Eukaryotic and prokaryotic stomatins: the proteolytic link

The 32kD membrane protein stomatin was first studied because it is deficient from the red cell membrane in two forms of the class of haemolytic anaemias known as "hereditary stomatocytosis." The hallmark of these conditions is a plasma membrane leak to the monovalent cations Na+ and K+: the protein is missing only in the most severely leaky of these conditions. No mutation has ever been found in the stomatin gene in these conditions. Stomatin-like proteins have been identified in all three domains of biology, yet their function remains enigmatic. Although the murine knock-out is without phenotype, we have identified a family showing a splicing defect in the stomatin mRNA, in which affected children showed a catastrophic multisystem disease not inconsistent with the now-known wide tissue distribution of stomatin. We report here a study of strongly homologous stomatin-like genes in prokaryotes, which reveals a close connection with a never-studied gene erroneously known as "nfed." This gene codes for a hydrophobic protein with a probable serine protease motif. It is possible that these stomatin-like genes and those which are known as"nfed" form an operon, suggesting that the two protein products are aimed at a common function. The corollary is that stomatin could be a partner protein for a membrane-bound proteolytic process, in both prokaryotes and in eukaryotes generally: this idea is consistent with experimental evidence.     

阿洛西林联合庆大霉素治疗铜绿假单胞菌肺部感染72例

目的：了解阿洛西林联合庆大霉素治疗铜绿假单胞菌肺部感染的疗效。方法：选择2009年12月～2013年12月期间在河南省三门峡监狱医院内就诊的72例铜绿假单胞菌肺部感染病例,随机分成2组,治疗组给予阿洛西林和庆大霉素联合应用,对照组给予头孢曲松钠单独使用,疗程均为7～14天。结果：治疗组总有效率为91．7％,细菌清除率为94．4％,不良反应发生率为5．6％,与对照组比较无显著差异。结论：对于肝、肾功能正常的铜绿假单胞菌肺部感染,阿洛西林和庆大霉素连用可作为临床治疗方案之一,且所需费用较头孢曲松钠等新型抗生素低,使广大患者更易接受。     

l‐Methionine anti‐biofilm activity against Pseudomonas aeruginosa is enhanced by the cystic fibrosis transmembrane conductance regulator potentiator,ivacaftor

Background

Biofilms may contribute to refractory chronic rhinosinusitis (CRS), as they lead to antibiotic resistance and failure of effective clinical treatment. l ‐Methionine is an amino acid with reported biofilm‐inhibiting properties. Ivacaftor is a cystic fibrosis transmembrane conductance regulator (CFTR) potentiator with mild antimicrobial activity via inhibition of bacterial DNA gyrase and topoisomerase IV. The objective of this study was to evaluate whether co‐treatment with ivacaftor and l ‐methionine can reduce the formation of Pseudomonas aeruginosa biofilms.

Methods

P aeruginosa (PAO‐1 strain) biofilms were studied in the presence of l ‐methionine and/or ivacaftor. For static biofilm assays, PAO‐1 was cultured in a 48‐well plate for 72 hours with stepwise combinations of these agents. Relative biofilm inhibitions were measured according to optical density of crystal violet stain at 590 nm. Live/dead assays (BacTiter‐Glo? assay, Promega) were imaged with laser scanning confocal microscopy. An agar diffusion test was used to confirm antibacterial effects of the drugs.

Results

l ‐Methionine (0.5 μM) significantly reduced PAO‐1 biofilm mass (32.4 ± 18.0%; n = 4; p < 0.001) compared with controls. Low doses of ivacaftor alone (4, 8, and 12 μg/mL) had no effect on biofilm formation. When combined with ivacaftor (4 μg/mL), a synergistic anti‐biofilm effect was noted at 0.05 μM and 0.5 μM of l ‐methionine (two‐way analysis of variane, p = 0.0415) compared with corresponding concentrations of l ‐methionine alone.

Conclusion

Ivacaftor enhanced the anti‐biofilm activity of l ‐methionine against the PAO‐1 strain of P aeruginosa. Further studies evaluating the efficacy of ivacaftor/l ‐methionine combinations for P aeruginosa sinusitis are planned.

     

Incidence of Pseudomonas aeruginosa bacteremia: a population-based study

Background

The incidence of Pseudomonas aeruginosa bacteremia has not been defined in a population-based investigation.

Methods

We performed a retrospective, population-based incidence study using resources of the Rochester Epidemiology Project of Olmsted County, Minnesota. We identified all Olmsted County residents with P. aeruginosa bacteremia between January 1, 1997, and December 31, 2006, by microbiology records in the only 2 laboratories in the county. Medical records were reviewed to confirm diagnosis, residency status, and clinical characteristics.

Results

Age-adjusted incidence per 100,000 person-years was 10.8 (95% confidence interval [CI], 7.5-14.0) in men and 3.7 (95% CI, 2.2-5.2) in women for total P. aeruginosa bacteremia, and 8.4 (95% CI, 5.5-11.2) in men and 2.5 (95% CI, 1.3-3.8) in women for monomicrobial P. aeruginosa bacteremia. There was no significant change in incidence of total P. aeruginosa bacteremia during the past decade (P = .418). Incidence increased exponentially with age, with a greater magnitude of increase in men compared with women for total and monomicrobial P. aeruginosa bacteremia (P = .007 and P = .015, respectively). In patients with monomicrobial P. aeruginosa bacteremia, the median age was 69 years, and 78.4% of cases were either nosocomial or health care associated. Most patients had multiple comorbid conditions. The urinary tract was the most common primary source of infection. The 28-day all-cause mortality of monomicrobial P. aeruginosa bacteremia was 25.5%. In vitro susceptibility to ciprofloxacin was 95.3%.

