Chapter 8-01: Microbiology in Infectious Diseases

Bacteria

Gram-positive:

    Cocci

Streptococcus spp., Staphylococcus spp.

    Rods

Bacillus spp., Clostridium spp., Listeria spp.

Gram-negative:

    Cocci

Neisseria spp.

    Rods

Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Hemophilus spp.

Mycobacterium

Mycobacterium tuberculosis

Spirochetes

Treponema pallidum (Syphilis), Borrelia spp., Leptospira spp.

No cell wall

Mycoplasma spp.

Viruses

DNA viruses

RNA viruses

Parvovirus, Papillomavirus (HPV), Adenovirus, Herpesvirus, Hepadnavirus (Hepatitis B)

Picornavirus, Hepesvirus (Hepatitis E), Calicivirus (norovirus), Retrovirus (HIV), Orthomyxovirus (influenza), Coronavirus

Fungi

Yeasts

Dimorphics

Molds

Candida spp., Cryptococcus spp.

Coccidioides spp., Histoplasma spp., Blastomyces spp., Paracoccidioides spp.

Aspergillus spp., Mucor spp., Rhizopus spp.

Parasites

GI infections

CNS infections

Hematologic infections

Sexually transmitted diseases

Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum

Toxoplasma gondii, Naegleria fowleri

Plasmodium spp., Babesia spp.

Trichomonas vaginalis

Helminths

Nematodes (roundworms)

Cestodes (tapeworms)

Trematodes (flukes)

Enterobius vermicularis, Strongyloides stercoralis, Toxocara canis

Taenia solium, Echinococcus granulosus

Schistosoma spp., Clonorchis sinensis

Cocci

Staphylococcus aureus

• Skin/soft tissue infections, septic arthritis, osteomyelitis, pneumonia, endocarditis, meningitis

• Toxin-mediated: Toxic shock syndrome, scalded skin syndrome, food poisoning

• Can be methicillin sensitive (MSSA) or methicillin resistant (MRSA). Culture and determine sensitivities. Cover for MRSA empirically up-front with IV vancomycin in hospitalized patients.

Staphylococcus epidermidis

• Skin flora – can be a contaminant in culture or can be a true pathogen

Streptococcus pneumoniae

• Meningitis, pneumonia, sinusitis, otitis media

Streptococcus pyogenes (Group A strep)

• Skin/soft tissue infection, pharyngitis

• Toxin-mediated: Toxic shock syndrome, scarlet fever, necrotizing fasciitis

• Immune-mediated: Rheumatic fever, post-strep glomerulonephritis

Streptococcus agalactiae (Group B strep)

• Meningitis, pneumonia, sepsis in babies

Streptococcus bovis

• GI flora that can penetrate into the bloodstream and cause subacute bacterial endocarditis in the setting of colon cancer or IBD

Enterococcus spp.

• UTI, biliary infection, subacute bacterial endocarditis

• Infections associated with indwelling lines and catheters

• Enterococcus faecium is often vancomycin resistant (VRE)

Rods

Spore-forming, aerobic

Bacillus cereus

• Pre-formed toxin that contaminates rice, causes diarrhea

Bacillus anthracis

• Black painless ulcer, flu-like, lethal

Spore-forming, anerobic

Clostridium tetani

• Wound gets infected, bacteria travels up neuron, can lead to spastic paralysis, trismus (lockjaw), risus sardonicus (spasm of facial muscles, appears like a grin)

Clostridium botulinum

• Preformed toxin in canned food, leads to flaccid paralysis

Clostridium perfringens

• Wound gets infected, can lead to muscle necrosis. Can also get food-borne disease that causes watery diarrhea

Clostridium difficile

• Common nosocomial infection, but can also be acquired in the community

• Watery diarrhea or, in severe cases, toxic megacolon

Nonfilamentous non-spore forming