Comparative evaluation of methods for the detection of biofilm formation in coagulase-negative staphylococci and correlation with antibiogram

Coagulase-Negative Staphylococci Determined as Blood Culture Contamination Have High Virulence Characteristic Including Transfer of Antibiotic Resistance Determinants to Staphylococcus aureus and Escherichia coli

This study aimed to evaluate the virulence of 36 clinical isolates estimated as blood culture contaminants (BCCs). MALDI-TOF MS classified all isolates as coagulase-negative staphylococci (CoNS) with the highest percentage of S. epidermidis (77.78%). All tested strains formed biofilms with greater ability at room temperature than 37 °C. CoNS were sensitive to vancomycin (0% resistance) and had relatively low resistance to linezolid and rifampicin (8.33 and 22.22% resistance). The highest resistance was observed for penicillin (94.44%). Moreover, we observed the transfer of antibiotic resistance genes from the tested CoNS to S. aureus and even to E. coli, although with lower efficiency. CoNS in planktonic form were completely combated by antiseptics after 10 and 60 s exposition, and activity against biofilms was time-dependent. The complete elimination of biofilms was observed after a 180 s exposure to Kodan and CITROclorex, and this exposure to Rivanol and Octenidyne showed still viable cells (>0.9 log CFU/mL). Our findings showed that a careful selection of antiseptics and extending the exposure time before blood collection can reduce the occurrence of blood culture contamination. However, our most important finding is the indication that CoNS naturally occurring on human skin and mucous membranes exhibit antibiotic resistance, and what is more, determinants of antibiotic resistance are transferred to both closely related Gram-positive bacteria and phylogenetically distant Gram-negative bacteria. Thus, our findings shed new light on CoNS-they indicate the necessity of their control due to the effective transfer of mobile genetic elements harboring antibiotic resistance genes, which may contribute to the spread of resistance genes and deepening the antibiotic crisis.

Endophytic bacteria of Gracilaria edulis in combating human bacterial pathogens by PPDHMP - A crude to single molecule product development approach

Resistance in human bacterial pathogens and lack of novel antibiotic development has led to the need for new antibiotics. Therefore, the current study was focused on endophytic bacteria from Gracilaria edulis, an edible seaweed, capable of synthesizing novel bioactive compounds with potential applications in the inhibition of human pathogens. The endophyte, identified as Bacillus subtilis through 16S rRNA gene sequencing, exhibited significant antibacterial activity against bacterial human pathogens. Using GC-MS, FTIR and NMR the lead compound was identified as Pyrrolo[1,2-α] pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl) (PPDHMP). Optimized media composition using glucose, proline and valine significantly enhanced the production of PPDHMP which was observed by the increase in zone of inhibition. Molecular docking of PPDHMP indicated a high binding affinity to beta-lactamase, suggesting its potential as a beta-lactamase inhibitor. PPDHMP exhibited cell wall inhibitory activity and ADMET analysis revealed promising pharmacokinetic and toxicity profiles indicating its potential for further evaluation as an oral antibiotic candidate. Phytotoxicity assessments and hemolytic assay confirmed the non-toxic nature of the metabolites produced. This research highlights the immense potential of marine endophytes in addressing the escalating issue of antibiotic resistance and paves the way for innovative solutions in antimicrobial therapy.

Silver Nanoparticles Functionalized with Polymeric Substances to Reduce the Growth of Planktonic and Biofilm Opportunistic Pathogens

The global rise in antimicrobial resistance, particularly among ESKAPE pathogens, has intensified the demand for alternative therapeutic strategies. Silver nanoparticles (AgNPs) have exhibited broad-spectrum antimicrobial activity and represent a promising approach to combat multidrug-resistant infections. This study aimed to synthesize and functionalize AgNPs using various polymeric agents-ethylene glycol (EG), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and their combinations-and to evaluate their antimicrobial and antibiofilm efficacy against clinically relevant bacterial strains. AgNPs were synthesized via chemical reduction and functionalized as Ag@EG, Ag@PEG, Ag@EG/PVP, and Ag@PEG/PVP. A total of 68 clinical isolates-including Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus lugdunensis, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa-were tested. Antimicrobial susceptibility was assessed using disc diffusion and broth microdilution assays, while antibiofilm activity was evaluated via the crystal violet method. Among all tested formulations, Ag@EG/PVP exhibited the highest antimicrobial and antibiofilm activity, with notably low minimum inhibitory concentrations (MIC50) and minimum biofilm eradication concentrations (MBEC50) for Ps. aeruginosa and K. pneumoniae. In contrast, AgNPs functionalized with PEG or EG alone showed limited efficacy. Biofilm-forming isolates, particularly Staphylococcus spp., required higher concentrations for inhibition. These results highlight the critical role of functionalization in modulating the antimicrobial properties of AgNPs, with Ag@EG/PVP demonstrating potent activity against both planktonic and biofilm-associated multidrug-resistant bacteria. Overall, this study supports further developing AgNPs-based formulations as adjuncts or alternatives to conventional antibiotics, particularly for managing biofilm-related infections. Future research should focus on formulation optimization, safety assessment, and translational potential.

A Comprehensive Phenotypic Characterization of Biofilm-Producing Coagulase-Negative Staphylococci: Elucidating the Complexities of Antimicrobial Resistance and Susceptibility

Background Coagulase-negative staphylococci (CoNS) have emerged as significant pathogens in nosocomial infections, particularly in bloodstream infections and individuals linked to embedded therapeutic devices. CoNS predominantly affects immunocompromised or debilitated patients. Additionally, individuals with medical indwelling devices, such as a catheter for the urinary tract, valves for the cardiovascular system, pacemakers, and prosthetic joints, should receive medical attention. As a result of the organism's evolving resistance to multiple antibiotics, managing CoNS infections is becoming increasingly challenging. The formation of biofilms is a key factor contributing to the pathogenicity and antimicrobial resistance of CoNS, complicating treatment efforts and the resolution of infections. Aim The aim of this study is to identify CoNS species, examine their biofilm production, and evaluate their resistance to antibiotics. Materials and methods A cross-sectional study was conducted on patients admitted to the Microbiology Department at Krishna Hospital, Karad. Clinical samples included the following: blood, pus, urine, sputum, endotracheal tube aspirate, high vaginal swab, and central venous catheter. Results The occurrence of coagulase-negative Staphylococcus across the range of clinical samples consisted of blood (61 isolates, 75.3%), pus (seven isolates, 8.6%), urine (six isolates, 7.4%), sputum (three isolates, 3.7%), endotracheal tubes (two isolates, 2.5%), and high vaginal swab and central venous catheter (one isolate (1.2%) each). The most often isolated species was Staphylococcus haemolyticus (35 isolates, 43.2%) followed by Staphylococcus epidermidis (22 isolates, 27.2%) and Staphylococcus hominis (12 isolates, 14.8%). We assessed the production of biofilms using Congo red agar, with 62 isolates (76.5%) demonstrating biofilm formation. Among these, S. haemolyticus  was the predominant species exhibiting biofilm production, with 29 isolates (46.8%) testing positive. This was followed by S. epidermidis  with 19 isolates (30.7%) and S. hominis  with nine isolates (14.5%). Conclusion The results of antibiotic susceptibility tests revealed multidrug resistance, with most isolates showing a high level of susceptibility to linezolid (84%) and complete resistance to penicillin. These findings highlight the clinical implications of limited treatment options and the need for alternative therapies, such as linezolid, in managing infections caused by coagulase-negative staphylococci.

