Incidence and antimicrobial susceptibility fingerprints of Plesiomonas shigelliodes isolates in water samples collected from some freshwater resources in Southwest Nigeria.

Plesiomonas shigelloides, is an emerging and significant enteric pathogen in water having implication in both localised and gastrointestinal infections with characteristic of displaying high resistance against commonly used antibiotics. This study evaluated the prevalence of Plesiomonas shigelloides and their antibiogram fingerprints in water sample collected from four rivers in South-western Nigeria. In all, 148 presumptive Plesiomonas shigelloides isolates was recovered from the rivers out of which 66 (44.6%) were confirmed positive for the organism using polymerase chain reaction techniques. Confirmed isolates were evaluated for their antibiogram profiles against a panel of 20 antimicrobials using the disc diffusion method and further screened for relevant antibiotic resistance genes. Resistance of the isolates against the antimicrobials followed the order: sulphamethoxazole (100%), erythromycin (93%), ampicillin (90%), cephalotin (82%), streptomycin (64%), and chloramphenicol (58%), amoxicillin (53%), cefotaxime (50%), tetracycline (49%), neomycin (38%) and trimethoprim + sulphamethoxazole (38%). Conversely, all the isolates were susceptible against netilmicin, and susceptibility against the other antibiotics follows the order: meropenem (94%), gentamicin (88%), imipenem (79%), amikacin (70%), ciprofloxacin (70%), norfloxacin (59%), trimethoprim (56%) and ceftazidine (56%). The multiple antibiotic resistance indices of the organism were higher than the accepted threshold of 0.2. The incidence of 11 antimicrobial resistance determinants were obtained as follows: [sulphonamides; (sulI (18%), sulII (20%), dfr1 (70%), dfr(18) (5%)), [beta-lactams; (ampC 37%)], [tetracyclines; (tetA (78%), tetE (57%)], [phenicols; (catII (16%), cmlA1 (11%)] and [aminoglycosides; (aphA2 (36%) and strA (67%)]. Pearson chi-square exact test revealed positive associations among tetA, tetE, sullI and catII and tetA genes. To the best of our knowledge, this is the first report on the incidence and antibiogram fingerprint of P. shigelloides in these freshwater resources and we conclude that these rivers are important reservoirs of multiple antimicrobial resistant biotypes of this organism, and consequently a threat to public health.

Aeromonas and Plesiomonas species from scarlet ibis (Eudocimus ruber) and their environment: monitoring antimicrobial susceptibility and virulence.

The present study aimed at evaluating the role of captive scarlet ibises (Eudocimus ruber) and their environment as reservoirs of Aeromonas spp. and Plesiomonas spp., and analyzing the in vitro antimicrobial susceptibility and virulence of the recovered bacterial isolates. Thus, non-lactose and weak-lactose fermenting, oxidase positive Gram-negative bacilli were recovered from cloacal samples (n = 30) of scarlet ibises kept in a conservational facility and from water samples (n = 30) from their environment. Then, the antimicrobial susceptibility, hemolytic activity and biofilm production of the recovered Aeromonas spp. and Plesiomonas shigelloides strains were assessed. In addition, the virulence-associated genes of Aeromonas spp. were detected. Ten Aeromonas veronii bv. sobria, 2 Aeromonas hydrophila complex and 10 P. shigelloides were recovered. Intermediate susceptibility to piperacillin-tazobactam and cefepime was observed in 2 Aeromonas spp. and 1 P. shigelloides, respectively, and resistance to gentamicin was observed in 4 P. shigelloides. The automated susceptibility analysis revealed resistance to piperacillin-tazobactam and meropenem among Aeromonas spp. and intermediate susceptibility to gentamicin among P. shigelloides. All Aeromonas isolates presented hemolytic activity, while 3 P. shigelloides were non-hemolytic. All Aeromonas spp. and 3/10 P. shigelloides were biofilm-producers, at 28 °C, while 10 Aeromonas spp. and 6/10 P. shigelloides produced biofilms, at 37 °C. The most prevalent virulence genes of Aeromonas spp. were asa1 and ascV. Scarlet ibises and their environment harbour potentially pathogenic bacteria, thus requiring monitoring and measures to prevent contamination of humans and other animals.

Inhibitory Effects of Gallic Acid Isolated from Caesalpinia mimosoides Lamk on Cholangiocarcinoma Cell Lines and Foodborne Pathogenic Bacteria.

