Community-acquired Strains Research Articles

Alkyl Pyridinol Compounds Exhibit Antimicrobial Effects against Gram-Positive Bacteria.

Background/Objectives. The rise of antibiotic-resistant pathogens represents a significant global challenge in infectious disease control, which is amplified by the decline in the discovery of novel antibiotics. Staphylococcus aureus continues to be a highly significant pathogen, causing infections in multiple organs and tissues in both healthcare institutions and community settings. The bacterium has become increasingly resistant to all available antibiotics. Consequently, there is an urgent need for novel small molecules that inhibit the growth or impair the survival of bacterial pathogens. Given their large structural and chemical diversity, as well as often unique mechanisms of action, natural products represent an excellent avenue for the discovery and development of novel antimicrobial treatments. Anaephene A and B are two such naturally occurring compounds with significant antimicrobial activity against Gram-positive bacteria. Here, we report the rapid syntheses and biological characterization of five novel anaephene derivatives, which display low cytotoxicity against mammalian cells but potent antibacterial activity against various S. aureus strains, including methicillin-resistant S. aureus (MRSA) and the multi-drug-resistant community-acquired strain USA300LAC. Methods. A Sonogashira cross-coupling reaction served as the key step for the synthesis of the alkyl pyridinol products. Results/Conclusions. Using the compound JC-01-074, which displays bactericidal activity already at low concentrations (MIC: 16 μg/mL), we provide evidence that alkyl pyridinols target actively growing and biofilm-forming cells and show that these compounds cause disruption and deformation of the staphylococcal membrane, indicating a membrane-associated mechanism of action.

Whole-Genome Analysis of the Influenza A(H1N1)pdm09 Viruses Isolated from Influenza-like Illness Outpatients in Myanmar and Community-Acquired Oseltamivir-Resistant Strains Present from 2015 to 2019.

In this study, we describe the genetic characteristics of influenza A(H1N1)pdm09 strains detected in Myanmar from 2015 to 2019. Whole genomes from 60 A(H1N1)pdm09 virus isolates were amplified using real-time polymerase chain reaction and successfully sequenced using the Illumina iSeq100 platforms. Eight individual phylogenetic trees were retrieved for each segment along with those of the World Health Organization (WHO)-recommended Southern Hemisphere vaccine strains for the respective years. A(H1N1)pdm09 viruses from 2015 were found to belong to clade 6B, those from 2016 to 6B.1, 2017 to 6B.1A, and 2019 to 6B.1A.5a, and were genetically distinct from the Southern Hemisphere vaccine strains for the respective seasons, A/California/7/2009 and A/Michigan/45/2015. We observed one virus with intra-subtype reassortment, collected in the 2015 season. Importantly, three viruses possessed the H275Y substitution in the neuraminidase protein, appearing to be community-acquired without the prior administration of neuraminidase inhibitors. These viruses exhibited highly reduced susceptibility to oseltamivir and peramivir. This study demonstrates the importance of monitoring genetic variations in influenza viruses that will contribute to the selection of global influenza vaccines.

Understanding bacterial diversity, infection dynamics, prevention of antibiotic resistance: an integrated study in an Algerian hospital context.

