Exotoxin Production Research Articles

The Comparative Characterization of a Hypervirulent Acinetobacter baumannii Bacteremia Clinical Isolate Reveals a Novel Mechanism of Pathogenesis.

Acinetobacter baumannii is an opportunistic Gram-negative pathogen with exquisite survival capabilities under various environmental conditions and displays widespread resistance to common antibiotics. A. baumannii is a leading cause of nosocomial infections that result in high morbidity and mortality rates. Accordingly, when multidrug resistance rates surpass threshold levels, the percentage of A. baumannii clinical isolates surges. Research into A. baumannii has increased in the past decade, and multiple mechanisms of pathogenesis have been identified, including mechanisms underlying biofilm development, quorum sensing, exotoxin production, secretion system utilization, and more. To date, the two gold-standard strains used to investigate different aspects of A. baumannii pathogenesis include ATCC 17978 and ATCC 19606. Here, we report a comparative characterization study of three additional A. baumannii clinical isolates obtained from different infection types and derived from different anatomical regions of infected patients. The comparison of three clinical isolates in addition to the ATCC strains revealed that the hypervirulent bacteremia clinical isolate, known as HUMC1, employs a completely different mechanism of pathogenesis when compared to all its counterparts. In stark contrast to the other genetic variants, the hypervirulent HUMC1 isolate does not form biofilms, is antibiotic-susceptible, and has the capacity to reach higher levels of quorum compared to the other clinically relevant strains. Our data also reveal that HUMC1 does not shed endotoxin into the extracellular milieu, rather secretes the evolutionarily conserved, host-mimicking, Zonula occludens toxin (Zot). Taken together, our hypothesis that HUMC1 cells have the ability to reach higher levels of quorum and lack biofilm production and endotoxin shedding, accompanied by the substantial elaboration of Zot, suggests a novel mechanism of pathogenesis that appears to afford the hypervirulent pathogen with stealth-like capabilities when disseminating through the circulatory system in a state of bacteremia.

Генетический потенциал токсигенных Escherichia coli, выделенных от телят и поросят

Abstract. The study aims to genetically characterize diarrhoeagenic Escherichia coli isolated from cattle and pigs. The main propose is genetic potential responsible for the production of exotoxins in pathogenic E. coli, the causative agents of escherichiosis in calves and piglets. The scientific novelty of the work consists in deciphering the genomes of diarrheogenic E. coli with the presence of nucleotide sequences of several exotoxins, including thermolabile, thermostable and shigap-like, as well as colicins, hemolysins and cyclomodulins, which have pathogenetic significance in the development of escherichia infection in calves and piglets. The study was carried out using microbiological and molecular genetic methods of research and mass spectrometric analysis. As a result, 135 E. coli isolates were subjected to genetic screening by polymerase chain reaction in agarose gel. It was found that 68 (50.36 %) escherichia had toxigenicity markers, while the thermolabile exotoxin gene was recorded more often than others (48.5 %), and the majority was recorded in E. coli isolated from piglets (29.4 %). In 19 (27.9 %) isolates, the presence of genes encoding the production of several exotoxins was established. According to the results of the polymerase-chain reaction, 4 E. coli isolates with a different set of nucleotide sequences responsible for the production of two or more exotoxins at the same time were subjected to genome-wide sequencing. The Escherichia genomes were assembled and annotated and deposited in the NCBI Prokaryotic Genome Annotation Pipeline database under the general number BioProject PRJNA887444. Further studies of E. coli genes and their role in the pathogenic potential of escherichiosis pathogens are needed for the subsequent development of effective means of preventing and controlling infection.

The Emergence and Impact of the M1UK Lineage on Invasive Group A Streptococcus Disease in Aotearoa New Zealand.

M1UK is associated with current surges in invasive infection globally, partly due to increased production of superantigen streptococcal pyrogenic exotoxin A. We show that M1UK is now the dominant invasive emm1 lineage in Aotearoa New Zealand and is genomically related to community infections, suggesting that measures that effectively prevent group A Streptococcus pharyngitis in children could reduce invasive disease.

