonas veronii (A. veronii) is an important zoonotic pathogen that causes substantial economic losses in aquaculture. In this study, we aimed to develop a safe and effective immune enhancer to protect Carassius auratus (C. auratus) from A. veronii infections. With recognized safety, lactic acid bacteria are used as antigen delivery vehicles to present antigens. Lipopolysaccharide (LPS), a protective antigen, induces immune responses in animals. Therefore, we created recombinant Lactobacillus plantarum (L. plantarum) with surface-displayed LPS of A. veronii TH0426 and tested its effects on immune responses in C. auratus. The results showed that recombinant L. plantarum Lp-pPG-611.1-LPS, as an immune enhancer, could improve the innate and adaptive immune responses of C. auratus when it was added to the diet of C. auratus. The challenge test showed that the survival rate of C. auratus fed with L. plantarum Lp-pPG-611.1-LPS was higher than that of the control groups, indicating that the recombinant L. plantarum Lp-pPG-611.1-LPS increased the resistance of C. auratus to A. veronii infection. The present results provide a theoretical basis for the development of recombinant L. plantarum Lp-pPG-611.1-LPS as an immune enhancer in aquaculture.

Characterizing a subtropical hypereutrophic lake: From physicochemical variables to shotgun metagenomic data

Lake Cajititlán is a subtropical and endorheic lake, which is heavily impacted by nutrient pollution. Agricultural runoff and poorly treated wastewater have entered this reservoir at alarming rates during past rainy seasons, causing the cultural eutrophication of this body of water and resulting in several massive fish kill events. In this study, shotgun metagenomic sequencing was used to examine the taxonomic and functional structure of microbial communities in Lake Cajititlán during the rainy season. Several water quality features and their interactions with microbial communities were also assessed to identify the major factors affecting the water quality and biota, specifically fish species. According to current water quality regulations, most of the physicochemical variables analyzed (dissolved oxygen, pH, Secchi disk, NH4+, NO3−, blue-green algae, total phosphorus, and chlorophyll-a) were outside of the permissible limits. Planktothrix agardhii and Microcystis aeruginosa were the most abundant phytoplankton species, and the dominant bacterial genera were Pseudomonas, Streptomyces, and Flavobacterium, with Pseudomonas fluorescens, Stenotrophomonas maltophilia, and Aeromonas veronii representing the most abundant bacterial species. All of these microorganisms have been reported to be potentially harmful to fish, and the latter three (P. fluorescens, S. maltophilia, A. veronii) also contain genes associated with pathogenicity in fish mortality (fur, luxS, aer, act, aha, exu, lip, ser). Genetic evidence from the microbial communities analyzed herein reveals that anthropogenic sources of nutrients in the lake altered genes involved in nitrogen, phosphorus, sulfur, and carbon metabolism, mainly at the beginning of the rainy season. These findings suggest that abiotic factors influence the structure of the microbial communities, along with the major biogeochemical cycles of Lake Cajititlán, resulting in temporal variations and an excess of microorganisms that can thrive in high-nutrient and low-oxygen environments. After reviewing the literature, this appears to be the first study that focuses on characterizing the water quality of a subtropical hypereutrophic lake through associations between physicochemical variables and shotgun metagenomic data. In addition, there are few studies that have coupled the metabolism of aquatic ecosystems with nutrient cycles.

Comparative genomics analysis of strains from diverse sources reveals the evolutionary relationship of Aeromonas veronii

Aeromonas veronii (A. veronii, AV) strains are emerging zoonotic and aquatic pathogens, yet we know very little about their genomics. This study aims to utilize comparative genomics to investigate the intraspecific genetic diversity, differences in virulence factors and evolutionary mechanisms of A. veronii strains from diverse sources and to fundamentally demonstrate their pathogenic mechanisms. We conducted comparative genomics analysis of 39 A. veronii strains from different sources and found that 1993 core genes are shared by these strains and that these shared core genes may be necessary to maintain the basic characteristics of A. veronii. Additionally, phylogenetic relationship analysis based on these shared genes revealed that a distant relationship between the AMC34 strain and the other 38 strains but that, the genetic relationship among the 38 strains is relatively close, indicating that AMC34 may not belong to A. veronii. Furthermore, analysis of shared core genes and average nucleotide identity (ANI) values showed no obvious correlation with the location of A. veronii isolation and genetic relationship. Our research indicates the evolutionary mechanism of A. veronii from different sources and provides new insights for a deeper understanding of its pathogenic mechanism.

Network-based analysis of virulence factors for uncovering Aeromonas veronii pathogenesis

BACKGROUND

Aeromonas veronii is a bacterial pathogen in aquaculture, which produces virulence factors to enable it colonize and evade host immune defense. Given that experimental verification of virulence factors is time-consuming and laborious, few virulence factors have been characterized. Moreover, most studies have only focused on single virulence factors, resulting in biased interpretation of the pathogenesis of A. veronii.

