The presence of bacteria in the blood almost always requires treatment with antibiotics. This is because there are high mortality rates from progression to sepsis if antibiotics are delayed.

The treatment of bacteremia should begin with empiric antibiotic coverage. Any patient presenting with signs or symptoms of bacteremia or a positive blood culture should be started on intravenous antibiotics. The choice of antibiotic is determined by the most likely source of infection and by the characteristic organisms that typically cause that infection. Other important considerations include the patient's past history of antibiotic use, the severity of the presenting symptoms, and any allergies to antibiotics. Empiric antibiotics should be narrowed, preferably to a single antibiotic, once the blood culture returns with a particular bacteria that has been isolated.

The Infectious Disease Society of America (IDSA) recommends treating uncomplicated methicillin resistant staph aureus (MRSA) bacteremia with a 14-day course of intravenous vancomycin. Uncomplicated bacteremia is defined as having positive blood cultures for MRSA, but having no evidence of endocarditis, no implanted prostheses, negative blood cultures after 2–4 days of treatment, and signs of clinical improvement after 72 hrs.

The antibiotic treatment of choice for streptococcal and enteroccal infections differs by species. However, it is important to look at the antibiotic resistance pattern for each species from the blood culture to better treat infections caused by resistant organisms.

Treatment for meningitis is antibiotics. The particular drugs used are based off the infecting bacteria, but a mix of ampicillin, gentamicin, and cefotaxime is used for early-onset meningitis before identification of infection. A regimen of antistaphylococcal antibiotic, such as nafcillin or vancomycin, plus cefotaxime or ceftazidime with or without an aminoglycoside is recommended for late-onset neonatal meningitis. The aim for these treatments is to sterilize the CSF of any meningitis-causing pathogens. A repeated LP 24–48 hours after initial treatment should be used to declare sterilization.

In cases of herpes simplex virus-derived meningitis, antiviral therapy (acyclovir or vidarabine) must be started immediately for a favorable outcome. Acyclovir is a better antiviral because it shows a similar effect on the infection as vidarabine and is safer to use in the neonate. The recommended dosage is 20 mg/kg every six hours for 21 days.

The treatment of TB meningitis is isoniazid, rifampicin, pyrazinamide and ethambutol for two months, followed by isoniazid and rifampicin alone for a further ten months. Steroids help reduce the risk of death in those without HIV. Steroids can be used in the first six weeks of treatment, A few people may require immunomodulatory agents such as thalidomide. Hydrocephalus occurs as a complication in about a third of people with TB meningitis. The addition of aspirin may reduce or delay mortality, possibly by reducing complications such as infarcts.

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.

Empiric antibiotics (treatment without exact diagnosis) should be started immediately, even before the results of the lumbar puncture and CSF analysis are known. The choice of initial treatment depends largely on the kind of bacteria that cause meningitis in a particular place and population. For instance, in the United Kingdom empirical treatment consists of a third-generation cefalosporin such as cefotaxime or ceftriaxone. In the USA, where resistance to cefalosporins is increasingly found in streptococci, addition of vancomycin to the initial treatment is recommended. Chloramphenicol, either alone or in combination with ampicillin, however, appears to work equally well.

Empirical therapy may be chosen on the basis of the person's age, whether the infection was preceded by a head injury, whether the person has undergone recent neurosurgery and whether or not a cerebral shunt is present. In young children and those over 50 years of age, as well as those who are immunocompromised, the addition of ampicillin is recommended to cover "Listeria monocytogenes". Once the Gram stain results become available, and the broad type of bacterial cause is known, it may be possible to change the antibiotics to those likely to deal with the presumed group of pathogens. The results of the CSF culture generally take longer to become available (24–48 hours). Once they do, empiric therapy may be switched to specific antibiotic therapy targeted to the specific causative organism and its sensitivities to antibiotics. For an antibiotic to be effective in meningitis it must not only be active against the pathogenic bacterium but also reach the meninges in adequate quantities; some antibiotics have inadequate penetrance and therefore have little use in meningitis. Most of the antibiotics used in meningitis have not been tested directly on people with meningitis in clinical trials. Rather, the relevant knowledge has mostly derived from laboratory studies in rabbits. Tuberculous meningitis requires prolonged treatment with antibiotics. While tuberculosis of the lungs is typically treated for six months, those with tuberculous meningitis are typically treated for a year or longer.