Bacterial infections, particularly bacteremia, urinary tract infections (UTIs), and pus infections, remain among hospitals' most worrying medical problems. This study aimed to explore bacterial diversity, infection dynamics, and antibiotic resistance profiles of bacterial isolates. We analyzed data from 1750 outpatients and 920 inpatients, of whom 1.6% and 8.47% respectively had various bacterial infections. The analysis revealed that UTIs were the most prevalent at 41.01%, particularly affecting women. UTIs also showed a distinct distribution across admission departments, notably in emergency (23.07%) and pediatric (14.10%) units. The most frequently isolated microorganisms were Escherichia coli (E. coli), followed by Klebsiella ornithinolytica. Skin infections followed UTIs, accounting for 35.88% of cases, more prevalent in men, with Staphylococcus aureus (S. aureus) being the primary pathogen (57%). Gram-negative bacteria (GNB) like E. coli and Pseudomonas aeruginosa contributed significantly to skin infections (43%). Bacteremia cases constituted 11.52% of bacterial infections, predominantly affecting women (67%) and linked to GNB (78%). A comparative study of antibiotic susceptibility profiles revealed more pronounced resistance in GNB strains isolated from inpatients, particularly to antibiotics such as Amoxicillin/clavulanic acid, Tetracyclin, Gentamicin, Chloramphenicol, and Ampicillin. In contrast, strains from ambulatory patients showed greater resistance to Colistin. Gram-positive bacteria from hospitalized patients showed higher resistance to quinolones and cephalosporins, while ambulatory strains showed high resistance to aminoglycosides, macrolides, fluoroquinolones, and penicillin. Furthermore, these analyses identified the most effective antibiotics for the empirical treatment of both community-acquired and nosocomial infections. Ciprofloxacin, aztreonam, and amikacin exhibited low resistance rates among GNB, with gentamicin and chloramphenicol being particularly effective for community-acquired strains. For S. aureus, ciprofloxacin, rifampicin, and cefoxitin were especially effective, with vancomycin showing high efficacy against community-acquired isolates and fosfomycin and chloramphenicol being effective for hospital-acquired strains. These results are essential for guiding antibiotic therapy and improving clinical outcomes, thus contributing to precision medicine and antimicrobial stewardship efforts.

Emergence of novel hypervirulent Acinetobacter baumannii strain and herpes simplex type 1 virus in a case of community-acquired pneumonia in China

BackgroundA. baumannii is an important and common clinical pathogen, especially in the intensive care unit (ICU). This study aimed to characterize one hypervirulent A. baumannii strain in a patient with community-acquired pneumonia and herpes simplex type 1 virus infection. MethodsMinimum inhibitory concentrations (MICs) were determined using the Kirby-Bauer (K-B) and broth microdilution methods. Galleria mellonella infection model experiment was conducted. Whole-genome sequencing (WGS) was performed using the Illumina and Nanopore platforms. The resistance and virulence determinants were identified using the ABRicate program with ResFinder and the VFDB database. The capsular polysaccharide locus (K locus) and lipooligosaccharide outer core locus (OC locus) were identified using Kleborate with Kaptive. Phylogenetic analyses were conducted using the BacWGSTdb server. ResultsA. baumannii XH2146 strain belongs to ST10Pas and ST447Oxf. The strain was resistant to cefazolin, ciprofloxacin, and trimethoprim/sulfamethoxazole (TMP-SMX). Bautype and Kaptive analyses showed that XH2146 contains OCL2 and KL49. WGS analysis revealed that the strain harbored blaADC-76, blaOXA-68, ant(3′’)-IIa, tet(B), and sul2. Notably, tet(B) and sul2, both were located within a 114,700-bp plasmid (designated pXH2146–1). Virulence assay revealed A. baumannii XH2146 possessed higher virulence than A. baumannii AB5075 at 12 h. Comparative genomic analysis showed that A. baumannii ST447 strains were mainly isolated from the USA and exhibited a relatively close genetic relationship. Importantly, 11 strains were observed to carry blaOXA-58; blaOXA-23 was identified in 11 isolates and three ST447 A. baumannii strains harbored blaNDM-1. ConclusionsEarly detection of community-acquired hypervirulent Acinetobacter baumannii strains is recommended to prevent their extensive spread in hospitals.

Detection of mecA Genes in Hospital-Acquired MRSA and SOSA Strains Associated with Biofilm Formation.

Methicillin-resistant (MR) Staphylococcus aureus (SA) and others, except for Staphylococcus aureus (SOSA), are common in healthcare-associated infections. SOSA encompass largely coagulase-negative staphylococci, including coagulase-positive staphylococcal species. Biofilm formation is encoded by the icaADBC operon and is involved in virulence. mecA encodes an additional penicillin-binding protein (PBP), PBP2a, that avoids the arrival of β-lactams at the target, found in the staphylococcal cassette chromosome mec (SCCmec). This work aims to detect mecA, the bap gene, the icaADBC operon, and types of SCCmec associated to biofilm in MRSA and SOSA strains. A total of 46% (37/80) of the strains were S. aureus, 44% (35/80) S. epidermidis, 5% (4/80) S. haemolyticus, 2.5% (2/80) S. hominis, 1.25% (1/80) S. intermedius, and 1.25% (1/80) S. saprophyticus. A total of 85% were MR, of which 95.5% showed mecA and 86.7% β-lactamase producers; thus, Staphylococcus may have more than one resistance mechanism. Healthcare-associated infection strains codified type I-III genes of SCCmec; types IV and V were associated to community-acquired strains (CA). Type II prevailed in MRSA mecA strains and type II and III in MRSOSA (methicillin-resistant staphylococci other than Staphylococcus aureus). The operon icaADBC was found in 24% of SA and 14% of SOSA; probably the arrangement of the operon, fork formation, and mutations influenced the variation. Methicillin resistance was mainly mediated by the mecA gene; however, there may be other mechanisms that also participate, since biofilm production is related to genes of the icaADBC operon and methicillin resistance was not associated with biofilm production. Therefore, it is necessary to strengthen surveillance to prevent the spread of these outbreaks both in the nosocomial environment and in the community.

