Biomedical subjects

I Kühn

Publications and source records attributed to I Kühn.

At least 19 recordsLinked to original sources

PubMed1995

Comparison of five calculation modes for antibody ELISA procedures using pertussis serology as a model.

During a phase III pertussis vaccine trial, serum antibody responses were measured by two enzyme-linked immunosorbent assays (ELISA) for pertussis toxin and filamentous haemagglutinin. These were used both for studies of antibody levels after vaccination and for diagnostic purposes. Since the absorbance values obtained were not directly proportional to the amount of antibody in the samples, ELISA optical densities were transformed to units by calibration to a reference serum. Five different calculation modes were compared. In four of these modes unit calculations were based on the relationship between dose response curves of the serum sample and a reference serum. In addition, traditional endpoint titres were included in the comparison. The calculation mode using reference line units showed the highest reproducibility, with intrassay coefficients of variation (CV) within the same test plate of 4-7% and interassay CVs of 12-14%. The CVs among the other methods ranged from 6 to 31% for intra-assay comparisons and from 12 to 47% for interassay comparisons. Furthermore, the CV values for intra-assay variations were used to calculate standardized differences between 79 pairs of acute and convalescent sera from cases confirmed by culture. These differences were then used to estimate the 'diagnostic sensitivity' for the different calculation modes. The results indicated that use of the reference line units was the most sensitive, whereas use of the end point titers was the least sensitive of these calculation modes.

Adult↗

PubMed1995

Determination of ochratoxin A in bile of swine by high-performance liquid chromatography.

A method for the determination of low concentrations of the mycotoxin ochratoxin A (OA) in bile of pigs is described. OA was extracted with acidified chloroform and the extract was purified on a silicagel cartridge, followed by liquid-liquid partition. OA was determined by high-performance liquid chromatography with fluorescence detection. The detection limit was 0.3 ng/ml, the mean recovery was 84%. An enzyme-linked immunosorbent assay proved to be suitable for confirmation of positive results. Because of the low detection limit, biliary elimination of OA in pigs fed with low-contaminated feedstuffs can be examined by this method. This is an important requirement for the study of pharmacokinetic profiles of OA.

Animal Feed↗

PubMed1995

Typing of coagulase-negative staphylococci from peritonitis in CAPD-patients by the PhP-CS system and REA.

Coagulase-negative staphylococci (CNS) were the most common bacteria causing peritonitis in patients treated with continuous ambulatory peritoneal dialysis (CAPD). In order to investigate if the same clone was responsible for the peritonitis in the different patients and if the exit site was the source of infection we followed 68 patients on CAPD for 2 years. During this period 9 patients had 12 episodes of peritonitis caused by CNS. Cultures were taken from exit site and peritoneal fluid in all patients at peritonitis and during the first study year at monthly intervals. In each culture up to 10 isolates of CNS were randomly collected and frozen. All 437 CNS isolates from the patients with CNS peritonitis were typed using a biochemical typing method and 41 isolates identical by this method were further discriminated by a DNA fingerprinting method. Identical strains were in no case isolated from different patients, indicating that no virulent strain was spread between the patients. The isolates causing the peritonitis were never found at the exist sites before the first day of the peritonitis in any patient. In only two patients was the same strain found at the exit site and in the peritoneal fluid on the first day of peritonitis. It thus seems that no virulent clone of CNS was infecting the patients and we found no evidence of CNS at the exit site causing the peritonitis.

Adult↗

PubMed1995

Phenotypic characterization of intestinal Escherichia coli of pigs during suckling, postweaning, and fattening periods.

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)

Animals↗

PubMed1995

An alternative synthesis of the NMDA antagonist CGS 19755 via free radical carbamoylation of ethyl isonicotinate.

