Erythromycin resistant propionibacteria in antibiotic treated acne patients: association with therapeutic failure

Erythromycin resistant (EmR) propionibacteria were isolated from the skin surface of 51% of patients treated with oral erythromycin and 42% of patients treated with topical clindamycin compared with 3% of untreated control subjects (P less than 0.001). Amongst the topical clindamycin-treated patients, there was a higher incidence of EmR propionibacterial carriage in those patients who had previously been treated with oral erythromycin (64%) than in patients with no known previous exposure to erythromycin (20%; 0.01 greater than P greater than 0.001). Patients responding to oral erythromycin treatment carried EmR propionibacteria less frequently (24%) than patients who were not responding or who had relapsed (70%; P less than 0.001). These observations suggest that the use of oral erythromycin and/or topical clindamycin encourages the development of resistant propionibacteria and that the emergence of resistant strains is associated with therapeutic failure in erythromycin-treated patients. In total 63 resistant isolates were obtained from 52 subjects. There were 42 strains of Propionibacterium acnes, 16 strains of Propionibacterium granulosum and five strains of Propionibacterium avidum. The majority of isolates were inducibly or constitutively resistant to macrolide (e.g. erythromycin), lincosamide (e.g. clindamycin) and streptogramin B type antibiotics. Therefore, the isolates are phenotypically indistinguishable from the majority of EmR bacteria in which resistance is due to methylation of 23S ribosomal RNA.

Management options for Propionibacterium acnes endophthalmitis

The authors reviewed the management of nine culture-proven cases of Propionibacterium acnes endophthalmitis which presented at an average of 4 months after extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens (PC IOL) implantation. The initial signs included a white intracapsular plaque (9/9), vitritis (9/9), granulomatous uveitis (4/9), nongranulomatous uveitis (5/9), hypopyon (4/9), beaded fibrin strands in the anterior chamber (3/9), and diffuse intraretinal hemorrhages (2/9). A variety of management schemes were used in these patients, including the following: topical and intravenous antibiotics alone; intraocular and topical antibiotic administration; pars plana vitrectomy with capsulectomy and intraocular antibiotic administration; and removal of all capsular remnants with PC IOL removal or exchange. The final visual acuities ranged from 20/20 to 20/60 in six eyes and 20/200 to 20/400 in three eyes. This review suggests that a variety of management options for P. acnes endophthalmitis appear to be successful. Based on the authors' experience, an algorithm for future treatment is offered.

Role of lipids in augmenting the antibacterial activity of benzoyl peroxide against Propionibacterium acnes

Antimicrobial activity and physicochemical properties of benzoyl peroxide (BP) were investigated to determine the mechanism of action for the compound as an antiacne agent. The MICs and MBCs against nine strains of Propionibacterium acnes ranged between 100 and 800 micrograms/ml in a nutrient broth system, with a median fourfold increase in activity demonstrated when lipid was added. The partition coefficient of BP in a 50:50 artificial skin lipid and water system was greater than 2,500, with the concentration of BP soluble in lipid measured at 1.12% and in water at 0.005%. When BP was incubated in the presence of a lipid mixture, reaction products were formed, with evidence that at least some of these compounds possessed antibacterial activity. These results suggest that BP reduces the P. acnes numbers in sebaceous follicles because of good lipid solubility and interaction with the lipid component, the latter property contributing to the antimicrobial activity of the compound in a high-lipid environment.

In vitro activity of flomoxef compared to moxalactam, cefoxitin, cefotaxime, and clindamycin against anaerobes

