Biomedical subjects

K Dietz

Publications and source records attributed to K Dietz.

At least 73 records · Page 4Linked to original sources

PubMed2000

Risk factors for treatment failures in patients receiving PCR-based preemptive therapy for CMV infection.

PCR-based preemptive therapy with ganciclovir has been shown to reduce the incidence of CMV disease after BMT. Failures of this treatment strategy are CMV disease and secondary non-viral infections. Eighty-six consecutive patients at high risk for CMV disease who received PCR-based preemptive therapy with ganciclovir were assessed for treatment failures and possible risk factors. Ganciclovir was initiated in 57 of 86 patients (66%). Only 28 of 86 (32%) patients received 4 or more weeks of ganciclovir. Recurrence of CMV infection after successful treatment was more frequent among recipients of a BMT from an unrelated compared to a sibling donor (P = 0.004). Three (3.5%) patients developed non-fatal early onset CMV disease and seven of 68 (10.3 %) late onset CMV disease (>100 days post transplant). Risk factors for late onset CMV disease were cGVHD (P = 0.0017) and duration of prior antiviral therapy >4 weeks (P = 0. 0073). The incidence of secondary non-viral infections was 28% with the duration of antiviral treatment being a significant risk factor for secondary bacterial (P = 0.0045) and invasive fungal infections (P = 0.006). Thus, PCR-based preemptive treatment with ganciclovir reduces early onset CMV disease, but the duration of antiviral therapy prior to day +100 is a significant risk factor for late onset CMV disease as well as secondary non-viral infections.

Adolescent↗

PubMed2000

[Are cross-eyed persons worse drivers? The effect of stereoscopic disparity on driving skills].

BACKGROUND: The motorist obtains about 90% of the information required to drive a vehicle from the sense of vision. In road traffic, various situations with respect to size, distance, and position have to be evaluated at different speeds. Does depth perception based on disparity play an essential role in these situations? METHODS: Each of ten subjects with defective stereopsis due to strabismus was compared with an age matched healthy control, who was also matched in yearly mileage, type of vehicle and duration of driving experience. After ophthalmological examination including stereotests for both distance and near, all subjects performed the following driving tests: (1) Stopping as close as possible in front of an obstacle, (2) reversing into a parking position, (3) driving a slalom parcours at the speed of 40 km/h, (4) estimating the relative position of two cars within a limited time while approaching them with 40 km/h. All tests were performed both under monocular (the non-leading eye covered) and binocular conditions. The sequence of the tests was randomized in order to minimize training effects. RESULTS: Comparing the driving performance of both groups, the controls performed significantly better (p < 0.01; ANOVA) only in the "slalom task". In "estimation of position" the controls performed significantly worse (p < 0.01; ANOVA) compared to their counterparts with defective stereopsis. A significant difference between the monocular and binocular performance was found only in the "stopping task", exclusively for the group of normals, benefitting from the binocular performance (p < 0.05; ANOVA). CONCLUSION: Stereopsis improves the driving performance only in dynamic situations at intermediate distances.

Adult↗

PubMed2000

[Influence of histopathological factors on dynamic MR mammography].

AIM: To assess the histopathological background of enhancement mechanisms in dynamic MR mammography studies. METHODS: The dynamic MR mammography (MRM) examinations were done with a 1.5 T MR imager (Magnetom Vision, Siemens) using a double breast coil and a coronal FLASH-3D sequence. Enhancement data were acquired during 9 minutes post contrast medium injection (Gd-DTPA 0.2 mmol/kg). Acquisition time was 87 sec/slab. Early enhancement at the first post contrast measurement (E1) and slope of wash-out (SE2-L) were calculated. In immunohistology, proliferation was assessed by the monoclonal antibody Ki 67, capillaries were stained by a CD 31 antibody. Of a total of 48 operated patients, 58 lesions and 46 surrounding tissues were evaluated. RESULTS: Cellularity, capillary density and proliferation showed statistically significant correlations with E1 (p < 0.01). In multiple regression analysis, E1 was significantly associated only with high cellularity (p = 0.002) and the combination of high cellularity and high microvessel density (p = 0.002); a negative slope of wash out was significantly associated only with malignant histology (p = 0.027). CONCLUSIONS: Our findings indicate a direct influence of cellularity and microvessel density on early enhancement. The expression of the proliferation marker Ki 67 was not an independent predictor for contrast enhancement.

Adult↗

PubMed2000

Placental transfer and decay of maternally acquired antimeasles antibodies in Nigerian children.

