Bugs and Drugs Flashcards
Bacillus anthracis
Gram positive rod, aerobic
Dx: eschar, hemorrhagic mediastinitis, bloody diarrhea
Tx: ciprofloxacin (alt: doxycycline)
Bacillus cereus
Gram positive rod, aerobic
Dx: vomiting (heat-stable toxin), diarrhea (heat-labile toxin)
Tx: supportive
Clostridium tetani
Gram positive rod, anaerobic
Dx: localized/generalized muscle spasm/rigidity with sweating, arrhythmias, and respiratory failure
Tx: tetanus antitoxin globulin, tetanus toxoid, metronidazole or penicillin
Clostridium perfringens
Gram positive rod, anaerobic
Dx: gas gangrene, food poisoning (cramps and watery diarrhea), necrotizing enteritis
Tx: penicillin and clindamycin, wound debridement if applicable
Clostridium botulinum
Gram positive rod, anaerobic
Dx: bilateral descending flaccid paralysis from home canned foods and honey
Tx: 3 valent botulinum antitoxin, metronidazole or penicillin
Clostridium difficile
Gram positive rod, anaerobe
Dx: pseudomembranous colitis (fever, abdominal pain, non-bloody diarrhea with abx use)
Tx: metronidazole (alt: vancomycin)
Corynebacterium diphtheriae
Gram positive rod, aerobe
Dx: fever, sore throat, gray pseudomembrane on tonsils/pharynx causing airway obstruction, arrhythmias, or nerve palsy
Tx: diphtheria antitoxin, penicillin or erythromycin (preventable with vaccine)
Listeria monocytogenes
Gram positive rod, facultative
Dx: gastroenteritis (watery diarrhea), meningitis (neonates/elderly/AIDS) with sepsis
Tx: ampicillin and gentamicin (alt: TMP-SMX)
Nocardia asteroides
Gram positive rod, aerobe
Dx: weakly acid fast filament-like rods, causes nocariosis, pneumonia, cellulitis, and abscesses in immunocompromised
Tx: TMP-SMX
Propionibacterium acnes
Gram positive rod, anaerobe
Dx: acne
Tx: benzoyl peroxide (topical) –> erythromycin/clindamycin (topical) –> minocycline (oral)
Staphylococcus aureus
Gram positive cocci, catalase + coagulase +
Dz:
- Acute osteomyelitis
- Skin infections: impetigo, cellulitis, post-surgical wounds
- Tricuspid valve endocarditis (IVDU) or acute endocarditis (mitral)
- Post influenzal pneumonia with empyema (HAP and VAP)
- Postpartum mastitis
- Sepsis and bacteremia
- Toxigenic: TSS, gastroenteriti, scalded skin syndrome
Tx: methicillin (MSSA), vancomycin (MRSA), linezolid (VISA/VRSA), cefazolin (prophylaxis)
Staphylococcus epidermidis
Gram positive cocci, catalase + coagulase -
Dz: implant related infections (heart valves, joints, catheters, shunts)
Tx: vancomycin
Staphylococcus saprophyticus
Gram positive cocci, catalase + coagulase -
Dz: UTI in sexually active women (2nd to E. coli)
Tx: fluoroquinolone (ciprofloxacin)
Streptococcus pyogenes
Gram positive cocci, catalase - beta-hemolytic bacitracin-sensitive
Dz:
- Skin infections: impetigo, cellulitis, necrotizing fasciitis, lymphangitis
- Pharyngitis
- Acute rheumatic fever
- Acute glomerulonephritis
- Toxigenic: toxic shock syndrome, scarlet fever
Tx: penicillin G
Streptococcus agalactiae (GBS)
Gram positive cocci, catalase - beta-hemolytic bacitracin resistant
Dz: neonatal pneumonia, meningitis, and sepsis
Tx: Penicillin G and gentamycin if severe
Enterococcus (E. faecalis, E. faecium)
Gram positive cocci, Group D, + growth in 6.5% NaCl
Dz: subacute bacterial endocarditis, UTIs, intraabdominal infections
Tx: penicillin G and gentamycin (B-lactam resistant: vancomycin and gentamycin; Vancomycin resistant: linezolid)
Streptococcus bovis
Gram positive cocci, Group D, - growth in 6.5% NaCl
Dz: subacute bacterial endocarditis associated with colon cancer
Tx: penicillin G (alt: vancomycin)
Streptococcus pneumoniae
Gram positive cocci, alpha-hemolytic, optochin sensitive
Dz: pneumonia, meningitis, otitis media, sinusitis, sepsis in asplenic patients
Tx: penicillin G (severe infection: ceftriaxone + vacomycin or newer fluoroquinolone)