Piezoelectric biosensor with dissipation monitoring enables the analysis of bacterial lytic agent activity

Antibiotic-resistant strains of Staphylococcus aureus pose a significant threat in healthcare, demanding urgent therapeutic solutions. Combining bacteriophages with conventional antibiotics, an innovative approach termed phage-antibiotic synergy, presents a promising treatment avenue. However, to enable new treatment strategies, there is a pressing need for methods to assess their efficacy reliably and rapidly. Here, we introduce a novel approach for real-time monitoring of pathogen lysis dynamics employing the piezoelectric quartz crystal microbalance (QCM) with dissipation (QCM-D) technique. The sensor, a QCM chip modified with the bacterium S. aureus RN4220 ΔtarM, was utilized to monitor the activity of the enzyme lysostaphin and the phage P68 as model lytic agents. Unlike conventional QCM solely measuring resonance frequency changes, our study demonstrates that dissipation monitoring enables differentiation of bacterial growth and lysis caused by cell-attached lytic agents. Compared to reference turbidimetry measurements, our results reveal distinct alterations in the growth curve of the bacteria adhered to the sensor, characterized by a delayed lag phase. Furthermore, the dissipation signal analysis facilitated the precise real-time monitoring of phage-mediated lysis. Finally, the QCM-D biosensor was employed to evaluate the synergistic effect of subinhibitory concentrations of the antibiotic amoxicillin with the bacteriophage P68, enabling monitoring of the lysis of P68-resistant wild-type strain S. aureus RN4220. Our findings suggest that this synergy also impedes the formation of bacterial aggregates, the precursors of biofilm formation. Overall, this method brings new insights into phage-antibiotic synergy, underpinning it as a promising strategy against antibiotic-resistant bacterial strains with broad implications for treatment and prevention.

Antibiofilm Mechanisms of the Helical G3 Peptide against Staphylococcus epidermidis

Antibacterial peptides (ABPs) have been recognized as promising alternatives to conventional antibiotics due to their broad antibacterial spectrum, high antibacterial activity, and low possibility of inducing bacterial resistance. However, their antibiofilm mechanisms have not yet reached a consensus. In this study, we investigated the antibiofilm activity of a short helical peptide G3 against Staphylococcus epidermidis, one of the most important strains of medical device contamination. Studies show that G3 inhibits S. epidermidis biofilm formation in a variety of ways. In the initial adhesion stage, G3 changes the properties of bacterial surfaces, such as charges, hydrophobicity, and permeability, by rapidly binding to them, thus interfering with their initial adhesion. In the mature stage, G3 prefers to target extracellular polysaccharides, leading to the death of outside bacteria and the disruption of the three-dimensional (3D) architecture of the bacterial biofilm. Such efficient antibiofilm activity of G3 endows it with great potential in the treatment of infections induced by the S. epidermidis biofilm.

Bacteriology of endotracheal tube biofilms and antibiotic resistance: a systematic review

Bacteria commonly adhere to surfaces and produce polymeric material to encase the attached cells to form communities called biofilms. Within these biofilms, bacteria can appear to be many times more resistant to antibiotics or disinfectants. This systematic review explores the prevalence and microbial profile associated with biofilm production of bacteria isolated from endotracheal tubes and its associations with antimicrobial resistance. A comprehensive search was performed on databases PubMed, Embase, and Google Scholar for relevant articles published between 1st January 2000 and 31st December 2022. The relevant articles were exported to Mendeley Desktop 1.19.8 and screened by title and abstract, followed by full text screening based on the eligibility criteria of the study. Quality assessment of the studies was performed using the Newcastle-Ottawa Scale (NOS) customized for cross-sectional studies. Furthermore, the prevalence of antimicrobial resistance in biofilm-producers isolated from endotracheal tube specimens was investigated. Twenty studies encompassing 981 endotracheal tubes met the eligibility criteria. Pseudomonas spp. and Acinetobacter spp. were predominant isolates among the biofilm producers. These biofilms provided strong resistance against commonly used antibiotics. The highest resistance rate observed in Pseudomonas spp. was against fluoroquinolones whereas the least resistance was seen against piperacillin-tazobactam. A similar trend of susceptibility was observed in Acinetobacter spp. with a very high resistance rate against fluoroquinolones, third-generation cephalosporins and carbapenems. In conclusion, endotracheal tubes were associated with colonization by biofilm forming bacteria with varying levels of antimicrobial resistance. Biofilms may promote the occurrence of recalcitrant infections in endotracheal tubes which need to be managed with appropriate protocols and antimicrobial stewardship. Research focus should shift towards meticulous exploration of biofilm-associated infections to improve detection and management.

Assessment of four in vitro phenotypic biofilm detection methods in relation to antimicrobial resistance in aerobic clinical bacterial isolates

INTRODUCTION

The lack of standardized methods for detecting biofilms continues to pose a challenge to microbiological diagnostics since biofilm-mediated infections induce persistent and recurrent infections in humans that often defy treatment with common antibiotics. This study aimed to evaluate diagnostic parameters of four in vitro phenotypic biofilm detection assays in relation to antimicrobial resistance in aerobic clinical bacterial isolates.

METHODS

In this cross-sectional study, bacterial strains from clinical samples were isolated and identified following the standard microbiological guidelines. The antibiotic resistance profile was assessed through the Kirby-Bauer disc diffusion method. Biofilm formation was detected by gold standard tissue culture plate method (TCPM), tube method (TM), Congo red agar (CRA), and modified Congo red agar (MCRA). Statistical analyses were performed using SPSS version 17.0, with a significant association considered at p<0.05.

RESULT

Among the total isolates (n = 226), TCPM detected 140 (61.95%) biofilm producers, with CoNS (9/9) (p<0.001) as the predominant biofilm former. When compared to TCPM, TM (n = 119) (p<0.001) showed 90.8% sensitivity and 70.1% specificity, CRA (n = 88) (p = 0.123) showed 68.2% sensitivity and 42% specificity, and MCRA (n = 86) (p = 0.442) showed 65.1% sensitivity and 40% specificity. Juxtaposed to CRA, colonies formed on MCRA developed more intense black pigmentation from 24 to 96 hours. There were 77 multi-drug-resistant (MDR)-biofilm formers and 39 extensively drug-resistant (XDR)-biofilm formers, with 100% resistance to ampicillin and ceftazidime, respectively.

CONCLUSION

It is suggested that TM be used for biofilm detection, after TCPM. Unlike MCRA, black pigmentation in colonies formed on CRA declined with time. MDR- and XDR-biofilm formers were frequent among the clinical isolates.

Phenotypic and Genotypic Characterization of Methicillin Resistance in Staphylococci Isolated from an Egyptian University Hospital

Methicillin-resistant in Staphylococci is a serious public health issue. It is mostly encoded by the mecA gene. The mecC gene is a new mecA analog responsible for resistance to methicillin in some Staphylococcal clinical isolates. This mecC gene is still underestimated in Egypt. The aim of the current study was to detect mecA and mecC genes in clinical Staphylococci isolates from a tertiary care university hospital in Egypt compared to the different phenotypic methods. A total of 118 Staphylococcus aureus (S. aureus) and 43 coagulase-negative Staphylococci (CoNS) were identified from various hospital-acquired infections. Methicillin resistance was identified genotypically using the PCR technique and phenotypically using the cefoxitin disc diffusion test, oxacillin broth microdilution and the VITEK2 system in all Staphylococcal isolates. The mecA gene was detected in 82.2% of S. aureus and 95.3% of CoNS isolates, while all of the isolates tested negative for the mecC gene. Interestingly, 30.2% of CoNS isolates showed the unique character of inducible oxacillin resistance, being mecA-positive but oxacillin-susceptible (OS-CoNS). The dual use of genotypic and phenotypic methods is highly recommended to avoid missing any genetically divergent strains.

Molecular Detection and Characterization of the Staphylococcus epidermidis and Staphylococcus haemolyticus Isolated from Hospitalized Patients and Healthcare Workers in Iran

Background

The present study is aimed at surveying the antibiotics resistance profile, biofilm formation ability, staphylococcal cassette chromosome mec (SCCmec) types, and molecular epidemiology of Staphylococcus epidermidis and Staphylococcus haemolyticus isolated from hospitalized patients and healthcare workers in four teaching hospitals in Iran.

