Analyses of cytochrome b mutations in Plasmodium falciparum isolates in Thai-Myanmar border

BACKGROUND: The combination of atovaquone and proguanil (Malarone) has been established as a drug of choice to prevent and treat multi-drug resistant Plasmodium (P.) falciparum malaria in travelers. However, several cases of resistance against Malarone have been reported in some parts of Africa, and many of the cases are believed to be associated with mutations at the codon 268 of cytochrome b gene in mitochondria of P. falciparum. The aim of the study was to estimate the effectiveness of Malarone in treatment and prophylaxis for the travelers to Thai-Myanmar border where multi-drug resistant malaria is highly endemic. METHODS: Seventy P. falciparum samples obtained from patients from Thai-Myanmar border were sequenced to detect mutations around the codon 268. The same samples were also sequenced to detect P. falciparum chloroquine resistance transporter mutation (PfCRT K76T). RESULTS: All the 70 samples showed no mutations at the codon 268 of cytochrome b gene. Whereas, 50 samples, whose pfcrt genes were sequenced successfully, had an identical genotype for K76T mutation. CONCLUSION: In Asian countries, even in the multi-drug resistant areas in the great Mekong region, no case of Malarone resistance has been reported clinically or genetically thus far. In this study, all the P. falciparum parasites tested successfully were shown to be chloroquine resistant but atovaquone susceptible genetically. The more the usefulness of Malarone increases for both treatment and prophylaxis, the wider the drug-resistance against Malarone may spread in the region. Although the total number of samples examined is not large, it is concluded from these findings that Malarone should be recommended for prophylaxis of malaria for travelers to the Mekong region.     

双氢青蒿素与咯萘啶伍用治疗抗性恶性疟的研究

目的　寻找更理想的治疗抗药性恶性疟的联合用药方案。　方法　双氢青蒿素、咯萘啶单用及伍用分别治疗24、25和32例恶性疟现症患者,分别于服药后第14、21及28天随访,以退热时间、原虫消失时间、复燃时间、复燃率、治愈率、配子体携带率、药物副作用发生率等为指标,以双氢青蒿素、咯萘啶标准疗法为对照,进行临床双盲试验,综合评估双氢青蒿素合并咯萘啶疗法。　结果　伍用组退热时间35.7±24.7h与咯萘啶单用组35.8±16.5h相似(P>0.05),显著快于双氢青蒿素单用组52.6±38.9h(P<0.01)。伍用组无性体原虫消失时间23.8±10.1h与双氢青蒿素单用组22.9±6.5h相似(P>0.05),显著快于咯萘啶单用组49.4±20.3h(P<0.01)。伍用组治后配子体出现率、持续时间及密度分别为20.0%、5.7d和4个/μl血,与双氢青蒿素单用组16.7%、3.5d和3个/μl血相似(P>0.05),明显好于咯萘啶单用组60.9%、11.5d和12个/μl血(P<0.01)。3种方案均无明显药物副反应。　结论　双氢青蒿素与咯萘啶伍用保持了两药的优点,克服了两药的不足,是目前治疗抗性恶性疟较为理想的药物组合     

Drug resistant malaria, with special reference to Thailand.

Drug resistance of malaria parasites is a major problem confronting efforts to treat and control malaria. Starting with chloroquine, the emergence of resistance to other drugs has led to multi-drug resistance patterns that pose increasing threats for the future. This report reviews work carried out over the past decades at the Hospital for Tropical Diseases, Bangkok, which monitors patients from many areas, including the Thai-Cambodian border, which harbors the world's most severe multi-drug resistant Plasmodium falciparum.     

多黏菌素的药理作用和治疗多重耐药鲍曼不动杆菌的研究进展

随着全球多重耐药鲍曼不动杆菌的感染率、致死率日益增多,且对碳青霉烯类耐药现象十分常见,多黏菌素作为治疗多重耐药鲍曼不动杆菌的最后防线被引入临床.本文旨在对多黏菌素的化学结构、作用机制、耐药机制、单用及联合应用和毒性作用进行综述,以期对临床科学合理用药和进一步研究提供参考.     

