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Vocabulary flashcards summarizing key pathogens, laboratory features, clinical manifestations, and treatments from the Unit 14 lecture on Gram-negative cocci and rods.
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Neisseria genus
Group of oxidase-positive, Gram-negative diplococci that includes commensals and the pathogens N. meningitidis and N. gonorrhoeae
Gram-negative diplococci
Microscopic appearance of paired, kidney-bean–shaped cocci typical of Neisseria species
Chocolate agar
Enriched culture medium needed for the growth of fastidious organisms such as Neisseria spp. and Haemophilus spp.
Oxidase positive
Bacteria that possess cytochrome-c oxidase; produces a purple color in the oxidase test (e.g., Neisseria, Pseudomonas)
Neisseria meningitidis
Human nasopharyngeal commensal that can cause meningitis or meningococcemia; encapsulated, droplet-transmitted, notifiable disease agent
Meningococcemia
Hematogenous dissemination of N. meningitidis, often producing petechiae, purpura, shock, and high mortality
Petechiae
Small, non-blanching red spots on skin or mucosa caused by capillary hemorrhage; classic in meningococcemia
Purpura
Larger hemorrhagic skin lesions that may accompany severe meningococcal infection
Capsular polysaccharide serogroups
Immunochemical classification of N. meningitidis (A, B, C, Y, W135, etc.) based on capsule composition
Serogroups B and C
Leading meningococcal serogroups causing disease in Spain (≈85–90 % of cases)
Conjugate vaccine
Polysaccharide capsule linked to a protein carrier to improve immunogenicity; used for N. meningitidis serogroup C and A/C/Y/W135
Recombinant protein MenB vaccine
Vaccine composed of surface proteins of N. meningitidis serogroup B, licensed since 2014
Chemoprophylaxis (meningococcus)
Preventive antimicrobial regimen for close contacts: rifampicin (2 days), single-dose ciprofloxacin, levofloxacin, or ceftriaxone
Neisseria gonorrhoeae
Fastidious, Gram-negative diplococcus causing gonorrhea; exclusive to humans and transmitted sexually or perinatally
Gonorrhea
STD characterized by urethritis in men and endocervicitis in women; may involve rectum, pharynx, conjunctiva
Ophthalmia neonatorum
Purulent conjunctivitis in newborns acquired during birth from maternal N. gonorrhoeae infection
Urethritis
Inflammation of the urethra; in men, intracellular Gram-negative diplococci seen in urethral exudate suggest gonorrhea
First-line therapy for gonorrhea
Ceftriaxone or cefixime plus doxycycline or azithromycin to cover possible Chlamydia co-infection
Pseudomonas aeruginosa
Motile, oxidase-positive, non-fermenting Gram-negative rod producing pigments (pyocyanin, pyoverdine); major opportunistic pathogen
Non-fermenting Gram-negative bacilli (NFGNB)
Group of aerobic rods (e.g., Pseudomonas, Acinetobacter) that oxidize but do not ferment sugars
Pyocyanin
Blue-green, water-soluble pigment produced by P. aeruginosa; contributes to oxidative tissue damage
Pyoverdine
Yellow-green fluorescent siderophore pigment of P. aeruginosa
Ecthyma gangrenosum
Necrotic skin lesion with central black eschar and peripheral erythema, classically linked to P. aeruginosa septicemia
Opportunistic pathogen
Organism that rarely infects healthy hosts but causes disease when barriers are breached or immunity is impaired
Antipseudomonal cephalosporin
Third-generation agent active against P. aeruginosa, e.g., ceftazidime or cefepime
Enterobacteriaceae family
Large family of oxidase-negative, Gram-negative rods that ferment glucose; includes E. coli, Salmonella, Shigella, Klebsiella, etc.
Lactose fermentation
Metabolic property tested on MacConkey agar; lactose fermenters form pink colonies, non-fermenters are colorless
MacConkey agar
Selective and differential medium for Gram-negative rods; differentiates lactose fermenters by colony color
API test
Commercial strip of biochemical reactions used for rapid identification of Enterobacteriaceae and other bacteria
Triple Sugar Iron (TSI) agar
Slant medium detecting glucose/lactose/sucrose fermentation, H₂S and gas production in enteric bacteria
H antigen
Flagellar protein antigen used for serotyping Enterobacteriaceae
K antigen
Capsular polysaccharide antigen of Enterobacteriaceae; involved in virulence
O antigen
Somatic lipopolysaccharide antigen used for epidemiologic serotyping of enteric bacteria
Escherichia coli
Common gut commensal and opportunistic pathogen; certain strains are primary pathogens causing diarrheal disease
Enterotoxigenic E. coli (ETEC)
Toxin-producing strain causing traveller’s and infantile watery diarrhea
Enteropathogenic E. coli (EPEC)
Strain causing infant diarrhea via attaching-and-effacing lesions
Enteroinvasive E. coli (EIEC)
Strain that invades colonic epithelium producing dysentery-like illness
Enterohemorrhagic E. coli (EHEC)
Shiga-toxin–producing strain causing hemorrhagic colitis and hemolytic uremic syndrome
Shigella
Non-motile Enterobacteriaceae genus causing bacillary dysentery through fecal-oral spread
Bacillary dysentery
Severe inflammatory diarrhea with blood, mucus, fever, caused by Shigella spp.
Salmonella Typhi
Human-restricted serovar causing typhoid fever via fecal-oral transmission
Typhoid fever
Systemic febrile illness with intestinal invasion caused by S. Typhi or S. Paratyphi
Salmonella Enteritidis
Zoonotic Salmonella serovar commonly producing self-limited gastroenteritis
Gastroenteritis (Salmonella)
Acute enterocolitis with fever, vomiting, and diarrhea following contaminated food or water ingestion
Carrier state
Condition in which a person harbors and sheds a pathogen without symptoms (e.g., Salmonella Typhi carriers)
Yersinia pestis
Gram-negative coccobacillus, agent of bubonic, septicemic, and pneumonic plague
Bubonic plague
Severe infection with painful, swollen lymph nodes (buboes) caused by Yersinia pestis
Yersinia enterocolitica
Enteric Yersinia species producing enterocolitis, often from contaminated pork or milk
Oxidase negative
Characteristic of Enterobacteriaceae; absence of cytochrome-c oxidase activity
Glucose fermentation
Ability to metabolize glucose anaerobically, a hallmark of Enterobacteriaceae
Peritrichous flagella
Flagellar arrangement around the entire cell surface, providing motility to many enteric rods
Oxidase test
Biochemical assay detecting cytochrome-c oxidase; differentiates oxidase-positive Pseudomonas from oxidase-negative Enterobacteriaceae
Rifampicin chemoprophylaxis
Use of rifampicin twice daily for 2 days to eradicate N. meningitidis carriage in close contacts