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Aims: A wide range of lipids are present on the skin surface of human beings and bacterial lipases are known to modify them. The microflora of the underarm (axilla) is often dominated by aerobic coryneforms and whilst many require lipids for growth, they appear not to be utilized as carbon sources. The aim of this study was to investigate the adherence aerobic coryneforms to lipids present on the skin surface of the human axilla to determine whether they contribute to colonization of the skin., Methods: Aerobic coryneforms were grown in a defined synthetic medium in the presence of (14)C-glucose to produce radio-labelled cells. Adherence to lipids was tested using a thin layer chromatography plate-based assay., Significance and Impact of the Study: The mechanism of bacterial adhesion to skin lipids is unknown. The results of this study show that a significant proportion of cutaneous aerobic coryneform isolates from the axilla interact with skin lipids resulting in increased adherence, which may contribute to skin colonization.

The cutaneous microbiology and antibody status to Propionibacterium acnes of patients with persistent (males, n = 32; females, n = 33) and late-onset (females, n = 25) acne were compared with individuals with adolescent acne (males, n = 22; females, n = 18) and normal control volunteers (persistent acne: males, n = 26; females, n = 30; late-onset: females, n = 20). Males had significantly higher grades of acne compared with females (P < 0.05). The microflora consisted in the main of propionibacteria, staphylococci and Malassezia; other bacteria represented less than 0.01% of the total microflora. At all sites for all samples there were significantly more propionibacteria than staphylococci or Malassezia (P < 0.05). There were significantly higher (P < 0.05) numbers of microorganisms in follicular casts from patients compared with their control volunteers for female facial skin and male back skin. Twenty-six papules and 48 normal follicles were analysed. A bimodal distribution of microbial colonization was noted, with about 90% of normal follicles and about 10% of acne follicles having no detectable viable microorganisms. Anti-P. acnes IgG antibody titres were measured using a secondary fluorescein isothiocyanate antibody technique, and no significant differences in titre were found between any groups of patients (P > 0.05). Correlation analysis showed no association between the population densities of P. acnes and anti-P. acnes IgG titres. There were no differences in the microbiology of skin of adolescent acne patients, persistent acne patients or late-onset acne patients which could account for these various forms of acne.

Concomitant application of 5% w/w benzoyl peroxide and 3% w/w erythromycin has previously been shown to prevent the overgrowth, on the skin of acne patients, of erythromycin-resistant coagulase-negative staphylococci, which occurs when the antibiotic is used alone. Two in vivo studies were carried out to assess the ability of the same therapeutic combination to inhibit the growth of pre-existing erythromycin-resistant propionibacteria and to prevent the selection of resistant strains during treatment. A double-blind clinical trial in 37 patients with mild to moderate acne vulgaris showed that the combination brought about a > 3 log10 c.f.u. reduction in total propionibacterial numbers/cm2 after 6 weeks therapy (P < 0.001, Wilcoxon's matched pairs) and also significantly reduced the number of erythromycin-resistant propionibacteria (P < 0.05). In contrast, erythromycin alone reduced the total propionibacterial count by < 1.5 log10 c.f.u./cm2 after 6 weeks (P < 0.05) and did not affect the number of erythromycin-resistant strains. The combined formulation was significantly more effective at reducing total propionibacterial numbers at 6 (P < 0.01, Mann-Whitney) and 12 weeks (P < 0.05) than erythromycin alone, although, after 12 weeks, the anti-propionibacterial efficacy of both preparations was less marked. Five patients on combination therapy, and five treated with erythromycin alone, acquired erythromycin-resistant strains de novo at week 6 or week 12. In an open study in 21 acne patients, who each carried > 10(3) c.f.u. erythromycin-resistant propionibacteria/cm2 skin pretreatment, the combination of erythromycin and benzoyl peroxide reduced the total propionibacterial count by > 2.5 log10 and the number of erythromycin-resistant strains by a similar amount (P < 0.001, Wilcoxon). This was accompanied by highly significant reductions in acne grade and lesion counts (P < 0.001). These data suggest that the combination of 5% w/w benzoyl peroxide and 3% w/w erythromycin has greater in vivo anti-propionibacterial activity than 3% w/w erythromycin alone, and brings about significant clinical improvement in acne patients with high numbers of erythromycin-resistant propionibacterial strains pretreatment.

