Gram Negative Bacteria PDF

Gram Negative Bacteria Group 3 Cruz, Isidro, Nonog, Pua, Ricardo, Tayag M RPHOLOGY & ID Gram-negative bacteria, such as Neisseria spp., are a group of microorganisms characterized by the structure of their cell walls. Neisseria spp. appears gramnegative under a microscope due to the thin peptidogl...

Gram Negative Bacteria Group 3 Cruz, Isidro, Nonog, Pua, Ricardo, Tayag M RPHOLOGY & ID Gram-negative bacteria, such as Neisseria spp., are a group of microorganisms characterized by the structure of their cell walls. Neisseria spp. appears gramnegative under a microscope due to the thin peptidoglycan layer in their cell walls (Tille, 2014). M RPHOLOGY & ID Pathogens Neisseria gonorrhoeae (gonorrhea) Neisseria meningiditis (meningococcal disease) ae orrhoe n o ia g r e ss i Ne These bacteria are often identified through microbiological culture techniques and molecular methods, such as PCR and DNA sequencing. Ne is s e ria m e n i n g iti di s ANTIGENIC STRUCTURES Neisseria gonorrhoeae 1 4 3 2 Pili Porin protein (Por) Opacity (Opa) proteins Lipooligosaccha rides (LOS) These allow gonococci to attach to the host’s epithelial cells; resist phagocytosis by leukocytes; and facilitate agglutination, primarily among mammalian erythrocytes (Punsalang & Sawyer, 1973). Por acts as a channel for uptake of nutrients and ions. It also suppresses phagocytosis from neutrophils and damages mitochondria of macrophages (Quillin & Seifert, 2018; Deo et al., 2018). Opa proteins found on the outer membrane allow gonococci colonies to adhere together and attach to their host’s cell receptors. These proteins facilitate the colonization of the genital tract’s epithelium (Quillin & Seifert, 2018) These are endotoxins abundant in outer membranes and are similar to LPS of enteric gram negative bacteria but lack O-antigen polymers. These help evade the immune system’s recognition by mimicking the glycolipids of erythrocyte cell membranes. ANTIGENIC STRUCTURES Neisseria gonorrhoeae 1 3 Pili Opacity (Opa) proteins 2 Porin protein (Por) 4 Lipooligosaccha rides (LOS) (Quillin & H. Steven Seifert, 2018) ANTIGENIC STRUCTURES Neisseria meningitidis 1 Polysaccharide capsule The major antigenic structure of meningococci that aids in evading immune response by mimicking signaling molecules. It also prevents cell desiccation. 2 Lipooligosaccha rides (LOS) LOS also regulate nutrient and metabolite flow and contribute to endothelial damage and capillary leakage. LOS are directly correlated with the severity of the disease. 3 Adhesins Major adhesins (pili & Opa proteins) and minor adhesins (MspA & NadA) allow meningococci to form micro colonies and adhere to epithelial cells. ENZYMES AND TOXINS Sialyltransferase gonococci Cleaves a part of nucleotide sugars found in glycolipids and places it on the LOS. Catalase and MsrA/B reductases Detoxify reactive oxygen species produced by neutrophils (i.e., hypochlorous acid, hydrogen peroxide) as a defense mechanism. IgA1 proteases gonococci meningococcus Break down immunoglobulin A (IgA), which inhibits the adherence of bacteria and neutralizes endotoxins. ENZYMES AND TOXINS Endotoxic LOS N. gonorrhoeae LOS interact with glycoprotein receptors to promote invasion in the epithelial tissue in urethra of men and in the cervical tract of women N. meningitidis LOS concentrations are at least 50x greater among patients suffering from sepsis compared to those caused by other gramnegative infections REGULATION OF VIRULENCE DETERMINANTS Capsule LPS Pili Outer membrane proteins The key structures present in this genus that contribute to their virulence includes the LPS, and capsule (only present in N. meningitidis) that acts as shield from the host innate or adaptive immune mechanisms, as well as pili and outer membrane proteins such as OPA, and OPC (not present in N. gonorrhoea) that contains adhesion factors for attachment in host cell linings (Virji, 2009). REGULATION OF VIRULENCE DETERMINANTS Mn-dependent regulation Increased presence of Mn affects several virulence factors of N. gonorrhoeae including: Reduction in the Pilin (PilE) levels, PilC1(pilus assembly), PilQ, PilT (pilus retraction) Increased expression of Porins and minor adhesin MafA Decreased expression of Opa, OmpR and transferrin binding protein A CrgA regulatory protein Role in the adhesion transition of N. meningitidis from initial to intimate adhesion of the bacterial cell to the host target cells. REGULATION OF VIRULENCE DETERMINANTS CrgA regulatory protein Once the CrgA is expressed, it inhibits expression of sia and pilE genes to expose the bacterial cell with its intimate adhesion structures ready for colonization. initial adhesion intimate adhesion PATH LOGY Neisseria gonorrhoeae gonorrhea Neisseria meningiditis meningitis Urogenital tract Upper respiratory tract (nasopharyngeal mucosa) Sexual Transmission Transmission through Bioaerosols Cause the body