To assess the in vitro activity of flomoxef (6315-S), moxalactam, cefoxitin, cefotaxime, and clindamycin against anaerobes 197 clinical isolates (27 Bacteroides fragilis, 42 B. thetaiotaomicron, 10 B. vulgatus, 7 B. ovatus, 6 B. uniformis, 6 B. distasonis, 7 Bacteroides melaninogenicus group, 11 Bacteroides oralis group, 21 Clostridium difficile, 7 C. perfringens, 3 C. sporogenes, 3 Clostridium spp., 33 Propionibacterium acnes, 14 Peptococcaceae) were studied by means of agar dilution tests. The MIC90 of B. fragilis was less than 2 micrograms/ml for flomoxef, less than 4 micrograms/ml for moxalactam, less than 16 micrograms/ml for cefoxitin, less than 128 micrograms/ml for cefotaxime and less than 2 micrograms/ml for clindamycin. The respective MIC90's of B. thetaiotaomicron were less than 64, less than 128, less than 32, less than 256 and 8 micrograms/ml. Strains of the other Bacteroides species and groups were more susceptible to flomoxef and the other antibiotics than B. thetaiotaomicron. Against Clostridium difficile flomoxef (MIC90 less than 4 micrograms/ml) proved to be superior to the other agents tested. Most of the Clostridium strains other than C. difficile were also susceptible to flomoxef; anaerobic grampositive cocci and Propionibacterium acnes were very sensitive (MIC90's less than 1 and less than or equal to 0.125 micrograms/ml, respectively). Its anti-anaerobic activity, together with its efficacy against aerobes, should make flomoxef a useful adjunct to the arsenal of modern antibiotic therapy.

[In vitro activity of an ofloxacin-metronidazole combination against anaerobic bacteria. Kinetics of the action of metronidazole against Bacteroides fragilis]

The activity of metronidazole combined with ofloxacin was investigated by the checkerboard method in liquid medium against 60 obligate anaerobes. The bacteriostatic effect of the combination was assessed by calculating the FIC index. Two metronidazole resistant strains of Propionibacterium acnes (MIC greater than 32 mg/l) were inhibited by 0.125 mg/l of this former antibiotic in presence of an ofloxacin concentration equal to half the value of the MIC. On the 58 other anaerobic strains, the combination of metronidazole plus ofloxacin had an additive bacteriostatic effect (30 strains) or a synergistic effect (26 strains). No antagonism was noted with any strain. For selected anaerobic or mixed infections the combination of metronidazole and ofloxacin may be useful. Killing curves demonstrated that, under good anaerobic conditions, metronidazole acted rapidly against Bacteroides fragilis. At a concentration of 8 mg/l, a decrease of log10 of the population was observed after 2 hours. After a contact ranging from 1 to 8 hours, depending of the investigated strains, a bactericidal effect was observed with metronidazole.

In vitro activity of ampicillin plus sulbactam against anaerobes compared to ampicillin and cefoxitin

The antimicrobial susceptibility of 195 recent clinical isolates of anaerobic bacteria was studied to ampicillin alone, ampicillin + 1 mg/l sulbactam, ampicillin + 5 mg/l sulbactam, and cefoxitin by means of agar dilution tests. The ampicillin-sulbactam combinations were the most effective drugs against species of the Bacteroides fragilis group, the MIC90 of ampicillin + 5 mg/l sulbactam for B. fragilis being less than 1 mg/l, compared to 256 mg/l of ampicillin, 4 mg/l of ampicillin + 1 mg/l sulbactam, and 8 mg/l of cefoxitin. No significant difference between ampicillin alone and in combination with sulbactam was observed against gram-positive anaerobic rods, Peptococcus spp. and Peptostreptococcus spp. with MIC's less than 2 mg/l.

A 31P-NMR study of Propionibacterium acnes, including effects caused by near-ultraviolet irradiation

161.8 MHz 31P-NMR spectra were recorded from the light sensitive skin bacterium Propionibacterium acnes. The cells were grown anaerobically on synthetic phosphate-buffered Eagle's medium or on a complex yeast extract medium. The spectra showed a large accumulation of polyphosphates when grown on Eagles medium. A splitting of the inorganic phosphate peak indicated a difference between internal and external pH of the cells. Addition of glucose to the cell suspension gave rise to a change in the pH gradient across the cell membrane, as reported for other Gram-positive bacteria. A decrease in the polyphosphate peak was observed after addition of glucose. A lethal dose of broad-band near-ultraviolet light (corresponding to a 10% survival in a survival test), increased the amount of polyphosphates visible in the NMR-spectra. The addition of glucose to irradiated cells decreased the pH in the external solution, but no splitting of the inorganic phosphate peak could however be observed. 31P-NMR can, therefore, be used to study immediate near-ultraviolet-induced effects at the cellular level, at least in the case of P. acnes.