Methods

In total, 43 Staphylococcus epidermidis and 12 Staphylococcus haemolyticus were isolated from hospitalized patients, and 19 Staphylococcus epidermidis and 7 Staphylococcus haemolyticus isolated from healthcare workers were included in the present study. The antimicrobial resistance profile of isolates was determined using the disk diffusion method. Moreover, the resistance of isolates to methicillin was identified using the cefoxitin disk diffusion test. The microtiter-plate test was used for quantifying biofilm formation. Moreover, the frequency of icaA and icaD genes was determined using PCR assay. The molecular epidemiology of methicillin-resistant isolates was determined using SCCmec typing and pulsed-field gel electrophoresis methods.

Results

Among all coagulase-negative staphylococci isolates, the highest resistance rate (81.5%) was seen for cefoxitin and cotrimoxazole. All of the isolates were susceptible to linezolid. Out of the 66 mecA-positive isolates, the most common SCCmec type was the type I (n = 23; 34.8%) followed by type IV (n = 13; 19.7%). Using pulsed-field gel electrophoresis (PFGE) assay, 27 PFGE types including 14 common types and 13 singletons were obtained among 51 methicillin-resistant S. epidermidis (MRSE) isolates. Moreover, among 12 methicillin-resistant S. haemolyticus (MRSH) isolates, 8 PFGE types were detected, of which 5 PFGE types were singletons.

Conclusion

The high rate of resistance to antibiotics as well as the possibility of cross-infection shows the importance of a pattern shift in the management and controlling programs of coagulase-negative staphylococci, especially in healthcare centers. Clinical trial registration. The present study is not a clinical trial study. Thus, a registration number is not required.

Clinical and Bacteriological Analyses of Biofilm-Forming Staphylococci Isolated from Diabetic Foot Ulcers

Background

Diabetes mellitus is a chronic disease that is associated with increased morbidity and mortality. Unfortunately, foot ulcers and amputations due to diabetes are very common in developing countries. The purpose of this study was to characterize the clinical presentation of diabetic foot ulcer (DFU) infections, isolate the causative agent, and analyze the biofilm formation and distribution of biofilm-related genes among isolated Staphylococci.

Material and Methods

The study included 100 diabetic patients suffering from DFUs attending Assiut University Hospital. Swabs were collected and antimicrobial susceptibility testing of the isolates was performed. Biofilm formation was tested phenotypically among staphylococcal isolates and the frequency of different biofilm genes was analyzed by PCR. Clinical presentations of diabetic foot ulcers were correlated with bacterial genetic characteristics. Spa types were determined using DNA Gear-a software.

Results

Microbiological analysis showed that 94/100 of the DFUs were positive for bacterial growth. The majority of infections were polymicrobial (54%, n=54/100). Staphylococci were the most commonly detected organisms, of which S. aureus represented 37.5% (n=24/64), S. haemolyticus 23.4% (n=15/64), S. epidermidis 34.3% (n=22/64) and other CNS 4.7% (n=3/64). Interestingly, co-infection with more than one species of Staphylococci was observed in 17.1% (n=11/64) of samples. A high level of antibiotic resistance was observed, where 78.1% (n=50/64) of Staphylococci spp were multidrug-resistant (MDR). Phenotypic detection showed that all isolated Staphylococci were biofilm-formers with different grades. Analysis of biofilm-forming genes among Staphylococci showed that the most predominant genes were icaD, spa, and bap. Isolates with a higher number of biofilm-related genes were associated with strong biofilm formation. Sequencing of the spa gene in S. aureus showed that our isolates represent a collection of 17 different spa types.

Conclusion

The majority of DFUs in our hospital are polymicrobial. Staphylococci other than S.aureus are major contributors to infected DFUs. MDR and biofilm formation are marked among isolates, which is paralleled by the presence of different categories of virulence-related genes. All severely infected wounds were associated with either strong or intermediate biofilm formers. The severity of DFU is directly related to the number of biofilm genes.

Cec4-Derived Peptide Inhibits Planktonic and Biofilm-Associated Methicillin Resistant Staphylococcus epidermidis

Staphylococcus epidermidis is part of the normal microbiota that colonizes the skin and mucosal surfaces of human beings. Previous studies suggested that S. epidermidis possessed low virulence, but recent studies confirmed that it can acquire high virulence from Staphylococcus aureus and with the increasing detection of methicillin-resistant S. epidermidis. It has become a major pathogen of graft-associated and hospital-acquired infections. In previous studies, we modified the antimicrobial peptide Cec4 (41 amino acids) and obtained the derived peptide C9 (16 amino acids) showing better antimicrobial activity against S. epidermidis with an MIC value of 8 μg/mL. The peptide has rapid bactericidal activity without detectable high-level resistance, showing certain inhibition and eradication ability on S. epidermidis biofilms. The damage of cell membrane structures by C9 was observed by scanning emission microscopy (SEM) and transmission electron microscopy (TEM). In addition, C9 altered the S. epidermidis cell membrane permeability, depolarization levels, fluidity, and reactive oxygen species (ROS) accumulation and possessed the ability to bind genomic DNA. Analysis of the transcriptional profiles of C9-treated cells revealed changes in genes involved in cell wall and ribosome biosynthesis, membrane protein transport, oxidative stress, and DNA transcription regulation. At the same time, the median lethal dose of C9 in mice was more than 128 mg/kg, and the intraperitoneal administration of 64 mg/kg was less toxic to the liver and kidneys of mice. Furthermore, C9 also showed a certain therapeutic effect on the mouse bacteremia model. In conclusion, C9 may be a candidate drug against S. epidermidis, which has the potential to be further developed as an antibacterial therapeutic agent. IMPORTANCE S. epidermidis is one of the most important pathogens of graft-related infection and hospital-acquired infection. The growing problem of antibiotic resistance, as well as the emergence of bacterial pathogenicity, highlights the need for antimicrobials with new modes of action. Antimicrobial peptides have been extensively studied over the past 30 years as ideal alternatives to antibiotics, and we report here that the derived peptide C9 is characterized by rapid bactericidal and antibiofilm activity, avoiding the development of resistance by acting on multiple nonspecific targets of the cell membrane or cell components. In addition, it has therapeutic potential against S. epidermidis infection in vivo. This study provides a rationale for the further development and application of C9 as an effective candidate antibiotic.

Biofilm formation and antibiotic resistance among Coagulase Negative Staphylococcus species isolated from central venous catheters of intensive care unit patients

PURPOSE

This study was conducted to determine the biofilm formation of coagulase negative Staphylococcus species (CoNS) isolated from patients with catheter related blood stream infection (CRBSI) and colonized central venous catheters (CVC) and their antibiotic susceptibility patterns and in situ biofilm formation of CVC tips.

METHODS

Eighty-two CoNS isolated from intensive care unit (ICU) patients with CRBSI (n ​= ​8) or colonized CVC (n ​= ​74) were included. Species identification and antibiotic susceptibility test were done. All isolates were screened for biofilm formation using crystal violet and 3-(4,5-dimethylthiazole-2-yl)-2-5-diphenyl-2H-tetrazolium bromide (MTT) assays and categorized as strong or moderate biofilm formers. CVC tips were subjected to crystal violet stain and scanning electron microscopy (SEM) to detect in-situ biofilm formation.

RESULTS

Staphylococcus haemolyticus (n ​= ​34; 41%) was the commonest to cause both CRBSI and CVC colonization. All 82 CoNS produced biofilms. Among them 77 (93.90%) were strong biofilm formers including all from CRBSI patients and 05 (6.10%) were moderate biofilm formers as detected by both methods. SEM showed bacteria adhered to surfaces of CVC tips with microbial-aggregates embedded in extracellular matrix. Mean crystal violet absorbance of CVC from CRBSI patients (0.6628) was significantly higher than colonized CVC (mean value 0.5592) (p ​= ​0.030). S. haemolyticus showed higher resistance to cloxacillin compared to other CoNS (p ​= ​0.039).

