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Biomedical subjects

A Siitonen

Publications and source records attributed to A Siitonen.

At least 55 records · Page 3Linked to original sources
PubMed2000

Prevalence of diarrheagenic Escherichia coli in finns with or without diarrhea during a round-the-world trip.

The incidence of diarrhea and the prevalence of bacterial enteropathogens, viruses, and parasites in feces of subjects with and without diarrhea were evaluated in 204 Finns traveling round the world (from Finland to China, Malaysia, Australia, Fiji, Chile, and Brazil and back to Finland). Special emphasis was placed on the finding of diarrheagenic Escherichia coli (enterotoxigenic, enteropathogenic, Shiga toxin-producing, and enteroaggregative strains) by PCR from growth on primary culture plates. From the PCR-positive samples, corresponding strains were isolated, confirmed as E. coli, and O serotyped. Of all the subjects, 37% experienced a total of 90 episodes of diarrhea. No adenoviruses or rotaviruses were detected, and findings of parasites were insignificant. In contrast, enteropathogenic bacteria were present in 62% of the 65 diarrheal and in 33% of the 127 nondiarrheal samples (P < 0.001); diarrheagenic E. coli strains were found in 35 and 26% of these, respectively (not statistically significant). As a single pathogen, E. coli was found in 20 and 24% of samples (not significant). Of all diarrheagenic E. coli strains, enteropathogenic strains were the most commonly found independently of the clinical picture of the subjects, whereas Salmonella enterica as a single pathogen was the most common non-E. coli organism found in diarrheal samples. Multiple bacterial pathogens were found 10 times more commonly in diarrheal than in nondiarrheal samples (20 versus 2%; P < 0.001).

Adolescent↗
PubMed1999

Swimming-associated outbreak of Escherichia coli O157:H7.

In 1997 the first outbreak of Escherichia coli O157:H7 infections involving 14 cases occurred in Finland. A case was defined as a resident of Alavus with an episode of diarrhoea between 5 and 17 July 1997, and from whom E. coli O157:H7 was isolated from stool. The investigation included case searching and a population-based case control study. Five primary and eight symptomatic secondary cases of E. coli O157:H7 illness were detected. In the 10 days before the outbreak, all 5 primary patients (aged 3-8 years), but only 6 of 32 population controls from the same age range (Fisher's test, P < 0.001) and 4 of 10 sibling controls (P < 0.05) had visited (but had not necessarily bathed in) a shallow beach popular among young children. Four out of 5 primary cases had remained within 5 m of the beach while swimming and had swallowed lake water compared to 1 of 5 population controls. These analytical epidemiologic findings incriminated fresh lake water as the vehicle of E. coli O157:H7 transmission.

Age Distribution↗
PubMed1999

Ethanol oxidation and acetaldehyde production in vitro by human intestinal strains of Escherichia coli under aerobic, microaerobic, and anaerobic conditions.

BACKGROUND: Many human colonic facultative anaerobic and aerobic bacteria are capable of alcohol dehydrogenase (ADH)-mediated ethanol oxidation. In this bacteriocolonic pathway for ethanol oxidation intracolonic ethanol is first oxidized by bacterial ADHs to acetaldehyde, which is further oxidized by either colonic mucosal or bacterial aldehyde dehydrogenases to acetate. The produced acetaldehyde is a highly toxic and carcinogenic agent. This study was aimed to investigate the ethanol oxidation capability and acetaldehyde formation of Escherichia coli IH 50546 and IH 50817. These intestinal E. coli strains expressed either high (IH 50546) or low (IH 50817) ADH activity. METHODS: Strains were cultured for 48 h on agar plates supplemented with ethanol under aerobic, microaerobic (6% O2), and anaerobic conditions. RESULTS: Under aerobic conditions both E. coli strains oxidized ethanol. The ethanol consumption rates (ECR) were 1.046+/-0.025 mM/h and 0.367+/-0.148 mM/h with IH 50546 and IH 50817, respectively. In the case of IH 50546 this was associated with significant acetaldehyde production (418+/-13 microM), suggesting ADH-mediated ethanol oxidation. Under microaerobic conditions only IH 50546 was able to oxidize ethanol (ECR, 0.498+/-0.074 mM/h) and to produce acetaldehyde (up to 440+/-76 microM) to significant extents. Under anaerobic conditions both strains fermented glucose to ethanol. CONCLUSIONS: This study experimentally shows the potential of certain bacteria representing normal human colonic flora to produce acetaldehyde under various atmospheric conditions that may prevail in different parts of the GI tract. This bacterial adaptation may be an essential feature of the bacteriocolonic pathway to produce toxic and carcinogenic acetaldehyde from either endogenous or exogenous ethanol.

