Aquitalea aquatilis sp. nov., isolated from Jungwon waterfall.

A Gram-stain-negative, facultative anaerobic, motile, short rods and yellow-pigmented bacterium, designated strain THG-DN7.12T, was isolated from water collected at Jungwon waterfall on Yongmun mountain, Republic of Korea. According to 16S rRNA gene sequence comparisons, strain THG-DN7.12T was found to be most closely related to Aquitalea denitrificans 5YN1-3T (98.9 % sequence similarity), Aquitalea magnusonii TRO-001DR8T (98.7 %) and Aquitalea pelogenes P1297T (98.0 %). The DNA-DNA relatedness between strain THG-DN7.12T and its phylogenetically closest neighbours was below 70.0 %. The strain's DNA G+C content was 59.7 mol%. The major polar lipid was found to be phosphatidylethanolamine. Summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and C16 : 0 were identified as the major fatty acids. Ubiquinone Q-8 was detected as the only respiratory quinone. These data supported the affiliation of strain THG-DN7.12T to the genus Aquitalea. Strain THG-DN7.12T was distinguished from related Aquitalea species by physiological and biochemical tests. Therefore, the novel isolate represents a novel species, for which the name Aquitalea aquatilis sp. nov. is proposed, with THG-DN7.12T as the type strain (=KACC 18847T=CCTCC AB 2016185T).

Cellulomonas aurantiaca sp. nov., isolated from a soil sample from a tangerine field.

A Gram-stain positive, facultatively aerobic, motile and rod-shaped bacterial strain, designated THG-SMD2.3T, was isolated from a soil sample collected in a tangerine field, Republic of Korea. According to the 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Cellulomonas and to be closely related to Cellulomonas fimi ATCC 484T (98.5%), Cellulomonas biazotea DSM 20112T (98.3%), Cellulomonas chitinilytica X.bu-bT (98.0%), Cellulomonas xylanilytica XIL11T (97.2%), Cellulomonas humilata ATCC 25174T (97.1%) and Cellulomonas composti TR7-06T (97.0%). The 16S rRNA gene sequence similarities with other current species of the genus Cellulomonas were in the range 95.4-96.6%. Catalase and oxidase tests were found to be positive. The DNA G+C content was determined to be 73.0 mol%. DNA-DNA hybridization values between strain THG-SMD2.3T and C. fimi ATCC 484T, C. biazotea DSM 20112T, C. chitinilytica X.bu-bT, C. xylanilytica XIL11T, C. humilata ATCC 25174T and C. composti TR7-06T were 58.1 ± 1.6%, 56.7 ± 0.8%, 30.3 ± 1.6%, 22.8 ± 1.6%, 19.9 ± 1.6%, and 13.5 ± 3.0%, respectively. Strain THG-SMD2.3T was also found to be able to grow at 20-42 °C, at 0-3% NaCl and at pH 5.5-10. The major fatty acids were identified as anteiso-C15:0, iso-C15:0, anteiso-C17:0 and iso-C14:0. The predominant menaquinone was identified as tetrahydrogenated menaquinones with nine isoprene units [MK-9(H4)]. The polar lipids were found to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids and two unidentified phospholipids. Based on these phenotypic, genotypic and phylogenetic characterisations strain THG-SMD2.3T (= KACC 19341T = CGMCC 1.16303T) is concluded to represent a novel species of the genus Cellulomonas, for which the name Cellulomonas aurantiaca sp. nov. is proposed.

Chitinophaga aurantiaca sp. nov., isolated from a soil sample from a tangerine field.

