"S. pneumonia" can be treated with a combination of penicillin and ampicillin.

"L. meningitis" should be treated with a combination of ampicillin and gentamicin because it is synergistic in vitro and provides more rapid bacterial clearance in animal models of infection. After sterilization of CSF, ampicillin should be stopped and gentamicin continued for another 14 days.

Bacteremia should be treated for 2 weeks, meningitis for 3 weeks, and brain abscess for at least 6 weeks. Ampicillin generally is considered antibiotic of choice; gentamicin is added frequently for its synergistic effects. Overall mortality rate is 20–30%; of all pregnancy-related cases, 22% resulted in fetal loss or neonatal death, but mothers usually survive.

The main means of prevention is through the promotion of safe handling, cooking and consumption of food. This includes washing raw vegetables and cooking raw food thoroughly, as well as reheating leftover or ready-to-eat foods like hot dogs until steaming hot.

Another aspect of prevention is advising high-risk groups such as pregnant women and immunocompromised patients to avoid unpasteurized pâtés and foods such as soft cheeses like feta, Brie, Camembert cheese, and bleu. Cream cheeses, yogurt, and cottage cheese are considered safe. In the United Kingdom, advice along these lines from the Chief Medical Officer posted in maternity clinics led to a sharp decline in cases of listeriosis in pregnancy in the late 1980s.

Neonatal infection treatment is typically started before the diagnosis of the cause can be confirmed.

Neonatal infection can be prophylactically treated with antibiotics. Maternal treatment with antibiotics is primarily used to protect against group B streptococcus.

Women with a history of HSV, can be treated with antiviral drugs to prevent symptomatic lesions and viral shedding that could infect the infant at birth. The antiviral medications used include acyclovir, penciclovir, valacyclovir, and famciclovir. Only very small amounts of the drug can be detected in the fetus. There are no increases in drug-related abnormalities in the infant that could be attributed to acyclovir. Long-term effects of antiviral medications have not been evaluated for their effects after growth and development of the child occurs. Neutropenia can be a complication of acyclovir treatment of neonatal HSV infection, but is usually transient. Treatment with immunoglobulin therapy has not been proven to be effective.

Treatment of CAP in children depends on the child's age and the severity of illness. Children under five are not usually treated for atypical bacteria. If hospitalization is not required, a seven-day course of amoxicillin is often prescribed, with co-trimaxazole an alternative when there is allergy to penicillins. Further studies are needed to confirm the efficacy of newer antibiotics. With the increase in drug-resistant Streptococcus pneumoniae, antibiotics such as cefpodoxime may become more popular. Hospitalized children receive intravenous ampicillin, ceftriaxone or cefotaxime, and a recent study found that a three-day course of antibiotics seems sufficient for most mild-to-moderate CAP in children.

Most newborn infants with CAP are hospitalized, receiving IV ampicillin and gentamicin for at least ten days to treat the common causative agents "streptococcus agalactiae", "listeria monocytogenes" and "escherichia coli". To treat the herpes simplex virus, IV acyclovir is administered for 21 days.

To reduce neonatal infection, routine screening of pregnant women for HIV, hepatitis B, syphilis, and rubella susceptibility is required in the UK.

Treatment with an vaginal antibiotic wash prior to birth does not prevent infection with group B streptococcus bacteria. Breast milk protects against necrotizing enterocolitis.

Because GBS bacteria can colonize the lower reproductive tract of 30% of women, typically pregnant women are tested for this pathogen from 35 to 37 weeks of pregnancy. Before delivery treatment of the mother with antibiotics reduces the rate of neonatal infection. Prevention of the infection of the baby is done by treating the mother with penicillin. Since the adoption of this prophylatic treatment, infant mortality from GBS infection has decreased by 80%.

Mothers with symptomatic HSV and who are treated with antiviral prophylaxis are less prone to have an active, symptomatic case at the time of birth and it may be able to reduce the risk of passing on HSV during birth. Cesarean delivery reduces the risk of infection of the infant.

Viral meningitis typically only requires supportive therapy; most viruses responsible for causing meningitis are not amenable to specific treatment. Viral meningitis tends to run a more benign course than bacterial meningitis. Herpes simplex virus and varicella zoster virus may respond to treatment with antiviral drugs such as aciclovir, but there are no clinical trials that have specifically addressed whether this treatment is effective. Mild cases of viral meningitis can be treated at home with conservative measures such as fluid, bedrest, and analgesics.