Acetaldehyde↗
PubMed1999

Haemolytic-uraemic syndrome caused by vero toxin-producing Escherichia coli serotype Rough: K-: H49.

The first case of haemolytic-uraemic syndrome (HUS) caused by Vero toxin-producing Escherichia coli (VTEC) which belonged to a novel serotype, Rough: K-: H49, is reported. The case was initially diagnosed as nephropathia epidemica caused by Puumala virus, but the subsequent diagnosis of HUS caused by VTEC was made after bacteriological investigation. The strain isolated fermented sorbitol produced VT2 toxin but not enterohaemolysin, nor did it carry the eaeA gene. In VTEC strains, the O antigen, the eaeA gene and enterohaemolysin production have been characterized as virulence-associated factors and believed to have an effect on pathogenesis of these strains to cause haemorrhagic colitis or HUS. The findings of this study demonstrate that there is a need for further studies to evaluate the pathogenetic mechanism of VTEC and need for easy diagnostic methods exploiting other properties than O157 antigen and non-fermentation of sorbitol to find all VTEC in human infections.

Adult↗
PubMed1999

Increasing fluoroquinolone resistance in salmonella serotypes in Finland during 1995-1997.

Antimicrobial resistance trends were examined for 811 salmonella isolates from humans collected in Finland during 1995-1997. The material was divided into domestic and foreign isolates according to the origin of infection. A total of 2.3% of the 387 domestic and 7.8% of the 424 foreign isolates were quinolone-resistant (P < 0.001). Among the domestic isolates we detected an emergence of ciprofloxacin resistance (MIC > or = 0.25 mg/L) with the proportion of resistant isolates increasing from 0 to 2.2% (P = 0.2). Among the foreign isolates this increase was even more dramatic, from 2.0% to 8.4% (P = 0.037) during the study period.

Anti-Bacterial Agents↗
PubMed1999

Detection of decreased fluoroquinolone susceptibility in Salmonellas and validation of nalidixic acid screening test.

We evaluated 1,010 Salmonella isolates classified as fluoroquinolone susceptible according to the National Committee for Clinical Laboratory Standards guidelines for susceptibility to nalidixic acid and three fluoroquinolones. These isolates were divided into two distinct subpopulations, with the great majority (n = 960) being fully ciprofloxacin susceptible and a minority (n = 50) exhibiting reduced ciprofloxacin susceptibility (MICs ranging between 0.125 and 0.5 microg/ml). The less ciprofloxacin-susceptible isolates were uniformly resistant to nalidixic acid, while only 12 (1.3%) of the fully susceptible isolates were nalidixic acid resistant. A similar association was observed between resistance to nalidixic acid and decreased susceptibility to ofloxacin or norfloxacin. A mutation of the gyrA gene could be demonstrated in all isolates for which the ciprofloxacin MICs were >/= 0.125 microg/ml and in 94% of the nalidixic acid-resistant isolates but in none of the nalidixic acid-susceptible isolates analyzed. Identification of nalidixic acid resistance by the disk diffusion method provided a sensitivity of 100% and a specificity of 87.3% as tools to screen for isolates for which the MICs of ciprofloxacin were >/= 0.125 microg/ml. We regard it as important that microbiology laboratories endeavor to recognize these less susceptible Salmonella strains, in order to reveal their clinical importance and to survey their epidemic spread.

