MED MICRO EXAM 2 KILLER

Bacillus

large, aerobic, Gram-positive rods that occur in chains and have square ends.

Bacillus anthracis

Produces anthrax and has a capsule encoded by plasmid pXO2, while plasmid pXO1 encodes protective antigen (PA), edema factor (EF), and lethal factor (LF); EF acts as an adenylate cyclase, while LF contributes to lethality. Human infection can be cutaneous, gastrointestinal, inhalational, or injection-related, with approximately 95% of cases being cutaneous and 5% inhalational; the notes list ciprofloxacin and an available vaccine.

Bacillus cereus

Causes food intoxication through an emetic type associated with fried rice, milk, and pasta, or a diarrheal type associated with meat dishes and sauces. It can also cause severe eye infections, including keratitis and endophthalmitis, and is resistant to several antimicrobials, including penicillins and cephalosporins; vancomycin or clindamycin may be used for serious non-foodborne infections.

Clostridium

anaerobic, Gram-positive, motile rods that may decompose proteins or produce toxins; they are found in soil, marine sediments, sewage, and animal or human intestinal tracts.

Clostridium botulinum

Produces botulinum toxin, which blocks acetylcholine release at synapses and neuromuscular junctions, causing flaccid paralysis without crossing the blood–brain barrier or directly affecting the CNS. Botulism may result from contaminated foods, honey-associated infant botulism, contaminated wounds, or inhalation, and its spores are highly heat-resistant, potentially surviving 100°C for several hours.

Clostridium tetani

Produces tetanospasmin, which causes spastic paralysis and is associated with contaminated wounds and devitalized or necrotic tissue. Tetanus prevention relies on toxoid immunization.

Clostridium perfringens

Produces alpha toxin (lecithinase) and is strongly associated with gas gangrene and myonecrosis; it can also cause foodborne diarrhea, with symptoms occurring approximately 7–30 hours after ingestion according to the reviewer.

Clostridium difficile

Associated with antibiotic use and pseudomembranous colitis; toxin A binds to the intestinal brush border, while toxin B has cytotoxic activity. The notes also mention fecal transplantation as a treatment approach.

Corynebacterium diphtheriae

Causes diphtheria, including membranous pharyngitis, and its toxin inhibits protein synthesis by inactivating elongation factor 2 (EF-2). Toxin fragment A has enzymatic activity, while fragment B is involved in receptor binding and translocation; complications include myocarditis and renal failure.

Listeria monocytogenes

A foodborne pathogen capable of surviving refrigerator temperatures, low pH, and high salt concentrations; it is motile at room temperature and produces listeriolysin O, which supports intracellular survival and cell-to-cell spread through actin polymerization. It can cause meningoencephalitis and bacteremia, and the notes list ampicillin, erythromycin, and intravenous trimethoprim-sulfamethoxazole as treatments while noting that cephalosporins and fluoroquinolones are inactive.

Staphylococci

are aerobic or microaerophilic, catalase-positive cocci, unlike streptococci; S. aureus is coagulase-positive, while the other major species covered are coagulase-negative.

Staphylococcus aureus

Produces Protein A, a polysaccharide capsule, clumping factor, hemolysins, toxic shock syndrome toxin (a superantigen), and a heat-stable enterotoxin resistant to gut enzymes. Resistance mechanisms include beta-lactamase production, resistance to nafcillin/methicillin/oxacillin, and possible vancomycin resistance; the notes define VRSA as having a vancomycin MIC of at least 16 µg/mL.

Staphylococcus epidermidis

Part of the normal skin microbiota and an important opportunistic pathogen associated with implanted medical devices; the notes attribute approximately 75% of the infections in the particular context discussed to this species.

Staphylococcus saprophyticus

A coagulase-negative staphylococcus associated with urinary tract infections (UTIs).

Streptococci

are classified using hemolysis on blood agar, Lancefield cell-wall antigens, biochemical reactions, and ecological features; pyogenic streptococci are generally more pathogenic, whereas viridans streptococci are often normal microbiota but can cause opportunistic infections.

