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lec 7
vi sinh
| Neisseria is | Gram-negative bacteria Obligate aerobic |
| Neisseria Habitat | Upper respiratory tract and mouth |
| Neisseria pathogens | N. gonorrhoeae N. meningitidis |
| Neisseria virulence factors | Fimbriae: Adhesion Porins ('Por' proteins) Endotoxin: Lipooligosaaccharide (LOS) |
| Antigenic switching | surface antigens change from generation to generation caused by multiple genetic mechanisms (cơ chế di truyền) important to avoid the host immune response |
| Clinical case Previously healthy 18-year-old man He presented to the emergency department with: Acute onset of fever and headache His temperature was elevated (40°C) He was tachycardic (140 beats/min) He was hypotensive (blood pressure 70/40 mmHg) | It is Neisseria meningitidis |
| N. meningitidis Virulence factors | The most important are the endotoxin and the capsule Polysaccharide capsule |
| N. meningitidis. | Enter Nasopharynx: Usually by droplets Patients may have both: Meningococcemia and Meningitis |
| Acute purulent meningitis | progresses very quickly Mortality is almost 100% in untreated begins suddenly Clinical findings - Intense headache - Fever - Neck stiffness - Low level of consciousness Classical signs -Brudzinski's sign -Kernig's sign Complications (Biến chứng |
| Meningococcemia | Scattered skin petechiae Effect of the endotoxin (LOS) Complications (Biến chứng) Amputations |
| N. meningitidis. Antibiotic treatment and prevention | Third-generation cephalosporins: Ceftriaxone or cefotaxime Vaccines: Conjugated meningococcal polysaccharide vaccines (serogroups) |
| N. gonorrhoeae | grows in chocolate agar (blood) not have a true capsule cover with syalic acid Always pathogen Sexual transmission |
| Gonococcal infection in males | Urethritis is the most common Symptoms -Urethral discharge -Dysuria Local complications: Epididymitis and/or prostatitis |
| Gonococcal infection in females | Cervicitis is the most common Symptoms -Mucopurulent discharge -Vaginal pruritus -Low abdominal pain Local complications: Inflammatory Disease (PID) |
| The family Enterobacteriaceae | found in nature as free-living bac Glucose fermentation Oxidase negative Facultative anaerobic Catalase positive They grow easily on MacConkey agar |
| Antigenic structure | Antigens in the surface - O antigen - K antigen - H antigen |
| O antigen | Sugar component antigen of LPS |
| K antigen | Capsular antigen Some are polysaccharides, others are proteins |
| H antigen | Flagellar antigen Proteins |
| The most common diseases are | Urinary tract infections (UTI) Acute gastroenteritis (with diarrhea) |
| Escherichia coli | Lactose fermenters Many distinct O, K, H antigens Different types of fimbriae Some produce exotoxins |
| Enterotoxigenic (ETEC) | Toxin mostly in children in developing countries |
| Enteroaggregative (EAEC) | toxins & Adhesion Infects primarily young children |
| Enteroinvasive (EIEC) | invasins |
| Enteropathogenic (EPEC) | Adhesion Children in developing countries |
| Shiga-toxin (STEC) | produce EC very danger |
| Urinary tract infections (UTIs) | usually caused by intestinal E. coli |
| One of the most common causes of neonatal meningitis | Escherichia coli (The other one is Streptococcus agalactiae) |
| Meningitis Special virulence factor | K1 capsular polysaccharide |
| Shigella | One of the most common causes of infectious diarrhea |
| Shigella is the | Facultative intracellular pathogen (Tác nhân gây bệnh nội bào) |
| Shigella Virulence factors | The common from Enterobacteriaceae Invasins Shiga-toxin (Stx) Produced by S. dysenteriae type 1 |
| Invasiveness is | the most important pathogenic mechanism, and NOT Shiga toxin |
| Shiga toxin | Produced by -Some E. coli (mainly STEC) -Shigella strains |
| Dysentery is | Diarrhea + leukocytes in stool + erythrocytes in stool caused either by: Invasive Shigella Enteroinvasive Escherichia coli (EIEC) Transmission: Fecal-oral route (Person to person) It appears in epidemic outbreaks (dịch bệnh bùng phát) spread quickly |
| Salmonella | Important public health problem throughout the world Transmission: By the fecal-oral route (animals/humans >> humans) |
| Salmonella Virulence factors | Capsular Vi antigen invasins Invasion is the most important pathogenic event |
| Salmonella Clinical diseases | 'Salmonellosis', gastroenteritis - The most common Typhoid fever - The most severe |
| Salmonellosis | food-borne disease Produced by non-typhoidal Salmonella is the most common Clinical findings: Diarrhea... |
| Typhoid fever | also a food-borne disease is a systemic disease Caused by typhoidal Salmonella Transmitted only from person to person Mortality is high |
| Yersinia | Zoonotic infections |
| Y. enterocolitica and Y. pseudotuberculosis cause | yersiniosis (acute enteritis with diarrhea) |
| Y. pestis causes | plague |
| Common virulence factors to all Yersinia | pYV virulence plasmid LPS |
| Yersinia enterocolitica & Yersinia pseudotuberculosis | Food-borne disease Clinical diseases - Acute enteritis • The most common form of the infection • Self-limited - Syndrome that mimics acute appendicitis • Fever and severe abdominal pain in the right lower quadrant - Reactive arthritis |
| Yersinia pestis (plague) | zoonosis: Transmitted to humans by a vector (lây từ một loài bọ Xenopsylla cheopis) |
| Pneumonic plague | is transmitted human to human by the respiratory route Bubonic plague >> Bacteremia >> Pneumonic plague |
| Bubonic plague | inoculation after a bite (flea) Fever Painful 'bubo' (inflamed lymph node) |
| Opportunistic Enterobacteriaceae | All of them can cause urinary tract infections Common after hospital manipulation Polysaccharide capsule Fimbriae (pili) for adhesion Non-motile |
| Klebsiella | Invasive liver abscess syndrome caused by Klebsiella pneumoniae Most patients are from Taiwan |
| Klebsiella Risk factors | Related with K1 and K2 serotypes: K1 is the most important |
| Vibrio, Aeromonas, Plesiomonas | Common features with Enterobacteriaceae are oxidase-positive in nature - Mostly in water environments |
| Vibrio | Gram-negative rods Highly motile |
| V. cholerae O1 | All produce cholera toxin |
| V. cholerae O139 | It produces cholera toxin and a polysaccharide capsule |
| Current pandemic is produced by | V. cholerae O1 'El Tor' biotype |
| Cholera is | NOT an invasive infection (nhiễm trùng xâm lấn) Caused by the cholera toxin produces the most dramatic and severe watery diarrhea known Food-borne disease Transmitted by the fecal-oral route Very high mortality |
| Cholerae Treatment | fluid replacement for dehydration Single dose azithromycin is the preferred therapy |
| fluid replacement for dehydration Single dose azithromycin is the preferred therapy | Very important in Asia Food-borne disease - Gastroenteritis: seafood |
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