Step 3 Infectious Disease

All patients diagnosed with gonococcal urethritis should also be treated empirically with an agent active against C trachomatis, such as oral doxycycline 100 mg twice a day for 7 days or oral azithromycin 1 g as a single dose

• First step in evaluating an asymptomatic person with recent significant exposure to tuberculosis patients is to obtain a tuberculin skin test.
• If the initial test result is negative, a second test should be performed 10 weeks after the last known exposure.

• Tuberculin skin testing detects the presence of latent tubercular infection.
• The treatment of latent tubercular infection should be strongly considered in all patients, especially in children less than 15 years of age and in HIV positive patients.

• Pearly penile papules are considered a normal variant.
• They are not spread by sexual contact or activity, and harbor no malignant potential.
• These asymptomatic lesions are more common in uncircumcised males and are thought to occur in a substantial proportion of the male population.
• They typically appear as one or multiple rows of small, flesh colored, dome-topped or filiform papules positioned circumferentially around the corona or sulcus of the glans penis.
• Treatment is not necessary.

• Antiviral therapy with oseltamivir can be considered in certain influenza patients including those who are older than 65, pregnant, or who have high risk medical conditions such as pulmonary or cardiac disease.
• Antiviral therapy should also be considered in patients who are hospitalized or who have involvement of the lower respiratory tract.
• In patients without high risk conditions who have only mild illness, antiviral therapies have benefit only if started within 48 hours of symptom onset.
• If patients present after 48 hours, symptomatic treatment with acetaminophen is most appropriate.

• Physicians with HIV, Hepatitis C, or Hepatitis B are a cause of controversy in the medical community because of the fear that they may transmit the particular infection to their patients.
• The American Medical Association's policy on this issue states that physicians who have a known infectious disease that could pose a significant risk if contracted by the patient should not engage in any activity that poses a significant risk of transmission to the patient.
• As a result, mandatory reporting of physicians is inappropriate unless there is conclusive evidence that the physician poses a danger to patients.

• Hydrophobia is pathognomonic for rabies; water triggers pharyngeal spasms that cause the patient to be frightened of drinking.
• The illness usually starts with a few days of nonspecific prodromal symptoms, including fever and malaise. Neurologic symptoms (eg, confusion, lethargy, paralysis, aphasia) develop later in the course of the disease.

• The acquisition of rabies from bats can occur from an unrecognized bite or a scratch, and possibly by inhalation of aerosolized viral particles.
• Bats are found in all states except Hawaii, and spelunking (cave exploration) is a risk factor for rabies acquisition from bats.

• Human rabies is a life-threatening infection characterized by hydrophobia and neurologic decline.
• Post-exposure prophylaxis is effective only in preventing disease prior to manifestation of symptoms.
• After disease onset, treatment is primarily palliative, and most patients suffer from coma and death within weeks of illness onset.
• Family members should be advised to expect long-term neurologic deficits in the rare chance that the patient does survive

• It is diagnosed when there are more than 250 neutrophils/mm3 in the ascitic fluid of a patient with nephrotic syndrome or cirrhosis.
• Management involves the administration of lactulose.
• Cultures are not always positive in this condition; however, antibiotic therapy must not be delayed while the results are pending.

• The MELD score is an objective measurement that uses serum bilirubin, INR, and serum creatinine levels to determine 90-day mortality in patients with advanced liver disease.
• The calculation is commonly used in assessing candidates for transplant livers and TIPS placement

• It has has 3 distinct phases.
• The first is an acute phase of mild, nonspecific symptoms with fever or myalgias, followed by an indeterminate phase with serologic or parasitic evidence of T cruz iinfection in the absence of signs or symptoms of infection.
• The final phase is chronic Chagas cardiomyopathy and gastrointestinal disease.

• It is the leading cause of dilated cardiomyopathy in Central and South America.
• Findings of right-sided heart failure (eg, jugular venous distension, ascites, edema) are more pronounced than those of left heart failure (eg, dyspnea, crackles).
• These patients frequently develop arrhythmias, including sinus node dysfunction, complete heart block, and ventricular tachycardia.
• Echocardiogram shows varying degrees of biventricular dysfunction, along with left ventricular apical aneurysm, which is considered pathognomonic of Chagas cardiomyopathy.