The aetiological role of Malassezia furfur in various dermatoses is controversial. The role of the three serovars of M. furfur in Malassezia-associated diseases has not been investigated. This study measured population densities of M. furfur serovars A, B and C, propionibacteria and Micrococcaceae on the chest, back, forehead, left and right cheeks of 10 patients with pityriasis versicolor, and 10 age- and sex-matched controls; and 10 patients with seborrhoeic dermatitis, and 10 age- and sex-matched controls. The population densities of M. furfur, propionibacteria and Micrococcaceae did not vary at a given site between patients and the corresponding control subjects. Malassezia furfur serovar A was found to be the predominant isolate on the chest and back of all four groups, but there was no difference in the distribution of serovars on the forehead and cheeks. No serovar was specifically associated with lesional skin in either disease. Thus, this data indicated that there was no difference in either the total population density of M. furfur or the distribution of serovars on lesional skin compared with control skin in either pityriasis versicolor or seborrhoeic dermatitis.

Propionibacterium acnes is the predominant microbial resident within the pilosebaceous follicles of sebum-rich areas of human skin. This study investigated the effects of known hydrophobic components of sebum on the physiology and nutrition of this microorganism, grown anaerobically at 33 degrees C, under defined conditions using continuous culture techniques. The medium used was chemically defined, comprising eight amino acids, with glucose as the main carbon energy source, and the culture pH was maintained at 5.6. The range of sebum lipids assayed was based on the C18 monounsaturated fatty acid 9-cis-octadecenoic acid (oleic acid). Stock micronized solutions were aseptically pulsed into continuous cultures in the presence and absence of glucose, and nutritional effects monitored. None of the lipid substrates significantly affected P. acnes growth either in terms of maximum specific growth rate (mu max) or final culture biomass yield. Glycerol (3 mg ml-1) was found to be a poor carbon/energy source in comparison to glucose. Bacterial cells did, however, adhere with varying degrees, to the different lipid species, with maximum adherence occurring with the free fatty acid. This observation was confirmed by preliminary uptake experiments using [14C]oleic acid. The interactive site for cell adherence may be the lipid-fibrillar layer associated with the cell surface of P. acnes, as discerned in electron microscopical studies. The findings of this investigation suggest that one function of the P. acnes lipase may be to aid colonization within the pilosebaceous follicle, by promoting cell adherence to components such as oleic acid.

Coagulase-negative staphylococci (C-NS) are a frequent cause of bacteraemia in premature neonates. It is likely that the strains of C-NS causing bacterial sepsis in premature neonates have their origin on the patient's skin surface. We have studied the quantitative development of the skin microflora at eight sites on premature neonates. A swab wash method was used to sample and enumerate the cutaneous microflora of premature neonates admitted to an intensive care unit with respiratory distress syndrome. The numbers of bacteria present on the skin increased rapidly by 100-fold in the first week of life. The species of C-NS found on neonatal skin were similar to those found on adult skin. However, the bacterial population was 10(3) lower by comparison. There was considerable variation in numbers of bacteria and in the proportion resistant to antibiotics from day to day. There appeared to be no association between antibiotic usage and the proportion of isolates resistant to antibiotics, although the resident bacteria were in many cases resistant to a variety of antibiotics. C-NS were isolated from 92% of samples from which bacteria were isolated. Staphylococcus epidermidis was found at all sites and accounted for 82% of each colonial type of staphylococcus isolated. Other organisms isolated included Propionibacterium sp, alpha-haemolytic streptococci, aerobic spore-bearing bacilli, aerobic coryneforms, Candida albicans, Klebsiella oxytoca, Pityrosporum sp, Klebsiella pneumoniae, and Escherichia coli. The results of this study suggest that the skin of premature neonates is colonised with antibiotic resistant C-NS during the first week of life and that the chance of contamination of an intravascular catheter at insertion increases during this period.

