Natural antibiosis among skin bacteria as a primary defence against infection

133

116

Although the micro-organisms forming the cutaneous microbiota are considered to play important roles in the modification and prevention of skin diseases, a comprehensive analysis of their composition has not yet been carried out because of difficulties in determining yet-to-be-cultured micro-organisms in the samples. Swab-scrubbed forehead skin samples of five healthy volunteers were analysed by profiling 16S rRNA genes, as well as by conventional culture methods, to provide a profile of the cutaneous microbiota that included yet-to-be-cultured bacteria from normal human skin. Cluster analyses of the 16S rRNA gene sequences indicated a marked increase in diversity compared with that derived from the culture methods. Nineteen previously recognized species and 13 novel phylotypes were obtained from the analysis of 416 clones. In addition to well-known bacteria such as Staphylococcus epidermidis and Propionibacterium acnes, phylotype A, the 16S rRNA gene of which is 97 % similar to that of Methylophilus methylotrophus, was detected in three of the five samples, in one of which it was the predominant clone. Culture-independent genetic profiling of 16S rRNA genes for detecting human cutaneous microbiota has allowed us to detect potentially novel components of the cutaneous microbiota in humans.

Section: Discussioncontrasting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Detection of potentially novel bacterial components of the human skin microbiota using culture-independent molecular profiling

Dekio

Hayashi

Sakamoto

et al. 2005

133

116

“…In contrast, Selwyn (1975) found that isolates from 22.6% of 340 persons produced antagonists when tested against coagulase-negative staphylococci and coryneforms (Selwyn and Ellis, 1972). …”

Section: Discussionmentioning

confidence: 99%

“…

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mentioning

confidence: 99%

Carriage of inhibitor-producing organisms on human skin

Noble¹,

Willie²

1980

SELWYN (1975) described the carriage of antibiotic-producing organisms on human skin and showed how they might protect the carrier against colonisation with potential pathogens such as Staphylococcus aureus. Subsequent work by Selwyn and his colleagues (Marsh and Selwyn, 1977a and b;Milyani and Selwyn, 1978) has shown that these antibiotic producers can restrict the growth of susceptible strains in vitro. This paper reports a study of the carriage, in patients with skin disease, of "antibiotic"-producing cocci with an activity against S. aureus. MATERIALS AND METHODSSamples for bacterial culture were taken from the nose, the chest, the perineum and one or more lesions of patients admitted to the Inpatient Department of St John's Hospital for Diseases of the Skin; cotton-tipped swabs moistened with broth were used. When S. aureus was isolated from a skin lesion the opinion of a clinician, usually the senior house officer, was sought on whether the lesion was clinically infected or only colonised; these opinions were recorded. The swabs were inoculated on to Blood Agar Base (Oxoid CM55) used as a 'nutrient' agar and the plates were incubated aerobically for 24 h at 37°C and left on the bench for a further 24 h at ambient temperature. A semi-quantitative assessment was made of each colony type present.Representatives of all colony types were subcultured on to blood-agar-base plates under a serial code number and examined for production of inhibitors. In the initial studies on about 4000 isolates, the method used was a modification of a pyocine typing method (Darrell and Wahba, 1964) in which test strains were inoculated as a heavy streak across the diameter of a glass petri dish containing blood-agar-base medium. This plate was then incubated for 24 h, after which the growth was removed by scraping with a microscope slide and the plate was exposed to chloroform vapour for 10 min. After exposure to air to permit evaporation of residual chloroform, four indicator strains were inoculated at right angles to the site of the original culture. The plates were then reincubated for 24 h at 37°C. Antibiotic production was indicated by a failure of growth in the area from which the test strain had been removed.Another 1300 isolates were tested by a modification of thismethod in which, after removal of the test-isolate growth with a glass microscope slide, any remaining cells were spread over the surface of the medium with a cotton tipped swab ('Q-tip') moistened in broth. The plate was then exposed to ultraviolet light for 20 min. to kill remaining cells; four indicator strains were then applied as previously described.The indicator strains used were S. aureus PS80, the original epidemic strain which remains virulent for mice and is used for propagating phage 80; S. aureus PS 42E, the propagating strain for phage 42E; S. aureus Wood 46, the standard a-haemolysin producer; and Micrococcus luteus 27B, a wild-type isolate from a patient. RESULTSFrom 292 patients, 5282 strains were tested. Inhibitor producers active against S. ...

“…The possible protective role of antibiotic-producing organisms in dermatological lesions was indicated in a recent epidemiological study (Selwyn, 1975). A limited amount of experimental work in animals has been carried out by Pryjma, Heczko and Wilburg (1972), who used Staph.…”

Section: Discussionmentioning

confidence: 99%

Quantitative Studies on Competitive Activities of Skin Bacteria Growing on Solid Media

Milyani

Selwyn

1978

&ATE m v IINTERACTIONS among skin micro-organisms have begun to receive attention in recent years, but detailed quantitative work has apparently been restricted to growth studies in liquid media (Marsh and Selwyn, 1977). However, such culture systems bear little or no relationship to the skin surface. As a first step towards a more realistic approach, we have devised a quantitative method to study pure and mixed cultures growing on the surface of agar media, and experiments were carried out on antagonistic activities between skin bacteria by means of this procedure. The method, and representative results obtained with it, are described in this paper. MATERIALS AND METHODSBacterial strains. The three commensal organisms used were an antibiotic-producing strain of Staphylococcus epidermidis biotype 4 (Baird-Parker, 1974) referred to as S6+, a penicillin-resistant non-antibiotic-producing strain of Staph. epidermidis of biotype 4 referred to as S6-, a strain of Micrococcus sp. classified as M7 according to Baird-Parker (1965), and a group-D diphtheroid strain (Evans, 1968). These were all isolated from normal skin.The three pathogenic organisms used were a penicillin-resistant strain of Staphylococcus aureus (bacteriophage group 111) and a strain of Streptococcus pyogenes, both from infected skin lesions, and a strain of Corynebacterium diphtheriae var. mitis from a stock culture. The Staph. aureus strain showed relatively small inhibition zones in direct antagonism tests with S6' when compared with all but one of the other bacteria studied. The exception was the non-antibiotic-producing strain, S6-, which was totally resistant to the action of S6 + (Marsh and Selwyn, 1977).Media. Nutrient agar and blood agar were used as growth media, and stock cultures were kept in nutrient broth at 4°C. The media were prepared as described by Cruickshank (1965) with Proteose Peptone and Lab-Lemco (Oxoid), New Zealand Agar and Defibrinated Horse Blood (Tissue Culture Services), and, in addition, 0 3 % (w/v) Liver Digest and 0 3 % (w/v) Yeast Extract (Oxoid). The selective media devised by Marsh and Selwyn (1977) made it possible to obtain differential counts of the bacteria in mixtures (table I).SampZing method. The quantitative study of bacteria growing on a solid surface was carried out with special Petri dishes (Sterilin, code 504 S) which were originally designed for direct contact culture of contaminated surfaces. Each dish had a surface area of 24 cm* and a grid divided into centimetre squares. The inoculum was prepared by diluting a 24-h culture to give approximately 10' colonyforming units (c.f.u.) per ml. For pure culture studies, a 0.2-ml volume was placed on the surface of the medium after it had dried for 20 min. Each plate was gently rotated to distribute the inoculum evenly over the surface (8 x lo3 c.f.u. per cm2). In mixed-culture studies, 1-ml volumes containing 1 x lo6 c.f.u. of each strain were mixed and 0.2 ml of the mixture was used as the inoculum. Readings of viable counts taken at intervals permitted the c...