الفهرس 
The biofilm: basic microbiologyOnly 14 pages are availabe for public view
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Abstract
iofilm is a complex aggregation of microorganisms that encase themselves within an extracellular polysaccharide lining which the organisms secrete after adherence to a surface. The production of extracellular polysaccharide is essential for development of the architecture of any biofilm matrix. This gylcocalyx polymer acts as a protective exoskeleton serving as a physical barrier, limiting the effective antimicrobial concentrations within the biofilm microenvironment. Bacteria in the protected microenvironment of a biofilm are 50–500 times more resistant to antimicrobial therapies than planktonic bacteria.
Biofilm infections tend to be persistent. Microorganisms, when present within biofilms, produce novel proteins, with as yet unknown functions, that are not present in planktonic cells and may increase the immunogenicity of the organism. This different phenotypic expression of bacteria within biofilms leading to a complex interbacterial communication system is known as quorum sensing, allowing communal growth and survival under diverse environmental conditions
In the field of dermatology the predominant bacterial phenotype on epithelial surfaces is that of organisms organized within a biofilm. Biofilms have been observed on healthy skin
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and in a number of dermatological conditions, including some that were previously thought not to have an infectious etiology.
The biofilm forming ability of P. acnes had been reported. It has been suggested that P. acnes cells residing within the pilosebaceous unit grow as a biofilm.
The aim of the present study was to assess biofilm forming ability by P. acnes in different grades of acne and to evaluate the resistance pattern of biofilm from P. acnes against the commonly used antibiotics. This study was conducted on 100 patients with facial acne vulgaris, 90 males and 10 females. They were divided according to their acne severity into three groups: Group I (mild acne): included 5 patients, Group II (moderate acne): included 65 patients and Group III (severe acne): included 30 patients.
All subjects were randomly recruited and subjected to detailed history, careful general examination, and dermatological examination including grading of acne into 3 groups. Swab from the acne lesions were taken for isolation of P. acnes strains and testing their biofilm forming ability and the resistance pattern of biofilm against the commonly used antibiotics.
Our study revealed that, P. acnes had the ability of biofilm formation. This was not related to patient sex or duration of acne lesion. Yet, a statistical significant difference was detected on
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comparing the various grades of acne regarding P. acnes ability of biofilm formation which showed that the ability of biofilm formation was increased with increasing the grade of acne.
Furthermore, a statistical significant difference was detected, on comparing the study groups as regards the degree of biofilm. Our observation fortifies the notion that the degree of biofilm could increase with increasing the grade of acne.
Additionally, the ability of biofilm formation was positively related to receiving incomplete repeated courses of empirical systemic and/ or topical antibiotics that enhanced the transformation of planktonic form of P. acnes into biofilm forming ability.
Regarding the drug susceptibility of the biofilm, our results showed that, (74.55%) of biofilms were susceptible to penicillin, (70.91%) to clindamycin, (45.45%) to linezolid, (20%) to erythromycin, (14.55%) to tetracycline and finally, (9.09%) were resistant to all.
On comparing the drug susceptibility of the biofilm amid the different acne grades in the study groups we showed that the antimicrobial resistance of P. acnes was closely related to the severity of acne vulgaris. Resistant P. acnes strains tended to be frequently found in severe acne patients rather than in moderate acne patients.
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Interestingly, all of the biofilms which were resistant to all drugs were intermediate biofilms. This could be attributed to restricted penetration of antimicrobials, decreased growth rate, expression of resistance genes and the presence of resistant „„persister‟‟ cells.
To our knowledge this is the first study to compare between different grades of acne as regards the ability of P. acnes to form biofilm. As mentioned before, the ability of biofilm formation was increased with increasing the grade of acne and was positively related to receiving incomplete repeated courses of empirical systemic and/ or topical antibiotics. Additionally, the degree of biofilm was increased with increasing the grade of acne. Resistance to antimicrobials was found with increasing grade of acne and increasing degree of biofilm.
Further studies on large number of patients are recommended to appraise the biofilm formation in different grades of acne and antimicrobial susceptibility of P. acnes biofilm.
Finally, this work underlines the importance of biofilm formation by P. acnes in acne pathogenesis, and shows that biofilm formation should be considered in the diagnosis and treatment of acne.