Conclusion

To our knowledge, this is the first population-based incidence study of P. aeruginosa bacteremia. The incidence of P. aeruginosa bacteremia has remained stable during the past decade. Fluoroquinolone susceptibility is high among local P. aeruginosa bacteremia isolates.     

Delafloxacin: a novel fluoroquinolone with activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa

Introduction: The resistance to current antimicrobial agents, including fluoroquinolones, has continued to grow among various pathogens indicating a need for new antimicrobials to combat multi-drug resistant (MDR) organisms. In June 2017, delafloxacin received approval by the US Food and Drug Administration for the treatment of acute bacterial skin and skin-structure infections (ABSSSIs) in adults caused by designated susceptible bacteria.

Areas covered: This review describes the pharmacology, pharmacodynamics, pharmacokinetics, product information, efficacy, and safety of delafloxacin.

Expert commentary: Delafloxacin is a novel oral and intravenous fluoroquinolone with activity against methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, offering a new option for the treatment of ABSSSI and potentially for complicated urinary tract infections and severe community-acquired bacterial pneumonia.     

铜绿假单胞菌对美罗培南耐药的危险因素分析

目的分析耐铜绿假单胞菌对美罗培南耐药的危险因素,为临床合理使用抗菌药物,减少耐药的发生提供依据。方法本研究以2012年1月至2014年1月在北京市大兴区人民医院住院治疗且血培养出现铜绿假单胞菌的患者为研究对象。所有的数据通过回顾原始病历进行收集。对所取得的数据进行费舍尔确切分析和逻辑回归分析。结果共有695例患者被纳入该研究,其中对美罗培南耐药的为401例(58%)。研究确定了3个诱导耐美罗培南的铜绿假单胞菌的危险因素:1使用碳青霉烯类药物超过1周;2重症监护病房治疗超过1周;3机械通气治疗超过72 h。结论对于需要抗菌药物治疗的患者应尽早采用细菌学方法确诊致病菌,减少经验性使用碳青霉烯类抗菌药物的时间;加强重症监护病房的消毒隔离措施;尽量缩短机械通气的治疗时间。     

Characterization of bacteriophages infecting clinical isolates of Pseudomonas aeruginosa stored in a culture collection

Some clinical isolates of Pseudomonas aeruginosa stored in our culture collection did not grow or grew poorly and showed lysis on the culture plates when removed from the collection and inoculated on MacConkey agar. One hypothesis was that bacteriophages had infected and killed those clinical isolates. To check the best storage conditions to maintain viable P. aeruginosa for a longer time, clinical isolates were stored at various temperatures and were grown monthly. We investigated the presence of phage in 10 clinical isolates of P. aeruginosa stored in our culture collection. Four strains of P. aeruginosa were infected by phages that were characterized by electron microscopy and isolated to assess their ability to infect. The best condition to maintain the viability of the strains during storage was in water at room temperature. Three Siphoviridae and two Myoviridae phages were visualized and characterized by morphology. We confirmed the presence of bacteriophages infecting clinical isolates, and their ability to infect and lyse alternative hosts. Strain PAO1, however, did not show lysis to any phage. Mucoid and multidrug resistant strains of P. aeruginosa showed lysis to 50% of the phages tested.     

Surface roughness enhances upward migration of bacteria on polymer fibers above liquid cultures

Monofilament polypropylene (PP) fibers, very similar to fibers that have been used as monofilament tailstrings of interuterinc contraceptive devices, were suspended vertically in bacterial liquid monocultures so that a portion of a fiber extended above the liquid surface. In some cases these highly oriented, cold drawn fibers were abraded prior to insertion in the cultures in order to produce surface roughness characterized by axial channels and protruding microfibrils that partially peeled from the fiber surface thereby forming the channels. Extent of migration on a fiber was assessed by aseptically cutting it into small segments, followed by culturing each segment on agar containing growth medium. Such assessment of the PP fibers after 48 h of incubation in the cultures revealed upward migration of Eschericia coli, Pseudomonas aeruginosa, and Staphylococcus aureus over significantly longer distances on the pre-roughened fibers than on those not so pre-treated. Mean measured distances of migration during 48 h were: for E. coli 2.7 ± 0.6 mm on roughened fibers (n = 16) and 0.4±0.7 mm on fibers not roughened (n = 17); for S. aureus 9.0±4.3 mm on roughened fibers (n = 13) and 0.2± 0.3 mm on fibers not roughened (n = 14); for P. aeruginosa 8.5± 3.7 mm on roughened fibers (n = 26) and 0.2± 0.5 mm on fibers not roughened (n = 5). Although no statistically significant (95% confidence level) difference could be discerned between the migration distances of S. aureus and P. aeruginosa, each of these species migrated a greater distance on the PP than did E. coli. The migrations observed are attributed predominantly to wicking of the liquid cultures upward in the axial grooves developed on the surface of the PP by the eruption and peeling of microfibrils from the surface. Surface tension of the growth medium was significantly lower than that of water and its contact angle on PP was less than 90 deg, thereby indicating a tendency to wet the PP. Bacterial growth in the medium further reduced its contact angle on PP, thereby indicating an even greater tendency to wet PP after such growth.