Microbiology - NCLEX-PN

The two most common bacterial arrangements are Staph- and Strep-. Staph- is a non-symmetrical arrangement like a cluster of grapes. Strep- indicates a chain of bacteria.

The three most common bacterial shapes are listed below.

Coccus—round or oval

Bacillus—rectangular or rod-shaped

Spirilla (spirochete)—spiral

By breaking down names into arrangement and shape, students can predict or identify the appearance of an organism by its name. In the example Staph indicates arrangement in a chain. Coccus indicates round or oval in shape. Therefore, Staphylococci are round or oval-shaped organisms arranged in a cluster.

Bordetella pertussis is a Gram negative, rod-shaped aerobe. It requires oxygen to function and commonly infects the respiratory tract of young children, causing whooping cough.

Neisseria gonorrhoeae is a Gram negative coccus bacterium that generally presents as a diplococcus (in pairs of cocci).

_Staphyloccocus aureus are Gram positive cocci. Chlamydia trachomatis and Rikettsia prowazekii are both classified as Gram negative rods and Neisseria meningitidis are Gram negative cocci.

All of the bacteria listed are Gram positive except Salmonella, which is a Gram negative facultative rod.

Vibrio cholerae is classified as Gram negative facultative rods. This bacteria is the most well known amongst the Vibrio species as it's the cause of cholera, which produces a toxin that causes very severe diarrhea.

Bacteria or any other microbes that feed on dead matter are termed saprophytes. Thermophilic microbes thrive in heated environments, halophiles such as _Vibrio parahaemolyticu_s prefer salt water, and archaebacteria are a group of bacteria found in high heat, high salt content locations such as sewage treatment plants and are able to tolerate many extreme habitats.

E. coli is a Gram negative rod. It's a lactose fermenting bacteria commonly implicated in urinary tract infections and less frequently in gastroenteritis.

Staphylococcus species are Gram positive, catalase positive cocci. The most famous member of this bacterial species, Staphylococcus aureus, is commonly implicated in skin infections, upper respiratory infections, and gastroenteritis (food poisoning).

The Gram stain is a test used to help classify bacteria based on the presence of peptidoglycan in the cell wall. Bacteria with a thick peptidoglycan cell wall will stain dark purple, and are termed Gram positive. On the other hand, if there is no peptidoglycan cell wall (or a very thin one), it will show up as pink. This is termed Gram negative. This distinction is particularly important when prescribing classes of antibiotics, as the cell wall is commonly targeted by antibiotics.

Botulism toxin inhibits acetylcholine release from the presynaptic nerve terminal, causing flaccid paralysis. Death in botulism exposure is generally due to respiratry failure. Tonic paralysis is the cause of respiratory arrest in other toxicity exposures, such as exposure to tetanus toxin.

Rickettsia rickettsii causes Rocky Mountain Spotted Fever, and is spread by dermacentor ticks. It causes fever, headache, muscle pain, and a rash. Borrelia burgdorferi is associated with Lyme disease, e_hrlichia chaffeensis_ is associated with human monocytotropic ehrlichiosis, andr_ickettsia helvetica_ is associated (very rarely) with meningitis.

While all of the listed organisms can cause diarrhea, Cryptosporidium, a protozoa, is the most commonly isolated organism in HIV positive patients presenting with diarrhea.

30% of cases of Guillain-Barré are preceded by infection by C_ampylobacter jejuni._ There is no known association between S_taphylococcus aureus, Salmonella,_ or E.coli and Guillain-Barré syndrome.

The most commonly implicated bacteria in epiglottiits are H. influenzae type B, Streptococcus spp, and Staphylococcus aureus. _Campylobacter jejuni is a common cause of food poisoning.

The question requires the knowledge that Escherichia coli is a facultative, Gram negative, lactose fermenting bacteria. EMB (eosin methylene blue), or Mac (MacConkey) media is superior for isolating Escherichia coli because it is both selective and differential. Nutrient agar is neither selective nor differential. Selenium enriched media would not help identify this bacteria because Escherichia coli does not require this supplemented media to grow. Phenethyl alcohol can be used to select for anaerobic bacteria, which is of no utility in this situation.

Genital warts is caused by human papillomavirus. All other sexually transmitted infection is correctly matched with its causative agent.

The question stem describes bubonic plague which is caused by Yersinia pestis. Staphylococcus aureus causes skin infections, toxic shock, and food poisoning. _Bacillus anthraci_s causes anthrax, which is similar to plague, but does not cause buboes. Borrelia burgdorferi causes lyme disease., which presents as rash and arthralgia.

The colon is anaerobic and the bladder is aerobic. This fact explains why E. coli normally lives in an anaerobic environment, but can also survive aerobically. Facultative anaerobes normally live in anaerobic conditions but can adapt to aerobic conditions. Microaerophiles describes bacteria that are obligate aerobes, but are poisoned by high levels of oxygen and thus require specific oxygen levels to grow.