Viridans streptococci

Common members of the normal upper respiratory tract microbiota and important causes of endocarditis on abnormal heart valves. They are usually alpha-hemolytic but may be nonhemolytic, are not inhibited by optochin, and have colonies that are insoluble in bile.

Streptococcus pyogenes

A Group A, beta-hemolytic streptococcus whose M protein is an important virulence factor; it causes pharyngitis, impetigo/pyoderma, erysipelas, cellulitis, necrotizing fasciitis, puerperal fever, bacteremia, toxic shock, and scarlet fever.

Streptococcus agalactiae

A Group B, beta-hemolytic streptococcus associated with vaginal and gastrointestinal microbiota; identification clues include positive hippurate hydrolysis and the CAMP test. The notes recommend IV ampicillin during labor in the relevant prevention context.

C and G streptococci

Associated with the nasopharynx and may cause pharyngitis, sinusitis, bacteremia, and endocarditis.

Streptococcus bovis

A Group D streptococcus that is generally nonhemolytic, PYR-negative, bile-esculin-positive, and unable to grow in 6.5% NaCl; bacteremia or endocarditis may be associated with biliary disease and colonic pathology, including carcinoma.

Streptococcus pneumoniae

A Gram-positive, lancet-shaped diplococcus that is alpha-hemolytic and possesses a capsule; it is associated with pneumonia, and the notes list PPSV23 and PCV13 vaccines.

Group D

Enterococcus faecalis and Enterococcus faecium, catalase-negative cocci that are PYR-positive, bile-esculin-positive, and capable of growth at 10–45°C; they can cause UTIs, bacteremia, and endocarditis. The notes emphasize intrinsic resistance to several antibiotic classes, including cephalosporins, penicillinase-resistant penicillins, and monobactams, as well as vancomycin resistance.

Enterobacteriaceae

are Gram-negative rods that are facultative anaerobes and commonly inhabit the intestinal tract; they characteristically ferment carbohydrates, and several members cause intestinal and extraintestinal infections.

Escherichia coli

Associated with UTIs, diarrheal disease, sepsis, and meningitis; its diarrheagenic pathotypes are distinguished by their clinical patterns. EPEC causes infant diarrhea, ETEC causes travelers’ diarrhea and diarrhea in young children, STEC causes hemorrhagic colitis and hemolytic uremic syndrome (HUS), EIEC causes a Shigella-like illness, and EAEC is associated with acute or chronic diarrhea.

Shigella dysenteriae

Causes bacillary dysentery and produces Shiga toxin, particularly serotype/type I as highlighted in the notes; it has a low infectious dose of approximately 10210^2102 organisms, and disease is primarily confined to the gastrointestinal tract.

Salmonella enterica

The notes identify these as Salmonella species and discuss typhoidal and nontyphoidal infections, including enteric fever, septicemia, and enterocolitis. For enteric fever, the notes list azithromycin for uncomplicated disease and third-generation cephalosporins or fluoroquinolones for hospitalized patients with complications.

Pseudomonas aeruginosa

A motile, Gram-negative rod and obligate aerobe that produces a sweet, grape-like, or corn-taco-like odor and distinctive pigments: pyocyanin (blue), pyoverdine (fluorescent greenish), pyorubin (dark red), and pyomelanin (black). Alginate promotes mucoid colonies and biofilm formation, especially in cystic fibrosis; exotoxin A causes tissue necrosis, and infections include wounds, meningitis, UTIs, chronic CF pneumonia, and ecthyma gangrenosum, with piperacillin plus tobramycin listed in the notes.

Acinetobacter baumannii

An important multidrug-resistant (MDR) nosocomial pathogen, particularly in critically ill or ICU patients.

Burkholderia cepacia

An environmental organism and opportunistic pathogen.