A Gram-stain-negative, facultatively anaerobic, non-motile and rod-shaped bacterial strain, designated THG-SD5.5T, was isolated from a soil sample collected in a tangerine field, Republic of Korea. According to the 16S rRNA gene sequence comparisons, the isolate was identified as a member of the genus Chitinophaga and to be closely related to Chitinophaga ginsengihumi KACC 17604T (97.9%) and Chitinophaga rupis KACC 14521T (97.5%). The 16S rRNA gene sequence similarities with other species of the genus Chitinophaga were in the range 92.8-95.5%. Catalase test was positive. Oxidase test was negative. The DNA G + C content was determined to be 46.1 mol%. DNA-DNA hybridization values between strain THG-SD5.5T and C. ginsengihumi KACC 17604T and C. rupis KACC 14521T were 45.1% and 15.6%, respectively. Strain THG-SD5.5T was also found to be able to grow at 24-33 °C, at 0-5% NaCl and at pH 5.5-9.0. The major fatty acids were identified as anteiso-C15:0, C16:0, anteiso-C17:0 and C18:0. The dominant respiratory quinone was identified as menaquinone-7 (MK-7). The polar lipids were found to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, an unidentified aminolipid, two unidentified phospholipids and three unidentified lipids. Based on these phenotypic, genotypic and phylogenetic characterisations, strain THG-SD5.5T (= KACC 19338T = CGMCC 1.16304T) is concluded to represent a novel species of the genus Chitinophaga, for which the name Chitinophaga aurantiaca sp. nov. is proposed.

Glaciecola amylolytica sp. nov., an amylase-producing bacterium isolated from seawater.

A Gram-stain-negative, aerobic, non-motile and coccus-shaped bacterium (THG-3.7T) was isolated from seawater. Growth occurred at 10-30 °C (optimum 25 °C), at pH 6-8 (optimum 7) and in the presence of 1-8 % (w/v) NaCl (optimum 4 %). Based on 16S rRNA gene sequence analysis, the nearest phylogenetic neighbours of strain THG-3.7T were identified as Paraglaciecola mesophila DSM 15026T (95.3 % similarity), Glaciecola pallidula DSM 14239T (95.2 %), Paraglaciecola aquimarina KCTC 32108T (95.1 %), Paraglaciecola arctica KACC 14537T (94.9 %), Glaciecola nitratireducens KCTC 12276T (94.7 %) and Paraglaciecola psychrophila CGMCC 1.6130T (94.7 %). 16S rRNA gene sequence similarities among strain THG-3.7T and other species were lower than 94.7 %. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified lipid and one unidentified aminolipid. The quinone system was composed of Q-8. The major fatty acids were C16 : 0, C18 : 1ω7c and summed feature 3 (C16 : 1ω7c and/or iso-C15 : 0 2-OH). The DNA G+C content of strain THG-3.7T was 47.9 mol%. On the basis of the data presented, strain THG-3.7T represents a novel species of the genus Glaciecola, for which the name Glaciecola amylolytica sp. nov. is proposed. The type strain is THG-3.7T (=KACC 19478T=CCTCC AB 2017258T).

Evaluation of in-vitro antimicrobial activity of Artemisia apiacea H. and Scutellaria baicalensis G. extracts.

PURPOSE: In traditional Korean medicine, Artemisia apiacea H. (ART) and Scutellaria baicalensis G. (SCU) are combined for the treatment of malaria and other malaria-like diseases. Because SCU is well-known as an antibacterial agent, the antimicrobial effect of a mixture of ART and SCU was investigated. METHODOLOGY: Plant samples were purchased from Kyungdong mart and extracted with 70 % ethanol. The in vitro antimicrobial activity of ART and SCU against pathogenic fungi (Aspergillus niger, Aspergillus oryzae, Candida albicans, Candida tropicalis and Candida glabrata), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) was evaluated using a broth microdilution assay, modified-disc diffusion and agar dilution methods with further CH2Cl2-fractionated ART, SCU and a mixture of ART/SCU (at a ratio of 3 : 5) (THAN-1). RESULTS: ART and SCU were effective against A. niger, C. albicans, B. subtilis and S. aureus. The range of minimum inhibitory concentration (MIC) values was 0.03125 to 4 mg ml-1 in the ART and SCU treatments. ART exhibited stronger activity than SCU. Interestingly, a 3 : 5 ratio mixture of ART and SCU (THAN-1) showed stronger antimicrobial activity than ART or SCU used individually. CONCLUSION: A treatment using a mixture of herbs such as THAN-1 would be useful in the suppression of the growth of pathogenic bacterial and fungal strains.

Ramlibacter rhizophilus sp. nov., isolated from rhizosphere soil of national flower Mugunghwa from South Korea.

