Treatment depends on the type of opportunistic infection, but usually involves different antibiotics.

When infection attacks the body, "anti-infective" drugs can suppress the infection. Several broad types of anti-infective drugs exist, depending on the type of organism targeted; they include antibacterial (antibiotic; including antitubercular), antiviral, antifungal and antiparasitic (including antiprotozoal and antihelminthic) agents. Depending on the severity and the type of infection, the antibiotic may be given by mouth or by injection, or may be applied topically. Severe infections of the brain are usually treated with intravenous antibiotics. Sometimes, multiple antibiotics are used in case there is resistance to one antibiotic. Antibiotics only work for bacteria and do not affect viruses. Antibiotics work by slowing down the multiplication of bacteria or killing the bacteria. The most common classes of antibiotics used in medicine include penicillin, cephalosporins, aminoglycosides, macrolides, quinolones and tetracyclines.

Not all infections require treatment, and for many self-limiting infections the treatment may cause more side-effects than benefits. Antimicrobial stewardship is the concept that healthcare providers should treat an infection with an antimicrobial that specifically works well for the target pathogen for the shortest amount of time and to only treat when there is a known or highly suspected pathogen that will respond to the medication.

Individuals at higher risk are often prescribed prophylactic medication to prevent an infection from occurring. A patient's risk level for developing an opportunistic infection is approximated using the patient's CD4 T-cell count and sometimes other markers of susceptibility. Common prophylaxis treatments include the following:

Treatment options in persons without HIV-infection have not been well studied. Intravenous Amphotericin B combined with flucytosine by mouth is recommended.

Persons living with AIDS often have a greater burden of disease and higher mortality (30-70% at 10-weeks), but recommended therapy is with amphotericin B and flucytosine. Where flucytosine is not available (many low and middle income countries), fluconazole should be used with amphotericin. Amphotericin-based induction therapy has much greater microbiologic activity than fluconazole monotherapy with 30% better survival at 10-weeks. Based on a systematic review of existing data, the most cost-effective induction treatment in resource-limited settings appears to be one week of amphotericin B coupled with high-dose fluconazole. After initial induction treatment as above, typical consolidation therapy is with oral fluconazole for at least 8 weeks used with secondary prophylaxis with fluconazole thereafter.

The decision on when to start treatment for HIV appears to be very different than other opportunistic infections. A large multi-site trial supports deferring ART for 4–6 weeks was overall preferable with 15% better 1-year survival than earlier ART initiation at 1–2 weeks after diagnosis. A Cochrane review also supports the delayed starting of treatment until cryptococcosis starts improving with antifungal treatment.

There is usually an indication for a specific identification of an infectious agent only when such identification can aid in the treatment or prevention of the disease, or to advance knowledge of the course of an illness prior to the development of effective therapeutic or preventative measures. For example, in the early 1980s, prior to the appearance of AZT for the treatment of AIDS, the course of the disease was closely followed by monitoring the composition of patient blood samples, even though the outcome would not offer the patient any further treatment options. In part, these studies on the appearance of HIV in specific communities permitted the advancement of hypotheses as to the route of transmission of the virus. By understanding how the disease was transmitted, resources could be targeted to the communities at greatest risk in campaigns aimed at reducing the number of new infections. The specific serological diagnostic identification, and later genotypic or molecular identification, of HIV also enabled the development of hypotheses as to the temporal and geographical origins of the virus, as well as a myriad of other hypothesis. The development of molecular diagnostic tools have enabled physicians and researchers to monitor the efficacy of treatment with anti-retroviral drugs. Molecular diagnostics are now commonly used to identify HIV in healthy people long before the onset of illness and have been used to demonstrate the existence of people who are genetically resistant to HIV infection. Thus, while there still is no cure for AIDS, there is great therapeutic and predictive benefit to identifying the virus and monitoring the virus levels within the blood of infected individuals, both for the patient and for the community at large.

Fungal pneumonia can be treated with antifungal drugs and sometimes by surgical debridement.

"Actinomyces" bacteria are generally sensitive to penicillin, which is frequently used to treat actinomycosis. In cases of penicillin allergy, doxycycline is used.

Sulfonamides such as sulfamethoxazole may be used as an alternative regimen at a total daily dosage of 2-4 grams. Response to therapy is slow and may take months.

