Aerobic gram positive bacilli

Non-sporogenous gram positive bacilli

Corynebacterium, arcanobacterium, rhodococcus, lactobacillus, listeria, erysiplelothrix, gardnerella

Sporogenous gram positive bacilli

Bacillus

Partially acid fast gram positive bacilli

Nocarida, rhodococcus, gordona, tsukamurella

Non-acid fast gram positive bacilli

streptomyces

corynebacterium general characteristics

66 species (38 are clinically significant). majority are normal flora of skin and mucous membranes of humans and animals, closely related to mycobacteria and nocardia

corynebacterium diphtheriae general characteristics

incubation period of 2-5 days, pharyngitis or tonsillitis, exudate formed (pseudomembrane) on tonsils, cutaneous infections

Clinical manifestations of corynebacterium diphtheriae

Two forms (respiratory and cutaneous), pharyngitis or tonsilitis, pustule, chronic ulcer

Possible complications of corynebacterium diphtheriae

respiratory obstructions, systemic effects of diphtheria toxin absorbed: kidney, heart, and nervous system involvement, death often due to cardiac failure

natural habitat of corynebacterium diphtheriae

humans are only natural host, normal flora of skin and oral cavity

transmission of corynebacterium diphtheriae

droplet aerosols, hand to mouth contact

prevention of corynebacterium diphtheriae

vaccine, schick test

microscopic morphology of corynebacterium diphtheriae

gram positive, pleomorphic (chinese letter formation), club shaped, uneven staining, non-spore forming and non-motile

special media for corynebacterium diphtheriae

cysteine tellurite, loefflers, tinsdale, blood agar (looks like dirty staph, small zone of beta hemolysis)

Identification of corynebacterium diphtheriae

biochemical reactions, antibiotics resistance, toxin detection

diphtheria toxin

major virulence factor, produced by C diphtheriae, C. ulcerans, and c. pseudotuberculosis strains infected with a temperate bacteriophage carrying tox gene, only toxin producing strains can cause diptheria, blocks protein synthesis, nontoxic until exposed to trypsin

treatment of corynebacterium diphtheriae

antitoxin (diphtheroids, could cause serum sickness), antibiotics (penicillin, vancomycin), supportive (obstruction removal, respiratory regulation)

corynebacterium ulcerans

human infection usually acquired through animal contact, similar to C. diphtheriae but milder, lower levels of toxin production, mild pharyngitis

corynebacterium jeikeium

normal skin flora, nosocomial infections in immunocompromised, bacteremia associated with prosthetic devices, strict aerobe, highly resistant to antibiotics, treated with vancomycin

corynebacterium urealyticum

one of the most frequently isolated corynebacteria, primarily a urine pathogen, slow growing, strict aerobe, catalase positive, does not ferment glucose, rapidly urease positive, resists a variety of antimicrobials

corynebacterium xerosis

normal flora of skin and mucous membranes, opportunistic infections such as prosthetic valve endocarditis, disease more common in immunocompromised, grows on SBA and forms dry, pigmented yellow to tan colonies

corynebacterium straitum

normal flora of nasopharynx and skin, nosocomal infections have been reposted, a rare cause of infection

corynebacterium pseudodiphtheriticum

normal flora of nasopharynx, rarely causes infections, associated with endocarditis, respiratory, UTIs, and cutaneous wound infection in immunocompromised, does not demonstrate characteristic pleomorphic morphology, stains evenly and cells often link in parallel rows, grows well on standard lab media

toxin detection

diagnosis of diphtheria depends on demonstrating that the isolate produces diphtheria toxin, ELISA, PCR to detect tox gene, Elek test

Arcanobacterium species

A. haemolyticum, A. pyogenes, A. bernardiae, all are catalase negative

A. haemolyticum

recovered from 10-20 year old patients with pharyngitis, a pruritic rash and desquamation of the skin from hands and feet, produces small colonies and narrow zone of beta hemolysis on SBA, lipase and lecithinase positive, resistant to penicillin

Rothia

does not ferment carbohydrates, shows variable reactions to a number of biochemical tests

rothia equi

found in soil, causes respiratory tract infections in animals, human infection rare

rothia equi microscopic morphology

may demonstrate branching filaments, may be partially acid fast

rothia equi macroscopic morphology

resembles klebsiella, forms salmon pink pigment with prolonged incubation

listeria monocytogenes general characteristics

gram positive bacilli, pleomorphic coccobacilli, beta hemolysis on BAP, catalase positive, tumbling motility, umbrella motility in agar

listeria monocytogenes virulence factors

hemolysin(listerolysin O, damages the phagosome membrane to prevent killing of the organism by the macrophage), catalase, superoxide dismutase, phospholipase C, surface protein p60 (induces phagocytosis through increased adhesion and penetration into mammalian cells