Gallic acid was isolated from Caesalpinia mimosoides Lamk and the structure s identified based on spectroscopic analysis and comparison with authentic compound. In this study we compared the ability of natural gallic acid (nGA) and commercial gallic acid (cGA) to inhibit the proliferation of cholangiocarcinoma cell lines (M213, M214) and foodborne pathogenic bacteria (Salmonella spp. and Plesiomonas shigelloides). Both nGA and cGA had the same inhibitory effects on cell proliferation by inducing apoptosis of cholangiocarcinoma cell lines. In addition, nGA inhibited growth of foodborne pathogenic bacteria in the same manner as cGA. Our results suggest that nGA from Caesalpinia mimosoides Lamk is a potential anticancer and antibacterial compound. However, in vivo studies are needed to elucidate the specific mechanisms involved.

PREVALENCE, BIOCHEMICAL CHARACTERISTICS, AND ANTIBIOTIC SUSCEPTIBILITY OF AEROMONADS, VIBRIOS, AND PLESIOMONADS ISOLATED FROM DIFFERENT SOURCES AT A ZOO.

Aeromonas spp., Vibrio parahaemolyticus , and Plesiomonas shigelloides are commonly implicated in foodborne and waterborne diarrheal illnesses of humans and other animals. The present study assessed the prevalence, biochemical characteristics, and antibiotic susceptibility of Aeromonas spp., V. parahaemolyticus , and P. shigelloides by analyzing samples from 729 sources at a zoo, including animal feces (n=607), watering facilities (n=104), and pond water samples (n=18). Of the 729 samples collected, 40 (5.5%) contained one of these four species of bacteria: A. hydrophila (n=16; 2.2%), A. sobria (n=12; 1.6%), V. parahaemolyticus (n=10; 1.4%), and P. shigelloides (n=2; 0.3%). The 16 isolates of A. hydrophila came from three fecal samples, eight watering facilities, and five pond water samples. The 12 isolates of A. sobria came from four fecal samples, three watering facilities, and five pond water samples. The 10 isolates of V. parahaemolyticus came from one fecal sample and nine watering facilities. The two isolates of P. shigelloides came from one watering facility and one pond water sample. Of the 40 isolates, 16 (40.0%), 21 (52.5%), and three (7.5%) originated from mammals, birds, and reptiles, respectively. All isolates tested positive for NO3, tryptophan, p-nitrophenyl-ß-D-galactopyranoside, glucose assimilation, N-acetyl-glucosamine, maltose, gluconate, malate, and oxidase. Aeromonas spp. and V. parahaemolyticus exhibited similar biochemical characteristics, whereas P. shigelloides exhibited distinct fermentation characteristics. All the isolated strains exhibited hemolytic activity; variable results of DNase, protease, and Congo red uptake tests; and resistance to ampicillin, bacitracin, novobiocin, penicillin, and vancomycin. All the strains were sensitive to amikacin, chloramphenicol, colistin, gentamicin, kanamycin, norfloxacin, and trimethoprim-sulfadimethoxazole. Because of the high proportion of asymptomatic carriers of these potentially pathogenic bacteria and their wide distribution, consistent monitoring of food and water sources is necessary to prevent disease outbreaks.

[Identification and pathological observation of a pathogenic Plesiomonas shigelloides strain isolated from cultured tilapia (Oreochromis niloticus)].

OBJECTIVE: A mass mortality of tilapia broke out in an aquaculture farm in Panyu, Guangdong Province in May, 2013. Affected fish showed blackening of body color, haemorrhageing on surface, scales shedding, fin rotting, and the presence of yellow liver, dark red spleen, enlarged gallbladder and ascitic fluid in the abdominal cavity. The purpose of this research was isolating and identifying the pathogen. METHODS: We isolated a suspicious bacteria strain PYS1 from diseased fish with significant pathological signs. The homology of 16S rRNA gene sequence of strain PYS1 and its morphological, cultural, and physical and chemical characteristics were studied for its identification. Its pathogenicity was investigated by recursive infection experiment and histopathological study. Its effective medicines was screened by antibiotic sensitive test. RESULTS: The results showed that strain PYS1 was Plesiomonas shigelloides clustered with P. shigelloides strains isolated from other fishes in the molecular phylogenetic tree of 16S rRNA gene sequences. Strain PYS1 was multiple drug resistant and only sensitive to a small part of 31 tested antibiotics (e.g., ceftriaxone, cefaclor, cefazolin, etc.). The symptoms of tilapia (O. niloticus) artificially infected with strain PYS1 were similar with natural infected fish. The half lethal dose (LD50) of strain PYS1 to tilapia was 1.425 x 10(8) CFU per fish. Paraffin sections showed intestine, liver, spleen, kidney and heart tissue injury caused by the strain. CONCLUSION: Our study demonstrated that P. shigelloides was the pathogen of cultured tilapia in the aquaculture farm and first reported its bacterial pathogenicity on Nile tilapia.

