The decision to treat bacteriuria depends on the presence of accompany symptoms and comorbidities.

Testing for bacteriuria is often performed in those with symptoms of a urinary tract infection. Testing is often done in other scenarios as in failure to thrive of a newborn or confusion in the elderly. Screening for bacteriuria is recommended in pregnancy as there is evidence that asymptomatic bacteriuria can lead to low birth weight and preterm delivery.

- Bacteriuria can be detected by urine dipstick test. The urinary nitrite test will be able to detect any nitrate-reducing bacteria in the urine. The leukocyte esterase test detects the presence of leukocytes (white blood cells) in the urine which can be associated with a urinary tract infection.The urine dipstick test is readily available and provides fast results.

- Microscopy can also be used to detect bacteriuria. It is more specific, especially when used with gram staining, but requires more time and equipment.

- The gold standard for detecting bacteriuria is a bacterial culture which identifies the actual organism. This test is more specific but can take several days to obtain a result. As a result, clinicians will often treat a bacteriuria based on the results of the urine dipstick test while waiting for the culture results. The culture will often provide antibiotic sensitivity.

Bacteriuria can be confirmed if a single bacterial species is isolated in a concentration greater than 100,000 colony forming units per millilitre of urine in clean-catch midstream urine specimens (one for men, two consecutive specimens with the same bacterium for women). For urine collected via bladder catheterization in men and women, a single urine specimen with greater than 100,000 colony forming units of a single species per millilitre is considered diagnostic. The threshold is also 100 colony forming units of a single species per millilitre for women displaying UTI symptoms.

Early diagnosis is necessary to properly manage sepsis, as initiation of rapid therapy is key to reducing deaths from severe sepsis.

Within the first three hours of suspected sepsis, diagnostic studies should include white blood cell counts, measuring serum lactate, and obtaining appropriate cultures before starting antibiotics, so long as this does not delay their use by more than 45 minutes. To identify the causative organism(s), at least two sets of blood cultures using bottles with media for aerobic and anaerobic organisms should be obtained, with at least one drawn through the skin and one drawn through each vascular access device (such as an IV catheter) in place more than 48 hours. Bacteria are present in the blood in only about 30% of cases. Another possible method of detection is by polymerase chain reaction. If other sources of infection are suspected, cultures of these sources, such as urine, cerebrospinal fluid, wounds, or respiratory secretions, also should be obtained, as long as this does not delay the use of antibiotics.

Within six hours, if blood pressure remains low despite initial fluid resuscitation of 30 ml/kg, or if initial lactate is ≥ 4 mmol/l (36 mg/dl), central venous pressure and central venous oxygen saturation should be measured. Lactate should be re-measured if the initial lactate was elevated. Within twelve hours, it is essential to diagnose or exclude any source of infection that would require emergent source control, such as necrotizing soft tissue infection, infection causing inflammation of the abdominal cavity lining, infection of the bile duct, or intestinal infarction. A pierced internal organ (free air on abdominal x-ray or CT scan), an abnormal chest x-ray consistent with pneumonia (with focal opacification), or petechiae, purpura, or purpura fulminans may be evident of infection.

A 2013 review concluded moderate-quality evidence exists to support use of the procalcitonin level as a method to distinguish sepsis from non-infectious causes of SIRS. The same review found the sensitivity of the test to be 77% and the specificity to be 79%. The authors suggested that procalcitonin may serve as a helpful diagnostic marker for sepsis, but cautioned that its level alone cannot definitively make the diagnosis. A 2012 systematic review found that soluble urokinase-type plasminogen activator receptor (SuPAR) is a nonspecific marker of inflammation and does not accurately diagnose sepsis. This same review concluded, however, that SuPAR has prognostic value, as higher SuPAR levels are associated with an increased rate of death in those with sepsis.

Bacteremia is most commonly diagnosed by blood culture, in which a sample of blood drawn from the vein by needle puncture is allowed to incubate with a medium that promotes bacterial growth. If bacteria are present in the bloodstream at the time the sample is obtained, the bacteria will multiply and can thereby be detected.

