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A study of self-assessed hearing problems was performed comprising 48,680 Swedish inhabitants aged 16-84 years. The participants of the survey responded to personal interviews during the period 1986-1993. One of the questions in the interview concerned difficulties of hearing in background noise. The total prevalence of the reported hearing problems was 10.7 per cent, varying from 2.4 per cent in the youngest age group to 30 per cent in the oldest. Men reported difficulties in hearing more often than women, except in the youngest age group. Hearing problems were more often reported by manual workers, unemployed and by those who had taken early retirement, than by non-manual employees and the self-employed. Regional differences regarding hearing problems were observed. The prevalence of self-reported problems was lowest in metropolitan Stockholm (7.9 per cent) and increased in the following order: other major cities (9.4 per cent), other cities (10.5 per cent), small population centres (12.5 per cent), agricultural areas (13.5 per cent) and sparsely populated forest areas (15 per cent). In summary, a number of factors related to ageing, socioeconomic status and domicile were related to self-assessed difficulties hearing a conversation. These factors obviously include determinants such as genetics, health status, gender-related differences, exposure to noise and possible conditioning effects of low-level noise exposure.

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We used the Phene Plate generalized microplates to investigate the metabolic activities of faecal flora of pigs during pre- and post-weaning periods. Weekly samples were collected from four sows and their litters (four piglets from each) during 5 months. The metabolic fingerprints obtained from faecal floras of sows and their litters in the first sampling occasion was very similar, suggesting that sows were the initial source of flora for piglets. This similarity, however, was lost in week 2 and piglets developed new types of flora which, although similar among the litter-mates, differed from those of the sows. The metabolic fingerprints of pigs' floras during the post-weaning period also differed from those of the suckling period. On day 70 pigs were transferred to a fattening stable. The faecal flora of the animals during this period was unstable in each individual and differed among litter-mates. A pattern of successive changes was observed in the fermentative capacity (FC) of pigs' floras reaching the highest value before weaning (day 34). An overall decrease in the FC value of faecal floras was observed as a consequence of dietary shifts from milk to solid food to high energy fattening diet. The mean FC value of pig floras on the first sampling occasion (mean +/- S.D. = 0.41 +/- 0.02) was significantly higher than that obtained in the last sampling occasion (day 145) (0.31 +/- 0.04) (P < 0.001). Faecal floras of sows also had lower FC values (0.25 +/- 0.01) than those of piglets suggesting that loss of FC by the faecal flora of young pigs will continue as they age.

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A total of 109 Escherichia coli isolates from piglets with diarrhoea, that had previously been shown to be enterotoxin producers, but negative for the adhesive fimbriae K88, K99, 987P and F41 were tested for the presence of more recently characterised fimbriae. Testing was done by immunodot assay with absorbed polyclonal antisera against Av24 and F107 fimbriae, and unabsorbed polyclonal antiserum and monoclonal antiserum against 2134P fimbriae. Strains were also tested by polymerase chain reaction for the presence of genes encoding the major subunit of F107 fimbriae. After elimination of possible non-specific reactions, antisera testing produced 10 strains positive with all 4 antisera, 1 strain that reacted with all antisera except F107, 2 strains that reacted with all antisera except the 2134P monoclonal, 3 strains that reacted with 2134P polyclonal and F107 and 2 that reacted with F107 only. The PCR testing confirmed the results of the antisera, but also produced an additional 14 positive strains, giving a total of 30% of the strains tested reacting positively by PCR. Furthermore, all 33 isolates positive by PCR came from pigs that were older than 1 week, which is 45% of the 72 isolates tested which came from older pigs.

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A highly discriminatory and standardized biochemical fingerprinting method was used to monitor the persistence and colonization of intestinal Escherichia coli isolated from the feces of four sows and their litters (four piglets from each) during the suckling, postweaning, and fattening periods. Altogether, 195 fecal samples were collected and 1,827 E. coli strains were tested (mean number of isolates tested per fecal sample per pig, 9.5). Strains were divided into similarity groups on the basis of their biochemical phenotypes (BPTs). The diversity of E. coli strains in each sample was measured with Simpson's index of diversity, and similarity between E. coli floras of piglets was calculated with a population similarity index. Each fecal sample contained several BPTs of E. coli, some of which dominated that population. The intestinal colonization of piglets consisted of successive waves of different E. coli BPTs, the tenure of which varied from a few days to 2 weeks. Most of these BPTs disappeared in the succeeding samples and were not recovered again from the same piglets. On the other hand, some E. coli strains which colonized piglets early during the suckling period persisted for a long period and were referred to as resident BPTs. Each piglet carried more than one resident BPT (mean of 2.4 BPTs per pig), some of which were also found in other piglets.(ABSTRACT TRUNCATED AT 250 WORDS)

