Airborne enteric bacteria and viruses from spray irrigation with wastewater.

The relationship between bacterial concentrations in wastewater used for spray irrigation and in the air was examined. Aerosolized coliforms were detected when their concentration was 10(3)/ml or more in the wastewater. Relative humidity and solar irradiation appeared to affect viable bacteria in the air; a positive correlation was found between relative humidity and the number of aerosolized bacteria. The correlation between solar irradiation and bacterial level, on the other hand, was negative. During night irrigation, up to 10 times more aerosolized bacteria were detected than with day irrigation. Wind velocity did not play an important role in the survival of aerosolized bacteria. Echovirus 7 was isolated in 4 out of 12 air samples collected 40 m downwind from the sprinkler.     

Airborne enteric bacteria and viruses from spray irrigation with wastewater.

The relationship between bacterial concentrations in wastewater used for spray irrigation and in the air was examined. Aerosolized coliforms were detected when their concentration was 10(3)/ml or more in the wastewater. Relative humidity and solar irradiation appeared to affect viable bacteria in the air; a positive correlation was found between relative humidity and the number of aerosolized bacteria. The correlation between solar irradiation and bacterial level, on the other hand, was negative. During night irrigation, up to 10 times more aerosolized bacteria were detected than with day irrigation. Wind velocity did not play an important role in the survival of aerosolized bacteria. Echovirus 7 was isolated in 4 out of 12 air samples collected 40 m downwind from the sprinkler.     

Salmonella serotypes isolated from human enteric processes in Recife, Pernambuco, during 1978-1980

From 13,196 faecal cultures made in Recife-Pernambuco during the period from 1978 to 1980, 1,720 strains of Salmonella were isolated. Serological typing on 1,387 of the isolates recognized 63 serotypes, 73.18% of which belonged to group B. The prevalent serotypes adding up to 1,231 strains (88.75% of the total of the isolates) were: S. typhimurium, S. saint-paul, S. poona, S. derby, S. agona, S. newport, S. oranienburg, S. infantis, S. tshiongwe and S. ndolo.     

Coexistence of different serotypes of dengue virus

 We formulate a non–linear system of differential equations that models the dynamics of dengue fever. This disease is produced by any of the four serotypes of dengue arbovirus. Each serotype produces permanent immunity to it, but only a certain degree of cross–immunity to heterologous serotypes. In our model we consider the relation between two serotypes. Our interest is to analyze the factors that allow the invasion and persistence of different serotypes in the human population. Analysis of the model reveals the existence of four equilibrium points, which belong to the region of biological interest. One of the equilibrium points corresponds to the disease–free state, the other three equilibria correspond to the two states where just one serotype is present, and the state where both serotypes coexist, respectively. We discuss conditions for the asymptotic stability of equilibria, supported by analytical and numerical methods. We find that coexistence of both serotypes is possible for a large range of parameters. Received: 7 July 1998 / Revised version: 12 July 2002 / Published online: 26 September 2002 Keywords or phrases: Dengue fever – Primary and secondary infections – Serotype – Coexistence – Threshold – Basic reproduction number – Persistence     

Visualization of TT virus particles recovered from the sera and feces of infected humans

TT virus (TTV) has not yet been cultured or visualized. We attempted to recover and visualize TTV-associated particles from the serum samples and feces of infected humans. Serum samples were obtained from 7 human immunodeficiency virus (HIV)-infected patients. Three patients had a high TTV DNA titer (10(8) copies/ml), three had a low TTV DNA titer (10(2) copies/ml), and one was negative for TTV DNA. Fecal supernatant was obtained from a different TTV-infected subject. The serum samples were fractionated by high-performance liquid chromatography, and TTV DNA-rich fractions were subjected to floatation ultracentrifugation in cesium chloride. Virus-like particles, 30-32 nm in diameter, were found in the 1.31-1.33 g/cm(3) fractions from each of the three serum samples with high TTV DNA titer, but not in any fraction from the four serum samples that either were negative for TTV DNA or had low TTV DNA titer. The TTV particles formed aggregates of various sizes, and immunogold electron microscopy showed that they were bound to human immunoglobulin G. Similar virus-like particles with a diameter of 30-32 nm banding at 1.34-1.35 g/cm(3) were visualized in fecal supernatant with TTV genotype 1a by immune electron microscopy using human plasma containing TTV genotype 1a-specific antibody.     

Infectivity of adeno-associated virus serotypes in mouse testis

Background

Recombinant adeno-associated viruses (AAVs) are emerging as favoured transgene delivery vectors for both research applications and gene therapy. In this context, a thorough investigation of the potential of various AAV serotypes to transduce specific cell types is valuable. Here, we rigorously tested the infectivity of a number of AAV serotypes in murine testis by direct testicular injection.

Results

We report the tropism of serotypes AAV2, 5, 8, 9 and AAVrh10 in mouse testis. We reveal unique infectivity of AAV2 and AAV9, which preferentially target intertubular testosterone-producing Leydig cells. Remarkably, AAV2 TM, a mutant for capsid designed to increase transduction, displayed a dramatic alteration in tropism; it infiltrated seminiferous tubules unlike wildtype AAV2 and transduced Sertoli cells. However, none of the AAVs tested infected spermatogonial cells.

Conclusions

In spite of direct testicular injection, none of the tested AAVs appeared to infect sperm progenitors as assayed by reporter expression. This lends support to the current view that AAVs are safe gene-therapy vehicles. However, testing the presence of rAAV genomic DNA in germ cells is necessary to assess the risk of individual serotypes.

