Genotypic analysis of strains of mutans streptococci by pulsed-field gel electrophoresis

The species and serotypes of various strains of S. mutans and S. sobrinus were characterized by pulsed-field gel electrophoresis after the genomic DNA from the various strains had been digested with five restriction enzymes (EcoR I, Xba I, Hind III, Sfi I and BssH II) separately. Among these restriction enzymes, BssH II was very useful for the characterization of species and serotypes and, in particular, digestion discriminated between serotypes d and g. The restriction patterns obtained from the genomic DNA of isolates isolated from children's saliva were essentially identical to those from the genomic DNA of the standard laboratory strains. Patterns of BssH II digests of the genomic DNA of 10 isolates identified as S. sobrinus were characteristic of serotype g of the standard laboratory strains. Our results indicate that digestion with BssH II and subsequence analysis by pulsed-field gel electrophoresis should be useful for the characterization of species and serotypes and for epidemiological studies of mutans streptococci.     

beta-N-acetyl-D-glucosaminidase activity of oral nutritionally variant streptococci

The ability of nutritionally variant streptococci from the oral cavity to produce beta-N-acetyl-D-glucosaminidase (NAGase) activity was studied. Of the three biotypes analyzed, the strains belonging to biotype III were all shown to produce detectable amounts of both cell-associated and excreted NAGase activity; some strains, but not all of biotype II, were also good NAGase producers, whilst strains of biotype I were not. NVS may contribute to the production of NAGase activity found in human saliva.     

Protein G genes: structure and distribution of IgG-binding and albumin-binding domains

Protein G (also designated Fc receptor type III) is the IgG-binding protein of group C and G streptococci. Protein G has also been shown to bind human serum albumin but at a site that is structurally separated from the IgG-binding region. From the known gene sequence of protein G, two synthetic oligonucleotides were constructed for use as probes in DNA-hybridization experiments to study the structure and distribution of the albumin- and IgG-binding regions in bacterial strains belonging to different species. Thus, one of the probes corresponded to repeats within the IgG-binding region (I) and the other corresponded to repeats in the albumin-binding encoding region (II). Probe I showed strong hybridization to DNA isolated from 31 human group C and G strains, whereas hybridization to probe II was variable. With the three restriction endonucleases used, three restriction patterns were found in Southern blot experiments. No fundamental difference could be detected in hybridization experiments, either between strains of group C and G streptococci, or between isolates of different clinical origin. No hybridization to DNA from other bacterial species was found.     

Antigenic specificity of opsonophagocytic antibodies in rabbit anti-sera to group B streptococci.

An opsonophagocytic assay has been developed which requires human polymorphonuclear leukocytes, immune serum, and complement for optimal killing of Group B streptococci. Only with all three of these components was killing of greater than 1.0 log10 of the initial inoculum achieved, using rabbit antisera directed to homologous strains of each of the five known serotypes of Group B streptococci. Titers of specific antisera which opsonized the strains and resulted in greater than 1 log 10 reduction of colony-forming units, ranged from 1:100 (serotype Ib) to 1:3200 (serotype Ia). Cross-reactions between serotype-specific sera and heterologous strains were seen in certain instances. Type Ic strain and serotype Ic antiserum demonstrated cross-reactions with types Ia and Ib which were explainable by known shared antigens among these types. The only other cross-reaction which resulted in greater than 1 log 10 reduction in colony-forming units was when unabsorbed antiserum to strain Ia was used to opsonize a strain of serotype III. Opsonization of 10 serotype III strains was demonstrated with a single type III antiserum. Killing of nine of these strains required polymorphonuclear leukocytes, complement, and antiserum, but one strain, D136C, the reference strain, could be killed (greater than 1 log 10 reduction in colony-forming units) without either complement or specific antiserum. Inhibition studies were performed utilizing large m.w. polysaccharide antigens extracted from each serotype. These antigens inhibited opsonization of homologous strains by homologous antisera with 50% inhibition points ranging between 0.5 and 4 mug.     