CONCLUSION

Majority of CoNS isolated were strong biofilm formers. In-situ biofilm formation on CVC tips were significantly evident in CRBSI patients compared to CVC colonized patients. S. haemolyticus is the commonest to cause both CRBSI and CVC colonization and shows significantly higher cloxacillin resistance rate.

Baicalin acts as an adjuvant to potentiate the activity of azithromycin against Staphylococcus saprophyticus biofilm: an in vitro, in vivo, and molecular study

Staphylococcus saprophyticus is frequently involved in various difficult-to-treat infections due to the formation of biofilms. To identify useful antibiofilm strategies, this study explored the efficacy and mechanism of baicalin in enhancing the ability of azithromycin against multidrug-resistant Staphylococcus saprophyticus-Liu-2016-Liyang, China-francolin (MDRSS) biofilms in vitro and in vivo. When azithromycin was used in combination with baicalin, the minimum inhibitory concentration in biofilm (MICB) for azithromycin decreased 4- to 512-fold. Compared with the azithromycin and baicalin groups, the combination of azithromycin and baicalin could not reduce the biofilm biomass, but the dispersion rates of biofilm were decreased and the bactericidal ability was increased. Furthermore, the relative transcript levels of WalK/R system-related genes were upregulated by the addition of baicalin or azithromycin plus baicalin compared with that of the azithromycin and blank control groups. The strong correlation relationship between the WalK/R system and the bactericidal index demonstrated that baicalin enhanced the bactericidal effect of azithromycin on MDRSS biofilms by modulating the WalK/R system. In the mouse cutaneous infection model, the combination of azithromycin and baicalin succeeded in eradicating MDRSS and decreasing pathological injuries. This study indicated that baicalin has the potential to be an adjuvant to enhance the antimicrobial activity of azithromycin against MDRSS in the biofilm form by modulating the WalK/R system.

Role of Biofilm in Bacterial Infection and Antimicrobial Resistance

Biofilm refers to the complex, sessile communities of microbes found either attached to a surface or buried firmly in an extracellular matrix as aggregates. Microbial flora which produces biofilm manifests an altered growth rate and transcribes genes that provide them resistance to antimicrobial and host immune systems. Biofilms protect the invading bacteria against the immune system of the host via impaired activation of phagocytes and the complement system. Biofilm-producing isolates showed greater multidrug resistance than non-biofilm producers. Biofilm causes antibiotic resistance through processes like chromosomally encoded resistant genes, restriction of antibiotics, reduction of growth rate, and host immunity. Biofilm formation is responsible for the development of superbugs like methicillin-resistant Staphylococcus aureus, vancomycin-resistant Staphylococcus aureus, and metallo-beta-lactamase producing Pseudomonas aeruginosa. Regular monitoring of antimicrobial resistance and maintaining hygiene, especially in hospitalized patients are required to control biofilm-related infections in order to prevent antimicrobial resistance.

Biofilm Detection by a Fiber-Tip Ball Resonator Optical Fiber Sensor

Bacterial biofilms are one of the most important challenges that modern medicine faces due to the difficulties of diagnosis, antibiotic resistance, and protective mechanisms against aggressive environments. For these reasons, methods that ensure the inexpensive and rapid or real-time detection of biofilm formation on medical devices are needed. This study examines the possibilities of using optical- and fiber-based biosensors to detect and analyze early bacterial biofilms. In this study, the biofilm-forming model organism Pseudomonas aeruginosa was inoculated on the surface of the optical sensor and allowed to attach for 2 h. The biosensors were made by a fiber-tip ball resonator, fabricated through a CO2 laser splicer on a single-mode fiber, forming a weak reflective spectrum. An optical backscatter reflectometer was used to measure the refractive index detected by the sensors during different growth periods. The early biofilm concentration was determined by crystal violet (CV) binding assay; however, such a concentration was lower than the detection limit of this assay. This work presents a new approach of biofilm sensing in the early attachment stage with a low limit of detection up to 10−4 RIU (refractive index units) or 35 ± 20 × 103 CFU/mL (colony formed units).

Exploring the Biofilm Formation Capacity in S. pseudintermedius and Coagulase-Negative Staphylococci Species

The ability of biofilm formation seems to play an important role in the virulence of staphylococci. However, studies reporting biofilm formation of coagulase-negative staphylococci isolated from animals are still very scarce. Thus, we aimed to evaluate the biofilm-forming capacity of CoNS and S. pseudintermedius isolated from several animal species and to investigate the effect of conventional antimicrobials on biofilm reduction. A total of 35 S. pseudintermedius and 192 CoNS were included. Biofilm formation was accessed by the microtiter plate assay and the biofilms were stained by crystal violet. Association between biofilm formation and staphylococci species and antimicrobial resistance was also performed. Biofilm susceptibility testing was performed with tetracycline and amikacin at the minimum inhibitory concentration (MIC) and 10 × MIC. The metabolic activity of the biofilm cells after antimicrobial treatment was accessed by the XTT assay. All isolates formed biofilm, with S. urealyticus producing the most biofilm biomass and S. pseudintermedius producing the least biomass. There was a positive association between biofilm formation and multidrug resistance as well as resistance to individual antimicrobials. Neither tetracycline nor amikacin were able to eradicate the biofilm, not even at the highest concentration used. This study provides new insights into biofilm formation and the effects of antimicrobials on CoNS species.

Phenotypic and Molecular Detection of Slime Producing Staphylococcus Spp. Obtained from Blood Samples of Patients Undergoing Hematopoietic Stem-Cell Transplantation

Aim: to investigate the slime production in isolates of Staphylococcus spp., associated with bacteremia in patients after hematopoietic stem-cell transplantation (HSCT) and to determine the relationship between the slime production and ica genes carriage, as well as the correlation of ica and methicillin resistance.

Materials and methods: Between 2019 and 2020, twenty-one clinically significant Staphylococcus spp. isolates were obtained from blood cultures of 17 patients after HSCT. The species identification and the susceptibility to cefoxitin were determined by BD Phoenix M50. Two phenotypic tests (Congo red agar, CRA; Christensen’s method, TT) and PCR for icaA and icaD were used to detect slime production. A PCR method was also used to detect the mecA, mecC genes.

Results: In the studied group of 21 isolates (S. epidermidis, n = 12; S. haemolyticus, n = 4; S. hominis, n = 2; S. aureus, n = 3), the phenotypic tests were positive in 13 isolates. Ten isolates (47.6%) were identified as carriers of ica genes (S. epidermidis, n = 9, and S. haemolyticus, n = 1). Five isolates (23.8%) were detected as slime producers by all three methods. The mecA gene was identified in 18 isolates (85.7%). All ica positive isolates were also mecA carriers.

Conclusion: A relatively high proportion of the blood isolates of Staphylococcus spp. were slime producers, associ-ated with ica genes. A combination of both phenotypic and genetic methods should be used to detect alternative routes of slime production. The co-expression of ica and mecA is associ-ated with the occurrence of difficult-to-eradicate isolates.