     

Heat inactivation of enteric viruses in dewatered wastewater sludge.

The effect of moisture content on the rates of heat inactivation of enteric viruses in wastewater sludge was determined. The protective effect of raw sludge on poliovirus previously observed (R. L. Ward, C. S. Ashley, and R. H. Moseley, Appl. Environ. Microbiol. 32:339--346, 1976) was found to be greatly enhanced in sludge dewatered by evaporation. Other enteroviruses responded in a similar fashion. This effect did not appear to be due merely to the state of dryness of the sludge samples because in humus-deficient soil, a relatively inert material, the rate of poliovirus inactivation by heat was not significantly altered through dewatering. Instead, this effect appeared to have been caused by protective substances in the sludge, such as detergents, which are concentrated through dewatering. As reported previously (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol. 34:681-688, 1977; R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol 36:889--897, 1978) raw sludge is not protective of reovirus, but, instead, the ionic detergents in sludge cause the rate of heat inactivation of this virus to be accelerated. Dewatering of sludge, however, was found to partially reverse this virucidal effect. Evidence is presented indicating that this reversal is caused by an unidentified protective substance in sludge also concentrated through dewatering. Finally, it was shown that the effects of raw sludge on heat inactivation of poliovirus and reovirus are greatly reduced by composting, a result that correlated with the degradation of detergents.     

Heat inactivation of enteric viruses in dewatered wastewater sludge.

The effect of moisture content on the rates of heat inactivation of enteric viruses in wastewater sludge was determined. The protective effect of raw sludge on poliovirus previously observed (R. L. Ward, C. S. Ashley, and R. H. Moseley, Appl. Environ. Microbiol. 32:339--346, 1976) was found to be greatly enhanced in sludge dewatered by evaporation. Other enteroviruses responded in a similar fashion. This effect did not appear to be due merely to the state of dryness of the sludge samples because in humus-deficient soil, a relatively inert material, the rate of poliovirus inactivation by heat was not significantly altered through dewatering. Instead, this effect appeared to have been caused by protective substances in the sludge, such as detergents, which are concentrated through dewatering. As reported previously (R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol. 34:681-688, 1977; R. L. Ward and C. S. Ashley, Appl. Environ. Microbiol 36:889--897, 1978) raw sludge is not protective of reovirus, but, instead, the ionic detergents in sludge cause the rate of heat inactivation of this virus to be accelerated. Dewatering of sludge, however, was found to partially reverse this virucidal effect. Evidence is presented indicating that this reversal is caused by an unidentified protective substance in sludge also concentrated through dewatering. Finally, it was shown that the effects of raw sludge on heat inactivation of poliovirus and reovirus are greatly reduced by composting, a result that correlated with the degradation of detergents.     

Experimental infection of Culicoides brevitarsis from south-east Queensland with three serotypes of bluetongue virus

Laboratory-reared C. brevitarsis (biting midges) were fed on sheep which had been experimentally infected with bluetongue serotype 1 (CSIRO 156), bluetongue serotype 20 (CSIRO 19) or bluetongue serotype 21 (CSIRO 154), or on cattle experimentally infected with bluetongue serotype 20 (CSIRO 19). Approximately 77 000 C. brevitarsis were exposed to sheep and 9000 to cattle. The average percentage feeding on sheep was 54% and on cattle 47%. In attempts to transmit virus by bite 3360 C. brevitarsis which had fed on viraemic sheep were held for 11-15 days before exposure to susceptible sheep. Although 11% of these insects fed, transmission of virus from sheep to sheep was not demonstrated. Estimated infection rates of C. brevitarsis for each serotype from sheep and serotype 20 from cattle were similar at 0.4% or lower. These low infection rates are one of the factors which make it unlikely that C. brevitarsis could be an efficient vector of bluetongue viruses in sheep in the field.     

污水厂产超广谱β内酰胺酶大肠杆菌通过接合水平传递耐药性

【目的】研究废水中产超广谱β-内酰胺酶大肠杆菌中可移动质粒在耐药基因水平传播机制中的作用。【方法】对污水厂分离所得的50株产ESBLs大肠杆菌进行接合试验,并对所得的接合子采用纸片扩散法测定其对15种常见药物的耐药表型,针对质粒介导的产ESBLs菌株的耐药基因设计7对特异性引物对接合子进行PCR扩增。【结果】研究结果显示,80份水样分离得50株产ESBLs大肠杆菌,共接合成功35株细菌,接合成功率高达70%。接合子与供体菌相比,均发生耐药谱型的改变,且存在丢失一种或几种药物耐药性且产生另一种或几种药物耐药性的现象。PCR扩增结果显示,接合子与供体菌相比,耐药基因型有所减少或不变,bla_(TEM)、bla_(CTX-M)基因全部接合成功,bla_(SHV)基因仅1株未接合成功,耐氟喹诺酮类基因未发生转移。【结论】本研究表明,不同的耐药基因可能位于不同的可移动质粒上,可移动质粒在大肠杆菌耐药性水平传播的过程中起到了十分重要的作用。     

Vaccine matching and antigenic variability of foot-and-mouth disease virus serotypes O and A from 2018 Ethiopian isolates

International Microbiology - Foot-and-mouth disease (FMD) is highly infectious, limits live animal trade, and affects ranchers owing to the loss of animal yield. The present study was designed to...