In Vitro Antibacterial Susceptibility of Different Pathogens to Thirty Nano-Polyoxometalates

Due to their unique properties, nano-polyoxometalates (POMs) can be alternative chemotherapeutic agents instrumental in designing new antibiotics. In this research, we synthesized and characterized “smart” nanocompounds and validated their antibacterial effects in order to formulate and implement potential new drugs. We characterized thirty POMs in terms of antibacterial activity–structure relationship. The antibacterial effects of these compounds are directly dependent upon their structure and the type of bacterial strain tested. We identified three POMs that presented sound antibacterial activity against S. aureus, B. cereus, E. coli, S. enteritidis and P. aeruginosa strains. A newly synthesized compound K6[(VO)SiMo2W9O39]·11H2O (POM 7) presented antibacterial activity only against S. aureus (ATCC 6538P). Twelve POMs exerted antibacterial effects against both Gram-positive and Gram-negative strains. Only one POM (a cluster derivatized with organometallic fragments) exhibited a stronger effect compared to amoxicillin. New studies in terms of selectivity and specificity are required to clarify these extremely important aspects needed to be considered in drug design.

1072. In Vitro Antibacterial Susceptibility Testing of Sulopenem Against Category A and B Bio-threat Bacterial Pathogens

Background Sulopenem is a thiopenem β-lactam antibiotic being developed for the treatment of infections caused by multi-drug resistant bacteria. Sulopenem possesses potent activity against species of the Enterobacterales that encode ESBLs or AmpC-type β-lactamases that confer resistance to third generation cephalosporins. It has also demonstrated good in vitro microbiological activity against a range of bacterial pathogens including penicillin resistant S. pneumoniae, β-lactamase-producing H. influenzae and M. catarrhalis. Sulopenem is available as intravenous and oral pro-drug formulations, and its activity aligns with the most urgent drug-resistant antimicrobial threats defined by the CDC. Methods Bacterial inoculums were prepared by suspending colonies into cation adjusted Mueller Hinton broth (CAMHB) from 18-24 h (B. anthracis, B. pseudomallei and B. mallei plates incubated at 35ºC); or 36-48 h (F. tularensis and Y. pestis plates incubated at 35ºC and 28ºC, respectively). Sheep blood agar plates were used for B. anthracis and Y. pestis. Chocolate agar plates were used for F. tularensis, B. pseudomallei and B. mallei. Suspended cultures were diluted with CAMHB to achieve a turbidity equivalent to a 0.5 McFarland standard. MICs were determined by the microdilution method in 96-well microplates according to CLSI guidelines (Clinical and Laboratory Standards Institute, 2020). Antibiotic ranges used for sulopenem were 0.03 - 64 μg/mL and 0.004 - 8 μg/mL for the diversity strains of B. anthracis, F. tularensis, Y. pesis, B. mallei, and B. pseudomallei, based on a final well volume of 100 μl after inoculation. Results A summary of sulopenem MIC90 results versus bio-threat bacterial pathogens in presented in the table. Criteria for down selection into mice was met for all pathogens except F. tularensis. Sulopenem MIC90 Summary for Down Selection Criteria Conclusion Sulopenem is active in vitro against a number of bio-threat pathogens at concentrations likely to be achieved after oral dosing in humans and meets criteria to be tested in the murine model of B. anthracis, Y. pestis, B. mallei, and B. pseudomallei. Disclosures Michael Dunne, MD, Iterum Therapeutics (Board Member, Consultant, Shareholder) Steven I. Aronin, MD, Iterum Therapeutics (Employee, Shareholder)

PHENOTYPIC DETECTION OF EFFLUX MECHANISM IN AMIKACIN-RESISTANT ACINETOBACTER ISOLATES FROM TWO DIFFERENT STATES IN SOUTH INDIA