Does Adjunctive Clindamycin Have a Role in Staphylococcus aureus Bacteremia? A Protocol for the Adjunctive Treatment Domain of the Staphylococcus aureus Network Adaptive Platform (SNAP) Randomized Controlled Trial.

The use of adjunctive antibiotics directed against exotoxin production in Staphylococcus aureus bacteremia (SAB) is widespread, and it is recommended in many guidelines, but this is based on limited evidence. Existing guidelines are based on the theoretical premise of toxin suppression, as many strains of S. aureus produce toxins such as leukocidins (eg, Panton-Valentine leukocidin, toxic shock syndrome toxin 1, exfoliative toxins, and various enterotoxins). Many clinicians therefore believe that limiting exotoxin production release by S. aureus could reduce its virulence and improve clinical outcomes. Clindamycin, a protein synthesis inhibitor antibiotic, is commonly used for this purpose. We report the domain-specific protocol, embedded in a large adaptive, platform trial, seeking to definitively answer this question. The Staphylococcus aureus Network Adaptive Platform (SNAP) trial is a pragmatic, randomized, multicenter adaptive platform trial that aims to compare different SAB therapies, simultaneously, for 90-day mortality rates. The adjunctive treatment domain aims to test the effectiveness of adjunctive antibiotics, initially comparing clindamycin to no adjunctive antibiotic, but future adaptations may include other agents. Individuals will be randomized to receive either 5 days of adjunctive clindamycin (or lincomycin) or no adjunctive antibiotic therapy alongside standard-of-care antibiotics. Most participants with SAB (within 72 hours of index blood culture and with no contraindications) will be eligible to participate in this domain. Prespecified analyses are defined in the statistical appendix to the core protocol, and domain-specific secondary analyses will be adjusted for resistance to clindamycin, disease phenotype (complicated or uncomplicated SAB) and Panton-Valentine leukocidin-positive isolate.

Features of exotoxin production of vaccine strains of anthrax pathogen for use in the veterinary industry

Exotoxins that produce vaccine strains of the anthrax pathogen are the main source of immunogenicity of anti-selective vaccines used in veterinary medicine. The relevance of the study is due to the search for the most suitable vaccine strains of the anthrax pathogen to obtain high production of exotoxin as a factor of the effectiveness of drugs for the implementation of preventive and safety measures in the field of veterinary medicine. In this regard, the purpose of the study was to examine the productive properties of microbes of the Bacillus genus regarding the production of exotoxin under changes in cultivation conditions during incubation. Microbiological and biotechnological methods and comparative statistical analysis are used to examine vaccine strains of the anthrax pathogen. Strains are selected according to the intensity of growth on nutrient media. A biotechnological approach to obtaining a specific anthrax protein is used to analyse the production of exotoxin by vaccine strains of the anthrax pathogen. When cultured on identical nutrient media, the vaccine strains produce different amounts of exotoxin. Virulent (B. anthracis IBM-92 Z), vaccine (B. anthracis K-79 Z, B. anthracis Sterne 34F 2, B. anthracis 55, B. anthracis SB. anthracis Tsenkovsky II) strains, and anthrax cultures (B. cereus 8035, B. anthracoides 67, B. subtilis BKM 17) are examined. In the course of experimental work, it is determined that the production of exotoxin of various anthrax pathogen strains depends on the medium’s pH. It is established that with identical pH values of the medium and cultivation conditions, the highest production of exotoxin was shown by the vaccine strain B. anthracis K-79 Z. The titer of a specific anthrax protein was 1:64. Changes in the pH of the medium during the cultivation of strains affect the amount of exotoxin formation – the main factor in the formation of specific immunity against the anthrax pathogen. The results of the study can be applied by specialists of the veterinary service to select antigen producers in the development of new drugs against anthrax in animals based on exotoxins

Diphtheritic tonsillitis in an immunized adult: A case report

Corynebacterium diphtheriae is a Gram-positive bacillus which can be either toxigenic or non-toxigenic depending on the production of the diphtheria exotoxin. Diphtheria is a potentially fatal infectious disease caused by toxigenic strains of C. diphtheriae. Despite the national immunization program, India accounts for approximately 20% of the total cases according to the recent World Health Organization reports. Even though it is a vaccine preventable disease, cases are being reported, which may be due to lack of booster doses or waning of immunity with increasing age. Here, we report a case of diphtheritic tonsillitis in a 30-year-old immunized adult who came to the otorhinolaryngology outpatient department with acute onset of throat pain and difficulty in swallowing. C. diphtheriae was isolated from bacteriological culture of throat swab. The patient was symptomatically better with 2 weeks of treatment with oral erythromycin 500 mg twice a day.

