細菌性前立腺炎：急性および慢性感染症の理解

最終更新日： 8月 16, 2026

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It is an unwritten rule of manhood that we do not talk about what goes on below the belt until something goes wrong. We track our gym progress, watch our cholesterol, maybe even monitor our testosterone. But when a deep pelvic ache sets in, or a quick trip to the bathroom starts to feel like forcing water through a crimped garden hose, it gets our full attention very fast.

Start here if you are unwell right now. 骨盤の痛み with fever or chills, or an inability to pass urine at all, is not something to read an article about — it is a reason to go to an emergency department today. Acute bacterial prostatitis can progress to a bloodstream infection, and a blocked bladder needs a catheter rather than painkillers. The rest of this article is for working out what is going on when you are not in that situation.

Prostatitis — a broad term for infection, inflammation or pain in the prostate gland — is remarkably common. Because the prostate sits just beneath the bladder and wraps around the urethra, any swelling or infection acts like a bottleneck, triggering urinary symptoms and a real dent in quality of life. In an earlier article I explained chronic pelvic pain syndrome and the patient-friendly way it is diagnosed. Today I want to focus on the two bacterial forms, and exactly how antibiotics clear them.

Prostatitis is divided into four types: acute bacterial (Type I), chronic bacterial (Type II), chronic pelvic pain syndrome (Type III), and a silent, symptom-free inflammatory form found by accident (Type IV) that needs no treatment. Let us unpack the two infectious types.

Type I: Acute Bacterial Prostatitis — The Sudden Storm

Think of acute bacterial prostatitis as an immediate, severe event — essentially a urinary tract infection that has spread into the prostate itself. Unlike the subtler prostate problems that simmer for months, this one strikes out of nowhere and can affect men of any age. The symptoms are impossible to ignore: a sudden spiking fever with chills and feeling generally unwell, intense pelvic or genital pain, and an urgent, frequent need to urinate with sharp burning. In some cases the prostate swells enough to block urine completely — a situation requiring emergency care.

What causes it? In the great majority of cases the culprits are common bacteria from the digestive or urinary tract, with 大腸菌 the number-one offender. They reach the prostate by travelling up the urethra or by infected urine refluxing into the prostate’s ducts, and they can occasionally be introduced during procedures such as catheterisation or prostate biopsy. Sexually transmitted infection is an uncommon cause overall, but in a younger man with a new partner it is worth testing for rather than assuming — the treatment is different.

How It Is Diagnosed

A very gentle rectal examination typically reveals a swollen, intensely tender prostate, and that tenderness is the main clue separating acute prostatitis from a simple bladder infection. A urine culture is the key test and must be taken before the first antibiotic dose, so the laboratory can identify the exact organism and which drugs will kill it. Because an acute infection can spill into the bloodstream, blood cultures are often taken too, and if there is any sign of urine being trapped, an ultrasound measures it — the same measurement discussed in why a bladder may not be emptying.

One important note about PSA testing: the prostate-specific antigen level often rises during an acute infection simply from inflammation. Checking PSA during an active infection is unnecessary and can cause a false cancer scare. Any cancer screening should wait until the infection has fully cleared — usually a matter of weeks, not days.

The Antibiotic Plan

Because acute prostatitis carries a real risk of progressing to a bloodstream infection or a prostate abscess, prompt antibiotics are essential. The silver lining is that an acutely inflamed prostate is highly permeable, so antibiotics that normally struggle to enter prostate tissue cross over easily. Men with signs of serious systemic infection, those who cannot keep medication down, and those who have recently had a prostate biopsy are treated in hospital with intravenous antibiotics; others can usually start oral treatment at home. Once the fever breaks, treatment is tailored to the culture results and continued for the full course.

One thing to watch for at home: treatment should be making a visible difference within two to three days. If the fever persists or the pain is still severe after that, go back — it may mean the antibiotic does not match the organism, or that a prostate abscess has formed, which is diagnosed on imaging and usually needs drainage rather than more tablets.

The single most important rule: do not cut the course short just because you feel better after a few days. Stopping early leaves partially resistant bacteria alive deep in the prostate, setting the stage for a chronic, recurring problem — which brings us to Type II.

Type II: Chronic Bacterial Prostatitis — The Hidden, Recurring Fire

If acute prostatitis is a sudden wildfire, chronic bacterial prostatitis is a smouldering underground ember. It is a persistent, long-term infection that keeps flaring despite completing standard antibiotic courses. Its hallmark is recurrent urinary tract infections caused by the same bacterial strain. A man takes antibiotics, the symptoms vanish, everything seems fine — then weeks or months later the identical burning, frequency and urgency return. Unlike the acute form, this one usually comes without fever, and between flares a man may have only mild pelvic discomfort or no symptoms at all.

