Unit 14. Gram Negative Cocci and Rods Microbiology PDF

Microbiology Unit 14 Gram negative cocci and rods Ve más allá • Neisseria spp • Pseudomonas aeruginosa 1 • Enterobacteriaceae family Neisseria genus. Gram-negative cocci 1. Neisseria Genus (gramnegative cocci) • Gram-negative cocci arranged in pairs (diplococci, “kidney beans") • Commensal sp...

Microbiology Unit 14 Gram negative cocci and rods Ve más allá • Neisseria spp • Pseudomonas aeruginosa 1 • Enterobacteriaceae family Neisseria genus. Gram-negative cocci 1. Neisseria Genus (gramnegative cocci) • Gram-negative cocci arranged in pairs (diplococci, “kidney beans") • Commensal species in the oropharynx: N. sicca, N. mucosa, N. lactamica  Rare opportunistic pathogens • True pathogens:  Neisseria meningitidis (meningococcus) Neisseria gonorrhoeae (gonococcus) • Demanding in culture medium: • Growth in enriched media: chocolate agar • Oxidase positive • Carbohydrate oxidation with productionof acid. Biochemical identification. • Differentiation between meningococcus and gonococcus. Fuente: Bill Schwartz. 1971. Public Health Image Library (PHIL), CDC. 4 1. Neisseria Genus N. meningitidis • Natural habitat: human pharynx (nasopharynx) • Carriers: 5-10% of the general population (higher in epidemics). • Transmission by droplets of oropharyngeal and respiratory secretions, by saliva, Pflügge droplets. • Development of the disease depends on: • Immune status of the individual • Strain virulence • If it causes disease: hematogenous dissemination (meningococcemia) and/or meningitis (tropism for the central nervous system) • Meningococcemia: possible appearance of petechiae, purpura • Meningitis: intracellular gram-negative diplococci can be observed in CSF • DISEASE OF COMPULSORY DECLARATION (EDO) N. meningitidis • Bacteremia (meningococcemia) and / or meningitis • Mortality 5-10% • -According to the capsular polysaccharide, it is classified into serogroups (A, B, C, Y, W135...) Epidemiology of meningitis due to Neisseria meningitidis in Spain: • Serogroups B and C are the main causes of disease in Spain (85-90% of cases). • Peak incidence at the age of 3 months-12 months. • High incidence up to 3 years of age and another peak in adolescents. • Seasonal pattern: most cases between December and March, with a peak in January. N. meningitidis Treatment (intravenous): • Penicillin G (if the strain is sensitive) • Cefotaxime or ceftriaxone Chemoprophylaxis (when necessary, contacts of cases): • Rifampicin 2 doses/day for two days • Ciprofloxacin or levofloxacin (single dose) • Ceftriaxone (single dose) Vaccines: • Capsular polysaccharide: serotypes A , C , Y , W135. Not used in Spain. • Conjugate (polysaccharide + protein). More efficient and durable response  Serogroup C (immunization schedule)  A , C , Y , W135 (immunosuppresed, travelling to endemic areas, immunization Schedule 2019) • Recombinant proteins: vaccine against B serotype (August 2014) N. meningitidis In the dental office: • Transmission occurs through the pharyngeal secretions of the patient, so the dentist has a high risk of acquiring this pathogen (which does not mean risk of illness) • Preventive measures:  Mask  Hygiene among patients  If a patient developed meningitis in the days following the dental visit: chemoprophylaxis  Vaccination 1. Neisseria Genus N. gonorrhoeae (gonococcus) • Gramnegative cocci in pairs (diplococci, “kidney beans") • Nutritionally fastidious (enriched medium for optimal growth): chocolate agar • Produces gonorrhea (STD, (sexually transmitted and perinatal disease). • Exclusive of humankind, present in mucous membranas. • Mucosal infections: uterine cervix, urethra, anal portion of the rectum, pharynx and conjunctiva (ophthalmia neonatorum). • Urethritis: intracellular gram-negative diplococci are observed in urethral exudate • DISEASE OF COMPULSORY DECLARATION (EDO), not urgent. N. gonorrhoeae (gonococcus) Manifestations: • Urethritis in men. • Endocervicitis in women Treatment of choice: • Cefixime or Ceftriaxone • Add doxycillin or azithromycin to cover Chlamydia Treatment of choice: • Alternatives: Azithromycin Pseudomonas aeruginosa. Gram-negative bacilli Pseudomonas aeruginosa • Gram-negative rods (bacilli) • Motile (flagella). In culture, poorly defined, extended colonies are observed. • Strict aerobes • Oxidative metabolism, no sugar fermentation • NonFermenting Gram Negative Bacilli (NFGNB) • Oxidase (+) (has the enzyme oxidase) • Production of colorful fluorescent and soluble pigments (pyocyanin and pyoverdine) • Some colonies have metallic sheen • Some strains produce capsules: mucoid colonies. • Cultures on solid medium have a characteristic “fruity odor”. • Humid habitat 2. Pseudomonas aeruginosa • Usually Pseudomonas does not cause infection in healthy people: • breakage of mucocutaneous barriers (burns, traumas, surgery) or immune diseases. • Important in nosocomial infections (opportunistic pathogen) • Multiple virulence factors • Intrinsically resistant to many antibiotics (antibiogram necessary), sometimes acquired resistance 2. Pseudomonas aeruginosa Fuente: Pseudomonas aeruginosa.JPG. Sun 14916. 