Microbiology – Pyogenic Cocci, Neisseria, Enteric & Other Bacteria (Wk 3 Final Review)

Vocabulary flashcards summarizing key organisms, virulence factors, laboratory tests, diseases, and treatment concepts from Week 3 microbiology lecture notes. Use them to reinforce definitions and recall during exam prep.

Pyogenic cocci

Spherical bacteria that produce pus-forming (suppurative) infections

Staphylococcus aureus

Gram-positive, catalase-positive coccus; major human pathogen producing coagulase and numerous toxins

Staphylococcus epidermidis

Coagulase-negative staphylococcus; common skin commensal and cause of device-related infections

Coagulase

Staphylococcal enzyme that converts fibrinogen to fibrin, helping bacteria evade phagocytosis

Protein A

Surface protein of S. aureus that binds Fc region of IgG, blocking opsonization

Catalase test

Laboratory test distinguishing staphylococci (+) from streptococci (–) by breakdown of H₂O₂

MRSA

Methicillin-resistant Staphylococcus aureus carrying mecA gene encoding altered PBP 2a

VRSA

Vancomycin-resistant Staphylococcus aureus with reduced susceptibility to glycopeptides

Exfoliative toxin

S. aureus serine protease that splits epidermal desmosomes, causing scalded-skin syndrome

Enterotoxin A

Heat-stable S. aureus toxin most commonly implicated in food poisoning

Toxic Shock Syndrome Toxin-1 (TSST-1)

Superantigen of S. aureus causing systemic rash, fever, hypotension and multiorgan failure

Folliculitis

Superficial infection of hair follicles, often due to S. aureus

Carbuncle

Deep, interconnected group of boils extending into subcutaneous tissue

Scalded Skin Syndrome (SSSS)

Exfoliative-toxin-mediated blistering disease of neonates and children

Staphylokinase

Fibrinolysin of S. aureus that dissolves clots and aids spread

Streptococcus pyogenes (GAS)

Group A β-hemolytic streptococcus causing pharyngitis, skin infections and sequelae

M protein

Antiphagocytic surface protein of S. pyogenes; basis of emm typing

Streptolysin O

Oxygen-labile hemolysin of GAS; antibodies (ASO) indicate recent infection

Streptolysin S

Oxygen-stable hemolysin responsible for β-hemolysis seen around GAS colonies

Streptokinase

GAS enzyme that activates plasminogen, dissolving fibrin clots

C5a peptidase

GAS protease that inactivates complement chemotaxin C5a

Rheumatic fever

Post-streptococcal autoimmune disease affecting heart, joints and CNS

Acute glomerulonephritis

Immune-complex renal disease following GAS pharyngitis or skin infection

Necrotizing fasciitis

Rapidly destructive soft-tissue infection (“flesh-eating disease”) often due to GAS or S. aureus

Streptococcal Toxic Shock Syndrome

Severe systemic GAS infection with shock and organ failure, usually bacteremic

Streptococcus agalactiae (GBS)

Group B streptococcus causing neonatal sepsis, meningitis and maternal infections

Early-onset GBS disease

Neonatal sepsis/pneumonia within first 7 days, acquired from vaginal colonization

Late-onset GBS disease

GBS meningitis or sepsis appearing 1 week–3 months after birth

Streptococcus pneumoniae

Encapsulated α-hemolytic diplococcus; major cause of pneumonia, meningitis, otitis

Pneumolysin

S. pneumoniae cytotoxin that lyses cells and activates complement

Capsular polysaccharide

Principal pneumococcal virulence factor; basis of >90 serotypes and vaccines

Neisseria gonorrhoeae

Gram-negative diplococcus (“gonococcus”) causing gonorrhea and disseminated infection

Pili (Neisseria)

Hairlike structures mediating attachment, antigenic variation and resistance to phagocytosis

OPA proteins

Opacity proteins of N. gonorrhoeae that promote intimate binding to epithelial cells

Lipooligosaccharide (LOS)

Endotoxin of Neisseria lacking O-antigen; triggers inflammation and immune evasion

Ophthalmia neonatorum

Gonococcal conjunctivitis acquired during birth; prevented with ocular prophylaxis

Neisseria meningitidis

Capsulated gram-negative diplococcus causing meningitis and meningococcemia

Fulminant meningococcemia

Rapid septicemic N. meningitidis infection with petechiae, DIC and shock

Ty21a vaccine

Oral live-attenuated vaccine against Salmonella Typhi

Enterobacteriaceae

Large family of gram-negative rods inhabiting gut; ferment glucose, oxidase-negative

O antigen

Somatic LPS polysaccharide used for serotyping enteric bacteria

H antigen

Flagellar antigen of enteric bacteria

K antigen

Capsular antigen of enteric bacteria

Escherichia coli

Common gut commensal; leading cause of UTIs and diverse diarrheal diseases

Uropathogenic E. coli (UPEC)

Strains with P fimbriae and hemolysin causing cystitis and pyelonephritis

Enterotoxigenic E. coli (ETEC)

Produces heat-labile (LT) and heat-stable (ST) toxins; traveler’s and childhood diarrhea

Enteropathogenic E. coli (EPEC)

Forms attaching-and-effacing lesions; infantile watery diarrhea

Enterohemorrhagic E. coli (EHEC/STEC)

Shiga-toxin-producing strains (e.g., O157:H7) causing hemorrhagic colitis and HUS