RESULTS

In this study, a PPI network at genome-wide scale for A. veronii was first constructed followed by prediction and mapping of virulence factors on the network. When topological characteristics were analyzed, the virulence factors had higher degree and betweenness centrality than other proteins in the network. In particular, the virulence factors tended to interact with each other and were enriched in two network modules. One of the modules mainly consisted of histidine kinases, response regulators, diguanylate cyclases and phosphodiesterases, which play important roles in two-component regulatory systems and the synthesis and degradation of cyclic-diGMP. Construction of the interspecies PPI network between A. veronii and its host Oreochromis niloticus revealed that the virulence factors interacted with homologous proteins in the host. Finally, the structures and interacting sites of the virulence factors during interaction with host proteins were predicted.

CONCLUSIONS

The findings here indicate that the virulence factors probably regulate the virulence of A. veronii by involving in signal transduction pathway and manipulate host biological processes by mimicking and binding competitively to host proteins. Our results give more insight into the pathogenesis of A. veronii and provides important information for designing targeted antibacterial drugs.

Comparative genomic analysis of different virulence strains reveals reasons for the increased virulence of Aeromonas veronii

Aeromonas veronii is an important zoonotic and aquatic agent. More and more cases have shown that it has caused huge economic losses in the aquaculture industry in addition to threatening human health. But the reasons for the increasing virulence of A. veronii are still unclear. In order to further understand the reasons for the increased virulence of A. veronii, we conducted a comparative analysis of the genomes of A. veronii with different virulence. The analysis revealed that there are multiple virulence factors, such as those related to fimbriae, flagella, toxins, iron ion uptake systems and type II, type III and type VI secretion systems in the virulent strain TH0426 genome. And comparative analysis showed that there were two complete type III secretion systems (API1 and API2), of which the API2 and iron ion transport system were unique to the TH0426 strain. In addition, TH0426 strain also has unique functional gene clusters, which may play important roles in terms of resisting infection, adapting to different environments and genetic evolution. These particular virulence factors and gene clusters may be the important reasons for the increased virulence. These insights will provide a reference for the study of the pathogenesis of A. veronii.

Comparative proteomic analysis reveals novel potential virulence factors of Aeromonas veronii

Aeromonas veronii is an important zoonotic and aquatic pathogen. An increasing number of reports indicate that it has caused substantial economic losses in the aquaculture industry, in addition to threatening human health. However, little is known about its pathogenesis. Exploration of new virulence factors of A. veronii would be helpful for further understanding its pathogenesis. Hence, we comparatively analyzed the proteomes of virulent, attenuated, and avirulent strains of A. veronii using tandem mass tag (TMT) protein labeling and found numerous proteins either up- or downregulated in the virulent strain. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that these differentially expressed proteins (DEPs) were involved mainly in pathways associated with bacterial chemotaxis and microbial metabolism in diverse environments. Furthermore, the expression levels of lysine decarboxylase, endoribonuclease, maltoporin, pullulanase, and aerolysin were positively correlated with the virulence of the strains, suggesting that their function may be closely related to the virulence of A. veronii. The results of qRT-PCR and multiple reaction monitoring for some DEPs were consistent with the results of TMT protein labeling. These results suggest that these DEPs may be novel potential virulence factors and will help to further understand the pathogenesis of A. veronii.

Aeromonas veronii Infection in Commercial Freshwater Fish: A Potential Threat to Public Health

Aeromonas veronii is an important pathogen causing freshwater fish sepsis and ulcer syndrome. An increasing number of cases have demonstrated its significance as an aquatic zoonotic agent. The purpose of this study was to ensure the safety of freshwater products by evaluating the infection status of edible freshwater fish. In this experiment, we isolated A. veronii from several species of apparently healthy freshwater fish, including Carassius auratus, Cyprinus carpio, Ctenopharyngodon idella, and Silurus asotus. A. veronii was identified through bacterial staining, culture characteristics, and 16S rDNA gene sequence. In addition, polymerase chain reaction (PCR) was used to investigate the distribution of seven major virulence genes, including aerolysin (aer: 88.51%), cytotoxic enterotoxin (act: 71.26%), serine proteinase (ser: 54.02%), adhesin (Aha: 40.23%), phospholipase (lip: 45.98%), nuclease (exu: 51.72%), and quorum sensing-controlled virulence factor (LuxS: 59.77%). In total, 496 strains of Aeromonas were isolated, including 87 strains of A. veronii. The isolates of A. veronii were Gram-negative, rod-shaped bacteria, and the colonies are yellow on Rimler-Shotts (RS) medium and showed greater than 99% homology with A. veronii ATCC35624 according to analyses of the 16S rDNA sequence. Nearly 50% of the A. veronii isolates carried at least four or more virulence genes, 25% of the isolates carried at least five types of virulence genes, and 59.77% isolates carried the LuxS gene, and the isolates carrying more virulence genes were found to be more virulent. These results are of great significance for further improving the food safety assessment of freshwater aquatic products.