The NMDA antagonist CGS 19755 (cis-4-phosphonomethyl-2-piperidinecarboxylic acid) has been prepared by applying Minisci reaction conditions [formamide, hydrogen peroxide, iron(II) sulfate] to ethyl isonicotinate, reduction of the ester with sodium borohydride, alcoholysis of the 2-carboxamide, formation of 4-(diethylphosphonomethyl)-2-pyridinecarboxylate, hydrogenation of the pyridine nucleus, and acid hydrolysis. The overall, unoptimized yield was around 11%. The procedure employs cheap starting materials, is practical and avoids the use of toxic and hazardous cyanotrimethylsilane which is used in the published procedure.

Free Radicals↗

PubMed1992

The importance of P and type 1 fimbriae for the persistence of Escherichia coli in the human gut.

The faecal Escherichia coli flora was studied in 89 infants. Each infant was followed with a mean of 12 faecal samples (range 5-21) between 0 and 18 months of age. All isolates were assayed for P fimbriae and biochemically phenotyped and the persistence of each strain (phenotype) in the infant's gut was determined. In a subset of strains the occurrence of type 1 fimbriae and adherence to HeLa cells was studied. Thirty-one per cent of isolates belonging to strains colonizing for longer than 6 months expressed P fimbriae compared to 19% of the isolates from strains colonizing 1-6 months or transient strains colonizing less than 1 month. Type 1 fimbriae and adherence to HeLa cells occurred similarly often in all groups of strains. We conclude that P fimbriae, but not type 1 fimbriae or HeLa cell adherence seemed to contribute to the ability of the E. coli strain to colonize the human intestine.

Bacterial Adhesion↗

PubMed1992

Application of biochemical fingerprinting to the investigation of clonal groups of Salmonella of serotype Havana.

A computerised typing method based on biochemical fingerprinting was used to investigate biochemical phenotypes (BPTs) among 70 strains of Salmonella of serotype Havana isolated from human cases of gastroenteritis in Iran and other parts of the world. A total of 16 BPTs comprising five common and 11 single phenotypes was identified. The most frequently found BPT contained 24 isolates from Iran and nine from other countries. Three common BPTs with two, seven and 15 isolates were found among Iranian strains only and one common BPT with two isolates was found among non-Iranian strains only. Antibiotic-resistance patterns and virulence properties of strains from these common BPTs suggested that they might be unique clones. Forty-two Iranian isolates shared multi-resistance to between three and seven antibiotics. In contrast, none of the isolates from other countries was resistant to antibiotics. Furthermore, 43 Iranian isolates showed mannose-resistant adhesion to HeLa cells and 24 of them possessed an aerobactin-mediated iron-uptake system, whereas none of the isolates from other countries possessed any of these virulence properties. These findings suggest that four unique clones of Salmonella Havana with different BPTs and virulence properties are common in Iran; two particular clones were responsible for a majority of Havana infections there. However, the most prevalent BPT found among Iranian strains was also common in strains from other countries. It is concluded that biochemical fingerprinting, as used in this study, is a reliable method for identifying clonal groups of Havana strains. The method is reproducible, easy to perform and can be used alone, or in combination with other typing methods, in epidemiological studies of serotype Havana.

Bacterial Adhesion↗

PubMed1992

Evaluation of the PhP system for biochemical-fingerprint typing of strains of Salmonella of serotype Typhimurium.

