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Gram Positive Organisms

 I. Gram Positive Cocci

Positive Catalase                                                                                                 Negative Catalase

               1. Staphylococcus                                                                                                                             

               2. Micrococcus                                                      Streptococcus                                                                                                     Peptostrepto/Enterococcus

               Facultative Anaerobe            Strict Aerobe            Pyogenic                            Pneumo-coccus                 Viridans/others       


1. S. aureus

+ Coagulase

+ Mannitol salt

Scaled skin synd.

Toxic Shock synd.

Food poisoning

Dx: Disc sensitivity

2. S. epidermis

- Coagulase

- Mannitol salt agar

Nocosomial prosthetic infection

3. S. saprophyticus

- Coagulase

- Mannitol salt agar




NF skin

Free living






1. Group A

b - hemolytic

S. pyogenes

NF skin


Cellulitis, AGN

Rheumatic fever

Scarlet fever

2. Group B

S. agalactiae

Neonatal sepsis


3. Non A&B

S. bovis

R/T Colon CA

S. pneumonia

Lancet shaped

Diplococcus  (in host; strepto-coccus in medium)

a - hemolytic

+ Bile soluble

+ Quellung reaction

Predisposing factor: Etoh, DM, renal dz, AIDS

False + serology d/t similar Ab w/ Klebsiella and H.pneumo.

1. Viridans

a - hemolytic

- Bile soluble

S. mutans

Dental caries,

Most common endocarditis post dental surgery


2. Others

a. Non-hemolytic

b. Micro –aerophilic

Never pathogenic

1. Pepto - streptococcus


Normal colony in mouth, colon


2. Entero-coccus

Group D


b - hemolytic

Grow on bile

E. faecalis

Nocosomial UTI


II. Gram Positive Rods

                   Spore & Exotoxin Producing                                                                Non-Spore Producing






1. B. anthracis

** Bamboo rods

Medusa colony; Elliptical central spore; Saprophyte; Capsule;

Exotoxin -> Anthrax - 3 forms: Cutaneous, GI, Respiratory (Woolsorter’s dz)

2. B. Cereus

Motile; No capsule

Food poisoning d/t toxins - sx after 12 hrs


1. C. perfringens

Capsule; Food poisoning  - 8 to 24 hrs after consumption of stews and gravies. Gas gangrene

2. C. tetani

** Tennis racket w/ terminal spores; Motile; Tetanus

 Lockjaw, muscle spasm

3. C. botulinum

Subterminal spore, Contaminated canned food -> paralysis; Infant (honey). Neurotoxin- destroyed by heat, virus induced

4. C. difficile

Abx assoc. pseudo-membranous colitis

1. Actinomyces israelii

Microaerophilic/ Obligate anaerobe

NL oral cavity

Invade tissue post trauma eg. Tooth extraction

Sulfur granules

2. Nocardia asteroides

Strict Aerobic

Acid fast

Pulmonary infection from soil

1. Corynebacterium diphtheriae

+ Tellurite agar, + Catalase; Twisted rods; + Exotoxin due to lysogenic bacteriophage; Diphtheria

Sx: **  pseudomembranous pharynx, Bullneck

2. Listeria monocytogenes

b-hemolytic, + Catalase

Motile, pseudopod; In unpasteurized milk; Listeriosis - Grow in non-immune macrophage

3. Erysipelothrix

In decaying matter; Causes erysipeloid (erythematous skin); Traumatic inoculation esp. in butcher/fisherman

Gram Negative Organisms



No Cell Wall

Neisseria - Diplococci

+ Capsule and Fimbriae

+ Oxidase; Fastidius (Grows with CO2 and blood); Facult anaerobe

1. N. meningitidis

IgA protease; Get into bld stream and enter meninges. Nasal carriers. Fimbriae.

Dx: Spinal tap, CO2 enriched BAP

2. N. gonorrhea

Chocolate agar w/ CO2

Dx: Male – 2-7 days purulent urethral d/c with dysuria. Female- asx (smaller urethra).

Enzyme- sugar ferment.

Thayer-Martin agar (has Abx).

Medicolegal. Other Neisseria (not grow on T-M agar).

1. Strict Aerobic

Pseudomona aeruginosa


** Water soluble greenish pigment

Common in burns, cystic fibrosis

2. Strict Anaerobic


3. Others

(See below)

1. Mycoplasma

 - Urease; No cell wall (Gm – d/t CM); Smallest cell; Pleomorphic

Sterol in CM. Older name = PPLO.