BACKGROUND: In developing countries vaccination against measles virus (MV) is generally administered at 9 months of age, although it is well-documented that protection of most infants by passively acquired maternal MV antibodies is waning before immunization is given. The purpose of this study was to investigate the decay of maternally derived MV antibodies in Nigerian infants as well as to compare a German and Nigerian cohort of paired mothers and newborns regarding the placental transfer efficiency of MV-specific IgG and total IgG antibodies. METHODS: MV-specific IgG antibodies were measured with a commercially available MV-enzyme-linked immunosorbent assay, a recombinant hemagglutinin enzyme-linked immunosorbent assay as well as a neutralization assay. Total IgG values were determined with a standard immunoturbidimetric test. RESULTS: Anti-MV IgG titers were twice as high in German newborns as in Nigerian newborns. An increased concentration of immunoglobulins transferred via the placenta was found only in the German cohort. High concentrations of total maternal IgG reduced the concentration of MV-specific as well as total IgG that crossed the placenta. Furthermore only 17% of the 4-month-old Nigerian infants were still protected against measles. Antibodies had a biologic half-life of 33 days and a biochemical half-life of 48 days. CONCLUSIONS: Our findings demonstrate that the decay of passively acquired MV antibodies occurred even more rapidly than expected resulting in susceptibility to MV in most of the 4-month-old infants in Nigeria. Furthermore transfer of maternal anti-MV IgG and total IgG antibodies to the newborn was more efficient in the German cohort compared with the Nigerian group. These findings suggest the use of alternative vaccination strategies in developing countries to possibly reduce the window of susceptibility against measles.

Adult↗

PubMed2000

Influence of Acanthamoeba castellanii on intracellular growth of different Legionella species in human monocytes.

Previous studies using a murine model of coinhalation of Legionella pneumophila and Hartmannella vermiformis have shown a significantly enhanced intrapulmonary growth of L. pneumophila in comparison to inhalation of legionellae alone (J. Brieland, M. McClain, L. Heath, C. Chrisp, G. Huffnagle, M. LeGendre, M. Hurley, J. Fantone, and C. Engleberg, Infect. Immun. 64:2449-2456, 1996). In this study, we introduce an in vitro coculture model of legionellae, Mono Mac 6 cells (MM6) and Acanthamoeba castellanii, using a cell culture chamber system which separates both cell types by a microporous polycarbonate membrane impervious to bacteria, amoebae, and human cells. Whereas L. pneumophila has shown a maximal 4-log-unit multiplication within MM6, which could not be further increased by coculture with Acanthamoeba castellanii, significantly enhanced replication of L. gormanii, L. micdadei, L. steigerwaltii, L. longbeachae, and L. dumoffii was seen after coculture with amoebae. This effect was seen only with uninfected amoebae, not with Legionella-infected amoebae. The supporting effect for intracellular multiplication in MM6 could be reproduced in part by addition of a cell-free coculture supernatant obtained from a coincubation experiment with uninfected A. castellanii and Legionella-infected MM6, suggesting that amoeba-derived effector molecules are involved in this phenomenon. This coculture model allows investigations of molecular and biochemical mechanisms which are responsible for the enhancement of intracellular multiplication of legionellae in monocytic cells after interaction with amoebae.

Acanthamoeba↗

PubMed2000

Malariometric update for the rainforest and savanna of Ashanti region, Ghana.

The epidemiological features of human infection with Plasmodium were studied in a community-based survey of 35 villages in the Ashanti region of Ghana. The overall prevalences of malarial parasitaemia in subjects aged > or = 2 years were 50.72% in forest areas and 49.72% in savanna. Plasmodium falciparum was the predominant species everywhere, followed by P. malariae in the savanna and P. ovale in the forest. The highest prevalence of asexual parasitaemia (of any species) occurred in the youngest age-group (2-9 years). The geometric mean intensities of parasitaemia among the parasitaemic (i.e. the parasite density indices) were 557, 640 and 452 parasites/microliter for P. falciparum, P. ovale and P. malariae, respectively. For each Plasmodium species encountered, the mean intensity of parasitaemia decreased with age. Mixed infections were observed in 24% and 30% of the parasitaemic subjects from the forest and savanna, respectively. Those infected with P. falciparum were more likely to carry P. ovale (odds ratio = 2.02) or P. malariae (odds ratio = 2.63) than those who were not infected with P. falciparum. Mean intensities of the parasitaemias in mixed infections were substantially higher than the sums of those in the corresponding single infections. When comparing villages, parasite density indices were found to be correlated with the prevalences of parasitaemia (r = 0.56).