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The present investigation comprised 5 specialized herds of slaughter pigs, each with a production of 1,500 to 4,000 fatteners per year. High prevalence of pleuritis was demonstrated in all herds at slaughter. Serological investigations by means of ELISA were carried out to determine antibody titres to Actinobacillus pleuropneumoniae (A. pl.) serotype 2 during the fattening period and at slaughter. The investigations showed that this agent was a predominant cause of the subclinical pleuritis although A. pl. was difficult to isolate. An environment study was performed in all herds and major environmental deficiencies were corrected during the course of the investigation. Similarly, all herds changed to a strict routine of batch rearing. In 4 herds out of 5, the animals were vaccinated on arrival to the growing-finishing units and again generally 3-4 weeks later with an inactivated vaccine against A. pl. serotype 2. The prevalence of pleuritis decreased with 25-75% during the three-year observation period. Also the prevalence of pneumonia decreased at the same time. Conversely, daily weight gain and feed conversion improved. The prevalence of pleuritis and pneumonia registered at slaughter was lower in three-breed crosses (including Hampshire, Landrace and Yorkshire) than in the two-breed crosses with Landrace and Yorkshire.

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Strains of Erysipelothrix rhusiopathiae isolated at 19 pig farms serving a certain abattoir, and on pork and in workers of this abattoir were studied. Mouse-pathogenic E. rhusiopathiae was found in pig slurry from two farms (11%). The strains belonged to serotypes 7 and 16 (both from the same farm) or were untypable. In pig slurry from the abattoir lairage only serotype 2 strains were found and all were pathogenic to mice. Mouse-pathogenic E. rhusiopathiae strains of serotype 2 were also recovered from 25 pork lions (25%). A mouse-pathogenic E. rhusiopathiae (serotype 2) strain was isolated from one of the 16 hand infections of slaughterhouse workers. The E. rhusiopathiae strains were phenotypically grouped by the API 50 CH system. Variations were demonstrated for the different serotypes. In 20 of 138 workers antibodies against E. rhusiopathiae were found; 14 had increased levels of IgG antibodies, seven had increased levels of IgM antibodies and one had an increased level of both.

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The present investigation comprised six integrated herds (100-150 sows each) and one specialized fattening herd. Serologic tests by ELISA were performed on blood samples from piglets and growing pigs during various rearing phases in order to determine the presence of Actinobacillus infection and to estimate the age of the animals at onset of the disease. Using this information, herd-specific vaccination programs were designed against Actinobacillus pleuropneumoniae serotype 2. The weaned piglets in the integrated herds were vaccinated twice before being moved to the fattening unit. In the specialized fattening herd, the pigs were vaccinated on arrival at the growing unit and just before transfer to the finishing unit. The frequencies of chronic pleuritis at slaughter demonstrated that a vaccination program adapted to the herd-specific problem, in combination with environmental improvements, reduces the prevalence of chronic pleuritis. On the other hand, only a moderate reduction of the prevalence of chronic pleuritis occurred as a result of vaccination if no environmental improvements were made. In two of the herds during the vaccination period, the number of feeding days and food consumption decreased, while growth per day increased. There was also an apparent correlation between higher serum titres and a decreased prevalence of pleuritis at slaughter in three of the herds.