Acinetobacter has already gained resistance to the majority of antibiotics available. Aminoglycosides are commonly used to treat invasive infections. Aminoglycoside resistance is associated with decreased drug absorption, aminoglycoside modification, and aminoglycoside efflux. The aim of this study was to detect the presence of an efflux mechanism in amikacin-resistant Acinetobacter isolated from hospital wards using Carbonyl Cyanide 3- Chlorophenylhydrazone (CCCP). One hundred isolates of Acinetobacter were isolated from tertiary care hospitals in two distinct South Indian states. Antibacterial susceptibility patterns were discovered between 2017 and 2019. Amikacin minimum inhibitory concentration (MIC) for resistant Acinetobacter isolates was determined using Clinical and Laboratory Standards Institute (CLSI) standards. The efflux system activity was determined using CCCP. Among 100 Acinetobacter baumannii isolates, 49 isolates with amikacin resistance were found. The MIC’s of Acinetobacter ranged between 2 – 1024 μg/mL for the amikacin studied. After treatment with the efflux pump inhibitor, 38.77% of isolates became less resistant to amikacin, as determined by phenotypic detection of efflux pumps, showing a decrease in antibiotic MICs of at least four fold. The data demonstrated the importance of efflux pump activity conferring amikacin resistance on Acinetobacter clinical isolates.

Antibacterial activity of aquatic extract of Myrtus communis leaves against Periodontitis isolated bacteria

Myrtus communis is an evergreen plant that can survive stressful environments and high-temperature seasons. Treatment using green plants was the most trended in recent years. The present study aimed to evaluate the antibacterial effects of Myrtus communis leaves against bacteria isolated from periodontitis. Fifty samples were collected from periodontitis subjects in both genders (female 32 % and male 68 %). The isolates were diagnosed by morphological characterization and biochemical tests. M. communis leaves were identified, collected, and prepared for extraction. The plant leaves were extracted using distilled water. The antibacterial susceptibility testing was performed by the well diffusion method. Antibiotics susceptibility patterns were executed using the disc diffusion method. All the isolates belonged to gram-positive bacteria. Among the isolated bacteria, 20, 18, and 12 were Lactobacillus spp., Streptococcus spp., and Staphylococcus aureus, respectively. The antibacterial susceptibility testing of M. communis extract showed a potential zone of inhibition against all the tested bacteria. Of the different concentrations, 30 mg/ml showed the highest zone of inhibition, 18.2 mm, 19.50 mm, and 30.66 mm against Streptococcus spp., Staphylococcus spp., and Lactobacillus spp. Among the tested antibiotics, ciprofloxacin and chloramphenicol exhibited the highest zone of inhibition against the tested bacteria. The aquatic extract of M. communis leaves was found to be effective against gram-positive bacteria. Further studies are warranted to investigate the active bio-compounds.

Four Types of ST11 Novel Mutations From Increasing Carbapenem-Resistant Klebsiella pneumoniae in Guangdong, 2016–2020

Objectives: This study aimed to explore changes in carbapenem-resistant Klebsiella pneumoniae (CR-KP) isolates collected in Guangdong over the period of 2016–2020.Methods: Antibacterial susceptibility was quantified through VITEK 2 compact and K-B method. Carbapenemase phenotypes and genotypes were characterized by modified carbapenem inactivation method (mCIM), EDTA-carbapenem inactivation method (eCIM), and polymerase chain reaction (PCR). Molecular characteristics and evolutionary trends were analyzed by multilocus sequence typing and evolutionary tree.Results: Isolates (2,847) of K. pneumoniae were separated in 2016–2020, and the separate rate of CR-KP increased from 5.65 to 9.90% (p = 0.009). The top 3 wards were intensive care unit (ICU) (21.92%), neonatal wards (13.70%), and respiratory wards (12.33%). In 146 CR-KP strains, serine carbapenemase was the main phenotype, and KPC was the main genotype, and 57 contained two resistant genes, and 1 contained three resistant genes. Two polygenic strains were first found: IMP + GES and KPC + NDM + VIM, but all the phenotypes were metalloenzyme, which indicated that metalloenzyme was usually the first choice for CR-KP resistance. In addition, all the ST54 of metalloenzyme type contained IMP, and all the ST45, ST37, and ST76 contained OXA. ST11 was the most prevalent (42.47%); ST11 and its mutants proved the predominant sequence type making up 51.1% of the carbapenemase-producing isolates. A novel type of ST11 mutation, the rpoB was mutated from sequence 1 to sequence 146, was in an independent separate branch on the evolutionary tree and was resistant to all antibacterial agents. The other three mutants, rpoB 1–15, infB 3–148, and infB 3–80, are also resistant to all antibacteria. Of note, all the four mutants produced serine carbapenemase and contained KPC, and indicated that the prevalent strain in China, ST11, has serious consequences and potential outbreaks.Conclusion: The infection rate of CR-KP has increased, and ICU and neonatal wards have become the key infection areas. Producing serine enzyme, the KPC genotype, and ST11 are the predominant CR-KP. Polygenic strains and ST11 mutation made clinical treatment difficult and may become a potential threat.

