Mueller-Hinton Agar Plates Research Articles

Reversion of KPC-114 to KPC-2 in ceftazidime-avibactam- resistant/meropenem-susceptible Klebsiella pneumoniae ST11 is related to low mutation rates.

Klebsiella pneumoniae strains that produce Klebsiella pneumoniae Carbapenemase (KPC) variants displaying resistance to ceftazidime-avibactam (CZA) often remain susceptible to meropenem (MEM), suggesting a potential therapeutic use of this carbapenem antibiotic. However, in vitro studies indicate that these sorts of strains can mutate becoming MEM-resistant, raising concerns about the effectiveness of carbapenems as treatment option. We have studied mutation rates occurring from the reversion of MEM-susceptible KPC-114 to MEM-resistant KPC-2, in CZA-resistant K. pneumoniae belonging to ST11. Two-step fluctuation assays (FAs) were conducted. In brief, initial cultures of KPC-114-producing K. pneumoniae showing 1 µg/mL MEM MIC were spread on Mueller-Hinton agar plates containing 2-8 µg/mL MEM. A second step of FA, at 4-16 µg/mL MEM was performed from a mutant colony obtained at 2 µg/mL MEM. Mutation rates were calculated using maximum likelihood estimation. Parental and mutant strains were sequenced by Illumina NextSeq, and mutations were predicted by variant-calling analysis. At 8 µg/mL MEM, mutants derived from parental CZA-resistant (MIC ≥ 64 µg/mL)/MEM-susceptible (MIC = 1 µg/mL) KPC-114-positive K. pneumoniae exhibited an accumulative mutation rate of 3.05 × 10-19 mutations/cell/generation, whereas at 16 µg/mL MEM an accumulative mutation rate of 1.33 × 10-19 mutations/cell/generation resulted in the reversion of KPC-114 (S181_P182 deletion) to KPC-2. These findings highlight that the reversion of MEM-susceptible KPC-114 to MEM-resistant KPC-2, in CZA-resistant K. pneumoniae ST11 is related to low mutation rates suggesting a low risk of therapeutic failure. In vivo investigations are necessary to confirm the clinical potential of MEM against CZA-resistant KPC variants.IMPORTANCEThe emergence of ceftazidime-avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae is a major concern due to the limited therapeutic options. Strikingly, KPC mutations mediating CZA resistance are generally associated with meropenem susceptibility, suggesting a potential therapeutic use of this carbapenem antibiotic. However, the reversion of meropenem-susceptible to meropenem-resistant could be expected. Therefore, knowing the mutation rate related to this genetic event is essential to estimate the potential use of meropenem against CZA-resistant KPC-producing K. pneumoniae. In this study, we demonstrate, in vitro, that under high concentrations of meropenem, reversion of KPC-114 to KPC-2 in CZA-resistant/meropenem-susceptible K. pneumoniae belonging to the global high-risk ST11 is related to low mutation rates.

Surveillance of In Vitro Activity of Cefiderocol Against Carbapenem-Resistant Gram-Negative Clinical Isolates in a Tertiary Care Hospital.

Antibiotic resistance among Gram-negative bacterial isolates is increasingly observed. With the emergence of carbapenem-resistant and pan-resistant pathogens, treating these resistant infections is becoming more challenging due to the limited number of effective drugs. There is a desperate need for the discovery of new antibiotics with novel mechanisms of action. Cefiderocol is one such novel antibiotic with a unique siderophore-based mechanism of action, which has been recently approved for clinical use against drug-resistant pathogens. The present study aims to identify the in vitro activity of cefiderocol against major carbapenem-resistant clinical isolates, including those resistant to colistin. One hundred and one carbapenem-resistant clinical isolates were included in the study. Identification and antibiotic susceptibility testing were performed using the automated VITEK® 2 Compact (bioMérieux SA, Marcy-l'Étoile, France) identification and susceptibility testing system, except for colistin and cefiderocol. Colistin resistance in Enterobacterales and Pseudomonas aeruginosa was assessed using the agar dilution minimum inhibitory concentration method, while for Acinetobacter baumannii, broth microdilution method was employed. Cefiderocol susceptibility testing was conducted using the Kirby-Bauer disc diffusion method with 30 µg discs on standard Mueller-Hinton agar plates. For selected isolates, cefiderocol minimum inhibitory concentration detection was performed using broth microdilution with iron-depleted cation-adjusted Mueller-Hinton broth. Of the total 101 isolates, the majority (75, 74.25%) were Enterobacterales which includedKlebsiella pneumonia (42, 41.58%) and Escherichia coli (33, 32.67%), followed by Pseudomonas aeruginosa (13, 12.87%) and Acinetobacter baumannii (10, 9.9%). Only three (2.97%)of the isolates were Stenotrophomonas maltophilia. Most of the isolates were susceptible to cefiderocol, with only four (3.96%) isolates showing resistance. Colistin resistance was observed in six (6.12%) of the isolates. There was a good correlation between disc diffusion testing and broth microdilution testing for the detection of cefiderocol-resistant isolates. No cross-resistance with colistin was observed, as all colistin-resistant isolates were uniformly susceptible to cefiderocol Conclusion: Cefiderocol is highly effective with good in vitro activity against the majority of carbapenem-resistant pathogens. While some isolates do show resistance, it is relatively uncommon. Given its safety profile compared to colistin, cefiderocol can serve as an alternative to colistin to treat carbapenem-resistant infections and it may be considered even for the management of colistin-resistant cases. Disc diffusion testing is a reliable method for identifying cefiderocol-resistant isolates in routine clinical and diagnostic laboratories, especially in resource-limited settings.