一种新的人兽共患传染病——狐阴道加德纳氏菌病的研究 V.狐阴道加德纳氏菌菌株的血清分型研究

将我国6个省(区)、13个主要狐场分离的145株狐阴道加德纳氏菌,进行抗原性、免疫原性测定,从每场分离菌中选出1～3个优良株进行血清型研究。凝集素交叉吸收试验证实,选出的26株菌可划分为3个血清型,以此3个血清型代表株制备因子血清,余下119株菌中,108株在所划分的3个血清型内,11株未能定型。在3个血清型中,Ⅰ型菌株数占定型菌数的79.1％,因而确定,Ⅰ型菌是国内狐场狐阴道加德纳氏菌主要流行型。试验还明确了从貉分离的5株、水貂分离的4株、犬分离的2株阴道加德纳氏菌也属于血清Ⅰ型。将3个血清型代表菌株制成超声抗原,经免疫琼脂扩散试验证实,各型抗原与同型或异型免疫血清均可形成一条明显的融合沉淀线,表明各型菌间有共同抗原成分。同型菌免疫琼脂扩散试验表明,各株菌形成的沉淀线完全融合,从而证实了血清分型的可靠性。     

An immunoblotting technique for the detection of bound and secreted bacterial Fc receptors

A rapid semiquantitative procedure that enables bacteria to be screened for surface or secreted receptors for the Fc region of human IgG is described. Surface Fc receptors were detected by direct transfer of bacterial colonies to nitrocellulose by electroblotting and then probing with ¹²⁵I-labeled human IgG in the presence of a two fold molar excess of unlabeled F(ab′)₂fragments. The blots were exposed to X-ray film and the intensity of the resulting autoradiograph was a measure of surface Fc receptors expression. This procedure reliably distinguished Staphylococcus aureus strains which expressed different levels of surface Fc receptors. When applied to the study of group A streptococci, a number of Fc receptor-positive strains were identified. Unlike the homogeneous Fc receptor expression on individual colonies of the staphylococcal strains, a wide variation in the level of Fc receptor expression was observed within a given streptococcal strain. Group A streptococcal substrains which expressed high and low levels of surface Fc receptors could be isolated from replica plates.Secreted Fc receptors were measured by a simple modification of the blotting procedure in which the nitrocellulose was placed on the opposite side of the agar from the bacterial colonies. Secreted Fc receptors was electroblotted through the agar onto nitrocellulose and probed as described above. This approach readily detected nanogram quantities of secreted type I Fc receptor (protein A) from the Staphylococcus aureus Cowan strain. None of the group A streptococcal strains tested were found to secrete detectable quantities of Fc receptors.     

An in vitro model to assess pneumococcal adherence to nasopharyngeal cells under competition conditions

Pneumococcal conjugate vaccine (PCV7) reduces invasive disease and carriage caused by vaccine serotypes (VS). An increase in carriage and disease with non-vaccine serotypes (NVS) has been observed. We have developed an in vitro model with human nasopharyngeal (NP) epithelial cells (Detroit 562) to assess the adherence capacity of Streptococcus pneumoniae to NP cells in the presence or absence of a competing Pnc strain. Two hundred and fifty pneumococcal (Pnc) strains (10 strains per serotype for 7 VS and 18 NVS) were tested for their opacity phenotype. Strains exhibiting (> or =50%) the transparent phenotype (n=72) were evaluated for their adherence capacity to Detroit 562 cells. Mean adherence capacity (> or =129 CFU/well) to NP cells was high for VS 18C, 4, and 9V and for NVS 16F, 10A, and 6A. In the in vitro competition experiments, VS strains out-competed (42/108) or co-existed (43/108) with NVS strains for adherence to NP cells in most co-inoculations. By contrast, NVS (15C, 16F, 31, and 35B) out-competed with VS in only 9 of 108 co-inoculations. Serotype 16F out-competed or co-existed with some VS and NVS strains. This model may be used to identify Pnc strains of a given serotype with competitive potentials for replacement of VS in the nasopharynx and to screen Pnc strains for animal colonization models.     

Restriction Fragment Length Polymorphisms and Sequence Analysis: an Approach for Genotyping Infectious Pancreatic Necrosis Virus Reference Strains and Other Aquabirnaviruses Isolated from Northwestern Spain

