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lnfectious Disease Complement Deficiency Diagnosis Persons with deficiencies of the terminal components of the classic complement pathway (C5-C9) are susceptible to recurrent neisserial infections. Defects in components of the alternative complement pathway of activation and the lectin pathway may also be associated with neisserial infections. Patients with deficiencies of the early components of the complement system (C2-C4) will have repeated infections with encapsulated bacteria and often SLE. Testing Obtain a CHro assay. If CHs. is low follow up with individuat component measurements. Screen all patients with repeated episodes of disseminated gonorrhea or meningococcal infection with CHro assay. Treatment Patients with complement deficiency respond to standard antibiotics IEST YOURSEIF A 21-year-old male college student has meningococcal meningitis for the third time in 2 years. ANSWER: For diagnosis, choose terminal complement deficiency. For management, select serum CHro assay. Malaria Prevention Select chloroquine for travelers to areas where chloroquine-resistant Plasmodium falciparum has not been reported (Central America, Haiti, Dominican Republic). Otherwise, select mefloquine, atovaquone-proguanil, tafenoquine, or doxycycline. Diagnosis and Testing Malaria is the most common cause of fever in returning travelers. Most infections are caused by P falciparum or Plq.smodium uiucx, and most deaths are caused by P. falciparum. * # #b; *r *" ; Symptoms develop after an incubation period of 1 week to @ @ffi & #"L@ * oto-^ **ta 3 months. ry w@ Look for:

Diagnosis and Testing Malaria is the most common cause of fever in returning travelers. Most infections are caused by P falciparum or Plq.smodium uiucx, and most deaths are caused by P. falciparum. * # #b; *r *" ; Symptoms develop after an incubation period of 1 week to @ @ffi & #"L@ * oto-^ **ta 3 months. ry w@ Look for: . cyclical paroxysms of rigors € m ***-"S & €3&*ffi. to# . fever, drenching sweats r travel history and inadequate antimalarial prophylaxis :'., ;'i*F,ffi. %ffi #mp € Plasmodiumfalciparum lnfection: ln the center of the peripheral blood smear o jaundice is a banana"shaped gametocyte diagnoslicof P.falciparum infection. . splenomegaly . coma, seizure . headache 245

lnfectious Disease Select thick and thin peripheral blood smears to diagnose malaria. parasitemia levels >2% are most consistent with p falciparum or Plasmodiumknowlesi (South and Southeast Asia) infection. DO]I'T BE TRICKED . Any traveler who has returned from a malaria-endemic area in the past year and has an undiagnosed febrile illness should undergo malaria evaluation. Treatment For non-/olcrpcrum species or P falciparum acquired in chloroquine sensitive areas, use chloroquine or hydroxychloroquine. For P falciparum acquired in chloroquine-resistant areas, choose atovaquone proguanil or artemether-lumefantrine.

DO]I'T BE TRICKED . Any traveler who has returned from a malaria-endemic area in the past year and has an undiagnosed febrile illness should undergo malaria evaluation. Treatment For non-/olcrpcrum species or P falciparum acquired in chloroquine sensitive areas, use chloroquine or hydroxychloroquine. For P falciparum acquired in chloroquine-resistant areas, choose atovaquone proguanil or artemether-lumefantrine. lnfectious Gastrointestinal Synd romes STUDY TABLE: Agents, Presentation, and Treatment of lnfectious Gastrointestinal Syndromes Agent Clinical Findings Diagnosis" Antimicrobial Treatmentb Bacterial Campylobaaer Fevers, chills, diarrhea (watery or bloody), Routine stool culture or NAAI Azithromycin; fluoroquinolone crampy abdominal pain; postinfection blood culture such as ciprofloxacin Guillain-Ba116 syndrome, lBS, intestinal (alternative) perforation, glomerulonephritis, erythema nodosum, hemolytic anemia, or reactive arthritis Shigella Dysentery (fevers, abdominal cramps, Routine stool culture or NAAT; Fluoroquinolone such as tenesmus, bloody/mucus-fi led stools; I blood cultures (with severe ciprofloxacin, or azithromycin possibly vomiting); postinfection HUS, disease) or ceftriaxone reactive arthritis, erythema nodosum, glomerulonephritis, or IBS Salmonella Fever, chills, diarrhea (watery or Routine stool culture or NAAT; Mild: none bloody), cramps, myalgia; bacteremia blood cultures (moderate to Underlying disease or severe in 10o/o-25o/o of patients; postinfection severe disease); bone marrow illness: fluoroquinolone such as reactive arthritis, erythema nodosum, and duodenal fluid cultures ciprofloxacin and/or parenteral or IBS may also be helpfulwhen third-generation cephalosporin enteric fever suspected such as ceftriaxone EHEC/STEC, most Bloody stools in >80% of patients; fever Stool culture with specialized None commonly often absent or low grade; may be media and immunoassay for Escherichia coli associated with HUS Shiga toxin or NAATfor 0157:H7 gene(s) encoding Shiga toxin ETEC (travelers' Nonbloody, watery stools; constitutional None-usually a clinical Fluoroquinolone (such as diarrhea) symptoms rare diagnosis ciprofloxacin), azithromycin, or rifaximin Yersinia Fevel diarrhea, right lower quadrant pain Stool culture with specialized Fluoroquinolone such as (may mimic appendicitis); pharyngitis; media (or culture of other ciprofloxacin intestinal perforation; postinfection involved sites); NAAT Third-generation cephalospori n reactive arthritis, hemolytic anemia, or such as ceftriaxone plus erythema nodosum gentamicin for severe disease

