Infectious Diseases

·         FIRST DISEASE : ---> Measles.

SECOND DISEASE : ---> Scarlet Fever.

THIRD DISEASE :---> Rubella or German Measles.

FOURTH DISEASE :---> Duke's Disease 

FIFTH DISEASE :---> Erythema Infectiosum caused by Parvovirus B19

SIXTH DISEASE :---> Exanthem Subitum / Roseola Infantum (HHV-6)(HHV-7 also mentioned)

( The terms "fourth disease" and "Dukes' disease" are rarely used today.)

·         Salmonella is by far the most common cause of febrile gastroenteritis in early infancy. Campylobacter is second in frequency to Salmonella as a bacterial cause of enteritis in infancy. Yersinia is a rare cause. Shigellosis is a disease that is rare in infancy but common in the 1- to 3-yr-old child. Rotavirus rarely (or never) causes bloody diarrhea.

·         A mean bactericidal concentration (MBC) > 4 times the minimum inhibitory concentration (MIC) defines bacterial tolerance.

·         Antipyretic therapy is directly beneficial in high-risk patients who have chronic cardiopulmonary diseases, metabolic disorders, or neurologic diseases.

·         Periodic fever is used to narrowly describe fever syndromes with a regular periodicity, such as cyclic neutropenia, and the syndrome of periodic fever, aphthous stomatitis, pharyngitis, and adenopathy (PFAPA).

·         Temperatures in excess of 41°C are most often associated with a noninfectious cause. Causes of very high temperatures (>41°C) include central fever (resulting from central nervous system dysfunction involving the hypothalamus), malignant hyperthermia, malignant neuroleptic syndrome, drug fever, or heatstroke.

·         Occult bacteremia (bacteremia without an obvious focus of infection) due to Streptococcus pneumoniae, H. influenza type b, N. meningitidis, or nontyphoidal Salmonella occurs in approximately 4% of relatively well-appearing children between 3 and 36 mo of age with fever (rectal temperature >38.0°C). S. pneumonia accounts for 90% of cases of occult bacteremia.

·         Fever of unknown origin is sometimes due to hypothalamic dysfunction. A clue to this disorder is failure of papillary constriction due to absence of the sphincter constrictor muscle of the eye. This muscle develops embryologically when the hypothalamus is also undergoing differentiation.

·         Focal seizures in a febrile neonate with evidence of systemic shock and hepatic dysfunction suggest the possibility of systemic herpes simplex virus infection.

·         Toxic shock syndrome and Kawasaki disease share many features, but Kawasaki disease is not accompanied by hypotension and shock. Kawasaki disease also typically occurs in children younger than 5 yr. Toxic shock syndrome can complicate focal infections caused by TSST-1-producing strains of Staphylococcus aureus.

·         The classic rash of scarlet fever has a texture of gooseflesh or coarse sandpaper. Pastia lines are areas of hyperpigmentation that do not blanch with pressure that may appear in creases, particularly in the antecubital fossae. White strawberry tongue is characteristic of the early illness; as the white coat desquamates, the red strawberry tongue persists. Skin desquamation begins toward the end of the first week of illness. Preauricular lymphadenopathy is not typical.

·         Listeria isolates are usually sensitive to penicillin, ampicillin, erythromycin, and tetracycline but are not susceptible to the cephalosporins, including the third-generation cephalosporins. The addition of an aminoglycoside (e.g., gentamicin) lowers the minimum bactericidal concentration.

·         Nocardia infection is characterized by remissions and exacerbations.

·         Chemoprophylaxis for contacts of a person with proven or suspected N. meningitidis infection is indicated for all household, daycare, and nursery care contacts. The index patient should also receive rifampin prophylaxis if penicillin was used for treatment.

Same way,Chemoprophylaxis for contacts of a person with proven H. influenzae type b infection is indicated if the close contact group includes one or more children younger than 48 mo of age who are not fully immunized; under these circumstances, rifampin prophylaxis is indicated for all members of the close contact group, including the index patient.

·         Nonsuppurative complications of meningococcal disease appear to be immune complex-mediated and become apparent 4-9 days after the onset of illness. Arthritis and cutaneous vasculitis (erythema nodosum) are most common.

·         Pertussis is a "family" disease with various degrees of symptoms and colonization. After diagnosis of pertussis in a toddler, erythromycin should be given to the patient and to All family members regardless of age, symptoms, or immunization status.

·         A 7- to 10-fold relative risk for infantile hypertrophic pyloric stenosis (IHPS) has been reported in infants younger than 6 wk of age treated with orally administered erythromycin. The highest risk appears to be in the first 2 wk of life in term infants, and with courses of 14 days or longer. The risk of IHPS after treatment with azithromycin or clarithromycin is unknown.