Micrococcus sedentarius, an organism associated with pitted keratolysis, produced two proteinases in culture supernatant fluids, as shown by non-denaturing PAGE with overlaying with a casein substrate. A mixture had optimal activity at pH 10 with azocasein substrate. At pH 7.1 and 8.1 in continuous culture with varying dilution rates high proteinase production occurred at relative specific growth rates (mu rels) 0.39 and 0.77 and biomass concentrations decreased with increasing dilution rate. One proteinase was constitutive and varied little in production with different growth rates. The other proteinase was under control with high production at low growth rates and no production at high growth rates. With varying pH at mu rels 0.39 and 0.77 maximum biomass concentration and proteinase production occurred between pH 8.0 and 9.0 as did the highest specific growth rate. These results support the hypothesis that Mic. sedentarius produces pitting in the stratum corneum when the skin is hydrated and the pH rises above neutrality.

The axillary microflora of 34 male subjects were studied in relation to their underarm odour intensity. The predominant groups of micro-organisms were aerobic coryneforms, Micrococcaceae and propionibacteria. There was no competition for habitat between these groups (Fisher's exact test P greater than 0.05). There was an association between the population density of aerobic coryneforms and the intensity of odour (Spearman, P = 0.001). Dominance of aerobic coryneforms within the axillary microflora was associated with high odour intensity (chi 2, P = 0.005). An in-vitro odour model was developed using a diethyl ether extract of axillary skin incubated with test bacteria. Underarm odour was produced exclusively by aerobic coryneform bacteria. Of aerobic coryneforms, 71.4% were odour producers and these were identified as Corynebacterium xerosis.

The known involvement of axillary microflora with under-arm odour (UAO) production led us to determine whether the odorous 16-androstene steroids are formed in the axilla by bacterial metabolism of an odourless precursor such as testosterone. Axillary bacteria from 34 men were selectively cultured for aerobic coryneform bacteria (ACB), Micrococcaceae and propionibacteria. Overnight suspensions of bacteria were incubated separately at 37 degrees C for two weeks with radiolabelled testosterone plus unlabelled testosterone (0.5 mg) and 0.5-mg quantities of 4,16-androstadien-3-one (androstadienone) and 5,16-androstadien-3 beta-ol (androstadienol). After extraction and purification by Sep-Pak cartridges and thin-layer chromatography, the eluted steroids were derivatised as the pentafluorobenzyl oximes (PFBO) and tert.-butyl dimethylsilyl (TBDMS) ethers. Saturated analogues were used as internal standards. Selected-ion monitoring electron-impact mass spectrometry was performed at the m/z corresponding to the M+.ion for the PFBO derivatives and the [M - 57]+ ion for the TBDMS ethers. Only ACB produced classical musk-like UAO (UAO + ve) in an in vitro odour-producing system with 29% being UAO -ve. ACB (UAO +ve) metabolised far more (p = 0.001) testosterone than ACB (UAO -ve), the principal metabolites being 5 alpha(beta)-dihydrotestosterone, 5 alpha(beta)-androstane-3,17-dione and 4-androstene-3,17-dione (4-androstenedione). No non-polar 16-androstenes were formed. Micrococcus luteus (ten strains) metabolised testosterone to 4-androstenedione only; propionibacterium spp. did not metabolise testosterone at all. However, incubation of 16-androstenes with ACB gave evidence for 4-ene-5 alpha(beta)-reduction, 3 alpha(beta)-oxido-reduction and epimerisation. In general the direction of transformations favoured formation of the more odorous 5 alpha-androst-16-en-3-one (5 alpha-androstenone) and 5 alpha-androst-16-en-3 alpha-ol (3 alpha-androstenol) from less odorous steroids. Such transformations, in vivo, would not require de novo synthesis of 5 alpha-androstenone or 3 alpha-androstenol and would be consistent with utilisation by ACB of 16-androstenes already present in small quantities in fresh apocrine secretions, which are odourless, to produce a more powerfully smelling mixture on the axillary skin surface.