Isolation and antimicrobial susceptibility of Plesiomonas shigelloides from great cormorants (Phalacrocorax carbo hanedae) in Gifu and Shiga Prefectures, Japan.

Plesiomonas shigelloides is a causal agent of gastroenteritis, sepsis and meningitis in humans. We examined the prevalence of P. shigelloides among great cormorants (Phalacrocorax carbo hanedae) in Japan and the antimicrobial susceptibility of isolates. P. shigelloides was isolated from 33 (47.8%) of 69 fecal samples from great cormorants in 2014. All 33 isolates were subjected to antimicrobial susceptibility testing using broth microdilution methods, which showed resistance to ampicillin (31 isolates, 93.9%), tetracycline (two isolates, 6.1%) and trimethoprim (one isolate, 3.0%). The high prevalence of P. shigelloides in the great cormorants implicates the possible microbiological risk to public health.

[Isolation and identification of a pathogenic Plesiomonas shigelloides from diseased grass carp].

OBJECTIVE: The aim of this study is to identify strain JX-09 and confirmed that the strain is the pathogen of diseased grass carp (Ctenopharyngodon idellus). METHODS: A pathogenic strain JX-09 was isolated from the diseased grass carp. The strain was identified based on physiological and biochemical characteristics, and the sequence analysis of 16S rRNA. Virulence of strain JX-09 to healthy grass carp was also tested. Furthermore, drug sensitivity was detected RESULTS: Strain JX-09 was identified as Plesiomonas shigelloides by with Kirby-Bauer's agar diffusion method. biochemical analysis and molecular biology. The P. shigelloides strain was re-isolated from the artificial infected grass carp, and the LD50 was about 6.4 x 10(4) cfu/g. Drug sensitive tests showed that strain JX-09 was susceptible to aztreonam, cefazolin, cephalothin and ceftriaxone, and resistant to kanamycin, medicamycin, vancomycin and piperacillin. CONCLUSION: Strain JX-09 was the pathogen of grass carp with muscle erosive disease. To the best of our knowledge, this is the first report that P. shigelloides as the pathogenic strain of grass carp.

Plesiomonas shigelloides infection in Southeast China.

BACKGROUND: Plesiomonas shigelloides can cause gastroenteritis and extra-intestinal diseases in humans. However, the prevalence of P. shigelloides infections has not been investigated in China. METHODS: Consecutive fecal specimens from outpatients with acute diarrhea and non-diarrheal patients at nine sentinel hospitals in southeast China were collected from March 2010 to May 2012. Bacterial pathogens were detected by culture, and P. shigelloides isolates were subjected to antimicrobial susceptibility testing. We also retrospectively reviewed the hospital microbiology laboratory and infection-control databases for all P. shigelloides isolates identified from 2001-2012 at our institution in addition to data on the patients' clinical and demographic characteristics. RESULTS: A total of 3,536 outpatients with acute diarrhea were enrolled in the study. P. shigelloides was isolated from 104 (2.9%) patients and accounted for 7.3% of bacterial isolates. Single-pathogen infections with P. shigelloides were present in 76 (73.1%) patients. No strain of P. shigelloides was isolated from the 478 non-diarrheal patients. Based on 444,684 nonfecal specimens, eight patients developed P. shigelloides-related extra-intestinal infections over the 12-year period. All eight patients had underlying diseases, including four with biliary tract diseases and three with liver diseases. Six cases were classified as nosocomial, and five cases were polymicrobial. P. shigelloides was sensitive to most antimicrobial drugs, except ampicillin. CONCLUSIONS: In southeast China, P. shigelloides has significant clinical relevance, although the isolation rate is low.

[Identification and drug sensitivity of a Plesiomonas shigelloides isolated from diseased sturgeons].

