Staphylococcus epidermidis lives harmlessly on everyone’s skin, so finding it in a urine sample is often a sign that the sample picked up skin germs on the way out. It can also cause genuine bladder and kidney infections, usually when something in the urinary tract, most often a catheter, gives it a surface to cling to. The same lab result can therefore mean nothing at all or a real infection, and the difference depends on your situation more than on the germ’s name.
Contamination or Real Infection
Your report may list the germ as coagulase-negative staph, or CoNS, a family of related skin staph that includes S. epidermidis. A urine culture grows whatever germs are in the sample and counts them as colony-forming units per millilitre, written cfu/mL. Many doctors still describe S. epidermidis in urine as a common contaminant and only rarely a cause of infection.1HealthTap. A member asked: I took a urine culture test last week and it shows that the bacteria is staphylococcus epidermidis…
Sometimes, though, it is truly in the bladder. In older adults with suspected complicated infections, CoNS showed up both in ordinary midstream samples and in urine taken straight from the bladder with a catheter.2Pathnostics. Staphylococcus Epidermidis in UTIs: Mechanisms and Diagnosis Urine markers of immune activity were also raised in those samples, which links the germ to a real infection response.3Pathnostics. Staphylococcus Epidermidis in UTIs: Mechanisms and Diagnosis
A contaminated sample usually looks different on paper. It often shows several kinds of germs at once rather than one, and the colony count tends to be low, well under 100,000. There may be few or no white cells in the urine. If you have no symptoms, many doctors simply repeat the test or do nothing.
Clues point the other way in true infections. People whose urine grew S. epidermidis alone at more than 100,000 cfu/mL had more white blood cells in their urine than people with negative cultures.4Clinical Laboratory Science. Significance of Staphylococcus Epidermidis in Urine Cultures at Michigan Medicine They more often had a positive leukocyte esterase, the white-cell sign on a urine dipstick, and they were more likely to have a urinary catheter.5Clinical Laboratory Science. Significance of Staphylococcus Epidermidis in Urine Cultures at Michigan Medicine
That is why identical lab wording can lead to different actions. A person with a catheter, fever, or new pain in the flank or lower abdomen gets the same result taken far more seriously than a healthy person with no symptoms. Without symptoms, many guidelines advise against treating germs in the urine at all, because antibiotics can cause side effects and breed resistance without helping.
If a repeat is ordered, a cleaner sample helps. Wash your hands and clean the genital area with the wipe provided, front to back. Let the first part of the stream go into the toilet, then catch the middle, and avoid touching the inside of the cup or lid. Deliver the sample quickly or keep it refrigerated, since germs multiply at room temperature.
When the result comes back, ask whether the germ grew alone and what the count was, and whether white cells or the white-cell dipstick sign were present. Mention any catheter, stones, recent surgery, or past urinary problems. It is also fair to ask whether a repeat or catheter sample would help before antibiotics are started.
Who Gets Real S. epidermidis Urinary Infections
S. epidermidis infections are tied to urinary catheters, where it builds sticky layers on the tubing.6Pathnostics. Coagulase-negative Staphylococci Group It is also linked to urinary and kidney infections in young children, adolescent boys, and children with abnormalities of the urinary tract.7Pathnostics. Coagulase-negative Staphylococci Group It has been reported in an adult woman with recurrent infections, and in men with kidney stones whose infection spread to the blood.8Pathnostics. Coagulase-negative Staphylococci Group In newborns treated at one maternity hospital, it made up about 6% of urine germs found.9Medical Principles and Practice. Prevalence of Urinary Tract Infections and Antibiotic Susceptibility Patterns of Uropathogens among Neonates in Maternity Hospital, Kuwait: A Six-Year Retrospective Study
A skin germ rarely infects a healthy bladder. Normal urine flow flushes germs out before they settle, and the bladder lining resists this germ better than other staph species. A catheter or stone gives it a surface the flushing cannot clear, and blocked or abnormal flow lets urine sit, giving germs time to multiply.
Babies and small children have less developed urinary tracts, and some are born with structural differences that let urine back up or pool. Newborns in hospital also have more contact with devices and healthcare surroundings, which gives skin germs more chances to enter. A urine infection in a young child with fever should always be checked by a doctor, because it can involve the kidneys. Children with repeated infections are often scanned for an underlying abnormality, since treating the germ alone will not fix a structural cause.
