Multidrug-Resistant Pseudomonas Infections: Hard to Treat, But Hope on the Horizon?

Homalomena pineodora essential oil nanoparticle inhibits diabetic wound pathogens

Essential oil of Homalomena pineodora inhibits diabetic pathogens; however, the activity was not sustainable when applied as wound dressing. This study aims to synthesise the essential oil nanoparticle using chitosan. The nanoparticles were synthesised with ion gelation method, confirmed by spectroscopic analysis. The spherical nanoparticles display a size of 70 nm, with strong surface charge of +24.10 mV. The nanoparticles showed an initial burst release followed by a slow release pattern for 72 h, following the first order of kinetic. The release behaviour was ideal for wound dressing. The antimicrobial activity was broad spectrum. The formation of nanoparticle enhanced the antimicrobial efficacy of the essential oil. The nanoparticle also showed a concentration-dependent killing behaviour on time-kill assay. In the 3D collagen wound models, the nanoparticles reduced the microbial growth by 60-80%. In conclusion, H. pineodora nanoparticles showed pharmaceutical potential in inhibiting microbial growth on diabetic ulcers.

First Study of Antimicrobial Activity of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Against Pseudomonas aeruginosa Isolated from Patients with Urinary Tract Infection in Tehran, Iran

Purpose

Pseudomonas aeruginosa causes complicated and/or nosocomial UTI. These infections are usually associated with severe and multi-drug resistant P. aeruginosa isolates. As there is no study about the activity of novel antibiotics ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) against P. aeruginosa isolates in Iran, we aimed to evaluate for the first time the efficacy of these agents against P. aeruginosa isolated from patients with UTI in Iran. Then, the genetic diversity of the resistant isolates was assayed.

Methods

In this study, a total of 200 P. aeruginosa isolates were collected from patients with UTI in Tehran, Iran. Disk diffusion and Minimum Inhibitory Concentration (MIC) methods were applied to determine the resistance of the isolates to CZA, C/T, and the other antibiotics. Extended-spectrum β-lactamases (ESBLs) and Metallo Beta Lactamase (MBL) production were assayed by Combination disk diffusion test (CDDT). Polymerase chain reaction (PCR) was carried out to detect the resistance genes, including beta-lactamases and carbapenemases genes. Finally, genomic analysis of the isolates was performed using the Pulse field gel electrophoresis (PFGE).

Results

Among the isolates, 16 (8%) were resistant to CZA and C/T that MIC confirmed it. The resistant isolates showed high resistance to the other classes of antibiotics. Among the resistant isolates, 31.2% and 75% were ESBL and MBL producers, respectively. The prevalence of bla_OXA10, bla_VIM, bla_OXA48, bla_OXA2, and bla_CTX-M was 100%, 50%, 31.2%, 25%, and 12.5%. Furthermore, two isolates (12.5%) harbored bla_PER and bla_NDM genes. The resistant isolates were grouped into 14 distinct pulsotypes and two shared pulsotypes were found.

Conclusion

Ceftazidime-avibactam and ceftolozane-tazobactam showed high activity against the P. aeruginosa isolated from patients with UTI in Iran. The low rate of resistance to the antibiotics is also alarming and should be considered to avoid further spreading of the antibiotic resistance among the P. aeruginosa and the other bacteria.

Molecular epidemiology of clinically high-risk Pseudomonas aeruginosa strains: Practical overview