to elicit an intense inflammatory response to the infected area Asymptomatic through acquired immunity Blood and brain infections like mengitis and septicemia PATH GENESIS Neisseria gonorrhoeae 1 Colonization of the urogenital tract Attachment to epithelial cells primarily with pili and Opa proteins Pili also facilitates microcolony formation 2 Eliciting an immune response Release of their LOS and peptidoglycan fragments to activate release of cytokines and chemokines 3 Formation of pus and transmission Release of inflammatory factors for phagocytosis of gonococci leads to formation of pus which can aid transmission PATH GENESIS Neisseria meningiditis 1 Colonization of the nasopharynx Penetration of the protective mucus by twitching of the pili Attachment to epithelial cells with adhesins 2 Invasion of the bloodstream Polysaccharide capsules prevent phagocytosis and ensure survival in the bloodstream 3 Invasion of the blood brain barrier Immune response from inflammatory cytokines induce the permeability of the blood-brain barrier, cerebrospinal fluid and meninges. CLINICAL FINDINGS Neisseria gonorrhoeae 1 Genital Infections In men, symptoms may include urethral discharge, painful urination, and occasionally swollen testicles (epididymitis). In women, symptoms are often mild or absent but may include vaginal discharge, pelvic pain, and painful urination. 2 Rectal Infections Symptoms can include rectal discharge, itching, pain, bleeding, and discomfort 3 Throat Infections Pharyngeal Gonorrhea Sore throat and discomfort in the throat are common symptoms. 4 Disseminated Gonococcal Infection (DGI) This is a rare but serious complication where the infection spreads to the bloodstream. Symptoms may include fever, joint pain (arthritis), skin rash, and even involvement of internal organs. CLINICAL FINDINGS Neisseria gonorrhoeae 1 Genital Infections 2 Rectal Infections 3 Throat Infections 4 Disseminated Gonococcal Infection (DGI) It's important to note that some individuals with gonorrhea may be asymptomatic, especially in women, which can make diagnosis and transmission control more challenging. CLINICAL FINDINGS Neisseria meningitidis 1 2 3 Meningitis Septicemia (Meningococcemia) Pneumonia & Joint Infections This is characterized by the sudden onset of high fever, chills, and a rapidly spreading rash which can progress to purple or black spots (petechiae). Meningococcal disease can progress rapidly and can be life-threatening, especially if not treated promptly with appropriate antibiotics. Therefore, if someone exhibits symptoms suggestive of meningococcal disease, immediate medical attention is crucial. Symptoms include high fever, severe headache, neck stiffness (meningismus), and sensitivity to light (photophobia). Patients may also experience nausea, vomiting, and altered mental status. Patients may also have symptoms such as fatigue, joint and muscle pain, and cold hands and feet. CLINICAL FINDINGS Neisseria meningitidis 1 2 3 Meningitis Septicemia (Meningococcemia) Pneumonia & Joint Infections CLINICAL FINDINGS Neisseria sicca While generally considered less pathogenic, it can still cause endocarditis, respiratory tract infections, and conjunctivitis (Parker & Nataro, 2010). DIAGNOSTIC LABORATORY TEST Oxidase test Gram Staining An oxidase test can be performed, where the bacteria produce a color change when exposed to oxidase reagent (Murray et al., 2020). Gram-negative diplococci are observed in clinical specimens, indicating the presence of Neisseria species. DIAGNOSTIC LABORATORY TEST Culture Molecular Tests Clinical specimens, such as urethral swabs for gonorrhea or cerebrospinal fluid for meningitis, can be cultured on selective media like Thayer-Martin or chocolate agar. Neisseria species typically grow under these conditions. PCR (Polymerase Chain Reaction) and DNA sequencing can be used for specific identification of Neisseria species and to determine antibiotic susceptibility. DIAGNOSTIC LABORATORY TEST Serology For Neisseria meningitidis, serological tests like latex agglutination or enzyme immunoassays can be used to detect specific antigens in cerebrospinal fluid or blood. Antimicrobial Susceptibility Testing It is a crucial laboratory technique used to determine the effectiveness of antibiotics against bacterial pathogens, including Neisseria species like Neisseria gonorrhoeae and Neisseria meningitidis. This testing is essential for guiding the selection of appropriate antibiotics for treatment, especially in the context of rising antibiotic resistance. DIAGNOSTIC LABORATORY TEST API NH system To further identify the specific species within Neisseria, culture and various biochemical tests, such as the API NH system, can be utilized (Tille, 2014). API NH® is a standardized system for the identification of Neisseria, Haemophilus (and related genera) and Moraxella catarrhalis (Branhamella catarrhalis), which uses miniaturized