Identification of key genes and molecular pathways in type 2 diabetes mellitus and polycystic ovary syndrome via bioinformatics analyses.

OBJECTIVE: Type 2 diabetes mellitus (T2DM) and polycystic ovary syndrome (PCOS) are highly prevalent endocrine system diseases. However, studies on the molecular mechanisms of T2DM and PCOS at the transcriptomic level are still few. Thus, we aimed to reveal the potential common genetic and molecular pathways between T2DM and PCOS via bioinformatics analyses. MATERIALS AND METHODS: We downloaded the GSE10946 and GSE18732 datasets for T2DM and PCOS, respectively, from the National Center for Biotechnology Information's Gene Expression Omnibus (GEO) database. These datasets were subjected to integrated differential and weighted gene co-expression network analyses (WGCNA) to screen common genes. Thereafter, functional enrichment and disease gene association analyses were performed, transcription factor (TF)-gene and TF-miRNA-gene regulatory networks were constructed, and finally, the relevant target drugs were identified. RESULTS: We identified common genes (BIRC3, DEPTOR, TNNL3, ADRA2A) in T2DM and PCOS. Pathway enrichment analysis depicted that the common genes were enriched in smooth muscle contraction, channel inhibitor activity, apoptosis, and tumor necrosis factor (TNF) signaling pathways. TFs such as SP7, KLF8, HCFC1, IRF1, and MLLT1 played key roles in TF regulatory networks. Orlistat was indicated to be an important gene-targeting drug. CONCLUSIONS: This study is the first study to explore four diagnostic biomarkers and gene regulatory networks for T2DM and PCOS. The findings of our study provide novel insights into the diagnosis and treatment of T2DM and PCOS.

The efficacy and safety of rotavirus vaccines in countries in Africa and Asia with high child mortality.

Rotavirus remains a leading cause of diarrhoeal morbidity and mortality in young children and rotavirus vaccines are critical for reducing global disease burden. This report addresses the performance of rotavirus vaccines in countries with high child mortality. We performed a sensitivity analysis as part of a systematic review on rotavirus vaccines to inform development of World Health Organization vaccine recommendations. The efficacy of four prequalified vaccines against severe rotavirus gastroenteritis was similar across high mortality settings in Asia and Africa. Within the first year following vaccination, vaccine efficacy for the four vaccines ranged from 48% to 57% while in the second year, efficacy ranged from 29% to 54%. The four vaccines showed no increase in intussusception risk in these settings. All four vaccines appear to prevent significant numbers of severe rotavirus gastroenteritis episodes with no measurable increase in intussusception risk in high mortality settings in Africa and Asia.

DUSP22 promotes senescence of HS-1 skin cancer cells through triggering MAPK signaling pathway.

The article "DUSP22 promotes senescence of HS-1 skin cancer cells through triggering MAPK signaling pathway, by X.-D. Zhao, C. Huang, R.-X. Wang, S.-A. Wang, published in Eur Rev Med Pharmacol Sci 2018; 22 (22): 7819-7825-DOI: 10.26355/eurrev_201811_16406-PMID: 30536326" has been withdrawn from the authors due to substantial deficiency in the experimental design. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/16406.

Disrupting a phospholipase A2 gene increasing lipid accumulation in the oleaginous yeast Yarrowia lipolytica.

AIMS: Phospholipase A2 (PLA2 ) is a diverse superfamily that hydrolyzes fatty acyl ester bonds at the sn-2 position of phospholipids. The correlation between phospholipid metabolism and the anabolism of neutral lipids remains unclear in yeasts. This study aims to explore the effects of PLA2 on lipid accumulation in the oleaginous yeast Yarrowia lipolytica. METHODS AND RESULTS: This study identified an actively expressed phospholipase A2 gene (PLA2-3, YAIL0_E16060g) in Y. lipolytica by quantitative PCR analysis. The gene PLA2-3 was disrupted in the strain po1gΔKu70 by homologous recombination and in the strain po1g-G3 by a CRISPR-Cas9 system, which caused an increase in stress sensitivity while the cell growth was not altered under fermentative conditions. Lipid production was performed in both flasks and bioreactors. The results showed that the lipid titre and lipid content were improved over 25% and 8-30%, respectively, in PLA2-3 disrupted strains compared to the controls. CONCLUSIONS: Disruption of the phospholipase PLA2-3 gene could effectively improve lipid production in Y. lipolytica. SIGNIFICANCE AND IMPACT OF THE STUDY: This study presented a strategy on improving the lipid production of oleaginous yeasts and a similar strategy might be used in other oleaginous microbes.