Antibiotic Susceptibility Pattern of Nosocomial and Community-Acquired Pseudomonas aeruginosa in Isfahan: A Prospective Multicenter Study

Background: Pseudomonas aeruginosa is a ubiquitous bacillus responsible for severe infections in inpatients, especially nosocomial and intensive care unit (ICU) infections. Objectives: This study aimed to determine the antibiotic susceptibility of clinical isolates from inpatients in three referral hospitals in Isfahan, Iran. Methods: Standard tests identified the organism and antibiotic susceptibility testing. Stratification was performed by place of infection (community, hospital), admission ward (ICU, non-ICU), and age group (< 20 versus > 20 years). Results: Pseudomonas aeruginosa showed high susceptibility to colistin (100%) and amikacin (81.8%) followed by tobramycin (69.2%), ciprofloxacin (68.5%), meropenem (67.2%), cefepime (65.7%), ceftazidime (64.3%), and imipenem (63.3%). Community-acquired strains were significantly more susceptible to meropenem (81.6%), ciprofloxacin (77.1%), cefepime (77.1%), imipenem (74.3%), and ceftazidime (72.2%) than nosocomial strains. Non-ICU isolates were more susceptible to carbapenems. Pseudomonas aeruginosa isolates had higher antibiotic susceptibility in less than 20 years. Conclusions: Based on the results, a combination of colistin and amikacin would be appropriate for the empiric treatment of suspected P. aeruginosa infections in severe cases, nosocomial infections, or patients admitted to ICU. Ceftazidime, cefepime, ciprofloxacin, meropenem, or imipenem would be suitable for mild to moderate infections, especially in community-acquired infections.

Staphylococcal scalded skin syndrome in neonate: Another face of CA-MRSA.

Staphylococcal scalded skin syndrome (SSSS), also known as Ritter's disease, in its severe form occurs predominantly in infants and children. It is caused by infection with group II (often phage group 71) Staphylococcus aureus. The foci of infection include nasopharynx, less commonly umbilicus, urinary tract, superficial abrasion, conjunctivae, and blood. Staphylococci are non-motile, non-spore-forming, catalase-positive, gram-positive cocci that appear predominantly as grape-like clusters. Although this organism is frequently a part of normal human microbial flora, it can cause significant opportunistic infections under certain conditions such as when extremes of age groups are involved, the presence of indwelling medical devices, and intravenous (iv) drug abuse. Staphylococcus aureus may cause a variety of infectious manifestations ranging from relatively benign skin infections to life-threatening systemic illnesses. SSSS caused by S. aureus strains produces exfoliative toxins which result in the development of blisters, erythema, and desquamation. Here, we present a case of an 11-day-old neonate who was diagnosed with SSSS. The causative agent responsible for this syndrome was identified as methicillin-resistant Staphylococcus aureus (MRSA). The molecular characterization of the gene Panton-Valentine leukocidin (PVL) was done by polymerase chain reaction (PCR) and was detected positive for PVL which is a distinctive virulence factor seen almost in all of the community-acquired MRSA strains. The patient was discharged after parenteral clindamycin therapy with almost complete resolution of symptoms.

Characterization of community-acquired Clostridioides difficile strains in Israel, 2020-2022.

