Impact of basic soil parameters on pesticide disappearance investigated by multivariate partial least square regression and statistics

Dissipation time is a key parameter when studying and modeling the environmental fate of pesticides. This study was conducted to characterize the variability of pesticide disappearance in soil and to identify possible controlling parameters related to intrinsic soil properties and microbiology. Multivariate data analysis was used to study spatial variability in three horizons from 24 sandy soil profiles. The time for 50% disappearance (DT(50)) was characterized for two herbicides, metribuzin (MBZ) and MCPA, and methyltriazine amine (MTA; transformation product of metsulfuron-methyl, tribenuron-methyl, thifensulfuron-methyl, and chlorsulfuron). Normal and log-normal distributions were compared for DT(50) and soil properties and descriptive statistics were calculated. Conformity with log-transformed distributions was observed and assuming normality of the DT(50) data would cause 5 to 35% overestimation. Mean DT(50) were: MCPA 9.5, MBZ 168, and MTA 127. Significant effect of soil depth on DT(50) was shown for MCPA and MBZ, with low values in deeper horizons. Simple linear correlation for combinations of MCPA, MTA, pH, and total organic carbon (TOC) was observed. Using partial least squares regression (PLS) 71 to 85% of the total DT(50) variance was explained. A specific predictor variable could not be identified as the controlling components differed within horizons and compounds. For MCPA the overall important predictor variables were microbiology and TOC, whereas for MTA and MBZ it was inorganic variables (Al, Fe, cation exchange capacity, base saturation percent, and pH) and microbiology. The study indicates that PLS generated input data can improve pesticide fate modeling and reduce the uncertainty in dissipation estimation.

Laboratory handling of Helicobacter pylori critically influences the results of in-vitro metronidazole resistance determination

In-vitro metronidazole resistance rates of Helicobacter pylori determined by Etest are high, and the predictive value of metronidazole resistance is low. It was hypothesised that altered laboratory methods could reduce the overestimation of resistance and improve the predictive value of the Etest. Pre-treatment isolates (n = 150) of H. pylori from 150 patients were investigated by Etest with incubation for 72 h. Treatment with metronidazole, tetracycline and bismuth for 10 days failed to eradicate H. pylori in 23 patients. After isolate storage for 3 years, resistance determination results by agar dilution and Etest, with incubation for 72 and 31 h, were compared. The rate of metronidazole resistance was reduced significantly during storage, and instability of resistance was associated significantly with treatment outcome. Isolates that retained in-vitro resistance had significantly (p 0.008) higher treatment failure rates (n = 13; 42%) than isolates that lost resistance (n = 3; 9%). The reproducibility achieved by dual testing with agar dilution and Etest was 41% and 70% for +/- 1 and +/- 2 log2 dilutions, respectively, after incubation for 72 h, and 85% and 92%, respectively, after incubation for 31 h. Thus, the predictive value was improved from 25% to 50% by the altered laboratory conditions (p 0.04). MIC values of 2-8 mg/L signified an intermediate risk of treatment failure.

Association between multiple sclerosis and cystic structures in cerebrospinal fluid

BACKGROUND

The aim of the study was to search for infectious agents in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS).

PATIENTS AND METHODS

CSF from ten patients with the diagnosis relapsing remitting MS and from five controls without MS were examined by transmission electron microscopy (TEM), dark field microscopy (DF), interference contrast microscopy (ICM) and UV-microscopic examination of acridine orange staining (AO). All CSF samples from patients and controls were cultured.

RESULTS

Cystic structures were observed in CSF of all ten patients by AO and TEM. DF revealed eight cyst-positive patients out of nine. One of five control persons had such structures in the CSF; this person had suffered from erythema migrans. Spirochete or rod-like structures emerged after culturing two of the MS patient CSF samples and these structures could be propagated.

CONCLUSION

A significant association of CSF cysts and MS was identified in this small study among residents in a coastal area of southern Norway. The cysts could be of spirochetal origin. Our study may encourage other researchers to study larger patient groups.

Assessment of optimal atmospheric conditions for growth of Helicobacter pylori

The number and diameter of colonies of Helicobacter pylori isolates growing on agar plates were determined to compare five methods that produce a culture atmosphere. No catalyst was applied. No significant difference was found between two hydrogen-based kits that have a different capacity for production of H2. These hydrogen-based methods were significantly better than all others evaluated, including one kit that produces ascorbic acid that binds with oxygen. Growth was significantly improved when the atmosphere outside the plastic incubation jars was enriched with 10% CO2, but carbon dioxide enrichment alone (i.e., no reduction of the oxygen concentration) gave a very poor yield. The colony diameter was a sensitive and reliable measure of atmospheric conditions, as the mean intra- and interobserver difference between repeated readings was < or = 0.1 mm for 82% and < or = 0.2 mm for 95% of the isolates.

Peptic ulcer disease in south Ethiopia is strongly associated with Helicobacter pylori

Helicobacter pylori infection was detected in 93% of 174 patients with a peptic ulcer compared with 63% of 116 patients with normal findings (chi 2 = 37.3; P < 0.001) in a cohort of 834 consecutive patients examined by gastroscopy in Yirga Alem Hospital in south Ethiopia. Fourteen patients were given 14 days' treatment with metronidazole 500 mg t.i.d., doxycycline 100 mg b.i.d. and bismuth subnitrate mixture 150 mg q.i.d. Of 10 patients who returned for follow-up, only 2 patients were free from H. pylori and cured. Nineteen strains of H. pylori from 19 consecutive patients in the same hospital were tested for resistance in vitro against metronidazole, doxycycline and ampicillin. All but 1 were highly resistant to metronidazole; 2 were fully and 14 intermediate resistant against doxycycline. All strains were fully sensitive in vitro to ampicillin. Thus, peptic ulcer was strongly associated with H. pylori in south Ethiopia, but eradication of the infection was hampered by antibiotic resistance.

