Comparison of Infrared Thermal Detection Systems for mass fever screening in a tropical healthcare setting

Objectives

Fever screening systems, such as Infrared Thermal Detection Systems (ITDS), have been used for rapid identification of potential cases during respiratory disease outbreaks for public health management. ITDS detect a difference between the subject and ambient temperature, making deployment in hot climates more challenging. This study, conducted in Singapore, a tropical city, evaluates the accuracy of three different ITDS for fever detection compared with traditional oral thermometry and self-reporting in a clinical setting.

Study design

This study is a prospective operational evaluation conducted in the Singapore military on all personnel seeking medical care at a high-volume primary healthcare centre over a one week period in February 2014.

Methods

Three ITDS, the STE Infrared Fever Screening System (IFSS), the Omnisense Sentry MKIII and the handheld Quick Shot Infrared Thermoscope HT-F03B, were evaluated. Temperature measurements were taken outside the healthcare centre, under a sheltered walkway and compared to oral temperature. Subjects were asked if they had fever.

Results

There were 430 subjects screened, of whom 34 participants (7.9%) had confirmed fever, determined by oral thermometer measurement. The handheld infrared thermoscope had a very low sensitivity (29.4%), but a high specificity (96.8%). The STE ITDS had a moderate sensitivity (44.1%), but a very high specificity (99.1%). Self-reported fevers showed good sensitivity (88.2%) and specificity (93.9%). The sensitivity of the Omnisense ITDS (89.7%) was the highest among the three methods with good specificity (92.0%).

Conclusion

The new generation Omnisense ITDS displayed a relatively high sensitivity and specificity for fever. Though it has a lower sensitivity, the old generation STE ITDS system showed a very high specificity. Self-reporting of fever was reliable. The handheld thermograph should not be used as a fever-screening tool under tropical conditions.

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The new generation fever screening system displayed a relatively high sensitivity and specificity for fever.

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Self-reporting of fever was reliable compared to measured temperature.

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The handheld thermograph should not be used as a fever-screening tool under tropical conditions.

Performance of case definitions for influenza surveillance

Influenza-like illness (ILI) case definitions, such as those from the European Centre for Disease Control and Prevention, World Health Organization (WHO) and United States Centers for Disease Control and Prevention, are commonly used for influenza surveillance. We assessed how various case definitions performed during the initial wave of influenza A(H1N1) pdm09 infections in Singapore on a cohort of 727 patients with two to three blood samples and whose symptoms were reviewed fortnightly from June to October 2009. Using seroconversion (≥ 4-fold rise) to A/California/7/2009 (H1N1), we identified 36 presumptive influenza A(H1N1)pdm09 episodes and 664 episodes unrelated to influenza A(H1N1)pdm09. Cough, fever and headache occurred more commonly in presumptive influenza A(H1N1)pdm09. Although the sensitivity was low (36%), the recently revised WHO ILI case definition gave a higher positive predictive value (42%) and positive likelihood ratio (13.3) than the other case definitions. Results including only episodes with primary care consultations were similar. Individuals who worked or had episodes with fever, cough or sore throat were more likely to consult a physician, while episodes with Saturday onset were less likely, with some consultations skipped or postponed. Our analysis supports the use of the revised WHO ILI case definition, which includes only cough in the presence of fever defined as body temperature ≥ 38 °C for influenza surveillance.

Medical response to the 2009 Sumatra earthquake: health needs in the post-disaster period

INTRODUCTION

This paper provides an overview of cases seen by the Singapore Armed Forces (SAF) medical and surgical teams in the 2009 Sumatra earthquake and discusses the role of militaries in the acute phase of a disaster.

METHODS

Two SAF primary healthcare clinics prospectively collected patient medical information for comparison. Descriptive analysis of the Emergency Department (ED) and surgical case records was performed.

RESULTS

1,015 patients were seen by the two primary healthcare clinics. In both Koto Bangko and Pariaman, respiratory-related conditions were the most common diagnoses (47.2% and 30.6%, respectively), followed by musculoskeletal/joint conditions (31.6% and 20.6%, respectively). In the ED, 55% and 27% of the 113 patients had trauma-related and infective-related diagnoses, respectively. Lacerations and contusions were the most common forms of trauma. Lung infection was the most common infective diagnosis seen at the ED. The number of ED cases was high during the first week and gradually declined in the second week. 56% of the 102 surgical procedures were performed on dirty or infective wounds. Fractures requiring fixation comprised 38% of surgical procedures.

CONCLUSION

Medical aid remains an important component of the overall humanitarian response. Militaries could play an important role in disaster response due to their ability to respond in a timely fashion and logistic capabilities. Pre-launch research on the affected area and knowledge on disaster-specific injury patterns would impact the expertise, equipment and supplies required. The increasing evidence base for disaster preparedness and medical response allows for better planning and reduces the impact of disasters on affected populations.

