·
All patients with Candida fungemia should be
treated with systemic antifungals.
Fluconazole has been shown to be an effective agent for candidemia with
equivalence to amphotericin products and caspofungin. For example, Candida glabrata is
typically resistant to fluconazole. Voriconazole is also
active against Candida albicans but has many drug interactions that make it
less desirable against this pathogen. Azoles such as fluconazole and
voriconazole are often less active against C. glabrata and C. krusei. Many practitioners
therefore prefer to initiate treatment with caspofungin or amphotericin
products in a patient with candidemia until the yeast isolate is
definitively identified as C. albicans. Caspofungin and other
echinocandins are gaining popularity due to their broad efficacy against
most yeast isolates and benign side-effect profile. Amphotericin B is
effective in fungemia but frequently causes rigors, electrolyte wasting, and
renal insufficiency. Newer lipid formulations mitigate these effects to
varying extents.
·
Dirofilaria
immitis, the dog heartworm, usually presents as a
solitary, noncalcified pulmonary nodule in humans. Because humans are an
unsuitable host for this worm, larvae that mature in subcutaneous tissues after
inoculation by infected mosquitoes enter veins and travel to the heart and act
as emboli into the pulmonary arteries, resulting in infarcts.
·
The differential diagnosis for nodular
adenitis includes Sporothrix schenckii, Nocardia brasiliensis,
Mycobacterium marinum, Leishmania braziliensis, and Francisella tularensis and
is based on direct inoculation of organism due to contact from the soil, marine
environment, insect bite, or animal bite.
·
HACEK endocarditis is typically subacute, and
the risk of embolic phenomena to the bone, skin, kidneys, and vasculature is
high. Vegetations are seen on ~85% of transthoracic echocardiograms. Cure rates
are excellent with antibiotics alone; native valves require 4 weeks and
prosthetic valves require 6 weeks of treatment. Ceftriaxone is the treatment of
choice, with ampicillin/gentamicin as an alternative. Sensitivities may be
delayed due to the organism’s slow growth.
·
Vibrio vulnificus
is a ubiquitous, invasive, gram-negative rod found in warm, salty, coastal
waters. It is found in zooplankton and shellfish and has been associated with
two disease syndromes: (1) sepsis in alcoholics
and persons with liver disease and (2) wound
infections from minor abrasions and/or lacerations. Advanced cases can
result in necrotizing vasculitis and gangrene.
It causes overwhelming
sepsis in the immunocompromised host, particularly cirrhotic patients.
Modes of infection are direct wound inoculation or ingestion via raw seafood.
Presentation is rapid with the classic skin findings described in this
case, which approximate purpura fulminans as the illness progresses. Mortality
is >50%, even with appropriate and early antibiotics.
·
SID (selective
intestinal decontamination), generally accomplished with fluorinated
quinolones, suppresses gram-negative bacteria but not gram-positive bacteria.
Therefore, patients on SID may have an increased frequency of gram-positive
organisms as the etiology for SBP episodes.
·
HCV Dx: HCV RNA
(PCR) > Anti-HCV (RIBA) > Anti-HCV (EIA)
·
The adherence of
HAART necessary to secure durable viral control (95+%) is beyond many people's abilities.
·
Two types of
resistance assays of HAART are available: genotypic resistance tests
and phenotypic resistance tests. Genotypic tests are more readily
available at this time. They involve sequencing HIV viral genes (i.e., reverse
transcriptase, protease) and identifying mutations associated with drug
resistance. Phenotypic tests assess the virus's ability to
replicate in the presence of different concentrations of antiretroviral
medications.
·
Clinically significant thrombocytopenia
indistinguishable from that seen in idiopathic thrombocytopenic purpura (ITP) may be a presentation of HIV infection.
Typically, bone marrow is normal with adequate numbers of megakaryocytes. The
disorder behaves much like classic ITP in that patients respond to steroids and
splenectomy. An HIV antibody test is recommended in patients presenting with
ITP. Of interest is the recent recognition of thrombotic thrombocytopenic
purpura in association with HIV infection.