Anti-Infective Agents↗
PubMed1999

Salmonella enteritidis phage types 1 and 4: pheno- and genotypic epidemiology of recent outbreaks in Finland.

In the 1990s, Salmonella enterica subsp. enterica serovar Enteritidis has caused 15 outbreaks in Finland; 12 of them were caused by phage type 1 (PT1) and PT4. Thus far, there has been no clear evidence as to the source of these Salmonella Enteritidis PT1 and PT4 strains, so it was necessary to try to characterize them further. Salmonella Enteritidis PT1 (n = 57) and PT4 (n = 43) isolates from different sources were analyzed by genomic pulsed-field gel electrophoresis (PFGE), plasmid profiling, and antimicrobial resistance testing to investigate the distribution of their subtypes in Finland. It was also hoped that this investigation would help in identifying the sources of the infections, especially the sources of the outbreaks caused by PT1 and PT4 in the 1990s. The results showed that both PFGE and plasmid profiling, but not antimicrobial susceptibility testing, were capable of differentiating isolates of Salmonella Enteritidis PT1 and PT4. By genotypic methods, it was possible to divide both PT1 and PT4 isolates into 12 subtypes. It could also be shown that all PT1 outbreak isolates were identical and, at least with this collection of isolates, that the outbreaks did not originate from the Baltic countries or from Russia, where this phage type predominates. It was also established that the outbreaks caused by PT4 all had different origins. Valuable information for future investigations was gained on the distribution of molecular subtypes of strains that originated from the tourist resorts that are popular among Finns and of strains that were isolated from livestock.

Animals↗
PubMed1999

Molecular epidemiology of an outbreak of febrile gastroenteritis caused by Listeria monocytogenes in cold-smoked rainbow trout.

Febrile gastroenteritis in five healthy persons was associated with the consumption of vacuum-packed cold-smoked rainbow trout containing Listeria monocytogenes. L. monocytogenes isolates from the incriminated fish product lot and the stool samples were all of serotype 1/2a and were indistinguishable by pulsed-field gel electrophoresis employing AscI and SmaI.

Adult↗
PubMed1998

Oat beta-glucan and xylan hydrolysates as selective substrates for Bifidobacterium and Lactobacillus strains.

Novel oligomers that resist digestion in the upper gut were prepared from oat mixed-linked beta-glucan and xylan by enzymatic hydrolysis with lichenase of Bacillus subtilis and xylanase of Trichoderma reesei respectively. The low-molecular-mass hydrolysis products of beta-glucan and xylan were compared with fructooligomers and raffinose in their ability to provide growth substrates for probiotic (Lactobacillus and Bifidobacterium) and intestinal (Bacteroides, Clostridium and Escherichia coli) strains in vitro. A degradation profile of each carbohydrate and total sugar consumption were analysed with HPLC, and bacterial growth rate with an automatic turbidometer, the Bioscreen C system. beta-Glucooligomers and xylooligomers both enhanced the growth of health-promoting probiotic strains as compared with intestinal bacterial growth, but not to a significant level. Raffinose stimulated the probiotic strains significantly, whereas fructooligomers induced high average growth for intestinal bacteria also.

Bifidobacterium↗
PubMed1998

Reactive arthritis following an outbreak of Salmonella Bovismorbificans infection.

