The 2.6-2.3 ka explosive eruptive period of the Pululahua dome complex, Ecuador: insights from pyroclast analysis.

Pululahua is an active volcano located 15 km north of Quito, Ecuador, that comprises sixteen dacitic-andesitic lava domes and a 13 km2 sub-rectangular depression formed between ~ 2.6 and ~ 2.3 ka. We use a detailed study of 70 flow and fall deposits that make up the pyroclastic sequence to show that the depression, previously classified as a caldera, was formed by numerous Vulcanian to (sub-) Plinian eruptions that destroyed both earlier and co-eruptive lava domes. We support this interpretation with field work, analysis of grain size distributions, density and components of 24 key deposits, supplemented by textural and petrologic analyses of 16 juvenile pyroclasts from throughout the pyroclastic sequence. These data document an alternation of (sub-) Plinian and Vulcanian eruptions dominated by denser juvenile material that preserves microtextural variations indicating changes in shallow level magma storage accompanying Vulcanian explosions. An exploratory examination of phenocryst textures and plagioclase and amphibole rim compositions suggests that much of the eruptive activity was driven by repeated inputs of less evolved magma into the Pululahua magmatic system. The inferred sequence of events provides a new hypothesis for the formation of the current morphology of Pululahua, including multiple episodes of both effusive and explosive eruptions accompanied by vent migration. Our findings offer an important insight into Pululahua's potential future hazard scenarios, which could affect millions of people. Supplementary Information: The online version contains supplementary material available at 10.1007/s00445-022-01590-4.

El Pululahua es un volcán activo situado 15 km al norte de Quito, Ecuador, que comprende dieciséis domos de lava dacítica-andesítica y una depresión sub-rectangular de 13 km² formada entre ~2,6 y ~2,3 mil años atrás. En este artículo realizamos un estudio detallado de 70 depósitos de flujos y caídas que componen la secuencia piroclástica para mostrar que la depresión, previamente clasificada como caldera, se formó en realidad por numerosas erupciones Vulcanianas a (sub-) Plinianas que destruyeron domos de lava pre-existentes y co-eruptivos. Fundamentamos esta interpretación con trabajo de campo, el análisis de densidad, componentes y distribución del tamaño de grano de 24 depósitos clave, además del análisis textural y petrológico de 16 piroclastos juveniles muestreados a lo largo de toda la secuencia. Los datos documentan una alternancia entre erupciones (sub-) Plinianas y Vulcanianas. La predominancia de material juvenil denso que conserva variaciones microtexturales dentro de los depósitos Vulcanianos indica cambios en el almacenamiento de magma a poca profundidad antes de estas erupciones. Un análisis exploratorio de las texturas de los fenocristales y de las composiciones de los bordes de plagioclasa y anfíbol sugiere que gran parte de la actividad eruptiva fue desencadenada por repetidas inyecciones de magma menos diferenciado al sistema magmático del Pululahua. La secuencia inferida de eventos eruptivos entre ~2,6 y ~2,3 mil años proporciona una nueva hipótesis para la formación de la actual morfología del Pululahua, incluyendo múltiples episodios de erupciones efusivas y explosivas acompañadas de la migración de los ventos eruptivos. Nuestros resultados aportan una nueva interpretación de los posibles futuros escenarios de peligro asociados al volcán Pululahua, los cuales podrían afectar a millones de personas.

Methamphetamine use, sexual activity, patient-provider communication, and medication adherence among HIV-infected patients in care, San Francisco 2004-2006.

While numerous studies examine methamphetamine use and associated risky sexual behaviors in HIV-uninfected individuals, few studies have surveyed HIV-infected individuals in the health care setting. To assess the frequency and trends of methamphetamine use, sexual activity, injection drug use, patient-provider communication, and medication adherence among HIV-infected persons in care, we administered a one-page anonymous survey in 2004 and 2006. The survey was conducted at the two University of California, San Francisco outpatient HIV clinics: at Moffitt Hospital (Moffitt), serving primarily privately insured patients, and at San Francisco General Hospital (SFGH), a county hospital serving primarily patients who are uninsured or publicly insured. In 2006, 39% of men who have sex with men (MSM), 33% of heterosexual men, and 11% of women reported methamphetamine use in the prior 12 months. Methamphetamine use was significantly associated with an increased number of sex partners among MSM and heterosexual men, and poor anti-retroviral medication adherence. Among MSM, methamphetamine use was more common at the SFGH clinic. Between 2004 and 2006, reported methamphetamine use in the last 12 months decreased among MSM at Moffitt (38 to 20%, p<0.01), but increased at SFGH (40 to 50%, p<0.05). Among methamphetamine users we found a high frequency of injection of methamphetamine, which increased at SFGH from 38 to 55%, p<0.05. Patient-provider communication regarding methamphetamine use has increased from 2004 to 2006 but no significant change has been found for providers asking patients about sexual activity. Overall, we found methamphetamine use to be common among HIV-infected patients in care, and associated with an increased number of sex partners, a high frequency of injection drug use, and poor adherence to anti-retroviral medications. These findings support the need for improved screening and clinic-based interventions to reduce and treat methamphetamine abuse and associated high risk sexual behaviors.