M. pneumoniae

Fried egg colonies

Mycoplasma agar

Serology – Fluorescent Ab

M. hominis

Post abortion and post partum infection; from own genital NF

2. Ureaplasma

No cell wall (Gm – d/t CM)

Smallest cell; Sterol in CM;

+ Urease; Non-gon,non-chlam urethritis

                                               Others - Straight                                                           Others - Curved





1. Haemophilus

H. influenzae


Complex lab media of hematin (Factor X) and NAD (Factor V)

Resp. transmission

[[H. ducreyi (Chancre)

Painful, soft, ulcerating chancroid; Buboes, Satellite lesions

H. aegyptius


2. Bordetella pertussis

Coccobacilli, + Fimbriae (Not virulent w/o it)

Droplet infxn;

Whooping cough; Stages: Catarrhal, non-productive paroxysmal cough, convalescence

3. Legionella pneumophilia

+ Silver impregnation stain (Gm St not good)

Fastidius (Requires L-cysteine and FE3+)

Colonies “ground grass”

Parasite of protozoa

Necrotizing multifocal PNA, multiplies w/in monocyte-macrophage

Fluorescent Ab Test

1. Yersinia pestis

Gm - bipolar

Bubonic plague

vector = flea

Fever, buboes – up to 70% mortality w/o tx

Primary PNA = plague

Do Gram stain of buboe

2. Brucella

Undulant fever

(24hr nl then fever then normal; peaks in the evening)

Enriched medium

B. abortus = cow

B. melitensis = goat

Transmitted by unpasteurized milk

Dx: Serology

3. Francisella tularensis


Bite of vector (tick or deer fly)


** Infects reticular endothelial organs


4. Pasteurella multocida


Cellulitis due to cat/dog scratch/bite

Dx: Culture on BAP

All ferment glucose, reduce nitrate, Oxidase negative

1. Escherichia coli

EMB agar; Most common cause of UTI

2. Shigella

S. Sonnei - Shigellosis; Dysentery;

3. Salmonella typhi

Stool - EMB and deoxycholate; + H2S

Typhoid fever; Salmonellosis x typhoid. In chicken containing food.

4. Yersinia pestis

Bipolar staining (more concentrated at the ends).

Plague, Vector = flea (bite)

5. Serratia

Inducible enzyme. Opportunist.

6. Citrobacter

Citrate as sole source of nutrient. Opportunist.

7. Klebsiella pneumoniae

Now just respiratory infxn. Current jelly sputum.

8. Enterobacter

Peritrichous flagella. Opportunist.

9. Proteus, Providencia, Morganella

In AIDS pt only

1. Vibrios cholerae

Polar flagella


Fecal contamination

** Rice water stool

2. Campylobacter

Polar flagella

C. jejuni and C. enteritis


C. fetus

Abortion in animal, Sepsis in human

3. Helicobacter pylori

Peptic ulcer and gastritis

+ Urease- NH4 OH act as buffer



III. Non Gram Staining Organisms

A. Spirochetes

Axial rod through spiral - (spirillum w/o axial rod) Dx: Dark Field or E.M.




1. Treponema pallidum (Syphillis)

Grows in special tissue cx only

Sexual contact, drug abuser

Neonatal syphilis – Hutchinson’s teeth;

3 Stages:

1° = hard painless chancre, asx for 2-10 wks afterwards

2° = highly infections, small pinpoint lesions

3° = > 5 ys later, efferent motor damage

Dx: silver impregnation stain

Medico legal

2. T. pertenue ( Yaws)

Not STD, mainly in children; Scars form develop at site of 2° infection. Contact, fomite, insect; In tropics

3. T. carateum (Pinta)

Not STD, palms, “pinta” = “painting” - areas of de/hyper – pigmented skin

4. Treponema. pallidum (Bejel)

Not STD, Maybe a race

More purulent d/c than syphilis


1. Borrelia recurrentis

 (Relapsing fever)

Spirochete c irregular spirals

Reservoir host – rodents and mammal;

Vector – endemic (tick); epidemic (lice)

Fever recurs weekly

Giemsa or Wright stain

2.Borrelia burgdorferi (Lyme dz)

Giemsa or Wright stain

Vector = tick;

Reservoir = deer and mice; Dx: serology; 3 stages:

1). erythema chronicum migrans, painless rash (target bullseye).

2). Cardiac and neuro sx months later.

