Microbiology Quiz: Bacterial Growth Factors and Culture Media

Bacterial Growth and Requirements

• Haemophilus influenzae requires heme and NAD to grow on an agar.

Culture Media

• Middlebrook medium is used to culture sputum to confirm a diagnosis of pulmonary tuberculosis.
• Xylose-Lysine-Deoxycholate (XLD) medium is not used to culture Haemophilus influenzae.

Bacterial Adherence

• Pilus is a non-essential bacterial component that mediates adherence of bacteria to mucous membranes.

Bacterial Survival

• Some bacteria are unable to survive in the presence of oxygen due to lacking catalase and superoxide dismutase.

Bacterial Identification

• Streptococcus pneumoniae is identified by its shiny, greenish colonies on a blood agar disc, which are inhibited by optochin, and its Gram-positive spherical shape growing in chains with a positive Quellung reaction.

Bacterial Characteristics

• Bacteria are prokaryotic, containing DNA only, and multiply by binary fission, producing either endotoxin or exotoxin.

Flagella

• Monotrichous refers to a single flagellum at one end, atrichous has no flagellum, lotrichous has a tuft of flagella at one or both ends, and peritrichous has flagella surrounded around the cell.

Bacterial Types

• Lactobacillus is an aerotolerant bacterium, meaning it does not require oxygen for growth.

Autoclave Sterilization

• Geobacillus stearothermophilus is the biological indicator for autoclaves.

Bacterial Growth Phases

• The lag phase is also known as the adjustment phase, the log phase is when the bacteria grow exponentially, the stationary phase has no net growth of the bacterial population, and the death phase has a decline in the bacterial population.

Causes of Bacterial Death

• Causes of bacterial death include food shortage, decreased pH, and increased concentration of toxic products.

Sterilization Indicators

• Geobacillus stearothermophilus is the biological indicator for autoclaves, and Thermus aquaticus is the indicator for ovens in sterilizing glassware.

Chemical Sterilants

• Glutaraldehyde is a chemical sterilant commonly used for sterilizing equipment.

Antiseptics

• Hexachlorophene is not an antiseptic, while alcohol, chlorhexidine, and QUATS are antiseptics.

Normal Flora

• The most abundant normal flora in throat and nasopharyngeal swab specimens is Streptococcus pyogenes.

Autoclave Settings

• The settings for an effective autoclave are a temperature of 121°C, for at least 15 minutes, using 15 psi of pressure.

Gram Staining

• Iodine is the mordant in Gram staining, not a counterstain.

Sterilization of Surgical Materials

• Glutaraldehyde can effectively kill Clostridium tetani in surgical materials.

Endotoxins

• Endotoxins induce the overproduction of IL-1.

Oxygen-Rich Environment

• Nocardia will not survive in an oxygen-rich environment.