early onset neonate listeria monocytogenes infection

in utero or during birth, results from an intrauterine infection that causes illness at or shortly after birth, most often results in sepsis, may be associated with aspiration of amniotic fluid

late onset neonate listeria monocytogenes infection

several days to weeks after birth, most often results in meningitis

listeria monocytogenes infection in pregnant women

more common in third trimester, listeriosis may present as flu like illness with fever, headache, and myalgia, organism enters bloodstream and seeds the uterus and fetus, causes premature labor or septic abortion in 3-7 days

listeria monocytogenes infection in immunocompromised patients

invasive listeriosis most commonly occurs in patients receiving chemotherapy, young children and older adults ae at risk, CNS and endocarditis are the most common clinical manifestations

natural habitat of listeria monocytogenes

zoonotic (mammals, birds, fish, insects), soil, water, vegetation

Transmission of listeria monocytogenes

ingestion of contaminated foods (milk, soft cheese, meat, cabbage, cold cuts, hot dogs), contact with environment, vertical

prevention and control of listeria monocytogenes

very difficult if not impossible, able to grow within a wide temperature range, avoid soft cheeses, cold cuts, or hot dogs when pregnant, ingest only pasteurized milk or cheese

diagnosis of listeria monocytogenes

direct smears (cells found singly in short chains or in palisades), may be preceded by cold enrichment if specimen is contaminated, slight zone of beta hemolysis, must be differentiated from strep and diphtheroids, unique motility (umbrella and tumbling), positive catalase, hippurate hydrolysis, bile esculin hydrolysis, VP and methyl red, and camp

Erysipelothrix rhusiopathiae general characteristics

gram positive, non-spore forming, slender filamentous bacilli, pleomorphic, facultative - microaerophilic, 2-3 days to grow, alpha hemolytic

diseases caused by Erysipelothrix rhusiopathiae

enodcarditis, erysipeloid, septicemia

natural habitat of Erysipelothrix rhusiopathiae

ubiquitious, zoonotic (pigs (main), mammals, birds, fish), soil

transmission of Erysipelothrix rhusiopathiae

direct contact, trauma or puncture to skin, occupational disease

diagnosis of Erysipelothrix rhusiopathiae

gram positive, filamentous rods, will grow on most conventional media (BAP is most commonly used). grow best under microaerophilic conditions

identification of Erysipelothrix rhusiopathiae

alpha hemolytic on SBA, nonmotile, catalase negative, hydrogen sulfide production on TSIA, VP negative, gelatin stab culture yields a test tube brush like pattern at 22 degrees C

treatment of Erysipelothrix rhusiopathiae

penicillin, cephalosporins, eryhromycin, clindamycin

lactobacillus acidophilus general characteristics

aerobic (or facultative anaerobe), gram positive, highly pleomorphic, non-spore forming, non-motile, optimal growth at pH 6

lactobacillus acidophilus epidemiology

normal flora in the mouth, gastrointestinal tract, female genital tract, a common contamination of urine specimens

beneficial properties of lactobacillus acidophilus

protects females from urogenital infections, produce lactic acid which lowers vaginal pH and suppresses overgrowth of bacteria, aids in digestion, diarrhea may occur if eliminated, can be replenished by eating yogurt

lactobacillus acidophilus colony morphology

pinpoint colonies, alpha hemolytic, frequently isolated from vaginal/cervical specimens and urines

identification of lactobacillus acidophilus

not commonly identified since it is usually a normal flora contaminant, catalase negative

treatment of lactobacillus acidophilus

penicillin in combination with an aminoglycoside

gardnerella vaginalis general characteristics

small, pelomorphic gram variable (positive but could look negative), coccobacilli and short rods, produces small, gray colonies, does not grow well on commercial blood agar, diffuse zone of beta hemolysis on human blood bilayer tween agar

gardnerella vaginalis epidemiology

normal flora in vaginal tract. may colonize distal urethra of males, transmission id unknown, possibly caused by endogenous strains

infections caused by gardnerella vaginalis

bacterial vaginosis, UTIs, bacteremia (rare)

diagnosis of gardnerella vaginalis

gram stain of vaginal secretions, wet mount of vaginal secretions (clue cells)

clue cells in gardnerella vaginalis

large, squamous epithelial cells with numerous small rods attached, large amount of gram positive rods with little presence of lactobacillus is indicative of it