In recent years, numerous outbreaks of multidrug-resistant Pseudomonas aeruginosa have been reported across the world. Once an outbreak occurs, besides routinely testing isolates for susceptibility to antimicrobials, it is required to check their virulence genotypes and clonality profiles. Replacing pulsed-field gel electrophoresis DNA fingerprinting are faster, easier-to-use, and less expensive polymerase chain reaction (PCR)-based methods for characterizing hospital isolates. P. aeruginosa possesses a mosaic genome structure and a highly conserved core genome displaying low sequence diversity and a highly variable accessory genome that communicates with other Pseudomonas species via horizontal gene transfer. Multiple-locus variable-number tandem-repeat analysis and multilocus sequence typing methods allow for phylogenetic analysis of isolates by PCR amplification of target genes with the support of Internet-based services. The target genes located in the core genome regions usually contain low-frequency mutations, allowing the resulting phylogenetic trees to infer evolutionary processes. The multiplex PCR-based open reading frame typing (POT) method, integron PCR, and exoenzyme genotyping can determine a genotype by PCR amplifying a specific insertion gene in the accessory genome region using a single or a multiple primer set. Thus, analyzing P. aeruginosa isolates for their clonality, virulence factors, and resistance characteristics is achievable by combining the clonality evaluation of the core genome based on multiple-locus targeting methods with other methods that can identify specific virulence and antimicrobial genes. Software packages such as eBURST, R, and Dendroscope, which are powerful tools for phylogenetic analyses, enable researchers and clinicians to visualize clonality associations in clinical isolates.

Ceftolozane-tazobactam- and ceftazidime-avibactam-resistant Pseudomonas aeruginosa mastoiditis

Pseudomonas aeruginosa is an important bacterial cause of a variety of infections and is associated with high morbidity and mortality. Infections caused by this bacterium are becoming more difficult to treat due to increasing resistance to many of the available antibiotics. Ceftolozane–tazobactam and ceftazidime–avibactam are two new cephalosporin/β-lactamase inhibitor combination antimicrobials that have demonstrated excellent in vitro activity against several multi-drug-resistant pathogens, including multi-drug-resistant P. aeruginosa. Cases of infections with isolates of multi-drug-resistant P. aeruginosa that are resistant to both of these antimicrobials have rarely been reported. We report a case of mastoiditis caused by P. aeruginosa that was resistant to both ceftolozane–tazobactam and ceftazidime–avibactam.

Genotypes, carbapenemase carriage, integron diversity and oprD alterations among carbapenem-resistant Pseudomonas aeruginosa from Russia

Pseudomonas aeruginosa is a serious opportunistic pathogen demonstrating a high level of resistance to many groups of antibiotics, including carbapenems. This study aimed to characterise the molecular epidemiology and prevalence of mobile genetic elements associated with resistance to carbapenems among P. aeruginosa (CRPA) clinical isolates. Among 145 carbapenem-resistant P. aeruginosa isolates, 34 different sequence types (STs) were detected; the six most common STs were ST654 (24%), ST235 (24%), ST111 (8%), ST446 (6%), ST357 (5%) and ST2592 (a novel single-locus variant of ST357) (4%). A carbapenemase gene was found in 94 isolates (64.8%). The bla_VIM-2 gene was harboured by 64 isolates (44.1%) restricted to ST111, ST235 and ST654, and the bla_GES-type and bla_OXA-10 group genes were each detected in 15 isolates (10.3%); none of other tested carbapenemase genes, including bla_IMP, bla_NDM and bla_GIM, were detected. Among the bla_VIM-2-positive isolates, five types of bla_VIM-2-containing integrons were discovered, including In56, In559, In59-like, In59 and In249. The oprD gene was disrupted by an insertion sequence (IS) in 15.9% of isolates. Overall, five types of IS elements were found (ISPsme1, ISPa1328, ISPa26, ISPst2 and ISPa195). Observed rearrangements within variable regions of bla_VIM-2-carrying integrons in conjunction with the discovery of a novel type of oprD-disrupting IS element illustrate the ongoing evolution of CRPA a, which warrants further investigation.

Effect of broad-spectrum antibiotics on bacterial translocation in burned or septic rats

Background:

Antibiotics are frequently used to treat critically ill patients, and its use is often accompanied by intestinal dysbiosis that might further lead to bacterial translocation (BT). Nevertheless, studies on the relationship between antibiotic therapy and BT are rare. In the present study, we investigated the effect of broad-spectrum antibiotics on BT in an experimental rat model of burn or sepsis injury.

