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A Siitonen

Publications and source records attributed to A Siitonen.

At least 73 records · Page 4Linked to original sources
PubMed1997

Molecular epidemiology of two international sprout-borne Salmonella outbreaks.

Sprout-borne Salmonella outbreaks in Finland have increased during the last 10 years. The latest two were caused by Salmonella enterica serovar Bovismorbificans (antigenic structure 6,8:r:1,5) in 1994 and S. enterica serovar Stanley (4,5, 12:d:1,2) in 1995. In this study, the restriction fragment length polymorphism of genomic DNA after pulsed-field gel electrophoresis (PFGE) and antimicrobial resistance profiles of the outbreak and nonoutbreak strains were compared. In each separate outbreak, the PFGE patterns of the outbreak strains (40 strains of S. enterica serovar Bovismorbificans and 28 strains of S. enterica serovar Stanley) after digestion of genomic DNA with restriction enzyme XbaI were indistinguishable from each other but differed clearly from those of the nonoutbreak strains (26 strains of S. enterica serovar Bovismorbificans and 40 strains of S. enterica serovar Stanley). The restriction enzyme XhoI did not differentiate the outbreak and nonoutbreak strains. The S. enterica serovar Stanley strains associated with the outbreak also had a unique antimicrobial resistance pattern, whereas all S. enterica serovar Bovismorbificans strains, both outbreak and nonoutbreak strains, were sensitive to all antimicrobial agents tested. Thus, the molecular typing confirmed that the S. enterica serovar Bovismorbificans outbreak isolates from humans and sprout salad were identical and strongly supported the epidemiological finding that S. enterica serovar Stanley outbreak isolates also originated from contaminated alfalfa seeds. It also confirmed that the sources of similar outbreaks in Sweden in 1994 caused by S. enterica serovar Bovismorbificans and in the United States in 1995 caused by S. enterica serovar Stanley and the source of the Finnish outbreaks were common.

Disease Outbreaks↗
PubMed1996

Recurrence of urinary tract infection in a primary care setting: analysis of a 1-year follow-up of 179 women.

In a prospective study, 179 adult women (age range, 17-82 years) were followed up for 12 months after an index episode of community-acquired cystitis caused by Escherichia coli. Episodes of symptomatic urinary tract infection (UTI) were recorded, and urinary isolates were compared with the index episode isolate; 147 UTI episodes were detected during the follow-up. Of these episodes, 131 were classified as recurrences occurring at least 1 month after the index episode; 44% of the patients had recurrences. A history of UTI increased the risk of recurrence; only 11.8% of the 17 patients without previous episodes of UTI had at least one recurrence, while 47.5% of those with previous episodes had at least one recurrence (OR, 6.8; univariate logistic regression). E. coli caused 78% of the recurrent episodes. Phenotypic and genotypic analysis of E. coli strains showed that one-third of the recurrences were caused by the index episode strain, which could persist and cause recurrences throughout the 1-year follow-up period. The prevalence of adhesins or other identified virulence factors for UTI among the recurrence strains was identical to that among the index episode strains. The presence of these factors did not affect the risk of recurrence but did increase the likelihood that the index episode strain would persist and cause recurrent episodes of UTI.

Adolescent↗
PubMed1996

Escherichia coli and appendicitis: phenotypic characteristics of E. coli isolates from inflamed and noninflamed appendices.

Two hundred four appendiceal isolates for Escherichia coli from 146 patients with either inflamed appendices (IA) (110 patients) or noninflamed appendices (NA) (36 patients) were characterized. Strains with P fimbriae were detected in 27% of IA and 31% of NA whereas type 1C-fimbriated strains were found only in IA (13%). Four serotypes, three with K5 antigens (O18:K5, O25:K5:H1, and O75:K5:H-) and one with K1 antigen (O75:K1:H7), were isolated only from IA (20 [18%] of 110); O25:K5:H1 was the most common serotype (isolated from 11 IA [10%]). Fecal isolates from the patients with IA resembled their corresponding appendiceal isolates rather than fecal isolates from patients with NA; this finding suggests that colonization of the gut by virulent E. coli--such as a hemolysin-producing, type 1C-fimbriated, P-fimbriated O25:K5:H1 serotype--may be a prerequisite for the development of appendicitis.

Adolescent↗
PubMed1996

Aldehyde dehydrogenase activity and acetate production by aerobic bacteria representing the normal flora of human large intestine.