Adolescent↗

PubMed1999

Protective effect of Crataegus oxyacantha against reperfusion arrhythmias after global no-flow ischemia in the rat heart.

The protective effect against reperfusion arrhythmias of a 3-month oral pretreatment with a dried extract of Crataegus oxyacantha (LI 132)(standardized to 2.2% flavonoids) was studied with the Langendorff heart of the rat after global no-flow ischemia. The heart was perfused with a modified Krebs-Henseleit solution in which the K+ content was reduced to 3.4 mmol/l in order to lower the fibrillation threshold. According to pilot experiments which considered various durations of global no-flow ischemia ranging from 10 to 20 minutes, two durations were chosen for the present study: 20 minutes (group 20) in which ventricular fibrillation (VF) was the predominant form of arrhythmias, and 18 minutes (group 18) in which the prevalence of VF was markedly lower despite the small difference in the duration of ischemia. Crataegus pretreatment significantly (p = 0.02) reduced the average prevalence of malignant arrhythmias (VF + Flutter) as observed during the 20-min-period of reperfusion as follows: group 20: from 89% (control, n = 9) to 51% (LI 132, n = 7), group 18: from 48% (control, n = 8) to 8% (LI 132, n = 8). In group 20, ventricular tachycardia (VT) could be observed only in the treated group, because of the predominance of VF in the control group. LI 132 pretreatment reduced the average prevalence of VT in group 18 in spite of the identical percentage of occurrence (6 out of 8 rats, with and without treatment) due to a shorter duration of the VT episodes. Thus, under the conditions of our experiments, effective prevention against reperfusion arrhythmias by Crataegus pretreatment was evident.

Animals↗

PubMed1999

Mortality in blind subjects. A population-based study on social security files from Baden-Württemberg.

BACKGROUND: Previous studies indicated that mortality is increased in blind subjects. However, no detailed analysis with respect to causes of blindness and the effect of additional diseases has been performed. The present study was undertaken to examine these questions. MATERIALS AND METHODS: The investigation is based on social security files from the Württemberg-Hohenzollern region (population 5.5 millions) in Germany. In total, 571 files of blind subjects whose blindness benefits terminated (mostly due to death) in 1994 were included. Medical opinions on ophthalmological status and general health were extracted from the files. Standardised mortality ratios (SMRs) on the basis of life tables of former West Germany were calculated using maximum likelihood methods taking into account censoring. RESULTS: Most subjects in our study had one or more additional diseases at onset of blindness (74%). The SMR in all blind is 1.41 [95% CI (confidence interval) = 1.28-1.54; n= 571]. Mortality of blind subjects is increased if subjects suffer from multiple disease at onset of blindness: the SMR in blind with multiple diseases is 1.76 (95% CI = 1.58-1.94; n = 421) versus 0.85 (CI = 0.70-1.0; n = 150) in otherwise healthy blind subjects. In cases where specifically ocular diseases were responsible for the visual loss, the symbol [M] indicates that the blind subject suffered from multiple disease at onset of blindness and [E] denotes that this was not the case. The SMRs for main causes of blindness are: macular degeneration [M] 1.5 (CI = 1.3-1.8; n = 123), [E] 1.1 (CI = 0.8-1.5; n = 43); glaucoma [M] 1.6 (CI = 1.3-2.1; n = 65), [E] 1.0 (CI = 0.6-1.5; n = 26); high myopia [M] 1.2 (CI = 0.8-1.7; n = 32), [E] 0.8 (CI = 0.5-1.2; n = 21); optic atrophy [M] 1.1 (CI = 0. 6-1.8; n = 19), [E] 1.4 (CI = 0.4-3.2; n = 4), and tapetoretinal degeneration [M] 2.3 (CI = 1.1- 4.2; n = 10), [E] 0.9 (CI = 0.4-1.8; n = 12). The SMR of cases of blindness in conjunction with other diseases was fairly high for diabetic retinopathy: 5.5 (CI = 4.4-6. 8; n = 81). Central-nervous-system-triggered blindness led to an SMR of 1.5 (CI = 1.0-2.2; n = 37). DISCUSSION: According to the results of the present study mortality is significantly increased in blind subjects. However, increased mortality in cases of blindness due to specifically ocular disease (e.g. macular degeneration) is associated with the presence of multiple (extra-ocular) diseases at onset of blindness.