Why It Is So Hard to Kill: The Biofilm Shield

Two things make this infection stubborn. First, chronic infection creates patchy, scarred zones in the gland, and these dense areas restrict medication from diffusing into deep tissue. Second, and more importantly, most of the responsible bacteria can build biofilms: a slimy protective matrix they secrete around themselves, which physically blocks both immune cells and standard antibiotic concentrations from reaching the bacteria inside.

Pinpointing the Source

To treat it correctly, a doctor must show the recurring bacteria actually live deep inside the prostate rather than floating in the bladder or urethra. Traditionally this is done with localisation testing that compares urine samples collected before and after a prostate massage: if the post-massage sample grows far more bacteria, the prostate is confirmed as the source. As discussed in my companion article on chronic pelvic pain, semen culture is increasingly used as a more tolerable alternative. It is also worth ruling out the mechanical reasons a bladder does not empty — residual urine is itself a driver of recurrent infection.

The Antibiotic Plan: Penetration and Patience

Eradicating bacteria shielded by scar tissue and biofilms needs a different strategy from a simple bladder infection. When the prostate is not actively inflamed it forms a formidable barrier that most common antibiotics bounce off. To penetrate non-inflamed prostate tissue an antibiotic needs specific chemical properties, and the fluoroquinolone class crosses that barrier well, which is why it has traditionally been first choice. The other key variable is duration: a minimum of several weeks, sometimes longer where biofilm or heavy scarring is involved. Where fluoroquinolones cannot be used, there are alternatives, also given for an extended course.

What You Should Know About Fluoroquinolones

These are effective drugs and, for a deep prostate infection, often the right ones. They also carry a set of uncommon but serious side effects that regulators have warned about specifically, and a man taking them for several weeks deserves to know what to look out for rather than discovering it afterwards.

• Tendon pain, swelling or rupture — most often the Achilles tendon. New pain in a tendon means stop the drug and contact your doctor the same day, and avoid strenuous exercise of that limb until you have been assessed. Risk is higher in older men, in those also taking corticosteroids, and after organ transplant.
• Nerve symptoms — new numbness, tingling, burning or weakness in the hands or feet should be reported promptly, as these can persist.
• Mood, sleep or confusion changes, which usually settle after stopping but are worth mentioning rather than tolerating.
• A caution in men with an aortic aneurysm or a strong family history of one, where these drugs are generally avoided if there is a reasonable alternative.
• Severe or persistent diarrhoea during or after any long antibiotic course needs assessment rather than an anti-diarrhoeal from the pharmacy.

None of this is a reason to refuse treatment for a genuine deep infection, where the alternative is a problem that recurs for years. It is a reason to take the drug for a confirmed infection rather than a hopeful one, and to speak up early if something feels wrong.

Acute vs Chronic at a Glance

Acute bacterial prostatitis is sudden and explosive, comes with fever and chills, involves a uniformly inflamed and drug-permeable gland, is diagnosed with a gentle examination and a urine culture, and is treated for a few weeks. Chronic bacterial prostatitis is slow and cyclic, comes without fever, involves a scarred gland protected by biofilms, needs localisation testing, and requires a longer, high-penetration course. Same family of bacteria, very different battles.

When It Is Not Bacterial at All

A critical point: the overwhelming majority of men who walk into a clinic with chronic prostatitis symptoms do not have a bacterial infection. They have chronic pelvic pain syndrome (Type III) — persistent urogenital pain for months, often with urinary or sexual symptoms, but with negative cultures. Because there is no active infection, guidelines explicitly do not recommend routine antibiotics. Repeated courses just in case do not help, expose men to the side effects listed above, and fuel resistance. It is managed instead with muscle-relaxing medication, short-term anti-inflammatories, pelvic floor physical therapy and nerve-modulating treatment. (Covered in depth in my article on chronic prostatitis and pelvic pain.)

The same principle applies one step earlier: bacteria found in the urine of a man with no symptoms usually need no antibiotics at all. A positive culture is not, by itself, a diagnosis.

