The active site structure of Thalassiosira weissflogii carbonic anhydrase 1.

X-ray absorption spectroscopy at the Zn K-edge indicates that the active site of the marine diatom Thalassiosira weissflogii carbonic anhydrase is strikingly similar to that of mammalian alpha-carbonic anhydrase enzymes. The zinc has three histidine ligands and a single water at 1.98 A. This is quite different from the beta-carbonic anhydrases of higher plants in which zinc is coordinated by two cysteine thiolates, one histidine, and a water molecule. The diatom carbonic anhydrase shows no significant sequence similarity with other carbonic anhydrases and may represent an example of convergent evolution at the molecular level.

Regulation of carbonic anhydrase expression by zinc, cobalt, and carbon dioxide in the marine diatom Thalassiosira weissflogii.

TWCA1 is the major Zn-requiring isoform of carbonic anhydrase (CA) in the marine diatom Thalassiosira weissflogii. We have examined the roles that trace metals and CO(2) play in the regulation of TWCA1 expression over ranges of concentrations that bracket those encountered in the marine environment. Both steady-state levels of TWCA1 and the kinetics of induction were measured by western analysis. TWCA1 levels correlated well with cellular CA activity levels. TWCA1 was induced at a low CO(2) concentration but the level of induction, as determined by western analysis, was dependent on the availability of Zn. Co effectively substituted for Zn in regulating TWCA1 expression and promoting TWCA1 activity. Upon shift from low to high CO(2), the concentration of TWCA1 decreased. The expression of TWCA1 is diel cycle regulated, and cellular TWCA1 decreased during the dark phase. These results provide the basis for studying the expression of CA in field populations and, taken together with previous radiolabeling studies, provide strong evidence of in vivo metal substitution of Co for Zn in a CA. Our data also support the conclusion that TWCA1 plays a central role in carbon acquisition in T. weissflogii.

A biological function for cadmium in marine diatoms.

The oceanic distribution of cadmium follows closely that of major algal nutrients such as phosphate. The reasons for this "nutrient-like" distribution are unclear, however, because cadmium is not generally believed to have a biological function. Herein, we provide evidence of a biological role for Cd in the marine diatom Thalassiosira weissflogii under conditions of low zinc, typical of the marine environment. Addition of Cd to Zn-limited cultures enhances the growth rate of T. weissflogii, particularly at low pCO(2). This increase in growth rate is reflected in increased levels of cellular carbonic anhydrase (CA) activity, although the levels of TWCA1, the major intracellular Zn-requiring isoform of CA in T. weissflogii, remain low. (109)Cd label comigrates with a protein band that shows CA activity and is distinct from TWCA1 on native PAGE of radiolabeled T. weissflogii cell lysates. The levels of the Cd protein are modulated by CO(2) in a manner that is consistent with a role for this enzyme in carbon acquisition. Purification of the CA-active fraction leads to the isolation of a Cd-containing protein of 43 kDa. It is now clear that T. weissflogii expresses a Cd-specific CA, which, particularly under conditions of Zn limitation, can replace the Zn enzyme TWCA1 in its carbon-concentrating mechanism.

Antiretroviral medication compliance in patients with AIDS.