A Gram-negative, aerobic, non-motile, long rods or coccoid without flagellum strain, designated THG-YS3.2.7T, was isolated from therhizosphere soil of a Mugunghwa flower collected from Kyung Hee University, Yongin, South Korea. Growth occurred at 10-40 °C (optimum 28-37 °C), at pH 6-8 (optimum 7) and at 0-5 % NaCl (optimum 1 %). The predominant ubiquinone was ubiquinone 8 (Q-8). The major cellular fatty acids were C10 : 0, C10 : 0 3OH, C16 : 0, C17 : 0, C17 : 0 cyclo, C18 : 0, C18 : 3ω6c (6,9,12), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1ω6c). The major polar lipids were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylcholine (PC). The DNA G+C content of strain THG-YS3.2.7T was 69.4 mol%. Based on 16S rRNA gene sequence analysis, the nearest phylogenetic neighbours of strain THG-YS3.2.7T were identified as Ramlibacter henchirensis DSM 14656T (97.92 %), Ramlibacter tataouinensis DSM 14655T (97.90 %), Ramlibacter solisilvae KACC 17567T (97.04 %). DNA-DNA hybridization values between strain THG-YS3.2.7T and R. henchirensis DSM 14656T, R. tataouinensis DSM 14655T, R. solisilvae KACC 17567T were 32.5±1.5, 43.1±1.1, 42.8±1.1 %, respectively. On the basis of the phylogenetic analysis, chemotaxonomic data, physiological characteristics and DNA-DNA hybridization data, strain THG-YS3.2.7T represent a novel species of the genus Ramlibacter, for which the name Ramlibacter rhizophilus sp. nov. is proposed. The type strain is THG-YS3.2.7T (=KCTC 52083T=CCTCC AB 2015357T).

Emticicia aquatilis sp. nov., isolated from a freshwater sample.

A Gram-stain-negative, facultatively anaerobic, non-motile, rod-shaped and yellow-pigmented bacterium, designated strain THG-DN6.14T, was isolated from a freshwater sample near Donghaksa temple in Daejeon, South Korea. On the basis of the results of 16S rRNA gene sequence comparisons, THG-DN6.14T was found to be most closely related to Emticicia sediminis JBR12T (99.1 % sequence similarity), Emticicia oligotrophica DSM 17448T (97.6 %), Emticicia aquatica HMF2925T (96.5 %), and Emticicia ginsengisoliGsoil 085T (94.4 %). The DNA-DNA relatedness between THG-DN6.14T and its phylogenetically closest neighbours was below 65.0 %. The DNA G+C content was 43.3 mol%. The major polar lipids were found to be phosphatidylethanolamine, an unidentified glycolipid and an unidentified aminoglycolipid. The major fatty acids were identified as C16 : 0, iso-C15 : 0, iso-C17 : 0 3-OH, and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The respiratory quinone was menaquinone MK-7. These data supported the affiliation of THG-DN6.14T to the genus Emticicia. THG-DN6.14Tcould be distinguished from related species of the genus Emticicia by physiological and biochemical tests. Therefore, the novel isolate represents a novel species, for which the name Emticicia aquatilis sp. nov. is proposed, with THG-DN6.14T (=KACC 18540T=CGMCC 1.15958T) as the type strain.

Aquaspirillum soli sp. nov., isolated from a soil sample.

A Gram-stain-negative, smooth, opaque, white-pigmented, helical-shaped, catalase- and oxidase-positive bacterium that was motile by means of bipolar tufts of flagella and grew under microaerophilic conditions, was isolated from a soil sample of a reed pond in Shangqiu, Henan province, PR China. The strain, designated THG-SQE6T, grows well at 25-42 °C, pH 6.5-7.5 and in the presence of 0-1 % (w/v) NaCl. hylogenetic analysis based on 16S rRNA gene sequences showed that strain THG-SQE6T was most closely related to Aquaspirillum serpens IAM 13944T (97.23 % 16S rRNA gene sequence similarity). The DNA G+C content of strain THG-SQE6T was 53.10 mol%. In DNA-DNA hybridization experiments, the DNA-DNA relatedness between strain THG-SQE6T and its closest phylogenetic neighbour was below 62.6 %. The predominant isoprenoid quinone detected in strain THG-SQE6T was ubiquinone-8 (Q-8). The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylserine, an unidentified phospholipid, an unidentified aminolipid and two unidentified lipids. The major fatty acids were identified as C12 : 0 3-OH, C16 : 0, C18 : 0, summed feature 3 and summed feature 8. These data support the affiliation of strain THG-SQE6T to the genus Aquaspirillum. Based on findings from the phenotypic, genotypic and phylogenetic characterization of strain THG-SQE6T, a novel species of the genus AquaspirillumnamedAquaspirillum soli sp. nov. is proposed. The type strain is THG-SQE6T (=KACC 18846T=CCTCC AB 2016081T).