• It causes community-acquired pneumonia that is commonly accompanied by extra-pulmonary symptoms such as diarrhea, nausea, vomiting, and neurologic findings (headache, confusion).
• Sputum analysis reveals many neutrophils, but very few, if any, organisms.

• Radiographs are usually obtained in patients when there is suspicion for osteomyelitis, although they lack sensitivity, particularly in the first 2 weeks of infection.
• Magnetic resonance imaging (MRI) is the first-line test to confirm a diagnosis of foot osteomyelitis, with computed tomography scan or three-phase bone scan being alternatives in patients unable to have an MRI.

• Induced sputum is the most common means of confirming the diagnosis.
• If an adequate sample is produced the specificity is high, however sensitivity is somewhat lower.
• Fiberoptic bronchoscopy with bronchoalveolar lavage is the recommended procedure for the direct identification of organisms in the bronchoalveolar tree or respiratory secretions.

• Early use of corticosteroids has been shown to decrease the mortality rate and the rate of respiratory failure in patients with moderate to severe Pneumocystis pneumonia (PCP).
• Steroids has anti-inflammatory effects, thus prevents further alveolar damage.
• Corticosteroid use is recommended in moderate to severe PCP infections with an alveolar-arterial oxygen gradient of 35 mmHg or more, and/or an arterial oxygen tension (Pa02) of 70 mmHg or less on room air.

• Clostridium difflcile colitis is usually diagnosed by stool studies for C difflcile toxin such as polymerase chain reaction (PCR) or enzyme immunoassay (EIA) for Clostridium difflcile toxins A and B.
• PCR is usually preferred due to higher sensitivity than EIA.
• Patients with negative laboratory testing and high clinical suspicion for C difflcile colitis usually undergo limited colonoscopy or sigmoidoscopy to document pseudomembranous colitis and confirm the diagnosis.

• In all such patients, the results of tuberculin skin testing should be compared to a baseline on the prior test.
• An increase in the skin test reactivity of greater than 10 mm (in patients less than 35 years of age) or greater than 15 mm (in patients older than 35 years of age) is considered a positive test for new infection.
• When baseline skin test values are not available, the test results should be interpreted as if the BCG vaccination never occurred .

• All healthcare workers with latent tuberculosis infection should be counseled about the risk of developing active tuberculosis and offered preventive therapy with isoniazid for 6 to 12 months.
• They should not be excluded from the workplace if they refuse to accept the recommended therapy.

HIV-infected patients with syphilis of unknown duration or late latent syphilis (syphilis acquired more than a year earlier) with neurologic symptoms should have cerebrospinal fluid examined before treatment.

• It is an acute febrile reaction that develops within 24 hours after the initiation of treatment for spirochetal infection (eg, syphilis, leptospirosis, tick-borne spirochetes).
• Fever is usually accompanied by malaise, chills, headache, and myalgias.
• The etiology of the reaction is thought to be due to an innate immunological reaction to the lysis of spirochetes.
• No effective prevention is available.

Community-acquired pneumonia in older patients with other coexisting medical illnesses should be ideally treated in the hospital

• Patients with an adequate response to the vaccine, demonstrated by a HBsAb titer of more than 10 miU/mL, are not at risk of contracting the virus and do not require post-exposure prophylaxis.
• Post-exposure prophylaxis for exposed patients who have either not been vaccinated or who did not appropriately respond to vaccination involves both hepatitis B immunoglobulin (HBIG) as well as vaccination, both of which should be administered within 12 hours of the exposure.