The benign nature of acute dengue infection in hospitalized older adults in Singapore

OBJECTIVES

In Singapore, dengue primarily affects adults. This study aimed to determine if older dengue patients in Singapore have greater morbidity and mortality.

METHODS

All laboratory diagnosed dengue patients admitted to Tan Tock Seng Hospital in 2004 were retrospectively reviewed. Cases were re-classified into dengue fever and dengue hemorrhagic fever based on World Health Organization criteria. Demographic, clinical, laboratory, and outcome data of patients aged > or = 60 years and <60 years were collected.

RESULTS

Of 1971 laboratory confirmed dengue cases, 66 were aged > or = 60 years. Older patients were significantly less likely to be male (44% vs. 64%), and more likely to have diabetes (17% vs. 2%), hypertension (48% vs. 4%), ischemic heart disease (6% vs. 0.1%), hyperlipidemia (18% vs. 1%), and secondary dengue infections (64% vs. 34%). Clinical features were similar except older patients were significantly less likely to report fever (92% vs. 99%), or have leukopenia (32% vs. 51%) or hemoconcentration (0 vs. 5%) on admission. Older patients had similar dengue hemorrhagic fever, bleeding, hypotension, severe thrombocytopenia, and elevated transaminase rates. Length of hospital stay, risk of intensive care unit admission, and outcome of death were not statistically different.

CONCLUSIONS

Despite greater co-morbidity and secondary dengue infection, older dengue patients in Singapore did not have greater morbidity or mortality.

Decision tree algorithm in deciding hospitalization for adult patients with dengue haemorrhagic fever in Singapore

OBJECTIVES

To develop a simple decision tree for clinicians to decide between hospitalization and outpatient monitoring of adult dengue patients.

METHOD

Retrospective cohort study on all laboratory-diagnosed dengue patients admitted in 2004 to Tan Tock Seng Hospital, Singapore. Demographic, clinical, laboratory and radiological data were collected, and cases classified as dengue fever (DF) or dengue haemorrhagic fever (DHF) using World Health Organization criteria. To develop the decision tree, we used chi-squared automatic interaction detector (CHAID) with bi-way and multi-way splitting. The resulting trees were pruned to achieve the highest sensitivity with the shortest tree.

RESULTS

In 2004, 1973 probable and confirmed adult dengue patients were admitted; DF comprised 1855 (94.0%) and DHF 118 (6.0%) of the cases. The best decision tree prediction had three branches, consisting of a history of clinical bleeding, serum urea, and serum total protein. This decision tree had a sensitivity of 1.00, specificity of 0.46, positive predictive value of 7.5%, and negative predictive value of 100%. The overall accuracy of the decision tree was 48.1%. The test sensitivity and specificity compared favourably with other predictive probability equations and sophisticated laboratory tests, and would prevent 43.9% of mild DF cases from hospitalization.

CONCLUSIONS

A simple decision tree is effective in predicting DHF in the clinical setting for adult dengue infection.

Do young adults with uncomplicated dengue fever need hospitalisation? A retrospective analysis of clinical and laboratory features

INTRODUCTION

Approximately 80 percent of all notified cases of dengue infections in Singapore were hospitalised from 2000 to 2005. We aimed to determine if hospitalised dengue patients had significant morbidity and mortality, and if admissions were in accordance with previously-published admission criteria.

METHODS

The medical records of the first 20 patients with laboratory-confirmed dengue from two consecutive months in three time periods were retrospectively reviewed. Demographical, clinical and laboratory data on admission, during hospitalisation and on discharge, were compared.

RESULTS

There were 120 patients with a mean age of 35 years. Males comprised 77 percent and foreign workers 51 percent. Of the published admission criteria, 33 percent had vomiting, 22 percent diarrhoea, 13 percent abdominal pain, 18 percent bleeding and one patient had hypotension. 30 percent were above the minimum platelet threshold of 80,000/microL, but 50 percent had safe levels of platelets between 50,000 and 80,000/microL. Dengue haemorrhagic fever occurred in 4 percent with no death. After admission, platelet nadir was below 20,000/microL in only 9 percent and below 10,000/microL in only 2 percent of cases. Bleeding did not correlate with platelet count. Medical referral to the hospital was significantly associated with thrombocytopenia, while self-referral was significantly associated with vomiting.

CONCLUSION

Severe adverse outcome among young adults with uncomplicated dengue fever is rare. Instead of hospitalisation, daily outpatient monitoring with symptomatic treatment and medical leave may be a safe and feasible alternative.