Isolation and Identification of Biofilm-Producing, Drug-Resistant Coagulase Negative Staphylococci from a Hospital Environment in Northern Philippines

Healthcare-associated infections (HCAIs) are considered adverse outcomes of confinement in a healthcare facility. Biofilm-producing, drug-resistant bacteria have further aggravated the problem with HCAIs. This study determined the prevalence, antibiotic susceptibility, and biofilm phenotype of coagulase-negative staphylococci (CoNS) isolated from a hospital environment in Northern Philippines. The identification of CoNS species and the determination of antibiotic susceptibility were done using an automated assay. Biofilm production was detected using tissue culture plate (TCP) and Congo red agar (CRA) methods. Out of 220 surfaces and 26 air samples collected, 103 (41.9%) CoNS strains were isolated, predominated by S. epidermidis with 30.1% prevalence. The medical ward was found to have the highest prevalence of CoNS at 64%. The CoNS isolates exhibited a variable resistance profile; the highest was found against penicillin (97.1%) and oxacillin (54.3%). Isolates manifesting resistance to linezolid and vancomycin were also detected. From the 103 CoNS isolates, 52 (50.5%) biofilm producers were detected using the TCP method, and 39 (37.9%) were detected by the CRA method. Statistically significant difference was found between the biofilm biomass and the slime-producing pattern. This study revealed the prevalence of biofilm-producing, drug-resistant strains of CoNS in a Level 3 hospital in Northern Philippines. This warrants further enhancement of infection prevention and control programs to avert the emergence of more biofilm-producing, drug-resistant bacterial strains that could pose formidable threats to public health.

Reversal of Azithromycin Resistance in Staphylococcus saprophyticus by Baicalin

In recent years, the efficacy of antibiotics has been threatened by the evolution of bacterial resistance. We previously demonstrated that baicalin (Bac) showed synergies with azithromycin (Azm) against Azm-resistant Staphylococcus saprophyticus (ARSS). The aim of this study was to explore the roles of Bac in reversing the resistance of ARSS to Azm. The ARSS was sequentially passaged for 20 days with the sub-MIC (minimum inhibitory concentration) of Bac. The strain that recovered sensitivity to Azm was named Azm-sensitive S. saprophyticus (ASSS). The sub-MIC of Bac reversed the resistance of ARSS to Azm. The MIC of Azm against the ASSS strain was 0.488 mg/l, and it was stable within 20 passages. The highest rate of resistance reversal reached 3.09% after ARSS was exposed to 31.25 mg/l Bac for 20 days. Furthermore, semiquantitative biofilm and RT-PCR assays reflected that the ability of biofilm formation and the transcript levels of msrA, mphC, and virulence-associated genes in the ASSS strain were significantly lower than those of the ARSS strain (p < 0.05). Simultaneously, Azm delayed the start time of death, alleviated the injury of the kidney, and decreased the bacterial burden in organs and cytokine levels in mice infected with ASSS. In contrast, Azm did not have a good therapeutic effect on mice infected with ARSS. Therefore, Bac has the potential to be an agent that reversed the resistance of ARSS to Azm.

Dysbiosis in salivary bacterial diversity of postpartum females and its association with oral health problems and APOs

The present study investigates the dysbiosis in salivary bacterial diversity by culture-dependent and independent methods. Culturable aerobic and facultative anaerobic bacterial diversity was studied in saliva collected from 267 postpartum and 54 nonpregnant females by using standard microbiological methods. For unculturable bacterial diversity, DNA from saliva samples of four selected females was sequenced by targeting V4 region of 16S rRNA. In postpartum females, S. mutans was significantly more prevalent. Its colonization was also seen significant among females having gingivitis (P < 0.01), dental caries (P < 0.01), and in those giving birth to low weight baby. In postpartum group, 65.16% females were culture positive for Staphylococcus, 12.73% Gram positive rods, 10.48% N. meningitides, 6.36% K. pneumoniae, 5.61% Enterobacter species and 2.62% E. coli. Isolates showed high biofilm forming ability and antibiotic resistance. Upon analysis of unculturable bacterial diversity, a total of 16 phyla and 156 genera were observed. Alpha diversity was decrease in postpartum female having oral health issues with pre-term low weight birth, compared to females with full term birth. Bray-Curtis dissimilarity was highest between female with dental issues and different pregnancy outcomes. Bacterial diversity and abundance altered among females with different oral health conditions and pregnancy outcomes, and also have pathogenic potential.

Isolation and molecular identification of biofilm producing P. aeruginosa and K. pneumoniae from urinary tract infections patient urine sample

BACKGROUND

Recent years, multi drug resistant pathogens and their pathogenicity were increased worldwide due to unauthorized consumption of antibiotics. In addition, correlation between multi drug resistant bacteria and biofilm formation is heightened due to the production of more virulence behavior. There is no better identification methods are available for detection of biofilm producing gram negative bacteria.

MATERIALS AND METHODS

In this research work, multi drug resistant strains of Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were identified based on the specific antibiotics and third generation cephalosporin discs by disc diffusion assay. Subsequently, biofilm forming ability of selected pathogens were identified tissue culture plate and tube test. Based on the multi-drug resistant ability and biofilm production, the molecular identification of P. aeruginosa and K. pneumoniae were confirmed by PCR using universal primers.

RESULTS AND CONCLUSIONS

No zone of inhibition present around the discs of muller hinton agar plates were confirm, selected P. aeruginosa and K. pneumoniae strains were multi drug resistant pathogens. Performed third generation cephalosporin antibiotics were also highly sensitive to selected pathogens of P. aeruginosa and K. pneumoniae. Further, biofilm forming ability of selected P. aeruginosa and K. pneumoniae was confirmed by tissue culture plate and tube methods. Finally, molecular identification of P. aeruginosa and K. pneumoniae was named as P. aeruginosa and K. pneumoniae. Our result was conclude, selected P. aeruginosa and K. pneumoniae as biofilm producing pathogens and also highly resistant to current antibiotics.

Antibiotic Susceptibility, Biofilm Production, and Detection of mecA Gene among Staphylococcus aureus Isolates from Different Clinical Specimens

The increasing incidence of methicillin-resistant and biofilm-forming S. aureus isolates in hospital settings is a gruesome concern today. The main objectives of this study were to determine the burden of S. aureus in clinical samples, assess their antibiotic susceptibility pattern and detect biofilm formation and mecA gene in them. A total of 1968 different clinical specimens were processed to isolate S. aureus following standard microbiological procedures. Antibiotic susceptibility test of the isolates was performed by Kirby–Bauer disc-diffusion method following CLSI guidelines. Biofilm was detected through tissue culture plate method. Methicillin-resistant S. aureus (MRSA) isolates were screened using cefoxitin (30 µg) discs and mecA gene was amplified by conventional polymerase chain reaction (PCR). Of 177 bacterial growth, the prevalence of S. aureus was 15.3% (n = 27). MRSA were 55.6% (15/27) and 44% (12/27) exhibited multidrug resistance (MDR). There was no significant association between methicillin resistance and MDR (p > 0.05). Both MRSA and MSSA were least sensitive to penicillin (100%, 75%) followed by erythromycin (86.6%, 66.6%). Most of the MRSA (93.4%) were susceptible to tetracycline. All S. aureus isolates were biofilm producers—19 (70%) were weak and only one (4%) was a strong biofilm producer. The strong biofilm-producing MSSA was resistant to most of the antibiotics except cefoxitin and clindamycin. None of the MSSA possessed mecA gene while 8 (53.3%) MRSA had it. More than half of S. aureus isolated were MRSA. High incidence of multidrug resistance along with capacity to form biofilm among clinical isolates of S.aureus is a matter of apprehension and prompt adoption of biosafety measures is suggested to curb their dissemination in the hospital environments.

Methicillin-Resistant Staphylococcus aureus (MRSA): Prevalence, Antimicrobial Susceptibility Pattern, and Detection of mecA Gene among Cardiac Patients from a Tertiary Care Heart Center in Kathmandu, Nepal

Background:

Methicillin Resistant Staphylococcus aureus (MRSA) is a significant human pathogen associated with nosocomial infections. mecA in the S. aureus is a marker of MRSA. The main objective of this study was to detect mecA and vanA genes conferring resistance in S. aureus among cardiac patients attending Sahid Gangalal National Heart Centre (SGNHC), Kathmandu, Nepal between May and November 2019.