Detection of resistance and virulence plasmids in Campylobacter coli and Campylobacter jejuni isolated from North Carolina food animal production, 2018–2019

Campylobacter remains the leading cause of bacterial foodborne illness in the U.S. and worldwide. Campylobacter plasmids may play a significant role in antimicrobial resistance (AMR) and virulence factor distribution, and potentially drive rapid adaptation. C. coli (n = 345) and C. jejuni (n = 199) isolates collected from live cattle, swine, turkey, and chickens, poultry carcasses at production, and retail meat in N.C. were analyzed to determine plasmid prevalence, extrachromosomal virulence and AMR genes, and the phylogeny of assembled plasmids. Putative plasmids ranging from <2 kb to 237kb were identified with virulence factors present in 66.1% (228/345) C. coli and 88.4% (176/199) C. jejuni plasmids (promoting adherence, invasion, exotoxin production, immune modulation, chemotaxis, mobility, and the type IV secretion system). AMR genes were identified in 21.2% (73/345) C. coli and 28.1% C. jejuni plasmids (conferring resistance to tetracyclines, aminoglycosides, beta-lactams, nucleosides, and lincosamides). Megaplasmids (>100 kb) were present in 25.7% (140/544) of the isolates and carried genes previously recognized to be involved with interspecies recombination. Our study highlights the extensive distribution and diversity of Campylobacter plasmids in food animal production and their role in the dissemination of biomedically important genes. Characterizing Campylobacter plasmids within the food animal production niche is important to understanding the epidemiology of potential emerging strains.

Transcriptional Regulators Controlling Virulence in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a pathogen capable of colonizing virtually every human tissue. The host colonization competence and versatility of this pathogen are powered by a wide array of virulence factors necessary in different steps of the infection process. This includes factors involved in bacterial motility and attachment, biofilm formation, the production and secretion of extracellular invasive enzymes and exotoxins, the production of toxic secondary metabolites, and the acquisition of iron. Expression of these virulence factors during infection is tightly regulated, which allows their production only when they are needed. This process optimizes host colonization and virulence. In this work, we review the intricate network of transcriptional regulators that control the expression of virulence factors in P. aeruginosa, including one- and two-component systems and σ factors. Because inhibition of virulence holds promise as a target for new antimicrobials, blocking the regulators that trigger the production of virulence determinants in P. aeruginosa is a promising strategy to fight this clinically relevant pathogen.

Probiotic disruption of quorum sensing reduces virulence and increases cefoxitin sensitivity in methicillin-resistant Staphylococcus aureus

Therapies which target quorum sensing (QS) systems that regulate virulence in methicillin-resistant Staphylococcus aureus (MRSA) are a promising alternative to antibiotics. QS systems play a crucial in the regulation of MRSA antibiotic resistance, exotoxin production, antioxidant protection and immune cell evasion, and are therefore attractive therapeutic targets to reduce the virulence of a pathogen. In the present work the the effects of bioactive peptides isolated from two strains of lactic acid bacteria were tested against antibiotic resistance, carotenoid production, resistance to oxidative killing and biofilm structure in two clinical MRSA isolates. The results obtained from fractional-inhibitory concentration assays with bulk and semi-purified bioactive molecules showed a significant synergistic effect increasing cefoxitin mediated killing of MRSA. This was coupled to a six-fold decrease of the major membrane pigment staphyloxanthin, and a 99% increase in susceptibility to oxidative stress mediated killing. Real-time quantitative PCR analysis of the QS-genes agrA and luxS, showed differential expression between MRSA strains, and a significant downregulation of the hemolysin gene hla. Light microscopy and scanning electron microscopy revealed alteration in biofilm formation and clustering behavior. These results demonstrate that bioactive metabolites may be effectively applied in tandem with beta-lactam antibiotics to sensitize MRSA to cefoxitin. Moreover, these results shown that several key QS-controlled virulence mechanisms are diminished by probiotic metabolites.