Vibrio cholerae

A motile, comma-shaped curved rod that forms yellow colonies on TCBS agar; its cholera toxin activates adenylate cyclase through persistent G-protein signaling, increasing cAMP and promoting chloride, bicarbonate, and water secretion into the intestine. It causes cholera, typically without invading intestinal tissue, and management emphasizes water and electrolyte replacement; the notes also mention tetracycline as an effective antimicrobial.

Campylobacter jejuni

A microaerophilic, curved rod that may appear comma-shaped, S-shaped, or gull-wing-shaped and causes gastroenteritis lasting approximately 5–8 days. An important post-infectious complication is Guillain–Barré syndrome, and macrolides are listed as treatment.

Helicobacter pylori

A gastric pathogen identifiable by its urease activity and associated with chronic gastric colonization, gastritis, peptic and duodenal ulcers, gastric adenocarcinoma, and MALT lymphoma. The notes list triple therapy consisting of a proton-pump inhibitor (PPI), amoxicillin, and clarithromycin.

Haemophilus influenzae

A small, pleomorphic Gram-negative coccobacillus that grows on chocolate agar and requires Factor X (hemin) and Factor V (NAD); it may show satellitism around Staphylococcus aureus on sheep blood agar because staphylococci release Factor V. Type b possesses a capsule and is associated with meningitis, especially in unvaccinated children.

Haemophilus ducreyi

Causes chancroid, a sexually transmitted infection associated with genital ulceration.

Bordetella pertussis

A minute, strictly aerobic Gram-negative coccobacillus cultured on Bordet–Gengou or charcoal-containing media; filamentous hemagglutinin (FHA) and fimbriae help attachment, pertussis toxin contributes to lymphocytosis and other systemic effects, and tracheal cytotoxin damages respiratory epithelium. It causes whooping cough, progressing through the catarrhal, paroxysmal, and convalescent stages, and infection does not provide lifelong immunity.

Francisella tularensis

Causes tularemia and requires cysteine- and hemin-rich media; Type A is more severe and potentially lethal, while Type B is generally milder. Clinical forms include pneumonic, oculoglandular, glandular, oropharyngeal, and typhoidal tularemia; the notes list streptomycin or gentamicin and state that the organism is resistant to beta-lactams.

Yersinia pestis

A Gram-negative organism associated with plague and the characteristic bipolar, safety-pin appearance; it is associated with rodents and flea transmission, especially the rat flea Xenopsylla cheopis. Virulence features include V and W antigens, a type III secretion system, and yersiniabactin; clinical forms are bubonic, pneumonic, and septicemic plague, and the notes list streptomycin or gentamicin.

Pasteurella multocida

A nonmotile Gram-negative coccobacillus found in the respiratory and gastrointestinal tracts of domestic and wild animals; human infection is particularly associated with cat and dog bite wounds, and penicillin G is listed as the drug of choice.

Neisserie

Gram-negative diplococci that may be found intracellularly in polymorphonuclear leukocytes (PMNs); the pathogenic species covered in the notes are associated with humans.

Neisseria gonorrhoeae

A gonococcus that lacks a capsule and oxidizes glucose only; it causes genital and other mucosal infections, forms transparent or opaque colonies, and uses pili, Por proteins, Opa proteins, and Rmp to attach to host cells and evade host defenses. Antigenic variation contributes to immune evasion, and the notes emphasize possible coinfection with Chlamydia trachomatis and ceftriaxone treatment.

Neisseria meningitidis

A meningococcus possessing a polysaccharide capsule, commonly found in the upper respiratory tract and capable of causing meningitis and meningococcemia. Important features include serogroups A, B, C, X, Y, and W-135, as well as potentially fulminant disease with hemorrhagic rash; the notes list penicillin G as treatment.

Bacteroides fragilis

Identified in the notes as the most important anaerobic pathogen and a member of the normal microbiota that can cause disease when introduced into normally sterile sites.

Gardnerella vaginalis

A Gram-variable bacillus associated with bacterial vaginosis.

