Quorum sensing (QS) is a communication mechanism between bacteria that allows specific processes to be controlled, such as biofilm formation, virulence factor expression, production of secondary ...metabolites and stress adaptation mechanisms such as bacterial competition systems including secretion systems (SS). These SS have an important role in bacterial communication. SS are ubiquitous; they are present in both Gram-negative and Gram-positive bacteria and in
sp. To date, 8 types of SS have been described (T1SS, T2SS, T3SS, T4SS, T5SS, T6SS, T7SS, and T9SS). They have global functions such as the transport of proteases, lipases, adhesins, heme-binding proteins, and amidases, and specific functions such as the synthesis of proteins in host cells, adaptation to the environment, the secretion of effectors to establish an infectious niche, transfer, absorption and release of DNA, translocation of effector proteins or DNA and autotransporter secretion. All of these functions can contribute to virulence and pathogenesis. In this review, we describe the known types of SS and discuss the ones that have been shown to be regulated by QS. Due to the large amount of information about this topic in some pathogens, we focus mainly on
and
spp.
Detection and monitoring of antimicrobial resistance are two pillars on which clinical microbiology will be based in the coming decades. The implementation of certain technologies such as whole ...genome sequencing (WGS) or mass spectrometry and the creation of national and international databases that include and gather data on antimicrobial resistance from around the world has allowed the application of bioinformatics in the study of antimicrobial resistance in microorganisms involved in human pathology.
To characterize the antimicrobial susceptibility, molecular epidemiology and carbapenem resistance mechanisms in Pseudomonas aeruginosa isolates recovered from respiratory tract samples from patients ...with ventilator-associated pneumonia enrolled in the MagicBullet clinical trial.
Isolates were collected from 53 patients from 12 hospitals in Spain, Italy and Greece. Susceptibility was determined using broth microdilution and Etest. MALDI-TOF MS was used to detect carbapenemase activity and carbapenemases were identified by PCR and sequencing. Molecular epidemiology was investigated using PFGE and MLST.
Of the 53 isolates, 2 (3.8%) were considered pandrug resistant (PDR), 19 (35.8%) were XDR and 16 (30.2%) were MDR. Most (88.9%) of the isolates from Greece were MDR, XDR or PDR, whereas fewer of the isolates from Spain (33.3%) and Italy (43.5%) showed antibiotic resistance. Three Greek isolates were resistant to colistin. Overall, the rates of resistance of P. aeruginosa isolates to imipenem, ciprofloxacin, ceftolozane/tazobactam and ceftazidime/avibactam were 64.1%, 54.7%, 22.6% and 24.5%, respectively. All isolates resistant to ceftolozane/tazobactam and ceftazidime/avibactam (Greece, n = 10; and Italy, n = 2) carried blaVIM-2. Spanish isolates were susceptible to the new drug combinations. Forty-eight restriction patterns and 27 STs were documented. Sixty percent of isolates belonged to six STs, including the high-risk clones ST-111, ST-175 and ST-235.
MDR/XDR isolates were highly prevalent, particularly in Greece. The most effective antibiotic against P. aeruginosa was colistin, followed by ceftolozane/tazobactam and ceftazidime/avibactam. blaVIM-2 is associated with resistance to ceftolozane/tazobactam and ceftazidime/avibactam, and related to highly resistant phenotypes. ST-111 was the most frequent and disseminated clone and the clonal diversity was lower in XDR and PDR strains.
The emergence of multidrug resistant (MDR) pathogenic bacteria is jeopardizing the value of antimicrobials, which had previously changed the course of medical science. In this study, we identified ...endolysins ElyA1 and ElyA2 (GH108-PG3 family), present in the genome of bacteriophages Ab1051Φ and Ab1052Φ, respectively. The muralytic activity of these endolysins against MDR clinical isolates (Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae) was tested using the turbidity reduction assay. Minimal inhibitory concentrations (MICs) of endolysin, colistin and a combination of endolysin and colistin were determined, and the antimicrobial activity of each treatment was confirmed by time kill curves. Endolysin ElyA1 displayed activity against all 25 strains of A. baumannii and P. aeruginosa tested and against 13 out of 17 strains of K. pneumoniae. Endolysin ElyA2 did not display any such activity. The combined antimicrobial activity of colistin and ElyA1 yielded a reduction in the colistin MIC for all strains studied, except K. pneumoniae. These results were confirmed in vivo in G. mellonella survival assays and in murine skin and lung infection models. In conclusion, combining colistin (1/4 MIC) with the new endolysin ElyA1 (350 µg) enhanced the bactericidal activity of colistin in both in vitro and in vivo studies. This will potentially enable reduction of the dose of colistin used in clinical practice.