Structural and Serological Studies of the O6-Related Antigen of Aeromonas veronii bv. sobria Strain K557 Isolated from Cyprinus carpio on a Polish Fish Farm, which Contains L-perosamine (4-amino-4,6-dideoxy-L-mannose), a Unique Sugar Characteristic for Aeromonas Serogroup O6

Amongst Aeromonas spp. strains that are pathogenic to fish in Polish aquacultures, serogroup O6 was one of the five most commonly identified immunotypes especially among carp isolates. Here, we report immunochemical studies of the lipopolysaccharide (LPS) including the O-specific polysaccharide (O-antigen) of A. veronii bv. sobria strain K557, serogroup O6, isolated from a common carp during an outbreak of motile aeromonad septicemia (MAS) on a Polish fish farm. The O-polysaccharide was obtained by mild acid degradation of the LPS and studied by chemical analyses, mass spectrometry, and ¹H and ¹³C NMR spectroscopy. It was revealed that the O-antigen was composed of two O-polysaccharides, both containing a unique sugar 4-amino-4,6-dideoxy-l-mannose (N-acetyl-l-perosamine, l-Rhap4NAc). The following structures of the O-polysaccharides (O-PS 1 and O-PS 2) were established: O-PS 1: →2)-α-l-Rhap4NAc-(1→; O-PS 2: →2)-α-l-Rhap4NAc-(1→3)-α-l-Rhap4NAc-(1→3)-α-l-Rhap4NAc-(1→. Western blotting and an enzyme-linked immunosorbent assay (ELISA) showed that the cross-reactivity between the LPS of A. veronii bv. sobria K557 and the A. hydrophila JCM 3968 O6 antiserum, and vice versa, is caused by the occurrence of common α-l-Rhap4NAc-(1→2)-α-l-Rhap4NAc and α-l-Rhap4NAc-(1→3)-α-l-Rhap4NAc disaccharides, whereas an additional →4)-α-d-GalpNAc-associated epitope defines the specificity of the O6 reference antiserum. Investigations of the serological and structural similarities and differences in the O-antigens provide knowledge of the immunospecificity of Aeromonas bacteria and are relevant in epidemiological studies and for the elucidation of the routes of transmission and relationships with pathogenicity.

Leech (Myzobdella lugubris) infestations in largemouth bass (Micropterus salmoides) in Back Bay, Virginia, USA

Back Bay is an oligohaline, coastal bay in southeast Virginia, USA. Since 2004, leeches have been observed in the oral cavities of largemouth bass (Micropterus salmoides) in this body of water. Leeches (Myzobdella lugubris) have previously been documented in the oral cavities of largemouth bass in the Currituck Sound, which is confluent with Back Bay on its southern border. Supplemental stocking of largemouth bass in Back Bay since 2009 has resulted in an increasing population; however, concern exists that leech infestation may be negatively affecting health of larger fish, which are still less abundant than expected. Despite the wide distribution of this leech, there is little available literature regarding its health impacts on hosts. In this study, we examine potential impacts of oral leech infestations on stress markers and haematological parameters of largemouth bass in Back Bay. No significant changes in plasma glucose or cortisol were observed between leech-infested and uninfested fish, and haematological parameters were not significantly different between the groups. Further, there was no evidence of systemic infections associated with leech infestation.

Maltoporin (LamB protein) contributes to the virulence and adhesion of Aeromonas veronii TH0426

Aeromonas veronii is one of the main pathogens causing freshwater fish sepsis and ulcer syndrome. More and more cases have shown that it has become an important zoonotic and aquatic agent. In this study, a A. veronii TH0426 mutant strain (ΔlamB) with an in-frame deletion removed nucleotides 10-1,296 of the lamB gene was firstly constructed to investigate its functions. The results showed that the LD₅₀ value of the mutant ΔlamB to zebrafish and mice was 13.7-fold and 5.6-fold higher than those of the wild-type strain, respectively. The toxicity of wild-type strain to EPC cells was 2.1-fold and threefold higher than those of ∆lamB when infected for 1 and 2 hr. Furthermore, the ability of biofilm formation and the adhesion and invasion to EPC cells of ∆lamB significantly decreased for 5.6-fold and 1.8-fold separately. In addition, motility detection result indicated that ∆lamB lost the swimming ability. The results of flagellar staining and TEM demonstrated that the flagella of ∆lamB were shed. In general, the deletion of lamB gene caused a significant decrease in the virulence and adhesion of A. veronii TH0426, and it can be known that the lamB gene of A. veronii plays a crucial role in the pathogenesis.