Adolescent↗

PubMed1999

Review of intra-host models of malaria.

Intra-host models of malaria (and some related models of trypanosomiasis) are reviewed. A first section gives a short description of the different models, their purposes and the authors' conclusions. A second section discusses some common issues, including intra-host populations, the intra-host basic reproduction number (R0) and growth rates, density regulation mechanisms (including acquired immunity), and the models' behaviour compared to that of Plasmodium falciparum in man.

Animals↗

PubMed1998

Cleavage motifs of the yeast 20S proteasome beta subunits deduced from digests of enolase 1.

The 436-amino acid protein enolase 1 from yeast was degraded in vitro by purified wild-type and mutant yeast 20S proteasome particles. Analysis of the cleavage products at different times revealed a processive degradation mechanism and a length distribution of fragments ranging from 3 to 25 amino acids with an average length of 7 to 8 amino acids. Surprisingly, the average fragment length was very similar between wild-type and mutant 20S proteasomes with reduced numbers of active sites. This implies that the fragment length is not influenced by the distance between the active sites, as previously postulated. A detailed analysis of the cleavages also allowed the identification of certain amino acid characteristics in positions flanking the cleavage site that guide the selection of the P1 residues by the three active beta subunits. Because yeast and mammalian proteasomes are highly homologous, similar cleavage motifs might be used by mammalian proteasomes. Therefore, our data provide a basis for predicting proteasomal degradation products from which peptides are sampled by major histocompatibility complex class I molecules for presentation to cytotoxic T cells.

Amino Acid Sequence↗

PubMed1998

The effect of pair formation and variable infectivity on the spread of an infection without recovery.

For the spread of an infection without recovery we compare the properties of a model in which contacts are assumed to be instantaneous and every contact is with a new partner to a model with an explicit description of partnership formation and duration. We investigate the dynamic behaviour at the beginning of the epidemic, the exponential growth phase and the endemic equilibrium in a population with a simple demographic process. Comparisons are made with the assumption that the basic reproduction ratio R0 is equal for both models. In a second step we introduce variable infectivity into both models and investigate how that interacts with the process of pair formation and partnership duration. The main results are: If partnership duration is taken into account, then (a) the prevalence may initially decrease, even if R0 > 1; (b) the exponential growth rate is lower than in a model without partnership duration; (c) the endemic equilibrium is higher than in a model without partnership duration. Furthermore we show that for a model with positive partnership duration for one value of R0 one might have more than one corresponding epidemic growth rate and endemic steady state. This implies that one cannot estimate R0 from the endemic level without further information on the partnership process. Finally we demonstrate that even for a very low value of per contact infectivity in the second stage of infection, as has been postulated for HIV-infection, transmission during the second stage may contribute significantly to the spread of the epidemic due to the long duration of the second stage. Therefore, reduction of the high infectivity in the short first stage of infection only affects R0 markedly if average partnership duration is short.

Acquired Immunodeficiency Syndrome↗

PubMed1998

Heterogeneities in schistosome transmission dynamics and control.

We review the theoretical framework for exploring the impact of individual and spatial heterogeneities in patterns of exposure and contamination and on the basic reproduction number, R0, for human schistosomes. Analysis of water contact data for 5 communities in Zimbabwe and Mali suggests that the impact is substantial, increasing R0 by factors of up to 6.5, mostly due to highly overdispersed distributions of contact rates among individuals. Several practical conclusions emerge: concentration of contacts at a single site should be avoided; the impact of control targeted at certain sites cannot be predicted without knowledge of how individuals' contacts are distributed among sites; control programmes targeted at individuals or sites contributing most to transmission can be very efficient but, conversely, will be ineffective if any of these individuals or sites are missed.

Animals↗

PubMed1998

Pharmacokinetics of clozapine and its metabolites in psychiatric patients: plasma protein binding and renal clearance.

