Enterobacteriaceae Week 3 PDF

Clinical Microbiology –Week 3 University of Nicosia, Cyprus Enterobacteriaceae Enterobacteriaceae Large heterogeneous family that contains >50 genera & hundreds of species of gram (-) bacilli Ubiquitous in nature, found in water, soil, & vegetation, colonize G.I t...

Clinical Microbiology –Week 3 University of Nicosia, Cyprus Enterobacteriaceae Enterobacteriaceae Large heterogeneous family that contains >50 genera & hundreds of species of gram (-) bacilli Ubiquitous in nature, found in water, soil, & vegetation, colonize G.I tract of many animals & humans Major cause of: bacteraemia, UTIs, intra-abdominal infection, pneumonia, gastroenteritis & other Medically important Enterobacteriaceae (among others) are: Escherichia spp Hafnia alvei Klebsiella spp Providencia spp Proteus spp Morganella morganii Shigella spp Pantoea agglomerans Salmonella spp Plesiomonas shigelloides Yersinia spp Edwardsiella tarda Enterobacter spp Citrobacter spp Enterobacteriaceae Enterobacteriaceae can be: 1. Primary pathogens (always associated with disease if found in clinical specimens) Salmonella typhi Shigella spp Yersinia pestis (plague) 2. Opportunistic pathogens (members of normal flora –associated with disease in certain cases) Escherichia coli Proteus spp Klebsiella spp Gram (-) bacilli, facultative anaerobes, ferment glucose & other sugars (lactose), catalase (+), oxidase (- ) Colonize oropharynx of hospitalized patients within 72hrs, major cause of HA infections CRE: Carbapenem Resistant Enterobacteriaceae, URGENT medical threat Enterobacteriaceae – physiology & structure Typical Gram (-) structure Inner (cytoplasmic) membrane: regulates passage of nutrients & macromolecules Periplasmic space: aqueous environment that contains PG layer & proteins Outer membrane: lipid bilayer, phospholipid on inner layer, LPS on outer Porins: proteins on outer membrane. Channels for hydrophilic molecules to enter Clinical Microbiology –Week 3 University of Nicosia, Cyprus Escherichia coli Escherichia coli Of most important human pathogens. Variety of community & hospital acquired infections (bacteraemia, sepsis, UTIs, gastroenteritis, meningitis, intra-abdominal infections etc.) Part of intestinal flora, pathogens if intestinal barrier damaged (e.g. perforation) or by acquisition of specific virulence factors (e.g. for UTIs or gastroenteritis) Pathogenic strains differ from commensal strains by their ability to produce virulence factors E. coli is: 1. Most common gram (-) bacillus isolated from patients with sepsis 2. Number one cause of CA-UTIs (& HA-UTIs) 3. Of the most frequent causes of gastroenteritis 4. Number one cause of “traveller’s diarrhea” 5. Second cause of neonatal meningitis (1st is S. agalactiae) Escherichia coli - extraintestinal Most common cause of UTI & leading cause of neonatal meningitis (second to S. agalactiae) Uropathogenic E. coli: more likely to produce P-fimbriae and/or type 1 fimbriae Colonize urethra –ascend to bladder & cause cystitis: 1:2 women will experience one episode Cystitis Dysuria & urinary urgency. Smelly urine, might be bloody. Cystitis DOES NOT cause high fever By ascending route they might reach the kidneys & cause pyelonephritis Pyelonephritis High fever with chills, vomiting may be present, pain at the costovertebral angle. GIORGANO SIGN SERIOUS INFECTION. May lead to bacteraemia & sepsis Step 2: adherence Uropathogenic E. coli - UPEC Type 1 fimbriae bind to bladder epithelium UPEC bind to epithelial cells form biofilm Deletion of type 1 fimbriae –no adherence –no biofilm (remember Koch’s postulates) Urine flow does not clear bacterial colonies UPEC invade bladder epithelium Inflammation Urinary Tract Infection Urinary tract infections Costovertebral tenderness Urine dipstick (+) Giordano sign - pyelonephritis Urine dipstick: (+) for WBC, maybe RBCs, maybe nitrates & leucocyte esterase Urinalysis (microscopic): WBCs, possibly RBCs, microorganisms Urine culture: Midstream urine sample. identifies pathogen. >100.000 cfu/ml Escherichia coli - intestinal E. coli causes gastroenteritis by 6 different mechanism based on virulence factors 1. Enterotoxinogenic E. coli (ETEC) Diarrheal disease in developing countries (840 million cases/yr) & number one cause of traveler’s diarrhea (local adults are protected through repeated exposure) Consumption of fecally contaminated food or water. Person-to-person spread does not occur After 1-2d, watery, non-bloody, abdominal cramps, nausea & vomiting. Can be severe if underlying diseases, esp. children & elderly ETEC attach to small bowel epithelium & produce heat-stable & heat-labile enterotoxins 2 classes of enterotoxins: heat-stable toxins (STa & STb) and heat-labile toxins (LT-I, LT-II) ETEC – traveler’s diarrhea If traveler at destination (from high income to low-middle income country), ≥3 unformed stools/24hrs plus one of abdominal cramps, tenesmus, nausea, vomiting, fever, or fecal urgency ETEC – traveler’s diarrhea Escherichia coli - intestinal 2. Enteropathogenic E. coli (EPEC) Characterized by their “attaching & effacing” effect, & NO PRODUCTION of Shiga toxins Rare in developed world, deadly disease among infants in Africa –breastfeeding highly protective Person-to-person spread, watery diarrhea, low-grade fever & vomiting Hallmark: “attaching& effacing effect”.Bacteria attach to apical surface of small intestine epithelial cells & loss (effacement) of microvilli –form cup-like pedestal on which bacteria rest Loss of microvilli results in malabsorption & profuse diarrhea EPEC – attachment & effacement Escherichia coli - intestinal 3. Enteroaggregative E. coli (EAEC) Aggregative pattern of appearance in tissue culture cells. Form two-dimensional clusters when they attach on intestinal mucosa Mucosal damage, loss of microvilli & cell death - Chronic diarrhea (>21d), traveller’s diarrhea, persistent diarrhea in HIV (+) Chronic diarrhea in children leads to malabsorption & growth retardation Some produce toxins similar to ST by ETEC EAEC – aggregative adherence Aggregation in tissue cultures Aggregation on intestinal mucosa  Escherichia coli - intestinal 4. Enteroinvasive E. coli (EIEC) Similar to Shigella (discussed latter) - rare in both developed & developing countries Have an invasion plasmid – invade colonic intestinal epithelial cells – escape phagosome & multiply in cytoplasm –using actin cytoskeleton as “road” –spread from cell to cell Differentiated from Shigella by the fact that they ferment glucose & xylose Watery diarrhea, may progress to dysentery with fever, abdominal cramps, small volume bloody/mucoid stools Escherichia coli - intestinal 5. Enterohemorrhagic E. coli (EHEC) & other Shiga-toxin producing E. coli Shiga toxins: bacteriophage-encoded cytotoxins that block protein synthesis & induce cell death Among Shiga toxin–producing E. coli STEC, those that share with EPEC the ability of attaching & effacing are known as Enterohemorrhagic E. coli (EHEC) EHEC, O157:H7: outbreaks & high rates of complications (more pathogenic than non-EHEC STEC) Reservoir of EHEC: G.I tract of young cattle & herbivorous mammals, survive for long periods in environment, proliferate in vegetables, foods & beverages Outbreaks: undercooked ground beef or contaminated vegetables (water, petting zoos, direct person- to-person, unpasteurized milk). Very low infectious dose (72hrs 2. Elderly with comorbidities 3. Immunosuppressed patients 4. Investigation of diarrheal outbreak 5. Recent antibiotic use (rule out Clostridium difficile colitis) 6. Food handlers & residents of health-care facilities 10% > 1 5% >2 1% > 4 WEEK WEEKS WEEKS BACTERIA PARASITES Salmonella, Shigella, Giardia, Entamoeba, Campylobacter, C. difficile Cryptosporidia, Helminths Stool microscopy & fecal biomarkers Presence of leukocytes = invasive disease Campylobacter, Salmonella, Shigella, EIEC, amoeba Absence of leukocytes = non - invasive Viral, Vibrio cholerae, ETEC, toxin-mediated syndromes Gonzalez et al. Clin Lab Med. 2016 Multiplex PCR Navidad et al. J Clin Microbiol. 2013 Clinical Microbiology –Week 3 University of Nicosia, Cyprus Klebsiella Klebsiella species 4 species cause human disease. K. pneumoniae, K. oxytoca, K. granulomatis, K. rhinoscleromatis Klebsiella pneumoniae Both community & hospital acquired infections Causes: lobar necrotic pneumonia, UTIs, liver abscesses (leading cause in Asia), septicaemia in hospitalized patients, wound infections, intra-abdominal infections & other K. oxytoca causes antibiotic-related colitis Pneumonia by K. pneumoniae, has distinctive features: 1. Very severe, with alcoholics being very susceptible group 2. Frequently affects upper lobes, frequent abscess formation 3. Production of “currant jelly” sputum (haemoptysis) Klebsiella pneumoniae Mucoid cultures Lobar necrotic pneumonia Haemoptysis Liver abscesses K. oxytoca –antibiotic related colitis Wound infection K. pneumoniae = ONE OF THE MOST RESISTANT NOSOCOMIAL BACTERIA - CRE Critical thinking 80-year-old man, bedridden with a permanent urinary catheter, presents with high fever, disorientation and confusion, and low blood pressure. Will you admit and why? Is infection likely and why? Which are the most appropriate biological samples for microbiological studies? The patient is placed on Ceftriaxone Day 3 – the patient is afebrile, when he suddenly develops high fever, and multiple episodes of malodorous diarrhea. Briefly describe the underlying pathophysiology of the patient’s diarrheal syndrome Which is the most likely implicated microorganism? How will you investigate? Critical thinking The patient is placed on oral Vancomycin (acts only in intestinal lumen, zero systemic absorption), diarrhea and fever subside. Day 12 – the patient develops a new febrile episode. Physical examination reveals an inflamed decubitus ulcer on the patients lower back Which genera you plan to cover empirically and why? How will previous antimicrobial schemes influence your decision and for which genera? LOBs HUS = uremic haemolytic syndrome, PNFs = neutrophils Which intestinal & extraintestinal clinical syndromes are attributed to E.coli? Which virulence factors are implicated? Epidemiology, clinical syndrome & virulence factor of Shigella spp. Epidemiology, clinical syndrome & virulence factor of Yersinia spp. Epidemiology, clinical syndrome of Klebsiella spp. Thank you very much for your attention