MRSA and Skin Infections in Psoriatic Patients: Therapeutic Options and New Perspectives.

Psoriatic patients present various infectious risk factors, but there are few studies in the literature evaluating the actual impact of psoriasis in severe staphylococcal skin infections. Our narrative review of the literature suggests that psoriatic patients are at increased risk of both colonization and severe infection, during hospitalization, by S. aureus. The latter also appears to play a role in the pathogenesis of psoriasis through the production of exotoxins. Hospitalized psoriatic patients are also at increased risk of MRSA skin infections. For this reason, new molecules are needed that could both overcome bacterial resistance and inhibit exotoxin production. In our opinion, in the near future, topical quorum sensing inhibitors in combination with current anti-MRSA therapies will be able to overcome the increasing resistance and block exotoxin production. Supplementation with Vitamin E (VE) or derivatives could also enhance the effect of anti-MRSA antibiotics, considering that psoriatic patients with metabolic comorbidities show a low intake of VE and low serum levels, making VE supplementation an interesting new perspective.

6-Methylcoumarin rescues bacterial quorum sensing induced ribosome-inactivating stress in Caenorhabditis elegans

IntroductionBacterial pathogenicity has for long posed severe effects on patient care. Pseudomonas aeruginosa is a common cause of hospital-acquired infections and nosocomial illnesses. It is known to infect the host by colonizing through quorum sensing and the production of exotoxins. MethodsThe current effort is an analysis of proteomic alterations caused by P. aeruginosa PAO1 to study the effects of quorum sensing inhibitor 6-Methylcoumarin on PAO1 infectivity in the Caenorhabditis elegans model. ResultsThrough tandem mass tag-based quantitative proteomics approaches, 229 proteins were found to be differentially regulated in infection and upon inhibition. Among these, 34 proteins were found to be dysregulated in both infection and quorum-sensing inhibition conditions. Along with the dysregulation of proteins involved in host-pathogen interaction, PAO1 was found to induce ribosome-inactivating stress accompanied by the downregulating mitochondrial proteins. This in turn caused dysregulation of apoptosis. The expression of multiple proteins involved in ribosome biogenesis and structure, oxidative phosphorylation, and mitochondrial enzymes were altered due to infection. This mechanism, adapted by PAO1 to survive in the host, was inhibited by 6-Methylcoumarin by rescuing the downregulation of ribosomal and mitochondrial proteins. ConclusionsTaken together, the data reflect the molecular alterations due to quorum sensing and the usefulness of inhibitors in controlling pathogenesis.

Impact of HLA Polymorphism on the Immune Response to Bacillus Anthracis Protective Antigen in Vaccination versus Natural Infection.

The causative agent of anthrax, Bacillus anthracis, evades the host immune response and establishes infection through the production of binary exotoxins composed of Protective Antigen (PA) and one of two subunits, lethal factor (LF) or edema factor (EF). The majority of vaccination strategies have focused upon the antibody response to the PA subunit. We have used a panel of humanised HLA class II transgenic mouse strains to define HLA-DR-restricted and HLA-DQ-restricted CD4+ T cell responses to the immunodominant epitopes of PA. This was correlated with the binding affinities of epitopes to HLA class II molecules, as well as the responses of two human cohorts: individuals vaccinated with the Anthrax Vaccine Precipitated (AVP) vaccine (which contains PA and trace amounts of LF), and patients recovering from cutaneous anthrax infections. The infected and vaccinated cohorts expressing different HLA types were found to make CD4+ T cell responses to multiple and diverse epitopes of PA. The effects of HLA polymorphism were explored using transgenic mouse lines, which demonstrated differential susceptibility, indicating that HLA-DR1 and HLA-DQ8 alleles conferred protective immunity relative to HLA-DR15, HLA-DR4 and HLA-DQ6. The HLA transgenics enabled a reductionist approach, allowing us to better define CD4+ T cell epitopes. Appreciating the effects of HLA polymorphism on the variability of responses to natural infection and vaccination is vital in planning protective strategies against anthrax.