Vaccine: 7 valent-conjugated polysaccharide (< 2 yrs), 23 valent-capsular polysaccharide (> 2 yrs)
Viridans streptococci
(S. mutans, S. mitis, S. sanguis, S. salivarius)
Gram positive cocci, catalase - alpha-hemolytic optochin resistant
Dz: dental plaque (S. mutans), subacute bacterial endocarditis (S. sanguis)
Tx: penicillin + gentamycin (alt: cephalosporin or vancomycin if severe), penicillin prophylaxis for dental procedures in valve disease
Neisseria meningitidis
Gram negative cocci, oxidase +, maltose fermentation +
Dz:
- Meningitis (CSF: icnreased PMN and protein, decreased glucose)
- Meningococcemia (Waterhouse-Friderichsen syndrome: fever, purpura, shock, DIC, bilateral adrenal hemorrhage)
- Pneumonia
Tx: penicillin G or ceftriaxone (alt: chloramphenicol)
Neisseria gonorrhoeae
Gram negative cocci, oxidase +, maltose fermentation -
Dz: purulent arthritis (wrist/ankle/knees), conjunctivitis, cervicitis, urethritis, pharyngitis, pustules on erythematous base
Tx: ceftriaxone and azithromycin for chlamydia
Alt: ciprofloxacin in penicillin allergy or specinomycin in pregnancy
Moraxella catarrhalis
Gram negative cocci, oxidase +
Dz: bronchitis and bronchopneumonia, otitis, sinusitis
Tx: **amoxicillin-clavulanate, cefuroxime axetil, TMP-SMX, azithromycin **
Escherichia coli
Gram negative rod, facultative, lactose fermenter
Dz:
- Gastroenteritis (Traveler’s diarrhea):
- EPEC/ETEC: watery diarrhea
- EHEC: shiga toxins → bloody diarrhea, HUS
- EIEC: dysenteric darrhea
- UTIs
- Neonatal meningitis, sepsis
Tx: supportive +/- rifaximin or fluoroquinolone for diarrhea, fluoroquinolone or TMP-SMX for UTIs, ceftriaxone for meningitis/sepsis
Klebsiella pneumoniae
Gram negative rod, lactose fermenter
Dz: nosocomial and community acquired infections in alcoholics, diabetics, and elderly including lobar pneumonia and UTIs
Tx: carbapenem (MDR: based on susceptibilities)
Enterobacter cloacae
Gram negative rod, lactose fermenter
Dz: nosocomial infections including pneumonia and UTI
Tx: carbapenem (MDR: based on susceptibilities)
Serratia marcescens
Gram negative rods, lactose fermenter
Dz: nosocomial infections in immunocompromised including pneumonia and UTI
Tx: G3 cephalosporin + gentamicin (MDR: based on susceptibilities)
Shigella dysenteriae
Gram negative rod, non-lactose fermenter, oxidase -, H2S -
Dz: bacillary dysentery (fever, cramps, tenesmus, blood stools with neutrophils and mucus)
Tx: supportive care +/- fluoroquinolone or TMP-SMX
Salmonella typhi
Gram negative rod, non-lactose fermenter, oxidase -, H2S +
Dz: enteric (typhoid) fever (bradycardia, abdominal pain, diarrhea and constipation, rose spots on trunk, hepatosplenomegaly, delirium, GI bleeding (*developing countries)
Tx: ciprofloxacin or ceftriaxone (alt: chloramphenicol), cholecystectomy if chronic carrier in gallbladder
Salmonella enteritidis
Gram negative rod, non-lactose fermenter, oxidase -, H2S +
Dz: enteritis (fever, nausea, vomiting, abdominal pain, bloody or nonbloody diarrhea)
Tx: self-limited, supportive only, no abx
Proteus mirabilis
Gram negative rod, non-lactose fermenter, oxidase -, H2S +, urease +
Dz: nosocomial UTI with struvite stones (catether associated)
Tx: ampicillin or SMX-TMP
Yersinia enterocolitica
Gram negative rod, non-fermenter, oxidase -, H2S -
Dz: enterocolitis, autoimmune complications (Reiter’s syndrome, reactive polyarthritis, erythema nodosum)
Tx: fluoroquinolone or TMP-SMX
Yersinia pestis
Gram negative rod, non-lactose fermenter, oxidase -, H2S-
Dz: bubonic plague, pneumonic plague, septicemic plague
Tx: streptomycin, doxycycline
Campylobacter jejuni
Gram negative rod (comma shaped)
Dz: acute enteritis (bloody diarrhea), autoimmune (Guillain-Barre, Reiter’s syndrome, reactive arthritis)
Tx: supportive if mild, erythromycin if severe