Methods:

A total of 524 clinical samples (blood, urine, sputum) were collected and processed. Bacterial isolates were tested for antimicrobial susceptibility test (AST) and screening for MRSA was carried out by cefoxitin disc diffusion method. Minimum inhibitory concentration (MIC) of vancomycin for MRSA was established by agar dilution method and chromosomal DNA was extracted and used in polymerase chain reaction targeting the mecA and vanA genes.

Results:

Out of 524 specimens, 27.5% (144/524) showed bacterial growth. Among 144 culture positive isolates, S. aureus (27.1%; 39/144) was the predominant bacteria. Among 39 S. aureus isolates, all isolates were found resistant to penicillin followed by erythromycin (94.9%; 37/39), gentamicin (94.9%; 37/39) and cefoxitin (87.2%; 34/39). Out of 39 S. aureus, 87.2% (34/39) were MRSA. Among 34 MRSA, 8.8% (3/34) were vancomycin intermediate S. aureus (VISA). None of the MRSA was resistant to vancomycin. All of the 3 VISA isolates were obtained from inpatients. Of 39 S. aureus, 82.1% (32/39) harbored mecA gene. Similarly, the entire VISA isolates and 94.1% (32/34) of the MRSA isolates were tested positive for mecA gene.

Conclusions:

High prevalence of MRSA among the cardiac patients indicates the increasing burden of drug resistance among bacterial isolates. Since infection control is the crucial step in coping with the burgeoning antimicrobial resistance in the country, augmentation of diagnostic facilities with routine monitoring of drug resistance is recommended.

Evaluation of Antibiotic Resistance and Biofilm Production among Clinical Strain Isolated from Medical Devices

Microbial biofilms pose a serious threat to patients requiring medical devices (MDs). Prolonged periods of implantation carry a high risk of device-related infections (DRIs). Patients with DRIs often have negative outcomes following the failure of antibiotic treatment. Resistant DRIs are mainly due to the MDs contamination by bacteria producing biofilm. The present study aimed to detect biofilm formation among MD bacterial isolates and to explore their antibiotic resistance profile. The study was conducted on 76 MDs, collected at University Hospital of Campania “Luigi Vanvitelli,” between October 2019 and September 2020. Identification of isolates and antibiotic susceptibility testing were performed using Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) and Phoenix Becton Dickinson, respectively. Biofilm-forming abilities were assessed using the tissue culture plate (TCP) method. Among the 94 MDs isolated strains, 42.7% were Gram-positive, 40.3% Gram-negative, and 17% Candida species. Among 78 bacterial strains, 43.6% were non-biofilm producers while 56.4% produced biofilms. All biofilm producing isolates were sensitive to a limited spectrum of antibiotic classes. All moderate and strong biofilm producers and 81% of weak biofilm producers were Multidrug Resistance (MDR) strains. In contrast, among non-biofilm producers, only 11.8% were classified as MDR strains. Our results highlighted that Sulfamides and Glycopeptides for the major Gram-positive strains and Fluoroquinolones, Carbapenems, and Aminoglycosides for the most represented Gram-negative isolates could be the most suitable therapeutic choice for most biofilm-DRIs.

Evaluation of Biofilm Formation and Prevalence of Multidrug-Resistant Strains of Staphylococcus epidermidis Isolated from Neonates with Sepsis in Southern Poland

Staphylococcus epidermidis strains play an important role in nosocomial infections, especially in the ones associated with biofilm formation on medical devices. The paper was aimed at analyzing the mechanisms of antibiotic resistance and confirming the biofilm-forming ability among S. epidermidis strains isolated from the blood of hospitalized newborns. Genetic analysis of resistance mechanism determinants included multiplex PCR detection of mecA, ermA, ermB, ermC, msrA, and mef genes. Biofilm analysis comprised phenotypic and genotypic methods including Christensen and Freeman methods and PCR detection of the icaADB gene complex. Among the tested S. epidermidis strains, 89% of the isolates were resistant to methicillin, 67%—to erythromycin, 53%—to clindamycin, 63%—to gentamicin, and 23%—to teicoplanin, while all the strains were susceptible to vancomycin and linezolid. The mecA gene was detected in 89% of the isolates, the ermC gene was the most common and present among 56% of the strains, while the msrA gene was observed in 11% isolates. Eighty-five percent of the strains were described as biofilm-positive by phenotypic methods and carried the icaADB gene cluster. Multidrug resistance and the biofilm-forming ability in most of the strains tested may contribute to antimicrobial therapy failure (p < 0.05).

Methicillin-resistant Staphylococcus aureus in Nepal

Staphylococcus aureus is both a frequent commensal and a leading cause of endocarditis, bacteremia, osteomyelitis and skin and soft tissue infections and device-related infections. We performed this minireview to summarize the prevalence of Staphylococcus aureus among clinical samples and estimate the proportion of methicillin-resistant Staphylococcus aureus. The prevalence of Staphylococcus aureus among clinical isolates in Nepal is 34.5%. On average, the proportion of multi-drug resistance in Staphylococcus aureus is 57.1%. Methicillin-resistant Staphylococcus aureus accounts for a total of 41.7%. Inducible clindamycin resistance was detected in about 35% of the isolates. A regular antimicrobial resistance surveillance mechanism is necessary to mitigate the development of resistance among organisms and further spread of superbugs like methicillin-resistance Staphylococcus aureus.

Phenotypic and genotypic virulence features of staphylococcal strains isolated from difficult-to-treat skin and soft tissue infections

Chronic infections represent an important burden on the healthcare system and have a significant impact on the patients’ quality of life. While Staphylococcus spp. are commensal bacteria, they can become pathogenic, leading to various types of infections. In this study we aimed to characterize the virulence profiles of staphylococcal strains involved in difficult-to-treat skin and soft tissue infections, from both phenotypic and genotypic points of view. Phenotypic ability of the strains to secrete soluble virulence factors was assessed by a culturing dependent assay and their capacity to develop biofilms on inert substrate was screened by an adapted crystal violet microtiter method. We also tested the presence of several virulence genes by PCR. Most of the studied strains were isolated from purulent secretions of acne lesions and frequently secreted two or three soluble virulence factors. Most frequently secreted soluble virulence factors were caseinase (89%), lipase (71%) and lecithinase (67%). Almost half of the strains produced a well-represented biofilm. The molecular characterization showed the presence of the genes cna, hlg, clfA, and clfB. Staphylococcal strains that produce difficult-to-treat skin and soft tissue infections seem to be characterized by an enhanced ability to produce different soluble virulence factors and to develop biofilms in vitro. Further studies need to be developed in other Staphylococcus spp. infections in order to confirm this hypothesis.

Antibiotic Resistance and mecA Gene Characterization of Coagulase-negative Staphylococci Isolated from Clinical Samples in Nepal

Background

Coagulase-negative Staphylococci (CoNS) are a significant cause of hospital-acquired and foreign-body-related infections. We conducted this research to assess methicillin susceptibility of CoNS by disc diffusion, agar dilution, and polymerase chain reaction (PCR) methods and to assess the antimicrobial susceptibility pattern.

Methods

We received 123 CoNS isolates from different specimens including blood, endotracheal tube, and central venous catheter. We performed sample processing, identification, and characterization following standard guidelines. Antimicrobial susceptibility was tested based on clinical and laboratory standards institute guidelines. We detected methicillin-resistant coagulase-negative staphylococci (MRCoNS) through mecA gene, disc diffusion method, and agar dilution method and compared the accuracy with PCR as reference.