The Phene Plate (PhP) system of biochemical fingerprinting of bacteria is a computerised typing system, based on quantitative measurements of the kinetics of several biochemical reactions of bacteria grown in liquid medium in microtitration plates. For each isolate tested, it yields a biochemical fingerprint comprising several kinds of quantitative data which are useful for establishing similarities among strains with a personal-computer program. In this study, a set of 16 specific substrates was chosen to differentiate strains of Salmonella of serotype Typhimurium. The system was evaluated for its typability, reproducibility and discriminatory power in tests with a collection of 100 epidemiologically unrelated Typhimurium strains and results were compared with those obtained by phage typing. At an identity level of 0.980, strains were assigned by this method to 51 biochemical phenotypes (BPTs), giving a diversity index of 0.963 and a resolution index of 0.210. In contrast, 24 phage types (PTs) were identified among these isolates (a diversity index of 0.901). The combined use of biochemical fingerprinting by the PhP system and phage typing discriminated 82 phenotypes (a diversity index of 0.994). Stability of markers in each of the methods was also evaluated after subculture of 20 strains for 21 consecutive days. Only nine biochemical reactions were found that were subject to small, but measurable, changes for at least one isolate. These changes slightly decreased the mean similarity coefficients among strains but the overall BPTs of the strains showed changes in four strains (20%). In contrast, eight strains (40%) showed changes in their PTs after this treatment. It is concluded that the PhP system is a highly discriminatory and reproducible method for typing Typhimurium strains. It is easy to perform, and may be used alone or in combination with phage typing in epidemiological studies of Typhimurium strains.

Bacterial Typing Techniques↗

PubMed1992

The use of biochemical fingerprinting, phage typing and antimicrobial-susceptibility testing in the detection of epidemic strains of Salmonella of serotype Typhimurium in Iran.

A collection of 86 strains of Salmonella of serotype Typhimurium isolated from children with gastroenteritis in Tehran, Iran was examined for biochemical phenotype, phage type and antibiotic-resistance pattern. Twenty-seven biochemical phenotypes (BPTs), 14 discrete phage types (PTs) and 18 resistotypes (RTs) were identified. Fifty-three strains (62%) belonged to two major and probably related BPTs, whereas the other 33 isolates belonged to less common BPTs. The two predominant BPTs contained 26 strains of the same PT and 23 strains of the same RT. Different PTs and RTs of strains with similar BPT were sometimes observed, possibly reflecting antibiotic pressures in Iran. These results suggest that two major "clones" of Typhimurium strains are particularly common in Iran and, although each method alone adequately detected these and other less common "clones", biochemical fingerprinting provided additional information about relationships among strains.

Bacterial Typing Techniques↗

PubMed1992

An outbreak of Klebsiella oxytoca septicemias associated with the use of invasive blood pressure monitoring equipment.

Seven cases of septicemia with piperacillin-resistant Klebsiella oxytoca (PRKO) occurred at 2-monthly intervals in a thoracic surgery intensive care unit. All PRKO isolates were serotyped, and phenotyped with a biochemical typing system. Only one patient in the unit was found to be colonized in stool or respiratory tract with PRKO, and this strain was different from the septicemia strains in phenotype though not in serotype. Environmental cultures, from humidifiers, oxygenators, pressure transducers, etc. were negative. PRKO of the epidemic phenotype was recovered from several non-patient transducer domes. The outbreak ended when transducer heads were disinfected and the use of non-patient domes was abolished.

Adult↗

PubMed1992

Biochemical fingerprinting of urinary Escherichia coli causing recurrent infections in women with pyelonephritic renal scarring.

A biochemical fingerprinting system, especially designed for subtyping of Escherichia coli and suitable for screening large number of bacterial strains was used in a long-term follow-up study of 19 women with non-obstructive pyelonephritic renal scarring and recurrent urinary infections in order to examine whether recurrent infections mostly are relapses or reinfections in this group of patients. Seventy-six recurrent infections occurred during a 47-month follow-up (0.09 infections per observation month). The majority of the recurrences were reinfections (58/76, 76%) and 18 (24%) were relapses caused by E. coli. Approximately 50% of relapses and reinfections caused by E. coli were symptomatic while the majority of reinfections caused by other bacteria were asymptomatic (23/30, 77%). In one patient a relapse of E. coli infection occurred more than two years (745 days) after the initial infection. Reinfections may occur early (7 days) after cessation of antimicrobial therapy in this group of patients. Two patients had an episode of symptomatic bacteriuria 51 and 56 days after asymptomatic bacteriuria with the same E. coli strain was detected. Biochemical fingerprinting of the E. coli isolates revealed that they belong to a wide variety of biochemical phenotypes which indicates that they are not members of widespread uropathogenic clones.