Additional treatment with corticosteroids (usually dexamethasone) has shown some benefits, such as a reduction of hearing loss, and better short term neurological outcomes in adolescents and adults from high-income countries with low rates of HIV. Some research has found reduced rates of death while other research has not. They also appear to be beneficial in those with tuberculosis meningitis, at least in those who are HIV negative.

Professional guidelines therefore recommend the commencement of dexamethasone or a similar corticosteroid just before the first dose of antibiotics is given, and continued for four days. Given that most of the benefit of the treatment is confined to those with pneumococcal meningitis, some guidelines suggest that dexamethasone be discontinued if another cause for meningitis is identified. The likely mechanism is suppression of overactive inflammation.

Additional treatment with corticosteroids have a different role in children than in adults. Though the benefit of corticosteroids has been demonstrated in adults as well as in children from high-income countries, their use in children from low-income countries is not supported by the evidence; the reason for this discrepancy is not clear. Even in high-income countries, the benefit of corticosteroids is only seen when they are given prior to the first dose of antibiotics, and is greatest in cases of "H. influenzae" meningitis, the incidence of which has decreased dramatically since the introduction of the Hib vaccine. Thus, corticosteroids are recommended in the treatment of pediatric meningitis if the cause is "H. influenzae", and only if given prior to the first dose of antibiotics; other uses are controversial.

Note that, in neonates, sepsis is difficult to diagnose clinically. They may be relatively asymptomatic until hemodynamic and respiratory collapse is imminent, so, if there is even a remote suspicion of sepsis, they are frequently treated with antibiotics empirically until cultures are sufficiently proven to be negative. In addition to fluid resuscitation and supportive care, a common antibiotic regimen in infants with suspected sepsis is a beta-lactam antibiotic (usually ampicillin) in combination with an aminoglycoside (usually gentamicin) or a third-generation cephalosporin (usually cefotaxime—ceftriaxone is generally avoided in neonates due to the theoretical risk of kernicterus.) The organisms which are targeted are species that predominate in the female genitourinary tract and to which neonates are especially vulnerable to, specifically Group B Streptococcus, "Escherichia coli", and "Listeria monocytogenes" (This is the main rationale for using ampicillin versus other beta-lactams.) Of course, neonates are also vulnerable to other common pathogens that can cause meningitis and bacteremia such as "Streptococcus pneumoniae" and "Neisseria meningitidis". Although uncommon, if anaerobic species are suspected (such as in cases where necrotizing enterocolitis or intestinal perforation is a concern, clindamycin is often added.

Granulocyte-macrophage colony stimulating factor (GM-CSF) is sometimes used in neonatal sepsis. However, a 2009 study found that GM-CSF corrects neutropenia if present but it has no effect on reducing sepsis or improving survival.

Trials of probiotics for prevention of neonatal sepsis have generally been too small and statistically underpowered to detect any benefit, but a randomized controlled trial that enrolled 4,556 neonates in India reported that probiotics significantly reduced the risk of developing sepsis. The probiotic used in the trial was "Lactobacillus plantarum".

A very large meta-analysis investigated the effect of probiotics on preventing late-onset sepsis (LOS) in neonates. Probiotics were found to reduce the risk of LOS, but only in babies who were fed human milk exclusively. It is difficult to distinguish if the prevention was a result of the probiotic supplementation or if it was a result of the properties of human milk. It is also still unclear if probiotic administration reduces LOS risk in extremely low birth weight infants due to the limited number of studies that investigated it. Out of the 37 studies included in this systematic review, none indicated any safety problems related to the probiotics. It would be beneficial to clarify the relationship between probiotic supplementation and human milk for future studies in order to prevent late onset sepsis in neonates.

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.

Some vertically transmitted infections, such as toxoplasmosis and syphilis, can be effectively treated with antibiotics if the mother is diagnosed early in her pregnancy. Many viral vertically transmitted infections have no effective treatment, but some, notably rubella and varicella-zoster, can be prevented by vaccinating the mother prior to pregnancy.

If the mother has active herpes simplex (as may be suggested by a pap test), delivery by Caesarean section can prevent the newborn from contact, and consequent infection, with this virus.

IgG antibody may play crucial role in prevention of intrauterine infections and extensive research is going on for developing IgG-based therapies for treatment and vaccination.

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.

Each type of vertically transmitted infection has a different prognosis. The stage of the pregnancy at the time of infection also can change the effect on the newborn.