Comparative Evaluation of Antifungal Efficacy of 3% Sodium Hypochlorite, 2% Chlorhexidine Gluconate, Ozonated Water, Alum Water, and Normal Saline Solutions against Endodontopathogenic Microorganism, Candida Albicans: A Microbiological In Vitro Study.

To compare and evaluate the antifungal efficacy of 3% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX) gluconate, 4 mg/mL ozonated water, and 2M alum water against Candida albicans (C. albicans). A total of 35 patients were selected from those attending the outpatient department of Pedodontics and Preventive Dentistry at Santosh Dental College and Hospitals, Ghaziabad. Their salivary samples were taken and cultured on a Sabouraud's dextrose agar (SDA) plate. The antifungal efficacy of 3% NaOCl, 2% CHX gluconate, 4 mg/mL concentration of ozonated water, and 2M alum water was assessed against clinical strains of C. albicans with the help of agar well diffusion method. The microbial isolates were inoculated into 10 mL of sterile peptone water and incubated at 37°C for 8 hours. The cultures were swabbed on the surface of sterile Mueller-Hinton agar plates using a sterile cotton swab. Five wells of 6 mm diameter were punched in each Petri dish. Around 100 µL of each test solution was poured into the designated wells. Further, the plates were incubated in an upright position at 37°C for 24 hours. The antifungal activity of the test solutions was determined by measuring the diameter of the inhibition zone in mm produced against the Candida isolates, and means were calculated. It was observed that all test solutions used in this study were inhibitory against C. albicans but with a variation in the size of inhibitory zones. According to the means of the diameter of inhibitory zones for all test solutions, the 3% NaOCl represented the statistically significant largest average zones of inhibition against C. albicans, followed by 2% CHX when compared with the other two test solutions alum water and ozonated water. Ozonated water produced the smallest mean inhibitory zone. Sharma A, Naorem N, Srivastava B, et al. Comparative Evaluation of Antifungal Efficacy of 3% Sodium Hypochlorite, 2% Chlorhexidine Gluconate, Ozonated Water, Alum Water, and Normal Saline Solutions against Endodontopathogenic Microorganism, Candida Albicans: A Microbiological In Vitro Study. Int J Clin Pediatr Dent 2024;17(S-1):S17-S24.

Does NexoBrid® have antimicrobial properties?

We previously published the microbial profile of burn wounds managed with NexoBrid® in Pinderfields Regional Burns Centre, Wakefield, UK. Our results showed no significant changes in bacterial colonisation in burn wounds debrided with NexoBrid®. Previous studies described the antimicrobial properties of bromelain enzyme. To date, the effects of NexoBrid® on microorganisms have not been reported. In this study, a series of lab experiments were conducted to investigate the antimicrobial properties of NexoBrid®. Mueller-Hinton agar plates were pre-treated with NexoBrid® and inoculated with common pathogens after serial dilution. Our results revealed that the pre-treated plates showed reduction in the growth of E. faecalis and S. aureus. No zones of inhibition were observed around NexoBrid® after 18 h of incubation. Where a combination of controls and test solutions were added, no zones of inhibition were seen around the NexoBrid® wells in any of fifty tested organisms. The slightly lower infection rates observed in patients treated with NexoBrid® are more likely to be due to efficient selective debridement of necrotic skin rather than direct antimicrobial action.

