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Biomedical subjects

G Lecatsas

Publications and source records attributed to G Lecatsas.

At least 55 records · Page 3Linked to original sources
PubMed1983

The mechanical transmission of hepatitis B virus by the common bedbug (Cimex lectularius L.) in South Africa.

Tests for both hepatitis B surface antigen (HBsAg) and hepatitis e antigen (HBeAg) were carried out on wild-caught and laboratory-colonized bedbugs (Cimex lectularius L.), the latter after hepatitis B virus (HBV)-positive blood-meals. Positivity for both antigens was interpreted as an indication of HBV infectivity. Of 22 pools in which were tested 211 bugs collected in the northern Transvaal, 18 were HBsAg-positive and 17 HBeAg-positive, with estimated infection rates of 156,7 and 137,7 per 1000 bugs respectively. Passage of HBV in bugs, allowing an extrinsic incubation period of 57-69 days, resulted in 19 out of 25 bugs being positive for HBsAg after the first passage; only a small number of these were positive for HBeAg. After the second passage all bugs tested were HBsAg-negative, showing that the virus had disappeared. Tests on the salivary glands and carcass of each bug at intervals up to 31 days after an infective meal showed a positivity rate of 98% (HBsAg) and 17% (HBeAg) for carcasses and 20% (HBsAg) and 0% (HBeAg) for salivary glands. Attempts to detect HBV particles in the salivary glands by electron microscopy failed. Bugs were shown to continue to excrete HBsAg in their faeces up to the 42nd day, and both HBsAg and HBeAg together up to the 30th day. HBsAg particles were only detected by electron microscopy in faeces harvested on the 10th day. The results as a whole indicate that no biological multiplication of virus occurs in C. lectularius but that mechanical transmission from insects to man could occur by: (i) contamination of a person when crushing infective bugs; (ii) contamination from infected faeces; and (iii) infection by bite due to regurgitation or interrupted feeding.

Animals↗
PubMed1983

Bacteriophage M: an incompatibility group M plasmid-specific phage.

Phage M was specific for bacterial strains, of various genera, harbouring plasmids of the M incompatibility group. It formed turbid plaques which varied from pin point to more than 2 mm in diameter on all hosts where plaques were detected. The phage had an hexagonal outline with a diameter of 27 nm. It contained RNA but differed from other plasmid-dependent RNA phages in being sensitive to chloroform. It adsorbed along the length of shafts of M pili.

Escherichia coli↗
PubMed1983

Papillomavirus in urine in pregnancy and following renal transplantation.

A survey of papovavirus excretion in urine during pregnancy and following renal transplantation has shown that 0.32% of specimens from the former and 0.5% of the specimens from the latter individuals contain virus particles of a size and morphology typical of papillomaviruses. Of the eight pregnant women who excreted such particles none had any visible evidence of any papillomatous lesions, whereas five of the six renal transplant recipients surveyed had a variety of such lesions, including three who had a marked urethral papillomatosis. Although the small quantity of virus detected prevented serological confirmation of particle identity, the uniformity of size, lack of growth in tissue culture, and occurrence of urethral papillomas strongly suggest that papillomavirus is excreted by both groups of patients investigated.

Adult↗
PubMed1981

Intermediate size papovavirus particles in pregnancy urine.

By electron microscopy of negatively stained urinary sediments, papovavirus particles of size intermediate between papillomavirus and polymavirus have been detected in the urine of a pregnant woman. The excretion of size variants of these viruses and the absence of detectable papillomas in any of the women who were found to excrete only papillomavirus represent new findings.

Adult↗
PubMed1981

Phage C-1: an IncC group; plasmid-specific phage.

A phage was isolated from sewage and shown to form plaques on Salmonella typhimurium strains carrying C plasmids. It failed to multiply on strains lacking plasmids of this group. It also plated on Proteus mirabilis and Serratia marcescens strains carrying various IncC plasmids but failed to form plaques on Escherichia coli strains harbouring most of these plasmids, although in all cases, phage multiplication on the strains was demonstrated. No phage increase occurred in any of the strains which lacked an IncC plasmid or contained plasmids of other incompatibility groups. The phage is small, hexagonal in outline, contains RNA, is resistant to chloroform and adsorbs to the shafts of pili coded for by IncC plasmids.

Bacteriophages↗
PubMed1981

Characteristics of BK papovavirus DNA prepared directly from human urine.

DNA was prepared directly from preparations pf papovavirus excreted in the urine of 2 patients on immunosuppressive therapy, without preliminary amplification in cell cultures. EcoRI, BamHI, and HindIII restriction patterns were typical of BK virus DNA and were identical for the two isolates. However, there were significant differences in the sizes of the HindIII fragments when compared with those of standard cell-culture-adapted BK virus strains.

Animals↗
PubMed1980

Urinary virus excretion in pregnancy.

In a series of 774 women with pregnancies ranging from 7 weeks to term, virus particles representing five different groups have been detected in urine specimens by negative staining electron microscopy. Of the virus-positive women, 0,39% excreted papillomavirus (in the absence of genital warts), 3,1% polyomavirus, 0,26% adenovirus type II, 0,65% an antibody-coated unidentified virus particle and 7,7% a membrane-associated virus-like particle. The implications of these findings are discussed in the light of the apparently increased susceptibility of pregnant women to virus infection.

Adenoviridae↗
PubMed1980

Summer diarrhoea in African infants and children.