Hyperbaric oxygen therapy may also be used as an adjunct to conventional therapy when the disease process is refractory to antibiotics and surgical treatment.

Available treatment falls into two modalities: treating infections and boosting the immune system.

Prevention of Pneumocystis pneumonia using trimethoprim/sulfamethoxazole is useful in those who are immunocompromised. In the early 1950s Immunoglobulin(Ig) was used by doctors to treat patients with primary immunodeficiency through intramuscular injection. Ig replacement therapy are infusions that can be either subcutaneous or intravenously administrated, resulting in higher Ig levels for about three to four weeks, although this varies with each patient.

Antibiotics can cause severe reactions and add significantly to the cost of care. In the United States, antibiotics and anti-infectives are the leading cause of adverse effect from drugs. In a study of 32 States in 2011, antibiotics and anti-infectives accounted for nearly 24 percent of ADEs that were present on admission, and 28 percent of those that occurred during a hospital stay.

Prescribing by an infectious disease specialist compared with prescribing by a non-infectious disease specialist decreases antibiotic consumption and reduces costs.

Vaccinations exist for several biological BRD precursors, but the multitude of possible precursors complicates the process of choosing a vaccine regime. Additionally, vaccines are not completely effective in stopping the disease, but are merely helpful in mitigation. Many of the problems with vaccine effectiveness rest with improper use, such as failing to time vaccine doses appropriately, or not administering them before shipping.

Vaccines are available for a number of viral/bacterial agents, including IBR, PI3, BVD, BRSV, Pasteurella, and "Haemophilus somnus". Many of these vaccines can be given simultaneously, because of their similar dosing schedule. For example, IBR, PI3, BVD, and BRSV vaccines are often sold in combination with each other.

Common situations in which antibiotics are overused include the following:

- Apparent viral respiratory illness in children should not be treated with antibiotics. If there is a diagnosis of bacterial infection, then antibiotics may be used.

- When children with ear tubes get ear infections, they should have antibiotic eardrops put into their ears to go to the infection rather than having oral antibiotics which are more likely to have unwanted side effects.

- Swimmer's ear should be treated with antibiotic eardrops, not oral antibiotics.

- Sinusitis should not be treated with antibiotics because it is usually caused by a virus, and even when it is caused by a bacteria, antibiotics are not indicated except in atypical circumstances as it usually resolves without treatment.

- Viral conjunctivitis should not be treated with antibiotics. Antibiotics should only be used with confirmation that a patient has bacterial conjunctivitis.

- Older persons often have bacteria in their urine which is detected in routine urine tests, but unless the person has the symptoms of a urinary tract infection, antibiotics should not be used in response.

- Eczema should not be treated with oral antibiotics. Dry skin can be treated with lotions or other symptom treatments.

- The use of topical antibiotics to treat surgical wounds does not reduce infection rates in comparison with non-antibiotic ointment or no ointment at all.

Fulminant infection from meningococci bacteria in the bloodstream is a medical emergency and requires emergent treatment with adequate antibiotics. Benzylpenicillin was once the drug of choice with chloramphenicol as a good alternative in allergic patients. Ceftriaxone is an antibiotic commonly employed today. Hydrocortisone can sometimes reverse the adrenal insufficiency. Plastic surgery and tissue grafting are sometimes needed to treat tissue necrosis resulting from the infection.

Cryptococcosis is a very subacute infection with a prolonged subclinical phase lasting weeks to months in persons with HIV/AIDS before the onset of symptomatic meningitis. In Sub-Saharan Africa, the prevalence rates of detectable cryptococcal antigen in peripheral blood is often 4–12% in persons with CD4 counts lower than 100 cells/mcL.

Cryptococcal antigen screen and preemptive treatment with fluconazole is cost saving to the healthcare system by avoiding cryptococcal meningitis. The World Health Organization recommends cryptococcal antigen screening in HIV-infected persons entering care with CD4<100 cells/μL. This undetected subclinical cryptococcal (if not preemptively treated with anti-fungal therapy) will often go on to develop cryptococcal meningitis, despite receiving HIV therapy. Cryptococcosis accounts for 20-25% of the mortality after initiating HIV therapy in Africa. What is effective preemptive treatment is unknown, with the current recommendations on dose and duration based on expert opinion. Screening in the United States is controversial, with official guidelines not recommending screening, despite cost-effectiveness and a 3% U.S. cryptococcal antigen prevalence in CD4<100 cells/μL.