Winter kill in intensively stocked channel catfish (Ictalurus punctatus): Coinfection with Aeromonas veronii, Streptococcus parauberis and Shewanella putrefaciens

Unusual persistent natural mortality occurred in a floating in-pond raceway system intensively stocked with channel and hybrid catfish beginning in early November 2016 up until March 2017. The temperature during the period of outbreak ranged from 7.2 to 23.7°C. Gross examination of freshly dead and moribund fish revealed pale gills, slight abdominal distension and swollen inflamed vents. Comprehensive necropsy of 20 fish demonstrated vast amounts of bloody ascitic fluid in the coelomic cavity, visceral congestion, splenomegaly and pale friable livers but macroscopically normal kidneys, suggesting systemic bacterial infection. Bacterial cultures were initiated from skin, gills and major internal organs. Following incubation, a mixture of three bacterial colony phenotypes was observed on agar plates. Presumptive biochemical characterization of the isolates followed by 16S-rRNA sequence analysis resulted in the identification of Aeromonas veronii, Streptococcus parauberis and Shewanella putrefaciens. Channel catfish juveniles were experimentally infected with the recovered isolates to fulfil Koch's postulates. Moreover, an antibiogram was used to evaluate the susceptibility of the isolates to antimicrobial drugs approved for use in aquaculture. Aquaflor was used successfully for treatment. Here, we report bacterial coinfection lead by A. veronii and the first identification of S. parauberis and S. putrefaciens from cultured catfish in North America.

Structural studies of the lipopolysaccharide from the fish pathogen Aeromonas veronii strain Bs19, serotype O16

Chemical analyses, mass spectrometry, and NMR spectroscopy were applied to study the structure of the lipopolysaccharide (LPS) isolated from Aeromonas veronii strain Bs19, serotype O16. ESI-MS revealed that the most abundant LPS glycoforms have tetra-acylated or hexa-acylated lipid A species, consisting of a bisphosphorylated GlcN disaccharide with an AraN residue as a non-stoichiometric substituent, and a core oligosaccharide composed of Hep₅Hex₃HexN₁Kdo₁P₁. Sugar and methylation analysis together with 1D and 2D ¹H and ¹³C NMR spectroscopy were the main methods used, and revealed that the O-specific polysaccharide (OPS) of A. veronii Bs19 was built up of tetrasaccharide repeating units with the structure: →4)-α-d-Quip3NAc-(1→3)-α-l-Rhap-(1→4)-β-d-Galp-(1→3)-α-d-GalpNAc-(1→. This composition was confirmed by mass spectrometry. The charge-deconvoluted ESI FT-ICR MS recorded for the LPS preparations identified mass peaks of SR- and R-form LPS species, that differed by Δm = 698.27 u, a value corresponding to the calculated molecular mass of one OPS repeating unit (6dHexNAc6dHexHexHexNAc-H₂O). Moreover, unspecific fragmentation spectra confirmed the sequence of the sugar residues in the OPS and allowed to assume that the elucidated structure also represented the biological repeating unit.

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.

Peritonitis caused by Aeromonas species at a hospital in southern Taiwan

OBJECTIVE

This study was conducted to investigate the clinical characteristics of patients with Aeromonas peritonitis, particularly secondary peritonitis.

METHODS

Patients with Aeromonas peritonitis treated between July 2004 and December 2011 were identified from the computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed.

RESULTS

A total of 50 patients with Aeromonas peritonitis were identified. Nine cases were classified as spontaneous bacterial peritonitis, and 41 cases were classified as secondary peritonitis. The most common etiology of secondary peritonitis was acute appendicitis (n=26), followed by small bowel perforation (n=7) and colon perforation (n=6). The patients with spontaneous bacterial peritonitis were more likely to be immunocompromised (p=0.0013) and more frequently had an initial presentation of shock (p=0.0129), an abnormal liver function (p<0.05) and concomitant bacteremia (p=0.0024) than the patients with secondary peritonitis. Although the patients with secondary peritonitis had higher levels of inflammatory parameters, including leukocytes and C-reactive protein, and more frequent polymicrobial infections, their survival outcome rates, such as in-hospital mortality, were significantly lower (p=0.0007). The overall in-hospital mortality rate was 20%, and initial shock was the only independent prognostic factor for mortality (p=0.012).

CONCLUSION

The clinical characteristics, including outcomes, of patients with spontaneous and secondary Aeromonas peritonitis differ. In-hospital mortality is significantly associated with the initial presentation of shock.

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.

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.

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.