Any bacteria that incidentally find their way to the culture medium will also multiply. For example, if the skin is not adequately cleaned before needle puncture, contamination of the blood sample with normal bacteria that live on the surface of the skin can occur. For this reason, blood cultures must be drawn with great attention to sterile process. The presence of certain bacteria in the blood culture, such as S"taphylococcus aureus", "Streptococcus pneumoniae", and "Escherichia coli" almost never represent a contamination of the sample. On the other hand, contamination may be more highly suspected if organisms like "Staphylococcus epidermidis" or "Propionibacterium acnes" grow in the blood culture.

Two blood cultures drawn from separate sites of the body are often sufficient to diagnose bacteremia. Two out of two cultures growing the same type of bacteria usually represents a real bacteremia, particularly if the organism that grows is not a common contaminant. One out of two positive cultures will usually prompt a repeat set of blood cultures to be drawn to confirm whether a contaminant or a real bacteremia is present. The patient's skin is typically cleaned with an alcohol-based product prior to drawing blood to prevent contamination. Blood cultures may be repeated at intervals to determine if persistent — rather than transient — bacteremia is present.

Prior to drawing blood cultures, a thorough patient history should be taken with particular regard to presence of both fevers and chills, other focal signs of infection such as in the skin or soft tissue, a state of immunosuppression, or any recent invasive procedures.

Ultrasound of the heart is recommended in all those with bacteremia due to "Staphylococcus aureus" to rule out infectious endocarditis.

Analysis of the urine may show signs of urinary tract infection. Specifically, the presence of nitrite and white blood cells on a urine test strip in patients with typical symptoms are sufficient for the diagnosis of pyelonephritis, and are an indication for empirical treatment. Blood tests such as a complete blood count may show neutrophilia. Microbiological culture of the urine, with or without blood cultures and antibiotic sensitivity testing are useful for establishing a formal diagnosis, and are considered mandatory.

If a kidney stone is suspected (e.g. on the basis of characteristic colicky pain or the presence of a disproportionate amount of blood in the urine), a kidneys, ureters, and bladder x-ray (KUB film) may assist in identifying radioopaque stones. Where available, a noncontrast helical CT scan with 5 millimeter sections is the diagnostic modality of choice in the radiographic evaluation of suspected nephrolithiasis. All stones are detectable on CT scans except very rare stones composed of certain drug residues in the urine. In patients with recurrent ascending urinary tract infections, it may be necessary to exclude an anatomical abnormality, such as vesicoureteral reflux or polycystic kidney disease. Investigations used in this setting include kidney ultrasonography or voiding cystourethrography. CT scan or kidney ultrasonography is useful in the diagnosis of xanthogranulomatous pyelonephritis; serial imaging may be useful for differentiating this condition from kidney cancer.

Ultrasound findings that indicate pyelonephritis are enlargement of the kidney, edema in the renal sinus or parenchyma, bleeding, loss of corticomedullary differentiation, abscess formation, or an areas of poor blood flow on doppler ultrasound. However, ultrasound findings are seen in only 20% to 24% of people with pyelonephritis.

A DMSA scan is a radionuclide scan that uses dimercaptosuccinic acid in assessing the kidney morphology. It is now the most reliable test for the diagnosis of acute pyelonephritis.

For healthcare-associated bacteremia due to intravenous catheters, the IDSA has published guidelines for catheter removal. Short term catheters (in place 14 days) should be removed if the patient is developing signs or symptoms of sepsis or endocarditis, or if blood cultures remain positive for more than 72 hours.

To make the diagnosis of a urinary tract infection in children, a positive urinary culture is required. Contamination poses a frequent challenge depending on the method of collection used, thus a cutoff of 10 CFU/mL is used for a "clean-catch" mid stream sample, 10 CFU/mL is used for catheter-obtained specimens, and 10 CFU/mL is used for suprapubic aspirations (a sample drawn directly from the bladder with a needle). The use of "urine bags" to collect samples is discouraged by the World Health Organization due to the high rate of contamination when cultured, and catheterization is preferred in those not toilet trained. Some, such as the American Academy of Pediatrics recommends renal ultrasound and voiding cystourethrogram (watching a person's urethra and urinary bladder with real time x-rays while they urinate) in all children less than two years old who have had a urinary tract infection. However, because there is a lack of effective treatment if problems are found, others such as the National Institute for Health and Care Excellence only recommends routine imaging in those less than six months old or who have unusual findings.