Reference strains of infectious pancreatic necrosis virus resembling the 10 recognized serotypes and local isolates of aquabirnaviruses isolated in northwestern Spain from reservoirs (mollusks) and from asymptomatic and carrier cultured fish were genotyped by restriction fragment length polymorphism (RFLP) and nucleic acid sequence analyses. The RFLP analysis yielded seven genogroups, each of which was clearly correlated with a serotype. Sequence analysis of the three open reading frames provided quite similar results in terms of genogrouping. Based on the results of this study and in order to unify the two types of assays, we propose placing aquabirnaviruses into six genogroups, four of which can be subdivided into two genotypes based on a two-step restriction analysis. The genotyping corresponds with serotyping as follows: genogroup I includes two genotypes corresponding to serotypes A9 (genotype I.1) and A1 (genotype I.2); genogroup II corresponds to serotype A3; genogroup III includes genotypes III.1 (serotype A2) and III.2 (serotype B1); genogroups IV and V include two genotypes, each corresponding to serotypes A5, A6, A7, and A8 (genotypes IV.1, IV.2, V.1, and V.2, respectively);and genogroup VI corresponds to serotype A4. As expected, most local isolates belonged to genotype III.1 and genogroup II. However, a few local isolates corresponded to the American types of genogroup I. Finally, based on the results of this study and due to its simplicity, the two-step restriction analysis assay is proposed as a method for typing new isolates of aquabirnaviruses, and the results correspond to the results of conventional serotyping.     

Restriction fragment length polymorphisms and sequence analysis: an approach for genotyping infectious pancreatic necrosis virus reference strains and other aquabirnaviruses isolated from northwestern Spain

Reference strains of infectious pancreatic necrosis virus resembling the 10 recognized serotypes and local isolates of aquabirnaviruses isolated in northwestern Spain from reservoirs (mollusks) and from asymptomatic and carrier cultured fish were genotyped by restriction fragment length polymorphism (RFLP) and nucleic acid sequence analyses. The RFLP analysis yielded seven genogroups, each of which was clearly correlated with a serotype. Sequence analysis of the three open reading frames provided quite similar results in terms of genogrouping. Based on the results of this study and in order to unify the two types of assays, we propose placing aquabirnaviruses into six genogroups, four of which can be subdivided into two genotypes based on a two-step restriction analysis. The genotyping corresponds with serotyping as follows: genogroup I includes two genotypes corresponding to serotypes A9 (genotype I.1) and A1 (genotype I.2); genogroup II corresponds to serotype A3; genogroup III includes genotypes III.1 (serotype A2) and III.2 (serotype B1); genogroups IV and V include two genotypes, each corresponding to serotypes A5, A6, A7, and A8 (genotypes IV.1, IV.2, V.1, and V.2, respectively);and genogroup VI corresponds to serotype A4. As expected, most local isolates belonged to genotype III.1 and genogroup II. However, a few local isolates corresponded to the American types of genogroup I. Finally, based on the results of this study and due to its simplicity, the two-step restriction analysis assay is proposed as a method for typing new isolates of aquabirnaviruses, and the results correspond to the results of conventional serotyping.     

DNA homology of surface protein antigen A gene in mutans streptococci

1. A recombinant plasmid, pYA724, containing an 8.45 kb DNA fragment encoding surface protein antigen A (spaA) from Streptococcus sobrinus 6715 was used to examine the DNA homology of the spaA gene with chromosomal DNA of various mutans streptococci strains. 2. Restriction endonuclease BamHI-digested pYA724 DNA was radio-labeled by nick-translation, and a DNA-DNA hybridization experiment was carried out. pYA724 DNA hybridized with chromosomal DNA of serotypes a, c, d, e, f and g strains, but not with b by dot DNA-hybridization and Southern blot DNA hybridization. 3. Chromosomal DNAs were isolated from several serotype c Streptococcus mutans strains, digested with BamHI, and analyzed by Southern blot DNA hybridization. pYA724 DNA hybridized with different sizes and numbers of BamHI-digested DNA fragments of the chromosomal DNAs. 4. These data indicated that all mutans streptococci strains except serotype b have DNA homologous with the spaA gene, although within the same serotype strain the spaA gene has a diversity of arrangement within the chromosome.     