Methicillin-resistant Staphylococcus aureus (MRSA) evolved from Methicillin-susceptible Staphylococcus aureus (MSSA) otherwise known as common "S. aureus". Many people are natural carriers of "S. aureus", without being affected in any way. MSSA was treatable with the antibiotic methicillin until it acquired the gene for antibiotic resistance. Though genetic mapping of various strains of MRSA, scientists have found that MSSA acquired the mecA gene in the 1960s, which accounts for its pathogenicity, before this it had a predominantly commensal relationship with humans. It is theorized that when this "S. aureus" strain that had acquired the mecA gene was introduced into hospitals, it came into contact with other hospital bacteria that had already been exposed to high levels of antibiotics. When exposed to such high levels of antibiotics, the hospital bacteria suddenly found themselves in an environment that had a high level of selection for antibiotic resistance, and thus resistance to multiple antibiotics formed within these hospital populations. When "S. aureus" came into contact with these populations, the multiple genes that code for antibiotic resistance to different drugs were then acquired by MRSA, making it nearly impossible to control. It is thought that MSSA acquired the resistance gene through the horizontal gene transfer, a method in which genetic information can be passed within a generation, and spread rapidly through its own population as was illustrated in multiple studies. Horizontal gene transfer speeds the process of genetic transfer since there is no need to wait an entire generation time for gene to be passed on. Since most antibiotics do not work on MRSA, physicians have to turn to alternative methods based in Darwinian medicine. However prevention is the most preferred method of avoiding antibiotic resistance. By reducing unnecessary antibiotic use in human and animal populations, antibiotics resistance can be slowed.

The narrow range of treatable diseases or "spectrum of activity" of the penicillins, along with the poor activity of the orally active phenoxymethylpenicillin, led to the search for derivatives of penicillin that could treat a wider range of infections. The isolation of 6-APA, the nucleus of penicillin, allowed for the preparation of semisynthetic penicillins, with various improvements over benzylpenicillin (bioavailability, spectrum, stability, tolerance).

The first major development was ampicillin in 1961. It offered a broader spectrum of activity than either of the original penicillins. Further development yielded β-lactamase-resistant penicillins, including flucloxacillin, dicloxacillin, and methicillin. These were significant for their activity against β-lactamase-producing bacterial species, but were ineffective against the methicillin-resistant "Staphylococcus aureus" (MRSA) strains that subsequently emerged.

Another development of the line of true penicillins was the antipseudomonal penicillins, such as carbenicillin, ticarcillin, and piperacillin, useful for their activity against Gram-negative bacteria. However, the usefulness of the β-lactam ring was such that related antibiotics, including the mecillinams, the carbapenems and, most important, the cephalosporins, still retain it at the center of their structures.

Coopers Animal Health , a division of Schering-Plough, has released a new vaccine "Piliguard" in Australia. The vaccine contains three strains of "Morexella bovis" (SAH38, FLA 64, EPP 63) pilli antigen. This stimulate antibody production against the bacterial pilli to prevent their attachment and invasion of the conjuntiva. The company claims the vaccine reduces the incidence and severity of the disease in an individual animal which directly reduces animal suffering and production loss on top of limiting the spread of disease through the herd. This, in turn, reduces the amount of antibioitcs and fly repellent needed during high-risk seasons. The vaccine is marketed in multidose vials and has an adjuvant to create a long-term subcutaneous depot. This means no booster shot is necessary, but severe local reaction can be seen in people who accidentally inoculate themselves. Calves as young as one week old can be treated and no meat, milk, or export slaughter withdrawal is needed.

A study performed at Strong Memorial Hospital in Rochester, New York, showed that infants ≤ 60 days old meeting the following criteria were at low-risk for having a serious bacterial illness:

- generally well-appearing

- previously healthy

- full term (at ≥37 weeks gestation)

- no antibiotics perinatally

- no unexplained hyperbilirubinemia that required treatment

- no antibiotics since discharge

- no hospitalizations

- no chronic illness

- discharged at the same time or before the mother

- no evidence of skin, soft tissue, bone, joint, or ear infection

- White blood cells (WBCs) count 5,000-15,000/mm

- absolute band count ≤ 1,500/mm

- urine WBC count ≤ 10 per high power field (hpf)

- stool WBC count ≤ 5 per high power field (hpf) "only in infants with diarrhea"

Those meeting these criteria likely do not require a lumbar puncture, and are felt to be safe for discharge home without antibiotic treatment, or with a single dose of intramuscular antibiotics, but will still require close outpatient follow-up.

One risk for Group B streptococcal infection (GBS) is Preterm rupture of membranes. Screening women for GBS (via vaginal and rectal swabbing) and treating culture positive women with intrapartum chemoprophylaxis is reducing the number of neonatal sepsis caused by GBS.