Bacillus spp. general characteristics

aerobic, gram positive, bacilli, form endospores, more than 50 species found in environment

bacillus anthracis

most highly virulent, causative agent of anthrax, highly lethal, not highly contagious

transmission of bacillus anthracis

contact with infected animals or products, inhalation of spores, introduction of spores through breaks in skin or mucous membranes, ingestion (rare)

virulence factors of bacillus anthracis

glutamic acid capsules (protects organism from phagocytosis), protective antigen, edema factor (an ademylate cyclase that increases camp in host cells), lethal factor (protease that kills host cells)

exotoxins of bacillus anthracis

all three proteins act synergistically, PA is binding molecule for EF and LF, PA and EF causes edema, PA and LF causes death

cutaneous anthrax

site of spore entry, 2-3 days incubation, progressive stages

progressive stages of cutaneous anthrax

small, pimple, erythematous rings, ulceration, black scar (eschar), eschar heals after 1-2 weeks, lesion dries and falls off, usually localized but can rarely become systemic

pulmonary anthrax

wool sorters disease, inhalation of spores, malaise with mild fever and fatigue for 2-5 days after spore exposure, initial flu like symptoms last 2-3 days, progresses to a severe phase (respiratory distress, chest edema, cyanosis, coma, death)

gastrointestinal anthrax

accounts for less than 1% of total anthrax cases worldwide, ingestion of spores, oropharyngeal or abdominal infection, abdominal pain, nausea, vomiting, due to difficulty with diagnosis fatality may be higher than cutaneous anthrax

complications of anthrax

5% of all cases develop meningitis, recovery from infection seems to confer immunity, effective vaccines are available for at risk individuals (occupational exposure)

microscopic morphology of bacillus anthracis

large, square ended gram positive rod, found singly or in chains, clear zones around cells representing the capsule, subculturing bacteria will lead to inability to produce capsule, older cultures can appear as gram variable

bacillus anthracis colony appearance

medium large, non-hemolytic, gray, flat, irregular margin, swirling projections (medusa head appearance), when edges of colony lifted with loop they will stand upright (similar to beaten egg whites)

identification of bacillus anthracis

catalase positive, can grow under aerobic and anaerobic environments, non motile (differentiates from other bacillus sp.), can grow in high salt (7% NaCl) and low pH, susceptible to penicillin

bacillus subtilis

rarely causes human infection, vegetative cells and spores widely distributed in nature, not part of normal flora, may be pigmented, identified biochemically

bacillus cereus

common cause of food poisoning and opportunistic infections, similar morphology and metabolically to B. anthracis, infections of the eye is the most common non GI infections, rarely causes serious infections, but do occur in IVDU, immunocompromised, neonates, and post surgical patients

bacillus cereus opportunistic infections

post traumatic eye infection, endocarditis, bacteremia, more common in IV drug users than immunocompromised

diarrheal type of food poisoning

associated with ingestion of meat and poultry, incubation period is 8-16 hours, abdominal pain, diarrhea, vomiting, average duration is 24 hours

emetic type of food poisoning

abdominal cramps and vomiting, some also have diarrhea, associated with ingestion of fried rice, average duration is 9 hours

virulence factors of bacillus cereus

enterotoxin production, lecithinase production (egg yolk agar, zone of opacity around colonies due to breakdown of lecithin found in egg yolks)

colony morphology of bacillus cereus

large, feathery, spreading, beta hemolytic

differentiation tests bacillus sp

hemolysis on SBA(antrhacis non hemolytic, cereus hemolytic), penicillin sensitivity (anthracis susceptible, cereus is resistant), motility (anthracis is non motile, cereus is motile)

generally characteristics of aerobic actinomycetes

similar morphology to fungi, demonstrate branching filamentous hyphae in culture, non spore forming, not commonly seen, responsible for significant human disease

clinically relevant actnomycetes

nocardia, actinomadura, gordonia, steptomyces, tsukamurella

clinically relevant Nocardia

N. asteroides, N. nova, N. farcinia, N. brasiliensis, N. otitidiscariarum

general characteristics of nocardia

aerobic, gram positive, rods, form branching hyphae, will stain gram variable, weakly acid fast, grow well on standard media, growth takes one or more weeks, commonly found in soil, infections more common in inmmunocompromised patients

virulence factors of nocardia

largely unclear, superoxide dismutase and catalase (resistance to intracellular killing)

pulmonary infections of nocardia

inhalation of organisms present in dust or soil, majority caused by N. asteroides, confluent bronchopneumonia that is usually chronic, progresses within months, extensive tissue involvement and damage, may disseminate to other organs, no sulfur granules or sinus tracts

cutaneous infections of nocardia

inoculation of organism into skin or subcutaneous tissues, N. brasiliensis most commonly involved, usually seen in hands and feet, infection begins as localized abscess, invasive and destructive to tissues and bone, lesions called mycetomas

nocardia microscopic morphology

gram reaction may be weak or irregular causing a beading appearance, usual specimens ae sputum and exudates or aspirates from skin or abscesses, acid fast when a weak acid is used

culture characteristics of nocardia

grows on routine bacterial media, grow better with increased CO2, chalky white to yellow or brown folded, grows slowly (3-30 days)

actinomadura, gordonia, streptomyces and tsukamurella general features

similar to nocardia, gram positive, aerobic, some are catalase positive, branching (can fragment into rods and cocci), differentiation is difficult