Antimicrobial susceptibility among Gram-positive and Gram-negative isolates collected in Europe between 2004 and 2010

Staphylococcus aureus Bacteriophage 52 Endolysin Exhibits Anti-Biofilm and Broad Antibacterial Activity Against Gram-Positive Bacteria

Bacteriophage endolysins have been shown to hold great promise as new antibacterial agents for animal and human health in food preservation. In the present study, endolysin from Staphylococcus aureus subsp. aureus ATCC 27692-B1 bacteriophage 52 (LysSA52) was cloned, expressed, and characterized for its antimicrobial properties. Following DNA extraction from bacteriophage 52, a 1446-bp DNA fragment containing the endolysin gene (lysSA52) was obtained by PCR amplification and cloned into pET SUMO expression vector. The positive clone was validated by sequencing and open-reading frame analysis. The LysSA52 sequence shared high homology with staphylococcal phage endolysins of the SA12, SA13, and DSW2 phages and others. The cloned lysSA52 gene encoding 481 amino acids endolysin was expressed in Escherichia coli BL21 with a calculated molecular mass of 66 kDa (LysSA52). This recombinant endolysin LysSA52 exhibited lytic activity against 8 of 10 Gram-positive bacteria via agar spot-on lawn antimicrobial assay, including methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Streptococcus pneumonia, Streptococcus pyogenes, Enterococcus faecium, Enterococcus faecalis, and Bacillus atrophaeus. In addition, the 0.50 mg/mL, LysSA52 endolysins reduced about 60% of the biofilms of S. aureus and S. epidermidis established on a microtiter plate in 12 h treatment. The data from this study indicate that LysSA52 endolysin could be used as an antibacterial protein to prevent and treat infections caused by staphylococci and several other Gram-positive pathogenic bacteria irrespective of their antibiotic resistance.

Distribution and Antimicrobial Susceptibility of Gram-Positive and Gram-Negative Pathogens Isolated from Patients Hospitalized in a Tertiary Teaching Hospital in Southwestern China

Background: Bacteria are the most common causes of clinical infectious diseases. The distribution and antimicrobial resistance (AMR) rates of bacteria provide important guidelines for clinical antibacterial treatment; however, the information in this region is still missing. Objectives: This study aimed to evaluate the changes in the distribution and AMR rates of clinical isolates from inpatients. Methods: We conducted a retrospective cross-sectional analysis of the distribution and antimicrobial susceptibility of all non-duplicate Gram-negative bacterial (GNB) and Gram-positive bacterial (GPB) isolates collected from January 1, 2013, to December 31, 2018, in our hospital. Results: In total, 56,535 and 3,518 non-repetitive isolates were detected in the whole hospital and intensive care units (ICUs), respectively. The isolates included GPB (26.3% and 18.4%, respectively) and GNB (73.7% and 81.6%, respectively). The five dominant bacteria were the same in the whole hospital and ICUs, but Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii percentages were different. The detection rates of all isolates and five dominant bacteria were significantly different between the ICUs and the whole hospital (P < 0.05). The detection rate of extended-spectrum β-lactamase (ESBL)-E. coli (54.1%) was significantly higher than that of K. pneumoniae (26.1%). The detection rates of carbapenem-resistant (CR) and extensively drug-resistant (XDR)-A. baumannii were the highest in both the ICUs (87.1% and 21.8%, respectively) and the whole hospital (65.5% and 12.9%, respectively). The methicillin-resistant S. aureus (MRSA) detection rate was high (26.5%) but showed a significant decreasing trend (P < 0.05). The detection rates of ESBL and XDR-E. coli, CRAB, and XDR-S. aureus were significantly different between the ICUs and the whole hospital (P < 0.05). Gram-negative bacteria were highly susceptible to amikacin (> 90%) and tigecycline (> 98%). Staphylococcus aureus showed 100% susceptibility to vancomycin and linezolid. Acinetobacter baumannii had the highest resistance to imipenem (62.8%) and meropenem (64.0%). Except for A. baumannii and E. coli (P < 0.05), the AMR levels and the trends of the other isolates were similar between the ICUs and the whole hospital (P > 0.05). Conclusions: Currently, the appropriate antimicrobial agents in our hospital include amikacin and tigecycline for the treatment of GNB infections and vancomycin and linezolid for the treatment of GPB infections. Moreover, it is still necessary to monitor AMR in the ICUs and the whole hospital simultaneously.