·
Laboratory findings of PCP include hypoxemia with an elevated A-aO2 gradient. Elevated serum lactate dehydrogenase levels are
seen.
Atovaquone is an alternative oral therapy for
mild-to-moderate PCP (PO2 > 60 mmHg, A-a O2 gradient < 45 mmHg) in
patients who cannot tolerate TMP-SMX. However, it is less effective than
TMP-SMX, although equally as effective as pentamidine. The dosing regimen with
the oral suspension is 750 mg twice daily, taken with a fatty meal, usually for
21 days. Because absorption depends on food intake, more acutely ill patients
are not candidates.
·
Three drugs have been approved for prophylaxis against MAC: rifabutin,
clarithromycin, and azithromycin.
·
Paradoxical
reactions during TB treatment are defined as transient worsening or appearance of new signs, symptoms, or
radiographic manifestations of TB that occur after initiation of treatment and
are not the result of treatment failure or a second process. Such reactions
were seen prior to the HIV epidemic and are still seen in HIV-negative TB
cases, although they are rare. Paradoxical reactions have been reported in up
to 35% of HIV/TB cases. Most
reactions are also associated with the initiation
of antiretroviral therapy, usually within days or weeks. They are most
common in patients with advanced (CD4 < 50) AIDS.
Common manifestations include: fever, new or increased adenopathy, new or
worsening pulmonary infiltrates, and serositis, such as pleural effusions.
·
Immune reconstitution
inflammatory syndrome IRIS: This syndrome is analogous to paradoxical reactions in TB treatment. In
the setting of effective antiretroviral therapy, there is a rapid control of
HIV viral replication and subsequent improvements in CD4 cell count and
function. This immune reconstitution may then lead to inflammatory
responses to clinically known or subclinical opportunistic infections.
Most commonly seen is lymphadenitis due to MAC, the paradoxical reactions in
TB, and exacerbations of cryptococcal meningitis and CMV retinitis. The more
severe reactions, such as meningitis and retinitis, may result in
administration of steroidal therapy.
·
Besides KS and non-Hodgkin's lymphoma, An additional AIDS-defining malignancy is invasive
cervical cancer. Although not specific to HIV infection, it appears
the clinical course is more aggressive in advanced HIV infection. All
HIV-infected women need to receive routine screening for cervical cancer. Human
papillomavirus (HPV) is involved in practically all cases of cervical cancer.
Other non-AIDS-defining malignancies seen more frequently in HIV infection
include Hodgkin's disease, anal cancer (also associated with HPV), lung cancer,
and testicular cancer.
·
Many patients with HIV experience a distal sensory polyneuropathy. This may be due
to HIV itself or treatment of HIV with certain neurotoxic nucleoside analogs,
most commonly zalcitabine, didanosine, and stavudine.
·
Progressive multifocal leukoencephalopathy (PML)
is a CNS demyelinating disease resulting from infection with JC virus.
·
Pneumococci
do not produce plasmid-mediated penicillinase, but they can develop chromosomal mutations that confer resistance
to penicillin by altering the affinity of the penicillin-binding proteins
in their cell walls.
The pneumococcal polysaccharide capsule is crucial to
virulence. The capsule allows the bacteria to resist phagocytosis by
leukocytes. Although the polysaccharide capsule is the critical factor in
determining the virulence of the pneumococci, several proteins, including surface protein A, contribute to the
pathogenesis of pneumococcal infections.
In patients
with pneumococcal pneumonia, a bronchopneumonic
pattern is radiographically more common than lobar consolidation.
Cigarette smoking is the strongest independent risk
factor for invasive pneumococcal disease in immunocompetent adults who are not
elderly.
·
Patients with community-acquired
bacteremias are more likely to have endocarditis
and secondary metastatic infections than patients with nosocomial infections,
who are more likely to have an evident portal of entry and severe underlying
diseases.
·
Vancomycin is
less effective than nafcillin for MRSA sensitive to both agents. Daptomycin and linezolid have excellent
activity against van-comycin-intermediate and vancomycin-resistant
Staphylococcus.