Results

We detected eight species of CoNS with Staphylococcus epidermidis as the most common. Most of the samples were received from the intensive care unit and blood was the dominant specimen followed by endotracheal-tube aspirate. Seventy-one percentage of isolates were methicillin-resistant by PCR method; disc diffusion and agar dilution method detected methicillin resistance with an accuracy of 96.7% and 98.3%, respectively. Antimicrobial susceptibility revealed an association between the different origins of samples, and also among the types of sample. Similarly, a comparison of the degree of resistance of antimicrobial agents between mecA gene positive and negative isolates showed significant differences. Vancomycin, linezolid, and teicoplanin are still effective for treating MRCoNS.

Conclusion

CoNS are a crucial cause of human infections especially in an intensive care unit setup where the use of devices is common. Disc diffusion and agar dilution are reliable for the detection of MRCoNS. The degree of antimicrobial resistance is much higher in organisms obtained from intensive care unit and foreign-body-related infections.

Rhizobacterial biofilm and plant growth promoting trait enhancement by organic acids and sugars

In the study,Pseudomonas sp. K6 and Pseudomonas monteilii were found to form an enhanced biofilm when cultured in the presence of organic acids and sugars. Here, the highest biofilm could be observed for Pseudomonas sp. K6 (3.08 ± 0.13) and P. monteilii (1.99 ± 0.12) when cultured in presence of 10 µM malic acid. However, maximum production of indole 3 acetic acid (IAA) was observed with 25 µM succinic acid treatment for Pseudomonas sp. K6 (24.33 ± 0.57 µg ml^-1) and with 25 µM galactose for P. monteilii (20 ± 0.0 µg ml^-1). At the same time, Pseudomonas sp. K6 solubilized the highest quantity of phosphate in the presence of 50 µM citric acid (21.33 ± 0.0 µM) and P. monteilii was observed to produce 32.66 ± 1.25 µM soluble phosphate in the presence of 10 µM galactose. The results of the study demonstrate the role of organic acids and sugars in the enhancement of biofilm formation, IAA production and phosphate solubilization in selected Pseudomonas spp. and highlight the potential use of rhizobacteria in conjugation with supplement for the agricultural applications.

Trend and Characteristics of Acinetobacter baumannii Infections in Patients Attending Universal College of Medical Sciences, Bhairahawa, Western Nepal: A Longitudinal Study of 2018

Background

Acinetobacter baumannii is one of the major organisms causing nosocomial infections and is intrinsically resistant to multiple classes of antibiotics. The main objective of this study was to investigate the trend and characteristics of A. baumannii infections including its resistance pattern among patients attending Universal College of Medical Sciences, Teaching Hospital (UCMSTH) in Western Nepal, between January and December 2018.

Patients and Methods

A total of 4862 clinical samples received at the microbiology laboratory of UCMSTH over a period of a year were analyzed. Following bacterial culture on the samples, culture-positive isolates were tested for antibiotic susceptibility using a modified Kirby–Bauer method. The demographic profile of the patient, information about samples, and the antibiotic profile of the A. baumannii isolated from different samples were recorded and analyzed.

Results

A total of 1180 (24.2%; 1180/4862) organisms were isolated from the total samples. Acinetobacter baumannii (12.4%; 147/1180) was the third most common organism. Prevalence of A. baumannii was found to be high in late summer/early winter (July: 15.9%; 18/113 and December: 18.8%; 13/69). The majority 71.4% (n=105) of A. baumannii isolates were multidrug resistant (MDR). None of the isolate was pan-drug resistant. Colistin, polymyxin B, and tigecycline were 100% sensitive to A. baumannii. MDR bacteria were significantly associated with the gender of the patients [female: 51.4% (54/105) versus male: 48.6% (51/105); p=0.05], clinical specimens [swab: 40% (42/105) sputum: 21.9% (23/105) and urine: 10.5% (11/105); p=0.02] and different wards of the hospital [surgery: 30.5% (32/105); ICU: 21.9% (23/105) and medicine: 19.0% (20/105); p< 0.03].

Conclusion

The high burden of MDR Acinetobacter isolates in clinical specimens shows an alarming presence of antimicrobial resistance. Two-thirds of the specimens showed MDR and were associated with demographic and clinical characteristics of the patients. In the management of infectious diseases at UCMSTH, there should be a high suspicion of Acinetobacter infection, and isolation and treatment should be carried out based on an antibiotic susceptibility test.

Clonal Diversity, Biofilm Formation, and Antimicrobial Resistance among Stenotrophomonas maltophilia Strains from Cystic Fibrosis and Non-Cystic Fibrosis Patients

The intrinsic antibiotic resistance of Stenotrophomonas maltophilia, along with its ability to form biofilm both on abiotic surfaces and host tissues, dramatically affects the efficacy of the antibiotic therapy. In this work, 85 S. maltophilia strains isolated in several hospital of central Italy and from several clinical settings were evaluated for their genetic relatedness (by pulsed-field gel electrophoresis, PFGE), biofilm formation (by microtiter plate assay), and planktonic antibiotic resistance (by Kirby–Bauer disk diffusion technique). The S. maltophilia population showed a high genetic heterogeneity: 64 different PFGE types were identified, equally distributed in cystic fibrosis (CF) and non-CF strains, and some consisted of multiple strains. Most of the strains (88.2%) were able to form biofilm, although non-CF strains were significantly more efficient than CF strains. CF strains produced lower biofilm amounts than non-CF strains, both those from respiratory tracts and blood. Non-CF PFGE types 3 and 27 consisted of strong-producers only. Cotrimoxazole and levofloxacin were the most effective antibiotics, being active respectively against 81.2% and 72.9% of strains. CF strains were significantly more resistant to piperacillin/tazobactam compared to non-CF strains (90% versus 53.3%), regardless of sample type. Among respiratory strains, cotrimoxazole was more active against non-CF than CF strains (susceptibility rates: 86.7% versus 75%). The multidrug resistant phenotype was significantly more prevalent in CF than non-CF strains (90% versus 66.7%). Overall, the multidrug-resistance level was negatively associated with efficiency in biofilm formation. Our results showed, for the first time, that in S. maltophilia both classical planktonic drug resistance and the ability of biofilm formation might favor its dissemination in the hospital setting. Biofilm formation might in fact act as a survival mechanism for susceptible bacteria, suggesting that clinical isolates should be routinely assayed for biofilm formation in diagnostic laboratories.

Inoculation Pneumonia Caused by Coagulase Negative Staphylococcus

Rationale

Although frequently retrieved in tracheal secretions of critically ill patients on mechanical ventilation, the existence of pneumonia caused by coagulase-negative staphylococci (CoNS) remains controversial.

Objective

To assess whether Staphylococcus haemolyticus (S. haemolyticus) inoculated in mice’s trachea can infect normal lung parenchyma, increasing concentrations of S. haemolyticus were intratracheally administered in 221 immunocompetent mice.

Methods

Each animal received intratracheally phosphate-buffered saline (PBS) (n = 43) or live (n = 141) or inactivated (n = 37) S. haemolyticus at increasing load: 1.0 × 10⁶, 1.0 × 10⁷, and 1.0 × 10⁸ colony forming units (CFU). Forty-three animals were sacrificed at 12 h and 178 were sacrificed at 36 h; 64 served for post-mortem lung histology, 157 served for pre-mortem bronchoalveolar lavage (BAL) analysis, and 42 served for post-mortem quantitative bacteriology of lung tissue. The distribution of biofilm-associated genes was investigated in the S. haemolyticus strain used in our in vivo experiment as well as among 19 other clinical S. haemolyticus strains collected from hospitals or nursing houses.