• 1. didanosine-induced pancreatitis
• 2. abacavir-related hypersensitivity syndrome
• 3. lactic acidosis secondary to the use of any of the NRTis
• 4. Stevens-Johnson syndrome secondary to the use of any of the NNRTis
• 5. nevirapine-associated liver failure
• 6.Crystal-induced nephropathy is a well-known side effect of indinavir therapy

• HIV prophylaxis after unprotected sexual intercourse with an individual who is HIV-positive is recommended within 72 hours after the sexual encounter.
• Standard post-exposure prophylaxis consists of the administration of two nucleoside reverse transcriptase inhibitors (e.g., zidovudine and lamivudine, tenofovir and lamivudine or tenofovir and emtricitabine) for four weeks.

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• It can serve as the surrogate marker for infectivity; patients with 3 negative smears are considered noninfectious for tuberculosis.
• But patients with negative smears may still have active infection which will require treatment.
• The positive predictive value of 3 sputum samples for acidfast bacilli (AFB) testing can range as high as 90% for diagnosing active tuberculosis (TB), but AFB testing has low sensitivity for ruling out TB.

• It is a common syndrome among young adults.
• This disease has a gradual onset and is characterized by the classic triad of moderate to high fever, tonsillar pharyngitis, and lymphadenopathy.
• Splenomegaly is often present.
• Epstein-Barr virus is the most common causative agent of IM, and is transmitted via intimate contact with oropharyngeal secretions (thus the nickname "the kissing disease").

• The diagnostic test of choice in confirming EBV IM is the Monospot test, which screens for heterophile antibodies that agglutinate horse red blood cells.
• Atypical lymphocytes are commonly seen on peripheral blood smears, but are not sensitive or specific for EBV IM.

• Evaluation for EBV-specific antibodies should be done next.
• The presence of lgM and lgG viral capsid antigen (VCA) antibodies suggests an acute EBV infection, and the diagnosis is confirmed if there are no lgG EBV nuclear antigen (EBNA) antibodies present.
• The lgG EBNA antibodies are not seen in acute infection, and only appear 6 to 12 weeks after the onset of symptoms.

• Treatment is supportive .
• Acetaminophen or NSAIDs will provide some symptomatic relief. Adequate fluids, nutrition, and rest are imperative

• Corticosteroids are warranted in the treatment of infectious mononucleosis during those select instances when airway obstruction appears imminent (shortness of breath while recumbent is a classic warning sign).
• Corticosteroids should also be considered in patients with infectious mononucleosis who are suffering from overwhelming infection or other serious complications (e.g., aplastic anemia or thrombocytopenia).

• It causes mild illness classically characterized by low-grade fever, lymphadenopathy involving the posterior cervical and occipital lymph nodes, and a maculopapular rash that begins on the face and spreads caudally.
• Nonspecific symptoms (eg, coryza, conjunctivitis, malaise, anorexia) may also be noted.

• Supportive treatment is sufficient when the illness is self limited, and the rash usually disappears within 3-5 days.
• Potential complications include an acute arthritis that typically resolves within several weeks, thrombocytopenia, and encephalitis.

• The best initial therapy for oral candidiasis (thrush) is a topical antifungal (e.g., nystatin suspension or clotrimazole troches), with an oral antifungal such as fluconazole used for resistant cases.
• In patients where thrush is secondary to inhaled corticosteroids, proper technique should be assessed by watching the patient use the inhaler.
• Patients should also be advised to rinse their mouth after using inhaler.

• It is indicated for the treatment of latent tuberculosis infection in individuals who have positive tuberculin skin tests more than or equal to 5mm and were close contacts of patients recently diagnosed with tuberculosis .
• Severe and sometimes fatal hepatitis is one known adverse effect of INH.
• Incidence of clinical hepatitis is estimated to be 2.6% for those who drink alcohol daily, already have liver disease, or are age 50 years and older.

• Most of the patients become symptomatic five to seven days after the tick bite.
• Early symptoms of the infection are nonspecific and can be misleading.
• Such symptoms include: low-grade fever, lethargy, myalgias and headaches.
• The rash of Rocky Mountain spotted fever is typically seen on the third to fifth day of illness.
• It is a petechial rash which usually begins on the ankles and wrists, and spreads to the palms, soles, and to the central body.
• In severe, fulminant cases, the patient may develop changes in mental status (i.e. confusion), focal neurological signs, seizures, and multiorgan dysfunction, leading to death.