OBJECTIVE: In 2012, the cumulative mortality of farmed sturgeons in Beijing was almost 60% with various symptoms, including the reddening of the anus with yellow exudation, ascities in the peritoneal cavity, petechial haemorrhages in liver and internal muscle wall, and the swollen spleen. METHODS: We isolated the pathogen from the dying sturgeons with significant pathological signs, and then analyzed its morphological, physiological and biochemical characteristics, taxonomic status, and drug sensitivity. Moreover, the pathogenic characteristic of presumptive pathogens was identified by artificial infection. RESULTS: The 16S rDNA sequence of the pathogen was more than 99% homology with that of Plesiomonas shigelloides, suggesting that the pathogen was P. shigelloides, which was also demonstrated by the results of biochemical tests. The LD50 of the pathogen to sturgeon was 1.0 x 10(5.8) CFU/mL, and it also can cause liver, kidey and spleen to lesions. There were no activities of amylase, caseinase, lipase, gelatinase and haemolysis of extracellular products of P. shigelloides, and its toxicity might be from endotoxin. In addition, the bacterium was specific sensitive to enrofloxacin, doxycyline hyclate, florfenicol and thiamphenicol with MIC less than 2 microg/mL. CONCLUSION: P. shigelloides was the main pathogen to cultured sturgeons in Beijing area, and enrofloxacin, doxycyline hyclate and florfenicol can be used against the disease.

[Virulence factors and in vitro susceptibility of Plesiomonas shigelloides isolated from diarrhea episodes in Cuba]. / Caracterización de factores de virulencia y susceptibilidad antimicrobiana en cepas de Plesiomonas shigelloides aisladas de pacientes con diarrea aguda en Cuba.

Acute diarrhea is still one of the main causes of disease in developing countries. At the National Reference Laboratory for Acute Diarrhoeal Diseases, of the "Pedro Kourí" Tropical Medicine Institute, 54 Plesiomonas shigelloides strains were serotyped. As a result, the circulation of four new serotypes (O20:H2, 056:H18, 071 :H31,081 :H22) was detected. The most common antigenic variant was 094:H3. In addition, the susceptibility pattern to 21 antimicrobial agents (AA) was studied. Highest percentages of resistance were observed to ampicillin (77.7%), tetracycline (29.2%), and erythromycin (18.5%) while, to all other AA the resistance percentages were under 33%. There was no evidence of association between the serotypes and the multi-resistance patterns present in the strains under study. The frequency of virulence factors was determined: 21.15% of the strains turned out to be ss-haemolytic; 73.7% showed the presence of biofilm and 92.31% were hydrophobic. In 17.3% of the strains, the three virulence factors analysed were present. When establishing the relationship among the different virulence factors and the serotypes of the strains through cross reaction with the Shigella genus, there was evidence that 93.3% of the strains showed at least one of the virulence factors studied. Likewise, at least one of the virulence factors analysed was present in 90.9% of the multi-resistant strains.

Caracterización de factores de virulencia y susceptibilidad antimicrobiana en cepas de Plesiomonas shigelloides aisladas de pacientes con diarrea aguda en Cuba / Virulence factors and in vitro susceptibility of Plesiomonas shigelloides isolated from diarrhea episodes in Cuba

Acute diarrhea is still one of the main causes of disease in developing countries. At the National Reference Laboratory for Acute Diarrhoeal Diseases, of the "Pedro Kourí" Tropical Medicine Institute, 54 Plesiomonas shigelloides strains were serotyped. As a result, the circulation of four new serotypes (O20:H2, 056:H18, 071 :H31,081 :H22) was detected. The most common antigenic variant was 094:H3. In addition, the susceptibility pattern to 21 antimicrobial agents (AA) was studied. Highest percentages of resistance were observed to ampicillin (77.7 percent), tetracycline (29.2 percent), and erythromycin (18.5 percent) while, to all other AA the resistance percentages were under 33 percent. There was no evidence of association between the serotypes and the multi-resistance patterns present in the strains under study. The frequency of virulence factors was determined: 21.15 percent of the strains turned out to be ß-haemolytic; 73.7 percent showed the presence of biofilm and 92.31 percent were hydrophobic. In 17.3 percent of the strains, the three virulence factors analysed were present. When establishing the relationship among the different virulence factors and the serotypes of the strains through cross reaction with the Shigella genus, there was evidence that 93.3 percent of the strains showed at least one of the virulence factors studied. Likewise, at least one of the virulence factors analysed was present in 90.9 percent of the multi-resistant strains.

