一株沃氏葡萄球菌耐药基因的研究

目的：研究沃氏葡萄球菌多重耐药情况和相关机制。方法：采用聚合酶链反应（PCR）法对一株多重耐药沃氏葡萄球菌进行β-内酰胺酶基因、氨基糖苷类修饰酶基因、大环内酯-林可酰胺-链阳菌素B类（MLSB）基因、四环素类基因、糖肽类基因、消毒剂基因检测。结果：PCR结果显示该株的mecA,TEM,ermA,ermC,msrA,msrB,aac（6′）/aph（2″）,qacA基因均为阳性,ant（4′,4″）,aph（3′）-,TetM,vanA,vanB基因均为阴性。结论：该株沃氏葡萄球菌存在多重耐药基因,而且对胺类、胍类消毒剂耐受。     

Hypersensitivity to inhaled TOBI following reaction to gentamicin

Cystic fibrosis (CF) is the most common autosomal-recessive disease in Caucasians. Colonization with Pseudomonas aeruginosa (P. aeruginosa) of the CF airways causes deterioration of pulmonary status. TOBI (Tobramycin solution for inhalation) is an inhaled antibiotic that can improve the pulmonary disease. We report on a 9-year old boy with CF who developed a rash following a course of IV gentamicin. The rash resolved after its discontinuation. However, the rash returned all over his body, with the start of inhalation of TOBI therapy. We desensitized the patient using escalating doses of inhaled TOBI. He tolerated the procedure well, and continues to be on TOBI 9 months after desensitization on a once-a-day regimen.     

下呼吸道感染患者铜绿假单胞菌分离株氨基糖苷类耐药相关基因分析

目的探讨分离自下呼吸道感染患者的氨基糖苷类耐药铜绿假单胞菌的耐药机制。方法从下呼吸道感染患者痰液中分离出52株对氨基糖苷类耐药的铜绿假单胞菌,PCR法检测6种氨基糖苷类修饰酶(AMEs)基因,并检测其中泛耐药菌的6种16S rRNA甲基化酶基因(以下简称甲基化酶基因)。对阳性产物测序加以证实。结果 52株铜绿假单胞菌中检出4种AMEs基因[aac(3)-Ⅱ、aac(6’)-Ⅰb、aac(6’)-Ⅱ和ant(2″)-Ⅰ],AMEs基因总检出率为92.3%。泛耐药菌中检出1种甲基化酶基因(rmtB)。16株高水平泛耐药菌中rmtB基因的检出率为81.3%。结论分离自下呼吸道感染患者的氨基糖苷类耐药铜绿假单胞菌中AMEs基因携带率高,其对氨基糖苷类耐药与aac(3)-Ⅱ、aac(6’)-Ⅰb、aac(6’)-Ⅱ和ant(2″)-Ⅰ有关;对氨基糖苷类高水平泛耐药主要与甲基化酶基因rmtB有关。     

Trafficking of Systemic Fluorescent Gentamicin into the Cochlea and Hair Cells

Aminoglycosides enter inner ear hair cells across their apical membranes via endocytosis, or through the mechanoelectrical transduction channels in vitro, suggesting that these drugs enter cochlear hair cells from endolymph to exert their cytotoxic effect. We used zebrafish to determine if fluorescently tagged gentamicin (GTTR) also enters hair cells via apically located calcium-sensitive cation channels and the cytotoxicity of GTTR to hair cells. We then examined the serum kinetics of GTTR following systemic injection in mice and which murine cochlear sites preferentially loaded with systemically administered GTTR over time by confocal microscopy. GTTR is taken up by, and is toxic to, wild-type zebrafish neuromast hair cells. Neuromast hair cell uptake of GTTR is attenuated by high concentrations of extracellular calcium or unconjugated gentamicin and is blocked in mariner mutant zebrafish, suggestive of entry via the apical mechanotransduction channel. In murine cochleae, GTTR is preferentially taken up by the stria vascularis compared to the spiral ligament, peaking 3 h after intra-peritoneal injection, following GTTR kinetics in serum. Strial marginal cells display greater intensity of GTTR fluorescence compared to intermediate and basal cells. Immunofluorescent detection of gentamicin in the cochlea also revealed widespread cellular labeling throughout the cochlea, with preferential labeling of marginal cells. Only GTTR fluorescence displayed increasing cytoplasmic intensity with increasing concentration, unlike the cytoplasmic intensity of fluorescence from immunolabeled gentamicin. These data suggest that systemically administered aminoglycosides are trafficked from strial capillaries into marginal cells and clear into endolymph. If so, this will facilitate electrophoretically driven aminoglycoside entry into hair cells from endolymph. Trans-strial trafficking of aminoglycosides from strial capillaries to marginal cells will be dependent on as-yet-unidentified mechanisms that convey these drugs across the intra-strial electrical barrier and into marginal cells.     

