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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↗
PubMed1994

Recurrent Escherichia coli bacteraemia--clinical characteristics and bacterial properties.

The aim of the present study was to determine if recurrent bacteraemia due to Escherichia coli might be caused by the same strain in spite of apparently adequate antimicrobial therapy. Eleven patients who, altogether, experienced 24 episodes of E. coli bacteraemia were studied. All had underlying diseases; five biliary-intestinal disease, four were severely immunocompromised and two had urinary tract disorders. During the first bacteraemic episode, nine patients were treated with various combinations of drugs which included gentamicin and two with co-trimoxazole alone. Antibiotic treatment was continued for at least 12 days in each case and all patients were clinically cured. All isolates of E. coli were characterized by biochemical fingerprinting, O and K serotyping, the presence of cell-surface hydrophobicity and production of aerobactin. In two patients, the recurrent infections were due to strains different from those causing the previous episodes. In nine patients who, altogether, had 19 episodes of bacteraemia, the strain of E. coli isolated during the first and all later episodes were identical, according to all tests performed. We suggest that in such circumstances, the infecting strain may remain in the patients' environment and after recolonising the faecal flora may give rise to further infections. It may be, however, that if necessary steps are not taken, the original bacterial focus remains within the same patient so leading to emergence of the infecting strain which may then cause further episodes of bacteraemia.

Adult↗
PubMed1994

Biochemical phenotypes of Salmonella Livingstone isolated from humans, animals and feedstuffs in Sweden.

Salmonella Livingstone is occasionally isolated from humans, animals and feedstuffs in Sweden. To follow the spread of infection and trace the source of isolates, adequate typing methods are needed. We have developed an automated typing system based on biochemical fingerprinting of bacteria (the PhP system) for typing of different Salmonella serotypes. The system measures the kinetics of various biochemical reactions of bacteria grown in liquid medium in microtiter plates and uses numerical techniques to identify biochemical phenotypes (BPTs) among the tested strains. In the present study we used a set of 16 highly discriminatory tests to differentiate strains of Salmonella of serotype Livingstone and evaluated the system for its discriminatory ability using a collection of 34 unrelated human isolates of S. Livingstone. We also used the system to investigate BPTs of 45 Livingstone strains isolated from animals and feedstuffs in Sweden between 1987 and 1991. Altogether 19 different BPTs were found among human isolate giving a diversity index (Di) of 0.930. In contrast, most strains isolated from animals and feedstuffs in Sweden belonged to 2 dominating BPTs (Di = 0.704). One of these contained 17 strains mainly isolated during 1992 whereas the other contained 18 strains isolated between 1987 and 1991. None of the Swedish human isolates were identical to those of animals and feedstuffs. These findings suggest that 2 different BPTs of Salmonella Livingstone strains are particularly common among animals and feedstuffs in Sweden and that they are not related to human cases of enteritis in this country. We also conclude that biochemical fingerprinting with the PhP system is a reliable and highly discriminatory method for detecting epidemic strains of Salmonella Livingstone.

Animal Feed↗
PubMed1993

Determination of ochratoxin A in urine and faeces of swine by high-performance liquid chromatography.

Sensitive methods for the determination of ochratoxin A in urine and faeces of swine are described. The samples were extracted with chloroform at pH < 2, and the extracts were cleaned up by a combination of solid-phase extraction and liquid-liquid partition. High-performance liquid chromatography with fluorescence detection was used for detection and determination. The detection limits were 0.3 ng/ml for urine and 1.5 ng/g for faeces. Recoveries of ochratoxin A from spiked samples of urine and faeces were 93% and 60%, respectively. Because of the low detection limit and the fast and relatively easy performance, the method for the determination of ochratoxin A in urine proved suitable for the estimation of possible contamination of live animals.

Animals↗
PubMed1993

The use of colonization rate and epidemic index as tools to illustrate the epidemiology of faecal Enterobacteriaceae strains in Swedish neonatal wards.

The epidemiology of faecal Gram-negative bacteria was studied in 953 infants from 22 neonatal special care wards in Swedish hospitals. Two complementary methods to measure presumed nosocomial transmission of bacterial strains were used: the prevalence rate of major (M) phenotypes (strains that had colonized at least 10% of the infants in a particular ward) and the epidemic index (Ei) (which measures the probability of isolating identical strains from different infants in a ward). About 1500 strains of the most common species (Klebsiella spp., Escherichia coli and Enterobacter cloacae) were typed by the Phene Plate (PhP) biochemical fingerprinting system, and selected Klebsiella isolates were also typed by K antigen serotyping. Klebsiella spp. showed a high propensity to spread (median Ei 0.034, max 0.234), whereas E. coli (median Ei 0.006, max 0.140) and E. cloacae (median Ei 0.0, max 0.012) were more seldom involved in outbreaks. High total Eis in the wards were correlated with high cephalosporin usage (Rs = -0.56, P < 0.05). A total of about 600 biochemical phenotypes of Enterobacteriaceae strains were isolated from the 953 infants. Most of these were found in only one or a few infants, but 24 M phenotypes belonging to Klebsiella spp. (N = 19), E. coli (N = 4) and E. cloacae (N = 1) had colonized altogether 239 (25%) infants. Klebsiella M phenotypes similar or identical to each other and carrying K antigen 55 were isolated from 108 (11%) infants in eight wards, and were thus responsible for 45% of the M phenotype carrier rate in all studied infants. It is suggested that they represent a clone of Klebsiella with a high ability to multiply and spread in hospital environments.

Colony Count, Microbial↗
PubMed1993

Variations in biochemical phenotypes and phage types of Salmonella enteritidis in Germany 1980-92.

The Phene Plate system for typing Salmonella serotypes (PhP-S) is a simple automated typing method based on biochemical fingerprinting. It gives a quantitative value of the metabolism of various substrates by measuring the speed and intensity of each reaction. The 'biochemical fingerprint' of each isolate is used to calculate similarities among the tested strains with a personal computer program. We used this system to examine a collection of 86 strains of Salmonella enteritidis isolated from human sporadic cases in Germany between 1980 and 1992. Twenty-three biochemical phenotypes (BPTs) consisting of 9 common (C) and 14 single (S) BPTs were identified. BPTs C2 and C4 containing 20 and 36 strains respectively accounted for 65% of the isolates. Strains of BPT C2 were found over a wide period of time whereas strains of BPT C4 were isolated during the period between 1988 and 1992. With phage typing, 11 discrete phage types (PTs) and 18 strains designated as non-specific type (NST) were identified. PTs 4 and 8 with 39 and 17 strains respectively were the dominant PTs. Strains of PT 8 were isolated over a wide period of time whereas all (except one) strains of PT 4 were isolated between 1988 and 1992. Combination of biochemical fingerprinting and phage typing divided the strains into 25 phenotypes (BPT:PTs). Whilst phenotype C2:8 was found over a number of different years, phenotype C4:4 was isolated only between 1988 and 1992. These findings indicate the presence of one persistent and one recently emerged phenotype among S. enteritidis strains in Germany.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Typing Techniques↗
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↗