Diagnosis and the imaging (and laboratory) studies to be ordered largely depend on the patient history, signs and symptoms. If a persistent sore throat with signs of sepsis are found, physicians are cautioned to screen for Lemierre's syndrome.

Laboratory investigations reveal signs of a bacterial infection with elevated C-reactive protein, erythrocyte sedimentation rate and white blood cells (notably neutrophils). Platelet count can be low or high. Liver and kidney function tests are often abnormal.

Thrombosis of the internal jugular vein can be displayed with sonography. Thrombi that have developed recently have low echogenicity or echogenicity similar to the flowing blood, and in such cases pressure with the ultrasound probe show a non-compressible jugular vein - a sure sign of thrombosis. Also color or power Doppler ultrasound identify a low echogenicity blood clot. A CT scan or an MRI scan is more sensitive in displaying the thrombus of the intra-thoracic retrosternal veins, but are rarely needed.

Chest X-ray and chest CT may show pleural effusion, nodules, infiltrates, abscesses and cavitations.

Bacterial cultures taken from the blood, joint aspirates or other sites can identify the causative agent of the disease.

Other illnesses that can be included in the differential diagnosis are:

- Q fever

- Tuberculosis

- Pneumonia

In straightforward cases, a diagnosis may be made and treatment given based on symptoms alone without further laboratory confirmation. In complicated or questionable cases, it may be useful to confirm the diagnosis via urinalysis, looking for the presence of urinary nitrites, white blood cells (leukocytes), or leukocyte esterase. Another test, urine microscopy, looks for the presence of red blood cells, white blood cells, or bacteria. Urine culture is deemed positive if it shows a bacterial colony count of greater than or equal to 10 colony-forming units per mL of a typical urinary tract organism. Antibiotic sensitivity can also be tested with these cultures, making them useful in the selection of antibiotic treatment. However, women with negative cultures may still improve with antibiotic treatment. As symptoms can be vague and without reliable tests for urinary tract infections, diagnosis can be difficult in the elderly.

Due to the atypical presentation and rarity of the infection, it takes a physician longer to diagnose than more common types of bladder infections. Diagnosis requires a personalized investigation with consideration to risk factors and symptoms (Bobba). Radiology of the abdominal or pubic region has proven to be an important tool in reaching a definitive diagnosis of conditions causing gas in the urinary tract. Computer tomography, or CT scans, are of most help due to their high sensitivity in detecting gas and air bubbles (Gheonea, Bondari). However, radiology is normally not the first tool used to diagnose. Most diagnoses are made by chance after imaging examination (Weerakkody). Sometimes, even when patients don’t show symptoms, their Emphysematous cystitis infection level can be very advanced already (De Baets, Baert). Gas in the bladder wall will often have the appearance of cobblestone or a “beaded necklace” with the use of conventional radiography (Weerakkody). Delayed diagnosis can lead to a severe infection, extension of the uterus, rupturing of the bladder, and death. Emphysematous cystitis has an overall mortality rate of 7%. However, surgery is only considered in severe cases where the disease progresses involving the ureters, kidneys, or adrenal glands. When required, surgery may be extensive. (De Baets, Baert).

Neonatal sepsis screening:

1. DLC (differential leukocyte count) showing increased numbers of polymorphs.

2. DLC: band cells > 20%.

3. increased haptoglobins.

4. micro ESR (Erythrocyte Sedimentation Rate) titer > 15mm.

5. gastric aspirate showing > 5 polymorphs per high power field.

6. newborn CSF (Cerebrospinal fluid) screen: showing increased cells and proteins.

7. suggestive history of chorioamnionitis, PROM (Premature rupture of membranes), etc...

Culturing for microorganisms from a sample of CSF, blood or urine, is the gold standard test for definitive diagnosis of neonatal sepsis. This can give false negatives due to the low sensitivity of culture methods and because of concomitant antibiotic therapy. Lumbar punctures should be done when possible as 10-15% presenting with sepsis also have meningitis, which warrants an antibiotic with a high CSF penetration.

