Which infectious disease needs oxygen to survive

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Our service is free and we are here to help you. Learn About Tuberculosis. Section Menu. Key Points While contagious, TB is not easily spread from person to person. About 1. About 10 million people have active TB worldwide. In the United States, TB is much less common. Active TB disease occurs most often in the lungs. The lungs are where your body carries out gas exchange between the air and the bloodstream, exchanging carbon dioxide for fresh oxygen.

This exchange takes place at the alveoli, tiny bubble-like divisions of the lungs. When you breathe, you inhale plenty of other material along with oxygen, including bacteria.

In order to infect you, the tuberculosis bacteria have to pass through the defenses in your airway and reach the alveoli. When the body's immune system notices the bacteria, it surrounds them with immune cells, creating collections of cells known as granulomas and effectively cutting off the bacteria from the rest of the body.

The bacteria can persist in granulomas for many years as a latent TB infection. In the United States, TB is much less common than it used to be. Of the some 13, new cases of active disease each year in the United States, over half occur in persons born outside of the country. Tuberculosis is very common in the developing world. It has been estimated that as much as a third of the world's population is infected with M.

Since the introduction of effective antibiotics, tuberculosis management has changed dramatically. Most important, people with tuberculosis are no longer sent to specialized sanitariums; now, they are treated in general hospitals and clinics.

The first step is typically microscopic examination to check for acid-fast bacilli AFB. Tubercle bacilli are nominally gram-positive but take up Gram stain inconsistently; samples are best prepared with Ziehl-Neelsen or Kinyoun stains for conventional light microscopy or fluorochrome stains for fluorescent microscopy.

Although finding AFB in a sputum smear is strong presumptive evidence of TB, definitive diagnosis requires a positive mycobacterial culture or nucleic acid amplification test NAAT. Culture is also required to isolate bacteria for drug-susceptibility testing and genotyping. However, it can take up to 3 mo for final confirmation of culture results. Liquid media are more sensitive and faster that solid media, with results available in 2 to 3 wk.

Rapid antigen testing to detect the MPB64 antigen can confirm that organisms growing on mycobacterial culture are M. The line probe assay can identify the presence of M. This test is usually done only on smear-positive specimens. In such cases, treatment can be started based on rifampin susceptibility. Drug susceptibility tests DSTs should be done on initial isolates from all patients to identify an effective anti-TB regimen.

These tests should be repeated if patients continue to produce culture-positive sputum after 3 mo of treatment or if cultures become positive after a period of negative cultures. Results of DSTs may take up to 8 wk if conventional bacteriologic methods are used, but several new molecular DSTs can detect drug resistance to rifampin or to rifampin and isoniazid in a sputum sample within hours.

Transbronchial biopsies can be done on infiltrative lesions, and samples are submitted for culture, histologic evaluation, and molecular testing. Gastric washings, which are culture-positive in a minority of samples, are no longer commonly used except in small children, who usually cannot produce a good sputum specimen. However, sputum induction is being used in young children who are able to cooperate. Ideally, biopsied samples of other tissue should be cultured fresh, but NAAT can be used for fixed tissues eg, for biopsied lymph node if histologic examination unexpectedly detects granulomatous changes.

The latter use of NAAT has not been approved but can be extremely useful, although positive and negative predictive values have not been established. It is positive in both latent and active infection and thus cannot distinguish between the two.

It is critical to give the injection intradermally, not subcutaneously. A well-demarcated bleb or wheal should result immediately. The diameter of induration not erythema transverse to the long axis of the arm is measured 48 to 72 h after injection. Anergy probably occurs because inhibiting antibodies are present or because so many T cells have been mobilized to the disease site that too few remain to produce a significant skin reaction.

False-positive results may occur if patients have nontuberculous mycobacterial infections or have received the BCG vaccine. The IGRA is a blood test based on the release of interferon-gamma by lymphocytes exposed in vitro to TB-specific antigens. Importantly, they are often negative in patients with remote TB infection. Long-term studies are being done to see whether TST-positive, IGRA-negative patients particularly those with immunosuppression are at low risk of reactivation.

In immunocompetent patients with drug-susceptible pulmonary tuberculosis, even severe disease with large cavities, appropriate therapy is usually curative if it is instituted and completed.

TB is much more aggressive in immunocompromised patients and, if not appropriately and aggressively treated, may be fatal in as little as 2 mo from a patient's initial presentation, especially with MDR-TB.

However, with effective antiretroviral therapy and appropriate anti-TB treatment , the prognosis for patients with HIV infection, even those with MDR-TB, may approach that of immunocompetent patients. Poorer outcomes should be expected for patients with XDR-TB because there are so few effective drugs. Most cases of acute viral hepatitis Most patients with TB can be treated as outpatients, with instructions on how to prevent transmission usually including.