DUSP22 promotes senescence of HS-1 skin cancer cells through triggering MAPK signaling pathway.

OBJECTIVE: Skin cancer severely threatens the public health. Dual-specificity protein phosphatase 22 (DUSP22) characterizes with multiple roles regulating cell growth, proliferation and gaining. This study aims to investigate the regulatory role of DUSP22 on aging of skin cancer cells and clarify molecular mechanisms, along with potential application value. PATIENTS AND METHODS: HS-1 skin cancer cells were transfected with DUSP22 by liposome transfection approach. Western blot assay was used to evaluate the effects of DUSP22 on aging protein of HS-1 cells, and activation of mitogen-activated protein kinase cascade (MAPK) signal pathway. Real-time PCR (RT-PCR) and Western blot assay were used to examine the DUSP22 expression in HS-1 cancer cells. Meanwhile, the correlation between P53 protein and aging was also investigated. RESULTS: Transfection of DUSP22 plasmid significantly elevated DUSP22 expression in HS-1 skin cancer cells compared to un-transfected cells (p<0.05), and activated MAPK to induce cell aging. Transfection of small interfere RNA (siRNA) DUSP22 significantly suppressed DUSP22 expression in HS-1 cancer cells, inhibited MAPK signal pathway, and decreased aging proteins P53 and P21 compared to the untreated group (p<0.05). DUSP22 was downregulated in HS-1 skin cancer cells, with MAPK signal pathway inhibition, and lower aging protein P53 expression. DUSP22 expression was positively correlated with aging protein P53 (p<0.05). CONCLUSIONS: DUSP22 facilitated HS-1 skin cancer cell aging via activating MAPK signal pathway, possibly providing novel strategy against skin cancer.

How I investigate Clonal cytogenetic abnormalities of undetermined significance.

Myelodysplastic syndromes are a group of hematopoietic stem cell diseases characterized by cytopenia(s), morphological dysplasia, and clonal hematopoiesis. In some patients, the cause of cytopenia(s) is uncertain, even after thorough clinical and laboratory evaluation. Evidence of clonal hematopoiesis has been used to support a diagnosis of myelodysplastic syndrome in this setting. In patients with cytopenia(s), the presence of clonal cytogenetic abnormalities, except for +8, del(20q) and -Y, can serve as presumptive evidence of myelodysplastic syndrome. Recent advances in next-generation sequencing have detected myeloid neoplasm-related mutations in patients who do not meet the diagnostic criteria for myelodysplastic syndrome. Various terms have been adopted to describe these cases, including clonal hematopoiesis of indeterminate potential (CHIP) and clonal cytopenia of undetermined significance (CCUS). Similarly, studies have shown that certain chromosomal abnormalities, including ones commonly detected in myelodysplastic syndrome, may not be associated necessarily with an underlying myelodysplastic syndrome. These clonal cytogenetic abnormalities of undetermined significance (CCAUS) are similar to CHIP and CCUS. Here, we review the features of CCAUS, distinguishing CCAUS from clonal cytogenetic abnormalities associated with myelodysplastic syndrome, and the potential impact of CCAUS on patient management.

EGF-mediated inhibition of ubiquitin-specific peptidase 24 expression has a crucial role in tumorigenesis.

In this study, several cancer-related proteins (Bax, p300, E2F4 and securin) have been proven to be substrates of ubiquitin-specific peptidase 24 (USP24), and relevance has been shown between USP24 and its substrates in samples from clinical lung cancer patients. Silencing USP24 increases the cancer formation by inhibiting cellular apoptosis and increasing cellular proliferation. Epidermal growth factor (EGF) treatment, and the KrasG12D and EGFRL858R mutations decrease USP24 protein stability via EGF- or CDK1-mediated phosphorylation at Ser1616, Ser2047 and Ser2604. Knockdown of USP24 decreases Bax and p300 levels, and reduces Ku70 acetylation, thereby preventing cancer cell apoptosis. In addition, knockdown of USP24 increases cell cycle progression by enhancing the G1-S transition and metaphase-anaphase transition. The molecular mechanism involves a decrease in the USP24 level, which reduces the expression of E2F4 and its partner TFDP1, and thus increases the G1/S transition. In conclusion, the USP24 level was decreased during the early stage of cancer and the mitotic stage of the cell cycle to regulate its substrates p300, Bax, E2F4 and securin, resulting in decreased cell apoptosis and increased cell cycle progression and, thus, cancer formation.

