Most Bartonella infections, particularly cat scratch disease, resolve on their own without antibiotics. When treatment is needed, the approach depends entirely on which part of the body is affected and how severe the infection is. Simple cases may need only a short course of a single antibiotic or no medication at all, while serious complications like heart valve infection require months of combination therapy.
Mild Cat Scratch Disease Often Clears on Its Own
Cat scratch disease is the most common form of Bartonella infection, and it typically shows up as swollen, tender lymph nodes near a cat scratch or bite. It occurs most often in children under 15. Whether antibiotics actually shorten the illness is still debated, and many people recover fully without any medication.
When doctors do prescribe an antibiotic for uncomplicated cat scratch disease, azithromycin is the standard choice. It has been shown to shrink swollen lymph nodes faster than no treatment. The typical course is just five days: a higher dose on the first day, then a lower dose for the remaining four. That brevity makes it one of the simpler antibiotic regimens you’ll encounter. The swollen nodes themselves can take weeks or even a couple of months to fully resolve, even with treatment, so don’t be alarmed if the lump lingers after you finish the pills.
Bacillary Angiomatosis Requires Longer Treatment
Bartonella can cause a condition called bacillary angiomatosis, where reddish-purple skin lesions develop from abnormal blood vessel growth. This happens almost exclusively in people with weakened immune systems. Unlike standard cat scratch disease, bacillary angiomatosis needs a longer course of antibiotics, typically around three months.
Erythromycin taken four times daily is the first-line treatment. If you can’t tolerate erythromycin or have a reason to avoid it, doxycycline taken twice daily for the same three-month period is the alternative. Stopping treatment too early raises the risk of relapse, which is a recurring theme with the more serious forms of Bartonella infection.
Heart Valve Infection Needs Aggressive Combination Therapy
Bartonella endocarditis, an infection of the heart valves, is the most dangerous manifestation and requires the most intensive treatment. This is one of the few situations in infectious disease where only aminoglycoside antibiotics (a class given intravenously) have true bacterial-killing power against Bartonella. Most other antibiotics simply stop the bacteria from multiplying without actually eliminating them.
The standard approach pairs doxycycline with gentamicin, an intravenous aminoglycoside, for the first two weeks. After that initial intensive phase, doxycycline continues alone for at least six weeks total, often longer. An alternative regimen combines doxycycline with rifampin for six weeks, then continues doxycycline for at least three months. People with HIV are treated for a minimum of three months regardless of which combination is used, because their immune systems are less able to help clear the remaining bacteria.
Some patients with Bartonella endocarditis ultimately need heart valve surgery if the infection has caused significant structural damage. The antibiotics treat the infection itself, but they can’t repair a valve that has already been destroyed.
Eye and Nerve Involvement
Bartonella can cause neuroretinitis, an inflammation of the optic nerve and retina that leads to sudden vision loss, often in one eye. This complication requires both antibiotics and corticosteroids working together. The steroids calm the intense inflammation threatening your vision while the antibiotics fight the underlying infection.
One important caution: rifampin, which is sometimes used for Bartonella, speeds up how your body breaks down both prednisone (a common steroid) and doxycycline. That means combining all three can actually undermine treatment by lowering the blood levels of the other two drugs. Clinicians managing neuroretinitis typically avoid rifampin for this reason and rely on doxycycline plus a steroid instead. With proper treatment, vision can improve dramatically within days, though relapses are possible if the inflammatory component isn’t fully controlled.
Why Treatment Duration Matters
Bartonella bacteria live inside cells, which makes them harder for antibiotics to reach. While Bartonella is technically susceptible to a wide range of antibiotic classes, including penicillins, tetracyclines, macrolides, and fluoroquinolones, that lab-dish susceptibility doesn’t always translate to real-world success. Only aminoglycosides consistently kill the bacteria outright; other drugs tend to suppress growth without fully eradicating the organism.
This is why serious Bartonella infections require such long treatment courses compared to many other bacterial infections. Cutting treatment short gives surviving bacteria a chance to rebound once antibiotic levels drop. For immunocompromised patients, the minimum treatment duration for any form of Bartonella disease is generally three months, and some need suppressive therapy even longer to prevent relapse.
Antibiotic Resistance Concerns
Macrolide resistance has been documented in Bartonella henselae, the species behind cat scratch disease. The bacteria can develop genetic mutations that block macrolide antibiotics from binding to their target, and these mutations confer resistance not just to erythromycin but also to clarithromycin and azithromycin simultaneously. Researchers have found naturally occurring resistant strains in lymph node samples from patients who had never taken antibiotics, suggesting these resistant bacteria exist in the wild and aren’t solely created by antibiotic use.
Treatment failures and relapses have been reported with erythromycin for cat scratch disease, and some experts recommend against using erythromycin alone for that reason. Azithromycin remains the preferred macrolide for uncomplicated cat scratch disease, partly because the short five-day course limits selective pressure for resistance. For more serious infections, the combination approach (pairing drugs from different classes) helps prevent resistance from derailing treatment.
What to Expect During Recovery
For a typical cat scratch disease case, expect the swollen lymph nodes to gradually shrink over weeks to months. Some nodes may drain on their own or need to be aspirated if they become very large and painful. Fatigue and low-grade fever usually resolve within a couple of weeks.
For more serious infections, recovery timelines are longer and depend on which organs are involved. Endocarditis patients may be on antibiotics for three to six months and need follow-up imaging of their heart valves. Neuroretinitis patients need regular eye exams to track vision recovery. In all cases, completing the full prescribed antibiotic course is critical, even if you feel better well before it ends.