Helicobacter pylori
Gram negative rod (comma shaped), urease breath test +
Dz: gastritis, peptic ulcers, gastric carcinoma
Tx: **omeprazole + amoxicillin + clarithromycin **
Vibrio cholerae
Gram negative rod (comma shaped)
Dz: cholera (severe watery diarrhea with electrolyte loss)
Tx: fluid and electrolyte replacement, doxycycline or TMP-SMX
Vibrio parahaemolyticus
Gram negative rod (comma shaped)
Dz: explosive watery diarrhea from undercooked seafood
Tx: rehydration, self-limited, no abx
Pseudomonas aeruginosa
Gram negative rod, non-lactose fermenter, strict aerobe, oxidase +, catalase +
Dz:
- Pneumonia in CF
- Eyes/Ears: corneal infections, external otitis (malignant), hot tub folliculitis
- Osteomyelitis and endocarditis in IVDU
- Burn wound infections
- UTIs with catheters
- Sepsis
Tx: ticarcillin + tobramycin (aminoglycoside) or cefepime or **imipenem + ciprofloxacin **
Bordetella pertussis
Gram negative rod (coccobacillus)
Dz: whooping cough
Tx: erythromycin
Vaccine: killed vaccine in infants, acellular vaccine in children > 15 months
Legionella pneumophila
Gram negative rod, faint gram stain, silver stain +, urine antigen +
Dz: Legionnaires’ disease (atypical pneumonia) in elderly and immunocompromised, Pontiac fever (flu-like)
Tx: azithromycin (macrolides) or fluoroquinolones
Coxiella burnetii
Gram negative rod, intracellular, Giemsa stain +
Dz: Q fever (fever, pneumonia, hepatitis, meningoencephalitis, and endocarditis)
Tx: doxycycline
Haemophilus influenzae
Gram negative rod (coccobacillus), grows on heme enriched chocolate agar, PRP +
Dz: pneumonia, otitis media, sinusitis, epiglottitis, meningitis
Tx: ceftriaxone for meningitis or epiglottitis, amoxicillin clavulanate or cefuroxime axetil or TMP-SMX or azithromycin for otitis media/sinusitis
Haemophilus aegyptius
Gram negative rod (coccobacillus)
Dz: conjunctivitis (pink eye)
Tx: azithromycin (topical)
Haemophilus ducreyi
Gram negative rod (coccobacillus)
Dz: chancroid
Tx: azithromycin (macrolide) or ceftriaxone
Pasturella multocida
Gram negative rod (coccobacillus)
Dz: cellulitis and lymphadenitis from cat or dog bites
Tx: penicillin G
Brucella abortus/melitensis/suis
Gram negative rods (coccobacillus), zoonotic
Dz: brucellosis (udulant fever, adenopathy, hepatosplenomegaly, septic arthritis, vertebral osteomyelitis)
Tx: streptomycin + doxycycline (alt: TMP-SMX in pregnancy and children)
Bacteroides fragilis
Gram negative rod, anaerobe
Dz: bacteremia/sepsis, abdominal and pelvic abscesses, peritonitis, cutaneous and soft tissue infections
Tx: metronidazole
Prophylaxis: cefoxitin before abdominal or pelvic surgery
Fusobacterium nucleatum
Gram negative rod, anaerobe
Dz: abscesses (brain, lung, abdominal, pelvic)
Tx: metronidazole
Prevotella melaninogenica
Gram negative rod, anaerobe
Dz: abscesses (brain, lung)
Tx: metronidazole
Bartonella henselae
Gram-variant rod, silver stain +
Dz: cat-scratch fever (fever and purulent lymphadenitis), bacillary angiomatosis (wide spread vascular lesions and nodules) and bacillary peliosis (vascular lesions in liver/spleen) in immunocompromised
Tx: azithromycin
Gardnerella vaginalis
Gram-variant rod
Dz: bacterial vaginosis (foul smelling discharge with clue cells)
Tx: metronidazole
Mycobacterium tuberculosis
Mycobacteria, aerobic, acid fast stain +
Dz:
- Pulmonary TB: fever, sweats, weight loss, hemoptysis
- Primary: Ghon complex
- Secondary: fibrocaseous cavitary lesions in apices
- Extrapulmonary TB: spread to LN, pleura, CNS, GU, GI, and vertebral bodies
- Miliary TB: hematogenous dissemination in immunocompromised
Tx: isoniazid + rifampin + pyrazinamide + ethambutol
Mycobacterium leprae
Mycobacterium, aerobe, acid fast stain +
Dz:
- Tuberculoid leprosy: hypopigmented and anesthetic skin plaques associated with enlarged peripheral nerves (few bacilli in granulomas)