While the number of penicillin-resistant bacteria is increasing, penicillin can still be used to treat a wide range of infections caused by certain susceptible bacteria, including Streptococci, Staphylococci, Clostridium, and Listeria genera. The following list illustrates minimum inhibitory concentration susceptibility data for a few medically significant bacteria:

- "Listeria monocytogenes": from less than or equal to 0.06 μg/ml to 0.25 μg/ml

- "Neisseria meningitidis": from less than or equal to 0.03 μg/ml to 0.5 μg/ml

- "Staphylococcus aureus": from less than or equal to 0.015 μg/ml to more than 32 μg/ml

An emerging infectious disease (EID) is an infectious disease whose incidence has increased in the past 20 years and could increase in the near future. Emerging infections account for at least 12% of all human pathogens. EIDs are caused by newly identified species or strains (e.g. Severe acute respiratory syndrome, HIV/AIDS) that may have evolved from a known infection (e.g. influenza) or spread to a new population (e.g. West Nile fever) or to an area undergoing ecologic transformation (e.g. Lyme disease), or be "reemerging" infections, like drug resistant tuberculosis. Nosocomial (hospital-acquired) infections, such as methicillin-resistant Staphylococcus aureus are emerging in hospitals, and extremely problematic in that they are resistant to many antibiotics. Of growing concern are adverse synergistic interactions between emerging diseases and other infectious and non-infectious conditions leading to the development of novel syndemics. Many emerging diseases are zoonotic - an animal reservoir incubates the organism, with only occasional transmission into human populations.

Fungi and parasites may also cause the disease. Fungi and parasites are especially associated with immunocompromised patients. Other causes include: "Nocardia asteroides", "Mycobacterium", Fungi (e.g. "Aspergillus", "Candida", "Cryptococcus", "Mucorales", "Coccidioides", "Histoplasma capsulatum", "Blastomyces dermatitidis", "Bipolaris", "Exophiala dermatitidis", "Curvularia pallescens", "Ochroconis gallopava", "Ramichloridium mackenziei", "Pseudallescheria boydii"), Protozoa (e.g. "Toxoplasma gondii", "Entamoeba histolytica", "Trypanosoma cruzi", "Schistosoma", "Paragonimus"), and Helminths (e.g. "Taenia solium"). Organisms that are most frequently associated with brain abscess in patients with AIDS are poliovirus, "Toxoplasma gondii", and "Cryptococcus neoformans", though in infection with the latter organism, symptoms of meningitis generally predominate.

These organisms are associated with certain predisposing conditions:

- Sinus and dental infections—Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (e.g. "Prevotella", "Porphyromonas", "Bacteroides"), "Fusobacterium", "S. aureus", and Enterobacteriaceae

- Penetrating trauma—"S. aureus", aerobic streptococci, Enterobacteriaceae, and "Clostridium" spp.

- Pulmonary infections—Aerobic and anaerobic streptococci, anaerobic gram-negative bacilli (e.g. "Prevotella", "Porphyromonas", "Bacteroides"), "Fusobacterium", "Actinomyces", and "Nocardia"

- Congenital heart disease—Aerobic and microaerophilic streptococci, and "S. aureus"

- HIV infection—"T. gondii", "Mycobacterium", "Nocardia", "Cryptococcus", and "Listeria monocytogenes"

- Transplantation—"Aspergillus", "Candida", "Cryptococcus", "Mucorales", "Nocardia", and "T. gondii"

- Neutropenia—Aerobic gram-negative bacilli, "Aspergillus", "Candida", and "Mucorales"

In sheep, the disease is also called the "circling disease". The most obvious signs for the veterinarians are neurological, especially lateral deviation of the neck and head.

Discontinuation of heparin is critical in a case of heparin-induced thrombocytopenia (HIT). Beyond that, however, clinicians generally treat to avoid a thrombosis, often by starting patients directly on warfarin. For this reason, patients are usually treated with a direct thrombin inhibitor, such as lepirudin or argatroban, which are approved by the FDA for this use. Other blood thinners sometimes used in this setting that are not FDA-approved for treatment of HIT include bivalirudin and fondaparinux. Platelet transfusions are not routinely used to treat HIT because thrombosis, not bleeding, is the primary problem.

Physicians often prescribe the antibiotic trimethoprim-sulfamethoxazole to prevent bacterial infections. This drug also has the benefit of sparing the normal bacteria of the digestive tract. Fungal infection is commonly prevented with itraconazole, although a newer drug of the same type called voriconazole may be more effective. The use of this drug for this purpose is still under scientific investigation.