Evolution of multi-drug resistant hepatitis B virus during sequential therapy

Multi-drug resistant hepatitis B virus (HBV) has been reported in hepatitis B patients who received sequential antiviral therapy. In vitro studies showed that HBV constructs with mutations resistant to lamivudine and adefovir have marked reduction in sensitivity to combination of lamivudine and adefovir, whereas constructs with mutations resistant to either drug remain sensitive to the other drug. We conducted this study to determine whether mutations conferring resistance to multiple antiviral agents co-locate on the same HBV genome in vivo and to describe the evolution of these mutations. Sera from six patients who had been found to have multi-drug resistant HBV mutations to lamivudine+adefovir, lamivudine+hepatitis B immunoglobulin (HBIG), or lamivudine+entecavir on direct sequencing were cloned after nested polymerase chain reaction (PCR). Analysis of 215 clones from 11 samples with multi-drug resistant mutations on direct sequencing showed that 183 (85%) clones had mutations to both therapies on the same genome; 31 clones had lamivudine-resistant mutants only. Clonal analysis of serial samples from three patients showed progressive evolution from all clones with lamivudine-resistant HBV mutations only to mixtures of clones that have multi-drug resistant mutations and clones that have lamivudine-resistant HBV mutations only, and ultimately all clones having multi-drug resistant HBV mutations. In conclusion, mutations conferring resistance to multiple antiviral agents co-locate on the same viral genome, suggesting that combination therapy directed against mutants resistant to each treatment may not be adequate in suppressing multi-drug resistant HBV. De novo combination therapy may prevent the emergence of multi-drug resistant mutants.     

青蒿素类药物与其他药物配伍治疗疟疾的研究进展

近年来抗疟药耐药现象的出现严重影响了疟疾的防治,新药的研发和疟疾疫苗的研究离临床应用还存在一定距离,联合用药是疟疾治疗的有效途径,已成为当今疟疾防治研究的热点。本文综述了青蒿素类药物与其他药物联合治疗疟疾的研究进展。     

Recent advances in the medical and surgical treatment of multi-drug resistant tuberculosis

PURPOSE OF REVIEW: Multi-drug resistant tuberculosis is a serious clinical problem. Extension of drug resistance to second-line anti-tuberculosis drugs in the form of the W-strain is cause for alarm. There is an urgent need for more rapid recognition of multi-drug resistant tuberculosis and newer therapeutic agents. This review summarizes the recent advances in the diagnosis and treatment of multi-drug resistant tuberculosis including surgery and new developments. RECENT FINDINGS: Multidrug resistant tuberculosis therapy is characterized by prolonged treatment, high morbidity and mortality, and high relapse rates. New diagnostic procedures that include electrophoretic and molecular hybridization techniques will allow rapid diagnosis. Several new drugs are currently in various phases of development. Moxifloxacin, a respiratory fluoroquinolone, is currently in phase III clinical development. New classes of drugs such as nitroimidazopyrans (PA-824) and diarylquinolines (R-207910) are exciting based on phase I and II data. Immunomodulation with vaccines and interferon-gamma have been unhelpful. Surgery is reserved for selected cases only. Cure rates of over 90% with reasonable morbidity and mortality has been achieved with meticulous preoperative preparation, patient selection and careful surgical technique. SUMMARY: Newer drugs and defined indications for surgery should provide improved cure rates, with reduced duration of treatment for multi-drug resistant tuberculosis.     

Artemisinin-based combinations

PURPOSE OF REVIEW: Artemisinin-based combination treatments have been the mainstay of treatment for falciparum malaria in Southeast Asia for more than 10 years and are now increasingly recommended as first-line treatment throughout the rest of the world. RECENT FINDINGS: A large multicentre randomised trial conducted in East Asia has shown a 35% reduction in mortality from severe malaria following treatment with parenteral artesunate compared with quinine. There is increasing evidence that artemisinin-based combination treatments are safe and rapidly effective. Artemether-lumefantrine (six doses) has been shown to be very effective in large trials reported from Uganda and Tanzania. A once daily three-dose treatment of dihydroartemisinin piperaquine, a newer fixed combination, was a highly efficacious and well tolerated treatment for multi-drug resistant falciparum malaria in Southeast Asia. SUMMARY: Early diagnosis and treatment of uncomplicated malaria with effective drugs remains a priority as part of a comprehensive malaria control strategy. Artemisinin-based combination treatments have consistently been shown to be highly effective and safe. The challenge is to make them accessible in tropical countries.     