Siderophore Cephalosporin Cefiderocol Utilizes Ferric Iron Transporter Systems for Antibacterial Activity against Pseudomonas aeruginosa

Cefiderocol (S-649266) is a novel parenteral siderophore cephalosporin conjugated with a catechol moiety at the third-position side chain. The in vitro activity of cefiderocol against Pseudomonas aeruginosa was enhanced under iron-depleted conditions, whereas that of ceftazidime was not affected. The monitoring of [thiazole-14C]cefiderocol revealed the increased intracellular accumulation of cefiderocol in P. aeruginosa cells incubated under iron-depleted conditions compared with those incubated under iron-sufficient conditions. Cefiderocol was shown to have potent chelating activity with ferric iron, and extracellular iron was efficiently transported into P. aeruginosa cells in the presence of cefiderocol as well as siderophores, while enhanced transport of extracellular ferric iron was not observed when one of the hydroxyl groups of the catechol moiety of cefiderocol was replaced with a methoxy group. We conclude that cefiderocol forms a chelating complex with iron, which is actively transported into P. aeruginosa cells via iron transporters, resulting in potent antibacterial activity of cefiderocol against P. aeruginosa.

Antimicrobial Susceptibility among European Gram-Negative and Gram-Positive Isolates Collected as Part of the Tigecycline Evaluation and Surveillance Trial (2004-2014)

Background: European centers (n = 226) involved in the Tigecycline Evaluation and Surveillance Trial (TEST, 2004-2014) submitted data and bacterial isolates. Methods: Minimal inhibitory concentrations and susceptibility were determined using Clinical and Laboratory Standards Institute methods and European Committee on Antimicrobial Susceptibility Testing breakpoints. Results: The rates of the following resistant pathogens increased from 2004 to 2014: extended-spectrum β-lactamase (ESBL)-positive Escherichia coli (from 8.9 to 16.9%), multidrug-resistant Acinetobacter baumannii complex (from 15.4 to 48.5%), and ESBL-positive Klebsiella pneumoniae (from 17.2 to 23.7%). The rate of methicillin-resistant Staphylococcus aureus was 27.5% in 2004 and 28.9% in 2014. Resistance to the carbapenems (imipenem and meropenem) was 37.4 and 14.5% for A. baumannii complex and Pseudomonas aeruginosa, respectively. Carbapenem resistance was ≤4.3% among the Enterobacteriaceae and 0.2% against Streptococcus pneumoniae. The resistance to tigecycline ranged between 7.4% against ESBL-producing K. pneumoniae and 0.0% against S. aureus.Conclusions: The carbapenems and tigecycline were active against Enterobacteriaceae. Agents with activity against A. baumannii complex and P. aeruginosa are limited. The carbapenems, tigecycline, linezolid, and vancomycin were active against Gram-positive organisms.

Antimicrobial susceptibility among important pathogens collected as part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) in Spain, 2004-2014

Here we report in vitro activity data from the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) for tigecycline and comparators against Gram-positive and Gram-negative organisms collected from 27 medical centres in Spain between 2004 and 2014. Minimum inhibitory concentrations (MICs) were determined according to the broth microdilution methodology of the Clinical and Laboratory Standards Institute (CLSI) and susceptibility were determined according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) interpretive criteria. Susceptibility was >97% for all antimicrobials tested against Enterococcus faecalis, and >98% of Enterococcus faecium tested were susceptible to tigecycline, linezolid and vancomycin. A total of 34.1% (1071/3143) of Staphylococcus aureus were meticillin-resistant S. aureus (MRSA), and all MRSA were susceptible to tigecycline and vancomycin. Among the Streptococcus pneumoniae, 5.2% (74/1430) were penicillin-resistant and all isolates were susceptible to linezolid and vancomycin. Among the Enterobacteriaceae, 17.1% (542/3167) of Escherichia coli, 2.8% (19/682) of Klebsiella oxytoca and 19.0% (441/2327) of Klebsiella pneumoniae isolates produced extend-spectrum β-lactamases (ESBLs). Against ESBL-producing E. coli and K. pneumoniae, susceptibility was highest for meropenem, amikacin and tigecycline with rates of >92% and >80%, respectively. Among the Acinetobacter baumannii, susceptibility ranged between 23.5% for levofloxacin and 51.4% for amikacin, and an MIC90 of 2mg/L was observed for tigecycline. In conclusion, monitoring of antimicrobial susceptibility among organisms such as S. aureus, Enterobacteriaceae and A. baumannii is of continuing importance as a guide to clinicians. Depending on the organism to be treated, carbapenems, linezolid, vancomycin and tigecycline continue to be active in Spain.