Recovery from an anaerobic infection depends on adequate and rapid management. The main principles of managing anaerobic infections are neutralizing the toxins produced by anaerobic bacteria, preventing the local proliferation of these organisms by altering the environment and preventing their dissemination and spread to healthy tissues.

Toxin can be neutralized by specific antitoxins, mainly in infections caused by Clostridia (tetanus and botulism). Controlling the environment can be attained by draining the pus, surgical debriding of necrotic tissue, improving blood circulation, alleviating any obstruction and by improving tissue oxygenation. Therapy with hyperbaric oxygen (HBO) may also be useful. The main goal of antimicrobials is in restricting the local and systemic spread of the microorganisms.

The available parenteral antimicrobials for most infections are metronidazole, clindamycin, chloramphenicol, cefoxitin, a penicillin (i.e. ticarcillin, ampicillin, piperacillin) and a beta-lactamase inhibitor (i.e. clavulanic acid, sulbactam, tazobactam), and a carbapenem (imipenem, meropenem, doripenem, ertapenem). An antimicrobial effective against Gram-negative enteric bacilli (i.e. aminoglycoside) or an anti-pseudomonal cephalosporin (i.e. cefepime ) are generally added to metronidazole, and occasionally cefoxitin when treating intra-abdominal infections to provide coverage for these organisms. Clindamycin should not be used as a single agent as empiric therapy for abdominal infections. Penicillin can be added to metronidazole in treating of intracranial, pulmonary and dental infections to provide coverage against microaerophilic streptococci, and Actinomyces.

Oral agents adequate for polymicrobial oral infections include the combinations of amoxicillin plus clavulanate, clindamycin and metronidazole plus a macrolide. Penicillin can be added to metronidazole in the treating dental and intracranial infections to cover "Actinomyces" spp., microaerophilic streptococci, and "Arachnia" spp. A macrolide can be added to metronidazole in treating upper respiratory infections to cover "S. aureus" and aerobic streptococci. Penicillin can be added to clindamycin to supplement its coverage against "Peptostreptococcus" spp. and other Gram-positive anaerobic organisms.

Doxycycline is added to most regimens in the treatment of pelvic infections to cover chlamydia and mycoplasma. Penicillin is effective for bacteremia caused by non-beta lactamase producing bacteria. However, other agents should be used for the therapy of bacteremia caused by beta-lactamase producing bacteria.

Because the length of therapy for anaerobic infections is generally longer than for infections due to aerobic and facultative anaerobic bacteria, oral therapy is often substituted for parenteral treatment. The agents available for oral therapy are limited and include amoxacillin plus clavulanate, clindamycin, chloramphenicol and metronidazole.

In 2010 the American Surgical Society and American Society of Infectious Diseases have updated their guidelines for the treatment of abdominal infections.

The recommendations suggest the following:

For mild-to-moderate community-acquired infections in adults, the agents recommended for empiric regimens are: ticarcillin- clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single-agent therapy or combinations of metronidazole with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin. Agents no longer recommended are: cefotetan and clindamycin ( Bacteroides fragilis group resistance) and ampicillin-sulbactam (E. coli resistance) and ainoglycosides (toxicity).

For high risk community-acquired infections in adults, the agents recommended for empiric regimens are: meropenem, imipenem-cilastatin, doripenem, piperacillin-tazobactam, ciprofloxacin or levofloxacin in combination with metronidazole, or ceftazidime or cefepime in combination with metronidazole. Quinolones should not be used unless hospital surveys indicate >90% susceptibility of "E. coli" to quinolones.

Aztreonam plus metronidazole is an alternative, but addition of an agent effective against gram-positive cocci is recommended. The routine use of an aminoglycoside or another second agent effective against gram-negative facultative and aerobic bacilli is not recommended in the absence of evidence that the infection is caused by resistant organisms that require such therapy.

Empiric use of agents effective against enterococci is recommended and agents effective against methicillin-resistant "S. aureus" (MRSA) or yeast is not recommended in the absence of evidence of infection due to such organisms.