CRP is not very accurate in picking up cases.

Sepsis has a worldwide incidence of more than 20 million cases a year, with mortality due to septic shock reaching up to 50 percent even in industrialized countries.

According to the U.S. Centers for Disease Control, septic shock is the thirteenth leading cause of death in the United States and the most frequent cause of deaths in intensive care units. There has been an increase in the rate of septic shock deaths in recent decades, which is attributed to an increase in invasive medical devices and procedures, increases in immunocompromised patients, and an overall increase in elderly patients.

Tertiary care centers (such as hospice care facilities) have 2-4 times the rate of bacteremia than primary care centers, 75% of which are hospital-acquired infections.

The process of infection by bacteria or fungi may result in systemic signs and symptoms that are variously described. Approximately 70% of septic shock cases were once traceable to gram-negative bacteria that produce endotoxins, however, with the emergence of MRSA and the increased use of arterial and venous catheters, gram-positive bacteria are implicated approximately as commonly as bacilli. In rough order of increasing severity these are, bacteremia or fungemia; sepsis, severe sepsis or sepsis syndrome; septic shock, refractory septic shock, multiple organ dysfunction syndrome, and death.

35% of septic shock cases derive from urinary tract infections, 15% from the respiratory tract, 15% from skin catheters (such as IVs), and more than 30% of all cases are idiopathic in origin.

The mortality rate from sepsis is approximately 40% in adults and 25% in children. It is significantly greater when sepsis is left untreated for more than seven days.

While there is tentative evidence for β-Blocker therapy to help control heart rate, evidence is not significant enough for its routine use. There is tentative evidence that steroids may be useful in improving outcomes.

Tentative evidence exists that Polymyxin B-immobilized fiber column hemoperfusion may be beneficial in treatment of septic shock. Trials are ongoing and it is currently being used in Japan and Western Europe.

Recombinant activated protein C (drotrecogin alpha) in a 2011 Cochrane review was found not to decrease mortality and to increase bleeding, and thus, was not recommended for use. Drotrecogin alfa (Xigris), was withdrawn from the market in October 2011.

Urinary catheters should be inserted using aseptic technique and sterile equipment (including sterile gloves, drape, sponges, antiseptic and sterile solution), particularly in an acute care setting. Hands should be washed before and after catheter insertion. Overall, catheter use should be minimized in all patients, particularly those at higher risk of CAUTI and mortality (e.g. the elderly or those with impaired immunity).

Acute prostatitis is relatively easy to diagnose due to its symptoms that suggest infection. The organism may be found in blood or urine, and sometimes in both. Common bacteria are "Escherichia coli, Klebsiella, Proteus, Pseudomonas, Enterobacter, Enterococcus, Serratia," and "Staphylococcus aureus." This can be a medical emergency in some patients and hospitalization with intravenous antibiotics may be required. A complete blood count reveals increased white blood cells. Sepsis from prostatitis is very rare, but may occur in immunocompromised patients; high fever and malaise generally prompt blood cultures, which are often positive in sepsis. A prostate massage should never be done in a patient with suspected acute prostatitis, since it may induce sepsis. Since bacteria causing the prostatitis is easily recoverable from the urine, prostate massage is not required to make the diagnosis. Rectal palpation usually reveals an enlarged, exquisitely tender, swollen prostate gland, which is firm, warm, and, occasionally, irregular to the touch. C-reactive protein is elevated in most cases.

Prostate biopsies are not indicated as the (clinical) features (described above) are diagnostic. The histologic correlate of acute prostatitis is a neutrophilic infiltration of the prostate gland.

Acute prostatitis is associated with a transiently elevated PSA, i.e., the PSA is increased during an episode of acute prostatitis and then decreases again after it has resolved. PSA testing is not indicated in the context of uncomplicated acute prostatitis.

When properly diagnosed, the mortality of Lemierre's syndrome is about 4.6%. Since this disease is not well known and often remains undiagnosed, mortality might be much higher.

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.