Genome diversification in phylogenetic lineages I and II of Listeria monocytogenes: identification of segments unique to lineage II populations

Thirteen different serotypes of Listeria monocytogenes can be distinguished on the basis of variation in somatic and flagellar antigens. Although the known virulence genes are present in all serotypes, greater than 90% of human cases of listeriosis are caused by serotypes 1/2a, 1/2b, and 4b and nearly all outbreaks of food-borne listeriosis have been caused by serotype 4b strains. Phylogenetic analysis of these three common clinical serotypes places them into two different lineages, with serotypes 1/2b and 4b belonging to lineage I and 1/2a belonging to lineage II. To begin examining evolution of the genome in these serotypes, DNA microarray analysis was used to identify lineage-specific and serotype-specific differences in genome content. A set of 44 strains representing serotypes 1/2a, 1/2b, and 4b was probed with a shotgun DNA microarray constructed from the serotype 1/2a strain 10403s. Clones spanning 47 different genes in 16 different contiguous segments relative to the lineage II 1/2a genome were found to be absent in all lineage I strains tested (serotype 4b and 1/2b) and an additional nine were altered exclusively in 4b strains. Southern hybridization confirmed that conserved alterations were, in all but two loci, due to absence of the segments from the genome. Genes within these contiguous segments comprise five functional categories, including genes involved in synthesis of cell surface molecules and regulation of virulence gene expression. Phylogenetic reconstruction and examination of compositional bias in the regions of difference are consistent with a model in which the ancestor of the two lineages had the 1/2 somatic serotype and the regions absent in the lineage I genome arose by loss of ancestral sequences.     

Molecular Characterization of the Recently Emerged Poultry Pathogen Ornithobacterium rhinotracheale by Multilocus Sequence Typing

Ornithobacterium rhinotracheale (ORT) is an economically important bacterial pathogen of turkeys and chickens worldwide. Since its first detection, a variety of typing methods have been used to gain basic knowledge about the bacterial population structure, an issue that still needs to be addressed. Serological characterization revealed at least 18 different serotypes (A-R) with ORT of serotype A to be predominate among poultry. This study aimed to establish a multilocus sequence typing (MLST) scheme for ORT that could easily be used by other laboratories and allows for worldwide comparison of sequence data. For this purpose, 87 ORT strains from different poultry hosts, geographical origins, years of isolation and serotypes were included in the analysis to identify correlations. Fourteen different sequence types (ST) were found. The most common ST1 was identified in 40 ORT strains from turkeys and chickens on 4 continents and in 3 different European countries. Together with ST9, both STs represented over three quarters (77%) of ORT strains used in the MLST analysis and included strains of frequently cross-reacting ORT serotypes A, E and I. Nine STs were only represented by one ORT strain and might indicate possible avian host, disease or serotype-specific relationships. In contrast, discrepancies between serotype and phylogenetic relatedness were clearly demonstrated by ORT strains that belonged to identical serotypes but differed in their ST. The overall identified low genetic diversity among strains isolated from turkeys and chickens independent of host and geographical origins suggests that ORT has only recently been introduced into domestic poultry and dispersed worldwide.     

Comparison of extracellular protein profiles of seven serotypes of mutans streptococci grown under controlled conditions

Extracellular proteins produced by the four human commensal species of mutans streptococci were analysed. The organisms used were Streptococcus mutans, serotypes c, e and f, Streptococcus cricetus, serotype a, Streptococcus rattus, serotype b, and Streptococcus sobrinus, serotypes d and g. They were grown in continuous culture at different generation times and pH values in media containing either glucose or fructose to determine the extent of variation in extracellular protein production that could occur for an individual strain. The results for different organisms grown under the same conditions were then compared. The total amount of protein of molecular mass greater than or equal to 60 kDa varied considerably with the growth conditions and with the strain. Generally more protein was present at a higher pH, conditions under which the organisms also form more lipoteichoic acid. With respect to individual protein components SDS-PAGE proved better than isoelectric focusing for detecting phenotypic responses by a particular strain to environmental changes and differences between the different strains. Differences in the molecular masses of protein components were particularly pronounced in the regions designated P1 (185-200 kDa), P2 (130-155 kDa) and P3 (60-95 kDa). Every strain produced at least one component in the P1 region that cross-reacted with antiserum to the purified protein from S. mutans serotype c, a protein which is indistinguishable from antigens B and I/II. Two components in the P2 region were dominant in the case of S. cricetus and S. sobrinus strains and showed glucosyltransferase (GTF) activity. GTF activity was also detected in the P3 region, particularly with S. mutans strains.     

