Mueller–Hinton agar is superior to PDM blood agar for detection of methicillin-resistant Staphylococcus aureus

The aim of this study was to compare the expression of oxacillin resistance in methicillin-resistant Staphylococcus aureus (MRSA) on Paper Disc Method agar supplemented with 5% defibrinated blood (PDM blood agar) and Mueller–Hinton agar supplemented with 2% NaCl (MH NaCl agar) using different susceptibility tests. Fifty mecA- containing isolates of S. aureus, exhibiting 46 different pulsed-field gel electrophoresis patterns, were comparatively tested using the E test, the single disk diffusion test, and the multipoint inoculation technique, under various culture conditions. The E test incubated at 35 °C for 24 h (breakpoint of resistance ≥2.0 mg/L) detected 94% of the isolates on MH NaCl agar, compared with 28% for PDM blood agar ( P  < 0.05). The disk diffusion test (breakpoint ≤ 10 mm in diameter) under these incubation conditions detected resistance in 100% of the isolates on MH NaCl agar and in 80% of the isolates on PDM blood agar ( P  < 0.05). The multipoint technique (breakpoint ≥1 mg/L), applied at 35 °C for 24 h, detected 100% on MH NaCl agar and 46% on PDM blood agar ( P  < 0.05). Irrespective of the method of susceptibility testing evaluated, MH NaCl agar was superior to PDM blood agar for the detection of oxacillin resistance in mecA -containing S. aureus .     

不同温度诱导细菌L型的实验观察

目的：观察不同温度诱导细菌形成Ｌ型。方法：抗生素纸片诱导。以苯唑青霉素（每片４０μｇ）、羧苄青霉素（每片５００μｇ）在３７℃、３２℃及２８℃分别诱导金黄色葡萄球菌和福氏痢疾杆菌Ｌ型。结果：三种不同温度诱导细菌形成Ｌ型,其菌落特征、形态及染色性等均无差别。结论：抗生素诱导Ｌ型除３７℃外,３２℃和２８℃均可形成。为探讨Ｌ型可在自然界产生和存在是否与某些传染病流行和传播有关提供依据。     

Changing Pattern of Relapse in Osteosarcoma of the Extremities Treated with Adjuvant and Neoadjuvant Chemotherapy

Abstract

In 551 patients with osteosarcoma of the extremities treated between 1980 and 1991 in our Institution with surgery only (35 cases), surgery combined with adjuvant chemotherapy (147 cases) or neoadjuvant chemotherapy (369 cases) the relapse patterns were analyzed. Adjuvant chemotherapy was performed according to 2 different protocols and neoadjuvant chemotherapy according to 3 different protocols successively activated.

In the 252 patients who relapsed, the interval between initial treatment and first relapse was significantly longer in the group treated with adjuvant and neoadjuvant chemotherapy (18.1 and 21.3 mo) than in the group treated with surgery only (5.4 mo). For patients treated with neoadjuvant chemotherapy, a longer interval was seen in the most effective regimen of neoadjuvant chemotherapy (25 mo). No significant differences were seen among the 3 groups, according to the site of first metastasis, although in patients treated with the most effective neoadjuvant regimen there was a higher incidence of bone metastasis.

In patients who relapsed with pulmonary metastases the average number of nodules seen by standard X-rays, as well as CT scans, was significantly higher in patients treated with surgery only (3.6) than in patients treated with adjuvant or neoadjuvant chemotherapy (2.5 and 2.6 nodules).

We conclude that these changes in metastatic pattern in patients treated with adjuvant and neoadjuvant chemotherapy are important, because they may encourage the use of salvage therapy with thoracotomy in a larger number of patients.

Prolongation of time relapsed after more effective regimens of adjuvant and neoadjuvant chemotherapy should be considered when evaluating the preliminary results of new chemotherapy protocols.     