Empiric antibiotic therapy for health care-associated intra-abdominal should be driven by local microbiologic results. Empiric coverage of likely pathogens may require multidrug regimens that include agents with expanded spectra of activity against gram-negative aerobic and facultative bacilli. These include meropenem, imipenem-cilastatin, doripenem, piperacillin-tazobactam, or ceftazidime or cefepime in combination with metronidazole. Aminoglycosides or colistin may be required.

Antimicrobial regimens for children include an aminoglycoside-based regimen, a carbapenem (imipenem, meropenem, or ertapenem), a beta-lactam/beta-lactamase-inhibitor combination (piperacillin-tazobactam or ticarcillin-clavulanate), or an advanced-generation cephalosporin (cefotaxime, ceftriaxone, ceftazidime, or cefepime) with metronidazole.

Clinical judgment, personal experience, safety and patient compliance should direct the physician in the choice of the appropriate antimicrobial agents. The length of therapy generally ranges between 2 and 4 weeks, but should be individualized depending on the response. In some instances treatment may be required for as long as 6–8 weeks, but can often be shortened with proper surgical drainage.

Antibiotics are the treatment of choice for bacterial pneumonia, with ventilation (oxygen supplement) as supportive therapy. The antibiotic choice depends on the nature of the pneumonia, the microorganisms most commonly causing pneumonia in the geographical region, and the immune status and underlying health of the individual. In the United Kingdom, amoxicillin is used as first-line therapy in the vast majority of patients acquiring pneumonia in the community, sometimes with added clarithromycin. In North America, where the "atypical" forms of community-acquired pneumonia are becoming more common, clarithromycin, azithromycin, or fluoroquinolones as single therapy have displaced the amoxicillin as first-line therapy.

Local patterns of antibiotic-resistance always need to be considered when initiating pharmacotherapy. In hospitalized individuals or those with immune deficiencies, local guidelines determine the selection of antibiotics.

"Streptococcus pneumoniae" — amoxicillin (or erythromycin in patients allergic to penicillin); cefuroxime and erythromycin in severe cases.

"Staphylococcus aureus" — flucloxacillin (to counteract the organism's β-lactamase).

Fungal meningitis is treated with long courses of high dose antifungal medications. The duration of treatment is dependent upon the causal pathogen and the patient's ability to stave off the infection; for patients with a weaker immune system or diabetes, treatment will often take longer.

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.

Usually initial therapy is empirical. If sufficient reason to suspect influenza, one might consider oseltamivir. In case of legionellosis, erythromycin or fluoroquinolone.

A third generation cephalosporin (ceftazidime) + carbapenems (imipenem) + beta lactam & beta lactamase inhibitors (piperacillin/tazobactam)

When meningococcal disease is suspected, treatment must be started "immediately" and should not be delayed while waiting for investigations. Treatment in primary care usually involves prompt intramuscular administration of benzylpenicillin, and then an urgent transfer to hospital (hopefully, an academic level I medical center, or at least a hospital with round the clock neurological care, ideally with neurological intensive and critical care units) for further care. Once in the hospital, the antibiotics of choice are usually IV broad spectrum 3rd generation cephalosporins, e.g., cefotaxime or ceftriaxone. Benzylpenicillin and chloramphenicol are also effective. Supportive measures include IV fluids, oxygen, inotropic support, e.g., dopamine or dobutamine and management of raised intracranial pressure. Steroid therapy may help in some adult patients, but is unlikely to affect long term outcomes.

Complications following meningococcal disease can be divided into early and late groups. Early complications include: raised intracranial pressure, disseminated intravascular coagulation, seizures, circulatory collapse and organ failure. Later complications are: deafness, blindness, lasting neurological deficits, reduced IQ, and gangrene leading to amputations.

Treatment consists of antibiotic therapy aimed at the typical bacterial pathogens in addition to supportive care for any complications which might result from the infection itself such as hypotension or respiratory failure. A typical regimen will include intravenous antibiotics such as from the penicillin-group which is active against "Staphylococcus aureus" and an aminoglycoside for activity against Gram-negative bacteria. For particularly invasive infections, antibiotics to cover anaerobic bacteria may be added (such as metronidazole). Treatment is typically for two weeks and often necessitates insertion of a central venous catheter or peripherally inserted central catheter.