AIMS: N-Desmethylclozapine and clozapine N-oxide are major metabolites of the atypical neuroleptic clozapine in humans and undergo renal excretion. The aim of this study was to investigate to what extent the elimination of these metabolites in urine contributes to the total fate of clozapine in patients and how they are handled by the kidney. METHODS: From 15 psychiatric patients on continuous clozapine monotherapy, blood and urine samples were obtained during four 2 h intervals, and clozapine and its metabolites were assayed in serum and urine by solid-phase extraction and h.p.l.c. Unbound fractions of the compounds were measured by equilibrium dialysis. RESULTS: The following unbound fractions in serum were found (geometric means): clozapine 5.5%, N-desmethylclozapine 9.7%, and clozapine N-oxide 24.6%. Renal clearance values calculated from unbound concentrations in serum and quantities excreted in urine were for clozapine on average 11% of the creatinine clearance, whereas those of N-desmethylclozapine and clozapine N-oxide amounted to 300 and 640%, respectively. The clearances of unbound clozapine and N-desmethylclozapine increased with increasing urine volume and decreasing pH. All renal clearance values exhibited large interindividual variations. The sum of clozapine and its metabolites in urine represented on average 14% of the dose. CONCLUSIONS: Clozapine, N-desmethylclozapine and clozapine N-oxide are highly protein-bound in serum. Clozapine is, after glomerular filtration, largely reabsorbed in the tubule, whereas the metabolites undergo net tubular secretion. Metabolic pathways alternative or subsequent to N-demethylation and N-oxidation must make major contributions to the total fate of clozapine in patients.

Adult↗

PubMed1998

The protective effect of condoms and nonoxynol-9 against HIV infection.

OBJECTIVES: Whether or not spermicides can reduce the risk of human immunodeficiency virus (HIV) transmission remains an important question for the control of heterosexual HIV transmission. The authors provide estimates from a reanalysis of one of the few observational studies on the efficacy of condoms and spermicides, used separately and together, per vaginal contact. METHODS: In this reanalysis, three different models were used to assess the efficacy of spermicides and condoms: linear (Pearl index), exponential (maximum likelihood), and monotonic (marginal likelihood). RESULTS: Reported use of barrier methods among 27,432 contacts was as follows: condoms plus nonoxynol-9, 39%; condoms alone, 25%; nonoxynol-9 alone, 24%; and unprotected, 11%. Under all three models, the results indicate a strong protective effect for spermicidal suppositories. The Pearl index indicated that spermicide alone is apparently efficacious, but the efficacy per contact cannot be quantified with this approach. Maximum likelihood estimates for the efficacy of nonoxynol-9 alone and condoms (with or without nonoxynol-9) were 100% (95% confidence interval [CI95] = 43%, 100%) and 92% (95% CI95 = 79%, 100%), respectively. CONCLUSIONS: The data from this observational study suggest that spermicides may be efficacious in reducing the risk of HIV transmission.

Administration, Intravaginal↗

PubMed1997

Analysis of a model for the pathogenesis of AIDS.

According to a previously proposed mathematical model, the pathogenesis of acquired immunodeficiency syndrome (AIDS) could be explained by two phenomena: direct human immunodeficiency virus (HIV) infection of CD4+ T-cell populations and ongoing generation and selection of HIV mutants with increasing replicative capacity. In the present paper, the results obtained with this model are described in more detail. For different values of biologically interpretable parameters, the model predicts very different patterns of CD4+ T-cell decline after primary infection. With the assumption of a variability of 10% to 25% of three parameters between infected individuals, the model yields a realistic distribution curve of the incubation period to AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Prolongation of life span in hypertensive rats by dietary interventions. Effects of garlic and linseed oil.

The effects of long-term dietary application of garlic (dried powder, 0.5% in weight of standard chow; G group) or linseed oil (2.5%; L group) as well as a combination of both interventions (L + G group) on the life span of hypertensive rats (SHR SP) was investigated. A further group fed with standard chow served as control (C). The dietary interventions were started at the age of three weeks. Besides regular measurements of the systolic arterial blood pressure (oscillometrically at the tail artery) as well as of heart rate and body weight, autopsy and histological investigations were performed. Both diets, and particularly their combination, prolonged life span significantly (mean values (days) C: 434.5 +/- 23.5; G: 453.2 +/- 16.2; L: 470.0 +/- 26.2; L + G: 494.8 +/- 39.2). There was no significant interaction of the factors garlic and linseed oil. Systolic blood pressure as measured during the compensatory stage (data used until the 39th week of life) was significantly lowered by both garlic (mean -5.8 mm Hg), linseed oil (mean -6.3 mm Hg), and their combination (mean -11.3 mm Hg). The animals died as a consequence of congestive left and right ventricular failure with ventricular hypertrophy, dilatation, myocardial fibrosis and cellular infiltration, left ventricular atrial thrombosis (in most cases), and terminal pneumonia. On the other hand, arteriosclerotic plaques and signs of cerebral stroke could not be detected. Except for the degree of hypertrophy, which was lower in the treated groups, no differences were obvious regarding the morphological findings at the time of death. There was a significant positive correlation between mean blood pressure and the degree of left ventricular hypertrophy. Furthermore, a significant negative correlation between mean blood pressure and ventricular hypertrophy on the one hand and survival on the other hand was obvious provided the total number of animals was considered, however, not within the individual groups. The same applies to the relation between the reduction of left ventricular hypertrophy and life span. The relatively slight hypotensive effect of both dietary interventions as well as the results of previous investigations speaks in favor of a substantial influence of factors independent of blood pressure. In view of controversial results and interpretations in international literature, the mechanisms involved need further study.

