Biomedical subjects

S A Skjold

Publications and source records attributed to S A Skjold.

7 recordsLinked to original sources

PubMed1987

Characterization of Streptococcus zooepidemicus (Lancefield group C) from human and selected animal infections.

We assembled an international collection of strains from sporadic and epidemic human infection with Streptococcus zooepidemicus (Lancefield group C) for laboratory study. Cultural and physiological characteristics of the isolates were determined, including biotyping with the API 20 STREP test kit and susceptibility testing with penicillin, erythromycin and tetracycline. The strains were examined for bacteriocin production and sensitivity and typed with a specially developed group-C streptococcal bacteriophage system incorporating a panel of 14 phages. Results of these tests gave useful discrimination between many of the strains: differences were shown between each of the major outbreak strains, including those complicated by post-streptococcal glomerulonephritis. Serious group C streptococcal infection may be caused by S. zooepidemicus and isolates should be identified to species level; the application of a typing scheme such as this may help to distinguish epidemiological patterns of infection.

Animals↗

PubMed1987

DNA fingerprinting of Streptococcus zooepidemicus (Lancefield group C) as an aid to epidemiological study.

A collection of Streptococcus zooepidemicus strains from human and animal infections was examined for DNA banding patterns after nuclease digestion and agarose gel electrophoresis. The large variety of DNA fingerprints found revealed the complexity of the species but showed that isolates from clusters of outbreaks had identical prints. The results confirmed the specificity of bacteriocin and bacteriophage typing of S. zooepidemicus; the technique also gave useful profiles on untypable strains. Strains with common bacteriocin and biotyping patterns from sporadic infections could be differentiated by their DNA fingerprints. In several outbreaks and incidents, more than one strain of S. zooepidemicus were encountered, and the importance of carefully interpreting typing data is stressed. Chromosomal DNA fingerprinting is a very efficient technique for demonstrating differences between strains of S. zooepidemicus, and its use is recommended for future epidemiological studies of this infectious agent.

Animals↗

PubMed1986

Surface proteins in the transduction of groups A and G streptococci.

Four pairs of M+SOR+ and M-SOR- variants of group-A type-49 streptococci were compared as receptor strains in transduction of a streptomycin-resistance marker. The yield of transductants was 5-9-fold greater with the M-SOR- variants than with the corresponding M+SOR+ variants. Treatment of M+SOR+ variants of type-49 streptococci with trypsin enhanced the rate of transduction by 16-35-fold whereas trypsin treatment of corresponding M-SOR- variants resulted in minimal enhancement (5-fold or less). With trypsin treatment the numbers of transductants were approximately equal in pairs of M+SOR+ and M-SOR- variants. Enhanced transduction (10-26-fold) of streptomycin resistance was obtained by trypsin treatment of another seven M+SOR+ type-49 strains, of diverse phage subtypes and from various geographical locations. A wide range of enhancement (5-46-fold) was found in eight of nine M+ strains of group-A type-6 streptococci. With trypsin treatment, three of 10 transducible group-G strains showed enhanced transduction (10-13-fold) of a plasmid containing a determinant for erythromycin resistance. Transductional enhancement is proteolytic in nature, being enhanced by trypsin, chymotrypsin, papain, pronase and streptococcal proteinase. Although interference with phage adsorption by surface proteins would appear to be the most obvious explanation for these findings, further studies are required to define more clearly the mechanism of trypsin enhancement.

Bacterial Proteins↗

PubMed1984

A bacteriocin produced by certain M-type 49 Streptococcus pyogenes strains when incubated anaerobically.