We have recently proposed the existence of a bacteriological pathway for ethanol oxidation, i.e. ethanol is oxidized by alcohol dehydrogenase of intestinal bacteria resulting in high intracolonic levels of reactive and toxic acetaldehyde. This study was aimed to examine aldehyde dehydrogenase (ALDH) activity, acetaldehyde consumption and production of acetate by aerobic bacteria (n = 27), representing the normal human colonic flora. Most bacterial strains did not show any membrane-associated aldehyde dehydrogenase, but possessed marked cytosolic NADP(+) - and NAD(+) - dependent aldehyde dehydrogenase activity, ranging from 155 nmol of NAD(P)H produced/min/mg of protein to zero with acetaldehyde as substrate. NADP(+)-linked ALDH activity was significantly higher than NAD(+)-linked activity in most of the tested bacteria. In addition, aerobic bacteria metabolized acetaldehyde effectively in vitro and this could be inhibited by cyanamide in nearly half of the tested strains. Production of acetate from acetaldehyde ranged from 2420 nmol/10(9) colony-forming units to almost negligible. In conclusion, many human aerobic colonic bacteria possess significant aldehyde dehydrogenase activity and can, consequently, produce acetate from acetaldehyde in vitro at least under the partially aerobic conditions proposed to prevail on the colonic mucosal surface. Individual variation in the capability of colonic flora to remove toxic acetaldehyde may be one factor regulating intracolonic acetaldehyde levels, as well as the rate of bacteriocolonic pathway for ethanol oxidation.

Acetaldehyde↗
PubMed1996

In vitro alcohol dehydrogenase-mediated acetaldehyde production by aerobic bacteria representing the normal colonic flora in man.

Excessive ethanol consumption has been related with the development of liver cirrhosis, as well as with rapid intestinal transit time and diarrhea. Moreover, heavy drinking is associated with an increased incidence of cancer of the oropharynx, larynx, esophagus, and colorectum. Acetaldehyde of microbial origin has recently been suggested as a possible pathogenic factor behind this alcohol-associated gastrointestinal morbidity. The present in vitro study was aimed to investigate alcohol dehydrogenase activity and acetaldehyde formation capacity of some major aerobic bacteria representing the normal colonic flora in man. Cytosolic alcohol dehydrogenase activity and cytosolic protein concentration were determined spectrophotometrically. Alcohol dehydrogenase activity was then calculated as nmoles of reduced substrate produced by milligrams of protein per minute. The ability of different bacteria to produce acetaldehyde was determined by incubating the intact bacterial suspension in closed vials containing ethanol (final concentration 22 mM) for 1 hr at 37 degrees C. The acetaldehyde formed during the incubation was analyzed by headspace gas chromatography. Marked differences in the alcohol dehydrogenase activity and acetaldehyde forming capacity were found among the strains tested. The alcohol dehydrogenase activity varied from 606 +/- 91 nmol/min/mg protein (Escherichia coli IH 50546) to 1 +/- 0.2 nmol/min/mg protein (E. coli IH 50817), and acetaldehyde formation varied from 1,717 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Klebsiella oxytoca IH 35403) to 5 +/- 2 nmol acetaldehyde/10(9) colony-forming units (Pseudomonas aeruginosa ATCC 27853). There was a statistically significant correlation (r = 0.77; p < 0.001) between alcohol dehydrogenase activity and acetaldehyde production from ethanol, strongly suggesting the catalytic role of bacterial alcohol dehydrogenase in this reaction.

Acetaldehyde↗
PubMed1996

Bacterial adherence and biofilm formation on latex and silicone T-tubes in relation to bacterial contamination of bile.

BACKGROUND: T-tube-related bacteriobilia causes infectious complications and obstruction. To prevent these, the choice of T-tube material may be of importance. METHODS: Transected common bile ducts (CBDs) of 17 piglets were sutured over latex or silicone T-tubes, or without a T-tube. RESULTS: After 6 weeks bacteriobilia was found in all of 12 CBDs with and in 1 of 5 CBDs without a T-tube (p < 0.05). By scanning electron microscopy (SEM) four of five latex and none of five silicone T-tubes had bacterial biofilms (p < 0.05). All tubes remained patent. Segments of T-tubes were incubated with five different bacterial strains. Sonication and SEM showed that 0.1-1.1% of 10(7) colony-forming units of inoculum adhered to T-tubes. Two to six times more bacteria adhered to latex than to silicone (p < 0.05). CONCLUSIONS: Silicone offers better long-term patency than latex. Less infectious complications occur if T-tubes are omitted.