气相色谱法研究赋形剂对苯唑青霉素钠稳定性的影响

采用程序裂解-气相色谱(GC)检测系统,配合红外光谱等手段,研究常用赋形剂如硬脂酸、硬脂酸镁、淀粉、滑石粉和碳酸钙等对苯唑青霉素钠和氨苄青霉素稳定性的影响。实验结果表明,硬脂酸和苯唑青霉素钠有固相反应发生,不宜作苯唑青霉素钠固体制剂的赋形剂,其它赋形剂在相同条件下无此现象。这与差热分析的结果一致。     

Antimicrobial activity of ozenoxacin and other antimicrobials against Staphylococcus aureus strains isolated from clinical skin specimens in Japan in 2019 and 2020

Skin infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and the spread of antimicrobial resistance are a major problem in Japan. Here, we investigated the susceptibility of S. aureus clinical isolates to ozenoxacin (OZNX), a topical antimicrobial approved for superficial skin infection treatment in Japan. Susceptibility to OZNX was measured in 110 skin-derived methicillin-susceptible S. aureus (MSSA) and 130 MRSA strains isolated in 2019 and 2020 in Japan. The broth microdilution method was performed, and results were analyzed according to the Clinical and Laboratory Standard Institute (M07 and M100) guidelines. The results were compared with those of other antimicrobials used against S. aureus. The minimum inhibitory concentrations (MIC)₉₀ of OZNX for MSSA and MRSA were 0.12 and 0.25 μg/mL, respectively, indicating that OZNX exhibited the same or stronger antibacterial activity than that of the other antimicrobials tested, such as nadifloxacin, fucidic acid, and gentamicin. No strains exhibited reduced OZNX susceptibility. Notably, a low MIC of OZNX was observed even for strains with reduced susceptibility to nadifloxacin, a similar quinolone-based topical antimicrobial. OZNX is a highly potent antimicrobial used in Japan for superficial skin infections caused by S. aureus, such as impetigo contagiosa and related diseases.     

健康者和急性白血病患者体内苯唑西林对阿米卡星药代动力学的影响

 目的:对阿米卡星(AMK)与苯唑西林(OXA)合用健康者和急性白血病患者体内药代动力学进行研究。方法:微量微生物法测定AMK血、尿药浓度。结果:单用与合用AMK的药时曲线均符合二房室模型,健康者体内AMK单用与合用药代动力学参数分别为:K₁₀(0.55±0.22)和(0.42±0.03)h^-1(P<0.05),t_{1/2β(2.11±0.16)和(3.00±0.41)h(P<0.01);AUC(54.7±3.90)和(69.15±4.91)μg·h·ml^-1(P<0.001);急性白血病患者体内,AMK单用与合用药代动力学参数分别为:K12(0.06±0.26)和(1.06±0.10)h^-1(P<0.05),K21(1.47±0.64)和(1.84±0.22)h^-1(P<0.05)。K10(0.71±0.05)和(0.54±0.04)h^-1(P<0.05),t1/2β(1.62±0.19)和(2.22±0.09)h(P<0.01),AUC(39.92±4.20)和(51.53±3.00)μg·h·ml^-1(P<0.001)。结论:健康者和急性白血病患者体内OXA对AMK的药代动力学均有显著的影响。}     

新生儿肺炎链球菌苯唑西林耐药与pbp2B基因突变分析

目的了解新生儿肺炎链球茵（streptococcus pneumoniae，SP）青霉素耐药基因突变及体外苯唑西林耐药状况。方法对分离自新生儿呼吸道的20株肺炎链球茵用纸片扩散法（K—B法）进行青霉素耐药性试验。用套式聚合酶链反应（nPCR）扩增PbP2B基因，对PCR产物进行DNA测序。结果20株肺炎链球茵体外苯唑西林耐药，耐青霉素PbP2B基因突变为点突变，分A、B两类各占95％和5％。结论新生儿肺炎链球茵耐青霉素株pbp2B基因突变类型与DUPLESSIS等报道的不完全相同应引起高度重视。     

Clinical features, epidemiology, antimicrobial resistance, and exotoxin genes (including that of Panton-Valentine leukocidin) of gentamicin-susceptible methicillin-resistant Staphylococcus aureus (GS-MRSA) isolated at a paediatric teaching hospital in New South Wales, Australia