"Haemophilus influenzae" produces beta-lactamases, and it is also able to modify its penicillin-binding proteins, so it has gained resistance to the penicillin family of antibiotics.

In severe cases, cefotaxime and ceftriaxone delivered directly into the bloodstream are the elected antibiotics, and, for the less severe cases, an association of ampicillin and sulbactam, cephalosporins of the second and third generation, or fluoroquinolones are preferred. (Fluoroquinolone-resistant "Haemophilus influenzae" have been observed.)

Macrolide antibiotics (e.g., clarithromycin) may be used in patients with a history of allergy to beta-lactam antibiotics. Macrolide resistance has also been observed.

In the absence of vaccination (often because calves are bought unvaccinated), antibiotics can help to stop the bacterial factors of the disease. The Virginia Cooperative Extension recommends Micotil, Nuflor, and Baytril 100 as newer antibiotics that do not need daily dosing, but also notes that Naxcel, Excenel, and Adspec are effective as well.

The serious complications of HiB are brain damage, hearing loss, and even death.

The suppression of CD4 T cells by HIV (or by immunosuppressive drugs) causes a decrease in the body's normal response to certain infections. Not only does this make it more difficult to fight the infection, it may mean that a level of infection that would normally produce symptoms is instead undetected (subclinical infection). If the CD4 count rapidly increases (due to effective treatment of HIV, or removal of other causes of immunosuppression), a sudden increase in the inflammatory response produces nonspecific symptoms such as fever, and in some cases a worsening of damage to the infected tissue.

There are two common IRIS scenarios. The first is the “unmasking” of an opportunistic infection. The second is the “paradoxical” symptomatic relapse of a prior infection despite microbiologic treatment success. Often in paradoxical IRIS, microbiologic cultures are sterile. In either scenario, there is hypothesized reconstitution of antigen-specific T cell-mediated immunity with activation of the immune system following HIV therapy against persisting antigen, whether present as intact organisms, dead organisms, or debris.

Though these symptoms can be dangerous, they also indicate that the body may now have a better chance to defeat the infection. The best treatment for this condition is unknown. In paradoxical IRIS reactions, the events will usually spontaneously get better with time without any additional therapy. In unmasking IRIS, the most common treatment is to administer antibiotic or antiviral drugs against the infectious organism. In some severe cases, anti-inflammatory medications, such as corticosteroids are needed to suppress inflammation until the infection has been eliminated.

Infections most commonly associated with IRIS include "Mycobacterium tuberculosis" and cryptococcal meningitis. Persons living with AIDS are more at risk for IRIS if they are starting for the first time, or if they have recently been treated for an opportunistic infection (OI). It is generally advised that when patients have low initial CD4 T cell count and opportunistic infection at the time of their HIV diagnosis, they receive treatment to control the opportunistic infections before HAART is initiated approximately two weeks later. This is true for most OIs, except for OIs involving the central nervous system.

Because Carrion's disease is often comorbid with "Salmonella" infections, chloramphenicol has historically been the treatment of choice.

Fluoroquinolones (such as ciprofloxacin) or chloramphenicol in adults and chloramphenicol plus beta-lactams in children are the antibiotic regimens of choice during the acute phase of Carrion's disease. Chloramphenicol-resistant "B. bacilliformis" has been observed.

During the eruptive phase, in which chloramphenicol is not useful, azithromycin, erythromycin, and ciprofloxacin have been used successfully for treatment. Rifampin or macrolides are also used to treat both adults and children.

Because of the high rates of comorbid infections and conditions, multiple treatments are often required. These have included the use of corticosteroids for respiratory distress, red blood cell transfusions for anemia, pericardiectomies for pericardial tamponades, and other standard treatments.

Antibiotics are given to treat any bacterial infection present. Cough suppressants are used if the cough is not productive. NSAIDs are often given to reduce fever and upper respiratory inflammation. Prevention is by vaccinating for canine adenovirus, distemper, parainfluenza, and "Bordetella". In kennels, the best prevention is to keep all the cages disinfected. In some cases, such as "doggie daycares" or nontraditional playcare-type boarding environments, it is usually not a cleaning or disinfecting issue, but rather an airborne issue, as the dogs are in contact with each other's saliva and breath. Although most kennels require proof of vaccination, the vaccination is not a fail-safe preventative. Just like human influenza, even after receiving the vaccination, a dog can still contract mutated strains or less severe cases.