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Parenteral vaccination of sows against Escherichia coli diarrhea in their newborn piglets has become more common during the last decade in Sweden, and the vaccination has generally had positive effects. For more than 20 years we have investigated E. coli strains isolated from piglets and weaned pigs with enteric disorders, noting the presence of O groups, enterotoxins, and adhesins. There has been a continuous change in the frequency of these virulence factors. The present study was performed during 1983 and 1984 to follow this change, since such information is essential for the proper choice of vaccines. A total of 856 E. coli strains were obtained from 683 herds divided into three age groups: 1 to 6 days old, 1 to 6 weeks old, and weaned pigs. O group 149 still dominated in the last two age groups, while O group 101 was, for the first time, the most frequent O group in neonatal piglets. All but four O149 strains carried the K88 antigen, which was found in only one other strain (O group 8). K99 antigen was most often found in O groups 101 and 64, and among all the K99 strains ST mouse was the most common (44 of 57), followed by ST mouse-ST pig strains (12 of 57). The 987P antigen was demonstrated in 26 strains belonging to O groups 141 and OX46 and nontypable strains. Two strains belonging to O group 101 were positive for F41 antigen; one of them also carried the K99 antigen. Among all non-O149 strains, ST mouse was the most common type of enterotoxigenic E. coli ( n = 88), followed in decreasing order by ST mouse-ST pig strains ( n = 69) and ST pig strains ( n = 33). In 114 strains producing enterotoxins no adhesive factor was found. Thus, vaccination of the Swedish sow population for more than 5 years with vaccines containing O149 and K88 antigens has apparently changed the pattern of enterotoxigenic E. coli in neonatal diarrhea. The frequency of O149:K88 strains has been reduced, and O101:K99:ST mouse strains now dominate. However, O149 strains remain the dominant O group in piglets older than 1 week. In spite of all our diagnostic efforts, no virulence factors were detected in about one third of the piglets and weaned pigs with enteric disorders.

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Intestinal immune responses to Escherichia coli antigens were studied in conventionally reared piglets orally infected on the first day of life with a virulent enterotoxigenic E. coli (O149: K88). During the first week of life intestinal antibodies were produced against the homologous lipopolysaccharide (LPS) as well as against the K88 antigen and the heat-labile enterotoxin (LT). On Day 7, anti-LPS antibodies of the IgA and IgG classes were detected in most piglets, whereas anti-K88 antibodies of the IgG and IgM classes predominated; antibodies against the enterotoxin were usually of the IgG class. In 21-day-old piglets antibodies of all immunoglobulin classes had usually been produced. In most cases, the levels of intestinal antibodies were substantially higher on Day 21 compared to Day 7, but the levels varied considerably both between and within litters. The intestinal immune responses did not correlate with the severity of clinical symptoms. One-, 7- and 21-day-old piglets reared in a specific-pathogen-free (SPF) herd lacked significant intestinal antibodies to the antigens examined. The oral challenge did not stimulate systemic immune responses. After colostral intake, all piglets had high antibody levels in the circulation. These levels decreased continuously during the 3-week study period. The possibility that high amounts of antibodies in colostrum could interfere with this early intestinal antibody formation should be considered when planning vaccination programmes against E. coli diarrhoea in piglets.

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A competitive enzyme-linked immunosorbent assay (ELISA) was compared with the conventional suckling mouse assay for the identification of heat-stable enterotoxin (STa) in samples from piglets suffering from diarrhea. A total of 110 Escherichia coli isolates, 22 primary cultures, and 26 fecal samples from piglets up to 8 weeks of age with diarrhea were compared in parallel by both assays. Of the 110 isolates tested, all gave consistent results by the ELISA and the suckling mouse assay; 60 strains were negative and 50 strains produced STa by both tests. Identical results were obtained when 22 primary agar cultures were screened for STa production by both methods; 6 were found to produce STa, while 16 did not. When 26 fecal samples were tested for the presence of STa, 10 were negative and 12 were positive by both assays. One of the remaining four samples gave questionable positive results by both the suckling mouse assay and the ELISA, but E. coli isolated from this sample gave positive results by both tests. The remaining three samples were negative by the suckling mouse assay, but gave questionable positive results by the ELISA. E. coli isolates from these three samples were always negative by both assays. The ELISA used in this study provides a reliable and convenient method for diagnosing STa-producing enterotoxigenic E. coli of porcine origin.