The cutaneous microflora of the mid-dorsal area of hairless and haired mice was studied by processing skin biopsies. In both C3H and CBA hairless genotype animals the prevalence of colonization and the bacterial density were significantly greater than in the haired animals. The dominant bacteria were staphylococci and aerobic coryneforms. No propionibacteria were isolated. Temporal studies with C3H mice showed that from 0 to 9 days after birth the cutaneous microflora reduced and from then on the haired genotype animals maintained a low cutaneous microflora, whilst hairless genotype animals gradually lost hair from head to tail and the microflora density increased. Reciprocal skin grafting between haired and hairless animals showed that the donor skin acquired the microflora characteristics of the recipient animal after 15 d post-grafting even though the donor skin remained morphologically true to genotype.

We describe a comparison of the scrub-wash method of Williamson and Kligman and a swab-wash method for the enumeration of cutaneous microflora. The swab-wash method provides a less traumatic alternative to the scrub-wash method and can be used to sample the cutaneous microflora of premature neonates.

An in vitro model has been developed to study the effect of soluble bacterial products on the viability and detachment of skin cell types utilized cultured grafts. Microbial products prepared from clinical isolates of bacterial species which most commonly colonize burn lesions showed marked variation in their ability to detach and kill both keratinocytes and fibroblasts. All three isolates of Acinetobacter spp. tested were effective in causing detachment and death of keratinocytes and fibroblasts, whereas Escherichia coli, Proteus mirabilis and Enterobacter spp. tested had little, or no, effect on detachment or viability for either skin cell type. Four Staphylococcus aureus isolates elicited variable strain-dependent results with regard to detachment and viability. One isolate possessed activity specific for keratinocyte detachment and death. These results indicate the possible undesirable effects such bacterial species may have on graft success in colonized burn wounds.

A survey has been made of the bacterial and fungal populations carried at three different sites on the feet of 60 individuals. The bacteria found at the three sites were quantitatively similar and Micrococcaceae and aerobic coryneform bacteria predominated. The carriage of other bacterial groups was generally low. There was a quantitative variation between sites--mean total counts were 1.04 X 10(7) cfu/cm2 skin in the fourth toe cleft, 4.08 X 10(5) cfu/cm2 skin on the sole and 1.21 X 10(3) cfu/cm2 skin on the dorsal surface. Staphylococci were most often dominant on the sole and dorsal surface whereas aerobic coryneforms predominated in the majority of fourth toe clefts. The higher the total count at a given site the more likely it was that aerobic coryneform bacteria predominated. The skin surface pH was significantly higher on the sole (mean value 6.25) than on the dorsal surface (mean value 5.23). Factors controlling the microbial ecology of the foot are discussed.

Propionibacterium acnes, Propionibacterium avidum and Propionibacterium granulosum were grown in continuous culture at 0-100% air saturation using a semi-synthetic medium. Maximum specific growth rate, biomass concentration and extracellular lipase, hyaluronate lyase and phosphatase activities were determined. All three species were capable of growth at 100% air saturation but at reduced growth rates. The presence of oxygen altered the production of extra-cellular enzymes. Propionibacterium avidum was the best adapted for growth in aerobic environments.

Correlation matrices were constructed for various human skin variables (propionibacteria, micrococcaceae, sebum excretion rate, percentage of free fatty acids and free fatty acid production rate). Two independent populations were studied (n = 87 and n = 103), and a subpopulation (n = 30) was investigated on three occasions at intervals of I month. In this way consistently high correlations could be differentiated from 'fortuitous' correlations. Propionibacteria versus micrococcaceae showed the highest correlation coefficient and propionibacteria versus percentage free fatty acids was also highly correlated. A scatter diagram indicated a relationship between the lower threshold of microbial density and sebum excretion rate. An explanation based on relative duct and gland size is presented.