Symptomatic bacteriuria is typically treated as a urinary tract infection with antibiotics. Common choices include nitrofurantoin, and trimethoprim/sulfamethoxazole.

Because it is a bacterial disease, the primary method of treatment for "Haemophilus" meningitis is anti-bacterial therapy. Common antibiotics include ceftriaxone or cefotaxime, both of which can combat the infection and thus reduce inflammation in the meninges, or the membranes that protect the brain and spinal cord. Anti-inflammatories such as corticosteroids, or steroids produced by the body to reduce inflammation, can also be used to fight the meningeal inflammation in an attempt to reduce risk of mortality and reduce the possibility of brain damage.

Asymptomatic bacteriuria generally does not require treatment. Exceptions include during pregnancy and in those undergoing surgery of the urinary tract. Children with vesicoureteral reflux or others with structural abnormalities of the urinary tract.

There is no indication to treat asymptomatic bacteriuria in diabetics, renal transplant recipients, and in those with spinal cord injuries.

The overuse of antibiotic therapy to treat asymptomatic bacteriuria increases the risk of diarrhea, antimicrobial resistance, and infection due to Clostridium difficile. Other effects include increased financial burdens and overreporting of mandated catheter-associated urinary tract infection.

Alternatives to fosfomycin include nitrofurantoin, pivmecillinam, and co-amoxiclav in oral treatment of urinary-tract infections associated with extended-spectrum beta-lactamase.

In a separate study, CRE were treated with colistin, amikacin, and tigecycline, and emphasizes the importance of using gentamicin in patients undergoing chemotherapy or stem-cell therapy procedures.

While colistin had shown promising activity against carbapenemase-producing isolates, more recent data suggest a resistance to it is already emerging and it will soon become ineffective.

Using another antibiotic concomitantly with carbapenem can help prevent the development of carbapenem resistance. One specific study showed a higher rate of carbapenem resistance when using meropenem alone compared with combination therapy with moxifloxacin.

In addition, several drugs were tested to gauge their effectiveness against CRE infections. "In vitro" studies have shown that rifampin has synergistic activity against carbapenem-resistant "E. coli" and "K. pneumoniae". However, more data are needed to determine if rifampin is effective in a clinical setting.

Several new agents are in development. The main areas where scientists are focusing is new β-lactamase inhibitors with activity against carbapenemases. Some of these include MK-7655, NXL104, and 6-alkylidenepenam sulfones. The exact way they affect the carbapenemases is unknown. Another experimental agent with activity against CRE is eravacycline.

Patients with HCAP are more likely than those with community-acquired pneumonia to receive inappropriate antibiotics that do not target the bacteria causing their disease.

In 2002, an expert panel made recommendations about the evaluation and treatment of probable nursing home-acquired pneumonia. They defined probably pneumonia, emphasized expedite antibiotic treatment (which is known to improve survival) and drafted criteria for the hospitalization of willing patients.

For initial treatment in the nursing home, a fluoroquinolone antibiotic suitable for respiratory infections (moxifloxacin, for example), or amoxicillin with clavulanic acid plus a macrolide has been suggested. In a hospital setting, injected (parenteral) fluoroquinolones or a second- or third-generation cephalosporin plus a macrolide could be used. Other factors that need to be taken into account are recent antibiotic therapy (because of possible resistance caused by recent exposure), known carrier state or risk factors for resistant organisms (for example, known carrier of MRSA or presence of bronchiectasis predisposing to Pseudomonas aeruginosa), or suspicion of possible Legionella pneumophila infection (legionnaires disease).

In 2005, the American Thoracic Society and Infectious Diseases Society of America have published guidelines suggesting antibiotics specifically for HCAP. The guidelines recommend combination therapy with an agent from each of the following groups to cover for both "Pseudomonas aeruginosa" and MRSA. This is based on studies using sputum samples and intensive care patients, in whom these bacteria were commonly found.

- cefepime, ceftazidime, imipenem, meropenem or piperacillin–tazobactam; plus

- ciprofloxacin, levofloxacin, amikacin, gentamicin, or tobramycin; plus

- linezolid or vancomycin

In one observational study, empirical antibiotic treatment that was not according to international treatment guidelines was an independent predictor of worse outcome among HCAP patients.