·         Only Shigella dysenteriae serotype 1 and certain Shiga toxin-producing E. coli (STEC) commonly produce significant amounts of Shiga toxin and cause hemolytic-uremic syndrome.

·         STEC organisms represent a particularly difficult therapeutic dilemma; antibiotic treatment can induce toxin production and phage-mediated bacterial lysis with toxin release. Current data suggest that antibiotics should not be given for STEC infection because they may increase the risk for HUS.

·         Many patients affected by Y. pseudotuberculosis do not have diarrhea, and thus a stool culture is not even considered as part of the diagnostic evaluation. If the extent of infection is limited to the mesenteric lymph nodes, the stool culture results may be negative.

·         The unusually severe lymph node tenderness, especially in the presence of systemic toxicity, distinguishes bubonic plague caused by Y. pestis from the typical lymphadenopathy associated with cat-scratch disease or tularemia.

·         Mucoid strains of P. aeruginosa are common in persons with cystic fibrosis, causing insidious but progressive respiratory deterioration, but are rarely encountered in other persons. B. cepacia is an opportunist that rarely infects immunocompetent persons but is common in persons with cystic fibrosis and causes an acute respiratory syndrome with fever, leukocytosis, and progressive respiratory failure.

·         Because of the difficulty in culture techniques and the inconsistency of seroconversion, the urinary antigen test for Legionella is a useful method in the prompt diagnosis of Legionella infection.

·         The oculoglandular syndrome (conjunctivitis, lymph node) is the most frequent atypical manifestation of cat-scratch disease. Fever occurs in only 30% of cases of cat-scratch disease.

·         The first and essential step in treatment of Clostridium difficile-associated diarrhea is the discontinuation of the current antibiotics, if at all possible. In most instances this course combined with appropriate fluid and electrolyte replacement is sufficient. C.difficile is frequently isolated from the stool of healthy infants. The interpretation of a positive stool culture or toxin requires clinical correlation. Treatment would not be indicated for an asymptomatic infant.

·         Pulmonary tuberculosis is best confirmed by culture and isolation of M. tuberculosis. The best culture specimen in young children is three consecutive early-morning gastric aspirates obtained before the child has arisen and before peristalsis has emptied the stomach contents. The yield is approximately 50%, but the yield from bronchoscopy is even lower. Negative cultures never exclude the diagnosis of tuberculosis.

·         There is limited cross-reactivity of the treponemal test (MHA-TP, FTA-ABS) material with other spirochetes, esp. Borrelia burgdorferi, the causative organism of Lyme disease.

·         Periostitis, occurring in the long bones, is most typical of congenital syphilis. Osteochondritis is a common finding in congenital cytomegalovirus, rubella, and syphilis infections.

·         A biphasic course is characteristic of icteric leptospirosis (Weil syndrome). Hepatorenal dysfunction follows anicteric leptospirosis in less than 10% of cases.

·         Doxycycline (for 14-21 days) is the treatment of choice for Lyme borreliosis in children older than 8 yr of age, but amoxicillin (for 14-21 days) is the treatment of choice in children younger than 8 yr. Where effective alternatives are available, children younger than 8 yr should not be treated with doxycycline because it may cause permanent discoloration of the teeth. Erythromycin is an alternative for persons who cannot take either doxycycline or amoxicillin.

Paralysis of the facial (7th) cranial nerve is relatively common in children with Lyme disease and may be the initial or the only manifestation of infection. The paralysis usually lasts 2 to 8 wk and resolves completely in most cases. There is no evidence that the clinical course of the facial palsy with Lyme disease is affected by antimicrobial treatment

·         C. trachomatis pneumonia is characterized by insidious onset of persistent cough and tachypnea, with the notable absence of fever. Rales are common, but wheezes are uncommon, which helps distinguish C. trachomatis from RSV pneumonia.

·         Chloramphenicol and tetracyclines have proven efficacy against Rocky Mountain spotted fever, but chloramphenicol may be associated with higher mortality. Dental staining is unlikely with a single course of a tetracycline. Doxycycline is recommended because the risk of dental staining is less than with other tetracyclines.

·         Catheter-related infections and fungemia with Malassezia furfur occur almost exclusively in patients receiving intravenous lipids. The use of lipid emulsions containing medium-chain triglycerides inhibits the growth of Malassezia.

·         Sporothrix thrives in decaying vegetation but also can be transmitted by bites and scratches of animals, most frequently cats and armadillos.

·         Hand, foot, and mouth disease caused by enterovirus 71 is frequently more severe than that due to coxsackievirus A16, with high rates of associated neurologic disease including aseptic meningitis, encephalitis, and paralysis.