Animals↗
PubMed1996

Bacterial adhesion and biofilm formation on various double-J stents in vivo and in vitro.

The aim of this study was to determine whether bacterial adhesion and biofilm formation occur on various ureteric stent materials in vivo and in vitro and whether there is any correlation between biofilm formation and urinary tract infection. Using an open surgical procedure, 23 double-J stents of 8 different types were inserted in the ureters of 13 piglets. After 6 weeks intubation, 2 (9%) of the 23 stented renal units yielded positive urine culture. Scanning Electron Microscopy (SEM) showed sporadic bacteria on 7 (30%) of the 23 indwelling ureteric stents and bacterial biofilms on only 2 (9%), those indwelling the renal units which yielded positive urine cultures. Precut segments of the 8 double-J stent brands were incubated with 5 different bacterial strains. Microbiological and SEM analysis of the stents revealed that only 0.1-0.01% of the bacterial inoculum adhered to the stents. There was no statistically significant difference in bacterial adherence to the various stent materials. Interestingly, the two Escherichia coli strains with P-fimbriae adhered significantly more than the two without P-fimbriae. Sporadic bacterial adhesion to ureteric stents seemed to have little clinical significance whereas biofilm formation seemed to result in urinary tract infection. None of the tested stents proved to be superior to the others in this respect, and adhesion appeared to depend on the virulence of the bacteria rather than the properties of the biomaterials.

Animals↗
PubMed1996

The first Salmonella enteritidis phage type 1 infection of a commercial layer flock in Finland.

The first Salmonella Enteritidis phage type (PT) 1 infection in a commercial layer flock of 2700 birds in Finland occurred in 1995. All the birds were ordered to be killed, the eggs to be destroyed and access to the layer house was denied in order to prevent spread of the infection. Ninety one commercial layers, 61 replacement pullets and 1062 eggs were collected for the analyses. The total infection level of the flock was 8%, concentrated on the 2 older age groups. S. Enteritidis PT1 was isolated from livers (5%), ovaries (2%) and from caeca (3%), of which 2 positive samples were detected with pre-enrichment and 3 without pre-enrichment by cultivation Rambach agar. Eight % of 105 pooled egg samples were positive, of which 2 were detected only from contents and 3 only from shells indicating both oviductal and faecal contamination routes of eggs. The results support the use of the extended sampling procedure in poultry flocks suspected of human food-borne Salmonella outbreaks of invasive serotypes, including not only faecal but also environmental, organ, blood and/or egg samples.

Animals↗
PubMed1995

Risk Behavior for Travelers' Diarrhea Among Finnish Travelers.

Background: Contaminated food and drink are the primary sources of traveler's diarrhea (TD). Identification of the characteristics that make a traveler more prone to TD is needed to improve prevention and therapy of this illness. Methods: We evaluated, by questionnaire, the association of dietary errors with TD among 933 adult Finnish tourists vacationing in Morocco. A stool specimen was obtained from patients in the group that developed TD at the onset of the diarrheal episode, and from all participants in the study on their return to Finland. Results: Only 5% of the 933 subjects who responded to the questionnaire, and who gave a stool sample, had adhered strictly to generally accepted recommendations. About 45% made five or more dietary errors during the trip; of these, 75% consumed raw vegetables, 65% salads, 33% puddings, 32% mayonnaise or other cold dressings, 31% consumed food bought from street vendors, 29% consumed cold meat, 18% cold sandwiches, 4% drank tap water, and 2% consumed raw meat. The age of the subjects did not correlate with the number of dietary errors. Subjects who had been abroad during the preceding 12 months committed more dietary errors than those who had not (mean 3.9 versus 4.5; p <.001). Also, subjects who spent 2 weeks in Morocco committed more dietary errors than those who spent only 1 week (mean 4.0 versus 4.8; p <.001). However, no association between TD and the number of dietary errors was observed. Differences with respect to eating habits were not observed between subjects, with or without TD or with or without an identified pathogen in stool specimens. There was no correlation between eating habits and the presence, or absence, of a specific pathogen in the stool sample; this is with the exception of Campylobacter spp: subjects with this pathogen consumed steak tartar or salad more often than did other subjects. Conclusions: Etiologic agents are so ubiquitous in this high-risk area that instructions to avoid certain foodstuffs commonly thought to be contaminated may be to some extent without value. Moreover, dietary self restraint proved to be impossible in the real situation. (J Travel Med 2:77-84, 1995)

Journal Article↗
PubMed1995

Subtyping of Shigella sonnei for tracing nosocomial transmission.