Niabella hibiscisoli sp. nov., isolated from soil of a Rose of Sharon garden.

A Gram-stain-negative, strictly aerobic, non-motile, rod-shaped and yellow-pigmented bacterium, designated strain THG-DN5.5T, was isolated from soil of a Rose of Sharon garden in Daejeon, South Korea. According to 16S rRNA gene sequence comparisons, strain THG-DN5.5T was found to be most closely related to Niabella yanshanensis CCBAU 05354T (97.7 % sequence similarity), Niabella ginsengisoli GR10-1T (97.0 %), 'Niabella terrae' ICM 1-15 (96.0 %), Niabella soli DSM 19437T (95.7 %) and Niabella aquatica RP-2T (95.6 %). The DNA-DNA relatedness between strain THG-DN5.5T and its phylogenetically closest neighbours was below 50.0 %. The DNA G+C content was 43.1 mol%. The major polar lipid of strain THG-DN5.5T was found to be phosphatidylethanolamine. The major fatty acids were identified as C16 : 0, iso-C15 : 0, iso-C15 : 1 G, and iso-C17 : 0 3-OH. MK-7 was the only menaquinone present. These data supported the affiliation of strain THG-DN5.5T to the genus Niabella. Strain THG-DN5.5T was distinguished from related species of the genus Niabellaby physiological and biochemical tests. In conclusion, strain THG-DN5.5T represents a novel species of the genus Niabella, for which the name Niabella hibiscisolisp. nov. is proposed. The type strain is THG-DN5.5T (=KACC 18857T=CCTCC AB 2016086T).

Flavobacterium hibisci sp. nov., isolated from the rhizosphere of Hibiscus syriacus L.

A Gram-stain-negative, smooth, bright-yellow-pigmented, rod-shaped bacterial strain, slightly motile by gliding, catalase- and oxidase-positive and aerobic, but growing weakly under anaerobic conditions, was isolated from the rhizosphere of the flower mugunghwa (Hibiscus syriacus L.) located in Kyung Hee University, Yongin, Gyeonggi, South Korea. The strain named THG-HG1.4T grew at 15-35 °C, pH 6.5-9.0 and in the presence of 0-2.5 % (w/v) NaCl. The phylogenetic analysis based on 16S rRNA gene sequence showed that strain THG-HG1.4T was most closely related to Flavobacterium gyeonganense HME7524T (98.83 %) and Flavobacterium arsenitoxidans S2-3HT (97.28 %). The DNA G+C content of strain THG-HG1.4T was 41.2 mol%. In DNA-DNA hybridization, the DNA-DNA relatedness between strain THG-HG1.4T and its closest phylogenetic neighbour was below 64.1 %. The predominant isoprenoid quinone detected in strain THG-HG1.4T was menaquinone-6 (MK-6). The major polar lipids were found to be phosphatidylethanolamine, three unidentified lipids, two unidentified glycolipids and an unidentified aminolipid. The major fatty acids were identified as iso-C15 : 0, iso-C15 : 0 3-OH, C16 : 0, iso-C17 : 0 3-OH and summed feature 3. Thus, based on the report of the phenotypic, genotypic and phylogenetic characterization of strain THG-HG1.4T, it has been concluded that the novel isolate represents a novel species of the genus Flavobacterium.Flavobacterium hibisci sp. nov. is proposed, with THG-HG1.4T (=KACC 18852T=CCTCC AB 2016178T) as the type strain.