Amodiaquine resistance is not related to rare findings of pfmdr1 gene amplifications in Kenya

OBJECTIVES: Many countries are now adopting artemisinin-based combination therapy (ACT) for treatment of Plasmodium falciparum malaria. In multi-drug resistant areas in South East Asia amplifications of the pfmdr1 gene are frequent and tentatively associated with reduced susceptibility to the common quinoline partner drugs mefloquine and lumefantrine. In Africa where amodiaquine is one of the favoured quinoline partner drugs in ACT, studies on multi-drug resistance associated pfmdr1 gene amplifications are urgent. Our aim was to determine the current prevalence of pfmdr1 gene amplifications and a possible association between pfmdr1 gene copy number and amodiaquine treatment outcome in Kenya. METHODS: Seventy-two children with Plasmodium falciparum infection in Kenya were treated with amodiaquine monotherapy and followed for 21 days. Possible amplification of the pfmdr1 gene was assessed from blood-spotted filterpaper by TaqMan probe based real-time polymerase chain reaction. RESULTS: The recrudescent rate was 14 of 72 (19%). All children had single pfmdr1 copy infections, with the exception of one child who had an infection with two pfmdr1 copies. This child had an adequate treatment response. CONCLUSION: Pfmdr1 amplifications do exist in Kenya but at a very low frequency. Yet, the substantial number of children with recrudescent infections implies that amodiaquine resistance is not related to pfmdr1 gene amplifications in Kenya.     

Case of pulmonary multi-drug resistant tuberculosis with left destroyed lung, treated with pneumonectomy

A 31-year-old woman complained of cough and fever for 2 months. She was admitted to a hospital and was diagnosed as pulmonary tuberculosis. She received combination therapy with isoniazid, rifampicin, ethambutol, and pyrazinamide. As the drug susceptibility test revealed that the isolated strain was multi-drug resistant, the regimen was changed to pyrazinamide, ethionamide, cycloserine, enviomycin, and levofloxacin. The chemotherapy was not effective, so she received pneumonectomy for left destroyed lung. After surgical treatment, her sputa converted to negative for tubercle bacilli. Surgical treatment such as pneumonectomy is considered to be useful in a case of multi-drug resistant pulmonary tuberculosis.     

21例耐多药脊柱结核手术联合个体化化疗的临床分析

目的 回顾性分析手术联合药敏试验指导下的个体化抗结核化疗对耐多药脊柱结核的临床疗效。 方法 收集2006年2月至2010年6月解放军第三○九医院全军骨科中心收治、且符合纳入标准的21例耐多药脊柱结核。包括初治结核6例,复治结核15例。21例患者入院后根据病灶特点接受不同方式手术治疗,术后参照既往抗结核化疗史及药敏试验结果,制定个体化化疗方案并定期随访。分析其临床特征与耐药表型,回顾术后1、3、6个月及之后每6个月随访时的临床表现,X线片、CT及三维重建、MRI等影像学变化及实验室指标,评价植骨融合情况及疾病转归。 结果 复治结核既往化疗平均持续（19.3±15.8）个月(7～49个月)。19例接受了开放手术治疗,其中1例于术后5个月内固定失效,有4例术后局部复发;2例接受的是CT引导下置管灌洗术。术后个体化化疗平均持续18.3(18～20)个月,末次随访时11例术前伴神经功能障碍者均有不同程度改善,9例伴后凸畸形者术后均得到良好矫正,但其中1例伴后凸畸形者因术后内固定失效,末次随访时后凸矫正明显丢失。18例最终临床治愈,3例仍在接受化疗。 结论 基于药敏试验的化疗联合手术的个体化治疗方案有利于尽早治愈耐多药脊柱结核,解决严重并发症,并避免耐多药菌株的播散及获得性耐药的产生。     

Successful combination therapy by meropenem and colistin for multi-drug-resistant Pseudomonas aeruginosa infection after allogeneic bone marrow transplantation

A 66-year-old male with acute type adult T-cell leukemia that was refractory to chemotherapy underwent unrelated allogeneic bone marrow transplantation after non-myeloablative conditioning with fludarabine, busulfan and total body irradiation. During an episode of neutropenia on day 12 after transplantation, pneumonia and sepsis due to multi-drug resistant Pseudomonas aeruginosa developed. Drug susceptibility tests demonstrated resistance to all kinds of intravenous antibiotics available for P. aeruginosa in Japan. Multi-drug susceptibility tests by the breakpoint-checkerboard plate method were then performed and combination therapy with meropenem hydrate and colistin was started based on the test results. After starting treatment, clinical symptoms and laboratory data immediately improved and engraftment of neutrophils was achieved on day 18. Infections with multi-drug-resistant P. aeruginosa are often critical for patients after hematopoietic stem cell transplantation and are difficult to control. In this paper, we report a case of severe multi-drug-resistant P. aeruginosa infection that was successfully treated by combination therapy selected using the breakpoint-checkerboard plate method.     