Adult↗

PubMed1992

Urinary Escherichia coli causing recurrent infections--a prospective follow-up of biochemical phenotypes.

Twenty-three women with non-obstructive acute pyelonephritis due to Escherichia coli were prospectively studied during 880 patient months, mean observation time 38 months. Each patient had between 1 and 4 new episodes of E. coli bacteriuria during the study period (altogether 49 recurrencies). All E. coli isolates were typed by biochemical fingerprinting. Twenty-six of the recurrencies were caused by an E. coli strain identical to one of those that had previously appeared. Sixteen of these infections were caused by a strain identical to the one that gave rise to the original acute pyelonephritis. Ten further recurrencies were due to an E. coli strain that had previously caused symptomatic or asymptomatic bacteriuria during the observation period. Despite appropriate treatment and repeated negative urine cultures post-treatment, infections caused by identical E. coli strains occurred up to 35 months after the initial episode of acute pyelonephritis. We suggest that the infecting E. coli strain may survive in the fecal flora or is harboured in the patient's surroundings, and after recolonizing the patient, these strains may give rise to further urinary tract infections.

Adult↗

PubMed1992

Nationwide spread of Klebsiella oxytoca K55 in Swedish neonatal special care wards.

In a nationwide survey of invasive bacterial infections in Swedish neonates, 36% of Klebsiella spp. were Klebsiella oxytoca serotype K55. This unexpectedly high proportion of K55 infections was due to clusters of infection in neonatal special care wards, and at first seemed attributable to nosocomial spread of a K. oxytoca strain of high virulence. Factors predisposing infants to infection were, however, found irrespective of whether the infecting strain was of serotype K55 or not. Additionally, the prevalence rates of a potential virulence factor, siderophore production, were similar among the two groups of strains. During the same period of time a K. oxytoca K55 with similar biochemical phenotype and drug resistance pattern was found to be spread among the neonates in 12 of 22 neonatal wards in Sweden. The increased proportion of invasive neonatal K. oxytoca K55 infections thus seemed to reflect a high rate of colonization rather than an increased virulence of the K55 strain.

Disease Outbreaks↗

PubMed1991

The use of the PhP-KE biochemical fingerprinting system in epidemiological studies of faecal Enterobacter cloacae strains from infants in Swedish neonatal wards.

The PhenePlate (PhP) biochemical fingerprinting system is an automated method for typing of bacteria, based on the evaluation of the kinetics of biochemical reactions, performed in microtitre plates. In the present study the PhP-Klebsiella/Enterobacter (KE) system was evaluated for typing of Enterobacter cloacae and employed to study the epidemiology of faecal E. cloacae strains isolated from infants in 22 Swedish neonatal wards. The PhP-KE system showed a high reproducibility and discrimination for E. cloacae isolates. Among 64 epidemiologically unrelated E. cloacae strains, 49 distinct phenotypes were found, and the diversity index was 0.985. E. cloacae was found as a part of the dominating Gram-negative aerobic bacterial flora in 83 out of 953 infants studied. The incidences of E. cloacae colonization varied between 0 and 35% in different wards, but in contrast to previous data for Klebsiella spp. and Escherichia coli, there was little evidence of spread of particular strains in the wards. We also discuss two different measures of nosocomial transmission of bacterial strains: transmissible strains and epidemic index.

Bacterial Typing Techniques↗

PubMed1991

Biochemical phenotypes of enteropathogenic Escherichia coli common to Iran and Sweden.