La diarrea aguda (DA) continúa siendo una de las principales causas de consulta en los países en vías de desarrollo. Un agente de baja prevalencia en DA es Plesiomonas shigelloides. En el Laboratorio Nacional de Referencia de Enfermedad Diarreica Aguda del IPK se estudiaron 54 cepas conservadas de P. shigelloides. Se determinó el serotipo detectándose por primera vez en el país la circulación de cuatro serotipos (O20:H2, 056:H18, 07LH31, 08LH22) así como la vanante antigénica de mayor prevalencia (094:H3). Se estudió el comportamiento de las cepas frente a 21 agentes antimicrobianos obteniéndose los mayores porcentajes de resistencia frente a ampicilina (77,7 por ciento), tetraciclina (29,2 por cientoo) y eritromicina (18,5 por ciento) mientras que para el resto se obtuvieron porcentajes de resistencia inferior a 33 por cientoo. No se evidenció asociación entre los serotipos y los patrones de multi-resistencia presentes en las cepas del estudio. Se estudiaron los factores de virulencia: actividad hemolítica, producción de exo-polisacáridos y adherencia a hidrocarburos. El 22,2 por ciento de las cepas resultaron B hemolíticas, 72,2 por cientoo presentó bio-película y 92,31 por ciento fueron hidrofóbicas. El 17,3 por ciento de las cepas presentaron los tres factores de virulencia. Estableciendo una relación entre los factores de virulencia y los serotipos de las cepas con reacción cruzada con el género Shigella se evidenció que 93,3 por cientoo de las cepas presentaron al menos uno de los factores de virulencia. El 90,9 por cientoo de las cepas multi-resistentes presentó al menos uno de ellos.

Analysis of freshwater pathogens: a guide to rational empiric antibiotic coverage.

Fresh water injuries are often contaminated with bacteria that are not typically encountered in other wounds. Their treatment should include empiric administration of appropriate antibiotics. This study identifies the most common pathogens found in the Lake of the Ozarks and their antibiotic sensitivity. Eleven of the twelve lake water samples (92%) had a positive culture result. Sixty-seven percent of lake water samples contained at least two strains of bacteria. Five different bacterial species of gram negative rods were isolated. All isolates were sensitive to Cefotetan, Ceftazidime, Ceftriaxone, Imipenem, Levofloxacin, Tobramycin, and Trimetheprim/sulfa. Antibiotic coverage after traumatic wounds required gram positive coverage. Our study suggests the addition of gram negative coverage for penetrating trauma contaminated by fresh water.

Effect of inoculum density on susceptibility of Plesiomonas shigelloides to cephalosporins.

OBJECTIVES: Resistance of Plesiomonas shigelloides to cephalosporins at higher cell densities has been reported. We investigated whether these inoculum effects are due to the production of beta-lactamases. METHODS: beta-Lactamase production of five P. shigelloides strains was characterized by activity tests, SDS-PAGE and isoelectric focusing. For all strains, MIC values of different cephalosporins were determined by microdilution methodology using inocula of 1 x 10(5) cfu/mL and 1 x 10(6) cfu/mL. Subsequently, the morphology of cells was determined by light microscopy. For one isolate, kill kinetics of cefpodoxime were determined using batch cultures with the lower and higher inocula. RESULTS: Four of five P. shigelloides strains were shown to be beta-lactamase-positive, producing different amounts of constitutively expressed non-inducible enzymes. Inoculum effects for cephalosporin susceptibility were observed for all strains. Examination of cells revealed a very strong filamentation, with filament sizes ranging from 100 microm up to 2 mm. The kill kinetics with cefpodoxime showed similar killing capacities of the antibiotic at both inoculum sizes. CONCLUSIONS: The reported resistance of P. shigelloides to cephalosporins at higher cell densities is not due to an inoculum-dependent regulation of beta-lactamases, but can be explained by the formation of extensive filaments.

Serotypes and anti-microbial susceptibility of Plesiomonas shigelloides isolates from humans, animals and aquatic environments in different countries.

A total of 73 strains of Plesiomonas shigelloides isolated from humans (24 strains) animals (21 strains) and aquatic environment (28 strains) were determined for their O:H serotype and susceptibility to 18 anti-microbial substances and to the vibriostatic agent O/129. Of all strains, 86.3% were typeable by the O and 94.5% by the H anti-sera used. The serotype distribution was heterogeneous within a country and between the countries. Of the 57 different serotypes identified, O11:H2 (2 strains), O22:H3 (4 strains), O35:HH11 (2 strains), O52:H3 (2 strains) and O90:H6 (2 strains) were found among isolates from humans and animals (mainly in cats) in Finland and Cuba, and O23:H1a1b (3 strains) among isolates from environmental sources in Slovak Republic and Italy. Most (93-100%) of all strains were susceptible to all anti-microbials tested but resistant (92-96%) to the broad-spectrum penicillins (ampicillin, mezlocillin). No correlation between anti-microbial resistance patterns and serotypes was found.

