Staphylococcus saprophyticus – causes, symptoms, diagnosis, treatment, pathology

Staphylococcus saprophyticus – causes, symptoms, diagnosis, treatment, pathology

August 7, 2019 6 By Bertrand Dibbert


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much more. Try it free today! With Staphylococcus saprophyticus, sometimes
called Staph saprophyticus, “staph” means grapes, “coccus” means round-shape, while
“saprophyticus” refers to organisms that grow on decaying organic material. So, Staphylococcus saprophyticus are round
bacteria that tend to live in grape-like clusters, and are commonly found on contaminated meat
products. Now, a little bit of microbe anatomy and physiology. Staph saprophyticus has a thick peptidoglycan
cell wall, which takes in purple dye when Gram stained – so this is a gram-positive
bacteria. It’s non-motile and doesn’t form spores,
and also, it’s a facultative anaerobe, meaning that it can live with or without oxygen. Staph saprophyticus is catalase positive,
so it makes an enzyme called catalase. We can use this to differentiate Staph saprophyticus
from other gram positive cocci, like streptococci and enterococci, which are catalase negative. To test for this, a few drops of hydrogen
peroxide are added to the colony of the suspected bacteria. So, if catalase is present, like in staph
saprophyticus, it makes hydrogen peroxide dissociate into water and oxygen, making the
mixture foam. Staph saprophyticus is also urease positive,
meaning it produces an enzyme called urease that dissociates urea into carbon dioxide
and ammonia. This can be tested by transferring a pure
sample of bacteria from the culture to a sterile tube containing a mixture of “urea agar”
broth and phenol red. Then, the mixture is incubated. So, with Staph saprophyticus, urease makes
urea dissociate into carbon dioxide and ammonia. Ammonia then makes the mixture change color
from orange-yellow to bright pink. This doesn’t happen with urease negative
Gram-positive cocci, like Streptococcus pneumoniae or Enterococcus faecalis. Furthermore, unlike many Staphylococcus species,
Staph saprophyticus and its close relative, Staph epidermidis, are both coagulase negative,
meaning they don’t produce an enzyme called coagulase. Testing for coagulase is done by transferring
a colony of the suspected bacteria in test tube containing fibrinogen-rich plasma. Coagulase-positive bacteria, like Staph aureus,
convert the soluble fibrinogen into sticky fibrin, which then visibly clumps up. With coagulase negative species, like Staph
saprophyticus or Staph epidermidis, the fibrin doesn’t clump up. Finally, to distinguish Staph saprophyticus
from Staph epidermidis, the novobiocin test is done. This is when a disk imbued with Novobiocin,
an antibiotic, is added to the culture. Staph saprophyticus is novobiocin resistant,
so the colonies remain intact, whereas Staph epidermidis is novobiocin sensitive, so the
colonies die off. Alright, now, people get Staph saprophyticus
by eating contaminated meat – but this doesn’t cause gastrointestinal disease. Instead, from the gut, bacteria gets to the
rectum, anus and eventually colonizes the perineum, becoming part of the normal flora. From the perineum, it can colonize the vagina,
where it doesn’t cause any issues, or the urethra, where it can cause a urinary tract
infection, or UTI. In fact, Staph saprophyticus is the second
most common cause of UTI after Escherichia coli. You see, the urinary PH is normally acidic,
so it’s not favorable for bacteria growth. But as soon as Staph saprophyticus gets into
the urinary system, it uses urease to hydrolyze urea into carbon dioxide and ammonia, which
is an alkali. So ammonia increases urinary PH until it’s
neutral or alkaline, favoring bacterial growth. Addition ally, ammonia can form complexes
with magnesium and sulfates, and precipitate into magnesium ammonium sulfate. This may lead to the formation of urinary
stones called struvite, which can cause urine outflow obstruction. Staph saprophyticus can also form adherent
biofilms on medical implants, typically the indwelling urinary catheters. A biofilm is basically a layer of “slime”
made of exopolysaccharides or EPS, within which Staph saprophyticus live and reproduce. Comparing a biofilm to strawberry jam, the
seeds would be the bacteria and the rest of the jam would be the EPS. Biofilms make it difficult for antibiotics
to reach the bacteria, so the infection is more difficult to treat. Staph saprophyticus infections can be treated
with antibiotics like nitrofurantoin, or a combination of trimethoprim and sulfamethoxazole. Additionally, indwelling medical devices should
be removed and replaced when there is suspicion of biofilms. Alright, as a quick recap… Staphylococcus saprophyticus is round, gram-positive,
facultative anaerobic, non-motile, non-spore forming, catalase positive, coagulase negative,
urease positive, and novobiocin resistant bacterium, which is known to be part of the
normal flora of the perineum. It is the 2nd most common cause of UTIs after
E.coli, and can also cause formation of struvite urinary stones. In can also colonize indwelling medical devices,
where it forms biofilms. Treatment relies on antibiotics like nitrofurantoin,
or a combination of trimethoprim and sulfamethoxazole, as well as removing infected indwelling devices.