A comparison of the cutaneous microflora found on normal feet with varying levels of odour has been made. High population densities of staphylococci and aerobic coryneform bacteria predispose to foot odour. There was no association between odour and the carriage on feet of any particular micro-organism, including brevibacteria. All organisms isolated were screened for exoenzyme activity. Only staphylococci produced lipase (78% of the staphylococci), whereas 97% of micrococci, 68% of aerobic coryneform bacteria, 25% of staphylococci and 94% of propionibacteria produced proteinase. The ability to degrade callous was exhibited by 47% of micrococci, 24% of aerobic coryneforms and 17% of the staphylococci. Feet with high odour had significantly higher population densities of micro-organisms with the ability to produce these exoenzymes than feet with low odour. No association was observed between foot odour and the carriage of micro-organisms capable of producing methanethiol. A hypothesis for the role of micro-organisms in the production of foot odour is proposed.

Full-thickness human cadaver skin was maintained on the dorso-lateral thoracic region of hairless mice whose immune rejection mechanism was suppressed using anti-mouse-thymocyte globulin. The bacterial profile of the pregrafted skin did not differ significantly from the normal human microflora. In contrast, the murine skin exhibited quantitative and qualitative differences from the human flora, in particular by the complete absence of Propionibacterium acnes, the dominant bacterium on sebum-rich areas of human skin. The normal microbial profile of the human grafts was maintained throughout the experimental period despite the novel environmental milieu. There was little contamination of the grafts from the normal murine flora. It was concluded that the grafted human skin would provide a realistic model for studying the ecology of human cutaneous micro-organisms.

Bacteria were sampled using a "scrub" technique from the skin surface of the faces of forty-nine female subjects aged 18-21 years. The sebum excretion rate was determined by a gravimetric method and the level of free fatty acids by titration. The production rate of free fatty acids was calculated from the product of the concentration of free fatty acids in the sebum and the sebum excretion rate. The date was analysed using Kendall's rank correlation method. Positive correlations existed between the number of Micrococcaceae and the skin propionibacteria (P < 0.001) and between both groups of organisms and the production rate of free fatty acids (P < 0.001). There was no significant correlation between the size of the bacterial population and the sebum excretion rate. The results support the view that free fatty acids are produced as a result of bacterial action, that the Micrococcaceae and skin propionibacteria do not compete to the detriment of their respective populations, and that the size of the bacterial population is not dependent upon the sebum excretion rate.

Three cutaneous propionibacteria, Propionibacterium acnes, Propionibacterium avidum and Propionibacterium granulosum, were grown in chemostats using semi-synthetic medium at various pH values. Growth occurred between pH 4.5 and 7.5 for P. acnes and pH 5.0 and 8.0 for P. avidum and P. granulosum. The highest mumax was at pH 6.0 for the three species. Maximum biomass production was obtained at pH 6.0 for P. acnes and P. avidum and at pH 7.5 for P. granulosum. Extracellular enzyme production occurred over the entire pH growth range when denaturation of the enzymes was taken into account. However, detectable activity of the enzymes was found in a narrower range of pH due to the denaturation of the enzymes at low or high pH values. The highest production of enzymes occurred at pH values between 5.0 and 6.0, apart from the production of hyaluronate lyase of P. granulosum (pH 6.0 to 7.0) and the proteinase of P. acnes and P. avidum (pH 5.0 to 7.5). Propionibacterium acnes produced a lipase, hyaluronate lyase, phosphatase and proteinase activity. Propionibacterium avidum produced a lipase and proteinase activity. Propionibacterium granulosum produced a lipase and hyaluronate lyase.