A collection of 143 strains of enteropathogenic Escherichia coli (EPEC) of 11 different serogroups isolated from children with diarrhoea, 71 in Sweden and 72 in Iran, was tested for similarity with a computerised biochemical fingerprinting method. From Sweden, there were 54 different phenotypes, 42 consisting of a single strain and 12 (common phenotypes) containing more than one isolate. From Iran, there were 48 different phenotypes, 38 with only one strain and 10 with more than one. Many of the strains which were biochemically similar, in both countries, also had similar virulence factors. Nine Swedish and 20 Iranian isolates showed biochemical identity to at least one of the strains of the other country, most of them belonging to serogroups O55, O119, O126, O127 and O128. The value of the biochemical fingerprinting method as an epidemiological tool and its ability to evaluate clonal relations among E. coli strains in different geographical areas is discussed.

Adhesins, Escherichia coli↗

PubMed1991

Biochemical fingerprinting of water coliform bacteria, a new method for measuring phenotypic diversity and for comparing different bacterial populations.

A simple, automated microplate system for biochemical characterization of water isolates can be used to obtain fingerprints of the bacterial flora from various water samples. Mathematical models for calculating the diversities and similarities between bacterial populations are described for such fingerprints. The diversity may give information on whether an indigenous or allochthonous flora is present, and the similarities between bacterial populations, as calculated by using a population similarity coefficient (Sp), may indicate contaminations between different water samples. The system was demonstrated on coliform bacterial populations from various water samples, with or without suspected intercontamination. For unrelated water samples, the Sps were close to 0, whereas repeated samples of the same source showed Sps of 0.64 to 0.74. The Sp values from several water samples were also clustered to form a dendrogram, thus indicating the relative similarities between the bacterial populations to confirm suspected common sources of pollution.

Bacterial Typing Techniques↗

PubMed1991

Characterization of Escherichia coli isolated in blood, urine and faeces from bacteraemic patients and possible spread of infection.

Blood, faecal and urine isolates from patients with culture-verified E. coli bacteraemia were investigated with respect to biochemical phenotype, O and K serotype and P. fimbriae. In 10/16 bacteraemic episodes, the blood isolates were identical to the corresponding faecal strains. In four of the remaining infections, antimicrobial therapy was initiated more than two days before faecal samples were taken. Urine cultures revealed growth of E. coli in 12/16 samples. However, only three had clinical signs of symptomatic urinary tract infections. Eight of these E. coli were saved. Further analysis revealed that five of eight strains were identical to the corresponding isolates from blood and stool samples, two were only identical to the faecal strain, while one was different to the corresponding E. coli in the blood and stool samples. The isolated E. coli strains belonged to varying and, among previously healthy persons, normally less common serotypes. No epidemiological relationship was observed between the studied strains. The high incidence of identical strains in the blood, stool and urine indicates a bacterial spread from the faecal flora directly to the urine and possibly also, via the blood, to the urine.

Bacteriuria↗

PubMed1991

Characterization of beta-lactam-resistant Klebsiella oxytoca isolated in a neonatal intensive care unit.

The occurrence of Klebsiella oxytoca resistant to ampicillin, piperacillin, aztreonam and cefuroxime in a neonatal intensive care unit, including two cases of septicemia, was shown to consist of a spread on three consecutive occasions caused by three different biochemical Klebsiella oxytoca phenotypes. All isolates, except six surface isolates from one infant belonging to phenotype 1, were sensitive to cefotaxime (MIC 0.5-4 mg/l) and ceftazidime (MIC 0.25-1 mg/l). Isolates of phenotypes 1 and 2 produced a beta-lactamase with an isoelectric point of 5.5 and isolates of phenotype 3, a beta-lactamase with an isoelectric point of 7.9. The beta-lactamases of all three phenotypes hydrolysed benzylpenicillin and more slowly cephalothin. All phenotype 1 isolates carried a 2.9 Md plasmid and most isolates also a 36 Md plasmid. All phenotype 2 isolates carried a 4.8 Md plasmid and one isolate also a 30 Md plasmid. The phenotype 3 isolates carried only one 85 Md plasmid.

Animals↗