New aminoglycoside antibiotics

Importance of the field: Nosocomial infections caused by multi-drug resistant (MDR) Gram-negative bacteria are on the increase, often with few or no therapeutic options for treatment. Historically, a successful approach to generate novel antibiotics has been the chemical modification of existing classes, addressing deficiencies such as resistance mechanisms, safety profile or pharmacokinetic parameters. Aminoglycosides (AGs) represent one of the five clinically-used classes (AGs, β-lactams, quinolones, tetracyclines and sulfonamides) with activity against Gram-negative bacteria.

Areas covered in this review: A summary of the AG patent literature between the beginning of 2005 and February 2010 with the main focus on novel AG analogs with potential for therapeutic activity against MDR Gram-negative pathogens.

What the reader will gain: Overview of the patent literature in the aminoglycoside field during the past 5 years including an assessment of the therapeutic potential for the derivatives described.

Take home message: A few companies and academic groups have recently reawakened the dormant field of AG antibiotics, successfully applying novel technologies. So far, this has yielded one clinical candidate, ACHN-490, currently undergoing a Phase II evaluation in complicated urinary tract infections.     

发现大肠埃希菌喹诺酮耐药株gyrA基因新亚型和aac（6′）-Ⅰ b-Cr、mdfA基因

目的 了解大肠埃希菌(E.coli)对常用抗菌药物的耐药性及喹诺酮类DNA旋转酶基因、多药外排基因及氨基糖苷类修饰酶基因（AMEs）的存在情况。 方法 收集2006年1月~2008年10月本院临床标本分离的E.coli 60株,用K-B法检测细菌对16种抗菌药物的敏感性,用PCR及测序技术分析6种喹诺酮类基因(gyrA、qnrA、qnrB、qnrS、qepA、mdfA)和1种AMEs基因aac(6′)-Ⅰ b。 结果 60株菌对环丙沙星和左氧氟沙星的耐药率均为78.4%（47/60）;55株菌存在gyrA基因突变,其中3株菌gyrA与美国NCBI中已登录的gyrA基因序列不同,为新亚型;mdfA基因均阳性;对9株aac(6′)-Ⅰ b基因PCR阳性产物进行测序,证实5株携带aac（6′）-Ⅰ b-Cr双功能酶基因。 结论 gyrA基因突变是E.coli对喹诺酮类药物最主要的耐药机制,耐喹诺酮类药物的E.coli株中发现aac（6′）-Ⅰ b-Cr基因和gyrA新亚型,E.coli检出mdfA基因为中国大陆地区首次报道。     

A meta-analysis of the target trough concentration of gentamicin and amikacin for reducing the risk of nephrotoxicity

IntroductionAntimicrobial resistance is one of the biggest threats to public health systems worldwide, and aminoglycosides are key drugs for treating drug-resistant infections. Because of the nephrotoxicity of aminoglycosides, therapeutic drug monitoring is recommended, but few studies of the target trough concentration (Cmin) have been reported. To address the problem, we performed a meta-analysis to confirm the target Cmin of aminoglycosides for minimizing the risk of nephrotoxicity.MethodsWe conducted a literature search using MEDLINE, the Cochrane Library, and Ichushi-Web. In the meta-analysis, nephrotoxicity was compared between the Cmin ≥2 mg/L and Cmin <2 mg/L groups for gentamicin and between the Cmin ≥10 mg/L and Cmin <10 mg/L groups for amikacin.ResultsNo randomized controlled trials were reported for any of the drugs. Five observational studies involving 615 patients were reported for gentamicin, and two observational studies involving 159 patients were identified for amikacin. For gentamicin, Cmin <2 mg/L was linked to a significantly lower rate of nephrotoxicity than Cmin ≥2 mg/L (odds ratio [OR] = 0.22, 95% confidence interval [CI] = 0.12–0.40). For amikacin, Cmin <10 mg/L was associated with a significantly lower rate of nephrotoxicity than Cmin ≥10 mg/L (OR = 0.05, 95% CI = 0.01–0.21).ConclusionsAlthough further well-controlled studies with a low risk of bias are needed, the current meta-analysis demonstrated that Cmin <2 mg/L and Cmin <10 mg/L may reduce the risk of nephrotoxicity linked to gentamicin and amikacin, respectively.     