lnfectious Gastrointestinal Synd romes STUDY TABLE: Agents, Presentation, and Treatment of lnfectious Gastrointestinal Syndromes Agent Clinical Findings Diagnosis" Antimicrobial Treatmentb Bacterial Campylobaaer Fevers, chills, diarrhea (watery or bloody), Routine stool culture or NAAI Azithromycin; fluoroquinolone crampy abdominal pain; postinfection blood culture such as ciprofloxacin Guillain-Ba116 syndrome, lBS, intestinal (alternative) perforation, glomerulonephritis, erythema nodosum, hemolytic anemia, or reactive arthritis Shigella Dysentery (fevers, abdominal cramps, Routine stool culture or NAAT; Fluoroquinolone such as tenesmus, bloody/mucus-fi led stools; I blood cultures (with severe ciprofloxacin, or azithromycin possibly vomiting); postinfection HUS, disease) or ceftriaxone reactive arthritis, erythema nodosum, glomerulonephritis, or IBS Salmonella Fever, chills, diarrhea (watery or Routine stool culture or NAAT; Mild: none bloody), cramps, myalgia; bacteremia blood cultures (moderate to Underlying disease or severe in 10o/o-25o/o of patients; postinfection severe disease); bone marrow illness: fluoroquinolone such as reactive arthritis, erythema nodosum, and duodenal fluid cultures ciprofloxacin and/or parenteral or IBS may also be helpfulwhen third-generation cephalosporin enteric fever suspected such as ceftriaxone EHEC/STEC, most Bloody stools in >80% of patients; fever Stool culture with specialized None commonly often absent or low grade; may be media and immunoassay for Escherichia coli associated with HUS Shiga toxin or NAATfor 0157:H7 gene(s) encoding Shiga toxin ETEC (travelers' Nonbloody, watery stools; constitutional None-usually a clinical Fluoroquinolone (such as diarrhea) symptoms rare diagnosis ciprofloxacin), azithromycin, or rifaximin Yersinia Fevel diarrhea, right lower quadrant pain Stool culture with specialized Fluoroquinolone such as (may mimic appendicitis); pharyngitis; media (or culture of other ciprofloxacin intestinal perforation; postinfection involved sites); NAAT Third-generation cephalospori n reactive arthritis, hemolytic anemia, or such as ceftriaxone plus erythema nodosum gentamicin for severe disease Vibrio Bloody stools (>25% of patients), fever, Stool culture with specialized Usually no treatment unless parahaemolyticus vomiting (>50% of patients) media (blood culture with invasive suspected invasive disease); Doxycycl ne, f u oroq u i nolone i I NAAT (such as ciprofloxacin), or azithro- mycin if treating severe noninva- sive gastrointestinal il lness

Vibrio Bloody stools (>25% of patients), fever, Stool culture with specialized Usually no treatment unless parahaemolyticus vomiting (>50% of patients) media (blood culture with invasive suspected invasive disease); Doxycycl ne, f u oroq u i nolone i I NAAT (such as ciprofloxacin), or azithro- mycin if treating severe noninva- sive gastrointestinal il lness Doxycycline plus ceft riaxone for invasive infection (Continued on the next page) 247

lnfectious Disease STUDY TABLE: Agents, Presentation, and Treatment of lnfectious Gastrointestinal Syndromes (Continued) Agent Clinical Findings Diagnosis" Antimicrobial Treatmentb Clostridioides Diarrhea (gross blood in stool Stool NAAT alone or stool EIA Nonsevere: oral vancomycin or difficile uncommon), fever, abdominal pain/ toxin test as part of stepwise oralfidaxomicin; if neither is cramping, colonic distention (with possible approach, including NAAT plus available, oral metronidazole sepsis, hypotension, ileus, toxic toxin, or GDH plus toxin, or Severe: oral vancomycin or megacolon in fulminant disease), GDH plus toxin followed by fidaxomicin leukocytosis, acute kidney injury NAATwhen results are discordant Fulminant: oral vancomycin, lV metronidazole, and (possibly) vancomycin enema