Ability of Azadirachta indica and Ocimum gratissimum to inhibit the growth of some hospital isolates

The study on the ability of Azadirachta indica and Ocimum gratissimum to inhibit the growth of some hospital isolates was carried out following several reports on the antimicrobial potentials of these plant leaves among locals. Some fresh leaves of Azadirachta indica and Ocimum gratissimum were processed into an aqueous extract as well as an ethanolic extract and preserved at 4oC. samples of Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Candida albicans which served as test microorganisms were obtained from the Federal Medial Centre Umuahia Abia State Nigeria. Antimicrobial sensitivity test of test isolates was determined using the Kirby-bauer disc diffusion method Disc diffusion method of the extracts . A 0.5 Mc farland solution of the 4 organisms were prepared and inoculated into an already prepared Mueller hinton agar plates containing the paper disc of 400mg/ml aqueous and ethanolic extracts. A control experiment was set up with 2mg/ml gentamycin disc. After 48 hours incubation, Ethanolic extract of Azadirachta indica showed the highest zones of inhibition of 7.5mm on Staphylococcus aureus, followed by ethanolic extract of Ocimum gratissimum 7.0mm on Escherichia coli. While the aqueous extracts of both Azadirachta indica and Ocimum gratissimum showed least zones of inhibition on Candida albicans. The overall were more antibacterial effective than antifungal. Therefore, the Ethanolic extract of Azadirachta indica and Ocimum gratissimum possess more antibacterial effect and less antifungal effect.

Characterisation of a novel AmpC beta-lactamase, DHA-33, resistant to inhibition by cloxacillin

Plasmid-encoded DHA-type AmpCs have been extensively reported in Enterobacterales. The expression of the genes encoding these plasmid-mediated enzymes are inducible and these enzymes are capable of conferring resistance to a wide spectrum of beta-lactams including penicillins and broad-spectrum cephalosporins. The identification of infections caused by AmpC-producing bacteria is a necessity, both for infection control/epidemiology purposes and to inform treatment choices. A common testing method for AmpC production in the clinical laboratory setting is to supplement Mueller-Hinton agar plates used for antibiotic disk diffusion with cloxacillin, a potent inhibitor of AmpC enzymes. Here we describe a novel DHA variant, produced by a clinical Escherichia coli isolate, which is resistant to cloxacillin inhibition.

Assessment of Antimicrobial Efficacy of Triphala, Neem, and Chlorhexidine Root Canal Irrigants.

Complete eradication of microorganisms from the root canal and three-dimensional obturation of the canal space are necessary for a successful root canal therapy. In root canal failures, Enterococcus faecalis is the most often detected bacterium. Microorganisms can be eliminated with the aid of chemical irrigation. The current research was conducted to evaluate the antimicrobial effect of triphala, neem, and chlorhexidine root canal irrigants. Mueller-Hinton agar plates were inoculated with the E. faecalis (ATCC) bacterial culture after it had been cultured overnight in brain heart infusion (BHI) broth. Agar well diffusion was used to measure antibacterial inhibition. After being introduced to their appropriate wells in agar plates, the three research irrigants were incubated for 24 hours at 37°C. Every well's bacterial inhibition zone was noted. After tabulating the results, statistical analysis was done. When triphala and A. indica extract (neem) were added to chlorhexidine, the highest inhibitory zone against E. faecalis was observed. The herbal remedy triphala and the extract from A. indica exhibited an inhibitory zone when tested against E. faecalis. As a result, these irrigants might be utilized as a substitute for root canal irrigants.