3) arthritis in large joints and progressive CNS dz


Closely wound spirals, Hooked ends

1. Leptospiral interrogans

Spread by urine of dogs, mice, rats

Dx: DF, immunofluor, silver stain

Flu like sx

Weil’s dz – most severe form of leptospirosis (jaundice and renal damage); usually have to concentrate bld or CSF, high titer of Ab

B. Acid fast rods, Chlamydia, and Rickettsia

Acid Fast Rods



A. Mycobacterium


Slow growing

Stain: Carbolfuschins, acid alcohol, methylene blue

1. M. tuberculosis (Tuberculosis)

Droplet infection or unpasteurized milk

Focus of infection – Lungs (Exotoxin) PPD skin test (protein ppt derived test)

If + test – do CXR and sputum cx

AIDS pt – M. kansasii and M. avium

2. M. leprae (Leprosy)

Grow on foot pads of mice and armadillos;

New cases from prolonged contact with infected

Trans: nasal mucosa, skin lesions, insects

Granulomatous dz of PNS and nasal mucosa. Brown rash becomes necrotic, infects cartilage and bone.

Dx: Acid fast stain


B. Nocardia – see Gm Pos Rods

Intracellular parasite

Reproduce via endocytosis/ multiplication (elementary body® reticular body)

1. C. psittaci (Psittacosis)

vector = bird, Resp inhalation

TWAR strain – does not need bird vector

2. C. pneumoniae (Walking PNA)

Droplet transmission, Nosocomial infection

3. C. trachomatis

a. Trachoma = Chronic conjunctivitis (Strain A,B,C)

Contact or fomite

b. Non-gonococcal urethritis

(Str D®K) leading cause of STD, male – purulent d/c, dysuria, med-legal

c. Inclusion conjunctivitis

(Str D®K), In newborns d/t mother w/ NGU

d. Lymphogranuloma venerum (LGV)

(Str L1-3) Buboes

Gram neg coccobacilli

Obligate intercellular parasite

** Binary fission, longer generation time, arthropod vector (dif w/ Chlamydia)

1. Rickettsia Rickettsii

(Rocky Mnt Spotted fever)

vector = tick; Res host = rabbit, man, tick

2. R. akari (Rickettsialpox)

vector = mite; Res host = mouse

Burning, necrotic lesion

3. R. prowazekii (Epidemic typhus)

vector = louse; Res host = animal

Scratch MO into skin after louse bite, defecate and vomit

4. R. tsutsugamushi (Scrub typhus/fever)

vector = mite; Res host = mouse


5. R. typhi (Endemic/ Murine typhus)

vector = flea; Res host = mouse

6. Rochilmea Quintana (Trench fever)

vector = lice; Res host = animal

Roseolar rash

7. Coxiella burnetii  (Q fever)

vector = tick; Res host = cow

** Human obtain by inhalation of dry feces

8. Ehrlichia Canis  (Ehrlichosis)

vector = tick; Res host = dog

** Prefers WBC


                      I. DIMORPHIC  

1. North American Blastomycosis

(Gilcrist’s Disease)

(Blastomyces dermatitidis).

Suppurative and granulomatous skin lesions esp. in skin, lungs, bones. ** One blastospore.  2 Types- 1). Cutaneous: skin- purulent, Lesions- elevated edges. 2). Systemic:  Resp tract- disseminated via blood to tissues and bones.


2. South American Blastomycosis (Paracoccidioides)

(Blastomyces brasiliensis or Paracoccidioides brasiliensis)

Chronic granulomatous disease of skin, mucous membrane, LN, organs. Saprophyte. Require warm temp.  POE= Mouth. **Large LN. ** Many blastospores. 4 Types: Cutaneous (mucosal), Lymphatic, Visceral, Mixed-type.

3. Coccidioidomycosis

(Valley Fever, San Joaqhin Fever). (Coccidioides immitis)

Yeast- spherule with endospore. Barrel-shaped arthrospore. Most infectious of the system mycoses. Need blood. FOI= Lungs. Pigeon feces. In Southwest.


4. Histoplasmosis

(Histoplasma capsulatum)

Spikelike tuberculate macroconidia. Pigeon feces, infected bat guano. Central/Eastern US. Reticuloendothelial system. Grow within macrophage.

3 Types: 1). Primary- lungs calcification in parenchyma. 2). Progressive- Emaciation, leukopenia. 3). Disseminating- Febrile and enlargement of reticulo-endothelial organ eg. Spleen, liver. Serological- need titer 1:32 or higher.

5. Tinea Versicolor

(Malassezia furfur)

Superficial skin. *Hypo-pigmented areas. More frequent in hot humid weather. Lesions contain both budding yeast cells and hyphae. Obtained by trauma. Dx- KOH prep.


6. Sporotrichosis

(Sporotrichum schenckii)

Traumatic inoculation. Hyphae- 3 to 5 macroconidia in clusters. Nodular lesion that forms indolent (hard) ulcers (lymphatic pustule) in LN, skin, or subcutaneous tissues. Saprophyte. Pyogenic infection spread along lymph system to bones, eyes, CNS.