Prevalence, Antimicrobial Susceptibility, and Molecular Characterization of Escherichia coli Isolated From Raw Milk in Dairy Herds in Northern China

Escherichia coli is a common bacterium in the intestines of animals, and it is also the major important cause of toxic mastitis, which is an acute or peracute disease that causes a higher incidence of death and culling of cattle. The purpose of this study was to investigate E. coli strains isolated from the raw milk of dairy cattle in Northern China, and the antibacterial susceptibility of these strains and essential virulence genes. From May to September 2015, 195 raw milk samples were collected from 195 dairy farms located in Northern China. Among the samples, 67 (34.4%) samples were positive for E. coli. About 67 E. coli strains were isolated from these 67 samples. The prevalence of Shiga toxin-producing E. coli (STEC), enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), and enteroinvasive E. coli (EIEC) were 9, 6, 4.5, and 1.5%, respectively. Among the virulence genes detected, stx1 was the most prevalent (6/67, 9%) gene, followed by eae (3/67, 4.5%), and estB (2/67, 3%). Moreover, the strains exhibited different resistance levels to ampicillin (46.3%), amoxicillin-clavulanic acid (16.4%), trimethoprim-sulfamethoxazole (13.4%), tetracycline (13.4%), cefoxitin (11.9%), chloramphenicol (7.5%), kanamycin (7.5%), streptomycin (6.0%), tobramycin (4.5%), azithromycin (4.5%), and ciprofloxacin (1.5%). All of the E. coli isolates were susceptible to gentamicin. The prevalence of β-lactamase-encoding genes was 34.3% in 67 E. coli isolates and 45% in 40 β-lactam-resistance E. coli isolates. The overall prevalence of blaSHV, blaTEM, blaCMY, and blaCTX-M genes were 1.5, 20.9, 10.4, and 1.5%, respectively. Nine non-pathogenic E. coli isolates also carried β-lactamase resistance genes, which may transfer to other pathogenic E. coli and pose a threat to the farm’s mastitis management projects. Our results showed that most of E. coli were multidrug resistant and possessed multiple virulence genes, which may have a huge potential hazard with public health, and antibiotic resistance of E. coli was prevalent in dairy herds in Northern China, and ampicillin should be used cautiously for mastitis caused by E. coli in Northern China.

S. aureus and K. pneumoniae on the Surface and within Core of Tonsils in Adults with Recurrent Tonsillitis

Background and Objectives: Recurrent tonsillitis is an infection of the palatine tonsils. Samples for microbiological testing are usually obtained from the inflamed surface of the tonsils. Colonizing the surface bacteria does not always correlate with pathogens causing recurrent tonsillitis and there is no consensus or this in research studies. The aim of the study was to compare whether Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumoniae) differ when isolated from the tonsillar surface or tonsillar crypts in patients with recurrent tonsillitis. Materials and Methods: a case series study was conducted at a tertiary referral center among 25 patients diagnosed with recurrent tonsillitis. An evaluation of S. aureus and K. pneumoniae incidence, biofilm formation and antibacterial susceptibility was performed. Results: There was a statistically significant association between surface and punch biopsy samples for S. aureus (Fisher’s Exact test p = 0.004) and K. pneumoniae (Fisher’s Exact test p < 0.001). A McNemar test did not reveal a statistically significant association. Although the antibacterial resistance profile was not broad, five out of nine S. aureus isolates were biofilm producers and four out of five K. pneumoniae isolates were biofilm producers. Conclusions: Surface and core cultures of tonsils are comparable with a differing incidence between the surface and the punch biopsy cultures for S. aureus and K. pneumoniae. A larger quantity of bacteria exist in surface samples suggesting that a biopsy sample may be less challenging in evaluating recurrent tonsillitis. We recommend that antibacterial susceptibility results are considered alongside the biofilm-forming potential of isolated bacteria.