ANTIMICROBIAL POTENCY AND PHYTOCHEMICAL CONTENTS OF THREE COMMON NIGERIA MEDICINAL PLANTS’ LEAF EXTRACTS

Morinda lucida, Tithonia diversifolia and Carica papaya are three medicinal plants commonly used for curing several diseases in traditional medicine. However, comparative scientific information as regards their antibacterial, antifungal, and phytochemical properties remains limited. Fresh leaves of Morinda lucida, Tithonia diversifolia, and Carica papaya were harvested and extracted by soaking pulverized samples of the plants in 250 mL of water and ethanol. The phytochemical constituents were determined by subjecting the decoction to qualitative and quantitative tests using standard methods. The antimicrobial and antifungal activities were determined by solidified Mueller-Hinton agar plate and solidified Potato Dextrose agar plate respectively. Alkaloids, flavonoids, saponins, tannins, and terpenoids were shown to be the primary metabolites in the ethanolic extract of the three plant species. Cardiac glycosides are only present in T. diversifolia. Aqueous and ethanolic leaf extracts of the three species had significant, but varying antibacterial activity and no antifungal properties. Ethanolic extracts of Morinda lucida were the most active against Escherichia coli with a 30 mm zone of inhibition and very active against Klebsiella pneumonia and Enterobacter aerogenes with 28 mm and 24 mm zone of inhibition, respectively. The aqueous extracts of T. diversifolia were more active against Staphylococcus aureus, Serratia marscences, and Enterobacter aerogenes than ethanolic extract. The ethanolic decoction of C. papaya was active against Enterococci. This study showed that depending on the decoction solvent and the microbes under investigation, the leaf extracts of the three plant species have a tolerable but variable level of activity.

A Comparative Evaluation of Antimicrobial Efficacy of Various Intracanal Medicaments (Curcuma longa, Honey, Nitrofurantoin, and Calcium Hydroxide) on Enterococcus faecalis: An in vitro Study

Background In the modern era of dentistry, natural and herbal alternatives are favored since they are renewable, have fewer adverse effects, and are cost-effective. Purpose To assess the effectiveness of different intracanal medications in eliminating Enterococcus faecalis. Materials and Methods In total, 50 single-rooted extracted teeth were decoronated at the cemento-enamel junction followed by the preparation of the canal. Then, in each of the presterilized samples, inoculum containing the E. faecalis was transferred and incubated at 37°C for 24 hours. Samples were allocated into 5 groups of 10 each: Group A (saline), Group B (calcium hydroxide), Group C ( Curcuma longa), Group D (honey), and Group E (nitrofurantoin group). The medicaments were injected into the canals respectively, the antibacterial assessment was done on the 1st and 7th day. Dentinal shavings are incubated and streaked on Mueller–Hinton agar plates and incubated for 24 hours at 37°C and the colony forming units (CFUs) were assessed. Results Among all the groups, there was a significant change in the number of colonies from Day 1 to Day 7, except in Group A (saline). Comparison between the groups revealed significant differences, with better efficacy by Group D (honey) followed by Group E (nitrofurantoin) and Group C ( C. longa). The least antimicrobial efficacy was observed with calcium hydroxide and no activity with saline. Conclusion Honey has the greatest antimicrobial efficacy among all the tested intra-canal medicament groups.

Effectiveness of white tea-mediated silver nanoparticles as an intracanal irrigant against Enterococcus faecalis: An in vitro study.

The probability of a positive outcome of root canal therapy is substantially higher if the infection is eradicated successfully before the obturation of the root canal system. Irrigation is an essential aspect of root canal debridement, as it enables more thorough cleaning than is possible with root canal instrumentation alone. To overcome the side effects of chemical irrigants, there has been a search for herbal medicines as substitutes. The aim of the present study was to explore the antimicrobial efficacy of white tea-mediated silver nanoparticles (AgNPs) formulated as an intracanal irrigant against Enterococcus faecalis, and to compare it with the efficacy of chlorhexidine and sodium hypochlorite irrigants. The experimental groups were as follows: group I - white tea-mediated AgNPs; group II - 2% chlorhexidine; and group III - 2.5% sodium hypochlorite. The characterization of AgNPs was performed using ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM) analysis. Enterococcus faecalis was inoculated onto Mueller-Hinton agar plates. The disks impregnated with irrigants were placed on the inoculated plates and incubated aerobically at 37°C for 24 h. Then, the growth inhibition zones were measured. Statistical analysis was performed using the one-way analysis of variance (ANOVA) and the post hoc tests. A concentration of 50 μL of white tea-mediated AgNPs exhibited the greatest zone of inhibition (32 ±2 mm), followed by 2% chlorhexidine (25 ±1 mm) and 2.5% sodium hypochlorite (23 ±3 mm). White tea-mediated AgNPs showed promising results in the elimination of E. faecalis, being superior to chlorhexidine and sodium hypochlorite irrigants.