Surgical face masks for TB patients are stigmatizing and are typically not recommended for cooperative patients. Precautions are needed until drug treatment has made patients sufficiently noncontagious. For patients with proven drug-susceptible or MDR-TB, precautions are maintained until there is a clinical response to therapy typically, 1 to 2 wk. However, for XDR-TB, response to treatment may be slower, and the consequences of transmission even greater; thus, a more convincing response to therapy eg, smear or culture conversion is required to end precautions.

Need for respiratory isolation, as for people living in congregate settings where previously unexposed people would be regularly encountered important primarily if effective treatment cannot be ensured.

Anyone entering the room should wear a respirator not a surgical mask that has been appropriately fitted and that meets National Institute for Occupational Safety and Health certification N or greater. Because risk of exposing other hospitalized patients is high, even though patients receiving effective treatment become noncontagious before sputum smears become negative, release from respiratory isolation usually requires 3 negative sputum smears over 2 days, including at least one early-morning negative specimen.

In hospitals and clinics, the highest risk of TB transmission is from patients who have undiagnosed TB or unidentified drug resistance and are receiving inadequate treatment, not from known TB patients who are receiving effective treatment. To improve treatment adherence, ensure cure, and limit transmission and the development of drug-resistant strains, public health programs closely monitor treatment, even if patients are being treated by a private physician.

In most states, TB care including skin testing, chest x-rays, and drugs is available free through public health clinics to reduce barriers to treatment. Increasingly, directly observed therapy DOT is becoming part of optimal patient case management; DOT involves supervision by public health personnel of the ingestion of every dose of drug. In some programs, selective self-administered treatment SAT is an option for patients who are committed to treatment; ideally, fixed-dose combination drug preparations are used to avoid the possibility of monotherapy, which can lead to drug resistance.

Mechanical drug monitoring devices have been advocated to improve adherence with SAT. Evaluate potential barriers to treatment eg, extreme poverty, unstable housing, child care problems, alcoholism, mental illness.

Close contacts are people who share the same breathing space for prolonged periods, typically household residents, but often include people at work, school, and places of recreation. The precise duration and degree of contact that constitutes risk vary because TB patients vary greatly in contagiousness.

For patients who are highly contagious as evidenced by multiple family members with disease or positive skin tests, even relatively casual contacts eg, passengers on the bus they ride should be referred for skin testing and evaluation for latent infection Screening for TB Tuberculosis TB is a chronic, progressive mycobacterial infection, often with a period of latency following initial infection. The first-line drugs isoniazid INH , rifampin RIF , pyrazinamide PZA , and ethambutol EMB are used together in initial treatment for regimens and doses, see Treatment regimens Treatment regimens Tuberculosis TB is a chronic, progressive mycobacterial infection, often with a period of latency following initial infection.

It remains the single most useful and least expensive drug for TB treatment. Decades of uncontrolled use—often as monotherapy—in many countries especially in East Asia have greatly increased the percentage of resistant strains. Adverse effects of isoniazid include rash, fever, and, rarely, anemia and agranulocytosis. Monthly liver function testing is not recommended unless patients have risk factors for liver disease.

Patients with unexplained fatigue, anorexia, nausea, vomiting, or jaundice may have hepatic toxicity; treatment is suspended and liver function tests are done. After recovery from mild aminotransferase elevations and symptoms, patients can be safely challenged with a half-dose for 2 to 3 days. If this dose is tolerated typically in about half of patients , the full dose may be restarted with close monitoring for recurrence of symptoms and deterioration of liver function.

Peripheral neuropathy can result from INH-induced pyridoxine vitamin B 6 deficiency, most likely in pregnant or breastfeeding women, undernourished patients, patients with diabetes mellitus or HIV infection, alcoholics, patients with cancer or uremia, and the elderly.

A daily dose of pyridoxine 25 to 50 mg can prevent this complication, although pyridoxine is usually not needed in children and healthy young adults. INH delays hepatic metabolism of phenytoin , requiring dose reduction. It can also cause a violent reaction to disulfiram , a drug occasionally used for alcoholism. INH is safe during pregnancy. It also eliminates dormant organisms in macrophages or caseous lesions that can cause late relapse. Thus, RIF should be used throughout the course of therapy.

Adverse effects of rifampin include cholestatic jaundice rare , fever, thrombocytopenia, and renal failure. Drug interactions must be considered when using RIF. It accelerates metabolism of anticoagulants, oral contraceptives, corticosteroids, digitoxin, oral antihyperglycemic drugs, methadone , and many other drugs. The interactions of rifamycins and many antiretroviral drugs are particularly complex; combined use requires specialized expertise. RIF is safe during pregnancy. Rifabutin is used for patients taking drugs particularly antiretroviral drugs that have unacceptable interactions with RIF.

Its action is similar to RIF, but it affects the metabolism of other drugs less. When used with clarithromycin or fluconazole , rifabutin has been associated with uveitis. This prophylactic combination is not recommended for children Pyrazinamide PZA is an oral bactericidal drug.