Methods:

The septic rat model was simulated by a second insult with lipopolysaccharides after burn injury. Ninety-two male Sprague-Dawley rats were randomly divided into control, burn, and sepsis groups (n = 8 or 9, each group), and the latter two groups were then treated with imipenem or ceftriaxone for 3 or 9 days. The mesenteric lymph nodes, liver, lungs, and blood were collected at each time point under sterile conditions for quantitative bacterial culture and strain identification. The differences between the groups were compared by Fisher exact test or Mann-Whitney U test.

Results:

Only minimal Escherichia coli translocation to the mesenteric lymph nodes was observed in the normal control group, in which the BT rate was 12.5%. Burn injury did not affect the BT rate (Burn group vs. Control group, 12.5% vs. 12.5%, P = 1.000), whereas the BT rate showed an increased trend after the second insult with lipopolysaccharide (Sepsis group vs. Control group, 44.4% vs. 12.5%, P = 0.294), and many strains of Enterobacteria spp. were detected in distant organs (liver, lung, and blood) [Sepsis group vs. Control group, 0 (0,3) vs. 0 (0,0), U = 20, P = 0.045]. After the antibiotic treatment, BT to the distant organs was increased in burned rats [Burn IT3 group vs. Burn group, 0 (0,2) vs. 0 (0,0); Burn IT9 group vs. Burn group, 0 (0,1) vs. 0 (0,0); Burn CT9 group vs. Burn group, 0 (0,2) vs. 0 (0,0); all U = 20 and P = 0.076] but decreased in septic rats [Sepsis CT3 group vs. Sepsis group, 0 (0,0) vs. 0 (0,3), U = 20, P = 0.045]. The total amount of translocated bacteria, regardless of which antibiotic was used, was increased in burned rats [Burn IT9 group vs. Burn group, 2.389 (0,2.845) vs. 0 (0,2.301) Log₁₀ colony-forming units (CFU)/g, U = 14, P = 0.034; Burn CT3 group vs. Burn group, 2.602 (0,3.633) vs. 0 (0,2.301) Log₁₀ CFU/g, U = 10.5, P = 0.009], but there was a slightly decreased trend in septic rats [Sepsis IT9 group vs. Sepsis group, 2.301 (2,3.146) vs. 0 (0,4.185) Log₁₀ CFU/g, U = 36, P = 0.721; Sepsis CT9 group vs. Sepsis group, 2 (0,3.279) vs. 0 (0,4.185) Log₁₀ CFU/g, U = 32.5, P = 0.760]. Remarkably, the quantity of Enterococci spp. dramatically increased after broad-spectrum antibiotic treatment in both the burned and septic groups [Burn IT3 group vs. Burn group, 1 (0,5.164) vs. 0 (0,0) Log₁₀ CFU/g, U = 16; Burn IT9 group vs. Burn group, 1 (0,2.845) vs. 0 (0,0) Log₁₀ CFU/g, U = 16; Burn CT3 group vs. Burn group, 2.602 (0,3.633) vs. 0 (0,0) Log₁₀ CFU/g, U = 8; Burn CT9 group vs. Burn group, 1 (0,4.326) vs. 0 (0,0) Log₁₀ CFU/g, U = 16; Sepsis IT3 group vs. Sepsis group, 2.477 (0,2.903) vs. 0 (0,0) Log₁₀ CFU/g, U = 4.5; Sepsis IT9 group vs. Sepsis group, 2 (0,3.146) vs. 0 (0,0) Log₁₀ CFU/g, U = 9; Sepsis CT3 group vs. Sepsis group, 1.151 (0,2.477) vs. 0 (0,0) Log₁₀ CFU/g, U = 18; Sepsis CT9 group vs. Sepsis group, 2 (0,3) vs. 0 (0,0) Log₁₀ CFU/g, U = 13.5; all P < 0.05].

Conclusions:

Broad-spectrum antibiotics promote BT in burned rats but prevent BT in septic rats, especially preventing BT to distant organs, such as the liver and lung. Moreover, Enterococci spp. with high drug resistance and high pathogenicity translocated most after antibiotic treatment.