Variants of ubiquitin-specific peptidase 24 play a crucial role in lung cancer malignancy.

Ubiquitin is a critical modifier regulating the degradation and function of its target proteins during posttranslational modification. Here we found that ubiquitin-specific peptidase 24 (USP24) is highly expressed in cell lines with enhanced malignancy and in late-stage lung cancer clinical samples. Studying single-nucleotide polymorphisms (SNPs) of USP24 using genomic DNA of lung cancer patients revealed an increase in SNP 7656C/T. When using RNA specimens instead of the genomic DNA of lung cancer patients, we found significant increases in the ratios of variants 930C/T and 7656T/C, suggesting that variants at these two sites are not only caused by the SNP of DNA but also by the RNA editing. USP24-930T and USP24-7656C increase USP24 expression levels by increasing RNA stability. Knocking down USP24 increased Suv39h1 level through a decrease in mouse double-minute 2 homolog levels, thus enhancing lysine-9 methylation of histone H3, and resulting in the prevention of lung cancer malignancy. In conclusion, as USP24 variant analysis revealed a higher ratio of variants in blood specimens of lung cancer patients than that in normal individuals, USP24-930T and USP24-7656C might be useful as diagnostic markers for cancer detection.

A study on the protective role of doxycycline upon dopaminergic neuron of LPS-PD rat model rat.

OBJECTIVE: To investigate the protective role of doxycycline upon the dopaminergic neuron of the lipopolysaccharide-Parkinson disease (LPS-PD) model rat and its mechanism. MATERIALS AND METHODS: Animals were randomly divided into three groups: normal control group, LPS group and doxycycline intervention. Group; establishing The PD model was created by injecting LPS stereo-tactically into the substantia nigra; observing the changes in the dopaminergic neurons and the major histocompatibility complex II (MHC II) positive microglia before and after the intervention of doxycycline with immunohistochemical staining. Using the HPLC-ED (high performance liquid chromatography-electrochemical detector) to test the changes in the striatal dopamine (DA), and DOPAC (dihydroxy phenyl acetic acid) content; adopting Western blotting was adopted to test the expression of the substantia nigra microglia MHC II (major histocompatibility complex II) protein. RESULTS: After the intervention of doxycycline, in the LPS group, the surviving dopamine neurons in the substantia nigra rose from 38% ± 5% to 79% ± 4% (p < 0.01); striatal DA and DOPAC content of the LPS group increased from 4.89 ± 0.27 and 0.70 ± 0.07 to 7.00 ± 0.34 and 1.10 ± o. 10 respectively (p < 0.01). The average number of rotation induced intraperitoneal injection of apomorphine of the animals in the LPS group reduced from (208 ± 14); time/30 min to (80 ± 12) times/30 min (p < 0.01); while the number of the MHC II positive cells in the substantia nigra pars compacta in the LPS group reduced from 835 ± 82 to 354 ± 59 (p < 0.01); Western blotting of the MHC II protein expression showed a significant reduction. CONCLUSIONS: Doxycycline can inhibit degeneration of LPS-induced dopaminergic neurons. Its neuroprotective function is achieved by downregulating the microglia MHC II expression.

Study on the carotid atherosclerotic plaque of patients suffering from ischemic cerebrovascular disease by 64 slices CT.

OBJECTIVE: To explore the correlation between the features of a carotid plaque of patients suffering from carotid atherosclerosis and ischemic cerebrovascular disease by 64 slices computed tomography (CT). PATIENTS AND METHODS: One hundred patients with carotid atherosclerosis were divided into the ischemic event group (n=48) and non-ischemic event group (n=52). The features of the carotid plaque were detected by 64 slices CT. RESULTS: One hundred and thirteen plaques were found in the ischemic event group. The proportions of fatty, calcified, and mixed plaque were 35.4%, 30.1%, and 34.5%. There are 78 plaques found in the non-ischemic event group. The proportions of fatty, calcified, and mixed plaque were 21.8%, 51.3%, and 26.9%. The distribution difference between the three types of plaques was statistically significant (p<0.05). The proportions of mixed plaque composed mainly of fatty plaque were 64.1% and 23.8%. These two constituent ratios are significantly different from those of statistical processing (p<0.01). There are 10 cases of plaque ulceration out of the 100 cases, among which eight are from the ischemic event group and two cases from the other group. After statistical processing, the incidence rates of plaque ulceration from these two groups are significantly different (p<0.05). CONCLUSIONS: The 64 slices CT can accurately present the morphological features of the carotid plaque. It indicates that the fatty plaque, mixed plaque composed mainly of fatty plaque and ulcerative plaque can cause ischemic cerebrovascular events.