Long-running bladder symptoms are a second group. Women with urge leakage, stress leakage, or painful bladder syndrome carried S. epidermidis in their urine more often than women without symptoms.10PubMed Central. The Urobiomes of Adult Women With Various Lower Urinary Tract Symptoms Status Differ: A Re-Analysis In one gene-based study, it appeared only in the urine of people with painful bladder syndrome, raising the possibility that some of their symptoms come from unrecognised infection.11Pathnostics. Coagulase-negative Staphylococci Group This link is still being studied and does not mean every painful bladder is infected.
If you have chronic bladder symptoms, standard cultures may miss low numbers of slow-growing germs, so it is reasonable to ask whether a repeat or extended culture is worth doing. Don’t assume antibiotics will fix long-standing pain; discuss it with a urologist. A symptom diary can show your doctor patterns that a single visit would not.
How S. epidermidis Causes Infection
Its main weapon is biofilm, a slimy, attached community of bacteria wrapped in a material they make themselves. Building biofilm is the key way S. epidermidis causes infections on medical devices.12PubMed Central. Staphylococcus epidermidis Uses Distinct Mechanisms of Biofilm Formation To Interfere with Phagocytosis and Activation of Mouse Macrophage-Like Cells 774A.1 It prefers to form biofilm on non-living surfaces such as plastic tubing,13PubMed Central. Accumulation-associated protein enhances Staphylococcus epidermidis biofilm formation under dynamic conditions and is required for infection in a rat catheter model and a surface protein helps it pile up into thicker biofilm when urine is flowing over it.14PubMed Central. Accumulation-associated protein enhances Staphylococcus epidermidis biofilm formation under dynamic conditions and is required for infection in a rat catheter model
On a catheter, that coating builds layer by layer over days to weeks. Germs deep inside are shielded from the body’s defences, and pieces can break off and seed new infections.
A catheter helps the germ in the first place because, within hours of insertion, it becomes coated with proteins from the body, and bacteria can attach to this coating. The tube also gives a path from the skin into the bladder, along the outside surface or through the drainage system. The longer a catheter stays in, the more likely a biofilm is to form. Once the biofilm is established, it is much harder to clear than free-floating germs.
Biofilm is not always switched on. Among germs from catheter infections, only about 1 in 4 made biofilm under normal conditions, yet stress or antibiotics switched it on in many others.15PubMed. Detection of the icaADBC gene cluster and biofilm formation in Staphylococcus epidermidis isolates from catheter-related urinary tract infections A strain that looks harmless in the lab can therefore still form biofilm inside you once antibiotics are given.
The healthy lining is a different story. In tests on human ureter tissue, S. epidermidis did not stick to the lining.16PubMed. In vitro adherence of Staphylococcus saprophyticus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus aureus to human ureter Its relative S. saprophyticus, a common cause of bladder infections in young women, sticks to urinary cells far better.17PubMed. Surface properties of Staphylococcus saprophyticus and Staphylococcus epidermidis as studied by adherence tests and two-polymer, aqueous phase systems
It can also go unnoticed. S. epidermidis infections cause much less inflammation than infections with its cousin S. aureus,18PubMed Central. Immune Evasion Mechanisms of Staphylococcus epidermidis Biofilm Infection so symptoms can be mild or vague. And it makes urease, an enzyme that breaks down urea and is linked to stones and prostate calcifications.19Pathnostics. Staphylococcus Epidermidis in UTIs: Mechanisms and Diagnosis
In practice, breaking down urea makes urine more alkaline, and alkaline urine lets minerals crystallise into crusts and stones. Crusts can block catheters and force tube changes. Stones then shelter the germ, keeping the infection going.
Why It Can Be Hard to Treat
Resistance is common. In urine strains from one study, about 9 in 10 resisted penicillin and about two thirds resisted tetracycline and erythromycin.20Reviews in Medical Microbiology. Phenotypic and molecular characterization of antimicrobial resistance in Staphylococcus epidermidis strains isolated from urinary tract infections and bovine mastitis In another group of urine strains, about 1 in 6 was methicillin-resistant, known as MRSE, and some came from people outside hospital.21Archives of Clinical Infectious Diseases. Molecular Characteristics of Biofilm-Producing Methicillin-Resistant Staphylococcus epidermidis Isolates Causing Urinary Tract Infections So the lab usually tests which antibiotics work before the choice is final.
Those percentages describe groups of strains, not yours, so your own sensitivity report matters more than any average. Strains from hospitals and long-term care tend to be more resistant, and earlier antibiotic courses and recent hospital stays raise the chance that yours resists common drugs.
The sensitivity report lists each antibiotic as working or resistant against your strain. Your doctor may switch drugs once it arrives, often after two to three days. Finish the course as prescribed even if you feel better, and tell your doctor about past antibiotic courses and allergies.