The paradigm of AIDS patient care has evolved to that of a chronic disease that is manageable with combination antiretroviral therapy. Intermittent adherence to antiretroviral regimens, however, has been associated with the selection of HIV mutations, resulting in drug-resistant virus. Medication compliance has become a vital component in the care of HIV-infected patients. This study was designed to assess the degree of medication compliance with zidovudine (ZDV) over a 2-month period among a convenience sample of 23 ambulatory patients with HIV infection. Enrollment took place during February to March 1995, when monotherapy with ZDV was considered the standard of care. Medication compliance was assessed by three methods: patient self-report determined by questionnaire, pharmacy refill records from the 3 months immediately before entry in the study, and an electronic monitoring system (Medication Event Management Systems [MEMS], Aprex Corp., Fremont, CA), which records the date and time of each opening of the medication vials. MEMS was utilized among a subgroup of eight participants over a 2-month period. Despite greater than 95% (22 of 23) of the subjects reporting that they believed ZDV was life prolonging, a majority took < or = 75% of the prescribed doses of ZDV as identified by both refill and MEMS methods. The mean percentage compliance over a 2-month period of observation for MEMS and pharmacy refill record review methods was 66% and 78%, respectively (p = 0.294). Among the subgroup of eight in the MEMS evaluation, 88% reported taking their ZDV according to the directions, all of the time. These results demonstrate that reliance upon patient self-report of medication compliance is less accurate than MEMS or pharmacy refill records, and that reliance on self-reporting could lead to erroneous assumptions of the patient's true drug compliance. In addition, the study suggests that pharmacy refill records may provide a method of assessing compliance that is equivalent to MEMS but is less experimental, and can easily be followed and interpreted by pharmacists and other clinicians caring for patients infected with HIV. Most importantly, relatively poor compliance rates demonstrated by MEMS raises serious concern for widespread development of HIV resistance to the more complicated, multiple-drug regimens in present use.

Primary prevention and rubella immunity: overlooked issues in the outpatient obstetric setting.

OBJECTIVE: To determine the knowledge of rubella immune status among practicing obstetrician-gynecologists in the United States and of rubella immunity policies covering healthcare workers in the obstetric-care office setting. DESIGN: Mailed survey questionnaire, August through December 1994. SETTING: Physicians from multiple-practice sites including private office, public institution, university or teaching hospital, and closed panel health maintenance organization settings. PARTICIPANTS: 3,302 practicing obstetrician-gynecologists, chosen by a systematic random sample from the AMA national physician database. MAIN OUTCOME MEASURES: Participants were defined as rubella immune if they reported knowledge of prior rubella vaccination or positive antibody titer. Knowledge of a policy for documenting rubella immunity among employees in the office-based practice setting also was assessed. RESULTS: Questionnaires were returned from 50% (1,666) of the 3,302 surveyed, and 96% (1,599) were evaluable. Approximately 20% (304/1,599) of the responding obstetrician-gynecologists did not have knowledge of documented rubella immunity, and the majority of office-based practices did not require documentation of rubella immunity in the following groups: physicians, 66% (723/1,094); office nurses, 62% (666/1,070); and other office staff, 69% (728/1,063). Sixty-two percent (993/1,599) of responding physicians had individual rubella serologies performed, with 916 known to be positive, 53 reported negative, and 24 reported unknown. Fifty-seven percent (918/1,599) reported receiving monovalent rubella vaccine or trivalent measles-mumps-rubella vaccine. Multiple logistic regression analysis revealed the following to be independent predictors of positive immune status among respondents: female gender (odds ratio [OR], 2.4; 95% confidence interval [CI95], 1.8-3.1), medical school graduation since 1980 (OR, 2.6; CI95, 2.0-3.3), providing obstetric or fertility services (OR, 1.5; CI95, 1.2-1.9), and group practice setting (> or = 5 physicians; OR, 1.2; CI95, 1.1-1.4). CONCLUSIONS: Nationally, nearly one of every five practicing obstetricians may not have documented rubella immunity, and the majority of office-based practices have no system for assuring such immunity. Rubella immunity should extend beyond the hospital setting, with consideration for requiring rubella immunity as a condition for employment. Methods for effective implementation and documentation of current guidelines need to be addressed, particularly in the office setting.

Multicenter clinical trials comparing cefotetan with moxalactam or cefoxitin as therapy for obstetric and gynecologic infections.