- Lepromatous leprosy: symmetrical widespread skin nodules/plaques (many bacilli in foamy macrophages of granulomas)
Tx: dapsone + rifampin for tuberculoid, dapsone + rifampin + clofazimine in lepromatous
Chlamydia trachomatis
Obligate intracellular bacteria
Dz: trachoma (blindness), neonatal conjunctivitis/pneumonia, STD (urethritis, cervicitis, epididymitis, PID), lymphogranuloma venereum, Reiter’s syndrome
Tx: azithromycin (tetracycline for LGV)
Chlamydia psittaci
Obligate intracellular bacteria, Giemsa stain +, infection from aerosolized bird feces
Dz: psittacosis (atypical pneumonia)
Tx: doxycycline
Rickettsia rickettsii
Obligate intracellular rod, Giemsa stain +
Dz: Rocky Mountain Spotted Fever (maculopapular to petechial rashes spreading from wrists and ankles to trunk, involves palms and soles), encephalitis
Tx: doxycycline (alt: chloramphenicol or ciprofloxacin)
Mycoplasma pneumoniae
Extracellular atypical bacteria
Dz: Atpical pneumonia (patchy interstitial infiltrates with fever and nonproductive cough) which can be complicated by erathema multiforme, Raynaud’s, arthalgias, hemolytic anema, and Guillain Barre
Tx: macrolides (azithromycin) or tetracycline
Borrelia burgdorferi
Spirochete, Giemsa stain +, silver stain +
Dz: Lyme disease
- Stage 1: erythema chronicum migrans (bull’s eye rash)
- Stage 2: neuropathy (meningitis, polyneuritis) and cardiopathy (AV block)
- Stage 3: arthritis
Tx: doxycycline in early stages (amoxicillin for kids), ceftriaxone in late stages
Treponema pallidum
Spirochete, viewed in darkfield microscopy
Dz: syphilis
- Primary: chancre
- Secondary: widespread maculopapular rash involving palms and soles, condylomata lata, non-tender lymphadenopathy, meningitis, mucous patches
- Tertiary: granulomas, aortitis, neurosyphilis (paresis, tabes dorsalis, Argyll Robertson pupil)
Treatment: penicillin G or doxycycline
Malassezia furfur
Dimorphic spherical budding yeasts with short chain-like hyphae
Dz: tinea versicolor (hypo/hyperpigmentations with scales and itching)
Tx: miconazole or selenium sulfide (topical), itraconazole (oral)
Trichophyton rubrum/tonsurans/schoenlenii
Mold with filamentous septate hyphae
Dz: dermatophytoses (tinea capitis, tinea pedis, tinea corporis, tinea cruris, favus, onychomycosis)
Tx: miconazole (topical for pedis, corporis, cruris), griseofulvin (oral for capitis and onychomycosis)
Coccidioides immitis
Fungus, endemic to southwest US and Latin America
Dz: Valley fever (pneumonitis and erythema nodosum)
Tx: itraconazole or amphotericin B for disseminated infections
Histoplasma capsulatum
Fungus, from bird and bat droppings in the Mississippi and Ohio River Valleys
Dz: histoplasmosis (atypical pneumonia or disseminated infections in immunocompromised)
Tx: itraconazole or amphotericin B for disseminated infections
Blastomyces dermatitidis
Fungus, endemic to northeast US
Dz: blastomycosis (pulmonary infection that can spread to skin or bone forming ulcerated granulomas)
Tx: itraconazole or amphotericin B for disseminated infections
Candida albicans
Opportunistic fungus (yeast only)
Dz: candidiasis (thrush, vulvovagintitis, skin/nail infections (diaper rash), right sided endocarditis in IVDU, UTI in catheters)
Tx: nystatin (topical), fluconazole (vulvovaginitis), amphotericin B (systemic infections)
Cryptococcus neoformans
Opportunistic fungus (yeast only) from bird droppings, thick walled capsule on India Ink stain
Dz: meningitis (AIDS), pulmonary infections
Tx: amphotericin B + flucytosine for induction and fulconazole for maintenance
Aspergillus fumigatus
Opportunistic fungus (mold only with septate hyphae)
Dz: aspergillosis
- Allergic bronchopulmonary aspergillosis
- Fungus ball in preexisting TB cavities