The Pharmacodynamics of Prolonged Infusion β-Lactams for the Treatment of Pseudomonas aeruginosa Infections: A Systematic Review

PURPOSE

Pseudomonas aeruginosa is a commonly isolated nosocomial pathogen for which treatment options are often limited for multidrug-resistant isolates. In addition to newer available antimicrobial agents active against P. aeruginosa, strategies such as extended (eg, prolonged or continuous) infusion have been suggested to optimize the pharmacokinetic and pharmacodynamic profiles of β-lactams. Literature regarding clinical outcomes for extended infusion β-lactams has been controversial; however, this use seems most beneficial in patients with severe illness. Prolonged infusion of β-lactams (eg, 3- to 4-hour infusion) can enhance the pharmacodynamic target attainment via increasing the amount of time throughout the dosing interval to which the free drug concentration remains above the MIC (minimum inhibitory concentration) of the organism (fT > MIC). This systematic review summarizes current literature related to the probability of target attainment (PTA) of various antipseudomonal β-lactam regimens administered as prolonged infusions in an effort to provide guidance in selecting optimal dosing regimens and infusion times for the treatment of P. aeruginosa infections.

METHODS

A literature search for all pertinent studies was performed by using the PubMed database (with no year limit) through March 31, 2019.

FINDINGS

Thirty-nine studies were included. Although many standard antipseudomonal β-lactam intermittent infusion regimens can provide adequate PTA against most susceptible isolates, prolonged infusion may enhance percent fT > MIC for organisms with higher MICs (eg, nonsusceptible) or patients with altered pharmacokinetic profiles (eg, obese, critically ill, those with febrile neutropenia).

IMPLICATIONS

Prolonged infusion β-lactam regimens can enhance PTA against nonsusceptible P. aeruginosa isolates and may provide a potential therapeutic option for multidrug-resistant infections. Before implementing prolonged infusion antipseudomonal β-lactams, institutions should consider the half-life of the antibiotic, local incidence of P. aeruginosa infections, antibiotic MIC distributions or MICs isolated from individual patients, individual patient characteristics that may alter pharmacokinetic variables, and PTA (eg, critically ill), as well as implementation challenges.

Thiostrepton Hijacks Pyoverdine Receptors To Inhibit Growth of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a biofilm-forming opportunistic pathogen and is intrinsically resistant to many antibiotics. In a high-throughput screen for molecules that modulate biofilm formation, we discovered that the thiopeptide antibiotic thiostrepton (TS), which is considered to be inactive against Gram-negative bacteria, stimulated P. aeruginosa biofilm formation in a dose-dependent manner. This phenotype is characteristic of exposure to antimicrobial compounds at subinhibitory concentrations, suggesting that TS was active against P. aeruginosa Supporting this observation, TS inhibited the growth of a panel of 96 multidrug-resistant (MDR) P. aeruginosa clinical isolates at low-micromolar concentrations. TS also had activity against Acinetobacter baumannii clinical isolates. The expression of Tsr, a 23S rRNA-modifying methyltransferase from TS producer Streptomyces azureus, in trans conferred TS resistance, confirming that the drug acted via its canonical mode of action, inhibition of ribosome function. The deletion of oligopeptide permease systems used by other peptide antibiotics for uptake failed to confer TS resistance. TS susceptibility was inversely proportional to iron availability, suggesting that TS exploits uptake pathways whose expression is increased under iron starvation. Consistent with this finding, TS activity against P. aeruginosa and A. baumannii was potentiated by the FDA-approved iron chelators deferiprone and deferasirox and by heat-inactivated serum. Screening of P. aeruginosa mutants for TS resistance revealed that it exploits pyoverdine receptors FpvA and FpvB to cross the outer membrane. We show that the biofilm stimulation phenotype can reveal cryptic subinhibitory antibiotic activity, and that TS has activity against select multidrug-resistant Gram-negative pathogens under iron-limited growth conditions, similar to those encountered at sites of infection.