Study of Methicillin-resistant Staphylococcus aureus Isolated from Various Clinical Specimens from Tertiary Care Hospital

ABSTRACT Introduction: Staphylococci are Gram-positive bacteria, with a diameter of 0.5–1.5 μm and individual cocci, which are divided in more than one plane from the grape-like cluster. In the genus staphylococci, 32 species and 8 subspecies are present in many of which are present as a commensal in the human body. Staphylococci are frequently found as a normal flora of skin mucosal, surface of respiratory, upper elementary, and urogenital tract of the human body. In immunocompromised condition, the infection can be spread by skin-to-skin contact and also by excretion such as saliva aerosol releasing during sneezing and coughing. Infection of staphylococci may also spread from the animal product such as nonpasteurized milk and milk products. Over the last few decades, Staphylococcus aureus has emerge as the most dangerous organism, which is known as methicillin-resistant S. aureus (MRSA). Some strains show vancomycin resistance by S. aureus in hospitalized patients. The present study was conducted to study the prevalence and antibiogram of MRSA isolates in a clinical sample from Acharya Vinoba Bhave Rural Hospital. Materials and Methods: This study was conducted in the Department of Microbiology at Jawaharlal Nehru Medical College (Datta Meghe Institute of Higher Education and Research), Wardha, from August 2020 to December 2021. The samples received in the microbiology laboratory were inoculated on blood agar and MacConkey’s agar, and incubated for 24 h at 37°C for staphylococcal isolation. A total of 145 Staphylococcal aureus were isolated and confirmed by Gram stain and various biochemical tests such as catalase test, oxidase test, coagulase test, and mannitol salt agar. Antibiotic susceptibility test was examined on the Mueller–Hinton agar plate using the modified Kirby–Bauer disc diffusion method. Screening of methicillin resistant was performed by cefoxitin (30 μg) disc diffusion method and interpreted according to CLSI guideline. Results: The prevalence of MRSA was 76 (52.41%) to methicillin-susceptible S. aureus. The highest MRSA was found in the age group >50 years (26.31%). Out of 76 MRSA isolates from different departments, the medicine and orthopedic departments show maximum MRSA as 19.74% each followed by pediatrics (17.11%) and surgery (13.16). Out of 76 MRSA isolates, vancomycin showed 93.42% sensitivity followed by linezolid (85.52%), Gentamicin (71.05%), tetracycline (56.57%), clindamycin (46.05%), and erythromycin (31.57%). Conclusion: With the advancement of new therapeutic agent, MRSA is also being easily resistant. Due to increasing cases of MRSA, there is an increase in the rate of morbidity and mortality. Moreover, except vancomycin, other drugs are resistant, as their MIC is not in the susceptible range. Thus, the results of this study indicate that vancomycin is a suitable medication to take when MRSA cases rise. In such cases, MRSA can be controlled by regular monitoring and checking the irrational use of antibiotics.

Comparison of antimicrobial efficacy of green tea extract and Triphala as root canal irrigants against Fusobacterium nucleatum using real-time polymerase chain reaction – An in vitro study

Aim: Fusobacterium nucleatum has gained attention in the endodontic literature as it is a predominant microorganism in primary, secondary, and persistent root canal infections. Current irrigants have lot of drawbacks and are unlikely to predictably achieve a bacteria-free root canal system, which can lead to these failures. Herbal alternatives are now gaining popularity in the field of endodontics, paving a new way in the disinfection of root canals. The aim of this study is to evaluate the antimicrobial efficacy of green tea extract and Triphala as root canal irrigants against F. nucleatum using real-time Polymerase chain reaction (PCR). Methods: Extracted teeth were taken and inoculated with F. nucleatum, which was grown in a Mueller–Hinton agar plate under anaerobic conditions. The samples were cleaned and shaped and irrigated with green tea extract, Triphala extract, and dimethyl sulfoxide, which were compared to the widely used irrigant, sodium hypochlorite. Cycle threshold value was used to calculate the efficacy of the irrigant against F. nucleatum after which the samples were subjected to reverse transcriptase PCR. The data were analyzed and the data between the group were compared using the one-way ANOVA followed by a post hoc Tukey’s test. Results: Triphala extract demonstrated high antimicrobial activity against F. nucleatum1. It revealed statistically significant differences between Triphala extract and sodium hypochlorite (NaOCL) (P = 0.001). Green tea extract also displayed antimicrobial activity. Both the Triphala and green tea extracts showed a significant difference (P < 0.001). Conclusion: Triphala extract showed better antibacterial efficacy when compared to 3% NaOCl and green tea extract against F. nucleatum.