The prevalence of community-acquired Clostridioides difficile infection (CA-CDI) has been rising, due to changes in antibiotics prescribing practices, emergence of hypervirulent strains and improved diagnostics. This study explored CA-CDI epidemiology by examining strain diversity and virulence factors of CA-CDI isolates collected across several geographical regions in Israel. Stool samples of 126 CA-CDI patients were subjected to PCR and an immunoassay to identify toxin genes and proteins, respectively. Toxin loci PaLoc and PaCdt were detected by whole-genome sequencing (WGS). Biofilm production was assessed by crystal violet-based assay. Minimum inhibitory concentration was determined using the Etest technique or agar dilution. WGS and multi-locus sequence typing (MLST) were used to classify strains and investigate genetic diversity. Sequence types (ST) 2 (17, 13.5%), ST42 (13, 10.3%), ST104 (10, 8%) and ST11 (9, 7.1%) were the most common. All (117, 92.8%) but ST11 belonged to Clade 1. No associations were found between ST and gender, geographic area or antibiotic susceptibility. Although all strains harbored toxins genes, 34 (27%) produced toxin A only, and 54 (42.9%) strains produced toxin B only; 38 (30.2%) produced both toxins. Most isolates were biofilm-producers (118, 93.6%), primarily weak producers (83/118, 70.3%). ST was significantly associated with both biofilm and toxin production. C. difficile isolates in Israel community exhibit high ST diversity, with no dominant strain. Other factors may influence the clinical outcomes of CDI such as toxin production, antibiotic resistance and biofilm production. Further studies are needed to better understand the dynamics and influence of these factors on CA-CDI.

Comparative Analysis of MRSA Isolation, Biofilm Formation, and Molecular Characteristics: Hospital-Acquired Versus Community-Acquired Strains

The current study was to look into the molecular characterisation and biofilm development of MRSA in patients who visited the Khyber Teaching Hospital, Hayatabad Medical Complex, and Lady Reading Hospital in Peshawar. Antibiotic susceptibility tests identify Methicillin-resistant Staphylococcus aureus in confirmed isolates of S. aureus. PCR was used to identify a gene, which proved that the MRSA isolates were real. HA- and CA-MRSA were distinguished by SCC mec typing. The microtiter plate assay was employed to look for signs of biofilm formation. 133 (82.60%) of the 161 samples that were positive for S. aureus. Of them, 32 (19.87%) had MSSA isolates, 28 (17.39%) were culture-negative, and 101 (62.73%) were determined to carry MRSA. To confirm all positive isolates one more time, Mec A gene analysis was performed. Twenty-one (20.79%) of the eighty (79.20%) confirmed isolates were classified as undistinguishable MRSA isolates, twenty-six (32.5%) as HA-MRSA isolates, and fifty-five (67.5%) as CA-MRSA isolates.

Discovery of the novel auxiliary factor for β-lactam resistance BlrA in community-acquired methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important human pathogens that cause a variety of infections in community and hospital settings. This organism displays high levels of resistance to β-lactam antibiotics and this principally occurs due to the production of β-lactamase and the penicillin binding protein PBP2a encoded by mecA gene. Furthermore, additional mechanisms, such as auxiliary factors, significantly contribute to β-lactam resistance. However, the function of most of these factors is still unknown.
 Recently, in our laboratory, the novel auxiliary factor gene blrA was initially identified by transposon mutagenesis in the community-acquired MRSA strain JE2. Next, the transposon mutation was transduced to the community-acquired MRSA strain MW2, resulting in the formation of a transposon mutant for blrA (blrA::ermB), denoted as MW2A. Initially, our results suggested that MW2A is more susceptible to oxacillin than the MW2 wild-type. Then, we performed the Minimum Inhibitory Concentration (MIC) method for the β-lactam antibiotics: oxacillin, cefoxitin, cephradine, ceftazidime, cefaclor and imipenem. MW2A exhibited a two-fold reduction for all tested β-lactam antibiotics compared to the MRSA wild-type strain MW2. Additionally, no phenotypical changes were observed after performing PBP2a latex agglutination test and phage spot assay. Finally, using DeepTMHMM we show that BlrA is likely to act intracellularly, which is typical of auxiliary factors.
 In this study, we show that BlrA is clearly involved in β-lactam resistance, but does not affect the expression of the gene mecA or the structure of the wall teichoic acids. Furthermore, we propose that that BlrA acts as an auxiliary factor and is activated in response to antimicrobial stress.