Prognosis depends greatly on the nature and severity of the condition. Some deficiencies cause early mortality (before age one), others with or even without treatment are lifelong conditions that cause little mortality or morbidity. Newer stem cell transplant technologies may lead to gene based treatments of

debilitating and fatal genetic immune deficiencies. Prognosis of acquired immune deficiencies depends on avoiding or treating the causative agent or

condition (like AIDS).

Shade, insect repellent-impregnated ear tags, and lower stocking rates may help prevent IBK. Early identification of the disease also helps prevent spread throughout the herd. Treatment is with early systemic use of a long-acting antibiotic such as tetracycline or florfenicol. Subconjunctival injections with procaine penicillin or other antibiotics are also effective, providing a "bubble" of antibiotic which releases into the eye slowly over several days.

Anti-inflammatory therapy can help shorten recovery times, but topical corticosteroids should be used with care if corneal ulcers are present.

"M. bovis" uses several different serotyped fimbriae as virulence factors, consequently pharmaceutical companies have exploited this to create vaccines. However, currently available vaccines are not reliable.

The majority of time treatment is symptomatic. Specific treatments are effective for bacterial, fungal, and herpes simplex infections.

The treatment includes lowering the increased intracranial pressure and starting intravenous antibiotics (and meanwhile identifying the causative organism mainly by blood culture studies).

Hyperbaric oxygen therapy (HBO2 or HBOT) is indicated as a primary and adjunct treatment which provides four primary functions.

Firstly, HBOT reduces intracranial pressure. Secondly, high partial pressures of oxygen act as a bactericide and thus inhibits the anaerobic and functionally anaerobic flora common in brain abscess. Third, HBOT optimizes the immune function thus enhancing the host defense mechanisms and fourth, HBOT has been found to be of benefit when brain abscess is concomitant with cranial osteomyleitis.

Secondary functions of HBOT include increased stem cell production and up-regulation of VEGF which aid in the healing and recovery process.

Surgical drainage of the abscess remains part of the standard management of bacterial brain abscesses. The location and treatment of the primary lesion also crucial, as is the removal of any foreign material (bone, dirt, bullets, and so forth).

There are few exceptions to this rule: "Haemophilus influenzae" meningitis is often associated with subdural effusions that are mistaken for subdural empyemas. These effusions resolve with antibiotics and require no surgical treatment. Tuberculosis can produce brain abscesses that look identical to conventional bacterial abscesses on CT imaging. Surgical drainage or aspiration is often necessary to identify "Mycobacterium tuberculosis", but once the diagnosis is made no further surgical intervention is necessary.

CT guided stereotactic aspiration is also indicated in the treatment of brain abscess.

Bats recovering from white-nose syndrome (WNS) may be the first natural occurrence of IRIS, in a report released by the USGS. WNS is typified by a cutaneous infection of the fungus "Pseudogymnoascus destructans" during hibernation, when the immune system is naturally suppressed to conserve energy through the winter. This study suggests that bats undergoing an intense inflammation at the site of infection after a return to euthermia is a form of IRIS.

To increase their effectiveness, vaccines should be administered as soon as possible after a dog enters a high-risk area, such as a shelter. 10 to 14 days are required for partial immunity to develop. Administration of B. bronchiseptica and canine-parainfluenza vaccines may then be continued routinely, especially during outbreaks of kennel cough. There are several methods of administration, including parenteral and intranasal. However, the intranasal method has been recommended when exposure is imminent, due to a more rapid and localized protection. Several intranasal vaccines have been developed that contain canine adenovirus in addition to B bronchiseptica and canine-parainfluenza virus antigens. Studies have thus far not been able to determine which formula of vaccination is the most efficient. Adverse effects of vaccinations are mild, but the most common effect observed up to 30 days after administration is nasal discharge. Vaccinations are not always effective. In one study it was found that 43.3% of all dogs in the study population with respiratory disease had in fact been vaccinated.