A large, single-source Salmonella outbreak caused by a rare serovar Bovismorbificans (6,8:r:1,5) occurred in southern Finland in 1994. The origin of the outbreak was sprouted alfalfa seeds. A questionnaire was mailed to all 210 subjects with positive stool culture. Ninety-one percent (191/210) returned the questionnaire. One hundred and fifty-three (80%) were adults. One hundred and fifty-nine out of one hundred and ninety-one (83%) reported diarrhoea, 109 (57%) fever, 104 (54%) abdominal pains, 83 (43%) fatigue, 66 (35%) articular symptoms and 20 (10%) had no symptoms. The median duration of diarrhoea was 5 days (range 1-35), that of other symptoms 4 days (range 1-30). Those reporting articular symptoms were examined (51 patients) or contacted by telephone (13 patients). Twelve percent (22/191) fulfilled the criteria for reactive arthritis (ReA). The difference in the incidence of ReA between children and adults was not significant (8%, vs. 12%). The median onset of joint symptoms was 8.5 days; symptoms were oligoarticular in 14 (67%) and polyarticular in four (19%) patients. Mostly ReA was mild, but in four patients (18%) the joint symptoms lasted for more than 4 months. Ten (45%) ReA patients had HLA-B27 tissue type. The duration and severity of ReA did not differ between HLA-B27 positive and negative patients. Fourteen (64%) ReA patients had received fluoroquinolone treatment before reactive joint or tendon symptoms manifested, but this treatment did not prevent ReA symptoms.

Adult↗
PubMed1998

Evaluation of pulsed-field gel electrophoresis of genomic restriction fragments in the discrimination of Yersinia enterocolitica O:3.

One hundred and six Yersinia enterocolitica serogroup O:3, biotype 4 isolated from human and porcine samples in 1984 and in the years 1993 5 were examined by pulsed-field gel electrophoresis (PFGE). The genomic profiles produced by the enzymes NotI and XbaI were studied. Sixteen (A-P) and 8 (1-8) different pulsotypes were obtained, respectively. By combining the pulsotypes produced by both NotI and XbaI 24 different types were distinguished. The two major types, designated as A1 and B1, comprised 36% of all strains tested. The proportions of pulsotypes A1 and B1 were, 35.9 and 25.6%, respectively, among strains isolated in 1984. The corresponding figures among the strains isolated in 1993-5 were 35.8 and 41.8%. Nine pulsotypes were found only in 1984 and nine only in 1993-5. The proportions of the major pulsotypes, A1 and B1, in human isolates were 42.9 and 35.7% and in porcine isolates 22.2 and 36.1% respectively. Six types were found among both human and porcine isolates, 8 only among human strains and 10 only among porcine strains.

Animals↗
PubMed1998

Shiga toxin-producing Escherichia coli in finland from 1990 through 1997: prevalence and characteristics of isolates.

During the past 10 years Shiga toxin-producing Escherichia coli (STEC) has emerged as one of the most important causes of food-borne infections in industrialized countries. In Finland, with a population of 5.1 million, however, only four STEC O157:H7 infections were identified from 1990 through 1995; the occurrence of non-O157 STEC infections was unknown. In 1996, we established a national prospective study to determine the prevalence of STEC serotypes in feces of Finns with bloody diarrhea. During this enhanced 1-year study period eight sporadic cases of STEC infection were found; of them, only two were indigenously acquired O157:H7 infections. In 1997, O157 infections increased dramatically, with O157 strains causing 51 of all 61 STEC infections. Altogether 14 non-O157:H7 STEC strains were found in Finland in the 1990s: O26:H11 (four strains), O26:HNM (HNM indicates nonmotile), O2:H29, O91:H21, O91:H40, O101:HNM, O107:H27, O157:HNM, O165:H25, OX3:H21, and Rough:H49. All O157:H7 and O26:H11 isolates produced enterohemolysin, but seven of the other STEC strains did not. Most (n = 63) of the 71 STEC strains isolated carried the stx2 gene only, five carried the stx1 gene only, and three carried both genes. The eaeA gene was detected in all other isolates except five non-O157 strains. There were seven distinct pulsed-field gel electrophoresis (PFGE) genotypes among 57 O157 strains and three distinct PFGE types among four O26:H11 strains. The main PFGE type was found among 65% of all O157 isolates.