Endophytic Bacillus aerophilus from the Leaves of Azadirachta indica as a Potential Biocontrol against Staphylococcus aureus

Aims: The study entailed isolation and identification of Bacillus aerophilus in the leaves of young Azadirachta indica plants, establishing the antimicrobial activity of the endophyte against Staphylococcus aureus, and screening for phytochemicals. The study investigated the potential of the endophytic Bacillus aerophilus in pathogen inhibition and phytochemical screening for bioactive compounds produced by the endophyte that can be used in drug development. The research contributes to the wider scientific goal of curbing rising cases of antibiotic resistance.
 Place and Duration of Study: Sample: collected from Kanyonyoo in Kitui County, between August 2022 and June 2023.
 Methodology: The bacteria were aseptically isolated and sub-cultured on nutrient agar. For identification, the bacteria underwent biochemical tests and molecular characterization. The 16S rRNA region was amplified and sequenced using universal primers 27F and 1492R. Bacterial isolate K1L003 was identified as Bacillus aerophilus. For antimicrobial testing, the agar disk diffusion method was used against pathogenic Staphylococcus aureus on Mueller Hinton Agar plates (MHA). The controls were doxycycline and vancomycin.
 Results: The endophytic isolate only inhibited Staphylococcus aureus (P < .001), with an inhibition mean similar to doxycycline (26 mm), against the pathogen. The endophytic isolate produced terpenoids, saponins, alkaloids, and flavonoids.
 Conclusion: Endophytic Bacillus aerophilus has better antimicrobial inhibition potential than vancomycin, against Staphylococcus aureus and produces diverse bioactive secondary metabolites. The endophyte has the potential to produce compounds that are useful in treating drug-resistant Staphylococcal infections.

Apparent prevalence and selected risk factors of methicillin-resistant Staphylococcus aureus and non-aureus staphylococci and mammaliicocci in bulk tank milk of dairy herds in Indiana, Ohio, and Michigan

The purpose of this study was to determine the apparent prevalence and risk factors of methicillin-resistant Staphylococcus aureus and non-aureus staphylococci and mammaliicocci (NASM) in bulk tank milk (BTM) obtained from 300 dairy farms that belong to a cooperative collecting milk from Indiana, Michigan, and Ohio. Dairy field personnel recorded information about selected farm level risk factors and collected and froze BTM samples (n = 300) that were sent to Michigan State University researchers. Milk samples were thawed at room temperature and pre-enriched by adding 1 to 4 mL of Mueller-Hinton broth supplemented with 6.5% NaCl and incubated at 37°C for 24 h. Subsequently, 10 µL was plated on mannitol salt agar and Mueller-Hinton agar supplemented with 2.5% NaCl containing 2 mg/L oxacillin and 20 mg/L aztreonam. Colonies that grew on the selective media were subcultured on blood agar and identified using MALDI-TOF mass spectrometry. Phenotypic methicillin resistance was tested using cefoxitin disk diffusion. Conventional PCR was used to detect mecA and mecC in phenotypically resistant isolates. Of 550 isolates that were obtained from mannitol salt agar plates and 10 isolates from Mueller-Hinton agar plates, 16 species of NASM accounted for 84% of staphylococci, while S. aureus accounted for the remaining 16%. Among S. aureus, 4 isolates from 4 farms (1.3%) demonstrated phenotypic resistance to methicillin resistance but none carried mecA or mecC genes. Among NASM, 45 isolates from 40 farms (13.3%) demonstrated phenotypic resistance to methicillin. However, only 13 NASM isolates (7 Mammaliicoccus sciuri, 2 Staphylococcus haemolyticus, 1 Mammaliicoccus fleuretti, 1 Staphylococcus epidermidis, 1 Staphylococcus saprophyticus, and 1 Staphylococcus hyicus) from 13 farms were positive for mecA, whereas all were negative for mecC. Thus, the prevalence of mecA-positive NASM in BTM was 4.3%. Based on molecular results, this study demonstrated a low prevalence of methicillin resistance NASM from BTM samples collected from farms in the Upper Midwest. Dairy farms that contained ≤200 lactating cows and had swine located on the farm had a higher prevalence of methicillin-resistant NASM than smaller farms that did not contain swine.