Guidelines from Canada suggest that HCAP can be treated like community-acquired pneumonia with antibiotics targeting Streptococcus pneumoniae, based on studies using blood cultures in different settings which have not found high rates of MRSA or Pseudomonas.

Besides prompt antibiotic treatment, supportive measure for organ failure (such as cardiac decompensation) are also important. Another consideration goes to hospital referral; although more severe pneumonia requires admission to an acute care facility, this also predisposes to hazards of hospitalization such as delirium, urinary incontinence, depression, falls, restraint use, functional decline, adverse drug effects and hospital infections. Therefore, mild pneumonia might be better dealt with inside the long term care facility. In patients with a limited life expectancy (for example, those with advanced dementia), end-of-life pneumonia also requires recognition and appropriate, palliative care.

Tigecycline, a member of the glycylcyclines antibiotics, has proven to be an effective therapy against Enterobacteriaceae that typically display tetracycline resistance, because tigecycline has a higher binding affinity with ribosomal sites than tetracycline has. Tigecycline is capable of killing almost all of the ESBLs and multidrug-resistant (MDR) "E. coli" isolates and the large majority of ESBL and MDR isolates of "Klebsiella" species.

A 2008 review of 42 studies of "in vitro" susceptibility of bacteria to tigecycline showed that MDR "K. pneumoniae" and "E. coli", including those that were carbapenem resistant, were susceptible more than 90% of the time. A limited number of patients have been treated with tigecycline, but the FDA has approved it in certain cases with synergies of other drugs. The limited number of patients indicates that more trials are needed to determine the overall clinical effectiveness.

Although tigecycline is the one of the first lines of defense against carbapenemase-producing isolates, negative clinical outcomes with tigecycline have occurred. Both urinary tract and primary blood infections can make tigecycline ineffective, because it has limited penetration and rapid tissue diffusion after being intravenously infused, respectively.

In people suspected of having pyelonephritis, a urine culture and antibiotic sensitivity test is performed, so therapy can eventually be tailored on the basis of the infecting organism. As most cases of pyelonephritis are due to bacterial infections, antibiotics are the mainstay of treatment. The choice of antibiotic depends on the species and antibiotic sensitivity profile of the infecting organism, and may include fluoroquinolones, cephalosporins, aminoglycosides, or trimethoprim/sulfamethoxazole, either alone or in combination.

In people who do not require hospitalization and live in an area where there is a low prevalence of antibiotic-resistant bacteria, an fluoroquinolone by mouth such as ciprofloxacin or levofloxacin is an appropriate initial choice for therapy. In areas where there is a higher prevalence of fluoroquinolone resistance, it is useful to initiate treatment with a single intravenous dose of a long-acting antibiotic such as ceftriaxone or an aminoglycoside, and then continuing treatment with a fluoroquinolone. Oral trimethoprim/sulfamethoxazole is an appropriate choice for therapy if the bacteria is known to be susceptible. If trimethoprim/sulfamethoxazole is used when the susceptibility is not known, it is useful to initiate treatment with a single intravenous dose of a long-acting antibiotic such as ceftriaxone or an aminoglycoside. Oral beta-lactam antibiotics are less effective than other available agents for treatment of pyelonephritis. Improvement is expected in 48 to 72 hours.

During the 1950s there were outbreaks of omphalitis that then led to anti-bacterial treatment of the umbilical cord stump as the new standard of care. It was later determined that in developed countries keeping the cord dry is sufficient, (known as "dry cord care") as recommended by the American Academy of Pediatrics. The umbilical cord dries more quickly and separates more readily when exposed to air However, each hospital/birthing center has its own recommendations for care of the umbilical cord after delivery. Some recommend not using any medicinal washes on the cord. Other popular recommendations include triple dye, betadine, bacitracin, or silver sulfadiazine. With regards to the medicinal treatments, there is little data to support any one treatment (or lack thereof) over another. However one recent review of many studies supported the use of chlorhexidine treatment as a way to reduce risk of death by 23% and risk of omphalitis by anywhere between 27-56% in community settings in underdeveloped countries. This study also found that this treatment increased the time that it would take for the umbilical stump to separate or fall off by 1.7 days. Lastly this large review also supported the notion that in hospital settings no medicinal type of cord care treatment was better at reducing infections compared to dry cord care.