MICROBIOLOGY I Laurie Baeker Hovde B S MT ASCP 1 GRAM STAIN Gram stain result provides the first clue quick easy diagnostic tool can guide empiric therapy divides bacteria into two groups positive blue or purple negative red or pink determines cell morphology i e shape size and arrangement 2 OXYGEN REQUIREMENTS anaerobic intolerant of O2 require proper handling and special conditions for growth specific request required for I D aerobic utilizes O2 and grows well in an atmosphere of room air facultatively anaerobic will grow aerobically or anaerobically and includes most clinically significant aerobes 3 1 Gram positive 4 Gram positive cocci round or spherical shape anaerobic Peptostreptococcus species part of indigenous or normal flora opportunistic pathogens will only cause infection if the integrity or immunity of the host is compromised 6 2 Gram positive cocci aerobic catalase test H2O2 H2 O2 positive Staphylococcus seen as groups or clusters on Gram stained smear normal flora of surface epithelium 7 Gram positive coagulase test an enzyme that binds fibrinogen positive S aureus a virulent pathogen skin infections pneumonia osteomyelitis food poisoning toxic shock syndrome MRSA 50 nationwide VISA VRSA negative SCN S epidermidis SBE S saprophyticus UTI 8 Gram positive cocci aerobic catalase test H2O2 H2 O2 negative Streptococcus seen scattered in pairs and as chains on Gram stained smear hemolytic properties on blood agar beta alpha gamma 9 3 Gram positive 10 Gram positive 11 Gram positive cocci aerobic gamma or alpha hemolytic bile esculin test esculin hydrolysis in the presence of bile positive Strep group D 12 4 Gram positive Strep group D growth in 6 5 NaCl PYR test to see if the organism has the enzyme that hydrolyzes the PYR substrate positive Enterococcus E faecalis 80 90 E faecium UTIs wound infections intraabdominal abcesses nosocomial infections VRE 1988 13 Gram positive Strep group D growth in 6 5 NaCl PYR test negative Strep group D not Enterococcus S bovis main human pathogen in this group 14 Gram positive cocci aerobic beta hemolytic PYR test positive Strep Group A S pyogenes pharyngitis scarlet fever skin and soft tissue infections the flesh eating strep autoimmune sequelae glomerulonephritis rheumatic fever 15 5 Gram positive PYR test negative other b hemolytic strep CAMP test synergism between Group B Strep and S aureus produces an enhanced arrow shaped zone of hemolysis at the intersection OR Hippurate hydrolysis a positive test results in a colored end product after addition of ninhydrin reagent 16 Gram positive CAMP test Hippurate hydrolysis positive Strep Group B GBS or S agalactiae most common cause of neonatal sepsis and meningitis amnionitis endometritis in pg women blood skin soft tissue infection pneumonia can be carried asymptomatically 17 Gram positive CAMP test and Hippurate hydrolysis negative Strep Group C F G S milleri Commercial latex agglutination tests classifies beta hemolytic Streptococcus into Lancefield groups in 1 hour S milleri and Strep Group F urogenital tract infections abscesses Strep Group C an G pharyngitis postpartum sepsis rash bacteremia 18 6 Gram positive cocci aerobic alpha hemolytic Optochin test disk susceptibility test Bile solubility test positive colonies autocatalyze or dissolve in the presence of bile salts 19 Gram positive Optochin test and Bile solubility test sensitive soluble S pneumoniae pneumococci seen as lancet shaped pairs on Gram stain community acquired pneumonia otitis media sinusitis meningitis primarily in children 5 years old 45 are Penicillin I or R in U S TM vaccine 2000 Prevnar 20 Gram positive Optochin test and Bile solubility test resistant insoluble S viridans a miscellaneous group of Strep that are part of the normal flora of oral respiratory and GI mucosa opportunistic pathogen low virulence major etiological agent of endocarditis in the U S 21 7 Gram positive bacilli rectangular shape anaerobic Clostridium species spore formers found in soil water dust sewage and in the intestinal tracts of animals and humans produce nasty toxins that are often responsible for the symptoms 22 Gram positive C difficile antibiotic associated diarrhea and pseudomembraneous colitis most common agents are beta lactams and clindamycin nosocomial infection carried asymptomatically as part of GI flora in up to 50 of kids 1 year old tissue culture gold standard also EIA latex agglutination chromatographic assay 23 Gram positive C perfringens gas gangrene toxin breaks down muscle third most common cause of bacterial food poisoning in the U S behind Salmonella and S aureus characteristic double zone of hemolysis around colonies 24 8 Gram positive C tetani tetanus often associated with puncture wounds disease course autolysis neurotoxin release binding to cells in CNS blockage of inhibitory impulses prolonged muscle spasms T in DPT vaccine 25 Gram positive C botulinum botulism rare but often fatal the mechanism of action of the toxin is similar to C tetani binding site differs the three manifestations of the disease are food wound and infant botulism trademark is acute flaccid paralysis 26 Gram positive Propionibacterium Eubacterium Bifidobacterium Actinomyces normal flora opportunistic pathogens Lactobacillus prevents yeast infection competes for nutrients found in yogurt and other foods Mobiluncus not part of normal flora associated with bacterial vaginosis 27 9 Gram positive bacilli aerobic Listeria monocytogenes primary habitat is soil and decaying vegetable matter will multiply at refrigerator temperatures contaminated foods are the primary vehicles of transmission listeriosis 2500 cases year in U S 28 Gram positive Listeria monocytogenes seen almost exclusively in neonates pregnant women and immunocompromised individuals untreated transplacental infection can lead to premature labor septic abortion neonatal meningitis colony morphology closely resembles Strep group B differentiate using Gram stain and catalase 29 Gram positive bacilli aerobic Erysipelothrix veterinary pathogen human infection subsequent to animal exposure is rare Corynebacterium most species are harmless saprophytes diphtheroids C diphtheriae causes diphtheria D in DPT vaccine 30 10 Gram positive Bacillus species spore formers most are troublesome contaminants B anthrasis anthrax rare B cereus food poisoning Nocardia inhabit soil vegetation water infection rare is subsequent to inhalation or inoculation through breaks in the skin 31 Gram negative 32 11