Management of enteroviral conjunctivitis outbreaks in the Singapore military in 2005

Between 8 August and 9 October 2005, tropical Singapore experienced a national epidemic of acute viral conjunctivitis. We report the epidemiological and virological findings of outbreaks of viral conjunctivitis in military facilities during the same time period, and the outbreak control measures taken. Outbreaks of viral conjunctivitis were identified by medical officers in military medical facilities. Epidemiological and virological investigations were carried out, and a standard set of control measures was instituted for each outbreak upon detection. Eight outbreaks of viral conjunctivitis occurred in the time period, corresponding to the national outbreak. Delayed detection and institution of preventive measures during the outbreaks were associated with delayed effectiveness of the control measures. Every delay in outbreak detection by one day resulted in a delay in terminating the outbreak by 0.82 days (p = 0.01). Coxsackievirus A24 was identified from some of the conjunctival swab samples taken.

Influenza and the pandemic threat

With the increasing concern of an imminent influenza pandemic, Singapore and many other countries have been developing preparedness plans. Influenza affects an estimated 20 percent of the population of Singapore annually, and local outbreaks can last for more than 12 weeks and occur at different periods of the year. The 1968 pandemic in Singapore had a clinical attack rate of about 20 percent and resulted in infections with fever that lasted up to five days. However, absenteeism from work due to seasonal influenza-like illnesses was estimated to be less than one day per person in Singapore. The next pandemic in Singapore is predicted to cause an average of 1,105 deaths and 3,338 hospitalisations, while a severe pandemic will cause more healthcare damage. Preventive strategies include national public health initiatives, vaccination, anti-viral therapy, and hygiene measures. To develop effective preparedness plans, it is important for healthcare workers to understand the disease's epidemiology, outcomes, and treatment and prevention strategies available.

Disaster relief and initial response to the earthquake and tsunami in Meulaboh, Indonesia

The Singapore Humanitarian Assistance Support Group deployed a team of 32 medical relief workers to Meulaboh, Indonesia to provide medical assistance for victims of the 26 December earthquake and tsunami disaster. The team was deployed at a primary healthcare clinic at an internally displaced persons' (IDP) camp and at the sole hospital's emergency and surgical departments. The team saw a total of 1841 patients, 1371 at the clinic and 446 at the hospital's emergency department, and performed surgery on 24 patients. Tsunami-related trauma cases accounted for 31.8% (142) of cases at the emergency department, 1.6% (22) of cases at the clinic, and 91.7% (22) of surgeries. This paper details the difficulties and lessons learnt by the team, including the lack of important resources for healthcare delivery. Water, sanitation, hygiene, and vector control were some of the problems faced, with the goal to provide the most effective public health for the greatest number of people given the limited resources available.

Addressing the stability of C-capped dipeptide efflux pump inhibitors that potentiate the activity of levofloxacin in Pseudomonas aeruginosa

Synthetic optimization of a biologically labile class of dipeptides that function as efflux pump inhibitors to potentiate the antibacterial agent levofloxacin in Pseudomonas aeruginosa has led to the discovery of a related series of compounds that are completely stable in a variety of biological matrices. Other than the stability profile, the in vitro profile of the new series is essentially identical to that observed with the original one. A prototypical compound from the new series demonstrates potentiation in an in vivo model of infection.

Stereochemical elucidation and total synthesis of dihydropacidamycin D, a semisynthetic pacidamycin

Hydrogenation of the C(4') exocyclic olefin of the pacidamycins has been shown to produce a series of semisynthetic compounds, the dihydropacidamycins, with antimicrobial activity similar to that of the natural products. Elucidation of stereochemistry in the pacidamycins has been completed through a campaign of natural product degradation experiments in combination with the total synthesis of the lowest-molecular weight dihydropacidamycin, dihydropacidamycin D. The stereochemical identities of the tryptophan and two alanine residues contained in pacidamycin D have been shown to be of the natural (S) configuration, and the unique 3-methylamino-2-aminobutyric acid contained in this series of antibiotics has been shown to be of the (2S,3S) configuration. Finally, the stereochemistry obtained by hydrogenation of the C(4')-C(5') exocyclic olefin has been shown to be (R) at the C(4') nucleoside site.