tests, as well as a specially adapted database. TREATMENT Neisseria gonorrhoeae Treatment of gonorrhea involves antibiotics; the recommended treatment for uncomplicated gonococcal infections was dual therapy with two antibiotics to improve treatment effectiveness and reduce the risk of antibiotic resistance (CDC, 2021). The most common treatment regimen was: Ceftriaxone Azithromycin Usually administered as a single intramuscular injection Often given as an oral dose TREATMENT Neisseria meningitidis Treatment of meningococcal disease involves antibiotics as well. It is a medical emergency, and treatment should be initiated promptly upon suspicion of the disease (CDC, 2021). Common antibiotics used for treatment include: Ceftriaxone or Cefotaxime Administered intravenously (IV) or intramuscularly (IM). These antibiotics are effective against Neisseria meningitidis. The choice of antibiotics may also depend on local antibiotic susceptibility patterns and the patient's age and underlying health conditions. Supportive care fluids and medications to manage symptoms like fever and pain MECHANISMS OF DRUG RESISTANCE Since vaccination is still not an option in effectively killing pathogenic Neisseria due to their adaptive mechanisms to actively evade and counter the host immune response, the only option is through antibiotic medications (Quillin & Seifert, 2018). However, in recent findings, some strains of pathogenic Neisseria are now resistant to penicillin, rifampicin, cefotaxime and ciprofloxacin (Willerton et al., 2021) penA gene mtrCDE efflux pumps LPS & LOS porB protein MECHANISMS OF DRUG RESISTANCE penA gene porB protein encodes for the transpeptidase penicillin binding protein 2 (PBBP) which is a periplasmic transpeptidase needed for peptidoglycan linking and is the most common target of cephalosporins to kill the bacteria. Mutations in this gene disables the binding of the beta lactams to the transpeptidase and render the drug useless against the bacteria (Quillin & Seifert, 2018). Mutations in the porB protein which is one of the main porin rings present in the membrane decreases the permeation of antibiotic molecules that passes through the outer wall of the bacteria, thus decreasing the effectiveness of antibiotics (Bartsch et al., 2021). mtrCDE efflux pumps LPS & LOS Increased efflux of antibiotic molecules through overexpression of mtrCDE efflux pumps as a boosted antimicrobial efflux system (Quillin & Seifert, 2018). Reduced interactions with antimicrobial peptides from the host’s immune response through structural modifications of lipopolysaccharide and lipooligosaccharides (Tzeng & Stephens, 2015). EPIDEMIOLOGY Gonorrhea Approximately 82.4 million newly recorded cases of N. gonorrhaea infections in 2020 (World Health Organization) Because gonorrhea infections may be asymptomatic, these do not account for underreported and underdiagnosed cases Highest prevalence recorded among developing areas of the western Pacific and African regions, and among adolescents (Kirkcaldy, 2019; Quillin & Seifert, 2018). Higher prevalence rate among women (0.8%) compared to men (0.6%) (Quillin & Seifert, 2018) Travel also contributes to the spread of infections through mixing of sexual partners (Kirkcaldy, 2019). High incidence of travel-associated gonorrhea were recorded in Thailand (31.2%) and in the Philippines (8%) EPIDEMIOLOGY Meningococcal meningitis Approximately 1.2 million cases worldwide of meningococcal infections with a death toll of 250,000 as of 2019 (Thisyakorn et al., 2022) 6 of the 12 polysaccharide capsule serogroups (A,B,C, W, X, Y) are known to cause most of the cases worldwide (Caugant & Brynildsrud, 2020) Large epidemics have been associated with serogroup A, such as the largest outbreak in Cordillera from 2004-2006 (Raguindin et al., 2020). Serogroup B has lower recorded incidence, but outbreaks are more prolonged and thus causes higher mortality (Rouphael & Stephens, 2012). Endemic to the Philippines: Approximately 100 cases are reported yearly in the country, with no seasonal variation (Thisyakorn et al., 2022) Highest prevalence (49.2%) was recorded among children less than 5 years old Higher case fatality rates among developing areas: 32% CFR in Cordillera vs 100% CFR in Tawi-Tawi Thank Y u for listening Gram Negative Bacteria Group 3 Cruz, Isidro, Nonog, Pua, Ricardo, Tayag REFERENCES Bartsch, A., Ives, C. M., Kattner, C., Pein, F., Diehn, M., Tanabe, M., Munk, A., Zachariae, U., Steinem, C., & Llabrés, S. (2021). An antibiotic-resistance conferring mutation in a neisserial porin: Structure, ion flux, and ampicillin binding. Biochimica Et Biophysica Acta - Biomembranes, 1863(6), 183601. https://doi.org/10.1016/j.bbamem.2021.183601 Brooks, G., Carroll, K.C., Butel, J., & Morse, S. (2012). Jawetz, Melnick, & Adelberg's Medical Microbiology. (26th ed). McGraw-Hill USA. CDC. (2021). 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