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Escherichia coli strains causing diarrhoea in Swedish piglets were isolated; this investigation was made over a 20-year period, from 1964 to 1984. Many of the isolates belonged to O-groups 8, 141 and 149. These strains were separated into different phenotypes with the aid of a new method, "biochemical fingerprinting". This method has been especially designed to sort E. coli-isolates into various phenotypes based on a pattern of quantitatively measured biochemical reactions. It was found that most pathogenic isolates carrying O-antigen 8 belonged to the same phenotype. This phenotype was common in the 1960's, but later it disappeared from the population and was replaced by a wide variety of different phenotypes, most of them non-enterotoxinogenic, but still belonging to O-group 8. In O-group 141 one phenotype dominated in the 1960's, but in the 1970's a new phenotype appeared, which further increased in number in the 1980's. By contrast, in the O-group 149 practically all strains isolated during the 20-year period were found to carry the relevant virulence factors and belong to the same phenotype.

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To evaluate the effect of widely used parenteral vaccination of dams against neonatal colibacillosis, the virulence factors of the intestinal Escherichia coli flora, namely, O serogroup, enterotoxin(s) produced (heat labile, porcine heat stable, and murine heat stable) and adhesins (K88, K99, and 987P antigens) of 149 piglets from different herds in Sweden were investigated. Three categories were investigated: healthy piglets, diarrheal piglets born to unvaccinated dams, and diarrheal piglets born to dams vaccinated with a polyvalent Formalin-killed whole-cell vaccine containing K88 antigen (Porcovac; Hoechst Pharmaceuticals, Hounslow, England). Piglets less than 1 week old and those 1 to 8 weeks old were evaluated separately. Diarrheal piglets less than 1 week old from vaccinated dams yielded a higher incidence of K99 antigen-positive E. coli of the murine heat-stable enterotoxigenicity type compared with piglets of the same age group from unvaccinated dams. The percentage of diarrheal cases from which E. coli lacking recognized virulence attributes were isolated was also higher in the former compared with the latter group. In the 1- to 8-week-old diarrheal piglets of vaccinated dams, the overall incidence, enterotoxigenicity type, and serotype of the E. coli isolates resembled those of diarrheal piglets less than 1 week of age from unvaccinated herds. Enterotoxigenic E. coli bearing 987P antigen detectable in vitro was rare. Most of the enterotoxigenic isolates lacking K88, K99, and 987P antigens produced only ST. The investigation pinpoints some of the inadequacies of vaccines of the type studied under field conditions.

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K88 antigen-negative enterotoxigenic Escherichia coli and non-enterotoxigenic strains isolated from piglets with diarrhea were examined for K99 antigen by agglutination tests after growth on Minca-IsoVitaleX (BBL Microbiology Systems, Cockeysville, Md.) agar medium. Of 64 K88-negative enterotoxigenic strains from as many piglets, 17 were found to be K99 positive. Of these, 10 were Swedish and 7 were of Norwegian origin. All 17 produced heat-stable enterotoxin detectable in the infant mouse assay, but only 2 gave positive ligated loop tests in 3- to 7-week-old piglets. Ligated loop tests in 5- to 12-day-old piglets were positive for each of the 15 K99-positive strains tested. Each of the Swedish K99-positive isolates was from a piglet of lesser than or equal to 7 days of age. One piglet harboring a K99-positive strain also harbored an O141:K88 enterotoxigenic strain producing only heat-stable enterotoxin. Five of the Swedish piglets yielding K99-positive isolates were from dams vaccinated wih a multicomponent bacterial vaccine containing K88 antigen. The K99 strains were O:K:H serotyped. The O serogroups represented were O8, O9, O64, O101, and O140. None of the 101 non-enterotoxigenic porcine isolates, representing 42 serogroups and non-O-groupable and rough strains, was found to be K99 positive. The findings indicate that so-called class 2 or atypical porcine enterotoxigenic E. coli should be routinely examined for the presence of K99 antigen.