Clostridioides Diarrhea (gross blood in stool Stool NAAT alone or stool EIA Nonsevere: oral vancomycin or difficile uncommon), fever, abdominal pain/ toxin test as part of stepwise oralfidaxomicin; if neither is cramping, colonic distention (with possible approach, including NAAT plus available, oral metronidazole sepsis, hypotension, ileus, toxic toxin, or GDH plus toxin, or Severe: oral vancomycin or megacolon in fulminant disease), GDH plus toxin followed by fidaxomicin leukocytosis, acute kidney injury NAATwhen results are discordant Fulminant: oral vancomycin, lV metronidazole, and (possibly) vancomycin enema Viral Norovirus Watery noninflammatory diarrhea and 1tr{T, particularly for outbreak None fever; vomiting in >50% of patients; short investigations incubation period and high attack rate Parasitic Giardia Watery "greasy," floating, foul-smelling EIA or NAAT preferred; stool Tinidazole, nitazoxanide, or diarrhea; abdominal cramping, nausea, microscopy for ova and metronidazole steatorrhea, flatulence, weight loss; fever parasites uncommon; postinfection lactose intolerance or IBS Cryptosporidium Watery diarrhea, abdominal cramping, Modified acid-fast stain; direct Nitazoxanide malaise, weight loss fluorescent antibody Effective antiretroviral therapy immunoassay; EIA; NAAT in patients with HIV infection Amebiasis Most asymptomatic; dysentery abdominal Stool microscopy for ova and Tinidazole or metronidazole pain, fever, weight loss; intestinal parasites; stool antigen followed by paromomycin or perforation immunoassay; 11trfT; serologic diloxanide antibodies Cyclospora Watery diarrhea, bloating, flatulence, Mod ified acid-fast stain; Trimethoprim- weight loss, nausea, anorexia, crampy fluorescence microscopy; su lfa methoxazole abdominal pain; sometimes fever NAAT GDFI = glutamate dehydrogenase.

Viral Norovirus Watery noninflammatory diarrhea and 1tr{T, particularly for outbreak None fever; vomiting in >50% of patients; short investigations incubation period and high attack rate Parasitic Giardia Watery "greasy," floating, foul-smelling EIA or NAAT preferred; stool Tinidazole, nitazoxanide, or diarrhea; abdominal cramping, nausea, microscopy for ova and metronidazole steatorrhea, flatulence, weight loss; fever parasites uncommon; postinfection lactose intolerance or IBS Cryptosporidium Watery diarrhea, abdominal cramping, Modified acid-fast stain; direct Nitazoxanide malaise, weight loss fluorescent antibody Effective antiretroviral therapy immunoassay; EIA; NAAT in patients with HIV infection Amebiasis Most asymptomatic; dysentery abdominal Stool microscopy for ova and Tinidazole or metronidazole pain, fever, weight loss; intestinal parasites; stool antigen followed by paromomycin or perforation immunoassay; 11trfT; serologic diloxanide antibodies Cyclospora Watery diarrhea, bloating, flatulence, Mod ified acid-fast stain; Trimethoprim- weight loss, nausea, anorexia, crampy fluorescence microscopy; su lfa methoxazole abdominal pain; sometimes fever NAAT GDFI = glutamate dehydrogenase. r'Empiric treatment, with the final choice of antimicrobial agent guided by in vitro susceptibility testing.