Novosphingobium lotistagni sp. nov., isolated from a lotus pond.

A Gram-staining-negative, aerobic, non-motile, rod-shaped and yellow-pigmented bacterium, designated strain THG-DN6.20T, was isolated from a lotus pond near Donghaksa temple in Daejeon, Republic of Korea. According to 16S rRNA gene sequence comparisons, strain THG-DN6.20T was found to be most closely related to Novosphingobium rosa IFO 15208T (97.6 % sequence similarity), Novosphingobium sediminicola HU1-AH51T (97.5 %) and Novosphingobium barchaimii LL02T (96.9 %). The DNA-DNA relatedness between strain THG-DN6.20T and its phylogenetically closest neighbours was below 60.0 %. The respiratory quinone and polyamine detected in strain THG-DN6.20T were ubiquinone Q-10 and spermidine, respectively. The DNA G+C content was 63.1 mol%. The major polar lipids were found to be phosphatidylethanolamine, diphosphatidylglycerol, sphingoglycolipid and phosphatidylcholine. The major fatty acids were identified as C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C14 : 0 2-OH. These data supported the affiliation of strain THG-DN6.20T to the genus Novosphingobium. Strain THG-DN6.20T could be distinguished from related species of the genus Novosphingobium by physiological and biochemical characteristics. Therefore, the novel isolate represents a novel species, for which the name Novosphingobium lotistagni sp. nov. is proposed, with THG-DN6.20T as the type strain (=KACC 18541T=CCTCC AB 2015354T).

Lysobacter rhizophilus sp. nov., isolated from rhizosphere soil of mugunghwa, the national flower of South Korea.

A Gram-staining-negative, aerobic, motile, rod-shaped, catalase- and oxidase-negative strain with one polar flagellum, designated THG-YS3.6T, was isolated from rhizosphere soil of a mugunghwa flower collected from Kyung Hee University, Yongin, South Korea. Growth occurred at 10-37 °C (optimum 25-30 °C), at pH 6-8 (optimum 7.0) and with 0-2.0 % NaCl (optimum 1 %). The isoprenoid quinone was ubiquinone-8 (Q-8). The major cellular fatty acids were iso-C11 : 0, iso-C11 : 0 3-OH, iso-C15 : 0, iso-C16 : 0, C16 : 1ω7c alcohol, C16 : 0, iso-C17 : 0 and summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl). The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylethanolamine, one unknown phospholipid, one unknown lipid and three unknown aminolipids. The DNA G+C content of strain THG-YS3.6T was 65.3 mol%. Based on 16S rRNA gene sequence analysis, the nearest phylogenetic neighbours of strain THG-YS3.6T were identified as Lysobacter yangpyeongensis KACC 11407T (98.7 %), Lysobacter oryzae KCTC 22249T (98.0 %), Lysobacter niabensis KACC 11587T (97.6 %) and Lysobacter terrae KACC 17646T (97.1 %). The DNA-DNA relatedness values between strain THG-YS3.6T and L. yangpyeongensis KACC 11407T, L. oryzae KCTC 22249T, L. niabensis KACC 11587T and L. terrae KACC 17646T were 53.8±1.0 %, 12.9±1.2 %, 10.9±0.6 % and 7.0±1.9 %, respectively. On the basis of the phylogenetic analysis, chemotaxonomic data, physiological characteristics and DNA-DNA hybridization data, strain THG-YS3.6T represents a novel species of the genus Lysobacter, for which the name Lysobacter rhizophilus sp. nov. is proposed. The type strain is THG-YS3.6T (=KCTC 52082T=CCTCC AB 2015358T).

Pedobacter humi sp. nov., isolated from a playground soil.

