Medical Microbiology: Micrococcaceae, Neisseria, Listeria, Corynebacterium, and Bacillus

Vocabulary practice flashcards covering bacteriological characteristics, virulence determinants, clinical manifestations, diagnostic markers, and epidemiology for Micrococcaceae, Neisseria, Listeria, Corynebacterium, and Bacillus species.

Micrococcaceae

A bacterial family comprising Gram-positive, catalase-positive, coccoid, pigment-producing organisms, including the genera Micrococcus and Staphylococcus.

Micrococcus

A genus of Gram-positive, catalase-positive, coagulase-negative cocci that arrange in tetrads, are susceptible to bacitracin, and are generally considered non-pathogenic.

Micrococcus luteus

A non-pathogenic bacterium that is part of normal skin flora, especially on the extremities, and can also be isolated from soil.

Staphylococcus

A genus of Gram-positive, catalase-positive cocci that grow in grape-like clusters and can function as normal flora or opportunistic pathogens.

Staphylococcus saprophyticus

A species that is normal flora of human skin and genitourinary mucosa, recognized as a primary cause of community-acquired urinary tract infections in young, sexually active females.

Staphylococcus epidermidis

A normal commensal of the skin and mucous membranes that is coagulase-negative, DNase-negative, gamma-hemolytic, unable to ferment mannitol, and capable of growth in $7.5\%\,\text{NaCl}$.

Staphylococcus aureus

A coagulase-positive, DNase-positive, beta-hemolytic pathogen of the skin and upper respiratory tract that ferments mannitol, grows in $7.5\%\,\text{NaCl}$, and is the most common cause of skin infections and nosocomial infections.

Coagulase

An enzyme produced by Staphylococcus aureus that converts fibrinogen to fibrin clots, depositing a protective fibrin wall around bacterial cells to resist phagocytosis.

Leukocidin

A staphylococcal virulence factor that destroys host white blood cells, enabling immune evasion and contributing to pus formation in boils and pimples.

Toxic Shock Syndrome (TSS)

A multisystem illness caused by a staphylococcal superantigen toxin, characterized by high fever, rash, vomiting, diarrhea, cardiovascular collapse, and kidney failure, classically linked to tampon use or postoperative infections.

Staphylococcal Enterotoxin A

A superantigen responsible for food poisoning that stimulates intestinal T cells and increases mucosal permeability, causing severe but short-lived vomiting and diarrhea.

Neisseria

A genus of aerobic, Gram-negative, kidney bean-shaped diplococci that are cytochrome oxidase-positive, catalase-positive, capnophilic, and inhabit mucosal surfaces.

Capnophilic

A term describing microorganisms, such as Neisseria species, that require or grow optimally under elevated $\text{CO}_2$ concentrations and moist atmospheric conditions.

Neisseria gonorrhoeae

The fastidious Gram-negative diplococcus that causes gonorrhea by pyogenic infection of columnar epithelium in the urethra, endocervix, pharynx, anal canal, and conjunctiva.

Ophthalmia neonatorum

A gonococcal eye infection contracted by newborns during vaginal passage through an infected birth canal, preventable by mandatory prophylactic antimicrobial eye drops or silver nitrate at birth.

Ceftriaxone

The recommended antimicrobial therapy for uncomplicated Neisseria gonorrhoeae infections, effective against plasmid-mediated $\beta$-lactamase-producing and chromosomally resistant strains.

Neisseria meningitidis

The meningococcus; an encapsulated Gram-negative diplococcus carried asymptomatically in the human nasopharynx that causes epidemic meningitis and fulminant meningococcemia.

Meningococcemia

Severe Neisseria meningitidis septicemia carrying a $25\%$ mortality rate, characterized by petechial skin lesions, disseminated intravascular coagulation, septic shock, and hemorrhage.

Moraxella catarrhalis

Formerly Branhamella catarrhalis; an intracellular Gram-negative diplococcus of the human respiratory tract and the third most common cause of acute otitis media and sinusitis in children.

Listeria monocytogenes

An aerobic, non-sporeforming, Gram-positive coccobacillus displaying weak beta-hemolysis, a positive CAMP reaction, and characteristic umbrella motility in motility media at $25\,^\circ\text{C}$.

Cold enrichment

A diagnostic isolation technique that exploits the unique ability of Listeria monocytogenes to replicate at refrigerator temperatures ($4\,^\circ\text{C}$).

Listeriolysin O

A pore-forming hemolysin produced by Listeria monocytogenes that disrupts phagosomal membranes, permitting bacterial escape into the host cytosol to avoid phagocytic killing.

Early onset neonatal listeriosis

A severe congenital Listeria infection acquired in utero, typically presenting at or shortly after birth as fulminant sepsis with fatality rates approaching $50\%$.

Late onset neonatal listeriosis

A Listeria infection presenting several days to weeks after birth in full-term, initially healthy infants, typically manifesting as meningitis.

Lactobacillus

Anaerobic and microaerophilic vaginal commensals that ferment glycogen into lactic acid under estrogenic stimulation, maintaining an acidic vaginal pH of $4\text{--}5$ to suppress pathogens.

Corynebacterium diphtheriae

A pleomorphic, non-motile, non-sporeforming Gram-positive rod that arranges in palisades or sharp-angled 'Chinese character' (V and L) configurations and produces diphtheria toxin.

Pseudomembrane (Diphtheritic)

A tough, adherent, grayish-white inflammatory exudate composed of necrotic epithelial cells, fibrin, and leukocytes formed on the pharynx or tonsils by toxigenic Corynebacterium diphtheriae.

Tinsdale agar

A selective and differential medium containing sheep blood, bovine serum, cystine, and potassium tellurite, on which Corynebacterium species produce distinctive black or brownish colonies.

Corynebacterium jeikeium

A multidrug-resistant normal skin commensal that serves as the most frequent cause of diphtheroid prosthetic valve endocarditis in adult patients.

Bacillus anthracis

An aerobic, endospore-forming, Gram-positive rod whose pathogenicity requires a poly-D-glutamic acid capsule and a three-component anthrax exotoxin.

Anthrax toxin

A tripartite plasmid-encoded complex consisting of protective antigen (PA), edema factor (EF), and lethal factor (LF), where PA + EF causes edema and PA + LF causes lethality.

Bacillus cereus (Diarrheal syndrome)

A foodborne illness caused by a heat-labile enterotoxin associated with meat or poultry, characterized by an $8\text{--}16\text{ hour}$ incubation period and a $24\text{ hour}$ duration of abdominal cramps and diarrhea.

Bacillus cereus (Emetic syndrome)

A foodborne illness caused by a heat-stable toxin associated with contaminated fried rice, characterized predominantly by vomiting and nausea with an average duration of $9\text{ hours}$.