Measurements and Main Results

Intratracheal inoculation of 1.0 × 10⁸ CFU live S. haemolyticus caused macroscopic and histological confluent pneumonia with significant increase in BAL white cell count, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-2. At 12 h, high concentrations of S. haemolyticus were identified in BAL. At 36 h, lung injury and BAL inflammation were less severe than at 12 h and moderate concentrations of species belonging to the oropharyngeal flora were identified in lung tissue. The inoculation of 1.0 × 10⁶ and 1.0 × 10⁷ CFU live S. haemolyticus caused histologic interstitial pneumonia and moderate BAL inflammation. Similar results were observed after inoculation of inactivated S. haemolyticus. Moreover, biofilm formation was a common phenotype in S. haemolyticus isolates. The low prevalence of the ica operon in our clinical S. haemolyticus strain collection indicated icaA and icaD independent-biofilm formation.

Conclusion

In immunocompetent spontaneously breathing mice, inoculation of S. haemolyticus causes concentration-dependent lung infection that spontaneously recovers over time. icaA and icaD independent biofilm formation is a common phenotype in S. haemolyticus isolates.

Virulence factors of uropathogenic Escherichia coli (UPEC) and correlation with antimicrobial resistance

Background

Escherichia coli has found to be the predominant uropathogen (50–90%) in uncomplicated, community acquired urinary tract infection (UTI). Uropathogenic Escherichia coli (UPEC) express a multitude of virulence factors, which enable the bacteria to establish UTI. The objective of this study was to evaluate the presence of different phenotypic virulence markers in UPEC isolates and determine their correlation with antibiotic resistance pattern.

Results

Out of 105 patients, 56 (53%) were females and 49 (47%) were males. The age of the patients in the study ranged from 18 years to 87 years and majority of the patients belonged to the age group 20–29 years. Virulence factor was observed in 65% (n = 69) of UPEC and 20% (n = 22) of control isolates (P = 0.0001). Haemolysin production was observed in 34(32.3%) of uroisolates and 12 (11.4%) of control strain. Similarly, 62% of UPEC and 1% of control produced biofilm (P = 0.0001). The expression of Mannose-resistant hemagglutinin (MRHA) and mannose-sensitive hemagglutinin (MSHA) in uroisolates were 52.3% (n = 55) and 5.7% (n = 6) respectively, whereas in faecal isolates, 8.5% (n = 9) expressed MRHA and none produced MSHA. Antimicrobial resistance showed a high degree of resistance towards ampicillin, cotrimoxazole and norfloxacin. The resistance was observed in significant higher degree in biofilm formers as compared to non-formers. MDR and ESBL was observed in 51 and 46% of test strains and 9 and 7.6% of control strains (P = 0.0001).

Conclusion

A significant association between virulence factors of UPEC and antimicrobial resistance in UPEC was present. Routine testing of these factors and co-relation with AMR is recommended. These findings will certainly help understand the pathogenicity and proper management of UTI patients, thus decreasing the improper use of antibiotics.

Prevalence and antibiotic susceptibility of bacteria isolated in patients affected with blepharitis in a tertiary eye centre in Spain

PURPOSE

To describe which bacteria can be found on lid margins in patients affected with blepharitis, to show their antibiotic susceptibility pattern, and to evaluate the antibiotic resistance trend of coagulase-negative Staphylococcus through time.

MATERIALS AND METHODS

Consecutive cases of 198 eyes affected with blepharitis between 2012 and 2018 were reviewed. A sample was collected by rubbing a swab against the base of the eyelashes of both the eyes of all patients. The samples were inoculated in blood agar and chocolate agar. The susceptibility of the identified bacteria to common antibiotics was tested. In addition, the antibiotic susceptibility pattern of coagulase-negative Staphylococcus detected from year 2016 to 2018 was compared with that of 4 years before.

RESULTS

The most common isolated bacterium was coagulase-negative Staphylococcus (89%) and Staphylococcus aureus (28%). Coagulase-negative Staphylococcus showed highest susceptibility to vancomycin (100%), neomycin (94%) and chloramphenicol (91%). Coagulase-negative Staphylococcus and Staphylococcus aureus were the most resistant to penicillin and erythromycin (resistance in 92%, 91% for coagulase-negative Staphylococcus, 86% and 43% of eyes for Staphylococcus aureus). Corynebacterium was resistant to oxacillin and erythromycin. Streptococcus viridans showed resistance to gentamycin and tobramycin. Moraxella was susceptible to most antibiotics. Bacillus was resistant to oxacillin. The antibiotic resistance trend of coagulase-negative Staphylococcus showed that the resistance to rifampicin increased through the years 2012-2018.

CONCLUSION

Coagulase-negative Staphylococcus and Staphylococcus aureus were the most isolated bacteria in patients affected by blepharitis in our tertiary eye centre. Both bacteria were resistant to erythromycin. Through the years, it seems that coagulase-negative Staphylococcus gained resistance to penicillin, erythromycin, ciprofloxacin and rifampicin.

Comparative study of antimicrobial resistance and biofilm formation among Gram-positive uropathogens isolated from community-acquired urinary tract infections and catheter-associated urinary tract infections

Background: Gram-positive cocci have emerged to be an important cause of urinary tract infection (UTI) both in community-acquired UTI (Com-UTI) and catheter-associated urinary tract infection (CA-UTI). The objective of this study was to investigate the frequency of Gram-positive cocci urinary tract infections, their susceptibility patterns to commonly used antimicrobial agents and the biofilm forming property with respect to catheter-associated UTI and community-acquired UTI.

Methods: A total of 1,360 urine samples from indwelling catheter and 10,423 from mid-stream urine were obtained during a 6-month period and processed following standard microbiological guidelines. Biofilm formation was detected using congo red agar (CRA), tube method (TM) and tissue culture plate (TCP) method. Chi-square test and independent sample t-test were employed to calculate the significance. Statistical significance was set at P-value ≤0.05.

Results: The infection rate was significantly higher in CA-UTI as compared to Com-UTI (25% vs 18%, p=0.0001). Among 2,216 organisms isolated, 471 were Gram-positive cocci; 401 were obtained from Com-UTI while 70 were from CA-UTI. Enterococcus faecalis was the most common organism isolated from Com-UTI, while Staphylococcus aureus was commonest among CA-UTI. Multi-drug resistance, methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci were also significantly higher in CA-UTI as compared to Com-UTI. Biofilm-forming property was significantly higher in CA-UTI than Com-UTI. The sensitivity of congo red agar method and tube method was 79% and 81.9% respectively and specificity was 98.5% each. Antimicrobial resistance was significantly higher in biofilm-formers as compared to non-formers.

Conclusion: Gram-positive bacteria are a significant cause of both CA-UTI and Com-UTI with Enterococcus faecalis and Staphylococcus aureus as common pathogen. Biofilm formation and multi-drug resistance is significantly higher in CA-UTI than Com-UTI. Routine surveillance of antimicrobial resistance and biofilm formation is necessary in all cases of UTI to ensure the proper management of patients.

Study of biofilm formation and antibiotic resistance pattern of gram-negative Bacilli among the clinical isolates at BPKIHS, Dharan

Objectives

Gram-negative bacilli are the common causative agents for community-acquired, nosocomial and opportunistic infections. The recent upsurge of biofilm, as well as beta-lactamases producing strains, have synergistically led to the extensive dissemination of multi-drug resistant gram-negative bacilli. This study was carried out with an intention to detect the biofilm formation by gram-negative bacilli and determine their antibiogram along with the detection of extended-spectrum beta-lactamases (ESBLs) and metallo-beta-lactamases (MBLs) production.

Results

Among 314 isolates, Escherichia coli (38%) were the predominant isolates followed by Acinetobacter spp. (20%), Klebsiella spp. (16%), and Pseudomonas spp. (12%). Overall, 197 (62.73%) of isolates were biofilm positive. 84 (26.75%) and 51 (16.24%) were confirmed as ESBL and MBL producers respectively. The association between MBL production and biofilm formation was statistically significant (χ² = 10.20, P value= 0.002) whereas it was insignificant between ESBL and biofilm production (χ² = 0.006, P-value= 0.937). Most of the biofilm and MBL producing strains were multi-drug resistant.