Adolescent↗
PubMed1997

Is it possible to prevent bacterial adhesion onto ureteric stents?

The aim of this study was to determine whether the use of bactericidal coatings or immersion in antibiotic solution reduces or prevents bacterial adhesion onto ureteric stents. Precut segments of full silicone, silver-coated and hydrogel-coated ureteric stents were incubated with two uropathogenic bacterial strains with and without previous immersion in antibiotic solution. Tobramycin, ceftriaxone and ciprofloxacin solutions were used, as these antibiotics are commonly administered for the prophylaxis and treatment of urinary tract infection (UTI). Microbiological analysis showed that immersion of ureteric stents in ceftriaxone and ciprofloxacin yielded a significant reduction of bacterial adhesion, whereas immersion in tobramycin did not. The surface material of the stents had no direct influence on bacterial adhesion. In this experimental study, neither the silver nor the hydrogel coat reduced bacterial adhesion onto ureteric stents whereas immersion in a suitable antibiotic solution significantly reduced and even prevented this phenomenon, probably due to the adhesion of the antibiotic onto the stent surface. Prevention of bacterial adhesion onto ureteric stents is essential to reduce the risk of UTI in connection with these devices.

Anti-Bacterial Agents↗
PubMed1997

Immersion in antibiotic solution prevents bacterial adhesion onto biodegradable prostatic stents.

OBJECTIVE: To determine whether immersion in antibiotic solution reduces or prevents bacterial adhesion onto biodegradable prostatic stents. MATERIALS AND METHODS: Pre-cut segments of polyglycolic acid (PGA) and polylactic acid (PLA) prostatic stents were incubated with two common uropathogenic bacterial strains (Enterococcus faecalis and Escherichia coli) with and without previous immersion in antibiotic solution. Tobramycin, ceftriaxone and ciprofloxacin solutions were used, as these antibiotics are commonly administered for the prophylaxis and treatment of urinary tract infection (UTI). RESULTS: Immersion in ciprofloxacin solution prevented the adherence of both bacterial strains. Immersion in ceftriaxone solution prevented only the adherence of the E. coli strain. Immersion in tobramycin solution had no effect on either of the strains. The stent materials per se did not influence bacterial adhesion. After immersion in ciprofloxacin, the stent segments retained significant antibacterial activity even after one day's incubation in saline. CONCLUSION: Immersion in a suitable antibiotic solution may significantly reduce and even prevent bacterial adhesion onto biodegradable prostatic stents. Preventing bacterial adhesion may reduce the risk of UTI during the use of these devices.

Anti-Bacterial Agents↗
PubMed1997

An international outbreak of Salmonella infections caused by alfalfa sprouts grown from contaminated seeds.

An outbreak of Salmonella serotype stanley infections occurred in the United States and Finland in 1995. The outbreak was investigated through case-control studies in Arizona, Michigan, and Finland; by isolate subtyping; and by tracing and culturing of the implicated food. Alfalfa sprout consumption was the only exposure associated with S. stanley infections in Arizona (matched odds ratio [MOR] = 11.1; 95% confidence interval [CI], 1.4-513), Michigan (MOR = 5.5; CI, 1.6-23), and Finland (MOR undefined; CI, 4.9-infinity). US and Finnish patient isolates were a unique outbreak strain distinct from S. stanley isolates not linked to the outbreak. Alfalfa sprouts eaten by patients in 6 US states and Finland were traced to seed shipped by a Dutch shipper. Thus, it was concluded that alfalfa sprouts grown from contaminated seed caused an international outbreak of > or =242 S. stanley infections in > or =17 US states and Finland. This outbreak illustrates a new mechanism through which contamination of fresh produce can cause large, widely dispersed outbreaks.

Adolescent↗