Of 70 black South African infants and children with acute summer diarrhoea, 30 (43%) were infected with enteropathogenic serogroups of Escherichia coli (EPEC), 13 (19%) with enterotoxigenic Gram-negative bacilli, 12 (17%) with Salmonella sp., 6 (9%) with Shigella sp., and 3 (4%) with rotaviruses. 13 (19%) patients were infected simultaneously with more than one enteropathogen, and no pathogen was detected in 22 (31%). In addition, 6 (15%) of 41 unselected patients were excreting Campylobacter fetus. Of 30 age-matched controls drawn from the same population, 5 (17%) were infected with EPEC serotypes, and 1 each with Salmonella sp. and rotavirus. This study stresses the polymicrobial nature of paediatric diarrhoea in a developing community and shows the continued importance of EPEC in this setting.

Campylobacter fetus↗
PubMed1979

Properties of R plasmid R772 and the corresponding pilus-specific phage PR772.

R plasmid R772 was isolated from a strain of Proteus mirabilis and is a self-transmissible P-1 incompatibility group plasmid having a molecular weight of about 27 x 10(6). It renders bacterial hosts resistant to kanamycin. Phage PR772 was isolated as a phage dependent on the presence of R772 in bacterial hosts. It is hexagonal-shaped with a diameter of 53 nm, has a thick inner membrane and no tail. Vaguely defined appendages are sometimes apparent at some vertices and the phage possesses double-stranded DNA. The DNA has a guanine plus cytosine molar content of 48%. The phage is sensitive to chloroform and has a buoyant density of 1.26 g cm(-3). These observations suggested that the inner membrane of the phage could contain lipid. Phage PR772 differs in morphology from the double-stranded DNA plasmid-specific phages PR4 and PRR1 which adsorb to tips and sides, respectively, of sex pili coded for by P-1 incompatibility group plasmids. Phage PR772 formed clear plaques which varied in diameter. Serologically, phages PR772 and PR4 are possibly related though very distantly, but the two phages have identical host ranges. Phage PR772 adsorbed by one of its apices to tips of sex pili coded for by plasmid R772 in Escherichia coli. It also formed plaques on Salmonella typhimurium Proteus morganii and Providence strains harbouring this plasmid as well as strains of E. coli carrying plasmids of incompatibility groups N or W. The phage produced areas of partial clearing on lawns of P. mirabilis PM5006 harbouring plasmid R772, the P-1 incompatibility group plasmid RP4, the W group plasmid RSa or the N group plasmid N3, and on lawns of Providence strain P29 carrying plasmid RP4.

Bacteriophages↗
PubMed1979

Genetic recombination in fused spheroplasts of Providence alcalifaciens.

Spheroplasts of Providence alcalifaciens strain P29 auxotrophs were prepared by combined treatment with glycine and lysozyme-EDTA. About 15% of spheroplasts had areas of cytoplasmic membrane exposed where cell wall was absent. The spheroplasts of different auxotrophs were mixed pairwise and fusion was attempted with polyethylene glycol or nascent calcium phosphate. After spheroplasts had regenerated to bacterial forms selection was made for recombinants. Recombinants arose at frequencies of 3.8 X 10(-6) to 1.7 X 10(-7) per spheroplast initially present, by both methods of fusion. The frequency was strongly dependent on the number of chromosomal loci used in selection. The possible order of five loci was determined and this corresponded to that on the closely related Proteus mirabilis chromosome. Control experiments excluded possibilities of auxotrophic reversion, conjugation, transformation, transfection or transduction as explanations of the results. Analysis of prototrophic clones yielded stable prototrophs or mixtures of stable prototrophs and stable recombinants. Parental types were not encountered. Unselected markers segregated among recombinants. It was concluded that the formation of recombinant bacteria was due to spheroplast fusion and that only stable products of the very temporary heteroploid state were haploid recombinants. The low frequency of recombination was ascribed to the limited number of spheroplasts with areas of exposed cytoplasmic membrane.

Cell Wall↗
PubMed1978

DNA viruses in urine after renal transplantation.

Approximately 2 500 specimens from 96 renal transplant recipients were examined for virus particles. Electron microscopy of negatively stained preparations showed that only 3 virus groups were present, namely polyomavirus, adenovirus and herpesvirus. No RNA viruses or oncogenic RNA viruses (retraviridae) were detected. Over a 5-year period polyomavirus was excreted by 37,5% of patients. Both herpesvirus and adenovirus were excreted by approximately 11% of the patients. Although trace quantities of other viruses may have been missed, the absence of RNA virus suggests that immunosuppressive treatment activates these DNA viruses. The failure to detect RNA viruses suggests that they are absent or may require different means of activation.

Adenoviridae↗
PubMed1978

The role of breast-feeding in the prevention of rotavirus infection.

Breast-fed infants are less susceptible to gastroenteritis than bottle-fed infants. Antibodies against rotavirus, the major pathogen of infantile gastroenteritis, were sought in human sera, colostrum and milk specimens by immunofluorescence. An experimental murine-rotavirus model was established by infecting the second litters of dams 4 weeks after infecting their first litters. Antibodies were absent from human and murine colostrum and milk specimens despite being present in virtually all sera, and the second mouse litters were as susceptible as the first. The inability of rotavirus to infect adult human beings and mice may prevent the formation of gut-derived antibody-secreting lymphocytes in milk, and thus prevent transmission of passive immunity. The association of bottle-feeding with rotavirus gastroenteritis appears to be the result of increased opportunity for spread of infection rather than of the absence of specific protective antibody.

Animals↗
PubMed1977

Rotavirus and winter gastro-enteritis in White South African infants.

In a microbiological investigation of winter gastro-enteritis in 23 White children rotaviruses were found in 14 (61%) and parvovirus-like particles in 1 (4%). Bacteriological examination of stools from 11 of these patients yielded one isolate of Salmonella eastbourne, but no enterotoxigenic or invasive bacteria were found. Rotavirus appears to be the main aetiological agent of acute winter gastro-enteritis in White infants.

Enterobacteriaceae↗