Identification and characterization of inhibitors of multidrug resistance efflux pumps in Pseudomonas aeruginosa: novel agents for combination therapy

Whole-cell assays were implemented to search for efflux pump inhibitors (EPIs) of the three multidrug resistance efflux pumps (MexAB-OprM, MexCD-OprJ, MexEF-OprN) that contribute to fluoroquinolone resistance in clinical isolates of Pseudomonas aeruginosa. Secondary assays were developed to identify lead compounds with exquisite activities as inhibitors. A broad-spectrum EPI which is active against all three known Mex efflux pumps from P. aeruginosa and their close Escherichia coli efflux pump homolog (AcrAB-TolC) was discovered. When this compound, MC-207,110, was used, the intrinsic resistance of P. aeruginosa to fluoroquinolones was decreased significantly (eightfold for levofloxacin). Acquired resistance due to the overexpression of efflux pumps was also decreased (32- to 64-fold reduction in the MIC of levofloxacin). Similarly, 32- to 64-fold reductions in MICs in the presence of MC-207,110 were observed for strains with overexpressed efflux pumps and various target mutations that confer resistance to levofloxacin (e.g., gyrA and parC). We also compared the frequencies of emergence of levofloxacin-resistant variants in the wild-type strain at four times the MIC of levofloxacin (1 microg/ml) when it was used either alone or in combination with EPI. In the case of levofloxacin alone, the frequency was approximately 10(-7) CFU/ml. In contrast, with an EPI, the frequency was below the level of detection (<10(-11)). In summary, we have demonstrated that inhibition of efflux pumps (i) decreased the level of intrinsic resistance significantly, (ii) reversed acquired resistance, and (iii) resulted in a decreased frequency of emergence of P. aeruginosa strains that are highly resistant to fluoroquinolones.

Discovery of RWJ-54428 (MC-02,479), a new cephalosporin active against resistant gram-positive bacteria

The discovery of RWJ-54428 (MC-02,479), a new cephalosporin displaying promising activity against sensitive and resistant Gram-positive bacteria, is described. Progressive structural modification from the previously reported 3-phenylthiocephem MC-02,331 afforded an overall increase in potency against MRSA while retaining other key properties such as acceptable solubility and serum binding. Evaluation of the in vitro potency and in vivo efficacy of a series of closely related compounds resulted in selection of RWJ-54428 (MC-02,479) for further studies.

SAR studies of anti-MRSA non-zwitterionic 3-heteroarylthiocephems

SAR studies in a series of 3-heteroarylthio substituted cephalosporins established that high activity against methicillin-resistant Staphylococcus aureus (MRSA) can be achieved with various heteroaryl substituents. Early results showed that highly lipophilic 3-heteroarylthio substituents, which were necessary for anti-MRSA activity, caused high affinity of such cephems toward serum proteins. Our earlier published efforts described discovery of zwitterionic cephems MC-02,331 and RWJ-54428 (MC-02,479), where serum binding was reduced by employing basic, positively charged functionalities attached to the 3-heteroarylthio substituent. In order to avoid low solubility problems associated with most such zwitterionic cephalosporins a wide variety of non-basic heteroaryl substituents was tested (non-zwitterionic cephems are more easily formulated as water soluble sodium salts for intravenous administration). Considerable reduction in serum binding was obtained in some analogs while maintaining high anti-MRSA potency.

Antibiotic resistance versus small molecules, the chemical evolution

Two discovery approaches directed to addressing the problem of increasing bacterial resistance are described. The first is a program to build activity against methicillin-resistant Staphylococcus aureus (MRSA) into the cephalosporin class of antibacterials, by enhancing affinity for PBP2a, the penicillin-binding protein responsible for this resistance. Through stepwise improvement in potency, human serum binding, solubility, and betalactamase stability, a stable of new compounds with excellent potential as anti-MRSA agents was realized. From this set was chosen MC-02, 479 (RWJ-54428), which is now undergoing extensive preclinical evaluation. The second approach explores the uridyl peptide family of antibiotics, inhibitors of bacterial translocase (mraY), whose members include the pacidamycins, mureidomycins, and napsamycins. Access to a diverse set of analogs by total synthesis was catalyzed by the discovery that hydrogenation of the 4'-exoenamidofuranosyl moiety causes no loss in biological activity. Indepth exploration of SAR required (1) establishment of the absolute stereochemistry of the central diaminobutyric acid (DABA) moiety and (2) determination of the stereochemistry of the 4'-substituent on the deoxyfuranose unit. The former was accomplished by comparison of DABA derived from degradation of a natural product pacidamycin with a sample synthesized from L-threonine. The biological activity of one member of a synthesized library of possible stereoisomers of the natural product established the absolute stereochemistry of the remaining centers. A variety of analogs of the natural product were prepared utilizing the synthetic methods developed, and their biological activities provide important insights into the specificity and spectrum of the antibiotic class.

What's new in the antibiotic pipeline

Many advances have recently been made in the development of chemotherapeutic agents for bacterial infections. As a consequence of problematic antimicrobial-resistant bacteria, research is now directed towards narrow-spectrum agents rather than broad-spectrum agents. Further, orally active agents have always been desirable, but today's cost-saving environment, in line with a desire to minimize treatment costs, values reduced administration costs and keeping patients out of the hospital. There has been a recent increase in research into orally active antibacterial agents, such as carbapenems and cephalosporins, and non-glycopeptide natural products.