Animals↗

PubMed1997

Exchange blood transfusion in severe falciparum malaria: retrospective evaluation of 61 patients treated with, compared to 63 patients treated without, exchange transfusion.

The rationale for exchange blood transfusion (ET) in severe falciparum malaria is threefold: reduction of parasitaemia, reduction of presumptive 'toxic' factors, and improvement of the rheological quality of the blood. We evaluated the records of 61 patients treated with ET to describe the present status of malaria treatment in Germany, Austria and Switzerland and to assess the efficacy of ET. Clinical data of 61 patients treated with ET were compared to data of 63 patients treated in 2 hospitals where ETs were generally not performed. We found that exchange transfusion is applied according to the clinician's subjective impression rather than strict guidelines. Logistic regression analysis adjusting for the differences in clinical parameters between patients treated with or without ET did not identify treatment as a prognostic indicator (odds ratio for relative risk of death with ET: 1.3; 95% CI: 0.4-4.9). Exchange transfusion did not significantly improve the unfavourable prognosis in cases of severe falciparum malaria. However, failure to reach statistical significance may be due to the retrospective design of the study and therefore non-systematic approach.

Adult↗

PubMed1997

Multiplication of different Legionella species in Mono Mac 6 cells and in Acanthamoeba castellanii.

Survival and distribution of legionellae in the environment are assumed to be associated with their multiplication in amoebae, whereas the ability to multiply in macrophages is usually regarded to correspond to pathogenicity. Since most investigations focused on Legionella pneumophila serogroup 1, we examined the intracellular multiplication of different Legionella species in Mono Mac 6 cells, which express phenotypic and functional features of mature monocytes, and in Acanthamoeba castellanii, an environmental host of Legionella spp. According to the bacterial doubling time in Mono Mac 6 cells and in A. castellanii, seven clusters of legionellae could be defined which could be split further with regard to finer differences. L. longbeachae serogroup 1, L. jordanis, and L. anisa were not able to multiply in either A. castellanii or Mono Mac 6 cells and are members of the first cluster. L. dumoffi did not multiply in Mono Mac 6 cells but showed a delayed multiplication in A. castellanii 72 h after infection and is the only member of the second cluster. L. steigerwaltii, L. gormanii, L. pneumophila serogroup 6 ATCC 33215, L. bozemanii, and L. micdadei showed a stable bacterial count in Mono Mac 6 cells after infection but a decreasing count in amoebae. They can be regarded as members of the third cluster. As the only member of the fourth cluster, L. oakridgensis was able to multiply slight in Mono Mac 6 cells but was killed within amoebae. A strain of L. pneumophila serogroup 1 Philadelphia obtained after 30 passages on SMH agar and a strain of L. pneumophila serogroup 1 Philadelphia obtained after intraperitoneal growth in guinea pigs are members of the fifth cluster, which showed multiplication in Mono Mac 6 cells but a decrease of bacterial counts in A. castellanii. The sixth cluster is characterized by intracellular multiplication in both host cell systems and consists of several strains of L. pneumophila serogroup 1 Philadelphia, a strain of L. pneumophila serogroup 2, and a fresh clinical isolate of L. pneumophila serogroup 6. Members of the seventh cluster are a strain of agar-adapted L. pneumophila serogroup 1 Bellingham and a strain of L. pneumophila serogroup 1 Bellingham which was passaged fewer than three times on BCYE alpha agar after inoculation and intraperitoneal growth in guinea pigs. In comparison to members of the sixth cluster, both strains showed a slightly enhanced multiplication in Mono Mac 6 cells but a reduced multiplication in amoebae. From our investigations, we could demonstrate a correlation between prevalence of a given Legionella species and their intracellular multiplication in Mono Mac 6 cells. Multiplication of members of the genus Legionella in A. castellanii seems to be dependent on mechanisms different from those in monocytes.

Acanthamoeba↗