Azithromycin-resistant syphilis infection: San Francisco, California, 2000-2004.

BACKGROUND: The incidence of syphilis has been increasing in the United States since reaching a nadir in 2000. Several clinical trials have demonstrated that treatment with oral azithromycin may be useful for syphilis control. After reports of azithromycin treatment failures in San Francisco, we investigated the clinical and epidemiologic characteristics of patients with syphilis due to azithromycin-resistant Treponema pallidum infection. METHODS: We reviewed city-wide case reports and conducted molecular screening for patients seen at the San Francisco metropolitan STD clinic (San Francisco City Clinic) to identify patients who did not respond to azithromycin treatment for syphilis or who were infected with azithromycin-resistant T. pallidum. We conducted an epidemiologic investigation and retrospective case-control study to identify risk factors for acquiring syphilis due to azithromycin-resistant T. pallidum. RESULTS: From January 2000 through December 2004, molecular screening of 124 samples identified 46 azithromycin-resistant T. pallidum isolates and 72 wild-type T. pallidum isolates. Six instances of treatment failure were identified through record review. In total, we identified 52 case patients (one of whom had 2 episodes) and 72 control patients. All case patients were male and either gay or bisexual, and 31% (16 of 52) were infected with human immunodeficiency virus. Investigation of patient-partner links and a retrospective case-control study did not reveal a sexual network or demographic differences between cases and controls. However, 7 case patients had recently used azithromycin, compared with 1 control patient. Surveillance data demonstrated that azithromycin-resistant T. pallidum prevalence increased from 0% in 2000 to 56% in 2004 among syphilis cases observed at the San Francisco City Clinic. CONCLUSIONS: Azithromycin-resistant T. pallidum is widespread in San Francisco. We recommend against using azithromycin for the management of syphilis in communities where macrolide-resistant T. pallidum is present and recommend active surveillance for resistance in sites where azithromycin is used.

Interventions in the commercial sex industry during the rise in syphilis rates among men who have sex with men (MSM).

OBJECTIVE: Describe sexually transmitted disease/human immunodeficiency virus prevention interventions targeting men who have sex with men (MSM) in commercial sex venues (CSV). STUDY: Compilation of descriptive and evaluation data from the CDC 8-city MSM Syphilis Response on interventions conducted in bathhouses/sex clubs, circuit parties, the Internet, male sex workers, and the adult film industry. RESULTS: Interventions in the commercial sex industry (CSI) often involved multiple collaborative efforts between public health departments (PHD), community-based organizations (CBO), and CSV owners and managers. Education and condoms were provided at multiple venues, including circuit parties, bathhouses, and sex clubs. CBO staff reported one-on-one street and CSV outreach to engage MSM at risk. Evaluation data demonstrate that MSM exposed to media campaigns were more aware of syphilis and more likely to have been tested for syphilis than MSM who did not see the campaigns. CONCLUSIONS: PHD and CBO are using multiple means of reaching MSM in the CSI. Evaluations are needed to determine which of these efforts decreases syphilis transmission.

A carboxy-terminal processing protease gene is located immediately upstream of the invasion-associated locus from Bartonella bacilliformis.

A gene with homology to those encoding an unusual class of C-terminal processing proteases that flanks the invasion-associated locus ialAB of Bartonella bacilliformis has been identified. The 1302 bp gene, termed ctpA, is located immediately upstream of the ialA gene and encodes a predicted nascent product of 434 amino acids, producing a mature protein of 411 amino acid residues. The Bartonella CtpA appears to undergo autolysis in vitro, producing multiple products of 43-46 kDa, and a second group of products of 36-37 kDa. Production of CtpA in vivo gives a single product of 41.8 kDa. In addition to a computer-predicted N-terminal secretory signal sequence, the molecular mass difference in vivo versus in vitro indicates that CtpA is likely to be secreted and post-translationally modified. The full-length CtpA protein shows 30% identify to the CtpA protein of Synechocystis sp. 6803 (69% overall sequence similarity). The mature CtpA protein also has significant homology to the tail-specific protease (Tsp) of Escherichia coli, with 22% identify and 62% similarity to an internal region of the 660 amino acid Tsp. The CtpA protein does not appear to exhibit haemolysin, collagenase, or caseinase activity. The ctpA gene is conserved in all Bartonella species examined, as determined by hybridization analyses, but it was not found in Brucella abortus or E. coli. The ctpA gene does not directly affect the erythrocyte-invasion phenotype conferred by ialAB, but its homology to other stress-response processing proteases implies an important role in survival of this intracellular pathogen.