Use of a genetic approach to evaluate the consequences of inhibition of efflux pumps in Pseudomonas aeruginosa

Drug efflux pumps in Pseudomonas aeruginosa were evaluated as potential targets for antibacterial therapy. The potential effects of pump inhibition on susceptibility to fluoroquinolone antibiotics were studied with isogenic strains that overexpress or lack individual efflux pumps and that have various combinations of efflux- and target-mediated mutations. Deletions in three efflux pump operons were constructed. As expected, deletion of the MexAB-OprM efflux pump decreased resistance to fluoroquinolones in the wild-type P. aeruginosa (16-fold reduction for levofloxacin [LVX]) or in the strain that overexpressed mexAB-oprM operon (64-fold reduction for LVX). In addition to that, resistance to LVX was significantly reduced even for the strains carrying target mutations (64-fold for strains for which LVX MICs were >4 microg/ml). We also studied the frequencies of emergence of LVX-resistant variants from different deletion mutants and the wild-type strain. Deletion of individual pumps or pairs of the pumps did not significantly affect the frequency of emergence of resistant variants (at 4x the MIC for the wild-type strain) compared to that for the wild type (10(-6) to 10(-7)). In the case of the strain with a triple deletion, the frequency of spontaneous mutants was undetectable (<10(-11)). In summary, inhibition of drug efflux pumps would (i) significantly decrease the level of intrinsic resistance, (ii) reverse acquired resistance, and (iii) result in a decreased frequency of emergence of P. aeruginosa strains highly resistant to fluoroquinolones in clinical settings.

Discovery of MC-02,331, a new cephalosporin exhibiting potent activity against methicillin-resistant Staphylococcus aureus

A systematic approach toward building activity against methicillin-resistant staphylococci into the cephalosporin class of beta-lactam antibiotics is described. Initial work focused on finding the optimal linkage between the cephem nucleus and a biphenyl pharmacophore, which established that a thio linkage afforded potent activity in vitro. Efforts to optimize this activity by altering substitution on the pharmacophore afforded iodophenylthio analog MC-02,002, which although highly potent against MRSA, was also highly bound to serum proteins. Further work to decrease serum protein binding showed that replacement of the iodo substituent by the positively-charged isothiouronium group afforded potent activity and reduced serum binding, but insufficient aqueous solubility. Solubility was enhanced by incorporation of a second positively-charged group into the 7-acyl substituent. Such derivatives (MC-02,171 and MC-02,306) lacked sufficient stability to staphylococcal beta-lactamase enzymes. The second positive charge was incorporated into the cephem 3-substituent in order to utilize the beta-lactamase-stable aminothiazolyl(oximino)acetyl class of 7-substituents. These efforts culminated with the discovery of bis(isothiouroniummethyl)phenylthio analog MC-02,331, whose profile is acceptable with respect to potency against MRSA, serum binding, aqueous solubility, and beta-lactamase stability.

Synthesis and antimicrobial evaluation of TAN-1057A/B analogs

TAN-1057A-D, dipeptides isolated from bacteria Flexibacter sp. PK-74 and PK-176, are new antibiotics with potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). We describe, in detail, the synthesis of several TAN-1057A/B analogs by a convergent route featuring a new method to construct the cyclic amidinourea functional group. The biological activity of these substances against methicillin-resistant Staphylococcus aureus (MRSA) is reported.

ZD9583, an orally effective thromboxane A2 synthase inhibitor and receptor antagonist with a sustained duration of action in rat and dog