417 A CTS Team Approach to Developing an Effective Vaccine for Non-Typhoidal Salmonella

OBJECTIVES/GOALS: Non-Typhoidal Salmonella causes over 95 million infections globally each year, and no effective vaccine exists to combat infections in humans. The goal of this study is to determine the immune protection provided by a novel extracellular vesicle (EV)-based vaccine generated using lab-strain Salmonella against wastewater-derived Salmonella. METHODS/STUDY POPULATION: We isolated Non-Typhoidal Salmonella (NTS) from raw influent wastewater samples collected from two wastewater reclamation facilities (WRF) in Gainesville, FL. Whole genome sequencing was performed on each isolate and compared to sequences of clinically-derived isolates in FL during our study period to identify a clinical and subclinical isolate for assessing EV based vaccine protection. Mouse serum and stool samples were collected from a cohort of EV-vaccinated mice. Surrogates of protection against Salmonella used anti-Salmonella IgA in the feces of these mice, and anti-Salmonella IgG in serum of the mice, by using ELISAs coated with whole cell lysate collected from the two wastewater-derived isolates. RESULTS/ANTICIPATED RESULTS: We have previously shown that an EV vaccine provides protection against Salmonella enterica Serovar Typhimurium, the serovar used in the generation of the EV vaccine. We anticipate that the EV vaccine generates additional protection against the community-acquired strains, which will be characterized by increases in fecal IgA and serum IgG against two community Salmonella isolates that is similar to responses against the serovar used to generate the EV vaccine (Typhimurium). DISCUSSION/SIGNIFICANCE: This study will improve the translation of our vaccine studies by demonstrating the efficacy of our novel EV vaccine against circulating Salmonella isolates.

Bacteria-mediated synthesis of silver nanoparticles under photo-irradiation and their efficacy against methicillin-resistant Staphylococcus aureus

ABSTRACT Over the last few decades, morbidity and mortality rates from infectious diseases have increased due to antibiotic resistance. Community-acquired and nosocomial-related methicillin-resistant bacterial strains are proliferating, which makes the discovery of new antibiotics and the search for new approaches to fight pathogenic bacteria an urgent task. One of the new promising classes of antimicrobials is silver nanoparticles (AgNPs). The goal of this study was to investigate the bacteria-mediated synthesis of AgNPs and evaluate their antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Indigenous bacteria from soil samples from Multan (Pakistan) were isolated and three strains – Klebsiella spp., Citrobacter freundii, and Bacillus cereus – were selected for the synthesis of AgNPs under photo-irradiation. The biosynthesis of AgNPs was confirmed by UV-visible spectroscopy. The AgNPs obtained in our experiments showed strong antibacterial activity against MRSA isolated from patients with community-acquired skin infections (from the dermatology ward of Jinnah Hospital Lahore) with 15 mm to 25 mm zones of inhibition (ZOI) according to the well diffusion method. The results of this project showed that microbial reduction of AgNO3 under photo-irradiation produces AgNPs that are highly active against MRSA.

Characterisation of Methicillin-Resistant Staphylococcus aureus from Alexandria, Egypt.

The present study aims to characterise clinical MRSA isolates from a tertiary care centre in Egypt's second-largest city, Alexandria. Thirty isolates collected in 2020 were genotypically characterised by microarray to detect their resistance and virulence genes and assign them to clonal complexes (CC) and strains. Isolates belonged to 11 different CCs and 14 different strains. CC15-MRSA-[V+fus] (n = 6), CC1-MRSA-[V+fus+tir+ccrA/B-1] (PVL+) (n = 5) as well as CC1-MRSA-[V+fus+tir+ccrA/B-1] and CC1153-MRSA-[V+fus] (PVL+) (both with n = 3) were the most common strains. Most isolates (83%) harboured variant or composite SCCmec V or VI elements that included the fusidic acid resistance gene fusC. The SCCmec [V+fus+tir+ccrA/B-1] element of one of the CC1 isolates was sequenced, revealing a presence not only of fusC but also of blaZ, aacA-aphD and other resistance genes. PVL genes were also common (40%). The hospital-acquired MRSA CC239-III strain was only found twice. A comparison to data from a study on strains collected in 2015 (Montelongo et al., 2022) showed an increase in fusC and PVL carriage and a decreasing prevalence of the CC239 strain. These observations indicate a diffusion of community-acquired strains into hospital settings. The beta-lactam use in hospitals and the widespread fusidic acid consumption in the community might pose a selective pressure that favours MRSA strains with composite SCCmec elements comprising mecA and fusC. This is an unsettling trend, but more MRSA typing data from Egypt are required.