• There is no single, reliable, diagnostic test during the early phase of the illness. The diagnosis and the decision to treat patients should be based clinically - on the patient's presentation in the right setting (endemic area in spring or early summer).
• Patients should be started on treatment early, without waiting for confirmatory tests, since the delay in treatment is associated with a higher mortality rate .

• If the infecting organism is different from that of the original infection, it is called a recurrence.
• If the infecting organism is the same original infecting organism within 2 weeks of completion of treatment, it is called a relapse.
• If an infection with the same organism occurs 2 weeks after completion of antibiotic therapy, it is defined as a recurrent infection.

• They are indicated when patients experience at least 2 infections in 6 months, and are used for periods ranging from 6 to 12 months.
• If the patient is able to associate the UTI with sexual intercourse, a single dose of an antibiotic immediately after coitus is effective.
• Before starting antibiotic prophylaxis, one should make sure that the urine culture is negative after the initial treatment is completed

• Insulin resistance is commonly seen in HIV patients, possibly because of altered secretion of the hormones adiponectin and leptin by abnormal adipocytes.
• Antiretroviral therapy may also play a role in the development of HIV lipodystrophy.
• Dyslipidemia is another commonly associated abnormality.
• Oral Hypoglycemics, metformin and thiazolidinediones such as rosiglitazone and pioglitazone may have efficacy in treating HIV lipodystrophy, suggesting a link between the two conditions.

• HIV infected patients frequently have dyslipidemia, particularly hypertriglyceridemia, which can be exacerbated by antiretroviral therapy.
• Statins are the first line treatment for most patients, but a fibrate medication should be used if the triglyceride level is more than 500 mg/dl.

• It manifests clinically with lower urinary tract infection symptoms and prostatic tenderness; however, it can also be asymptomatic and have no findings on physical examination.
• The most effective treatment is quinolones, preferably ciprofloxacin or levofloxacin, and a second alternative is TMP-SMX. Therapy must be given for 6 to 12 weeks.

• It can be considered in women who have had more than two UTis in six months or more than three UTis in a year.
• Prophylaxis can be used either continuously for up to several years or solely after intercourse in women whose UTis occur only after sexual activity.
• Fluoroquinolones, sulfamethoxazole-trimethoprim, and nitrofurantoin are the most commonly used agents.
• An additional option is providing female patients with antibiotics in advance, and allowing the patient to self -diagnose and treat her UTis.

• They should be advised to seek medical attention if they have symptoms of Lyme disease such as rash, arthritis, neurologic changes, or fatigue, particularly if they recall a recent tick bite.
• While doxycycline is the usual first-line agent for treating Lyme disease, Lyme disease in pregnancy is treated with amoxicillin or cefuroxime because they pose less risk to the fetus.

• It is a paradoxical worsening of preexisting (and sometimes subclinical) infections in HIV-positive individuals.
• The syndrome usually occurs days to weeks after the initiation of treatment with highly active antiretroviral therapy (HAART), and is thought to arise secondary to the rapid improvement in immune function allowed for by HAART.
• Typically, however, IRIS is self-limited, and is best managed with continued HAART and antibiotic treatment of the underlying pathogen.

• Asymptomatic patients without radiographic evidence of active TB who have been treated previously for active TB or LTBI need no further TB treatment.
• There is no need for a repeat TST as it will likely remain positive.

• It measures interferon-gamma release by T cells stimulated by specific M tuberculosis antigens.
• They are an alternate means of diagnosing LTBI and cannot distinguish LTBI from active TB.
• Unlike TSTs, they do not require repeat visits and are not affected by vaccination with Bacille Calmette-Guerin.

• Prior BCG vaccination should rarely cause more than 15 mm induration with PPD skin testing.
• The effect of BCG vaccination on induration decreases significantly 15 years after the vaccine is received.
• Isoniazid treatment for 9 months is recommended for patients with latent tuberculosis.