Even when caught early, aggressive treatment is required (Bobba). Antibiotics are proven to cure Emphysematous cystitis over time and reduce the amount of gas inside the bladder wall. Prognosis is poor if antibiotics are not used to treat the patient. Additional treatment consists of urinary drainage and good control of blood glucose. The treatment of underlying comorbid diseases, such as diabetes, is extremely important because they can intensify the infection (Gheonea, Bondari). Hyperbaric oxygen is an effective treatment, and has cured some cases in as little as 48 hours. Although it is unclear as to how gas formation occurs in emphysematous cystitis, it’s dependant on whether or not the patient has contributing diseases (Mccabe). Gas formation in diabetic patients diagnosed with Emphysematous cystitis has been determined to occur due to the production of carbon dioxide as a result of the fermentation of the high concentrations of glucose. Gas formation in nondiabetic patients is most likely due the breaking down of urinary lactulose and tissue proteins. Inflammation caused by infection increases pressure and decreases circulation, which provides the perfect environment for bacteria to produce gas (Sereno).

Antibiotics are the first line of treatment in acute prostatitis. Antibiotics usually resolve acute prostatitis infections in a very short time, however a minimum of two to four weeks of therapy is recommended to eradicate the offending organism completely. Appropriate antibiotics should be used, based on the microbe causing the infection. Some antibiotics have very poor penetration of the prostatic capsule, others, such as ciprofloxacin, trimethoprim/sulfamethoxazole, and tetracyclines such as doxycycline penetrate prostatic tissue well. In acute prostatitis, penetration of the prostate is not as important as for category II because the intense inflammation disrupts the prostate-blood barrier. It is more important to choose a bactericidal antibiotic (kills bacteria, e.g., a fluoroquinolone antibiotic) rather than a bacteriostatic antibiotic (slows bacterial growth, e.g. tetracycline) for acute potentially life-threatening infections.

Severely ill patients may need hospitalization, while nontoxic patients can be treated at home with bed rest, analgesics, stool softeners, and hydration. Men with acute prostatitis complicated by urinary retention are best managed with a suprapubic catheter or intermittent catheterization. Lack of clinical response to antibiotics should raise the suspicion of an abscess and prompt an imaging study such as a transrectal ultrasound (TRUS).

A number of other conditions can cause fevers following delivery including: urinary tract infections, breast engorgement, atelectasis and surgical incisions among others.

Puerperal fever is diagnosed when:

- A temperature rise above maintained over 24 hours or recurring during the period from the end of the first to the end of the 10th day after childbirth or abortion. (ICD-10)

- Oral temperature of or more on any two of the first ten days postpartum. (USJCMW)

Puerperal fever (from the Latin "puer", "male child (boy)"), is no longer favored as a diagnostic category. Instead, contemporary terminology specifies:

1. the specific target of infection: endometritis (inflammation of the inner lining of the uterus), metrophlebitis (inflammation of the veins of the uterus), and peritonitis (inflammation of the membrane lining of the abdomen)

2. the severity of the infection: less serious infection (contained multiplication of microbes) or possibly life-threatening sepsis (uncontrolled and uncontained multiplication of microbes throughout the blood stream).

Endometritis is a polymicrobial infection. It frequently includes organisms such as "Ureaplasma", "Streptococcus", "Mycoplasma", and "Bacteroides", and may also include organisms such as "Gardnerella", "Chlamydia", "Lactobacillus", "Escherichia", and "Staphylococcus".

Bacteria and yeast, including those naturally occurring as part of the human microbiome, can travel along urinary catheters and cause an infection in the bladder, kidneys, and other organs connected to the urinary tract.

CAUTI can lead to complications such as prostatitis, epididymitis, and orchitis in men, and cystitis, pyelonephritis, gram-negative bacteremia, endocarditis, vertebral osteomyelitis, septic arthritis, endophthalmitis, and meningitis in all patients. Complications associated with CAUTI cause discomfort to the patient, prolonged hospital stay, and increased cost and mortality. It has been estimated that more than 13,000 deaths are associated with UTIs annually. Estimated > 560,000 nosocomial UTIs annually.

If left untreated, complications may arise including abscess formation, peritonitis, sepsis, and damage to the urinary tract by fibrosis and granuloma formation. It is recommended, as a first step, to drain the lesion with ultrasound or CT guidance. If a patient has an underlying obstructive problem it needs to be addressed according to its cause.