The thromboxane A2 (TXA2) synthase inhibitory activity and the TXA2 receptor (TP-receptor) blocking action of ZD9583 ((4Z)-6-[(2S,4S,5R)-2-(1-[2-cyano-4-methylphenoxy]-1-methylethyl) -4-(3-pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid) has been evaluated in-vitro by use of whole blood and platelets from man, and ex-vivo by use of platelets and whole blood from rats and dogs. ZD9583 caused concentration-dependent inhibition of human platelet microsomal TXA2 production with an IC50 of 0.017 +/- 0.003 microM; this inhibition was associated with an increase in prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) formation. ZD9583 also inhibited collagen-stimulated TXA2 synthesis in whole blood from man, rat and dog giving IC50 values of 0.027 +/- 0.005, 0.02 +/- 0.006 and 0.013 +/- 0.01 microM, respectively. The drug did not modify platelet cyclooxygenase activity as inhibition of thromboxane B2 (TXB2) formation was associated with a concomitant increased synthesis of prostaglandin D2 (PGD2), PGE2 and PGF2 alpha. ZD9583 had little effect on cultured human umbilical vein endothelial cell prostacyclin synthase giving an IC50 of 24.2 +/- 4.9 microM. In-vitro ZD9583 caused concentration-dependent inhibition of U46619-induced aggregation responses of platelets from man, rat and dog, yielding apparent log A2 values of 8.7 +/- 0.12, 8.8 +/- 0.2 and 9.3 +/- 0.2, respectively. The drug was selective; at concentrations up to 100 microM it did not affect 5-hydroxytryptamine or the primary phases of adenosine diphosphate and adrenaline-induced aggregation. ZD9583 (100 microM) did not, furthermore, modify the platelet inhibitory effects of PGD2, prostaglandin E1 (PGE1) and prostacyclin. Oral administration of ZD9583 (3-10 mg kg-1) to both rats and dogs caused dose-dependant inhibition of collagen-stimulated TXA2 production ex-vivo which persisted for up to 12 h. The drug also caused profound TXA2 receptor blockade in both species for in excess of 12-h after an oral dose of 3 mg kg-1. ZD9583 (3 mg kg-1, p.o.), when administered to dogs over a five-day period at 12 h intervals, did not cause either tachyphylaxis or an accumulation of effect. We conclude that ZD9583 is a potent, selective, orally active thromboxane synthase inhibitor and TXA2 receptor antagonist.

"Glycylcyclines". 3. 9-Aminodoxycyclinecarboxamides

A series of 9-(acylamino)doxycycline derivatives has been prepared. These analogs exhibit good activity against both tetracycline sensitive and tetracycline resistant Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria that are encoded with the efflux and ribosomal resistance gene factors. N,N-Dialkylglycylamido derivatives possessed the highest activity. Replacement of glycine moiety with other amino acids did not further enhance the activity.

Glycylcyclines. 1. A new generation of potent antibacterial agents through modification of 9-aminotetracyclines

This report describes the discovery of a new generation of tetracycline antibacterial agents, the "glycylcyclines". These agents are notable for their activity against a broad spectrum of tetracycline-susceptible and -resistant Gram-negative and Gram-positive aerobic and anaerobic bacteria possessing various classes of tetracycline-resistant determinants [tet B (efflux), tet M (ribosomal protection)]. The design and synthesis of a number of 7-substituted 9-substituted-amido 6-demethyl-6-deoxytetracyclines are described.

ZD1542, a potent thromboxane A2 synthase inhibitor and receptor antagonist in vitro

1. The thromboxane A2 synthase (TXS) inhibitory activity and the thromboxane A2 (TP)-receptor blocking action of ZD1542 (4(Z)-6-[2S,4S,5R)-2-[1-methyl-1-(2-nitro-4-tolyloxy)ethyl]-4-(3- pyridyl)-1,3-dioxan-5-yl]hex-4-enoic acid) has been evaluated in vitro on platelets and whole blood from a range of species including man. Antagonist activity has also been investigated in vascular and pulmonary smooth muscle preparations in vitro. 2. ZD1542 caused concentration-dependent inhibition of human platelet microsomal thromboxane B2 (TXB2) production in vitro (IC50 = 0.016 microM); this inhibition was associated with an increase in prostaglandin E2 (PGE2) and PGF2 alpha formation. 3. ZD1542 also inhibited collagen-stimulated TXS in human, rat and dog whole blood giving IC50 values of 0.018, 0.009 and 0.049 microM respectively. The drug did not modify platelet cyclo-oxygenase activity as inhibition of TXB2 formation was associated with a concomitant increase in the levels of PGD2, PGE2 and PGF2 alpha. ZD1542 had little if any effect against cultured human umbilical vein endothelial cell (HUVEC) cyclo-oxygenase (IC50 > 100 microM) and prostacyclin (PGI2) synthase (IC50 = 18.0 +/- 8.6 microM). 4. ZD1542 caused concentration-dependent inhibition of U46619-induced aggregation responses of human, rat and dog platelets yielding apparent pA2 values of 8.3, 8.5 and 9.1 respectively. The drug was selective as, at concentrations up to 100 microM, it did not modify 5-hydroxytryptamine (5-HT) or the primary phases of adenosine diphosphate (ADP) and adrenaline-induced aggregation. Furthermore, ZD1542 (100 microM) modified only weakly the platelet effects of PGD2, PGE1 and PGI2. 5. ZD1542 also caused concentration-dependent inhibition of U46619-mediated contractions of rat thoracic aorta, guinea-pig trachea and lung parenchyma preparations giving apparent pA2 values of 8.6,8.3 and 8.5 respectively. At concentrations approaching three orders of magnitude greater than those required to block U46619-mediated contractions, the drug did not affect the actions of non-prostanoid agonists or exhibit agonist activity in any of the smooth muscle preparations employed; neither did it interact at EP- or FP-receptors.6. In conclusion, the present study demonstrates that ZD1542 is a drug that exhibits both potent,selective TXS inhibition and TXA2 receptor antagonism.