Should Linezolid Replace Clindamycin as the Adjunctive Antimicrobial of Choice in Group A Streptococcal Necrotizing Soft Tissue Infection and Toxic Shock Syndrome? A Focused Debate.

Group A Streptococcus (GAS) necrotizing soft tissue infections and toxic shock syndrome remain high-mortality conditions. In vitro and animal model data, as well as multiple observational studies, suggest adjunctive clindamycin (ie, given with a beta-lactam) reduces invasive GAS infection mortality by inhibiting exotoxin production. Unfortunately, clindamycin resistance in GAS has been rapidly increasing in the United States since the mid-2010s, although the clinical significance of this remains unclear. Linezolid is a promising alternative adjunctive agent to which US GAS isolates remain near-universally susceptible, with a similar mechanism of action and similar in vitro evidence of GAS virulence factor attenuation. However, the clinical data supporting linezolid's value in severe GAS infections are far more limited. Here the authors review the data and reasoning behind a general preference for clindamycin or linezolid in a focused, pro-con debate format.

ToxR is a c-di-GMP binding protein that modulates surface-associated behaviour in Pseudomonas aeruginosa

Pseudomonas aeruginosa uses multiple protein regulators that work in tandem to control the production of a wide range of virulence factors and facilitate rapid adaptation to diverse environmental conditions. In this opportunistic pathogen, ToxR was known to positively regulate the production of the major virulence factor exotoxin A and now, through analysis of genetic changes between two sublines of P. aeruginosa PAO1 and functional complementation of swarming, we have identified a previously unknown role of ToxR in surface-associated motility in P. aeruginosa. Further analysis revealed that ToxR had an impact on swarming motility by regulating the Rhl quorum sensing system and subsequent production of rhamnolipid surfactants. Additionally, ToxR was found to tightly bind cyclic diguanylate (c-di-GMP) and negatively affect traits controlled by this second messenger including reducing biofilm formation and the expression of Psl and Pel exopolysaccharides, necessary for attachment and sessile communities matrix scaffolding, in P. aeruginosa. Moreover, a link between the post-transcriptional regulator RsmA and toxR expression via the alternative sigma factor PvdS, induced under iron-limiting conditions, is established. This study reveals the importance of ToxR in a sophisticated regulation of free-living and biofilm-associated lifestyles, appropriate for establishing acute or chronic P. aeruginosa infections.

Prospect of using B. anthracis exotoxin in the design of anti-selective emergency preparations

The relevance of the study is conditioned upon the fact that outbreaks of anthrax are periodically recorded on the territory of Ukraine, not only in ruminants, but also in pigs, fur animals, dogs, and people. The purpose of the study is to investigate the protective properties of the experimental vaccines and the abacillary vaccine “Antracol” and to prove the immunogenic effect of the extracellular toxin from the B. anthracis K-79 Z strain. Cultures of vaccine strains of anthrax were used for the experiments: B. anthracis 55, B. anthracis SB, B. anthracis K-79 Z and the “Antracol” vaccine (experimental development). Microbiological, clinical-biological, and biotechnological research methods were used in the study. The protective effect was investigated on guinea pigs (Cavia porcellus). An acute experiment was performed with a virulent strain B. anthracis 92 Z. Exotoxin was obtained from the specified cultures. The titre of the exotoxin was found in the disk precipitation reaction. The highest result regarding exotoxin production was recorded in B. anthracis K-79 Z 1 : 128 with a total protein concentration of 0.19 mg/ml, while the exotoxin of B. anthracis strain 55 with a titre of 1 : 32 showed a high total protein concentration of 0.4 mg/ml. The effect of B. anthracis exotoxins on the body was investigated by administering them to laboratory animals in different titres of exotoxins, followed by infection with the pathogenic strain B. anthracis 92 Z. The exotoxin of the vaccine strain B. anthracis K-79 Z in a titre of 1 : 64-1 : 128 shows the best protective properties against the pathogenic strain. It was found that the vaccine strains of B. anthracis SB and B. anthracis K-79 Z have the same level of protection of laboratory animals during experimental infection, which is 60%, while the vaccine from the strain B. anthracis 34F2 showed a level of protection of 20%. Based on the results of the study, it was found appropriate to use exotoxin B. anthracis in the development of prophylactic preparations against anthrax. The research results can be used by scientists and specialists in the field of veterinary medicine to develop new and improve the available vaccines for effective anthrax prevention