Bacteriocin production (P)-typing of 75 M-type 49 group-A streptococci obtained from a variety of epidemiological incidents in different countries gave no evidence of production under the usual aerobic test conditions. However, with anaerobic incubation, 28% of the strains gave a pattern of inhibitory activity against the indicator strains which was indistinguishable from that previously attributed to the bacteriocin, streptococcin A-FF22 (SA-FF22). Isolation and partial purification of the M type 49 bacteriocin (SA-M49) by freeze-thaw elution from anaerobically grown lawn cultures, followed by ammonium sulphate precipitation and Sephadex chromatography, showed the activity to be associated with a heat-stable proteinaceous molecule of molecular weight approximately 8000 - properties similar to those of SA-FF22. SA-FF22 and SA-M49 were found to have identical inhibitory spectra including immunity of the producer strains to the inhibitory activity of both the homologous and heterologous bacteriocin preparations. SA-M49 production occurred in some strains of phage subtypes II, III and provisional VI and, since it was a consistent property for all isolates from single outbreaks of infection, it provides a means of discriminating between strains of each of these three phage subtypes. There was no evidence of any increased incidence of SA-M49 production in M-type 49 strains associated with nephritic sequelae.

Anaerobiosis↗

PubMed1983

Type 49 Streptococcus pyogenes: phage subtypes as epidemiological markers in isolates from skin sepsis and acute glomerulonephritis.

Studies of group A, M type 49 streptococci from England, Trinidad and Alaska indicate that isolates of this serotype often differ with respect to phage subtype from one geographical area to another, but are generally homogeneous in one place at one time. The findings support the conclusion that acute glomerulonephritis can be associated with a variety of phage subtypes of M type 49 streptococci. In outbreaks of skin sepsis without nephritis in England, the phage subtypes of M type 49 streptococci isolated from skin lesions of meat handlers were the same as those recovered from skin lesions of non-meat handlers in the same community. The findings on the Trinidad isolates suggest that M type 49 streptococci of one phage subtype may persist in a population for 9 years and may result in a second outbreak of acute glomerulonephritis. In an Alaska Eskimo population in whom acute glomerulonephritis was occurring, most of the M type 49 isolates available for testing were of a single phage subtype. Equally prevalent in this population were group A streptococci that exhibited the same T antigen as the type 49 isolates but differed in their serum opacity reaction and phage subtype. This apparently related strain was not typable with available M antisera but showed functional evidence of M protein and is probably a new M type.

Alaska↗

PubMed1982

Transduction of the genetic determinant for streptolysin S in group A streptococci.

The genetic determinant for streptolysin S production (SLS+) was successfully transduced to two naturally occurring nonhemolytic strains of group A streptococci (Streptococcus pyogenes), an M-type 18 strain associated with an outbreak of rheumatic fever and an M-negative variant of a type 49 strain isolated from a skin lesion. Attempts to transduce this determinant to a nonhemolytic M-type 68 strain and a nonhemolytic T-type 12 strain were not successful. Transduction was accomplished with a double temperature-sensitive mutant bacteriophage. Cellular antigenic characters and the phage sensitivity of the transductants remained unaltered. The donor strain also transduced streptomycin resistance well when the nonhemolytic type 49 strain was used as a recipient. There was no evidence of cotransduction of the determinants for streptolysin S and streptomycin resistance.

Antigens, Bacterial↗

PubMed1976

Method for phage typing group A type 49 streptococci.

A method of phage subtyping group A type 49 streptococci is described. The method is similar to that used for phage typing staphylococci, except that lysates obtained by induction with mitomycin C rather than propagated stock phages were used. Five type 49 strains were used as phage donors. Seventy-two strains of type 49 streptococci isolated from 10 worldwide sources were examined by this method. Among these strains, five distinct subtypes (I through V) could be distinguished on the basis of their lytic patterns. Only a few of the type 49 strains could not be classified into one of these phage subtypes (6% using 100 X routine test dilution). Strains from a single source were generally homogeneous with respect to their phage subtype. The method proved useful in discriminating between type 49 strains isolated from different geographical sources and from the same place in different years. Studies in progress suggest that it may be useful for subtyping other strains of special epidemiological interest, such as strains of other serological types associated with nephritis.

Bacteriophage Typing↗