Erythromycin-resistant propionibacteria isolated from the skin of antibiotic-treated acne patients were found to express four different patterns of resistance to a set of eight MLS antibiotics. The majority of isolates (48/89 strains) were constitutively resistant to 14- and 16-membered ring macrolide, lincosamide and streptogramin B-type antibiotics. MICs of josamycin (0.5-16 mg/l) and spiramycin (0.5-128 mg/l) were lower than those of erythromycin, oleandomycin and tylosin (64 to less than 512 mg/l). Two strains of Propionibacterium granulosum exhibited inducible MLS resistance. Both 14- and 16-membered ring macrolides and virginiamycin S induced clindamycin resistance in these strains. Fifteen isolates demonstrated a similar phenotype to the inducible strains but were non-inducible by erythromycin. A fourth group of strains demonstrated high level resistance to all five macrolides tested (MIC greater than or equal to 128 mg/l) but were sensitive to virginiamycin S. The phenotype displayed by these strains is not compatible with the expression of methylase genes as currently known, nor with the action of an erythromycin esterase which hydrolyses only 14-membered ring macrolides. The resistance patterns of 12 isolates could not be classified into any of the above phenotypic classes. Therefore, the majority of erythromycin resistant propionibacteria express MLS resistance which is phenotypically similar to that coded for by several well characterized RNA methylase (erm) genes.

Seventy one papules in the early stages of inflammatory development were isolated from acne vulgaris affected skin and their content of micro-organisms characterized. The progress of lesions prior to excision was monitored by tracing an area of the upper back onto a transparent acetate sheet. This template was used the next day, and in some cases after 3 days, to identify inflamed lesions of less than 1 day and 2-3 days duration. These were biopsied, and pilosebaceous units isolated by micro-dissection, homogenized and microbial populations studied by viable counting and microscopy. Propionibacteria colonised 68% of '1 day' duration lesions and 79% of '3 day' duration lesions; staphylococci colonized 19% and 32% respectively and Pityrosporum spp. (Malassezia furfur) were found in 52% and 68%. Although the prevalence of each microbial group was higher in the more chronic lesions, these differences were not statistically significant. The microbial profile of inflamed lesions was similar both qualitatively and quantitatively to non-inflamed lesions studied previously. These results call into question the role of micro-organisms as the initiators of inflammation in acne vulgaris.

The prevalence and abundance of Malassezia furfur on clinically normal skin at 20 sites has been determined. All of the 16 subjects studied (young adults) had high counts on the upper trunk and on at least one site on the head. Counts obtained from the lower trunk and upper thighs of male subjects were considerably higher than those from female volunteers. Organisms isolated, grouped according to their colony morphologies, had distributions consistent with those noted for 'Pityrosporum ovale' and 'P. orbiculare' in previous studies. Mean M. furfur counts were compared with aerobic and anaerobic bacterial counts performed at the same sites. Propionibacteria and M. furfur distributions were similar but not identical. Some factors which might limit the range of M. furfur are discussed.

A quantitative study was made of the microflora of 174 acne and 68 non-acne subjects. Two groups of organisms were investigated, the anaerobic diphtheroids and members of the Micrococcaceae. The results showed high numbers of both groups of bacteria in skin bearing blackheads, papules or pustules and in non-acne adolescent skin. There were significantly lower numbers of bacteria in the pilosebaceous ducts of normal looking skin in acne areas and in pre-adolescent skin when compared with non-acne adolescent skin. It is suggested that increased numbers of bacteria alone do not predispose to acne, but that their interaction with the skin, which is a function of the localized skin environment, may be important.

A cryostat sectioning procedure was used to determine quantitative viable counts of microorganisms both on the surface and in successive layers of human cadaver skin biopsies. Also, using a previously described xenograft model, we investigated the dependence of microorganisms on the presence of sebaceous glands by using full thickness (1.5-2.0 mm) and split thickness (0.6 mm, ensuring sebaceous gland exclusion) human skin. Our results show substantial variation in the distribution and abundance of skin bacteria, even amongst biopsies from the same cadaver. In general, propionibacteria were distributed within a narrow band at varying depths beneath the skin surface whereas staphylococci were more broadly distributed. The importance of this with respect to topically applied antiseptics and antimicrobial agents is indicated. The xenograft studies demonstrated that propionibacteria were dependent on the presence of sebaceous glands whereas staphylococci were not.