BMY 28100, a new oral cephalosporin

BMY 28100, a new oral cephalosporin with a (Z)-propenyl side chain at the 3 position and a p-hydroxyphenylglycyl substituent at the 7 position, was evaluated in comparison with cefaclor and cephalexin and, when appropriate, ampicillin and vancomycin. In vitro, BMY 28100 was more active than the reference cephalosporins against streptococci, Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes, Haemophilus influenzae, Propionibacterium acnes, Clostridium perfringens, and Clostridium difficile. BMY 28100 was comparable to cefaclor and more active than cephalexin against Staphylococcus saprophyticus and ampicillin-susceptible strains of Branhamella catarrhalis; but against ampicillin-resistant strains of B. catarrhalis, BMY 28100 was comparable to cephalexin and more active than cefaclor. Against Neisseria gonorrhoeae, BMY 28100 was comparable to cephalexin, but less active than cefaclor. Members of the family Enterobacteriaceae overall were equally susceptible to BMY 28100 and cefaclor but were less susceptible to cephalexin. In human serum, BMY 28100 was 45% protein bound. After an oral dose to mice, 82% of the drug was recovered in urine. The oral therapeutic efficacy of BMY 28100 in systemically infected mice reflected its activity in vitro.

Isotretinoin--an explanation for its long-term benefit

Isotretinoin is of undisputed benefit in the treatment of acne. In doses of 1 mg/kg/day for 4 months the drug produces a highly significant reduction in sebum excretion rate (90 +/- 3%) in comedone formation as measured by assessing follicular casts (70 +/- 5%), and in surface Propionibacterium acnes. However, the mechanisms of long-term clinical remission are not well understood. There are however, risk factors which predetermine the outcome to treatment with isotretinoin. Younger subjects (14-19 years) and those who have had acne for less than 6 years, respond less well than older subjects. Subjects with more truncal acne also fare less well than those with predominantly facial acne. A return of the reduced sebum excretion rate to within 10% of the pre-treatment level also is a poor prognostic factor. This and future studies could lead to development of more logical dose regimes depending, for example, on the age of the patient; duration of acne and its site. However, until proven otherwise, this study confirms our earlier data, and that of the German multi-centres and Strauss et al (1), that the optimum dose schedule for treating acne patients is 1 mg/kg/day regime.

Comparing 2.5%, 5%, and 10% benzoyl peroxide on inflammatory acne vulgaris

A 2.5% formulation of benzoyl peroxide was compared with its vehicle, and with a 5% and a 10% proprietary benzoyl peroxide gel preparation in three double-blind studies involving 153 patients with mild to moderately severe acne vulgaris. The 2.5% benzoyl peroxide formulation was more effective than its vehicle and equivalent to the 5% and 10% concentrations in reducing the number of inflammatory lesions (papules and pustules). Desquamation, erythema, and symptoms of burning with the 2.5% gel were less frequent than with the 10% preparation but equivalent to the 5% gel. The 2.5% formulation also significantly reduced Propionibacterium acnes and the percentage of free fatty acids in the surface lipids after 2 weeks of topical application.

The in vitro antimicrobial effect of azelaic acid

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.

Qualitative and quantitative changes in cutaneous bacteria associated with systemic isotretinoin therapy for acne conglobata

Quantitative cultures in 40 patients treated with systemic isotretinoin demonstrated a significant reduction in the anaerobic diphtheroid, Propionibacterium acnes within one month of therapy and a continued suppression during 5 months of treatment. This reduction persisted after discontinuation of isotretinoin therapy despite a return of sebum excretion to pretreatment levels. Surface aerobic bacteria showed a significant reduction in the total number of organisms and significant qualitative changes. Gram negative bacteria were sharply reduced in both the anterior nares and skin while Staphylococcus aureus recovery increased significantly.

Comparative in-vitro activity of Sch 34343 and other antimicrobial agents against anaerobic bacteria

The activity of Sch 34343 was determined against 575 strains of anaerobic bacteria by an agar-dilution method. Its activity was compared with that of benzylpenicillin, piperacillin, cefoxitin, imipenem, clindamycin, metronidazole, chloramphenicol, vancomycin, fusidic acid and bacitracin. Sch 34343 and imipenem were the most active agents tested. Based on these results, Sch 34343 appears to be a promising antimicrobial agent for anaerobic infections and warrants further clinical investigations.