In vitro and in vivo antibacterial activities of the glycylcyclines, a new class of semisynthetic tetracyclines

N,N-Dimethylglycylamido (DMG) derivatives of minocycline and 6-demethyl-6-deoxytetracycline are new semisynthetic tetracyclines referred to as the glycylcyclines. The in vitro activities of the glycylcyclines were evaluated in comparison with those of minocycline and tetracycline against strains carrying characterized tetracycline resistance determinants and against 995 recent clinical isolates obtained from geographically distinct medical centers in North America. The glycylcyclines were active against tetracycline-resistant strains carrying efflux [tet(A), tet(B), tet(C), and tet(D) in Escherichia coli and tet(K) in Staphylococcus aureus] and ribosomal protection [tet(M) in S. aureus, Enterococcus faecalis, and E. coli)] resistance determinants. Potent activity (MIC for 90% of strains, < or = 0.5 microgram/ml) was obtained with the glycylcyclines against methicillin-susceptible and methicillin-resistant S. aureus, E. faecalis, Enterococcus faecium, and various streptococcal species. The glycylcyclines exhibited good activity against a wide diversity of gram-negative aerobic and anaerobic bacteria, most of which were less susceptible to minocycline and tetracycline. The activities of the glycylcyclines against most organisms tested were comparable to each other. The in vivo efficacies of the glycylcyclines against acute lethal infections in mice when dosed intravenously were reflective of their in vitro activities. The glycylcyclines had efficacies comparable to that of minocycline against infections with methicillin-susceptible and methicillin-resistant S. aureus strains, a strain carrying tet(K), and a tetracycline-susceptible E. coli strain but exceeded the effectiveness of minocycline against infections with resistant isolates, including strains harboring tet(M) or tet(B). Levels of DMG-6-deoxytetracycline in serum were higher and more sustained than those of DMG-minocycline or minocycline. Our results show that the glycylcyclines have potent in vitro activities against a wide spectrum of gram-positive and gram-negative, aerobic and anaerobic bacteria, including many resistant strains. On the basis of their in vitro and in vivo activities, the glycylcyclines represent a significant advance to the tetracycline class of antibiotics and have good potential value for clinical efficacy.

Regioselective and enantioselective epoxidation catalyzed by metalloporphyrins

Recent progress in regioselective and enantioselective epoxidations catalyzed by metalloporphyrins is discussed here, with an explanation of the biomimetic antecedents of this area and its relevance to synthetic applications. Classification of the catalysts that have been studied allows useful conclusions to be drawn about the development of this field. In particular, both the most promising biomimetic and practical catalysts have arisen from systems that can be systematically modified by convenient synthetic methodology.

N-phosphoryl derivatives of bisantrene. Antitumor prodrugs with enhanced solubility and reduced potential for toxicity

The selective phosphorylation of bisantrene (1) affords bis(phosphonoguanidinic acid) 6, a prodrug with enhanced aqueous solubility (as sodium salt 7) at physiological pH. Unlike 1, in a rat tail vein model, no precipitation was observed when bis(phosphonoguanidinic acid) 6 was injected. While in rats 6 hydrolyzed to monophosphonoguanidinic acid 9 with a half-life of ca. 12 min., complete hydrolysis to bisantrene required several hours. The corresponding monophosphonoguanidinic acid 9 was synthesized from bisantrene and also showed good solubility and antitumor activity. While the antitumor activities of 6 in mice were comparable to bisantrene against B-16 melanoma and P-388 and L-1210 leukemias, it was inactive in vitro vs several tumor cell types. Thus, its activity in vivo resulted from its ability to serve as a prodrug for bisantrene.

Kinetic interactions of tazobactam with beta-lactamases from all major structural classes

Tazobactam was shown to be a potent inhibitor of group 1, 2a, 2b, and 2b' beta-lactamases. Extended kinetic studies with class A and C serine beta-lactamases showed that the PC1, TEM-2, and P99 enzymes all were reversibly inhibited prior to inactivation of the enzymes. The CcrA metallo-beta-lactamase was less well inhibited, with a 50% inhibitory concentration at least 3 orders of magnitude less favorable than those for most serine beta-lactamases. The numbers of hydrolytic turnovers of tazobactam before inactivation were 2 for PC1, 125 for TEM-2, 50 for P99, and 4,000 for the CcrA enzyme. In spectral studies, transient intermediates were formed after reaction of tazobactam with the PC1, TEM-2, and CcrA beta-lactamases, corresponding to enzyme-associated intermediates responsible for hydrolysis of tazobactam. Chromophores absorbing at 270 nm (CcrA) and 288 nm (TEM-2 and PC1) were observed for these reaction intermediates. The P99 cephalosporinase formed a stable complex with a UV maximum at 295 nm. Incubation of tazobactam with all of the enzymes resulted in accumulation of a tazobactam reaction product with a short-wavelength absorbance. This product has characteristics similar to those of the major eucaryotic metabolite of tazobactam. Possible reaction mechanisms are presented to explain the findings. In conclusion, both serine-based and metallo-beta-lactamases were irreversibly inactivated by tazobactam following an initial transient inhibition phase.