Novel β-lactam-β-lactamase inhibitor combinations currently approved for clinical use are poorly active against metallo-β-lactamase (MBL)-producing strains. We evaluated the
activity of ...cefepime-taniborbactam (FTB formerly cefepime-VNRX-5133) and comparator agents against carbapenemase-producing
(
= 247) and carbapenem-resistant Pseudomonas species (
= 170) clinical isolates prospectively collected from different clinical origins in patients admitted to 8 Spanish hospitals. FTB was the most active agent in both
(97.6% MIC
, ≤8/4 mg/L) and Pseudomonas (67.1% MIC
, ≤8/4 mg/L) populations. The MIC
was >8 mg/L in 6/247 (2.4%)
isolates (3 KPC-producing Klebsiella pneumoniae isolates, 1 VIM-producing Enterobacter cloacae isolate, 1 IMP-producing E. cloacae isolate, and 1 NDM-producing Escherichia coli isolate) and in 56/170 (32.9%) Pseudomonas isolates, 19 of them carbapenemase producers (15 producers of VIM, 2 of GES, 1 of GES+VIM, and 1 of GES+KPC). Against the
isolates with meropenem MICs of >2 mg/L (138/247), FTB was the most active agent against both serine-β-lactamases (107/138) and MBL producers (31/138) (97.2 and 93.5% MIC
, ≤8/4 mg/L, respectively), whereas the activity of comparators was reduced, particularly against the MBL producers (ceftazidime-avibactam, 94.4 and 12.9%, meropenem-vaborbactam, 85.0 and 64.5%, imipenem-relebactam, 76.6 and 9.7%, ceftolozane-tazobactam, 1.9 and 0%, and piperacillin-tazobactam, 0 and 0%, respectively). Among the meropenem-resistant Pseudomonas isolates (163/170; MIC, >2 mg/L), the activities of FTB against serine-β-lactamase (35/163) and MBL (43/163) producers were 88.6 and 65.1%, respectively, whereas the susceptibilities of comparators were as follows: ceftazidime-avibactam, 88.5 and 16.0%, meropenem-vaborbactam, 8.5 and 7.0%, imipenem-relebactam, 2.9 and 2.3%, ceftolozane-tazobactam, 0 and 2.3%, and piperacillin-tazobactam, 0 and 0%, respectively. Microbiological results suggest FTB as a potential therapeutic option in patients infected with carbapenemase-producing
and carbapenem-resistant Pseudomonas isolates, including MBL producers.
Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been successfully applied in recent years for first-line identification of pathogens in clinical ...microbiology because it is simple to use, rapid, and accurate and has economic benefits in hospital management. The range of clinical applications of MALDI-TOF MS for bacterial isolates is increasing constantly, from species identification to the two most promising applications in the near future: detection of antimicrobial resistance and strain typing for epidemiological studies. The aim of this review is to outline the contribution of previous MALDI-TOF MS studies in relation to detection of antimicrobial resistance and to discuss potential future challenges in this field. Three main approaches are ready (or almost ready) for clinical use, including the detection of antibiotic modifications due to the enzymatic activity of bacteria, the detection of antimicrobial resistance by analysis of the peak patterns of bacteria or mass peak profiles, and the detection of resistance by semiquantification of bacterial growth in the presence of a given antibiotic. This review provides an expert guide for MALDI-TOF MS users to new approaches in the field of antimicrobial resistance detection, especially possible applications as a routine diagnostic tool in microbiology laboratories.