耐药结核病的研究进展

耐药结核病是当今世界非常严峻的公共卫生问题,它直接影响着全球结核病疫情的控制。除我们常见的耐多药结核病外,近年来耐药结核病的定义和类型也在不断变化并增加,如超广泛耐药、全耐药等。耐药结核病的诊断主要通过常规的细菌学和核酸检测方法在实验室中确定。部分药物敏感的病例由于对抗结核药物不能耐受而使治疗方案受限,表现为与耐药结核病相同的治疗结果,可称之为"临床耐药结核病"。对耐药结核病的预防主要寄望于现有抗结核药物的个性化使用,用足核心药物异烟肼和利福平是关键。抗结核新药的出现有助于我们控制耐多药结核病,但现阶段仍要注意实施综合疗法,加大病灶局部的抗结核药物浓度,立足于现有药物,个性化治疗耐多药结核病才是正确的道路。     

Drug resistance in malaria

Ever since the discovery of the first case of chloroquine resistance along the Thai-Combodian border in the late 1950s, Southeast Asia has played an important role as a focus for the development of drug resistance in Plasmodium falciparum. Although the first case of quinine resistance had been reported much earlier from South America, the onset of chloroquine resistance marked the beginning of a new chapter in the history of malaria in Southeast Asia and by 1973 chloroquine finally had to be replaced by the combination of sulphadoxine and pyrimethamine (SP) as first line drug for the treatment of uncomplicated malaria in Thailand and more than 10 African countries have also switched their first line drug to SP. In 1985, eventually SP was replaced by mefloquine. The rapid development of resistance to this new drug leads to the introduction of artemisinin as a combination drug in the mid-1990s. It is mandatory to mention here that therapeutic regimens for prevention and treatment of chloroquine-resistant P. falciparum are associated with higher costs and side-effects compared to chloroquine. Additionally, some of these alternative treatments are associated with more side-effects, take longer time for cure and are more difficult to comply with than chloroquine. Urgent efforts are needed to identify effective, affordable, alternative antimalarial regimens. Molecular markers for antimalarial resistance have been identified, including pfmdr-1 and pfcrt polymorphisms associated with chloroquine resistance and dhfr and dhps polymorphisms associated with SP resistance. Polymorphisms in pfmdr-1 may also be associated with resistance to chloroquine, mefloquine and artemisinin. Use of such genetic information for the early detection of resistance foci and future monitoring of drug resistant malaria is a potentially useful epidemiological tool, in conjunction with the conventional in vitro and in vivo drug sensitivity assessments. The purpose of this review is to describe the state of knowledge regarding drug resistant malaria and to outline the changing patterns of drug resistance including its determinants, current status in diverse geographical areas, molecular markers and their implications to limit the advent, spread and intensification of drug resistant malaria.     

Amikacin and colistin for treatment of Acinetobacter baumannii meningitis

We report a case of a 52-year-old man with post-surgical meningitis due to a multi-drug resistant Acinetobacter baumannii. Despite therapy with intravenous amikacin and imipenem the meningitis progressed. Upon institution of combination therapy with amikacin by the intravenous and intrathecal (IT) routes, and intravenous colistin the patient experienced successful clinical and microbiological outcomes.     

