The solithromycin journey—It is all in the chemistry

The macrolide class of antibiotics, including the early generation macrolides erythromycin, clarithromycin and azithromycin, have been used broadly for treatment of respiratory tract infections. An increase of treatment failures of early generation macrolides is due to the upturn in bacterial macrolide resistance to 48% in the US and over 80% in Asian countries and has led to the use of alternate therapies, such as fluoroquinolones. The safety of the fluoroquinolones is now in question and alternate antibiotics for the outpatient treatment of community acquired bacterial pneumonia are needed. Telithromycin, approved in 2003, is no longer used owing to serious adverse events, collectively called the ‘Ketek effects’. Telithromycin has a side chain pyridine moiety that blocks nicotinic acetylcholine receptors. Blockade of these receptors is known experimentally to cause the side effects seen with telithromycin in patients use. Solithromycin is a new macrolide, the first fluoroketolide, which has been tested successfully in two Phase 3 trials and is undergoing regulatory review at the FDA. Solithromycin is differentiated from telithromycin chemically and biologically in that its side chain is chemically different and does not significantly block nicotinic acetylcholine receptors. Solithromycin was well tolerated and effective in clinical trials.     

Structural relationships among chloramphenicol-resistance plasmids of Staphylococcus aureus

Abstract Twelve different chloramphenicol-resistance (Cm^r) plasmids detected in Staphylococcus aureus strains isolated between 1952 and 1981 were characterized by restriction endonuclease, DNA hybridization and heteroduplex analyses. These studies revealed three families of Cm^r plasmids which were distinguished by their chloramphenicol acetyltransferase sequences; the prototype plasmids of the families were pC221, pC223 and pC194. The cat and replication ( rep ) genes of the plasmid pC221 were highly conserved in other pC221 family members and were related to their homologs in the pC223 family plasmids; however, the cat and rep genes of the pC194 family plasmids were distinct.     

In situ detection of antibiotic-resistance elements in single Bacillus cereus spores

Rapid detection of Bacillus spores is a challenging task in food and defense industries. In situ labeling of spores would be advantageous for detection by automated systems based on single-cell analysis. Determination of antibiotic-resistance genes in bacterial spores using in situ labeling has never been developed. Most of the in situ detection schemes employ techniques such as fluorescence in situ hybridization (FISH) that target the naturally amplified ribosomal RNA (rRNA). However, the majority of antibiotic-resistance genes has a plasmidic or chromosomal origin and is present in low copy numbers in the cell. The main challenge in the development of low-target in situ detection in spores is the permeabilization procedure and the signal amplification required for detection. This study presents permeabilization and in situ signal amplification protocols, using Bacillus cereus spores as a model, in order to detect antibiotic-resistance genes. The permeabilization protocol was designed based on the different layers of the Bacillus spore. Catalyzed reporter deposition (CARD)–FISH and in situ polymerase chain reaction (PCR) were used as signal amplification techniques. B. cereus was transformed with the high copy number pC194 and low copy number pMTL500Eres plasmids in order to induce resistance to chloramphenicol and erythromycin, respectively. In addition, a rifampicin-resistant B. cereus strain, conferred by a single-nucleotide polymorphism (SNP) in the chromosome, was used. Using CARD–FISH, only the high copy number plasmid pC194 was detected. On the other hand, in situ PCR gave positive results in all tested instances. This study demonstrated that it was feasible to detect antibiotic-resistance genes in Bacillus spores using in situ techniques. In addition, in situ PCR has been shown to be more sensitive and more applicable than CARD–FISH in detecting low copy targets.     

“Trade-off” in Antarctic bacteria: limnetic psychrotrophs concede multiple enzyme expressions for multiple metal resistance

The present study examines the metal and antibiotic resistant bacteria in ice and water from lakes east and west of the Indian base camp (Maitri) in Antarctica. The isolates from western and eastern lakes showed distinct geographical differences in properties like metal resistance and enzyme expression. This may be attributed to high organic loading in the lakes on the west of Maitri. However, there was no marked geopraphical distinction in antibiotic resistance between the lakes. Bacteria from the lakes on the eastern side showed resistance to three or more metals including mercury while, those from the western were resistant to only 1–2 metals excluding mercury. Multiple enzyme expression was more pronounced in the lakes on the western side. On the eastern side multiple metal resistance was encountered in bacterial isolates associated with fewer enzyme expressions suggesting a “trade-off”. Thus these Antarctic isolates from the east trade their ability to express multiple enzymes for developing resistance to multiple metals including mercury.     