·
Teichoic acid
is a carbohydrate antigen in the cell wall of staphylococci. Antibodies to
teichoic acid can be detected in normal human serum. Teichoic acid has no established role in virulence, and
antibodies to this antigen are not protective.
·
There is a strong association between S. bovis and carcinoma of the colon, and any
patient with documented S. bovis bacteremia should be evaluated specifically
for the possibility of colon carcinoma.
·
About 90%
of patients with primary tuberculosis
infection are asymptomatic. Thus,
pleuritis is fairly uncommon, as are the three other potential manifestations
of symptomatic primary infection (atypical pneumonia, extrapulmonary tuberculosis,
and direct progression to upper lobe disease). Patients who are HIV positive, who are immunologically
suppressed, or who are in some way debilitated are at increased risk for symptomatic primary infection.
Different atypical
mycobacteria are sensitive to different antibiotics. For example, M. kansasii responds well to regimens
containing rifampin, ethambutol, and isoniazid,
and M. avium intracellulare complex (MAC)
is most sensitive to the macrolides azithromycin
and clarithromycin.
·
Rifampin
is contraindicated in patients receiving protease inhibitors (PIs). It is also contraindicated in patients
taking nonnucleoside reverse transcriptase inhibitors (NNRTIs) such as nevirapine, delavirdine, and
efavirenz. Rifampin is a potent inductor of the cytochrome P-450 enzyme system,
and reduced levels of both the PIs and NNRTIs can result from coadministration.
Conversely, PIs can raise rifampin concentrations to potentially toxic levels.
·
Prophylaxis
is recommended for close contacts of N.meningitidis
persons. Close contacts are defined
as household members, day care center contacts, and
anyone directly exposed to the patient's oral secretions (as might occur
through kissing, via mouth-to-mouth resuscitation, during endotracheal
intubation, or during endotracheal tube management by health care workers not
wearing appropriate masks). The likelihood of contracting invasive disease from
close contacts is highest in the first few days after exposure.
·
A typical finding of clstridial myonecrosis is
the absence of a prominent inflammatory response.
·
Metronidazole
is the drug of choice for B. fragilis brain
abscess because of its excellent penetration into the central
nervous system and its virtually universal activity against Bacteroides
species.
·
Antibiotics are the mainstay of therapy for Actinomyces infections, and penicillin is the
drug of choice. Daily doses of Penicillin G 10
to 20 million units are usually administered intravenously for a
period of 2 to 4 weeks, followed by oral therapy for 3 to 6 months.
·
It has repeatedly been demonstrated that single-dose penicillin therapy for early symptomatic
syphilis is more likely to fail in an
HIV-infected patient than in a patient with syphilis alone.
HIV-infected patients have higher rates of false
positive nontreponemal serologic test results.
·
Recent studies have suggested that treatment
with antibiotics and antimotility agents is actually associated with an
increased risk of developing HUS,
especially in children. Thus, it is important to identify serotype O157:H7 in patients with the appropriate
clinical picture; careful monitoring and supportive care is warranted in these
patients. If requested, identification of the causative organism can be
accomplished in most laboratories because this
serotype ferments sorbitol slowly (unlike most other E. coli
strains), allowing its identification on specific indicator plates.
·
V. vulnificus
can cause overwhelming sepsis in compromised individuals. Patients particularly
at risk are those with chronic liver disease or iron-overload
states. Hemorrhagic bullous skin lesions are characteristic. Patients
need not have diarrhea that would be expected with V. cholerae. Another
clinical syndrome associated with V. vulnificus is that of local wound
infection that progresses to fasciitis.For treatment, the drug of choice is tetracycline, with or without cefotaxime. With
bacteremia, the mortality is over 50% despite
appropriate antibiotic therapy.
·
Fever and abdominal pain
are characteristically absent in patients
with V. cholerae infections.
·
IN PERTUSIS,
A single elevated antibody titer should be interpreted in relation to
age-matched, population-specific controls. Paired
specimens have limited utility because a rapid amnestic response
to infection usually precludes the detection of a significant rise in antibody
concentrations between acute and convalescent sera.