Structural studies on tazobactam

Tazobactam (3, C10H12N4O5S) is an effective inhibitor of bacterial beta-lactamases. It crystallizes with unit cell dimensions a = 10.230 (2) A, b = 14.396 (2) A, and c = 17.291 (2) A in space group P2(1)2(1)2(1). Compared to the related inhibitor sulbactam (2), which lacks the triazole ring, crystalline tazobactam exhibits very similar beta-lactam geometry and the same S(1) envelope conformation of the thiazolidine ring. However, in both independent molecules of 3 a triazole ring nitrogen atom accepts an intermolecular hydrogen bond; similar interaction by this moiety of 3 with a hydrogen-bond donor on the enzyme, which is impossible for 2, could account for its enhanced inhibitory power. Semiempirical molecular orbital calculations show pronounced negative potential there. Molecular mechanics supports the hypothesis that the carboxyl group can rotate freely and the triazole ring can "flip".

Pyrido[3,4-e]-1,2,4-triazines and related heterocycles as potential antifungal agents

The preparation and biological activities of a series of pyrido[3,4-e]-1,2,4-triazines, 1,2,4-triazino[5,6-c]quinolines, and related fused triazines are described. Methyl, amino, and acylamino substituents were placed in the pyridyl ring of the former system. Other structural modifications included various alkyl, cycloalkyl, substituted phenyl, and heterocyclic groups in the 3-position of these ring systems. In agar dilution assays, actives in this series inhibited strains of Candida, Aspergillus, Mucor, and Trychophyton species at MIC's of less than or equal to 16 micrograms/mL.

N-azamonobactams. 1. The synthesis of some 3-substituted N-azamonobactam derivatives

Ring closure of the N-(tert-butyloxycarbonyl)-L-serine 2-(diphenylmethylene)hydrazide (10a) and the corresponding L-threonine derivative (10b) gave good yields of the beta-lactams 11a and 11b. Catalytic hydrogenation afforded the corresponding N-amino beta-lactams 12a and 12b. These compounds were then further transformed into 3-(S)-[[(2-amino-4-thiazolyl)-(Z)-(methoxyimino)acetyl]amino-2-oxo-1- azetidinyl]sulfamic acid analogs 18, 23, and 30a and 30b. None of these compounds exhibited any interesting biological activity.

Antitumor agents. 2. Bisguanylhydrazones of anthracene-9,10-dicarboxaldehydes

9,10-Anthracenedicarboxaldehyde bis[(4,5-dihydro-1H-imidazol-2-yl)hydrazone] (bisantrene, VI-1) showed anticancer activity in mice vs. both leukemias and solid tumors. Increases in life span vs. the following neoplasms were: P-388 leukemia, 137%; B-16 melanoma, 122%; Lieberman plasma cell tumor, greater than 85%; colon tumor 26, 150%; Ridgway osteogenic sarcoma, 85%. There were significant numbers of long-term survivors. Both DNA and RNA synthesis were strongly inhibited. The drug was resistant to biodegradation and was bound strongly to tissues; in monkeys the half-life for disappearance from serum was 6 days. Related hydrazones were synthesized, and structure-activity relationships are discussed. Two routes to ring-substituted anthracene-9,10-dicarboxaldehyde intermediates were developed.

C NMR spectra of streptolydigin, tirandamycin, and related degradation products

Absorptions of the 32 carbon atoms of streptolydigin, a 3-acyltetramic acid, have been assigned in its C NMR spectrum, as have the adsorptions of triandamycin and related degradation products. Methods employed in assigning the individual carbons include off-resonance decoupling, and comparison studies with appropriate model compounds.

Heterogeneous Catalysis: Effect of an Alternating Electric Field

Oxidation of carbon monoxide was studcied in a static reactor at 123 degrees +/- 1 degrees C, wtith NiO as catalyst. An alternating electric field of about 22,000 volts per centimeter, peak to peak, was applied normal to the catalytic Surfaces. The rate of oxidation was thereby enhanced by a factor of 6 at 100 cycles per second, with maximum enhancement at between 100 and 200 cycles per second.