2012. Disponible en: commons.wikimedia.org/wiki/File:Pseudomonas_aeruginosa.JPG 14 2. Pseudomonas aeruginosa 2. Pseudomonas aeruginosa Clinical Manifestations: A) Cutaneous infections 1. Folliculitis 2. Infections of burns, wounds, after penetrating trauma or surgery… 3. Ecthyma gangrenosum: • Starts as an erythematous macule (=red spot), • rapidly progresses to a blister (=bladder), ulcer and necrosis. • Typical final lesion: central necrosis with peripheral erythema. • It is a lesion that can appear in the context of a generalized infection or progress to it. 2. Pseudomonas aeruginosa B) Other infections 1. In hospitalized patients, immunocompromised: • Lung infections (pneumonia associated with mechanical ventilation) • Urinary tract infections (in patients with long-lasting urinary catheters) • Bacteremia • Sepsis or septicemia (generalized infection, with hypotension and shock = multiple organ failure due to lack of tissue irrigation) 2. In swimmers: Ear infections (external otitis) 3. In eye lens users: Eye infections, conjunctivitis 2. Pseudomonas aeruginosa Treatment • Complicated treatment due to: • Natural resistance to multiple antibiotics • Acquired resistances • Most effective antibiotics: 3rd generation antipseudomonal cephalosporins (ceftazidime), imipenem, ciprofloxacin, tobramycin, amikacin, piperacillin-tazobactam • In severe infections, antibiotics are always used • In ecthyma, abscesses, deep skin infections: drainage and surgical debridement. Enterobacteriaceae Family Gram-negative bacilli 3. Enterobacteriaceae family • 30 genera and >110 species • Gram-negative rods (bacilli) • Glucose fermentation • Oxidase (-) They do not have the enzyme oxidase • Growth under aerobic / anaerobic conditions. There are strict aerobic species and other species are facultative anaerobes. • Habitat: environment and normal microbiota of humans Types and animals (GI tract) • Opportunistic pathogens / primary pathogens 3. Enterobacteriaceae family 30 Genera and > 110 species Opportunistic pathogens (as part of the microbiota) Escherichia coli Klebsiella, Enterobacter, Citrobacter, Serratia Proteus, Morganella, Providencia Primary pathogens (not part of the microbiota, can be present after an infection in the gut = carrier state) Salmonella Shigella Yersinia Some strains of Escherichia coli 3. Enterobacteriaceae family Biochemical characteristics • Glucose fermentation • Lactose fermentation: variable (McConkey selective medium) • Nitrates reduction (+) • Oxidase (-) • When they are motile, it is by peritrichous flagella • They differ from each other in multiple biochemical characteristics • Identification: API test, Kligler media, TSI media… 3. Enterobacteriaceae family 3. Enterobacteriaceae family https://commons.wikimedia.org/wiki/File:TSIagar.JPG Identification of enterobacteria, TSI. Glucose and lactose fermentation, gas and H2S production 3. Enterobacteriaceae family  Subclassification in serotypes according to their antigenic structure • H antigen: flagella= protein • K antigen: surface = capsular polysaccharide • O antigen: cell wall= LPS  Epidemiological use (indentify the strain involved in an outbreak) 3. Enterobacteriaceae family Sensitivity to antibiotics: • Variable depending on the species • Antibiogram (sensitivity test) required • Interpreted reading of the antibiogram Fuente: Public Health Image Library (PHIL), CDC 3. Enterobacteriaceae family Infections produced by Enterobacteriaceae: Most common • Urinary tract infections: urinary infection, prostatitis • Abdominal infections (peritonitis, abscesses, gastroenteritis: diarrhea, vomiting, abdominal pain) Other infections (hospitalized patients, immunocompromised) • Wound infections (surgical, trauma, burns, ..) • Respiratory infections (intubated, ..) • Bacteremia • ... 3. Enterobacteriaceae family 3.1. Escherichia coli Opportunistic pathogenic strains in the intestinal microbiota:  Extraintestinal symptoms  Urinary Tract Infections  Neonatal meningitis  Other, uncommon in healthy people (meningitis, sepsis…)  Strict pathogenic strains, they are not in the microbiota: Gastrointestinal symptoms: • Enterotoxigenic (ETEC): traveller’s diarrhea, infant diarrhea • Enteropathogenic (EPEC): infant diarrhea • Enteroinvasive (EIEC) • Enterohemorrhagic (EHEC) 3. Enterobacteriaceae family Shigella • Etiological agent of bacillary dysentery: diarrhea (liquid, watery, bloody stools), vomiting, fever. In travelers due to consumption of non-chlorinated water. S. dysenteriae (group A) S. flexneri (group B) S. boydii (group C) S. sonnei (group D) 3. Enterobacteriaceae family Salmonella • Fecal-oral transmission (from people or animals). • There may be a carrier state (transmits the disease while being asymptomatic) • S. typhi and S. paratyphi: Typhoid fever and paratyphoid fever • S. enteritidis and S. choleraesuis : Gastroenteritis. 3. Enterobacteriaceae family Gastroenteritis - Infection by ingestion of food / wáter, oral/fecal transmission - Acute enterocolitis (fever, diarrhea, vomiting) - Usually self-limited in healthy individuals Typhoid and paratyphoid fever - Infection by ingestion of food / wáter, oral/fecal transmission - Invasion without enterocolitis - Fever, nonspecific symptoms and then gastrointestinal symptoms 3. Enterobacteriaceae family Yersinia Mainly animal pathogens • Y. pestis: Bubonic plague • Y. enterocolitica: enterocolitis THANKS FOR YOUR KIND ATTENTION! QUESTIONS PLEASE? Ve más allá © Copyright Universidad Europea. Todos los derechos reservados