A Gram-stain-negative, aerobic, non-motile, rod-shaped and yellow-pigmented bacterium, designated strain THG S15-2T, was isolated from playground soil in Sindorim-dong, Guro-gu, Seoul, South Korea. According to 16S rRNA gene sequence comparisons, strain THG S15-2T was found to be related most closely to Pedobacter ginsengisoli Gsoil 104T (97.5 % similarity), Pedobacter panaciterrae Gsoil 042T (97.4 %), Pedobacter seoulensis THG-G12T (97.1 %) and Pedobacter caeni LMG 22862T (97.1 %). The level of DNA-DNA relatedness between strain THG S15-2T and its phylogenetically closest neighbours was below 30.0 %. The only isoprenoid quinone detected in strain THG S15-2T was menaquinone-7. The DNA G+C content was 45.9 mol%. The major polar lipid was phosphatidylethanolamine. The major component in the polyamine pattern was sym-homospermidine. The major fatty acids were identified as summed feature 3 (C16:1ω7c and/or C16:1ω6c), iso-C15:0 and C16:0. These data supported the affiliation of strain THG S15-2T to the genus Pedobacter. Strain THG S15-2T was distinguished from related Pedobacter species by physiological and biochemical tests. Therefore, strain THG S15-2T represents a novel species, for which the name Pedobacter humi sp. nov. is proposed. The type strain is THG S15-2T (= KCTC 42735T = CCTCC AB 2015293T).

Nocardioides albidus sp. nov., an actinobacterium isolated from garden soil.

A novel bacterial strain, designated THG-S11.7T, was isolated from garden soil in Incheon, South Korea. Cells of the strain were Gram-stain-positive, aerobic, non-motile cocci, and were catalase- and oxidase-positive. Colonies of the strain were white. Strain THG-S11.7T grew optimally at 28 °C, at pH 7.0 and in the presence of 2.0 % NaCl. 16S rRNA gene sequence analysis indicated that the strain was a member of the genus Nocardioides. Strain THG-S11.7T showed a 16S rRNA gene sequence similarity of 98.2 % to Nocardioides kongjuensis KCTC 19054T, 98.0 % to Nocardioides caeni KCTC 19600T, 97.9 % to Nocardioides daeguensis KCTC 19799T, 97.8 % to Nocardioides nitrophenolicus KCTC 047BPT, 97.6 % to Nocardioides aromaticivorans KACC 20613T, 97.5 % to Nocardioides simplex KACC 20620T and 97.0 % to Nocardioides ginsengisoli KCTC 19135T. DNA-DNA relatedness values between strain THG-S11.7T and the closest phylogenetic neighbours were below 45.0 % and the DNA G+C content of strain THG-S11.7T was 72.2 mol%. Strain THG-S11.7T was characterized chemotaxonomically as having ll-diaminopimelic acid in the cell-wall peptidoglycan and menaquinone MK-8(H4) as the predominant isoprenoid quinone. The major phospholipid was determined to be diphosphatidylglycerol. The major cellular fatty acids of strain THG-S11.7T were iso-C15 : 0, C16 : 0 and iso-C16 : 0. Based on the phenotypic, genotypic and phylogenetic analyses, it is proposed that the isolate represents a novel species of the genus Nocardioides, for which the name Nocardioides albidus sp. nov. is proposed. The type strain is THG-S11.7T ( = KCTC 39607T = CCTCC AB 2015297T).

Clients of female sex workers as a bridging population in Vietnam.

Understanding bridging behaviors of clients of female sex workers (FSWs) is important for projecting and intervening in the spread of sexually transmitted infections in Vietnam. The goals of the study were to determine HIV/STI prevalence amongst different bridging groups, identify factors associated with being potential and active bridgers, and assess the association of drug use and unsafe sex with HIV and/or STI prevalence. In April, 2007, 292 clients were anonymously interviewed at sex venues in a two-stage time-location cluster sampling survey, followed by HIV, syphilis, and HSV-2 testing. Based on condom use with both high-risk (FSWs) and low-risk (wives/girlfriends) sexual partners, clients were classified as unlikely, potential, or active bridgers. The majority of clients were potential or active bridgers (55.8%) who had a significantly higher prevalence of herpes simplex type 2 (HSV-2) (21% and 33%, respectively) than unlikely bridgers (8.7%). HIV seropositivity was 4.4-fold (95% CI 1.1-17.1) higher among those who were HSV-2-positive. Clients of FSWs may be playing a major bridging role in transmitting HIV and sexually transmitted infections (STIs) in Vietnam. An observed synergistic interaction between drug use and condom slippage/breakage emphasizes the importance of proper condom use, particularly among drug users.