AIMS: To describe the epidemiological, clinical, and laboratory features of gentamicin-susceptible methicillin-resistant Staphylococcus aureus (GS-MRSA) seen at a paediatric teaching hospital. METHODS: Patients from whom GS-MRSA was isolated between 1 January 2001 and 31 December 2002 were enrolled. Retrospective chart review was performed. Susceptibility testing was performed with the Vitek2 system; PCR confirmed methicillin resistance. Phage typing and pulsed field gel electrophoresis (PFGE) was performed (utilising MLST/SCCmec-defined control strains). PCR detection of tst, luk-PV, and entA-entE was performed. RESULTS: Eighty-five per cent of all Staphylococcus aureus isolates during the study period were methicillin-sensitive, and 15% were MRSA (9% GS-MRSA, 6% gentamicin resistant-MRSA). 100 GS-MRSA infections in 98 children were identified: 59 cases of skin/soft tissue, four bone and joint, four surgical site infections, three pneumonia, eight other types, and 22 represented colonisation. Ninety-nine isolates were non-multidrug resistant, but 17 strains were resistant to erythromycin, 7 to tetracyclines, 12 to ciprofloxacin, 11 to fusidic acid, 1 each to rifampicin and mupirocin. 44 isolates were Oceania strain (ST30-MRSA-IV), 20 were Queensland strain (ST93-MRSA-IV), ten were UK EMRSA-15 (ST22-MRSA-IV), eight were WA MRSA-1 (ST1-MRSA-IV), two were WA MRSA-5 (ST8-MRSA-IV), one was WA MRSA-2 (ST78slv-MRSA-IV), one was WA MRSA-15 (ST59-MRSA-IV), and the remainder were sporadics. Twenty patients were Pacific Islanders, of whom 12 had the Oceania strain; ten were Aboriginal, of whom eight had the Queensland strain. Sixty-eight isolates possessed luk-PV, including all Queensland strains and 91% of Oceania strains. Enterotoxin genes were detected in 25% of the isolates, and tst was detected in four isolates. CONCLUSIONS: GS-MRSA is a significant paediatric problem in New South Wales: two minority groups are over-represented, multiple epidemic strains were detected, most community strains possess luk-PV, and many isolates are multidrug resistant.     

几种检测耐甲氧西林金黄色葡萄球菌方法的评价

目的对三种检测耐甲氧西林葡萄球菌方法的可靠性和临床实用性进行评价。方法以PCR检测金黄色葡萄球茵甲氧西林决定因子A（mecA）为金标准,按临床实验室标准化委员会（CLSI）操作规程用苯唑西林纸片扩散法、头孢西丁纸片扩散法、苯唑西林琼脂稀释法对临床分离的155株金黄色葡萄球菌进行检测。结果155株金黄色葡萄球菌经mecA基因检测,耐甲氧西林金黄色葡萄球菌（MRSA）为61．9％（96／155）;头孢西丁纸片扩散法检测MRSA的敏感性和特异性均为100％;苯唑西林纸片扩散法的敏感性为95．8％,特异性为91．5％;苯唑西林琼脂稀释法的敏感性为100％,特异性为98．3％;头孢西丁纸片扩散法优于苯唑西林纸片扩散法和苯唑西林琼脂稀释法。结论头孢西丁纸片扩散法操作简便、敏感性高、特异性好、结果可靠,可作为医院微生物实验室日常工作中检测耐甲氧西林葡萄球菌的常规方法。     

苯唑西林耐药金黄色葡萄球菌的临床分离和药敏情况分析

目的分析苯唑西林耐药金黄色葡萄球菌的临床分离和药敏情况,并与苯唑西林敏感金黄色葡萄球菌的情况进行比较。方法回顾性分析84株金黄色葡萄球菌,依据苯唑西林分为耐药株和敏感株,采用χ2检验分析耐药株和敏感株的来源差异和对每种抗生素的敏感性差异。结果苯唑西林敏感株和耐药株的标本来源和病区分布差异无统计学意义,药敏分析结果显示敏感株和耐药株对呋西地酸、吗啉噁酮、奎奴普丁/达福普汀、替考拉宁和万古霉素的敏感性差异无统计学意义(P0.05),对阿米卡星、克林霉素、环丙沙星、红霉素、庆大霉素、妥布霉素、利福平、复方磺胺和四环素的敏感性差异有统计学意义(P0.05)。结论临床在确诊金黄色葡萄球菌感染时,应区别对待苯唑西林敏感株和耐药株,及时、合理使用抗生素预防和控制感染。