Effect of mecobalamin treatment on the recovery of patients with posterior communicating artery aneurysm inducing oculomotor nerve palsy after operation.

OBJECTIVE: This research aims to evaluate the effect of mecobalamin treatment on the recovery of patients with posterior communicating artery aneurysm inducing oculomotor nerve palsy after embolization. PATIENTS AND METHODS: A total of 56 patients with oculomotor nerve palsy (ONP) attributed to posterior communicating artery (PcomA), were admitted and treated in the Neurology Department of Hubei College of Medicine affiliated to Xiangyan Hospital from July 2007 to January 2013, and 55 of them were followed up as well. Among them 27 patients were given embolization treatment and 28 received embolization + mecobalamin treatment. The recovery condition of ONP were followed and compared one year after the treatment. RESULTS: All patients were followed up for more than a year. And 31 patients (56.4%) out of 55 achieved complete recovery, 19 (34.5%) attained partial recovery and 5 (9.1%) had no recovery from ONP. Whereas, 20 patients (71.4%) in the embolization + mecobalamin treatment group achieved complete recovery and 11 (40.7%) in the embolization treatment group achieved partial recovery, and the comparative difference was statistically significant (p < 0.05). CONCLUSIONS: Endovascular is highly efficacious treatment for ONP-inducing PcomA and can promote the recovery of oculomotor nerve palsy after embolism.

Anti-HMGB1 antibody reduces weight gain in mice fed a high-fat diet.

Insulin resistance in obesity is believed to be propagated by adipose tissue and liver inflammation. HMGB1 is a multifunctional protein that is pro-inflammatory when released from cells. It has been previously demonstrated that anti-HMGB1 antibody reduces atherosclerotic lesion pro-inflammatory cells and progression of atherosclerosis in a mouse model. To test the potential beneficial role of blocking HMGB1 in adipose tissue and liver inflammation in mice fed an obesogenic diet, we administered anti-HMGB1 antibody to C57Bl/6 mice fed a high (60%)-fat diet. The mice were treated with weekly injections of an anti-HMGB1 antibody or anti-KLH antibody (isotype control) for 16 weeks. Mice that received the anti-HMGB1 antibody gained less weight than the control-treated animals. Anti-HMGB1 treatment also reduced hepatic expression of TNF-alpha and MCP-1, molecules that promote inflammation. However, adipose tissue inflammation, as measured by gene expression analyses and immunohistochemistry, did not differ between the two groups. There also were no differences in glucose or insulin tolerance between the two groups. When feeding mice a high-fat diet, these data suggest that HMGB1 may have a crucial role in weight gain and liver inflammation.

Flow cytometry immunophenotypic analysis of Philadelphia-negative myeloproliferative neoplasms: Correlation with histopathologic features.

BACKGROUND: Compared with the proven utility of flow cytometry immunophenotyping (FCI) analysis in the workup of myelodysplastic syndromes (MDS), immunophenotypic alterations in myeloproliferative neoplasms (MPN) have been less studied and the potential utility of FCI is not defined. METHODS: Bone marrow (BM) samples of 83 Philadelphia-negative MPN patients were assessed by multicolor FCI including 27 with essential thrombocythemia (ET); 17 polycythemia vera (PV); 33 primary myelofibrosis (PMF) and 6 MPN-unclassifiable (MPN-U). The time interval from initial diagnosis of MPN to FCI analysis was 18 months (0-370). Ninety-five age-matched MDS patients with a similar BM blast count were included for comparison. RESULTS: Immunophenotypic alterations, either in CD34(+) cells or myelomonocytic cells, were detected in 82 of 83 (99%) MPN cases. FCI abnormalities were more frequently observed in cases with substantial myelofibrosis but not different between PMF and fibrotic stage of ET/PV. Furthermore, FCI abnormalities were more frequent in cases with ≥5% BM blasts and/or circulating blasts (P = 0.006); as well as cases with an abnormal karyotype (P = 0.036); but not associated with morphologic dysplasia or JAK2 mutation status. Comparing with MDS, FCI abnormalities were overall less pronounced in MPN cases (P = 0.001). CONCLUSIONS: MPNs exhibit frequent immunophenotypic alterations, more pronounced in cases with adverse histopathologic features. These findings illustrate that immunophenotypic alterations are a part of constellational findings in MPN, and correlate progressively with disease stage. The study results also suggest a role of FCI in diagnosis of MPN and monitoring disease over time and after therapy.