Antibiotic resistance in Pseudomonas aeruginosa - Mechanisms, epidemiology and evolution

Antibiotics are powerful drugs used in the treatment of bacterial infections. The inappropriate use of these medicines has driven the dissemination of antibiotic resistance (AR) in most bacteria. Pseudomonas aeruginosa is an opportunistic pathogen commonly involved in environmental- and difficult-to-treat hospital-acquired infections. This species is frequently resistant to several antibiotics, being in the "critical" category of the WHO's priority pathogens list for research and development of new antibiotics. In addition to a remarkable intrinsic resistance to several antibiotics, P. aeruginosa can acquire resistance through chromosomal mutations and acquisition of AR genes. P. aeruginosa has one of the largest bacterial genomes and possesses a significant assortment of genes acquired by horizontal gene transfer (HGT), which are frequently localized within integrons and mobile genetic elements (MGEs), such as transposons, insertion sequences, genomic islands, phages, plasmids and integrative and conjugative elements (ICEs). This genomic diversity results in a non-clonal population structure, punctuated by specific clones that are associated with significant morbidity and mortality worldwide, the so-called high-risk clones. Acquisition of MGEs produces a fitness cost in the host, that can be eased over time by compensatory mutations during MGE-host coevolution. Even though plasmids and ICEs are important drivers of AR, the underlying evolutionary traits that promote this dissemination are poorly understood. In this review, we provide a comprehensive description of the main strategies involved in AR in P. aeruginosa and the leading drivers of HGT in this species. The most recently developed genomic tools that allowed a better understanding of the features contributing for the success of P. aeruginosa are discussed.

Prophylactic and therapeutic protection of human IgG purified from sera containing anti-exotoxin A titers against pneumonia caused by Pseudomonas aeruginosa

Antibodies are effective alternative tools to combat infections caused by Pseudomonas aeruginosa (PA), especially multi-drug-resistant PA. Thus, to solve the urgent need for an anti-PA antibody drug, we hypothesized that anti-PA intravenous immunoglobulins could be a practical attempt. Exotoxin A (ETA) is one of the most important factors for PA infection and is also a critical target for the development of immune interventions. In this study, a total of 320 sera were collected from healthy volunteers. The concentration of ETA-specific antibodies was determined by a Luminex-based assay and then purified by affinity chromatography. The purified IgGs were able to neutralize the cytotoxicity of ETA in vitro. We showed they had a prophylactic and therapeutic protective effect in PA pneumonia and ETA toxemia models. In addition, administration of nonspecific IgGs also provided partial protection. Collectively, our results provide additional evidence for IVIG-based treatment of infections caused by multi-drug-resistant PA and suggest that patients at high risk of PA pneumonia could be prophylactically treated with anti-ETA IgGs or even with nonspecific IgGs.

Compounds with capacity to quench the tyrosyl radical in Pseudomonas aeruginosa ribonucleotide reductase

Ribonucleotide reductase (RNR) has been extensively probed as a target enzyme in the search for selective antibiotics. Here we report on the mechanism of inhibition of nine compounds, serving as representative examples of three different inhibitor classes previously identified by us to efficiently inhibit RNR. The interaction between the inhibitors and Pseudomonas aeruginosa RNR was elucidated using a combination of electron paramagnetic resonance spectroscopy and thermal shift analysis. All nine inhibitors were found to efficiently quench the tyrosyl radical present in RNR, required for catalysis. Three different mechanisms of radical quenching were identified, and shown to depend on reduction potential of the assay solution and quaternary structure of the protein complex. These results form a good foundation for further development of P. aeruginosa selective antibiotics. Moreover, this study underscores the complex nature of RNR inhibition and the need for detailed spectroscopic studies to unravel the mechanism of RNR inhibitors.