A simple method for determining metronidazole resistance of Helicobacter pylori

The reliability of methods for determination of Helicobacter pylori resistance to metronidazole has been found to depend upon the incubation time. Because the disk diffusion method is more vulnerable than other methods to prolonged incubation, this method has not been recommended for H. pylori. However, because media designed for rapid growth of H. pylori have been introduced, the time has come to look at the clinical usefulness of this inexpensive and simple method again. The correlation of readings obtained with the E test (AB Biodisk, Solna, Sweden) and Rosco's (Taastrup, Denmark) disk diffusion method for in vitro metronidazole resistance determination for H. pylori with a short incubation time (24 to 31 h) was studied. Plates which could not be read after 24 to 31 h were reincubated for another night. Fifty-seven consecutive clinical strains were tested. Because the rate of regrowth of H. pylori depends upon the age of the colonies inoculated, the reproducibility of resistance test results for young colonies versus old colonies was also studied. Resistance plates could be read after 24 to 31 h of incubation for 28 of 29 strains when the inoculum consisted of young colonies (3 to 4 days old). For these 29 strains, a high correlation (r = -0.937) was found between results obtained with the E test and those obtained with the disk diffusion test. A poorer correlation was found for old colonies (> or = 5 days old) (r = -0.742), which required a prolonged incubation for 8 of 23 strains. In conclusion, short incubation was successfully applied with young colonies. Results obtained with the simple and inexpensive disk diffusion method correlated well with those obtained with the E test.

Risks related to lack of standardization of tests to detect in vitro metronidazole resistance in Helicobacter pylori

The correlation between metronidazole MIC readings obtained in vitro on two different media for two different inoculum dilutions was studied after two, three, and five days of incubation using 20 clinical isolates of Helicobacter pylori. The PDM epsilometer (E test) was used. After two days of incubation, log MIC values on chocolate PDM and Vestfold charcoal medium, a new charcoal medium, showed good correlation. Charcoal media can thus be used for metronidazole sensitivity tests. In terms of double-dilution gradients, prolongation of incubation time from two to three days and change of inoculum dilution from 0.5 to 4 McFarland had little impact when studied separately. However, the combined effect of the two variables was marked. The matching of a sparse inoculum incubated for two days against a heavy inoculum incubated for three days resulted in readings which, for 30% of the pairs, differed by two double-dilution gradients or more. On the other hand, the separate influence of both variables was found to affect the correlation coefficients significantly. Five days of incubation was associated with a poor correlation when the variables on MIC readings was not exposed in a scale of double-dilution gradients because the intervals were too large. For this reason, scales without thresholds are recommended.

Rapid growth of Helicobacter pylori

The ability of six variants of a new charcoal medium and Skirrow's medium to grow Helicobacter pylori in 3 and 5 days was studied using 20 different strains of Helicobacter pylori. The main admixtures for the charcoal media were serum, whole blood, and egg yolk emulsion. For this purpose, serum was significantly better and egg yolk emulsion significantly worse than whole blood. The addition of Iso Vitalex resulted in significantly improved growth on the charcoal media. Skirrow's medium showed very poor performance after three days of incubation and needed a long incubation time.

The epidemiology of blindness and visual loss in Hamar tribesmen of Ethiopia. The role of gender

We conducted a population-based survey in the Hamar tribe of Ethiopia to assess the problem of blindness and ocular morbidity. Blindness was detected in 1.9% of the Hamar. Among the age group 40 and over < 1.0% of men and 13% of women were blind. Women with low vision or blindness comprised 30% of all women while men with low vision or blindness only comprised 8% of men in the age stratum. Cataract is responsible for the excess blindness in women. Even mild visual disability is less common in men. In Hamar society men have two roles: as herders and as warriors. Warriors with visual loss will be less successful in defending themselves. We suggest that Hamar men who develop visual loss have increased mortality compared to women with visual loss. Vision loss in women does not appear to have life-threatening consequences. Cessation of hostilities between the Hamar and their neighbours could, conceivably, lead to an 'increase' in the incidence of vision loss among men.

Community-wide outbreak of Neisseria gonorrhoeae conjunctivitis in Konso district, North Omo administrative region

We describe a large outbreak of severe pustular conjunctivitis due to Neiserria gonorrhoeae. Over 9,000 cases occurred during 8 months in 1987-1988 in one district in North Omo, Ethiopia. Both sexes and all age groups were affected, particularly children under 5 years of age; only a small minority were neonates. Despite a highly successful cure rate for individual cases, the outbreak continued for a number of months. Several epidemiologic approaches were used to monitor the outbreak and identify the mechanism of transmission. The epidemic curve suggested person-to-person transmission. Routine surveillance data showed that there was no concurrent genital gonorrhea outbreak and genital transmission could not explain a community-wide outbreak. In the setting of intense crowding and relative lack of water, peak transmission of illness coincided with two periods following the rains, suggesting that flies were important in transmission. A case-control study identified lack of face-washing as a household risk factor. Eighty seven of one-hundred and forty six (59%) control houses with children were judged to contain children with clean faces, while only 102 of 216 (47%) case households contained children with clean faces (p less than .05). Our recommendations include measures to improve personal hygiene.