A method allowing isolation and microbiological analysis of individual pilosebaceous units (follicles) was used to study biopsies of back skin obtained from volunteer acne vulgaris patients. The main microbial groups isolated were members of the genera Propionibacterium, Staphylococcus and Pityrosporum. The incidence (and mean density) of these organisms in 140 normal follicles was 12% (2.6 X 10(5) per follicle), 4% (5.5 X 10(3) per follicle) and 13% (10(2) per follicle) respectively. Colonized follicles were not distributed evenly amongst the subjects studied. The results are analysed and discussed from an ecological standpoint.

Two hundred and forty-one strains or resident skin bacteria comprising 93 isolates of Propionob acterium acnes and 148 of Micrococcaceae derived from 36 acne patients and 8 control subjects were screened for their ability to inhibit 32 indicator strains, including 20 strains of P. acnes and 12 strains of Staphylococcus epidermidis derived from patients with all grades of acne and from normal skin. Fifty-three strains (22%) showed some activity against at least one indicator strain. Both broad- and narrow-spectrum inhibition was detected. Inhibitory isolates of P. acnes outnumbered inhibitory Micrococcaceae by four to one. There was a low frequency of inhibition of S. epidermidis by Micrococcaceae (2.7%) and by P. acnes (1.1%) and a higher frequency of inhibition of P. acnes by Micrococcaceae (9.5%) and by P. acnes (40.8%). Furthermore, 81.8% of the subjects sampled possessed strains inhibitory to P. acnes. The significance of this finding is, as yet, unknown. No difference in the prevalence of active strains in normal (20%) and acne (22.5%) skin was detected. These findings suggest that the possession of inhibitory strains and conversely the possession of sensitive strains does not predispose to acne.

Various strains of cutaneous micro-organisms were tested in vitro for their survival rates in 0.5 mol/l (8.4% w/v) azelaic acid solution. All bacterial strains exhibited large reductions in viability (at least 40-fold) over a 24 h test period, but little response was noted with Pityrosporum ovale. The bactericidal effect of azelaic acid was reduced considerably in the presence of nutrients. Minimum inhibitory concentrations (MICs) and minimum bactericidal (or fungicidal) concentrations (MBCs) were also determined. MICs varied from 0.03 mol/l to 0.25 mol/l; MBCs were all either 0.25 mol/l or greater.

This study examined the humoral immune responses to Malas-sezia furfur serovars A, B and C of 10 patients with pityriasis versicolor, 10 patients with seborrheic dermatitis and 20 age- and sex-matched controls. A transferable solid-phase ELISA was used to determine titres of total Igs, IgM. IgA and IgG specific to M. furfur serovars A, B and C. The results demonstrated that patients with seborrheic dermatitis had a significantly higher titre of total Igs to serovar A than patients with pityriasis versicolor; and that patients with seborrheic dermatitis had a significantly higher titre of IgA to serovar C than patients with pityriasis versicolor. The titres of total Igs for controls and patients with seborrheic dermatitis were significantly lower to serovar B than to serovar C. A modified TSP ELISA was used to determine the titres of the IgG subclasses. Titres of IgG[SUB1,3,4] to serovar B were significantly higher in seborrheic dermatitis patients than pityriasis versicolor patients and titres of IgG[SUB3] to serovar A were significantly higher in seborrheic dermatitis patients than pityriasis versicolor patients. However, despite the differences between the patient groups, none of these results was significantly different to those of con- trols. Thus, this study did not demonstrate any differences in humoral immunity of patients suffering from Malassezia-associated dermatoses when compared to normal controls. These results may suggest that the humoral immune response to M. furfur is not related to the pathogenesis of Malassezia-associated dermatoses, but simply to the carriage of M. furfur on the skin. [ABSTRACT FROM AUTHOR]