Enteroinvasive E. coli (EIEC)

Non-motile strains that invade colonic epithelium, causing dysentery-like illness

Enteroaggregative E. coli (EAEC)

Adheres in “stacked brick” pattern; persistent diarrhea in children and HIV patients

Klebsiella pneumoniae

Mucoid, non-motile enteric rod causing lobar pneumonia and UTIs; produces “currant-jelly” sputum

Klebsiella granulomatis

Agent of granuloma inguinale (donovanosis), a chronic genital ulcer disease

Enterobacter cloacae

Hospital pathogen with inducible AmpC β-lactamase; causes UTIs, pneumonia

Serratia marcescens

Red-pigmented opportunist with AmpC; associated with catheter and urine infections

Proteus mirabilis

Highly motile, urease-positive rod causing swarming on agar and kidney stones

Providencia stuartii

Enteric rod implicated in catheter-associated UTIs, especially in nursing homes

Shigella dysenteriae

Non-motile, non-lactose fermenter producing Shiga toxin; causes bacillary dysentery

Hemolytic uremic syndrome (HUS)

Triad of hemolytic anemia, renal failure, thrombocytopenia after Shiga toxin exposure

Salmonella Typhi

Human-restricted serovar causing typhoid (enteric) fever

Rose spots

Blanching pink macules on trunk in typhoid fever

Widal test

Serologic agglutination test detecting antibodies to Salmonella O and H antigens

Yersinia pestis

Safety-pin-staining rod; agent of bubonic and pneumonic plague

Yersinia enterocolitica

Cold-tolerant enteroinvasive rod causing pseudoappendicitis and diarrhea

Pseudomonas aeruginosa

Non-fermenting gram-negative rod producing pyocyanin; opportunist in burns and CF

Ecthyma gangrenosum

Necrotic skin lesions due to P. aeruginosa bacteremia

Vibrio cholerae O1/O139

Comma-shaped halotolerant rod whose cholera toxin causes profuse watery diarrhea

Rice-water stool

Watery, fleck-laden feces characteristic of cholera

Campylobacter jejuni

Curved microaerophilic rod; leading bacterial cause of gastroenteritis and GBS trigger

Helicobacter pylori

Urease-positive spiral rod causing gastritis, peptic ulcers and gastric cancer

Haemophilus influenzae type b (Hib)

Encapsulated gram-negative coccobacillus causing pediatric meningitis and epiglottitis

X factor

Hemin growth factor required by many Haemophilus species

V factor

NAD/NADP required for growth of Haemophilus on chocolate agar

Satellitism

Growth of H. influenzae around S. aureus colonies supplying V factor on blood agar

Haemophilus ducreyi

X-factor-dependent bacillus causing chancroid (painful genital ulcer)

Bordetella pertussis

Strict aerobe causing whooping cough; produces pertussis toxin and FHA

Catarrhal stage

Initial, highly contagious phase of pertussis with mild respiratory symptoms

Paroxysmal stage

Phase of pertussis with characteristic whooping cough and posttussive vomiting

Brucella melitensis

Gram-negative zoonotic coccobacillus causing undulant fever (brucellosis)

Gardnerella vaginalis

Gram-variable rod associated with bacterial vaginosis and “clue cells”

Clostridium tetani

Obligate anaerobic bacillus with terminal spore; produces tetanospasmin causing tetanus

Opisthotonos

Extreme arching of back due to tetanic spasms

Clostridium perfringens

Gas-gangrene bacillus producing α-toxin and enterotoxin; causes myonecrosis and food poisoning

Hyperbaric oxygen therapy

Adjunct treatment delivering high O₂ to inhibit clostridial anaerobes in gas gangrene

Clostridioides difficile

Spore-forming anaerobe producing toxins A/B; leading cause of antibiotic-associated colitis

Pseudomembranous colitis

Severe C. difficile colitis with yellow plaques on colon mucosa

Clostridium botulinum

Anaerobe whose neurotoxin blocks acetylcholine release, causing flaccid paralysis

Actinomyces israelii

Filamentous gram-positive anaerobe causing cervicofacial “lumpy jaw”

Nocardia asteroides

Partially acid-fast branching rod causing pulmonary and CNS abscesses in immunocompromised

Corynebacterium diphtheriae

Club-shaped gram-positive rod producing diphtheria toxin and pseudomembrane

Elek test

In-vitro immunodiffusion assay for toxigenic C. diphtheriae

Schick test

Skin test for diphtheria susceptibility using intradermal toxin

Mycobacterium tuberculosis

Acid-fast bacillus causing pulmonary and extrapulmonary tuberculosis

PPD (Purified Protein Derivative)

Antigen used in Mantoux skin test for latent TB infection

Lowenstein-Jensen medium

Egg-based medium for culturing mycobacteria

Mycobacterium bovis

Cattle TB bacillus; basis of BCG vaccine and transmissible via unpasteurized milk

Mycobacterium leprae

Slow-growing bacillus causing Hansen’s disease (leprosy)

Lepromin test

Skin test indicating cell-mediated immunity to M. leprae (Mitsuda reaction)

Photochromogen

Runyon group of mycobacteria producing pigment only on light exposure (e.g., M. kansasii)

Runyon groups

Classification of nontuberculous mycobacteria by pigment and growth rate

Bacteroides fragilis

Gram-negative anaerobic rod; leading cause of intra-abdominal abscesses