Synthesis, Physicochemical Properties and Molecular Docking of New Benzothiazole Derivatives as Antimicrobial Agents Targeting DHPS Enzyme.

The drug-resistance problem is widely spread and becoming more common in community-acquired and nosocomial strains of bacteria. Therefore, finding new antimicrobial agents remains an important drug target. From this perspective, new derivatives of benzothiazole were synthesized and evaluated for their antimicrobial activity and ability to inhibit the DHPS enzyme. The synthesis was carried out by the reaction of benzothiazole N-arylsulphonylhydrazone with N-aryl-2-cyano-3-(dimethylamino)acrylamide, N-aryl-3-(dimethylamino)prop-2-en-1-one, arylaldehydes or diazonium salt of arylamine derivatives, which led to the formation of N-arylsulfonylpyridones 6a-d (yield 60-70%) and 12a-c (yield 50-60%),N-(2-(benzo[d]thiazole-2-yl)-3-arylacryloyl-4-methylsulfonohydrazide 14a-c (yield 60-65%), 4-(benzo[d]thiazole-2-yl)-5-aryl-1H-pyrazol-3(2H)-one 16a-c (yield 65-75%), and N'-(2-(benzo[d]thiazol-2-yl)-2-(2-arylhydrazono)acetyl)-4-arylsulfonohydrazide 19a-e (yield 85-70%). The antimicrobial evaluations resulted into a variety of microbial activities against the tested strains. Most compounds showed antimicrobial activity against S. aureus with an MIC range of 0.025 to 2.609 mM. The most active compound, 16c, exhibited superior activity against the S. aureus strain with an of MIC 0.025 mM among all tested compounds, outperforming both standard drugs ampicillin and sulfadiazine. The physicochemical-pharmacokinetic properties of the synthesized compounds were studied, and it was discovered that some compounds do not violate rule of five and have good bioavailability and drug-likeness scores. The five antimicrobial potent compounds with good physicochemical-pharmacokinetic properties were then examined for their inhibition of DHPS enzyme. According to the finding, three compounds, 16a-c, had IC50 values comparable to the standard drug and revealed that compound 16b was the most active compound with an IC50 value of 7.85 μg/mL, which is comparable to that of sulfadiazine (standard drug) with an IC50 value of 7.13 μg/mL. A docking study was performed to better understand the interaction of potent compounds with the binding sites of the DHPS enzyme, which revealed that compounds 16a-c are linked by two arene-H interactions with Lys220 within the PABA pocket.

Identification of Staphylococcus aureus Penicillin Binding Protein 4 (PBP4) Inhibitors.

Methicillin-resistant Staphylococcus aureus (MRSA) is a global healthcare concern. Such resistance has historically been attributed to the acquisition of mecA (or mecC), which encodes an alternative penicillin binding protein, PBP2a, with low β-lactam affinity. However, recent studies have indicated that penicillin binding protein 4 (PBP4) is also a critical determinant of S. aureus methicillin resistance, particularly among community-acquired MRSA strains. Thus, PBP4 has been considered an intriguing therapeutic target as corresponding inhibitors may restore MRSA β-lactam susceptibility. In addition to its role in antibiotic resistance, PBP4 has also recently been shown to be required for S. aureus cortical bone osteocyte lacuno-canalicular network (OLCN) invasion and colonization, providing the organism with a niche for re-occurring bone infection. From these perspectives, the development of PBP4 inhibitors may have tremendous impact as agents that both reverse methicillin resistance and inhibit the organism’s ability to cause chronic osteomyelitis. Accordingly, using a whole-cell high-throughput screen of a 30,000-member small molecule chemical library and secondary assays we identified putative S. aureus PBP4 inhibitors. Quantitative reverse transcriptase mediated PCR and PBP4 binding assays revealed that hits could be further distinguished as compounds that reduce PBP4 expression versus compounds that are likely to affect the protein’s function. We also showed that 6.25 µM (2.5 µg/mL) of the lead candidate, 9314848, reverses the organism’s PBP4-dependent MRSA phenotype and inhibits its ability to traverse Microfluidic-Silicon Membrane-Canalicular Arrays (µSiM-CA) that model the OLCN orifice. Collectively, these molecules may represent promising potential as PBP4-inhibitors that can be further developed as adjuvants for the treatment of MRSA infections and/or osteomyelitis prophylactics.