Yeast Only

Mold Only



1. Cryptococcosis

(Cryptococcus neoformans)

The most common life-threatening fungal disease in AIDS pts. Immuno-compromised. **Yeast with large capsule. Bird feces with soil. Infects esp. brain and meninges.


2. Candidiasis

(Candida albican)

NF. Opportunist (esp. in DM- overgrowth d/t high sugar = thrush in mouth). Moist skin. Yeast and **pseudohyphae (chains of blastospores that do not break off, look like hyphae). **Grows on Corn meal agar (poor nutrition for other fungus). 4 types:  Mucous membrane= Thrush, Cutaneous (vaginal, baby), Pulmonary, CNS.

1. Dermatomycosis

Grows on derma (skin, hair, nail). The only communicable fungal infection. 3 Genera: 1). Microsporum (leaf shaped). 2). Trichophyton (macroconidia- bat shaped). 3). Epidermophyton (Pingpong paddle shape). Dermal infection (keratin). Tinea = Tinea pedis (feet), unguium (nail), cruris (jock-itch), corporis (trunk), barbae (beard), capitis (ringworm on scalp), imbricata (scales), favosa (honey-comb).


2. Tinea Nigra (Cladosporium werneckii)

An infection of the keratinized layers of the skin. Pleomorphic.  Brown to black macules on palmar aspect of the hands (due to melanin-like pigment in the hyphae).


3. Maduromycosis

(Madura foot, Mycetoma)

**Clubbed shaped foot. (2X-3X normal size). Caused by variety of filamentous fungi. Exogenous source, d/t trauma. Occurs in the tropics and subtropics. Human pathogen that reproduce sexually.


4. Geotrichosis

(Geotrichum species)

Infection is endogenous from mouth and intestine. Also exogenous (soil). Immunocompromised pt. Geotrichum candidum -  seg-mentation of hyphae into arthrospores (brick-shaped).


5. Aspergillus

(Aspergillus species)

May cause allergy. Opportunist. Inhaled spores. Separate hyphae. Colonizing tuberculous cavity in lung. Cause PNA.

6. Mucormycosis (Mucor species)

Rapidly fatal. Acute inflammation and vascular thrombosis. Cause= hyphae invade walls and lumen of blood vessels. **DM. Pulmonary mucormycosis in DM- fatal (2-10days duration). Source= soil, manure, fruit, bread mold. Ulcerative colitis in non-DM with peritonitis, death.


7. Rhizopus

Saprophytic. ** Esp in DM, burns, leukemia. Airborne asexual spores. Proliferates in walls of bld vessels esp. paranasal sinus, lungs, gut. Cause necrosis distally. Nonseptate hyphae broad, branches form right angles.


8. Pseudallescheria

(Pseudallescheria boydii). Separated hyphae resemble Aspergillus. ** Conidia (pear-shaped) with brownish-gray mycelium.


9. Rhinosporidiosis

(Rhinosporidium seeberi)

Infect mucous membrane of nose, eyes, ears, larynx, vagina, penis. Polyps. Cause= Swimming in stagnant water. Sx= painless itching with mucoid discharge. Develops into tumors. Sporangiospore mold.


10. Chromoblastomyces or Verrucous dermatitis.

Caused by a wide variety of fungi. Warty cutaneous nodules. Infection by trauma. Simulates a patch of ringworm.

1. Actinomycosis

(Actinomyces israelii)

Procaryotic Gram +.  Chronic suppurative and granulomatous lesions. **Sulfur granules on skin. Anaerobic. Endogenous- NF of mouth. Enter via trauma. Lumpy jaw. 3 Types: Cervicofacial, thoracic, abdominal.


2. Nocardiosis

(Nocardia species)

**Strict Aerobic. Some acid fast. Exogenous disease- soil. Suppurative and granulomatous subcutaneous dz with swelling, abscess. 3 types: 1). Mycetoma (unilateral infection of extremity), 2). Pulmonary infection (N. asteroides). 3). Systemic


3. Pneumocystis

(Pneumocystis carinii)

PNA in AIDS. Analysis of rRNA, mtDNA, enzyme= fungus. But not grow on fungal media and antifungals are ineffective. But, controlled by antiprotozoan. Has cystic forms and sporozoites. Transmission by inhalation, but not invade lung tissue. Cyst in alveoli cause frothy exudate that blocks gas exchange.

For the Medical School and Chiropractic Students of America by Scott D. Neff, DC DABCO MSOM MPS-BT DE IDE IME CFE DABFE FFABS FFAAJTS 2010 graduate Antigua School of Medicine, West Indies


© & TM 1998 American Academy for Justice Through Science. All rights reserved.

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