Polymeric Composites with Silver (I) Cyanoximates Inhibit Biofilm Formation of Gram-Positive and Gram-Negative Bacteria

Biofilms are surface-associated microbial communities known for their increased resistance to antimicrobials and host factors. This resistance introduces a critical clinical challenge, particularly in cases associated with implants increasing the predisposition for bacterial infections. Preventing such infections requires the development of novel antimicrobials or compounds that enhance bactericidal effect of currently available antibiotics. We have synthesized and characterized twelve novel silver(I) cyanoximates designated as Ag(ACO), Ag(BCO), Ag(CCO), Ag(ECO), Ag(PiCO), Ag(PICO) (yellow and red polymorphs), Ag(BIHCO), Ag(BIMCO), Ag(BOCO), Ag(BTCO), Ag(MCO) and Ag(PiPCO). The compounds exhibit a remarkable resistance to high intensity visible light, UV radiation and heat and have poor solubility in water. All these compounds can be well incorporated into the light-curable acrylate polymeric composites that are currently used as dental fillers or adhesives of indwelling medical devices. A range of dry weight % from 0.5 to 5.0 of the compounds was tested in this study. To study the potential of these compounds in preventing planktonic and biofilm growth of bacteria, we selected two human pathogens (Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus) and Gram-positive environmental isolate Bacillus aryabhattai. Both planktonic and biofilm growth was abolished completely in the presence of 0.5% to 5% of the compounds. The most efficient inhibition was shown by Ag(PiCO), Ag(BIHCO) and Ag(BTCO). The inhibition of biofilm growth by Ag(PiCO)-yellow was confirmed by scanning electron microscopy (SEM). Application of Ag(BTCO) and Ag(PiCO)-red in combination with tobramycin, the antibiotic commonly used to treat P. aeruginosa infections, showed a significant synergistic effect. Finally, the inhibitory effect lasted for at least 120 h in P. aeruginosa and 36 h in S. aureus and B. aryabhattai. Overall, several silver(I) cyanoximates complexes efficiently prevent biofilm development of both Gram-negative and Gram-positive bacteria and present a particularly significant potential for applications against P. aeruginosa infections.

Newer β-Lactam/β-Lactamase inhibitor for multidrug-resistant gram-negative infections: Challenges, implications and surveillance strategy for India

Antimicrobial resistance (AMR) is a major public health concern across the globe, and it is increasing at an alarming rate. Multiple classes of antimicrobials have been used for the treatment of infectious diseases. Rise in the AMR limits its use and hence the prerequisite for the newer agents to combat drug resistance. Among the infections caused by Gram-negative organisms, beta-lactams are one of the most commonly used agents. However, the presence of diverse beta-lactamases hinders its use for therapy. To overcome these enzymes, beta-lactamase inhibitors are being discovered. The aim of this document is to address the burden of AMR in India and interventions to fight against this battle. This document addresses and summarises the following: The current scenario of AMR in India (antimicrobial susceptibility, resistance mechanisms and molecular epidemiology of common pathogens); contentious issues in the use of beta-lactam/beta-lactamase inhibitor as an carbapenem sparing agent; role of newer beta-lactam/beta-lactamase inhibitor agents with its appropriateness to Indian scenario and; the Indian Council of Medical Research interventions to combat drug resistance in terms of surveillance and infection control as a national response to AMR. This document evidences the need for improved national surveillance system and country-specific newer agents to fight against the AMR.

Slt, MltD, and MltG of Pseudomonas aeruginosa as Targets of Bulgecin A in Potentiation of β-Lactam Antibiotics