The thematic role of extracellular loop of VraG in activation of the membrane sensor GraS in a cystic fibrosis MRSA strain differs in nuance from the CA-MRSA strain JE2.

Patients with cystic fibrosis (CF) often suffer recurrent bronchial bacterial infections that lead to deterioration of lung function over time. The infections in CF patients are often due to S. aureus and P. aeruginosa that colonize the airways. Significantly, methicillin-resistant S. aureus (MRSA) makes it challenging for treatment in CF patients due to its feature of multiple antibiotic resistance. In bronchial airways, cationic antimicrobial peptides are often present in mucosa cells, neutrophils, and macrophages that interfere with bacterial proliferation. The major mechanism for resistance to the bactericidal activity of cationic peptides in S. aureus is mediated by the GraRS two-component system that activates expression of MprF and DltABCD to increase surface positive charge to repel interactions with cationic peptides. We recently found that VraG, a membrane permease component of the VraFG efflux pumps, harbors a long 200-residue extracellular loop (EL) that utilizes K380 to interact with the negatively charged 9-residue extracellular loop of the membrane sensor GraS to control mprF expression in a community-acquired MRSA strain JE2. In this study, we extended this observation to a CF MRSA strain CF32A1 where we affirmed that the EL loop of VraG controls GraS-mediated signal transduction; however, in contrast to community acquired MRSA strain JE2, the CF MRSA strain CF32A1 requires both K380 and K388 in the EL of VraG to properly modulate signal transduction mediated by GraS. This effect was not attributable to the several single nucleotide polymorphisms that exist between VraG and GraS in the two MRSA strains.

PREVALENCE OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS IN WESTERN TAMILNADU

Humans are natural reservoir for Staphylococcus aureus, and asymptomatic colonization is far more common than infection. Colonization byStaph.aureusmay be persistent and can last for years. Recent reports of strains of Methicillin Resistant Staphylococcus aureus (MRSA) isolated from community have led speculation that the epidemiology of S. aureus is changing .Usually, MRSA infections havebeen a concern among hospitals for decades now and the reports revealthat the community acquired MRSA is increasing . The community acquired strains could possibly have arisen as a consequence of resistance gene transfer from a hospital acquired (nosocomial) donor into a susceptible recipient. With appropriate analysis of donor andrecipient chromosomes, it could be possible to determine whether these newly identified communityacquired strains are wild or self-supporting.The present study was conducted with a total sample of 1296 wound and other skin infection samples that were collected from different hospitals in western Tamilnadu. The specimens were inoculated in blood agar for isolation and identified as S.aureus by using standard method based on colony morphology, Gram's stain, catalase and coagulase test. A total 258 isolates were confirmed as S.aureus. These strains were processed by the following three techniques,(i) oxacillin, Methicillin and cefoxition disk diffusion method, (ii) cultured in MeRSA plate, (iii) Vitek 2 fully automated ID and AST system for detection mecA gene producer. 34 MRSA strains were identified out of 258 strains.

Genomic dissection of Klebsiella pneumoniae infections in hospital patients reveals insights into an opportunistic pathogen

