Mechanisms of Fluoroquinolone and Aminoglycoside Resistance in Keratitis-AssociatedPseudomonas aeruginosa

Safety and efficacy of fortified antibiotics and fluoroquinolones for the treatment of bacterial keratitis: A meta-analysis

PURPOSE

To compare the safety and efficacy of fortified antibiotics and fluoroquinolones in the treatment of bacterial keratitis.

METHODS

PubMed, EMBASE, Cochrane Library, CNKI, Wanfang database and VIP database were systematically searched for randomized controlled trials (RCT) of treatment of bacterial keratitis with fortified antibiotics and fluoroquinolones. Rev Man 5.3 software was used to analyze outcome index cure rate, time to cure, and adverse events in a meta-analysis.

RESULTS

After literature search and screening, 9 randomized controlled trials were included in this study. Compared with traditional fortified antibiotic therapy, fluoroquinolones show consistency in terms of cure rate and incidence of adverse events: cure rates (OR=0.99, 95% CI: 0.75, 1.30) and incidence of adverse events (OR=0.75, 95% CI: 0.48, 1.17). However, the time to cure for fluoroquinolones was shorter than that of fortified antibiotics (MD=0.96, 95% CI: 0.50, 1.41).

CONCLUSION

The cure rate and safety of fluoroquinolones are equivalent to those of fortified antibiotics, so it seems reasonable to use fluoroquinolones as the preferred treatment for bacterial keratitis.

Emergence and Transfer of Plasmid-Harbored rmtB in a Clinical Multidrug-Resistant Pseudomonas aeruginosa Strain

Multidrug-resistant (MDR) Pseudomonas aeruginosa poses a great challenge to clinical treatment. In this study, we characterized a ST768 MDR P. aeruginosa strain, Pa150, that was isolated from a diabetic foot patient. The minimum inhibitory concentration (MIC) assay showed that Pa150 was resistant to almost all kinds of antibiotics, especially aminoglycosides. Whole genome sequencing revealed multiple antibiotic resistant genes on the chromosome and a 437-Kb plasmid (named pTJPa150) that harbors conjugation-related genes. A conjugation assay verified its self-transmissibility. On the pTJPa150 plasmid, we identified a 16S rRNA methylase gene, rmtB, that is flanked by mobile genetic elements (MGEs). The transfer of the pTJPa150 plasmid or the cloning of the rmtB gene into the reference strain, PAO1, significantly increased the bacterial resistance to aminoglycoside antibiotics. To the best of our knowledge, this is the first report of an rmtB-carrying conjugative plasmid isolated from P. aeruginosa, revealing a novel possible transmission mechanism of the rmtB gene.

Characteristics of Antibiotic Resistance and Tolerance of Environmentally Endemic Pseudomonas aeruginosa

Antibiotic-resistant bacteria remain a serious public health threat. In order to determine the percentage of antibiotic-resistant and -tolerant Pseudomonas aeruginosa cells present and to provide a more detailed infection risk of bacteria present in the environment, an isolation method using a combination of 41 °C culture and specific primers was established to evaluate P. aeruginosa in the environment. The 50 strains were randomly selected among 110 isolated from the river. The results of antibiotic susceptibility evaluation showed that only 4% of environmental strains were classified as antibiotic-resistant, while 35.7% of clinical strains isolated in the same area were antibiotic-resistant, indicating a clear difference between environmental and clinical strains. However, the percentage of antibiotic-tolerance, an indicator of potential resistance risk for strains that have not become resistant, was 78.8% for clinical strains and 90% for environmental strains, suggesting that P. aeruginosa, a known cause of nosocomial infections, has a high rate of antibiotic-tolerance even in environmentally derived strains. It suggested that the rate of antibiotic-tolerance is not elicited by the presence or absence of antimicrobial exposure. The combination of established isolation and risk analysis methods presented in this study should provide accurate and efficient information on the risk level of P. aeruginosa in various regions and samples.

Pathogenesis of the Pseudomonas aeruginosa Biofilm: A Review

Pseudomonas aeruginosa is associated with several human infections, mainly related to healthcare services. In the hospital, it is associated with resistance to several antibiotics, which poses a great challenge to therapy. However, one of the biggest challenges in treating P. aeruginosa infections is that related to biofilms. The complex structure of the P. aeruginosa biofilm contributes an additional factor to the pathogenicity of this microorganism, leading to therapeutic failure, in addition to escape from the immune system, and generating chronic infections that are difficult to eradicate. In this review, we address several molecular aspects of the pathogenicity of P. aeruginosa biofilms.

Pseudomonas aeruginosa Pneumonia: Evolution of Antimicrobial Resistance and Implications for Therapy

Pseudomonas aeruginosa (PA), a non-lactose-fermenting gram-negative bacillus, is a common cause of nosocomial infections in critically ill or debilitated patients, particularly ventilator-associated pneumonia (VAP), and infections of urinary tract, intra-abdominal, wounds, skin/soft tissue, and bloodstream. PA rarely affects healthy individuals, but may cause serious infections in patients with chronic structural lung disease, comorbidities, advanced age, impaired immune defenses, or with medical devices (e.g., urinary or intravascular catheters, foreign bodies). Treatment of pseudomonal infections is difficult, as PA is intrinsically resistant to multiple antimicrobials, and may acquire new resistance determinants even while on antimicrobial therapy. Mortality associated with pseudomonal VAP or bacteremias is high (> 35%) and optimal therapy is controversial. Over the past three decades, antimicrobial resistance (AMR) among PA has escalated globally, via dissemination of several international multidrug resistant "epidemic" clones. We discuss the importance of PA as a cause of pneumonia including health care-associated pneumonia, hospital-acquired pneumonia, VAP, the emergence of AMR to this pathogen, and approaches to therapy (both empirical and definitive).