Legionella pneumophila

A fastidious, aerobic Gram-negative bacterium that stains poorly with Gram stain and grows on buffered charcoal yeast extract (BCYE) agar containing alpha-ketoglutarate, L-cysteine, and iron. it causes Pontiac fever or Legionnaires’ disease, and the notes list macrolides, quinolones, and tetracyclines.

Bartonella bacilliformis

An intracellular, Gram-negative, pleomorphic rod associated with Oroya fever, which can involve severe anemia, and verruga peruana.

Bartonella quintana

Associated with trench fever.

Bartonella henselae

Associated with cat-scratch disease and bacillary angiomatosis; Bartonella species are slow-growing and intracellular.

Streptobacillus moniliformis

An aerobic, Gram-negative, pleomorphic rod that may form irregular chains with fusiform enlargements; it causes rat-bite fever and Haverhill fever, and the notes mention an L-form.

Mycobacteria

aerobic, non-spore-forming rods with a lipid-rich cell wall containing mycolic acids and waxes, contributing to acid-fast staining, slow growth, and resistance to drying and various chemical agents. The notes identify Middlebrook and Lowenstein–Jensen (LJ) media for culture

Mycobacterium tuberculosis

Causes tuberculosis (TB) and produces exudative lesions or productive granulomas; caseous granulomas may break into bronchi and form cavities, while lesions may heal through fibrosis or calcification. The notes discuss Ghon lesions, positive tuberculin tests, and multidrug-resistant TB; first-line drugs listed are isoniazid (INH), rifampicin (RMP), pyrazinamide (PZA), and ethambutol (EMB).

Mycobacterium leprae

Causes leprosy.

Mycobacterium ulcerans

Causes Buruli ulcer.

Spirochetes

endoflagella (axial filaments) that support their characteristic motility.

Treponema pallidum

A slender, actively motile spirochete that causes syphilis and is difficult to visualize using routine methods; the notes mention dark-field illumination, immunofluorescence, and silver impregnation, and state that it has not been continuously cultured on artificial media. Syphilis may progress from local infection to systemic and later tertiary disease, including gummas, cardiovascular lesions, and neurological damage; congenital infection may cause fetal loss or characteristic abnormalities, and penicillin is treponemicidal.

Borrelia recurrentis

ransmitted by the human body louse and causes relapsing fever because antigenic variants multiply and evade existing immune responses

Borrelia burgdorferi:

Transmitted by the tick Ixodes scapularis and causes Lyme disease, which may progress through three stages and involve the skin and nervous system.

Leptospira interrogans

A tightly coiled, thin, flexible, actively motile spirochete with an end that may bend into a hook shape; it derives energy from oxidation of long-chain fatty acids rather than using amino acids or carbohydrates as major energy sources.

Mycoplasma

very small, highly pleomorphic bacteria, with the smallest described in the notes measuring approximately 125–250 nm; they lack a cell wall and instead possess a triple-layered membrane containing sterol.

Mycoplasma pneumoniae

Associated with pneumonia and belongs to the group of cell wall-deficient organisms, making beta-lactams such as penicillin ineffective; the notes list tetracyclines and erythromycin as active agents.

Mycoplasma hominis

Associated with postpartum infections and infections involving the uterine tubes.

Ureaplasma urealyticum

Associated with nongonococcal urethritis (NGU) and lung disease in premature infants.

Mycoplasma genitalium

Associated with urogenital infections.

Rickettsia

obligate intracellular, arthropod-transmitted, pleomorphic coccobacilli that stain poorly with routine Gram staining; Giemsa staining may be used, and infections commonly feature fever, rash, and vasculitis.

Coxiella burnetii

Causes Q fever and is associated with sheep, goats, and cattle; transmission can occur through inhalation of contaminated aerosols, while ticks are also mentioned in its epidemiology. The notes emphasize its ability to survive drying and persistence in dried feces or milk, and list doxycycline as treatment.