Viral Norovirus Watery noninflammatory diarrhea and 1tr{T, particularly for outbreak None fever; vomiting in >50% of patients; short investigations incubation period and high attack rate Parasitic Giardia Watery "greasy," floating, foul-smelling EIA or NAAT preferred; stool Tinidazole, nitazoxanide, or diarrhea; abdominal cramping, nausea, microscopy for ova and metronidazole steatorrhea, flatulence, weight loss; fever parasites uncommon; postinfection lactose intolerance or IBS Cryptosporidium Watery diarrhea, abdominal cramping, Modified acid-fast stain; direct Nitazoxanide malaise, weight loss fluorescent antibody Effective antiretroviral therapy immunoassay; EIA; NAAT in patients with HIV infection Amebiasis Most asymptomatic; dysentery abdominal Stool microscopy for ova and Tinidazole or metronidazole pain, fever, weight loss; intestinal parasites; stool antigen followed by paromomycin or perforation immunoassay; 11trfT; serologic diloxanide antibodies Cyclospora Watery diarrhea, bloating, flatulence, Mod ified acid-fast stain; Trimethoprim- weight loss, nausea, anorexia, crampy fluorescence microscopy; su lfa methoxazole abdominal pain; sometimes fever NAAT GDFI = glutamate dehydrogenase. r'Empiric treatment, with the final choice of antimicrobial agent guided by in vitro susceptibility testing. Health Care-Associated lnfections Prevention Hand hygiene, performed before and after each patient contact, is the foundation of infection prevention. Standard and transmission-based precautions are practiced with every patient.

r'Empiric treatment, with the final choice of antimicrobial agent guided by in vitro susceptibility testing. Health Care-Associated lnfections Prevention Hand hygiene, performed before and after each patient contact, is the foundation of infection prevention. Standard and transmission-based precautions are practiced with every patient. SIUDY TABLE: Transmission-Based Precautionsu Precaution Type lndications Precaution Examples Airborne Organisms transmitted from Airborne infection isolation Chickenpox (plus contact precautions), the respiratory tract by small room (negative-pressure tuberculosis, measles, SARS-CoV-2 droplet nuclei (S5 pm)that room); HCP wear fit-tested travel long distances on air N95 respirator currents Contact Organisms transmitted by Single room; gloves and gown Multidrug-resistant organisms (such as direct or indirect contact for HC P entering room MRSA, VRE, ESBl'producing gram- negative organisms, CRE), Clostridioides difficile, rotavirus (Continued on the nert page) 248

lnfectious Disease STUDY TABLE: Transmission-Based Precautions" (Continued) PrecautionType lndications Precaution Examples Droplet Organisms transmitted from Single room; HCP wear face lnfluenza, Bordetella pertussis, Neisseria the respiratory tract by large or surgical mask when within meningrtrdls for first 24 hours of therapy, droplet nuclei (>5 pm)that 3 feet of patient mumps travel less than 3 feet on air currents CRE = carb,apenem-resistant Enterobacteriaceae; ESBL = extended spectrum 0 lactamase; HCP = health care personnel; VRE = vancomycin-resistant enterococci. Catheter-Associated UTls Prevention CAUTIs can be prevented by using a urinary catheter only when indicated and removing it as soon as possible. Maintain a closed catheter system at all times, and keep the catheter bag below the level of the bladder. Diagnosis Typical signs and symptoms of UTI may not be present in a catheterized patient. Obtain urine cultures in patients with symptoms attributable to the urinary tract; symptoms <-rr compatible findings plus >103 CFU/mL is diagnostic of infection. \ Treatment If a CAUTI is suspected, remove the catheter. Treat for 5 to 7 days. When culture data are available, treatment should be adjusted to the narrowest spectrum of coverage possible. DOII'T BE TRICKED ! . In patients with a urinary catheter, do not obtain routine urinalysis or cultures and do not treat asymptomatic l bacteriuria. o Don't treat asymptomatic candiduria with antifungal therapy; do remove the catheter. I I i Central Line-Associated Bloodstream lnfection I i i Prevention I Use oflV catheters should be reserved lor patients with a proven need, and the catheter should be removed as soon as clinically I possible. L

DOII'T BE TRICKED ! . In patients with a urinary catheter, do not obtain routine urinalysis or cultures and do not treat asymptomatic l bacteriuria. o Don't treat asymptomatic candiduria with antifungal therapy; do remove the catheter. I I i Central Line-Associated Bloodstream lnfection I i i Prevention I Use oflV catheters should be reserved lor patients with a proven need, and the catheter should be removed as soon as clinically I possible. L t I STUDY TABLE: Prevention Strategies for Central Line-Associated Bloodstream lnfections I Choose. Do not choose... I Maximum sterile barrier precautions and chlorhexidine for skin Routine dressing changes decontamination during catheter insertion t I Subclavian insertion Femoral artery insertion I I L Catheter care teams Routine replacement of central venous catheters I I L I I 1 I 249 I L I