The clinical efficacy and safety of cefotetan was assessed in two multicenter clinical trials involving 335 evaluable patients hospitalized with obstetric and gynecologic infections. In Study I, cefotetan was compared with moxalactam and in Study II, cefotetan was compared with cefoxitin. The clinical response rate in Study I was 67 of 70 patients for cefotetan (96 percent) and 33 of 34 patients (97 percent) for moxalactam. In Study II, the clinical response rate was 138 of 147 patients in the cefotetan group (94 percent) and 76 of 84 patients in the cefoxitin group (91 percent). For the patients with bacteriologic response data, 196 of 205 cefotetan patients (96 percent), 23 of 24 moxalactam patients (96 percent), and 70 of 75 cefoxitin patients (93 percent) had a satisfactory bacteriologic response. Cefotetan was well tolerated and produced no major adverse reactions. The mean amount of cefotetan given was lower than that of moxalactam or cefoxitin.

Multicenter comparison of cefotetan and cefoxitin in the treatment of acute obstetric and gynecologic infections.

Two hundred eighty-seven women were treated in a multicenter, randomized, comparative study to compare the safety and efficacy of cefotetan every 12 hours with that of cefoxitin every 6 or 8 hours in the treatment of acute obstetric and gynecologic pelvic infections. The most frequent primary diagnoses in both groups were endometritis and pelvic inflammatory disease; 24 of these patients were also bacteremic. The mean duration of treatment was 5.2 and 5.4 days for the cefotetan and cefoxitin groups, respectively, and the total doses administered were 18.1 and 32.1 gm, respectively. The rate of clinical failure for the cefotetan group was 8.5% and 12.2% for the cefoxitin group. Laboratory and clinical adverse reactions were infrequent and none was serious; both antimicrobials were well tolerated. These results suggest the administration of cefotetan provided adequate clinical and bacteriologic effectiveness in the treatment of hospital- and community-acquired, polymicrobial obstetric and gynecologic pelvic infections.

Atypical manifestations of herpes simplex encephalitis.

The diagnosis of herpes simplex encephalitis is readily considered in patients with focal findings on neurologic and radiologic examinations. In the two patients we have described, the diagnosis was delayed because clinical findings were attributed to other medical conditions, and radiologic studies were nondiagnostic. A high index of suspicion and repeated neuroradiologic tests are recommended in patients with unexplained encephalitis.

Rocky Mountain spotted fever: a warm weather problem.

Rocky Mountain spotted fever occurs primarily in the warm weather months of April through September in the southeastern and south central United States. It is transmitted by the bite of ticks infected with the etiologic Rickettsia. This article reviews the epidemiology, clinical manifestations, diagnosis and therapy of Rocky Mountain spotted fever. Emphasis is placed on the dilemmas of early diagnosis and the necessity of early and often empirical antibiotic treatment of suspected cases.

Septic arthritis caused by Kingella kingae.

A normal part of the oral flora, Kingella kingae has seldom been recognized as the cause of serious clinical infections. We report a case of documented septic arthritis caused by K. kingae in an otherwise healthy infant. We suggest that it may be more common than thought based on the general unfamiliarity with this organism and the fact that several dozen clinical isolates have been identified by reference laboratories.

Induction and prevention of experimental arteriovenous fistula infections.

Arteriovenous fistulae (AVF) between the femoral vessels were prepared in 20 rabbits to determine if local endovascular infections could be induced and if antibiotic prophylaxis could prevent infection. Twenty-four hours after bacterial challenge with 10(6) Staphylococcus aureus all 20 AVF were culture positive, whereas 19 of the 20 contralateral, unoperated femoral vessels were sterile. Two rabbits with AVF, followed for 30 days after receiving staphylocci, had intermittently positive blood cultures and had positive cultures of the AVF and heart valves at autopsy. Two groups of ten rabbits with AVF received either prophylactic oxacillin or vancomycin 0.5 h before bacterial challenge. Only 2 of 10 animals receiving oxacillin and 1 of 10 receiving vancomycin had positive AVF cultures at 24 h, a significant reduction in the incidence of endovascular infection compared with that in controls (P less than 0.001 by Fisher's exact test). This model, which reliably results in infection, can be used to study the pathophysiology, prevention, and treatment of AVF infections.