临床分离4544株革兰阴性杆菌的耐药分布与变迁

目的了解玉溪市革兰阴性杆菌的耐药分布与变迁,为临床用药提供依据。方法对玉溪市人民医院1999—2004年临床各科送检的各类标本中培养分离出的4544株革兰阴性杆菌作回顾性分析。结果9种（属）细菌对25种药物的药敏结果耐药率〉50％者72种次（40．9％）,〈20％者44种次（25．0％）。总的耐药情况为不动杆菌和阴沟肠杆菌最高,铜绿假单胞菌和大肠埃希菌次之,甲型副伤寒沙门菌和福氏志贺菌最低。亚胺培南对多种细菌有较高的敏感覆盖率。有4种细菌对10种抗菌药物耐药率的上升具有临床意义（P〈0.01或P〈0．05）,其中以甲型副伤寒沙门菌对氟喹诺酮类上升最为显著。结论临床分离革兰阴性杆菌的耐药形势十分严峻,应定期监测区域内细菌的耐药变化．指导临床合坪用药。     

Analysis of plasmid genome evolution based on nucleotide-sequence comparison of two related plasmids of Escherichia coli

Plasmid Rsc13, a small derivative of the plasmid R1, contains a region necessary for replication as well as a complete copy (4957 bp) of the ampicillin resistance transposon, Tn3. We determined the nucleotide sequence of the replication region of Rsc13 to be 2937 bp and then compared this region (designated the 2.9-kb region) to the analogous region of pSM1, a small derivative of the plasmid R100 which has common ancestry with R1. Rsc13 and pSM1 were 96% homologous in this 2.9-kb region except for a discrete region of about 250 bp which showed only 44% homology. The sequence and distribution of nucleotide substitutions between Rsc13 and pSM1 supported a map of possible genes and sites which have previously been seen in the replication region of Rsc13 and pSM1 which showed only 44% homology. Analysis of the amino acid sequence and predicted conformation of the two RepA2 polypeptides, however, suggested that they were very similar. We proposed that the repA2 region of R1 and R100 was replaced by a substitution of a short DNA segment from another plasmid which was evolutionarily related to R1 and R100 but had more divergence. This event may have been mediated by a mechanism similar to that of gene conversion as described in eukaryotic systems.     

益生芽孢杆菌对抗生素的敏感性及其质粒的检测

采用滤纸片抑菌圈法测定３０株益生芽孢杆菌对１５种抗生素的敏感性。结果９０％菌株抗磺胺嘧啶,对其余抗生素大部分菌株敏感。用改良碱裂解法提取３０株菌质粒,只有６１２９菌株含有一个大约４３ｋｂ的质粒,质粒消除实验证明该质粒与磺胺嘧啶抗性无关。     

糖尿病足复发感染病原菌的分布及耐药性分析

目的对糖尿病足复发感染病原菌的分布及耐药性进行分析。方法选取杭州师范大学附属医院2014年6月至2015年6月收治的且符合纳入标准的糖尿病足复发感染患者120例。对所有患者糖尿病足复发感染病原菌的分布及耐药性进行分析。结果 120例糖尿病足复发感染患者共检出病原菌145株,其中18例为混合细菌感染。145株细菌中革兰阳性菌91株(62.8%),前三位的分别为金黄色葡萄球菌、粪肠球菌、链球菌,分别占28.3%、24.8%、6.2%;革兰阴性菌41株(28.3%),以大肠埃希菌、绿脓假单胞菌属、奇异变形杆菌为主,分别占6.9%、6.2%、5.5%。不同病原菌对常用抗菌药物呈现不同程度的耐药;革兰阳性球菌对青霉素、红霉素耐药严重,而对头孢曲松、万古霉素较为敏感,对万古霉素未出现耐药情况。革兰阴性菌对亚胺培南、美罗培南均敏感,其次对阿米卡星较敏感,对氨苄西林耐药率最高。结论糖尿病足患者复发感染病原菌分布广泛,应根据药物敏感性试验结果及时调整抗菌药物,以利于促进创面早期愈合。     

宫颈癌患者阴道分泌物非厌氧菌菌群分布及常见菌药敏分析

目的：探讨宫颈癌患者阴道分泌物非厌氧菌菌群分布和常见菌的药敏情况。方法：对87例住院患者的阴道分泌物进行常规培养(不包括厌氧菌、淋病奈瑟菌及支原体培养)和常见菌的药敏测定。结果：87分标本中细菌培养阳性者共86分．阳性率98．8％;共检出菌株161株,革兰阴性菌125株(77．6％),其中嗜麦芽窄食单胞菌和鲁氏不动杆菌分别有49株(39．2％)和43株(34．4％);革兰阳性菌36株(22．4％)．以葡萄球菌和肠球菌为主,分别有18株(50．0％)和9株(25．0％)。药敏结果显示,常见革兰阴性杆菌对氨苄西林的敏感性最差,对亚胺培南、头孢三代的敏感性差别较大．革兰阳性球菌对青霉素的耐药率最高,万古霉素的敏感性最高。结论：宫颈癌患者的阴道分泌物需氧菌群以革兰阴性菌为主,尤以嗜麦芽窄食单胞菌和鲁氏不动杆菌最为常见,临床上根据阴道分泌物菌群分布和药敏情况,在术前采用合适的冲洗液可有效地减少术后感染的发生。