Actinomyces georgiae sp. nov., Actinomyces gerencseriae sp. nov., designation of two genospecies of Actinomyces naeslundii, and inclusion of A. naeslundii serotypes II and III and Actinomyces viscosus serotype II in A. naeslundii genospecies 2

DNAs of type strains and representative members of Actinomyces groups from the human periodontal flora and from other habitats were compared by using the S1 nuclease procedure to determine their genetic relatedness. One rather common group from the human periodontal flora, previously called "Actinomyces D08," is phenotypically distinct from, and genetically unrelated to, previously described species. We propose the name of Actinomyces georgiae for this organism; the type strain is strain ATCC 49285. Another common group from the human periodontal flora is Actinomyces israelii serotype II, which was found genetically distinct from the type strain of A. israelii (serotype I) and from other previously described species of Actinomyces. We propose the name Actinomyces gerencseriae for this organism; the type strain is strain ATCC 23860. A. naeslundii serotype I strains were distinct from the other strains studied. A separate genospecies which included strains of A. naeslundii serotypes II and III and A. viscosus serotype II was delineated. Strains of Actinomyces serotype WVA 963 constitute an additional distinct genospecies. Because there are no reliable phenotypic tests, other than serological analyses, to differentiate Actinomyces serotype WVA 963 and the two genospecies of A. naeslundii, no taxonomic changes are proposed for these three genospecies.     

Genetic diversity among the T-protein genes of group A streptococci

T protein is a trypsin- and pepsin-resistant molecule on the surface of group A streptococci used as a serological tool to differentiate streptococci of this group. The purpose of this study was to determine the relatedness among the T protein genes of the 25 known T serotypes. DNA probes were constructed which represented various regions of the structural gene for the T6 protein, tee6. The probes were assayed for their ability to hybridize HindIII digests of chromosomal DNA from the 25 different T serotypes. Probe pTEE6.3, coding for the entire T6 protein, and pTEE6(1-299), coding for the amino-terminal half of T6, displayed the highest amount of homology, each binding to 10 of 25 T serotypes. Probes coding for sequences in the carboxy-terminal half of T6 showed considerably less homology among T serotypes with one probe hybridizing with only three out of 25. A synthetic oligonucleotide coding for the carboxy-terminal hydrophobic domain of T6, an area conserved to some degree among several bacterial surface proteins, showed homology with only seven out of 25 T serotypes. Hybridization with sequences outside the tee6 coding area provided additional information on the relatedness of certain sets of T serotypes according to restriction-fragment size heterogeneity. Clearly, there is considerable diversity among T-serotype genes. The data suggest that two or more families of structurally variant T proteins exist, which share only the property of proteolytic resistance and/or, perhaps, some biological function.     

Serological properties of Abiotrophia and Granulicatella species (nutritionally variant streptococci)

Serological variations were examined among 12 type or reference strains and 91 oral isolates of vitamin B6-dependent Abiotrophia and Granulicatella spp. Rabbits were immunized with whole cells of 12 selected strains and 10 typing antisera were obtained, which were unreactive with the Lancefield group A to G antigen preparations. The reactivity of the antisera and autoclaved cell surface antigen extracts was tested by double diffusion in agar gel and a capillary precipitin test. These typing antisera categorized all Abiotrophia defectiva strains, all except one Granulicatella elegans strain, three-quarters of the Granulicatella adiacens, and half of the Granulicatella paraadiacens into 8 serotypes and 2 subserotypes. The Granulicatella balaenopterae type strain was unserotypable. All A. defectiva strains were serotype I, some of which were divided into subserotype I-1 and/or I-5. The G. adiacens strains generally belonged to serotype II or III, and the G. paraadiacens strains to serotype IV, V or VI. All G. adiacens or G. paraadiacens serotype II strains were also subserotype I-5. The G. elegans strains were serotype VII or VIII. These Abiotrophia and Granulicatella serotypes were undetectable among 33 strains of the other 11 species including the bacteriolytic enzyme-producing but vitamin B6-independent strains of Streptococcus, Enterococcus, Dolosigranulum and Aerococcus. The proposed serotyping system for Abiotrophia and Granulicatella spp. would be helpful in the identification and classification of these unique coccal isolates in ecological and epidemiological studies.     