Multi-color flow cytometric immunophenotyping for detection of minimal residual disease in AML: past, present and future.

Current chemotherapeutic regimens achieve CR in a large percentage of patients with AML. However, relapse after CR remains a significant problem. The presence of leukemic cells at levels too low to be detected by conventional microscopy, termed minimal residual disease (MRD), has been associated with an increased risk of relapse and shortened survival. Detection of MRD requires the use of highly sensitive ancillary techniques. Multi-color flow cytometric immunophenotyping is a sensitive method for quick and accurate detection of MRD. Use of this method in patient management may result in lower rates of relapse and improved survival, and is an effective means of assessing novel therapeutic agents. This method can be used in the vast majority of patients with AML, regardless of the immunophenotypic, cytogenetic and molecular genetic abnormalities present. Unfortunately, conflicting data regarding optimum methods of measurement and reporting, as well as the expertize required to interpret results have limited broad application of this technique. We provide a broad overview of this technique, including its advantages and limitations, and discuss the methods employed at our institution. We also review several possible areas of future investigation.

Toll-like receptor alterations in myelodysplastic syndrome.

Recent studies have implicated the innate immunity system in the pathogenesis of myelodysplastic syndromes (MDS). Toll-like receptor (TLR) genes encode key innate immunity signal initiators. We recently identified multiple genes, known to be regulated by TLRs, to be overexpressed in MDS bone marrow (BM) CD34+ cells, and hypothesized that TLR signaling is abnormally activated in MDS. We analyzed a large cohort of MDS cases and identified TLR1, TLR2 and TLR6 to be significantly overexpressed in MDS BM CD34+ cells. Deep sequencing followed by Sanger resequencing of TLR1, TLR2, TLR4 and TLR6 genes uncovered a recurrent genetic variant, TLR2-F217S, in 11% of 149 patients. Functionally, TLR2-F217S results in enhanced activation of downstream signaling including NF-κB activity after TLR2 agonist treatment. In cultured primary BM CD34+ cells of normal donors, TLR2 agonists induced histone demethylase JMJD3 and interleukin-8 gene expression. Inhibition of TLR2 in BM CD34+ cells from patients with lower-risk MDS using short hairpin RNA resulted in increased erythroid colony formation. Finally, RNA expression levels of TLR2 and TLR6, as well as presence of TLR2-F217S, are associated with distinct prognosis and clinical characteristics. These findings indicate that TLR2-centered signaling is deregulated in MDS, and that its targeting may have potential therapeutic benefit in MDS.

Sp1 phosphorylation by cyclin-dependent kinase 1/cyclin B1 represses its DNA-binding activity during mitosis in cancer cells.

Sp1 is important for the transcription of many genes. Our previous studies have shown that Sp1 is degraded in normal cell, but it is preserved in cancer cells during mitosis and exists a priori in the daughter cells, ready to engage in gene transcription and thereby contributes to the proliferation and survival of cancer cells. The mechanism by which Sp1 is preserved in cancer cells during mitosis remains unknown. In this study, we observed that Sp1 strongly colocalized with cyclin-dependent kinase 1 (CDK1)/cyclin B1 during mitosis. Moreover, we showed that Sp1 is a novel mitotic substrate of CDK1/cyclin B1 and is phosphorylated by it at Thr 739 before the onset of mitosis. Phospho-Sp1 reduced its DNA-binding ability and facilitated the chromatin condensation process during mitosis. Mutation of Thr739 to alanine resulted in Sp1 remaining in the chromosomes, delayed cell-cycle progression, and eventually led to apoptosis. Screening of Sp1-associated proteins during mitosis by using liquid chromatography/mass spectrometry indicated the tethering of Sp1 to myosin/F-actin. Furthermore, phospho-Sp1 and myosin/F-actin appeared to exist as a congregated ring at the periphery of the chromosome. However, at the end of mitosis and the beginning of interphase, Sp1 was dephosphorylated by PP2A and returned to the chromatin. These results indicate that cancer cells use CDK1 and PP2A to regulate the movement of Sp1 in and out of the chromosomes during cell-cycle progression, which may benefit cancer-cell proliferation.

TCR-Vbeta flow cytometric analysis of peripheral blood for assessing clonality and disease burden in patients with T cell large granular lymphocyte leukaemia.