No Correlation between Biofilm Formation, Virulence Factors, and Antibiotic Resistance in Pseudomonas aeruginosa: Results from a Laboratory-Based In Vitro Study.

Pseudomonas aeruginosa (P. aeruginosa) possesses a plethora of virulence determinants, including the production of biofilm, pigments, exotoxins, proteases, flagella, and secretion systems. The aim of our present study was to establish the relationship between biofilm-forming capacity, the expression of some important virulence factors, and the multidrug-resistant (MDR) phenotype in P. aeruginosa. A total of three hundred and two (n = 302) isolates were included in this study. Antimicrobial susceptibility testing and phenotypic detection of resistance determinants were carried out; based on these results, isolates were grouped into distinct resistotypes and multiple antibiotic resistance (MAR) indices were calculated. The capacity of isolates to produce biofilm was assessed using a crystal violet microtiter-plate based method. Motility (swimming, swarming, and twitching) and pigment-production (pyoverdine and pyocyanin) were also measured. Pearson correlation coefficients (r) were calculated to determine for antimicrobial resistance, biofilm-formation, and expression of other virulence factors. Resistance rates were the highest for ceftazidime (56.95%; n = 172), levofloxacin (54.97%; n = 166), and ciprofloxacin (54.64%; n = 159), while lowest for colistin (1.66%; n = 5); 44.04% (n = 133) of isolates were classified as MDR. 19.87% (n = 60), 20.86% (n = 63) and 59.27% (n = 179) were classified as weak, moderate, and strong biofilm producers, respectively. With the exception of pyocyanin production (0.371 ± 0.193 vs. non-MDR: 0.319 ± 0.191; p = 0.018), MDR and non-MDR isolates did not show significant differences in expression of virulence factors. Additionally, no relevant correlations were seen between the rate of biofilm formation, pigment production, or motility. Data on interplay between the presence and mechanisms of drug resistance with those of biofilm formation and virulence is crucial to address chronic bacterial infections and to provide strategies for their management.

Epidemiology of serious bacterial infection in febrile infants under 3 months of age and diagnostic management in Mayotte

ObjectiveThis study aimed to determine the prevalence of serious bacterial infections (SBIs) in infants less than 90 days old presenting with fever on arrival at the emergency department (ED), and to assess the diagnostic management of febrile infants. DesignA retrospective study at Mamoudzou Hospital, Mayotte Island, French Department. SettingGeneral ED in the only pediatric hospital throughout the territory PatientsWe included infants less than 90 days old with a history of fever and bacterial investigation evaluated in the ED between 2016 and 2018. We excluded preterm infants (gestational age < 37 weeks) and those with known immunodeficiency or previous administration of antibiotics. ResultsA total of 594 infants were included. In all, 105 infants (17.7%) were diagnosed with an SBI and 28 (4.7%) with an invasive bacterial infection of which 1.34% was meningitis. The most frequent SBI was pneumonia (n = 69, 11.6%) followed by urinary tract infection (UTI; n = 37, 6.2%). Predominant pathogens (excluding contaminants) were Escherichia coli (51.2% of the UTI cases), group B Streptococcus (62.5% of meningitis cases), and Staphylococcus aureus (61.5% of bacteremia cases). Seven infants presented with bacterial pneumonia due to Staphylococcus aureus with Panton–Valentine leucocidin (PVL) exotoxin production. Ill-appearing infants, clinical signs of SBI and complex chronic condition were associated with a risk of SBI (respective odds ratio [OR]: 4.6, 95% confidence interval [CI]: 3–6.9; OR: 4.2, 95% CI: 2.8–6.4; and OR: 3.2, 95% CI: 1.2–8.5). The median age for SBI was 42 days (5–90). Fever without source (FWS) occurred more often in infants under 21 days of age (48.5% vs. 31.3% in older infants, p < 0.001). The median duration of fever at home was 24 h (6–96). Concerning management, in infants aged under 21 days, there were more lumbar punctures (58.3% vs. 23% in older infants, p < 0.001) and more frequent initiation of empiric antibiotics (62.6% vs. 42.7%, p < 0.001). Length of stay was also longer in this age range (5 days vs. 3 days, p = 0.037). ConclusionDelay in medical consultation in the case of fever, the risk of SBI regardless of age, and unusual epidemiology with many IBI due to Staphylococcus aureus with PVL exotoxin production are specific characteristics observed in our study. Knowledge of the current epidemiology of SBI in Mayotte would be useful for setting up a risk-stratified protocol in this population in the future.

