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• Gram negative cocci and rods


  Microbiological classification of bacteria
• Microorganisms covered


  • Neisseria spp
  • Pseudomonas aeruginosa
  • Enterobacteriaceae family

  
• Neisseria genus


  Gram-negative cocci
• Neisseria species


  • Neisseria meningitidis
  • Neisseria gonorrhoeae

  
• Neisseria genus


  • 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 like chocolate agar, Oxidase positive, Carbohydrate oxidation with production of acid, Biochemical identification, Differentiation between meningococcus and gonococcus

  
• Neisseria meningitidis (meningococcus)


  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 and 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)

  
• Neisseria meningitidis


  • Bacteremia (meningococcemia) and / or meningitis, Mortality 5-10%, Classified into serogroups (A, B, C, Y, W135...)
• Epidemiology of meningitis due to Neisseria meningitidis in Spain
• Treatment of Neisseria meningitidis

  Intravenous: Penicillin G (if the strain is sensitive), Cefotaxime or ceftriaxone
• Chemoprophylaxis of Neisseria meningitidis

  Rifampicin 2 doses/day for two days, Ciprofloxacin or levofloxacin (single dose), Ceftriaxone (single dose)
• Vaccines against Neisseria meningitidis

  • 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 (immunosuppressed, travelling to endemic areas, immunization Schedule 2019)
  • Recombinant proteins: vaccine against B serotype (August 2014)
• Neisseria 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
• Neisseria gonorrhoeae (gonococcus)


  Gram-negative 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

  
• Manifestations of Neisseria gonorrhoeae

  Urethritis in men, Endocervicitis in women
• Treatment of choice for Neisseria gonorrhoeae

  Cefixime or Ceftriaxone, Add doxycillin or azithromycin to cover Chlamydia

  
• 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

  
• Pseudomonas aeruginosa usually does not cause infection in healthy people
• Pseudomonas aeruginosa

  • Cutaneous infections: Folliculitis, Infections of burns, wounds, after penetrating trauma or surgery, Ecthyma gangrenosum, Other infections 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), In swimmers: Ear infections (external otitis), In eye lens users: Eye infections, conjunctivitis
• Treatment of Pseudomonas aeruginosa


  Complicated treatment due to natural resistance to multiple antibiotics and 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


  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 and animals (GI tract), Opportunistic pathogens / primary pathogens
• Enterobacteriaceae species


  • Escherichia coli, Klebsiella, Enterobacter, Citrobacter, Serratia, Proteus, Morganella, Providencia, Salmonella, Shigella, Yersinia

  
• 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

  
• Subclassification of Enterobacteriaceae in serotypes according to their antigenic structure
• Sensitivity to antibiotics of Enterobacteriaceae


  Variable depending on the species, Antibiogram (sensitivity test) required, Interpreted reading of the antibiogram

  
• Infections produced by Enterobacteriaceae

  • Urinary tract infections: urinary infection, prostatitis, Abdominal infections (peritonitis, abscesses, gastroenteritis: diarrhea, vomiting, abdominal pain), Wound infections (surgical, trauma, burns, ..), Respiratory infections (intubated, ..), Bacteremia
• Escherichia coli


  Opportunistic pathogenic strains in the intestinal microbiota: Extraintestinal symptoms like Urinary Tract Infections, Neonatal meningitis, Other, uncommon in healthy people (meningitis, sepsis…), Strict pathogenic strains, they are not in the microbiota: Gastrointestinal symptoms like Enterotoxigenic (ETEC): traveller's diarrhea, infant diarrhea, Enteropathogenic (EPEC): infant diarrhea, Enteroinvasive (EIEC), Enterohemorrhagic (EHEC)
• Shigella


  Etiological agent of bacillary dysentery: diarrhea (liquid, watery, bloody stools), vomiting, fever. In travelers due to consumption of non-chlorinated water. Species: S. dysenteriae (group A), S. flexneri (group B), S. boydii (group C), S. sonnei (group D)
• 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
• Salmonella infections


  • Gastroenteritis: Infection by ingestion of food / water, oral/fecal transmission, Acute enterocolitis (fever, diarrhea, vomiting), Usually self-limited in healthy individuals, Typhoid and paratyphoid fever: Infection by ingestion of food / water, oral/fecal transmission, Invasion without enterocolitis, Fever, nonspecific symptoms and then gastrointestinal symptoms
• Yersinia


  Mainly animal pathogens, Y. pestis: Bubonic plague, Y. enterocolitica: enterocolitis