Nosocomial transfer of Shigella spp. occurred between two patients sharing the patient room and toilet in a ward for internal medicine. Both patients had travelled abroad shortly before the onset of illness. Based on the epidemiology of Shigella sonnei strains imported into Finland, nosocomial infection was strongly suspected. The isolates of S. sonnei were subtyped using ribotyping, plasmid analysis and antibiotic resistance patterns. The greatest discrimination between the strains was achieved by ribotyping. The results of the typing scheme confirmed the nosocomial transmission of S. sonnei. The outbreak did not spread further within the ward. The importance of isolation of a patient with diarrhoea in a hospital setting is emphasized.

Adult↗
PubMed1995

Distribution of Aeromonas phenospecies and genospecies among strains isolated from water, foods or from human clinical samples.

A total of 332 Aeromonas spp. originating from drinking water (n = 75), fresh water (n = 57), chicken and ground beef (107), human faecal samples in association with travelling (n = 49), human faecal samples not associated with travelling (n = 38), and six strains from human blood cultures were studied by phenotypic methods and by using analysis of ribopatterns as a molecular method for the identification of the 13 known hybridization groups (HGs). Also included were the reference strains of each HG. A. hydrophila HG 1, A. caviae HG 4 and A. veronii biotype sobria HG 8/10 were the most important genospecies identified in human faecal samples. A. hydrophila HG 2 and A. media HG 5B predominated in drinking water and A. hydrophila HG 2 and HG 3, A. media HG 5A and HG 5B predominated in fresh water. In drinking water only one isolate was A. hydrophila HG 1 and two isolates were A. caviae HG 4. Clinically important Aeromonas spp. HG 1 (A. hydrophila), HG 4 (A. caviae) and HG 8/10 (A. veronii biotype sobria) were common in chicken and ground beef. In contrast to the drinking water samples, HG 5A was common in chicken and ground beef samples. Atypical, unidentified isolates were most often found in fresh water samples (12/57 strains). Although water has been suspected of being an important source of human aeromonas infections, clinically important HGs were found to be in the minority among Aeromonas spp. identified in drinking water or fresh water. The distribution of Aeromonas spp. HGs among drinking water, chicken and ground beef samples was also different, suggesting that contamination of meat or chicken may not originate from water.

Adult↗
PubMed1995

Association of Aeromonas spp. with travellers' diarrhoea in Finland.

The association of Aeromonas spp. with travellers' diarrhoea was studied among 978 Finnish tourists travelling to Morocco in winter (n = 398) and autumn (n = 580) in 1989. Fifty-five isolates from diarrhoeal patients with (n = 16) or without (n = 39) a recent travelling history in a developing country were also included. In Morocco, Aeromonas spp. were isolated from 8.7% of patients with diarrhoea and from 1.4% of non-diarrhoeal tourists (p < 0.001). Aeromonas spp. were found as the sole pathogen in 5.5% of patients (p < 0.001). Diarrhoea with multiple pathogens, including Aeromonas spp., was found in 3.1% of patients. Species identification by phenotypic and genotypic methods indicated that A. veronii biotype sobria (hybridisation group HG 8/10) and A. caviae (HG 4) were the most common Aeromonas spp. associated with travellers' diarrhoea. A. hydrophila (HG 1) and A. caviae (HG 4) were common in patients acquiring diarrhoea in Finland. Ribotyping of strains within a species showed that all strains had different ribotypes although the tourists were infected during the same trip. This study suggested that only certain Aeromonas spp. were commonly found in travellers' diarrhoea. However, the causative role of those species is unclear.

Aeromonas↗
PubMed1995

Serological variety of flagellar antigen H1 in natural Escherichia coli population.