Tx: amphotericin B, caspofungin, surgical removal of fungus ball
Mucor and Rhizopus
Opportunistic fungus (mold only) with irregular broad aseptate hyphae
Dz: mucormycosis (invasion leads to ischemic necrosis in sinuses and brain, as well as lungs and GI tract)
Tx: amphotericin B and surgical removal of necrotic tissue
Pneumocystis jiroveci
Opportunistic fungus, methenamine-silver stain +
Dz: pneumonia (diffuse bilateral interstitial infilatrates with ground-glass appearance)
Tx: TMP-SMX (also used for prophylaxis in CD4 < 200)
Plasmodium vivax/ovale/malariae/falciparum
Protozoa transmitted by mosquito bite
Dz: malaria (fever chills, sweats, hemolytic anemia, and hepatosplenomegaly), black water disease (P. falciparum - above plus cerebral malaria, lung edema, renal failure from hemoglobinuria, and death)
- P. malariae: endemic to Asia, Africa, and Latin America and targets mature RBC
- Tx: chloroquine
- P. vivax/ovale: endemic to Asia, Africa, and Latin America and targets reticulocytes and remains latent in hepatocytes
- Tx: chloroquine and primaquine (for dormant form)
- P. falciparum: endemic to SE Asia, E Africa, and South America and targets all age RBC
- Tx: mefloquine or quinine + doxycycline
Babesia microti
Protozoa (sporozoites, trophozoites, merozoites) trasmitted by Ixodes tick in NE US
Dz: babesiosis (fever, chills, hemolytic anemia, hepatosplenomegaly) - blood smear shows ring-like trophozoites or Maltese cross-like merozoites
Tx: **quinine + clindamycin **
Naegleria fowleri
Amoeba that invades nasal mucosa and eats brain in southwest US
Dz: primary amebic meningoencephalitis
Tx: amphotericin B + miconazole + rifampin or don’t put head underwater
Toxoplasma gondii
Protozoa from ingestion of undercooked meat or contact with cat feces
Dz:
- Congential toxoplasmosis: abortion, stillbirth, hepatosplenomegaly, or triad of intracranial calcification, hydrocephalus, and chorioretinitis
- Mononucleosis in immunocompetent
- Encephalitis, brain abscess, pneumonia, myocarditis in immunocompromised
Tx: sulfadiazine + pyrimetamine and avoid cats/raw meat if pregnant
Leishmania donovani (tropica/mexiana/braziliensis)
Intracellular parasite that infects bone marrow and spleen (transmitted by sandfly bite)
Dz:
- L. donovani: visceral leishmaniasis (fever, hepatosplenomegaly, skin hyperpigementation, and bone marrow suppression causing pancytopenia, infections, and bleeding)
- L. tropica/mexicana: cutaneous leishmaniasis (nodules and ulcers)
- L. braziliensis: mucocutaneous leishmaniasis (granulomatous ulcerating lesions)
Tx: sodium stibogluconate or amphotericin B
Trypanosoma cruzi
Flagellated trypomastigotes and nonflagellated amastigotes (reduviid bug bite)
Dz: Chagas’ disease (facial edema and nodules, chronic dilated cardiomyopathy, arrhythmias, megacolon, megaesophagus)
Tx: nifurtimox or benznidazole
Trypanosoma gambiense/rhodesiense
Flagellated trypomastigotes in blood/CSF without nonflagellated amastigotes in tissue
Dz: sleeping sickness (recurring fever, lymphadenopathy, encephalitis leading to coma and death)
Tx: suramin and melarsoprol for encephalitis
Entamoeba histolytica
Trophozoites and cysts
Dz:
- Amoebic dysentery: bloody diarrhea and abdominal pain
- Hepatic abscesses (anchovy sauce-like pus)
Tx: metronidazole
Giardia lamblia
Trophozoites and cysts
Dz: giardiasis (watery, fatty, foul-smelling diarrhea)
Tx: metronidazole and supportive care
Cryptosporidium parvum
Ingestion of oocysts (acid fast) which form sporozoites then trophozoites
Dz: cryptosporidiosis (watery diarrhea, worse in immunocompromised)
Tx: self-limited with normal immunity, paromomycin for immunocompromised
Trichomonas vaginalis
Trophozoites with no cysts transmitted by sexual contact
Dz: trichomoniasis (foul smelling, greenish vaginal discharge)
Tx: metronidazole