·
Brucella
is a slow-growing organism that can be recovered from blood or bone marrow
aspirates; the laboratory that performs the tests should be informed that
Brucella is suspected, in order that the laboratory may keep blood cultures for
21 days.
·
Bacillary
angiomatosis is an infection with B. henselae that primarily
involves the skin and lymph nodes; it is
often seen in patients with AIDS whose CD4+
T cell count is less than 100 cells/µl. Cutaneous lesions are produced by areas
of neovascular proliferation associated with the inflammatory response to the
bacteria. Lesions appear in crops and can have a papular, verrucous, or
pedunculated appearance. They are typically red to purple and are difficult to
distinguish from Kapsosi sarcoma.
Regional lymphadenopathy is common. Systemic disease involving the liver,
spleen, and bone also occurs. Peliosis hepatis
is a characteristic finding in the liver and appears as hypodense lesions on
abdominal CT. Treatment with erythromycin or doxycycline usually results in
rapid improvement; this treatment should be continued for 2 months. Relapses
are frequent after discontinuance of therapy, and some patients need lifelong
treatment with tetracycline or a macrolide for disease control.
·
The distinction between gonococcal and
nongonococcal arthritis is clinically useful, because gonococcal infections tend to have a better prognosis
than nongonococcal arthritis. Progressive joint damage is uncommon
in gonococcal arthritis.
Also,
crystal arthropathy and septic arthritis may coexist; thus, the presence of
crystals does not rule out septic arthritis, and cultures
should be obtained when there is a clinical suspicion of septic arthritis
or when a regimen of intra-articular corticosteroid injections is planned.
·
The lumbar
region is most frequently involved in pyogenic
hematogenous osteomyelitis. Thoracic
vertebrae are often infected in spinal tuberculosis (Pott
disease). The cervical spine
is often the site of infection in patients who abuse I.V.
drugs. Vertebral osteomyelitis is almost always the result of
hematogenous seeding.
·
The absence of rash in RMSF does not correspond
to milder disease; a small percentage of patients with so-called spotless RMSF have fatal illness. Doxycycline
is the preferred agent in all patients except pregnant women, for whom chloramphenicol
remains the agent of choice.
·
Antihistamines
are not indicated in Acute Bacterial Sinusitis, because they thicken secretions
and impair drainage. Nasal decongestants, such as pseudoephedrine, are a
mainstay of therapy
·
The following four clinical criteria have been proposed as suggestive of group A streptococcal pharyngitis: tonsillar
exudates, tender anterior adenopathy, absence of cough, and history of fever.
·
A new approach for Uncomplicated
Otitis Media that merits study is a delayed-therapy
strategy, in which an antibiotic is prescribed when otitis media is
diagnosed, but the parents of the child are encouraged to fill the prescription
only if the child's condition has not improved after 72 hours. Clearly, antibiotics do have a role in management
of this common condition.
·
Lemierre syndrome
occurs most commonly in children and young adults and is characterized by
septic thrombophlebitis of the internal jugular vein,
septic pulmonary emboli, and anaerobic bacteremia. It is typically
caused by Fusobacterium necrophorum.
Lemierre syndrome starts as pharyngitis with invasion into the deep pharyngeal
tissue; this allows drainage into the lateral pharyngeal space and subsequent
thrombosis of the internal jugular vein. CT scanning of the neck can lead to a
diagnosis of thrombosis (ultrasound can also be used); blood cultures are
important in identifying the pathogen. Penicillin G, metronidazole, and
clindamycin have been the mainstays of therapy, although since the 1970s,
Fusobacterium species have been found to be positive for βlactamase, and
some authors recommend using antibiotics that are β-lactamase-stable or
antibiotic combinations that include β-lactamase inhibitors. Heparin
therapy has not been conclusively shown to improve outcomes, and ligation and surgical
resection of the internal jugular vein are rarely necessary with adequate
antibiotic therapy.
·
Hyponatremia,
although common in many pathologic lung conditions, is suggestive of Legionella infection.