Vanillic acid combats Vibrio alginolyticus by cell membrane damage and biofilm reduction.

Antibiotics are the most powerful weapon against bacterial infectious diseases in aquaculture. However, the indiscriminate usage of antibiotics often culminates in the emerging development of antibiotic-resistant bacteria, making it imperative to search for novel types of antimicrobial agents. This study investigated the antibacterial and antivirulence effects of vanillic acid (VA) against the fish pathogen, Vibrio alginolyticus. We showed that VA had a good anti-Vibrio activity with minimal inhibitory concentration (MIC) of 1.0mg/ml. In addition, VA wielded its antibacterial action in a dose-/time-dependent manner by causing cell membrane damage and increasing membrane permeability, which is evidenced by increasing the conductivity and malondialdehyde content in the treated cell cultures and the scanning electron microscopy images. Furthermore, VA significantly reduced the biofilm-forming capability, mobility and exotoxin production (protease and exopolysaccharide) and downregulation of the expression of biofilm- and virulence-associated genes (sypG, fliS, fliK, lafA, lafK, asp and luxR) was seen in the V.alginolyticus that exposed to VA at subinhibitory concentrations. Overall, our findings suggested that VA may be of interest for treating V.alginolyticus-associated infections in aquaculture.

Adjunctive Clindamycin Improves Outcomes of Invasive Group A Streptococcal Infection: Best Evidence to Date

Clindamycin decreases production of exotoxins that underlie many manifestations of invasive group A streptococcal (iGAS) infections. Although this

Gas Gangrene in a Closed Pelvic Injury

Gas gangrene in a closed pelvic injury is very rare phenomenon and we could not find many reported cases in the literature. Radiographs are not enough for diagnosis and computed tomography (CT) is not widely available yet in primary health center. Basic management includes surgical debridement with incision and drainage of necrotic tissue of the involved area, antibiotic therapy, and surgical intensive care. Delay of the surgical debridement for &gt;12 h is associated with higher overall morbidity. The aerobic and anaerobic bacteria with the indigenous commensal of the pelvis results in the production of exotoxins that leads to severe rapid tissue necrosis and the synthesis of insoluble gases characteristic of subcutaneous emphysema or Fournier's gangrene. Although gas gangrene is often diagnosed clinically, emergency CT can support in early diagnosis with accurate assessment of the disease extent. CT not only helps evaluate the pelvic bony structures but also helps assess the spread of disease in the abdomen and pelvis. The mainstay of the management includes surgical debridement with incision and drainage of necrotic tissue of involved area, antibiotic therapy, and surgical intensive care. Early diagnosis remains the mainstay of the treatment of Gas gangrene. It is important to diagnose these life-threatening conditions and treat them as early as possible. Due to the rarity of such events and the unavailability of gold standard diagnostic and treatment modalities, it is very difficult to prevent the mortality for such patients. There is a need for a better treatment plan to diagnose and manage such patients urgently and not to miss the initial phase of disease progression which is critical for saving the life of the patient.