The Takeaway: Partner With Your Urologist

When treating a true bacterial infection in the prostate, precision is everything. Success means matching the exact organism in your culture with an antibiotic chemically capable of crossing the blood-prostate barrier, and maintaining it long enough to reach bacteria sheltering in biofilm and scarred tissue. If you have sudden pelvic pain with fever, or find yourself trapped in a loop of recurring bladder infections, do not ignore it.

Dr. Soarawee Weerasopone consults at バンコク病院本部 and at Samitivej Sriracha Hospital, Chonburi — 088-022-1445, with the wider range of conditions set out under 泌尿器科.

バンコク病院の遠隔医療は、来院が困難な患者様（海外からの患者様を含みます）を対象にご利用いただけます。泌尿器科宛てに事前にメールでご手配ください。 bhquro@bdms.co.th. It suits reviewing culture results and planning a long course; it is not appropriate for an acute infection with fever, which needs to be seen. Samitivej Sriracha is in-person only.

Reference: Borgert BJ, Wallen EM, Pham MN. Prostatitis: A Review. JAMA. 2025 Sep 16;334(11):1003-1013. doi:10.1001/jama.2025.11499.

お客様からよくいただくご質問

急性細菌性前立腺炎と慢性細菌性前立腺炎の違いは何ですか？

Acute bacterial prostatitis comes on suddenly and severely, with fever, chills, intense pelvic pain and painful urination — essentially a urinary infection that has spread into the prostate, and a potential emergency. Chronic bacterial prostatitis is a slow, recurring infection by the same bacterial strain, usually without fever, where symptoms keep returning weeks or months after antibiotics. The chronic form is harder to treat because the gland becomes scarred and the bacteria hide inside protective biofilms.

When does prostatitis need emergency care?

Pelvic pain with fever or chills, or complete inability to pass urine, needs same-day emergency assessment: acute bacterial prostatitis can progress to a bloodstream infection, and a blocked bladder needs a catheter. Also return promptly if you are already on antibiotics and the fever or severe pain has not started improving within two to three days, which can mean the drug does not match the organism or that an abscess has formed and needs drainage.

細菌性前立腺炎の抗生物質治療には、どのくらいの期間が必要ですか？

Acute bacterial prostatitis is typically treated for a few weeks; chronic bacterial prostatitis requires a longer course of at least several weeks, sometimes extended to overcome biofilms and scarred tissue. Complete the entire course even after you feel better, because stopping early leaves resistant bacteria deep in the prostate and can turn an acute infection into a chronic, recurring one.

What side effects should I watch for on a long antibiotic course?

Fluoroquinolones, often used because they penetrate prostate tissue, carry uncommon but serious risks that regulators warn about. New tendon pain or swelling, most often the Achilles, means stop the drug and contact your doctor the same day. New numbness, tingling or weakness in the hands or feet should be reported promptly. Mood, sleep or confusion changes are worth mentioning. They are generally avoided where there is an aortic aneurysm or strong family history. Severe or persistent diarrhoea during or after any long course needs assessment rather than an over-the-counter remedy.

一部の前立腺感染症が治りにくいのはなぜですか？

The gland develops patchy, scarred zones that block medication from diffusing in, and most of the bacteria can build biofilms — a protective shield that keeps both the immune system and standard antibiotics from reaching them. When the prostate is not inflamed it also forms a strong barrier that many antibiotics cannot cross, so only specific deep-penetrating drugs given for an extended period fully eradicate the infection.

前立腺炎がある場合、PSA検査を受けるべきですか？

No. PSA often rises during an active prostate infection simply because of inflammation, not cancer. Testing then is unnecessary and can cause a false cancer scare. If prostate cancer screening is needed it should be done only after the infection has completely cleared, so the result means something.

Do antibiotics help chronic pelvic pain syndrome?

No. Most men with chronic prostatitis symptoms actually have chronic pelvic pain syndrome, where cultures show no bacteria. Guidelines do not recommend routine antibiotics, because there is no infection to treat — repeated courses cause side effects and promote resistance. It is managed with alpha-blockers, anti-inflammatories, pelvic floor physical therapy and nerve-modulating medication instead.

免責事項 This content is written and reviewed by Dr. Soarawee Weerasopone, a board-certified urologist at Bangkok Hospital Headquarters. It is intended for educational purposes only and does not constitute medical advice. Antibiotic therapy must be guided by a physician and proper cultures. No advice, diagnosis or prescription is given through personal messaging channels or social media. Acute bacterial prostatitis with high fever or inability to urinate is a medical emergency — seek immediate care. Always consult a qualified healthcare professional before starting or changing any medical treatment.