When used during the intensive initial 2 mo of treatment, it shortens the duration of therapy to 6 mo and prevents development of resistance to RIF. The major adverse effects of pyrazinamide are GI upset and hepatitis.

It often causes hyperuricemia, which is generally mild and only rarely induces gout. PZA is commonly used during pregnancy, but its safety has not been confirmed. Ethambutol EMB is given orally and is the best-tolerated of the first-line drugs. Patients with optic neuritis present initially with an inability to distinguish blue from green, followed by impairment of visual acuity.

Because both symptoms are reversible if detected early, patients should have a baseline test of visual acuity and color vision and should be questioned monthly regarding their vision. Caution is warranted if communication is limited by language and cultural barriers. For similar reasons, EMB is usually avoided in young children who cannot read eye charts but can be used if needed because of drug resistance or drug intolerance. Another drug is substituted for EMB if optic neuritis occurs.

Ethambutol can be used safely during pregnancy. Resistance to EMB is less common than that to the other first-line drugs. Other antibiotics are active against TB and are used primarily when patients have drug-resistant TB DR-TB or do not tolerate one of the first-line drugs. The 2 most important classes are aminoglycosides and the closely related polypeptide drug, capreomycin and fluoroquinolones; aminoglycosides are available only for parenteral use. Streptomycin , once the most commonly used aminoglycoside, is very effective and bactericidal.

Resistance is still relatively uncommon in the US but is more common globally. CSF penetration is poor, and intrathecal administration should not be used if other effective drugs are available. Dose-related adverse effects of streptomycin include renal tubular damage, vestibular damage, and ototoxicity. The maximum is usually 1 g for adults, reduced to 0.

Patients should be monitored with appropriate testing of balance, hearing, and serum creatinine levels. Adverse effects of streptomycin include rash, fever, agranulocytosis, and serum sickness. Flushing and tingling around the mouth commonly accompany injection but subside quickly. Streptomycin is contraindicated during pregnancy because it may cause vestibular toxicity and ototoxicity in the fetus. Kanamycin and amikacin may remain effective even if streptomycin resistance has developed.

Their renal and neural toxicities are similar to those of streptomycin. Capreomycin , a related nonaminoglycoside parenteral bactericidal drug, has dosage, effectiveness, and adverse effects similar to those of aminoglycosides. It is an important drug for MDR-TB because isolates resistant to streptomycin are often susceptible to capreomycin , and it is somewhat better-tolerated than aminoglycosides when prolonged administration is required.

Some fluoroquinolones levofloxacin , moxifloxacin are the most active and safest TB drugs after isoniazid and rifampin , but they are not first-line drugs for TB susceptible to isoniazid and rifampin. Moxifloxacin appears to be as active as isoniazid when used with rifampin.

Other 2nd-line drugs include ethionamide , cycloserine , and para-aminosalicylic acid PAS. These drugs are less effective and more toxic than the first-line drugs but are essential in treatment of MDR-TB. Bedaquiline, delamanid, and sutezolid are new anti-TB drugs that are typically reserved for highly resistant TB precise indications are not yet fully defined or for patients who cannot tolerate other 2nd-line drugs. Drug resistance develops through spontaneous genetic mutation.

Incomplete, erratic, or single-drug therapy selects for these resistant organisms. Once a drug-resistant strain has developed and proliferates, it may acquire resistance to additional drugs through the same process.

In this way, the organism can become resistant to multiple antibiotics in steps. MDR-TB is resistant to isoniazid and rifampin , with or without resistance to other drugs. The WHO estimates that , to , new cases occurred worldwide in In parts of the world where resistance testing is inadequate or unavailable, many patients who do not respond to first-line therapy probably have unrecognized MDR-TB.

Multidrug resistance has major negative implications for TB control; alternative treatments require a longer treatment course with less effective, more toxic, and more expensive 2nd-line drugs. This additional resistance has dire therapeutic implications.

Although some patients with XDR-TB can be cured, mortality is higher, and the outcome depends on the number of effective drugs that remain as well as the extent of lung destruction caused by the bacilli.

Resistant strains can be transmitted from person to person. A person who is infected with a drug-resistant strain from another person is said to have primary drug resistance. Uninhibited transmission of drug-resistant strains in congregate settings, such as hospitals, clinics, prisons, shelters, and refugee camps, is a major barrier to global control.

Several new anti-TB drugs that may be active against resistant strains are in preclinical or clinical development but will not be available for several more years. Furthermore, unless treatment programs are strengthened eg, by full supervision of each dose and improved access to culture and susceptibility testing , stepwise resistance to new drugs is likely.

Successful treatment of drug-resistant TB depends on the use of multiple active drugs simultaneously, so that any resistance to one drug is countered by the killing effects of a 2nd, 3rd or 4th drug. Furthermore, all drugs in the regimen must be taken scrupulously for an extended period. The new anti-TB drugs bedaquiline, delamanid, and sutezolid are active against resistant strains and may help control the epidemic of drug-resistant TB.