AIMS: T cell large granular lymphocytes (T-LGLs) are commonly increased in reactive conditions as well as T-LGL leukaemia. This differential diagnosis often requires a combined assessment of clonality and tumour burden. In this study we assessed the utility of flow cytometric (FC) analysis of T cell receptor beta chain variable region (TCR-Vbeta) expression by using 24 antibodies reactive to 70% of the TCR-Vbeta repertoire. METHODS: Analyses were performed on peripheral blood samples obtained from 20 patients with a confirmed diagnosis of T-LGL leukaemia and 18 patients without known T cell lymphoproliferative diseases. RESULTS: The results were compared with TCR gene rearrangement status assessed by PCR. By FC analysis, 19/20 T-LGL leukaemia cases were CD3+CD8+ and one case was CD3+CD4+. All the cases demonstrated at least one immunophenotypic aberration, with altered CD5 expression being most frequent. Abnormal Vbeta expression was detected by FC in 19 of 20 (95%) T-LGL leukaemia cases, but in none of the controls; this showed 100% concordance with TCR gene rearrangement studies. In addition to establishing clonality, FC Vbeta analysis enables calculation of absolute numbers of clonal T cells; this is important in monitoring tumour burden after treatment. CONCLUSIONS: It is concluded that FC Vbeta analysis is a fast, reliable and quantitative method that can simultaneously assess T-LGL leukaemia clonality and tumour burden.

Trisomy 11 in myelodysplastic syndromes defines a unique group of disease with aggressive clinicopathologic features.

Trisomy 11 in myelodysplastic syndromes (MDS) is rare, with undefined clinical significance and is currently assigned to the International Prognostic Scoring System (IPSS) intermediate-risk group. Over a 15-year period, we identified 17 MDS patients with trisomy 11 either as a sole abnormality (n=10) or associated with one or two additional alterations (n=7), comprising 0.3% of all MDS cases reviewed. Of 16 patients with Bone Marrow material available for review, 14 (88%) patients presented with excess blasts, 69% patients evolved to acute myeloid leukemia (AML) in a 5-month median interval and the median survival was 14 months. For comparison, we studied 19 AML patients with trisomy 11 in a noncomplex karyotype, of which, a substantial subset of patients had morphologic dysplasia, and/or preexisting cytopenia(s)/MDS. Genomic DNA PCR showed MLL partial tandem duplication in 5 of 10 MDS and 7 of 11 AML patients. A review of literature identified 17 additional cases of MDS with trisomy 11, showing similar clinicopathologic features to our patients. Compared with our historical data comprising 1165 MDS patients, MDS patients with trisomy 11 had a significantly inferior survival to patients in the IPSS intermediate-risk cytogenetic group (P=0.0002), but comparable to the poor-risk group (P=0.97). We conclude that trisomy 11 in MDS correlates with clinical aggressiveness, may suggest an early/evolving AML with myelodysplasia-related changes and is best considered a high-risk cytogenetic abnormality in MDS prognostication.

Using strain typing to characterise a fluoroquinolone-resistant Neisseria gonorrhoeae transmission network in southern California.

OBJECTIVE: We investigated the initial outbreak of fluoroquinolone-resistant Neisseria gonorrhoeae (QRNG) in southern California with analysis of transmission using strain typing. METHODS: Surveillance for QRNG was conducted between 2000 and 2002 in southern California, including epidemiology and strain typing by a combination of antibiogram, auxotype, serovar, Lip type and amino acid alteration patterns in the quinolone-resistance determining region of GyrA and ParC. Combining epidemiological data with strain typing, we describe the emergence of QRNG outbreak strains using risk factor analysis and transmission networks. RESULTS: Two outbreak strains accounted for 82% of isolates. Both strains required proline, were Lip type 17c, had amino acid alterations 91> Phe in GyrA and 87> Arg in ParC, but they differed by their serovar, IB-3C8 versus IB-2H7, 2G2. Outbreak strains were positively associated with men who have sex with men (MSM), adjusted odds ratio (AOR) 23.9 (95% confidence interval (CI) 2.2 to 261) and negatively associated with travel history: AOR 0.05, (95% CI 0.0 to 0.6). Network analysis demonstrated that 17 cases were connected by sexual contacts and/or public venues including bars, bathhouses/sex clubs, and internet sites. CONCLUSIONS: QRNG may have become established among Californian MSM through an identified transmission network of southern Californian bars, bathhouses and internet sites.