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Ninety-one Escherichia coli strains isolated from porcine neonatal diarrhea, representing 28 O-groups and rough and non-O-groupable strains, were examined for enterotoxigenicity (heat stable [ST] or heat labile [LT]) by using bacterial suspensions in intestinal loop tests in 3- to 7-week-old piglets and culture supernatant fluids in the Y1 adrenal cell test, the 18-h rabbit intestinal loop test, and the infant mouse test. Eleven strains in O-groups 101, 138, 147, and 149 were positive in all four assay systems and were designated ST + LT. Fourteen strains within O-groups 8, 9, 20, 64, 141, and 149 and non-O-groupable were positive only in the 3- to 7-week-old piglet loop test and the infant mouse test and were designated ST pig + mouse. Sixteen strains distributed among O-groups 8, 16, 32, 50, 51, 98, 115, 141, 149, and 157 were positive only in the piglet intestinal loop test and were designated ST pig. Three strains of O-groups 8, 9, and 140 were positive only in the infant mouse assay and were designated ST mouse. Two strains of O-group 149 were positive in all tests except the infant mouse test and were designated LT. A total of 42 strains were negative in all four tests (Ent(-)), and 3 strains could not be categorized by the enterotoxigenicity criteria used. All K88-positive isolates, 17 strains of O-groups 8, 32, 147, and 149, were positive in at least one enterotoxigenicity test. ST pig and ST mouse strains gave positive intestinal loop tests as bacterial suspensions in 4- to 10-day-old piglets. A 6-h piglet intestinal loop test performed with heat-inactivated culture supernatants was preferable to an 18- to 20-h test for determination of ST production by strains of diverse O-groups. ST production by the two strains designated LT was detected by the 6-h test. The infant mouse test, although highly reproducible and convenient, appears to possess considerable limitations in routine screening of E. coli of porcine origin for ST production.

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In a comparison between piglets (1-7 days old) with diarrhea and healthy piglets of the same age and 1 to 8 weeks old, 810 intestinal strains of Escherichia coli from 81 piglets from as many different herds in Sweden were investigated with regard to O-group, enterotoxicity, and possession of K88 antigen. A clear difference was found between the E. coli isolates from piglets with diarrhea and from representatives of healthy herds without diarrhea, with regard to (i) the homogeneity of strains in individual pigs and (ii) the distribution of O-groups, K88 antigen, and frequency of enterotoxicity. Strains from piglets with diarrhea showed a high frequency of O-group 149 (53%), enterotoxicity (61%), and K88 antigen (56%), while not more than 3% of the strains from healthy piglets of the same age harbored any of these characteristics. Of the isolates in O-groups 8, 64, and 115, 36% were enterotoxigenic. The corresponding data for O-group 149 and nontypable strains were 96 and 1%, respectively. Furthermore, K88 antigen was only found in O-groups 8 and 149. In O-group 149, 96% of the strains (n = 167) produced the K88 antigen as well as heat-labile enterotoxin. In contrast, strains producing heat-stable enterotoxin were mainly found in O-groups 8, 9, 64, 115, and 141. There was a significant difference in the frequencies of E. coli strains producing heat-labile enterotoxin between piglets with diarrhea and those without, whereas the pathogenic role of heat-stable enterotoxin-producing strains was less apparent.

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Porcine enteropathogenic Escherichia coli strains possessing or lacking K88 antigen were studied by using hydrophobic interaction chromatography on cross-linked agarose gels with alkyl or aryl substituents (amphiphilic gels) to determine whether or not they possessed surface-associated hydrophobic properties. Strains with K88ab or K88ac antigen adsorbed to phenyl and octyl Sepharose gels in the presence of 4 M sodium chloride. This property correlated with phenotypic expression of K88 antigen. Cells grown at 37 degrees C but not those grown at 18 degrees C possessed hydrophobic adsorptive characteristics in addition to the property of mannose-resistant hemagglutination of guinea pig erythrocytes. Adsorption of K88-positive strains to gels with hydrophobic ligands was independent of O group and enterotoxicity. Strains lacking K88 antigen did not adsorb to the hydrophobically substituted derivatives of Sepharose and lacked mannose-resistant hemagglutinating characteristics. Neither the presence of additional polysaccharide K antigens nor nonhemagglutinating pili conferred the property of hydrophobic interaction on the strains. K88-positive bacteria had a lower electrophoretic migration rate than did K88-negative bacteria of the same serotype in free-zone electrophoresis. K88-positive bacteria also adsorbed strongly to hydrophobic ligands in the presence of 1 M ammonium sulfate, whereas K88-negative strains did not. These observations provide evidence for the suspected role of hydrophobic interaction in the adhesive properties of certain enteropathogenic strains of E. coli. Moreover, hydrophobic interaction chromatography provides convenient and rapid alternative means of screening strains for a property potentially associated with adhesiveness.

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