Novel T4 bacteriophage and royal jelly infused disinfectant versus E. coli compared to QACs

Antimicrobial resistance is an increasingly worsening phenomenon in the 21st century having resulted in thousands of deaths per year. Increases in the diffusion of antimicrobial resistance in gram-negative bacteria and prevalence of specific genes leading to resistance have been linked to an excessive usage of quaternary ammonium compounds (QACs) in gram-negative bacteria such as Escherichia coli. This experiment aims to develop a novel disinfectant solution (T4MRJP) that utilizes the entero-bacteriophage t4 and nine major royal jelly proteins (MRJPs) to inhibit the growth of E. coli on a MHA (Mueller Hinton Agar) growth medium. In the experiment, the Kirby Bauer Disk Diffusion Assay was first applied on six MHA plates inoculated with 36 evenly distributed susceptibility disks containing different concentrations of solution for three QAC groups, a positive t4 bacteriophage group, and two T4 groups at 90% and 98% dilution respectively. Results demonstrated a strong positive correlation between the increases of concentration to demonstrated inhibition but a lack of statistical significance between the T4 and QAC groups in regards to the proposed hypothesis. However, the diluted T4 group was just as effective as the QAC groups at inhibiting bacterial growth, especially at higher concentrations of the administered solution. In a second trial, however, the T4MRJP (Major royal jelly protein) cocktail was significantly less effective than the experimented QAC groups compared to the bacteriophage alone.

Assessment of the Antimicrobial Effectiveness of Herbal Root Canal Irrigants (Propolis, Triphala, and Aloe Vera) and Chlorhexidine Against Enterococcus Faecalis.

Complete microbial eradication from the root canal and 3-dimensional obturation of the canal space are necessary for an efficient root canal procedure. The current research was conducted to assess the antimicrobial effectiveness of herbal root canal irrigants and Chlorhexidine against Enterococcus faecalis. The brain heart infusion (BHI) broth was used to grow the E. faecalis (ATCC) bacterial culture overnight before it was inoculated onto Mueller-Hinton agar plates. Agar-well diffusion was used to measure antibacterial inhibition. Respective propolis, Triphala, aloe vera, and chlorhexidineirrigants were added to the appropriate wells in agar plates and incubated for 24 hours at 37°C. Each well's bacterial inhibition zone was measured and recorded. Statistics were used to tabulate and analyze the results. Chlorhexidine indicated the maximum inhibitory zone againstE. faecalis, subsequently propolis and Triphala, and the lowest by A. vera extract. Propolis, Triphala, and aloe vera were tested herbal remedies that demonstrated an inhibitory zone againstE. faecalis. These irrigants are therefore, suitable for use as root canal irrigating solutions.

IN VITRO ANTIBACTERIAL ACTIVITY OF EUCALYPTUS (Melaleuca leucadendra) OIL AGAINST METHICILLIN-RESISTANT Staphylococcus aureus (MRSA)

Highlights The use of eucalyptus oil is natural and risk-free. It has a lengthy history of use as a traditional medicine in Asia, including Indonesia. It has been demonstrated that eucalyptus oil possesses antibacterial activity against MRSA, and this activity was controlled by the oil's concentration. Abstract Background: Eucalyptus (Melaleuca leucadendra) oil is used by Indonesians as an herbal medicine. Eucalyptus containing 1,8-cineol at 72.30% is expected to be used as an antibacterial. Objective: The study aimed to assess the antibacterial activity of eucalyptus oil against Methicillin-resistant Staphylococcus aureus (MRSA) bacteria in vitro. Material and Method: The materials used were eucalyptus oil (M. leucadendra) in various concentrations with ethyl acetate as solvent. The research method used was the agar-well diffusion assay. The MRSA was suspended to 0.5 McFarland turbidity. The MRSA suspension was thoroughly swabbed onto the surface of the Mueller-Hinton agar plate. The wells were made with a diameter of 0.6 mm on Muller-Hinton agar aseptically and 100 µl of eucalyptus oil was put into the well using a micropipette and incubated for 24 hours at 37°C. The diameter of the inhibition zone was measured with a caliper. Statistical analysis using the SPSS software edition 23. Result: Eucalyptus oil solution starting from a concentration of 10% to 100% had an antibacterial response, which could be seen by the formation of a bacterial inhibition zone around the eucalyptus oil (M. leucadendra) wells. The inhibition ability of eucalyptus oil against MRSA bacteria was greatest at a concentration of 90% with an inhibition zone of 31.26 mm. It was found that the concentration of eucalyptus oil affected the diameter of the bacterial inhibition area. Conclusion: Eucalyptus oil has been shown to have antibacterial activity against MRSA and was influenced by the concentration of the oil.