Klebsiella pneumoniae is a major cause of opportunistic healthcare-associated infections, which are increasingly complicated by the presence of extended-spectrum beta-lactamases (ESBLs) and carbapenem resistance. We conducted a year-long prospective surveillance study of K. pneumoniae clinical isolates in hospital patients. Whole-genome sequence (WGS) data reveals a diverse pathogen population, including other species within the K. pneumoniae species complex (18%). Several infections were caused by K. variicola/K. pneumoniae hybrids, one of which shows evidence of nosocomial transmission. A wide range of antimicrobial resistance (AMR) phenotypes are observed, and diverse genetic mechanisms identified (mainly plasmid-borne genes). ESBLs are correlated with presence of other acquired AMR genes (median n = 10). Bacterial genomic features associated with nosocomial onset are ESBLs (OR 2.34, p = 0.015) and rhamnose-positive capsules (OR 3.12, p < 0.001). Virulence plasmid-encoded features (aerobactin, hypermucoidy) are observed at low-prevalence (<3%), mostly in community-onset cases. WGS-confirmed nosocomial transmission is implicated in just 10% of cases, but strongly associated with ESBLs (OR 21, p < 1 × 10−11). We estimate 28% risk of onward nosocomial transmission for ESBL-positive strains vs 1.7% for ESBL-negative strains. These data indicate that K. pneumoniae infections in hospitalised patients are due largely to opportunistic infections with diverse strains, with an additional burden from nosocomially-transmitted AMR strains and community-acquired hypervirulent strains.

Epidemiological and clinical features of Panton-Valentine Leukocidin positive Staphylococcus aureus bacteremia: A case-control study.

Panton-Valentine Leukocidin (PVL) toxin in Staphylococcus aureus has been associated with both severe pneumonia and skin and soft tissue infections. However, there are only limited data on how this virulence factor may influence the clinical course or complications of bacteremic S. aureus infections. Between September 2016 and March 2018, S. aureus isolates from clinical cultures from hospitals in an academic medical center underwent comprehensive genomic sequencing. Four hundred sixty-nine (29%) of 1681 S. aureus sequenced isolates were identified as containing the genes that encode for PVL. Case patients with one or more positive blood cultures for PVL were randomly matched with control patients having positive blood cultures with lukF/lukS-PV negative (PVL strains from a retrospective chart review). 51 case and 56 control patients were analyzed. Case patients were more likely to have a history of injection drug use, while controls more likely to undergo hemodialysis. Isolates from 78.4% of case patients were methicillin resistant as compared to 28.6% from control patients. Case patients had a higher incidence of pneumonia and skin and soft tissue infection and longer duration of fever without differences in length of bacteremia. Clinical cure or expiration was comparable. These results are consistent with prior observations associating the PVL toxin with both community-acquired MRSA strains as well as severe staphylococcal pneumonia. The presence of the PVL toxin does not appear to otherwise influence the natural history of bacteremic S. aureus disease other than in prolonging the duration of fever.

Antimicrobial Resistance in Enterococci

Background. Enterococcus spp. are opportunistic agents of community-acquired and in-hospital infections, which have been considered a threat to public health due to their antimicrobial resistance, primarily to glycopeptides, in recent years.The aim of the study is to determine the prevalence of various Enterococcus species causing infections in hospitalized patients and their antimicrobial resistance.Methods included identification by MALDI-TOF mass spectrometry and antimicrobial susceptibility testing in accordance with the EUCAST or, in their absence, CLSI guidelines.Results. Antimicrobial resistance in 1562 consecutive Enterococcus strains isolated from hospitalized patients was determined in a major medical center admitting patients from various regions of the Russian Federation in 2019. The predominance of E.faecalis and E.faecium (99.5%) was revealed; the frequency of isolation of the former was 56% higher than that of the latter. E.avium, E.casseliflavus, E.gallinarum, E.durans were isolated from 0.5% of biological samples. The highest level of resistance of enterococci was observed to erythromycin (84.8%), tetracycline (75.0%), and rifampicin (68.2%). Multidrug, as well as vancomycin resistance, prevailed in E.faecium. All E.faecium strains isolated from blood were multidrug resistant. Resistance to vancomycin in enterococci, causing bloodstream infections, was observed solely in 19.5% of E.faecium; all vancomycin-resistant isolates were also resistant to teicoplanin. Linezolid resistance was detected in 2 community-acquired strains of E.faecalis (0.1%). Rare enterococci have shown diverse patterns of antimicrobial resistance.Conclusions. E.faecalis and E.faecium prevailed among Enterococcus spp. causing infections in hospitalized patients. Multidrug resistance and vancomycin resistance were observed predominantly in E.faecium, especially in strains causing blood-stream infections. Further monitoring of the spread and antimicrobial resistance of various Enterococcus spp. in hospital and community-acquired infections is needed.