Photodynamic therapy for treatment of bacterial keratitis

Microbial keratitis is the main cause of corneal opacification and the fourth leading cause of blindness worldwide, with bacteria the major infectious agent. Recently, bacterial keratitis has become a serious threat due to routine use of antibiotics leading to selection of resistant and multidrug-resistant bacteria strains. New approaches for treatment of bacterial keratitis are necessary to outcome the increasing antibiotic resistance. Antimicrobial photodynamic therapy is based on three agents: photosensitizer, oxygen, and light radiation. This therapy has been successful for treatment of infections in different tissues and organs as well as against different type of infectious agents and no resistance development. Also, new photosensitizers are being developed that has increased the spectrum of therapeutic protocols for treatment of a number of infectious diseases. Thus, antimicrobial photodynamic therapy has an extraordinary potential for treatment of those bacterial keratitis cases that actually are not solved by traditional antibiotic therapy.

The many antibiotic resistance and tolerance strategies of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a bacterial pathogen associated with a wide range of infections and utilizes several strategies to establish and maintain infection including biofilm production, multidrug resistance, and antibiotic tolerance. Multidrug resistance in P. aeruginosa, as well as in all other bacterial pathogens, is a growing concern. Aminoglycoside resistance, in particular, is a major concern in P. aeruginosa infections and must be better understood in order to maintain effective clinical treatment. In this review, the various antibiotic resistance and tolerance mechanisms of Pseudomonas are explored including: classic mutation driven resistance, adaptive resistance, persister cells, small colony variants, phoenix colonies, and biofilms. It is important to further characterize each of these phenotypes and continue to evaluate antibiotic surviving isolates for novel driving mechanisms, so that we are better prepared to combat the rising number of recurrent and recalcitrant infections.

Role of Aminoglycoside-Modifying Enzymes (AMEs) in Resistance to Aminoglycosides among Clinical Isolates of Pseudomonas aeruginosa in the North of Iran

In recent years, the prevalence of resistance to aminoglycosides among clinical isolates of Pseudomonas aeruginosa is increasing. The aim of this study was to investigate the role of aminoglycoside-modifying enzymes (AMEs) in resistance to aminoglycosides in clinical isolates of P. aeruginosa. The clinical isolates were collected from different hospitals. Disk agar diffusion test was used to determine the antimicrobial resistance pattern of the clinical isolates, and the minimum inhibitory concentration of aminoglycosides was detected by microbroth dilution method. The PCR was performed for discovery of aminoglycoside-modifying enzyme-encoding genes. Among 100 screened isolates, 43 (43%) isolates were resistant to at least one tested aminoglycosides. However, 13 (13%) isolates were resistant to all tested aminoglycosides and 37 isolates were detected as multidrug resistant (MDR). The resistance rates of P. aeruginosa isolates against tested antibiotics were as follows: ciprofloxacin (41%), piperacillin-tazobactam (12%), cefepime (32%), piperacillin (26%), and imipenem (31%). However, according to the MIC method, 13%, 32%, 33%, and 37% of the isolates were resistant to amikacin, gentamicin, tobramycin, and netilmicin, respectively. The PCR results showed that AAC(6')-Ib was the most commonly (26/43, 60.4%) identified AME-encoding gene followed by AAC(6')-IIa (41.86%), APH(3')-IIb (34.8%), ANT(3 ^″ )-Ia (18.6), ANT(2 ^″ )-Ia (13.95%), and APH(3 ^″ )-Ib (2.32%). However, APH(3')-Ib was not found in any of the studied isolates. The high prevalence of AME-encoding genes among aminoglycoside-resistant P. aeruginosa isolates in this area indicated the important role of AMEs in resistance to these antibiotics similar to most studies worldwide. Due to the transmission possibility of these genes between the Gram-negative bacteria, we need to control the prescription of aminoglycosides in hospitals.

Research Progress of Alzheimer's Disease Therapeutic Drugs: Based on Renin-Angiotensin System Axis

It is widely recognized that Alzheimer's disease (AD) has a complicate link to renin-angiotensin system (RAS). It is known that cerebrovascular disease has some connections with AD, but most of the studies are still conducted in parallel or independently. Although previous research came up with large number of hypotheses about the pathogenesis of AD, it does not include the mechanism of RAS-related regulation of AD. It has been found that many components of RAS have been changed in AD. For example, the multifunctional and high-efficiency vasoconstrictor Ang II and Ang III with similar effects are changed under the action of other RAS signal peptides; these signal peptides are believed to help improve nerve injury and cognitive function. These changes may lead to neuropathological changes of AD, and progressive defects of cognitive function, which are association with some hypotheses of AD. The role of RAS in AD gradually attracts our attention, and RAS deserved to be considered carefully in the pathogenesis of AD. This review discusses the mechanisms of RAS participating in the three current hypotheses of AD: neuroinflammation, oxidative stress and amyloid-β protein (Aβ) hypothesis, as well as the drugs that regulate RAS systems already in clinical or in clinical trials. It further demonstrates the importance of RAS in the pathogenesis of AD, not only because of its multiple aspects of participation, which may be accidental, but also because of the availability of RAS drugs, which can be reused as therapies of AD.