Molecular cloning and characterization of the spaB gene of Streptococcus sobrinus

A gene of Streptococcus sobrinus 6715 (serotype g) designated spaB and encoding a surface protein antigen was isolated from a cosmid gene bank. A 5.4 kb HindIII/AvaI DNA fragment containing the gene was inserted into plasmid pBR322 to yield plasmid pXI404. Analysis of plasmid-encoded gene products showed that the 5.4 kb fragment of pXI404 encoded a 195 kDa protein. Southern blot experiments revealed that the 5.4 kb chromosomal insert DNA had sequence similarity with genomic DNA of S. sobrinus 6715, S. sobrinus B13 (serotype d) and Streptococcus cricetus HS6 (serotype a). The recombinant SpaB protein (rSpaB) was purified and monospecific antiserum was prepared. With immunological techniques and the anti-rSpaB serum, we have shown: (1) that the rSpaB protein has physico-chemical and antigenic identity with the S. sobrinus SpaB protein, (2) the presence of cross-reactive proteins in the extracellular protein of serotypes a and d of the mutans group of streptococci and (3) that the SpaB protein is expressed on the surface of mutans streptococcal serotypes a, d and g.     

A 28-kilodalton fibronectin-binding protein of group a streptococci

Lipoteichoic acid (LTA) has been implicated as a major adhesin of group A streptococci that interacts with fibronectin (Fn). It has been suggested that protein adhesins may also be involved in the binding of Fn to streptococci. We searched for such a protein by transblotting membrane preparations from M types 5, 19, and 24 group A streptococci to nitrocellulose and reacting the blot with¹²⁵I-Fn. The Fn reacted with a 28-kDa polypeptide from all three serotypes of streptococci. Using affinity-purified antibodies to the 28-kDa protein in immunoblots of membrane preparations from various streptococci, we demonstrated that the 28-kDa protein is present in all 17 strains tested. Affinity-purified antibodies to the 28-kDa protein also reacted in varying degrees with intact streptococci, demonstrating that the antigen is exposed on the surface of intact organisms. Our results suggest that, in addition to LTA, group A streptococci contain a common Fn-binding moiety that is expressed as a major component of membrane preparations and that is accessible on the surface of streptococci for interactions with Fn.     

Characterization of group B streptococcal glyceraldehyde-3-phosphate dehydrogenase: surface localization,enzymatic activity,and protein-protein interactions

During characterization of the surface antigens of serotype III group B streptococci (GBS), a protein with an apparent M(r) of approximately 173,500 migrating on a SDS--polyacrylamide gel was found to have an N-terminal amino acid sequence identical to that of the plasmin receptor (Plr) of group A streptococci, a surface-localized glyceraldehyde-3-phosphate dehydrogenase (GAPDH). This work begins to characterize GBS GAPDH and to assess its functional activity on the cell surface. The 1.0-kb gapC gene of GBS was amplified by PCR. plr and gapC demonstrated 87% homology. An anti-Plr monoclonal antibody reacted with GBS whole cells, suggesting GBS GAPDH is surface localized. Multiple serotypes of GBS demonstrated functional GAPDH on their surfaces. The anti-Plr monoclonal antibody recognized GBS protein bands of approximately 41 and 173.5 kDa, by Western blot. Presumably, these represent monomeric and tetrameric forms of the GAPDH molecule. GBS GAPDH was demonstrated by Western blot analysis to interact with lys- and glu-plasminogens. Fluid-phase GBS GAPDH interacted, by means of ELISA, with immobilized lys-plasminogen, glu-plasminogen, actin, and fibrinogen. Enzymatically active GAPDH, capable of binding cytoskeletal and extracellular matrix proteins, is expressed on the surface of GBS.     

Biotyping of Propionibacterium acnes isolated from normal human facial skin

Biochemical and serological characteristics of 128 strains of Propionibacterium acnes isolated from the facial skin of healthy Japanese volunteers were compared with the three standard strains of the American Type Culture Collection, ATCC 6919, 11827, and 11828. Accordingly, the isolated strains of P. acnes were classified into five biotypes (B1 to B5) on the basis of fermentation tests of ribose, erythritol, and sorbitol. Two serotypes were distinguished by the agglutination test. P. acnes belonging to serotype I had galactose as a cell wall sugar, whereas those of serotype II lacked galactose. The strains of serotype I were distributed among all five biotypes (B1 to B5); however, those of serotype II consisted only of one biotype (B2). A term "sero-biotype" was introduced to differentiate and carefully classify the isolates. The predominant sero-biotypes differed with the individual and region of the facial skin. In general, strains of sero-biotype IB1, IB3, IB4, and IIB2 were more frequently isolated than those of sero-biotype IB2 and IB5. Thus, for routine assay work, serotyping of P. acnes as based on erythritol and sorbitol fermentation is both practical and applicable.