Variation of the Escherichia coli flagellar antigen H1 was studied among 120 human isolates belonging to more than 25 O:K serovars. Factor-specific antisera were prepared and shown to be useful in the identification of serological subtypes of H1. The three subtypes found were defined as H1abc, H1acd and H1abe. The H1abc corresponded to the standard flagellar antigen H1 present in 84% of all strains. It was found in all O groups except O15, O17 and O83. Eight O15 and two O17 strains studied were of subtype H1abe, while the one O83 strain studied was H1acd. Both subtypes H1abc and H1acd were found among strains within O6:K5, O6:K13 or O-non-typeable:K5 serovars.

Animals↗
PubMed1995

Quantitative differences in adhesiveness of type 1 fimbriated Escherichia coli due to structural differences in fimH genes.

Type 1 fimbriae are heteropolymeric surface organelles responsible for the D-mannose-sensitive (MS) adhesion of Escherichia coli. We recently reported that variation of receptor specificity of type 1 fimbriae can result solely from minor alterations in the structure of the gene for the FimH adhesin subunit. To further study the relationship between allelic variation of the fimH gene and adhesive properties of type 1 fimbriae, the fimH genes from five additional strains were cloned and used to complement the FimH deletion in E. coli KB18. When the parental and recombinant strains were tested for adhesion to immobilized mannan, a wide quantitative range in the ability of bacteria to adhere was noted. The differences in adhesion do not appear to be due to differences in the levels of fimbriation or relative levels of incorporation of FimH, because these parameters were similar in low-adhesion and high-adhesion strains. The nucleotide sequence for each of the fimH genes was determined. Analysis of deduced FimH sequences allowed identification of two sequence homology groups, based on the presence of Asn-70 and Ser-78 or Ser-70 and Asn-78 residues. The consensus sequences for each group conferred very low adhesion activity, and this low-adhesion phenotype predominated among a group of 43 fecal isolates. Strains isolated from a different host niche, the urinary tract, expressed type 1 fimbriae that conferred an increased level of adhesion. The results presented here strongly suggest that the quantitative variations in MS adhesion are due primarily to structural differences in the FimH adhesin. The observed differences in MS adhesion among populations of E. coli isolated from different host niches call attention to the possibility that phenotypic variants of FimH may play a functional role in populations dynamics.

Adhesins, Bacterial↗
PubMed1995

Characterization of Hafnia alvei by biochemical tests, random amplified polymorphic DNA PCR, and partial sequencing of 16S rRNA gene.

Hafnia alvei strains which possess the attachment-effacement gene (eaeA) may have clinical importance as new diarrhea-causing pathogens and should therefore be differentiated from other H. alvei strains. We characterized diarrheal H. alvei strains, which were positive in the PCR test for the eaeA gene, using biochemical tests not routinely used for identification of members of the family Enterobacteriaceae, and compared them with eaeA-negative strains isolated from different clinical and nonclinical sources to find characteristics useful for identification. Random amplified polymorphic DNA (RAPD)-PCR and partial sequencing of the 16S rRNA gene were utilized to study the genetic diversity of the isolates. The eaeA-positive strains were found to have many characteristic biochemical properties. Negative reactions in the 2-ketogluconate and histidine assimilation tests and a positive reaction in the 3-hydroxybenzoate assimilation test may be useful in routine diagnostics. Nearly identical RAPD-PCR profiles and identical 353-bp fragments of the 16S rRNA genes indicated little genetic diversity among the eaeA-positive strains. The low level of homology (92%) in the partial 16S rRNA genes of eaeA-positive and -negative H. alvei strains raises questions about the taxonomic positioning of eaeA-positive H. alvei.

Base Sequence↗
PubMed1994

Ribotyping as an epidemiologic tool for Escherichia coli.

Restriction fragment length polymorphism of ribosomal RNA genes was analysed among 133 Escherichia coli strains predominantly from blood and urine, including 21 isolates from faeces of healthy persons. The strains had also been characterized for their O:K:H serotypes, for the presence of P, S and type 1C fimbriae, non-P, non-S mannose-resistant haemagglutinins and haemolysin production. Hind III-digested genomic DNA was subjected to Southern blot analysis with either plasmid pKK3535 containing E. coli rRNA operon or purified rRNA as a probe. Among the 133 strains 20 ribotypes were obtained. The distribution of strains into different ribotypes generally correlated with their O:K:H serotype. Ribotype variation within serotypes was mainly seen among strains with the K5 capsule. The origin of the strains or the presence of virulence-associated factors did not correlate with the ribotype. In conclusion, ribotyping appears to be a valuable method in epidemiologic studies especially when the serotyping methods are not available.

Bacterial Adhesion↗