Aminoglycoside usage and monitoring in a Saudi Arabian teaching hospital: a ten-year laboratory audit

BACKGROUND AND OBJECTIVE: In 1989, a therapeutic drug monitoring service was established in Assir Central Hospital, Abha, Saudi Arabia, by the Department of Clinical Pharmacology and Therapeutics of the College of Medicine, King Saud University Abha Branch (now King Khalid University). We report a 10-year follow-up of the results of monitoring the commonly used aminoglycosides (amikacin, gentamycin and tobramycin) obtained from our adult patients on first monitoring. METHOD: Two educational seminars for doctors and nurses were conducted 6 months before the initiation of this study. Drug assay requests were made on specially designed forms. Drug dosages were determined by the attending physicians. Samples for peak and trough drug level determinations were drawn after the fourth dose. The results of first time monitoring were sent to the wards with appropriate comments for dosage modifications where indicated. RESULTS: The results for 2022 patients were analysed. Of these, 929, 899 and 194 were for amikacin, gentamycin and tobramycin, respectively. Therapeutic trough concentrations were 71.2%, 28.3% and 28.3% of patients on amikacin, gentamycin and tobramycin, respectively. A total of 8.8%, 17.6% and 11.9% had trough concentrations considered toxic for amikacin, gentamycin and tobramycin, respectively. Peak therapeutic concentrations were achieved in 31.6%, 42.3% and 39.7% of patients on amikacin, gentamycin and tobramycin. A total of 53.3% of patients on amikacin, 50.3% on gentamycin and 57.2% on tobramycin had peak serum drug concentrations in the subtherapeutic range. Toxic concentrations were noticed mainly in patients aged over 60 years and in the critically ill in the intensive care, coronary care and bums units of the hospital. CONCLUSION: To be cost-effective, intensive therapeutic monitoring of aminoglycosides in adults should continue to be monitored mainly for the old and sick patients in critical care units to optimize patient management.     

Intravenous aminoglycoside usage and monitoring of patients with cystic fibrosis in Australia. What's new?

Background: The aim of this study was to determine the current situation regarding aminoglycoside use and monitoring in patients with cystic fibrosis (CF) throughout Australia.
Methods: A questionnaire was sent out to all CF units. Information gathered included patient characteristics, aminoglycoside use, dosing, therapeutic drug-monitoring methods, toxicity monitoring and incidence of occurrence.
Results: Responses were obtained from 27 of the 28 units identified. Tobramycin was the aminoglycoside of choice. All but three centres were using once-daily dosing for aminoglycoside administration. Initial dosing in tobramycin-naïve patients was based on bodyweight (range 7–12 mg/kg). Patients being readmitted were mainly prescribed the dose that they had received on their previous admission. All units gave i.v. doses by infusion with five units using bolus dosing as well. The method of therapeutic drug monitoring varied greatly. A computer programme was used by 15 units. Toxicity monitoring usually coincided with therapeutic drug monitoring. Nephrotoxicity was reported as having occurred in 13 units and ototoxicity in 15 units. The highest incidence of toxicity was ototoxicity in 20% of patients in one CF unit.
Conclusion: Aminoglycoside dosing regimens have changed since the last survey was carried out in 1999. There has been an increase in the use of once-daily dosing from 54 to 88% of units. The reporting of both ototoxicity and renal toxicity has also increased (from 27 to 75% and from 19 to 65%, respectively). Standardization of management protocols for antibiotic use and patient monitoring may help reduce the risk of cumulative toxicity to aminoglycosides in CF patients.