Klebsiella pneumoniae is an opportunistic Gram-negative pathogen that employs different strategies (resistance and persistence) to counteract antibiotic treatments. This study aimed to search for new ...means of combatting imipenem-resistant and persister strains of K. pneumoniae by repurposing the anticancer drug mitomycin C as an antimicrobial agent and by combining the drug and the conventional antibiotic imipenem with the lytic phage vB_KpnM-VAC13. Several clinical K. pneumoniae isolates were characterized, and an imipenem-resistant isolate (harboring OXA-245 β-lactamase) and a persister isolate were selected for study. The mitomycin C and imipenem MICs for both isolates were determined by the broth microdilution method. Time-kill curve data were obtained by optical density at 600 nm (OD
) measurement and CFU enumeration in the presence of each drug alone and with the phage. The frequency of occurrence of mutants resistant to each drug and the combinations was also calculated, and the efficacy of the combination treatments was evaluated using an
infection model (Galleria mellonella). The lytic phage vB_KpnM-VAC13 and mitomycin C had synergistic effects on imipenem-resistant and persister isolates, both
and
The phage-imipenem combination successfully killed the persisters but not the imipenem-resistant isolate harboring OXA-245 β-lactamase. Interestingly, the combinations decreased the emergence of
resistant mutants of both isolates. Combinations of the lytic phage vB_KpnM-VAC13 with mitomycin C and imipenem were effective against the persister K. pneumoniae isolate. The lytic phage-mitomycin C combination was also effective against imipenem-resistant K. pneumoniae strains harboring OXA-245 β-lactamase.
Proteomic studies have improved our understanding of the microbial world. The most recent advances in this field have helped us to explore aspects beyond genomics. For example, by studying proteins ...and their regulation, researchers now understand how some pathogenic bacteria have adapted to the lethal actions of antibiotics. Proteomics has also advanced our knowledge of mechanisms of bacterial virulence and some important aspects of how bacteria interact with human cells and, thus, of the pathogenesis of infectious diseases. This review article addresses these issues in some of the most important human pathogens. It also reports some applications of Matrix-Assisted Laser Desorption/Ionization-Time-Of-Flight (MALDI-TOF) mass spectrometry that may be important for the diagnosis of bacterial resistance in clinical laboratories in the future. The reported advances will enable new diagnostic and therapeutic strategies to be developed in the fight against some of the most lethal bacteria affecting humans.
Antimicrobial resistance constitutes one of the major threats regarding pathogenic microorganisms. Gram-negative pathogens, such as Enterobacteriaceae (specially those producing extended-spectrum ...beta-lactamases), Pseudomonas aeruginosa, and Acinetobacter baumannii have acquired an important role in hospital infections, which is of particular concern because of the associated broad spectrum of antibiotic resistance. beta-Lactam antibiotics are considered the most successful antimicrobial agents since the beginning of the antibiotic era. Soon after the introduction of penicillin, microorganisms able to destroy this beta-lactam antibiotic were reported, thus emphasizing the facility of pathogenic microorganisms to develop beta-lactam resistance. In Gram-negative pathogens, beta-lactamase production is the main mechanism involved in acquired beta-lactam resistance. Four classes of beta-lactamases have been described: A, B, C, and D. Classes A, C, and D are enzymes with a serine moiety in the active centre that catalyzes hydrolysis of the beta -lactam ring through an acyl-intermediate of serine, whereas the class B enzymes require a metal cofactor (e.g. zinc in the natural form) to function, and for this reason, they are also referred to as metallo- beta-lactamases (MBLs). To overcome beta-lactamase-mediated resistance, a combination of beta-lactam and a beta-lactamase inhibitor, which protects the beta-lactam antibiotic from the activity of the beta-lactamase, has been widely used in the treatment of human infections. Although there are some very successful combinations of beta-lactams and beta-lactamase inhibitors, most of the inhibitors act against class A beta-lactamases and remain ineffective against class B, C, and D beta-lactamases. This review constitutes an update of the current status and knowledge regarding class A to D beta-lactamase inhibitors, as well as a summary of the drug discovery strategy currently used to identify new beta-lactamase inhibitors, mainly based on the knowledge of crystal structure of beta-lactamase enzymes.
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