The interplay between the activities of lytic transglycosylases (LTs) and penicillin-binding proteins (PBPs) is critical for the health of the bacterial cell wall. Bulgecin A (a natural-product inhibitor of LTs) potentiates the activity of β-lactam antibiotics (inhibitors of PBPs), underscoring this intimate mechanistic interdependence. Bulgecin A in the presence of an appropriate β-lactam causes bulge deformation due to the formation of aberrant peptidoglycan at the division site of the bacterium. As Pseudomonas aeruginosa, a nefarious human pathogen, has 11 LT paralogs, the answer as to which LT activity correlates with β-lactam potentiation is important and is currently unknown. Growth of P. aeruginosa PAO1 strains harboring individual transposon-insertion mutants at each of the 11 genes for LTs, in the presence of the β-lactam antibiotic ceftazidime or meropenem, implicated the gene products of slt, mltD, and mltG (of the 11), in bulge formation and potentiation. Hence, the respective enzymes would be the targets of inhibition by bulgecin A, which was indeed documented. We further demonstrated by imaging in real time and by SEM that cell lysis occurs by the structural failure of this bulge. Upon removal of the β-lactam antibiotic prior to lysis, P. aeruginosa experiences delayed recovery from the elongation and bulge phenotype in the presence of bulgecin A. These observations argue for a collaborative role for the target LTs in the repair of the aberrant cell wall, the absence of activities of which in the presence of bulgecin A results in potentiation of the β-lactam antibiotic.

Mutations in gyrB play an important role in ciprofloxacin-resistant Pseudomonas aeruginosa

Purpose

To investigate the main molecular resistance mechanisms to fluoroquinolones (FQs) in Pseudomonas aeruginosa and also to investigate the effect of time and concentration on mutations in resistance genes.

Materials and methods

The clinical isolates of P. aeruginosa which are sensitive to ciprofloxacin (CIP) or levofloxacin (LEV) were collected. The isolates were incubated with different concentrations of CIP or LEV for 5 days and the minimal inhibitory concentrations (MICs) of CIP, LEV and ofloxacin (OFX) were measured. The MIC of FQs to P. aeruginosa was measured by the agar dilution method. FQ resistance determining regions of gyrA, gyrB, parC and parE were amplified by PCR, and mutations in four genes were explored using sequence analysis with the Snapgene software. The relative expression levels of two efflux pumps genes (mexA and mexE) were measured by quantitative reverse transcription PCR.

Results

A total of eleven isolates were collected from the Second Hospital of Shanxi Medical University. Amino acid alterations in gyrA and gyrB were mainly detected in resistant mutants, and the percentage of strains with amino acid alterations in gyrB was significantly higher than that in gyrA (P<0.001). MICs of strains with mutations both in gyrA and gyrB were not significantly higher than those of strains with mutations only in gyrB (P>0.05). No amino acid alterations were detected in genes of parC and parE. In both gyrA and gyrB, the number of amino acid alterations increased with incubation time prolonged and increased with increasing incubation concentration.

Conclusion

CIP was more competent than LEV in making P. aeruginosa resistant to in vitro selection. Mutations occurring in gyrB played an important role in FQ resistance of P. aeruginosa in vitro selection.

Current trends in the treatment of pneumonia due to multidrug-resistant Gram-negative bacteria

Pneumonia is one of the most common infections worldwide. Morbidity, mortality, and healthcare costs increase substantially when pneumonia is caused by multidrug-resistant Gram-negative bacteria (MDR-GNB). The ongoing spread of antimicrobial resistance has made treating MDR-GNB pneumonia increasingly difficult. Fortunately, there have been some recent additions to our antibiotic armamentarium in the US and Europe for MDR-GNB, along with several agents that are in advanced stages of development. In this article, we review the risk factors for and current management of MDR-GNB pneumonia as well as novel agents with activity against these important and challenging pathogens.

Postmortem microbiology sampling following death in hospital: an ESGFOR task force consensus statement

Postmortem microbiology (PMM) is a valuable tool in the identification of the cause of death and of factors contributory to death where death has been caused by infection. The value of PMM is dependent on careful autopsy planning, appropriate sampling, minimisation of postmortem bacterial translocation and avoidance of sample contamination. Interpretation of PMM results requires careful consideration in light of the clinical history, macroscopic findings and the histological appearances of the tissues. This consensus statement aims to highlight the importance of PMM in the hospital setting and to give microbiological and pathological advice on sampling in deaths occurring in hospital.