·         Resistant HSV: Foscarnet

·         The IgM-VCA is the best single test to identify acute EBV infection.

·         Sensorineural hearing loss is a risk after asymptomatic congenital CMV infection. The incidence of neonatal CMV-positive urine is much greater than the incidence of symptomatic neonatal CMV inclusion disease (e.g., microencephaly, retinitis, being small for gestational age, petechiae).

·         The incidence of congenital CMV infection ranges from 0.2 to 2.4% of all live births, with the higher rates among populations with a lower economic standard of living. The risk for fetal infection is greatest with maternal primary CMV infection (30%) and much lower with recurrent infection (<1%).

·         The generally benign nature of roseola precludes consideration of antiviral therapy. Although HHV-6 is inhibited by ganciclovir, cidofovir, and foscarnet (but not acyclovir), the clinical efficacy and benefit of antiviral therapy for roseola has not been established.

·         RSV-IVIG is contraindicated and palivizumab is not recommended for infants with cyanotic heart disease. In studies of RSV-IVIG given for prophylaxis, mortality is higher in treated patients with heart disease.

·         ICAM-1 is present on the epithelium covering the lymphoepithelium of the adenoids and other epithelial cells of the nose and is the cell receptor for most rhinoviruses.

·         HIV gp120 has significant heterogeneity among HIV strains, which is one reason for the difficulty in developing an effective HIV vaccine.

·         Serologic diagnosis of HIV infection by ELISA and Western immunoblot analysis is reliable only after 18 mo of age. Before this age, residual maternal antibodies acquired transplacentally may be responsible for the positive serologic test results.

·         All infants 6 wk to 1 yr of age born to HIV-infected mothers should receive prophylaxis for P. carinii regardless of CD4 cell count and percentage. After 12 mo of age, prophylaxis is prescribed according to the CD4 cell count and percentage.

·         HTLV-I is prevalent in Japan and the Caribbean, where breast-feeding is a major mode of transmission.

·         Naegleria organisms are found in many freshwater sources, including ponds, lakes, and stagnant pools. It occurs most commonly in previously healthy children and adults. Therapy is often difficult, and morbidity and mortality are high.

The clinical manifestations and course of Acanthamoeba and Balamuthia infection of the central nervous system are similar. Most patients with Acanthamoeba are immunocompromised, in contrast to Balamuthia infection.

·         All persons with Entamoeba histolytica trophozoites or cysts in their stools should be treated, whether they have symptoms or not.

·         Cryptosporidium is prevalent in developing countries and in children younger than 2 yr of age. It causes watery, nonbloody diarrhea that is usually self-limited but may persist for several weeks. Because illness is self-limited in immunocompetent persons, no specific therapy is required. Treatment of immunocompromised persons is with paromomycin, with or without azithromycin.

·         The combination of clindamycin (20-40 mg/kg/day divided tid PO) and quinine (25 mg/kg/day divided tid PO) for 7 to 10 days is the therapy of choice for babesiosis in children.

·         Congenital toxoplasmosis is associated with organ dysfunction, inflammation, growth retardation, thrombocytopenia, hepatitis, retinitis, and microcephaly, but not with true congenital anomalies like such as cleft palate or patent ductus arteriosus.

                                               

·         Most persons are infected with P. carinii before 4 yr of age. Most primary infections in immunocompetent persons are asymptomatic.

·         The recommended treatment regimen for pinworms (Enterobius vermicularis) is mebendazole, 100 mg orally, with a repeat dose in 2 wk. An alternative treatment is albendazole, 400 mg orally, with a repeat dose in 2 wk.

·         Hydatid disease (echinococcosis) does not respond to praziquantel, probably due to failure to penetrate the liver cyst. Except for Fasciola hepatica, all other trematode and cestode infections (flukes and tapeworms) will respond to praziquantel.

·         Preterm infants, including those of very low birthweight, should be vaccinated at the same chronological age as for full-term infants and according to the routine childhood immunization schedule. One exception to this recommendation is hepatitis B vaccination of those born of HBsAg-negative mothers with low birthweights (i.e., <2 kg). Initiation of vaccination in this case should be delayed until the infant is 1 mo of age.

·         Upward pressure applied to the angle of the mandible produces tenderness with mumps (Hatchcock's sign); this maneuver produces no tenderness with adenitis.

·         Herpes gladiatorum is a term used to describe ocular and cutaneous infection with herpes simplex virus type 1, which occurs in wrestlers and rugby players. The infection is transmitted primarily by direct skin-to-skin contact and is endemic among high-school and college wrestlers