Biofilm adds another shield. Germs inside a mature biofilm tolerated every antibiotic tested far better than free-floating germs.22PubMed Central. Staphylococcus epidermidis Biofilms Have a High Tolerance to Antibiotics in Periprosthetic Joint Infection Standard doses of vancomycin, levofloxacin, daptomycin and minocycline all failed to clear an established biofilm in lab tests,23PubMed Central. Eradication of Staphylococcus epidermidis within Biofilms: Comparison of Systemic versus Supratherapeutic Concentrations of Antibiotics because the drug levels needed to clear biofilm on plastic can’t be reached with normal dosing.24PubMed Central. Eradication of Staphylococcus epidermidis within Biofilms: Comparison of Systemic versus Supratherapeutic Concentrations of Antibiotics Infections tied to a device therefore tend to return if the device stays in.
Lab tests use free-floating germs, so a drug that works on paper may fail against a coated catheter. Symptoms that recur after treatment point to a hidden source like a device or stone, and after repeat infections it is worth asking whether imaging or a urology review is needed.
Treatment When You Have a Catheter
If a catheter has been in for two weeks or more, replacing it helps symptoms clear faster.25Praxis Medical Insights. What is the treatment approach for a Staphylococcus epidermidis urinary tract infection Urine for culture should be taken from a freshly placed catheter, not the old one,26Praxis Medical Insights. What is the treatment approach for a Staphylococcus epidermidis urinary tract infection and the catheter should come out completely as soon as it is no longer needed.27Praxis Medical Insights. What is the treatment approach for a Staphylococcus epidermidis urinary tract infection
The order matters because the old catheter carries a biofilm that releases germs into the urine, so a sample from it can show germs that are on the plastic, not in the bladder. Replacing it first means the sample reflects what is really in the bladder. It also gives the antibiotic a better chance, since fresh plastic has no established biofilm.
Sometimes removal alone is enough. After prostate surgery, removing the catheter without antibiotics cleared S. epidermidis from the urine in all 9 men who had it.28PubMed. Diagnostic criteria and natural history of catheter-associated urinary tract infections after prostatectomy Infection persisted in 5 of 6 men with other bacteria.29PubMed. Diagnostic criteria and natural history of catheter-associated urinary tract infections after prostatectomy
If you use a catheter long term, expect a change of catheter as part of the workup when symptoms appear; your nurse may swap it before taking a new sample. Germs in the urine without symptoms are often left untreated. Fever, flank pain, confusion or blood in the urine need prompt attention, and it is worth asking about the shortest catheter time possible.
Daily habits lower the risk. Wash your hands before touching the catheter or bag, keep the bag below bladder level so urine doesn’t flow back, avoid kinks, and empty the bag regularly. Drink enough fluid to keep urine flowing, unless you’ve been told otherwise.
How the Lab Identifies It
Many labs now identify germs by the pattern of proteins they contain, a method more accurate than older chemical tests.30PubMed. Evaluation of the Biotyper MALDI-TOF MS system for identification of Staphylococcus species It named the right staph species about 97% of the time.31PubMed. Evaluation of the Biotyper MALDI-TOF MS system for identification of Staphylococcus species
The test works by placing a tiny amount of a bacterial colony on a plate and hitting it with a laser, which breaks it into charged pieces. The machine measures how fast those pieces travel, producing a pattern characteristic of each species, and the lab compares it to a library of known germs to name the match. It is commonly called MALDI-TOF and takes only minutes once there is a colony to test.
The wait is mostly for growth. Germs need about a day to grow on the culture plate, and antibiotic sensitivity usually adds another day or two. Your doctor may start treatment before results arrive if you are unwell.
New Treatments Being Tested
Phages are viruses that infect only bacteria, attaching to a specific type and destroying it from within. Each one targets particular bacteria, so it can be chosen to match the germ causing the infection. Some also make enzymes that break down biofilm, which is why they interest researchers working on catheters. They do not infect human cells.
In lab tests, coating catheters with a phage that attacks S. epidermidis cut biofilm sharply over a day.32PubMed Central. Using Bacteriophages To Reduce Formation of Catheter-Associated Biofilms by Staphylococcus epidermidis Phage therapy may help with chronic and catheter infections by breaking up biofilm and helping antibiotics work.33PubMed Central. Phages as potential life-saving therapeutic option in the treatment of multidrug-resistant urinary tract infections These are mostly early results, not standard care.
Today, phage therapy is mainly available through research trials and may suit people with repeated resistant infections. If infections keep returning, ask a urology or infection specialist about trials.