Measurement of ceftolozane and tazobactam concentrations in plasma by UHPLC-MS/MS. Clinical application in the management of difficult-to-treat osteoarticular infections

BACKGROUND

Ceftolozane, in combination with the β-lactamase inhibitor tazobactam, is a new option in the pipeline against multidrug-resistant Gram-negative bacilli. As for other β-lactam antibiotics, optimizing the use of ceftolozane-tazobactam is advisable, especially in difficult-to-treat infections. In this regard, therapeutic drug monitoring would be required to guide the treatment of ceftolozane-tazobactam. Thus, we aimed to develop and validate procedures based on UHPLC-MS/MS for measurement of ceftolozane and tazobactam plasma concentrations in clinical practice.

MATERIAL AND METHODS

Analyses were conducted using an Acquity® UPLC® integrated system coupled to an Acquity® TQD® tandem-quadrupole mass spectrometer. Ceftolozane, tazobactam and their internal standards (ceftazidime-D₅ and sulbactam) were detected by electrospray ionization mass spectrometry in positive and negative ion multiple reaction monitoring modes, using transitions of 667.2 → 199.3/139.0 and 551.9 → 467.9 for ceftolozane and ceftazidime-D₅, and 299.0 → 138/254.9 and 232.0 → 140.0 for tazobactam and sulbactam. Measurement procedures developed were used for guiding the treatment and adjusting daily dose of ceftolozane-tazobactam in patients with osteoarticular infections.

RESULTS

Coefficients of variation and absolute relative biases were <7.9% and 6.5% in all cases. The lower limit of quantification, linearity, normalized-recoveries, normalized-matrix effects and measurement uncertainties for ceftolozane were: 0.97 mg/L, (0.97-125) mg/L, ≤113.6%, ≤108.7%, and ≤ 18.7%, respectively; and for tazobactam: 1.04 mg/L, (1.04-125) mg/L, ≤103.6%, ≤101.9%, and ≤ 20.0%. No interferences and carry-over were observed. Patients plasma concentrations were higher than the recommended 3-4 times the minimal inhibitory concentrations.

CONCLUSIONS

Our measurement procedures are suitable for therapeutic drug monitoring of ceftolozane-tazobactam in patients with osteoarticular infections.

Calcium Phosphate Nanoparticles as Intrinsic Inorganic Antimicrobials: The Antibacterial Effect

Cheap and simple to make, calcium phosphate (CP), thanks to its unusual functional pleiotropy, belongs to the new wave of abundant and naturally accessible nanomaterials applicable as a means to various technological ends. It is used in a number of industries, including the biomedical, but its intrinsic antibacterial activity in the nanoparticle form has not been sufficiently explored to date. In this study, we report on this intrinsic antibacterial effect exhibited by two distinct CP phases: an amorphous CP (ACP) and hydroxyapatite (HAp). The effect is prominent against a number of regular bacterial species, including Staphylococcus aureus, Staphylococcus epidermis, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa, but also their multidrug-resistant (MDR) analogues. Although ACP and HAp displayed similar levels of activity against Gram-negative organisms, ACP proved to be more effective against the Gram-positive ones, with respect to which HAp was mostly inert, yet this trend became reversed for the MDR strains. In addition to the intrinsic antimicrobial effect of CP nanoparticles, we have also observed a synergistic effect between the nanoparticles and certain antibiotics. Both forms of CP were engaged in a synergistic relationship with a variety of concomitantly delivered antibiotics, including ampicillin, kanamycin, oxacillin, vancomycin, minocycline, erythromycin, linezolid, and clindamycin, and enabled even antibiotics completely ineffective against particular bacterial strains to significantly suppress their growth. This relationship was complex; depending on a particular CP phase, bacterial strain and antibiotic, the antibacterial activity (i) intensified proportionally to the nanoparticle concentration, (ii) plateaued immediately after the introduction of nanoparticles in minute amounts, or (iii) exhibited concentration-dependent minima due to stress-induced biofilm formation. These findings present grounds for the further optimization of CP properties and maximization of this intriguing effect, which could in the long run make this material comparable in activity to the inorganics of choice for this application, including silver, copper, or zinc oxide, while retaining its superb safety profile and positive eukaryotic versus prokaryotic cell selectivity.