The effect of disinfectants on Plesiomonas shigelloides.

The effects of ten commercially available disinfectants on virulence associated properties of Plesiomonas shigelloides were tested. All the disinfectants tested contained quaternary ammonium salts. The majority of the disinfectants when used at subinhibitory concentrations increased surface hydrophobicity as evaluated by bacterial adherence to xylene and decreased bacterial motility in a concentration dependent manner. Disinfectants did not significantly affect lipase activity. However, more than half of the antimicrobials tested increased the resistance of bacteria to hydrogen peroxide. The disinfectants, in a similar manner to antibiotics at concentrations below MIC, interfered with potential virulence factors of Plesiomonas shigelloides.

Some properties of Plesiomonas shigelloides treated with aminoglycosides.

The effect of aminoglycoside antibiotics (amikacin, gentamicin, netilmicin and tobramycin) at sublethal concentrations (sub-MICs) on some properties of Plesiomonas shigelloides strains was evaluated. All agents decreased the bacterial surface hydrophobicity. Amikacin (1/4 of the MIC) and netilmicin (1/4 and 1/8 of the MIC) changed the hydrophobic character of P. shigelloides surface to a hydrophilic one. Treatment of the strains with aminoglycosides decreased also motility, netilmicin being the most effective. No significant changes were found in lipolytic activity of antibiotic-treated strains. In the majority of cases aminoglycosides increased sensitivity of bacteria to hydrogen peroxide. The tested antibiotics did not induce production of short-chained N-acylhomoserine lactones signal molecules. Aminoglycosides at sub-MICs affected important activities of P. shigelloides potentially associated with their virulence in dependence on strain, antibiotic and concentration.

Characteristics of Plesiomonas shigelloides infection in Taiwan.

From January 1999 through December 2000, a total of 111 cases of Plesiomonas shigelloides infections were diagnosed in a medical center of northern Taiwan. The patients ranged in age from 22 days to 72 years. One third (39/111, 35%) of the positive cultures were found in young children (<2 years old). There was no significant difference in the incidence between males (56/111, 50%) and females (55/111, 50%). The peak seasons for the disease were summer (45/111, 41%) and autumn (42/111, 38%). The major clinical presentations in children were diarrhea (66/69, 96%) and fever (38/69, 55%), whereas diarrhea (41/42, 98%) and abdominal pain (30/42, 71%) were the most common presentations in adults. Most adults with P. shigelloides infection visited the emergency room (38/42, 90%) and received empirical antimicrobials (37/42, 88%), whereas children were more likely to be treated as outpatients (53/69, 77%) and inpatients (27/69, 39%). One third (23/69, 33%) of pediatric patients had mixed enteric infection, and 74% (17/23) of them were younger than 2 years. Salmonella species (17/24, 71%), especially group B Salmonella (12/17, 71%), were the most common mixed enteric pathogen. The disease is usually mild and self-limited. Symptomatic management is adequate and antimicrobial therapy is seldom required.

Natural antimicrobial susceptibilities of Plesiomonas shigelloides strains.

The natural susceptibility of 74 Plesiomonas shigelloides strains isolated from humans (n = 50), water (n = 22) and animals (n = 2) to 71 antibiotics was examined. MICs were performed using a microdilution procedure with Mueller-Hinton broth and an inoculum of 1 x 10(6) cfu/mL. Plesiomonas strains were naturally susceptible or naturally susceptible and intermediate to tetracyclines, several aminoglycosides, aminopenicillins in combination with beta-lactamase inhibitors, all cephalosporins except cefoperazone, ceftazidime and cefepime, carbapenems, aztreonam, quinolones, trimethoprim, sulfamethoxazole, azithromycin, chloramphenicol, nitrofurantoin and fosfomycin. Uniform natural resistance was found to all penicillins tested, roxithromycin, clarithromycin, lincosamides, streptogramins, glycopeptides and fusidic acid. Plesiomonas strains were naturally resistant and intermediate to streptomycin, erythromycin and rifampicin. There were two susceptibility patterns to piperacillin/tazobactam, several cephalosporins and aztreonam. In contrast to a previous study with beta-lactam antibiotics, susceptibility testing of non-beta-lactams revealed no alterations of the MICs of most antibiotics, using different inocula and media. A database is described of the natural susceptibility of P. shigelloides strains to a wide range of antibiotics. It can be used for the validation of susceptibility test results of these bacteria.