Changes in the bacterial flora of the external ear canal from the wearing of occlusive equipment

External otitis has been associated with wearing obstructive gear covering the earlobe and external ear canal. In this study we investigated the changes in the bacterial flora of the external ear canal after wearing rubber hoods. The bacterial flora of external ear canals surfaces was investigated in a group of 19 volunteers who wore rubber hoods for a period of 25 to 30 minutes while doing manual work. The protective effect of 2% acetic acid was tested by instilling it in the left ear of all participants. Staphylococcus epidermidis, Propionibacterium acnes, and alpha-hemolytic streptococci were the predominant isolates from the ear samples. After hoods were worn, there was a substantial increase in the number of these organisms in 7 (36.8%) of the external ears. However, an increase in the bacterial counts in the external ear canals occurred in only 2 (10.5%) of the individuals treated prophylactically with acetic acid drops (P less than 0.02).

The mode of action of ethyl lactate as a treatment for acne

We have shown that an alcoholic lotion containing ethyl lactate when applied topically to rat skin under occlusion became localized in the follicles and sebaceous glands. When applied to human facial skin the ethyl lactate was hydrolysed to ethanol and lactic acid, and thereby lowered the skin pH. Under such conditions the growth of recoverable skin bacteria, in particular the anaerobe Propionibacterium acnes, was inhibited, and the hydrolysis of sebum to free fatty acids by lipase derived from the bacteria was greatly impaired. These effects of ethyl lactate would account for its observed clinical efficacy in acne vulgaris.

Resistance of propionibacteria to antibiotics used in the treatment of acne

Strains of propionibacteria resistant to clindamycin or clindamycin and erythromycin were isolated from four patients with acne, three of whom were receiving clindamycin. Four strains of P. acnes and one of P. granulosum with moderate levels of tetracycline resistance were isolated from 25 patients with acne being treated with tetracycline. A similar increase in tetracycline resistance was achieved by training sensitive strains in vitro. P. acnes was sensitive to sulphonamide and trimethoprim but some strains of P. granulosum were resistant to sulphonamide. Similar reports of clindamycin and erythromycin resistance from the USA suggest resistance may be increasing in isolates from patients with acne.

Comparative activity of benzoyl peroxide and hexachlorophene. In vivo studies against propionibacterium acnes in humans

The bactericidal effects of benzoyl peroxide (5% lotion) and hexachlorophene (3% colloidal suspension) against Propionibacterium acnes were compared in nine healthy college students who had the microbiological and skin lipid characteristics typical of acne vulgaris, but no active lesions. Each of the two medications was applied twice daily, to opposite sides of the face, for four consecutive weeks. Hexachlorophene was effective against surface aerobes but only slightly active against P acnes. It marginally reduced free fatty acid concentrations in surface lipids and in follicular porphyrin fluorescence. Conversely, benzoyl peroxide virtually eliminated P acnes and aerobes and induced substantially decreased free fatty acid concentrations and follicular fluorescence. We conclude that benzoyl peroxide exerts its antimicrobial action in the follicles and inhibits P acnes, while the antimicrobial effectiveness of hexachlorophene is limited to the skin surface.

The effect of benzoyl peroxide on cutaneous micro-organisms in vitro

The survival curves of cutaneous micro-organisms in the presence of benzoyl peroxide were investigated. All the curves exhibited a shoulder prior to exponential cell death. Benzoyl peroxide was lethal to the cutaneous organisms tested and they varied in sensitivity increasing as follows: Propionibacterium acnes, Staphylococcus capitis, Staph. epidermidis, Staph. hominis, Prop. avidum, Prop. granulosum and Pityrosporum ovale.

Effects of treatment with erythromycin 1.5 percent topical solution or clindamycin phosphate 1.0 percent topical solution on P. acnes counts and free fatty acid levels

Twenty healthy subjects (7 men and 13 women) with average baseline P. acnes counts equal to or greater than 1.0 x 10(5) were treated twice a day for eleven days in a randomized, double-blind study with either erythromycin 1.5 percent topical solution or clindamycin phosphate 1.0 percent topical solution. P. acnes counts and free fatty acid (FFA) measurements were performed before treatment, and on Days 4 and 11 of treatment. Statistically significant reductions in P. acnes counts were produced in both groups over the course of the study. There were no statistically significant changes in FFA, free fatty acid/fatty ester (FFA/FE) ratios or triglyceride levels. With erythromycin there were greater reductions in FFA and FFA/FE ratios and greater increases in triglycerides than with the clindamycin group, but the differences between the treatment groups were not significant. No adverse reactions were reported.