Identification of Bacterial Isolates and Their Antimicrobial Susceptibility Pattern from Wound/Pus Sample in a Tertiary Care Hospital, Gwalior, India

Objective The goal of this investigation was to look at the frequency and dispersal of bacteria isolated from pus/wound, as well as their susceptibility patterns. Materials and Methods A study was conducted on 175 patients who provided pus and/or wound discharge samples in different wards (outpatient department or inpatient department). MacConkey agar and blood agar plates were immediately inoculated with samples and incubated at 37°C for 24 hours. The Gram stain and biochemical tests were used to identify all isolates after incubation. Kirby–Bauer's disc diffusion method was used to perform sensitivity tests on Mueller–Hinton agar plates. Results This study covered 175 patients, with a bacterial isolation rate of 102 (58.28%). Males outnumbered females in the samples (M:F = 1.8:1), with a median age of 45 years as majority were in the age group of 40 to 60 years which was 41 (40.20%). Total 90.1% samples showed monomicrobial infection, whereas 9.8% showed polymicrobial infection, and total 112 bacterial strains were isolated. Conclusion Escherichia coli was the most prevalent isolate in present investigation, followed by Pseudomonas aeruginosa. Chloramphenicol is the only antibiotic which is effective for both gram-negative bacilli and gram-positive cocci. This report's susceptibility statistic may be worth considering for developing empiric treatment regimens for pyogenic infections.

Evaluation of a new rapid immunochromatographic assay for the detection of GES-producing Gram-negative bacteria.

As carbapenemase-producing Enterobacterales are increasingly reported worldwide, their rapid detection is crucial to reduce their spread and prevent infections and outbreaks. Lateral flow immunoassays (LFIAs) have become major tools for the detection of carbapenemases. However, as for most commercially available assays, only the five main carbapenemases are targeted. Here, we have developed and evaluated an LFIA prototype for the rapid and reliable detection of the increasingly identified GES-type β-lactamases. The GES LFIA was validated on 103 well-characterized Gram-negative isolates expressing various β-lactamases grown on Mueller-Hinton (MH) agar, chromogenic, and chromogenic/selective media. The limit of detection of the assay was 106 cfu per test with bacteria grown on MH agar plates. GES LFIA accurately detected GES-type β-lactamases irrespective of the culture media and the bacterial host. The GES LFIA was not able to distinguish between GES-ESBLs and GES-carbapenemases. Because GES enzymes are still rare, their detection as an ESBL or a carbapenemase remains important, especially because extensive use of carbapenems to treat ESBL infections may select for GES variants capable of hydrolysing carbapenems. The GES LFIA is efficient, rapid and easy to implement in the routine workflow of a clinical microbiology laboratory for the confirmation of GES-type β-lactamases. Combining it with immunochromatographic assays targeting the five main carbapenemases (KPC, NDM, VIM, IMP and OXA-48) would improve the overall sensitivity for the most frequently encountered carbapenemases and ESBLs, especially in non-fermenters.

Listeria monocytogenes Isolates from Meat Products and Processing Environment in Poland Are Sensitive to Commonly Used Antibiotics, with Rare Cases of Reduced Sensitivity to Ciprofloxacin.

Antibiotic resistance is a global health problem, causing not only an increased mortality rate of bacterial infections but also economic losses due to, among other reasons, the need for longer hospital stays. Listeria monocytogenes is one of the foodborne pathogens with the ability to induce a serious illness called listeriosis, with approximately 20-30% fatal outcomes. The treatment regimen of listeriosis in humans includes the administration of antibiotics (in most cases, ampicillin or trimethoprim with sulfamethoxazole in case of allergies to β-lactams), so the resistance of this pathogen to antibiotics can potentially lead to increased mortality. The antibiotic sensitivity status of n = 153 L. monocytogenes isolates originating from meat food samples (raw and processed) and meat-processing environment (both contacting and non-contacting with food) collected between October 2020 and November 2021 in Poland was examined in this study. Susceptibility to antibiotics was determined using the disc diffusion method on Mueller-Hinton agar plates. All collected samples were susceptible to 9 antibiotics: ampicillin (10 µg), chloramphenicol (30 µg), erythromycin (15 µg), gentamicin (10 µg), penicillin (10 IU), streptomycin (10 µg), sulfamethoxazole/trimethoprim (1.25/23.75 µg), tetracycline (30 µg) and vancomycin (30 µg). Some of the isolates (n = 10; 6.5%) showed reduced susceptibility to ciprofloxacin (5 µg), which was classified as an intermediate response. All these ten isolates were collected from surfaces contacting with food in food-processing facilities.