Multi-drug resistant Plasmodium falciparum malaria in Assam, India: timing of recurrence and anti-malarial drug concentrations in whole blood

The susceptibility of 23 cases of Plasmodium falciparum malaria from the Sonapur primary health center in the Kamrup district of Assam, India to different antimalarials was investigated using the 28-day World Health Organization in vivo test. Whole blood concentrations of chloroquine, sulfadoxine, and quinine were determined at different intervals and at the time of parasites recrudescence after completion of treatment with the respective drugs to confirm the status of drug sensitivity. A case of multi-drug resistant P. falciparum malaria was found where recrudescence occurred, despite standard oral treatment with chloroquine, sulfadoxine/pyrimethamine, and quinine sequentially. Whole blood concentrations of chloroquine, sulfadoxine, and quinine at the time of recrudescence were 0.35 microg/ml (day 7), 18 microg/ml (day 14), and 0.009 microg/ml (day 14), respectively. Therefore, monitoring of drug-resistant P. falciparum malaria and its proper treatment should be intensified to check the spread of multi-drug resistant strains in other parts of the country.     

Carbapenem-resistant enterobacteriaceae: an emerging problem in children

Antibiotic resistance among gram-negative bacteria has reached critical levels. The rise of carbapenem resistance in Enterobacteriaceae carrying additional resistance genes to multiple antibiotic classes has created a generation of organisms nearly resistant to all available therapy. Carbapenem-resistant Enterobacteriaceae (CRE) infections are known to be associated with significant morbidity and mortality, and these pathogens have now made their way to the most vulnerable populations, including children. This review provides a brief overview of CRE, with a focus on CRE infections in children, and highlights available data on the epidemiology, clinical characteristics, carbapenemase types, risk factors, treatment, and outcomes of these multi-drug resistant infections in the pediatric population.     

Atovaquone-proguanil: report from the CDC expert meeting on malaria chemoprophylaxis (II)

The fixed dose combination of atovaquone and proguanil hydrochloride, marketed under the trade name Malarone, is the most recently approved agent in North America for the prevention and treatment of chloroquine- and multi-drug resistant Plasmodium falciparum malaria. In both adult and pediatric populations, atovaquone-proguanil demonstrates consistently high protective efficacy against P. falciparum, and in treatment trials, cure rates exceed 93%. Only a handful of genetically confirmed treatment failures have been reported to date. Atovaquone-proguanil has an excellent safety profile during both prophylaxis and treatment courses, with severe adverse events rarely reported. This topical review will examine the evidence behind the current indications for use of atovaquone-proguanil, and will summarize the current body of literature surrounding safety and tolerability.     

Ideal treatment of malaria attack: more questions than answers? Experience of a department of infectious diseases

The number of cases of malaria imported to western Europe from tropical areas is steadily growing, due to the increased number of people traveling to endemic regions and to the spread of Plasmodium strains resistant to chemoprophylaxis. This has prompted the WHO to frequently update its guidelines concerning preventive therapy. We report on 143 consecutive cases of benign attacks of malaria in patients returning primarily from western and central Africa. Plasmodium falciparum was responsible for 80% of the cases. Forty-one percent of the patients had followed their preventive regimen correctly; mefloquine failed in 3 of them. Three early relapses were observed after curative treatment, including 2 patients who had received intravenous quinine for more than 5 days. Because P. falciparum infection is potentially lethal, we suggest that the treatment of malaria attacks be optimized, by systematically dosing serum quinine levels, in order to adjust the administered doses, and, as a first-line therapy, by prescribing a combination of drugs to patients at high risk of resistance.     

Benefits of using multiple first-line therapies against malaria

Despite the availability of many drugs and therapies to treat malaria, many countries' national policies recommend using a single first-line therapy for most clinical malaria cases. To assess whether this is the best strategy for the population as a whole, we designed an evolutionary-epidemiological modeling framework for malaria and compared the benefits of different treatment strategies in the context of resistance evolution. Our results show that the population-wide use of multiple first-line therapies (MFT) against malaria yields a better clinical outcome than using a single therapy or a cycling strategy where therapies are rotated, either on a fixed cycling schedule or when resistance levels or treatment failure become too high. MFT strategies also delay the emergence and slow the fixation of resistant strains (phenotypes), and they allow a larger fraction of the population to be treated without trading off future treatment of cases that may be untreatable because of high resistance levels. Earlier papers have noted that cycling strategies have the disadvantage of creating a less temporally variable environment than MFT strategies, making resistance evolution easier for the parasite. Here, we illustrate a second feature of parasite ecology that impairs the performance of cycling policies, namely, that cycling policies degrade the mean fitness of the parasite population more quickly than MFT policies, making it easier for new resistant types to invade and spread. The clinical benefits of using multiple first-line therapies against malaria suggest that MFT policies should play a key role in malaria elimination and control programs.