·
Three
variants of SBP are recognized on the basis of culture and neutrophil counts of
the ascitic fluid. In a strict sense, SBP
is defined by an ascitic fluid with a positive culture and a PMN count > 250
cells/mm3. CNNA has a negative
culture and a neutrocytic ascites (PMN count > 500 cells/mm3). Bacterascites is characterized by a positive
ascitic fluid culture in the absence of neutrocytic ascites (PMN count < 250
cells/mm3). SBP and CNNA are indistinguishable clinically and are managed
identically with antibiotics. Bacterascites in the absence of symptoms is usually
self-limited and can be managed by observation and repeat paracentesis in 48
hours.
·
In patients without
ascites, the omentum
is very much liable to contain intra-abdominal abscesses.
For this reason, paracentesis is usually not helpful in making a diagnosis. Four-quadrant paracentesis is used in the setting
of peritonitis secondary to diffuse bowel disease, trauma, or surgery.
·
Because of the increased incidence of maternal
mortality and premature births, asymptomatic
bacteriuria in pregnant
women is actively sought and is as aggressively treated and followed as
symptomatic infection.
·
Hantavirus : HCPS & HFRS
HFRS clinical disease can be divided into four
phases: febrile, cardiopulmonary, diuretic, and convalescent.
The mortality
from HCPS is about 50%; most deaths are caused by intractable
hypotension and associated dysrhythmia.
The deer mouse, Peromyscus maniculatus, is the reservoir for the Sin
Nombre virus that causes the hantavirus pulmonary syndrome.
·
Parvovirus B19
causes erythema infectiosum (fifth disease)
in otherwise healthy persons, aplastic crises
in persons with hemolytic disorders, chronic anemia
in immunocompromised hosts, and fetal loss
in pregnant women.
·
Human paravaccinia infections result from direct contact with natural animal reservoirs
of these agents; humans are only incidental hosts. Paravaccinia is an infection
that produces lesions on the teats and oral mucosa of calves and milk cows.
When humans are infected by direct contact, so-called milker's nodules develop on the fingers or hands;
these nodules are occasionally associated with lymphadenitis.
·
One manifestation of HTLV-I
infection is adult T cell leukemia (ATL).
Four clinical types have been described: acute,
lymphomatous, chronic, and smoldering. The most common by far is acute
ATL. Acute ATL is characterized by a short clinical prodrome with an average of
2 weeks between the onset of symptoms and diagnosis. The clinical picture is
characterized by rapidly progressive skin lesions, pulmonary infiltrates, and
diarrhea. Patients with acute ATL have abnormal circulating lymphocytes with
little lymphadenopathy. Lymphomatous ATL, the second most common type,
accounting for 20% of cases, presents as lymphadenopathy in the absence of
abnormal circulating cells. Both acute ATL and lymphomatous ATL are associated
with hypercalcemia, not hypocalcemia. The
other major manifestation of HTLV-I infection is HAM.
This is a slowly progressive thoracic myelopathy. At onset, symptoms include
weakness or stiffness in one or both legs, back pain, and urinary incontinence.
On examination, patients characteristically have hyperreflexia,
ankle clonus, extensor plantar responses, and spastic paraparesis.
Cognitive function is generally not impaired.
·
In patients with
long-standing HIV, the CD4+ T cell count will become more predictive of disease
progression than will viral load.
·
The antibiotic of
choice for listerial meningitis is ampicillin (or
trimethoprim-sulfamethoxazole for the penicillin-allergic patient). Vancomycin,
the cephalosporins (e.g., ceftriaxone), and the carbapenems (e.g., imipenem or
meropenem) do not adequately cover Listeria.
·
Appropriate
malaria chemoprophylaxis is the most important preventive measure
for travelers to malarial areas. In addition to advice about the avoidance of
mosquitos and the use of repellants, most visitors to areas endemic for malaria
should receive chemoprophylaxis, regardless of the duration of exposure. In
most parts of the world where malaria is found, including Africa, chloroquine
resistance is common. Pyrimethamine-sulfadoxine is no longer recommended
for prophylaxis because of the associated risk of serious mucocutaneous
reactions. Mefloquine is the
preferred agent for malaria chemoprophylaxis in areas of the world where
chloroquine-resistant malaria is present. Although mefloquine is generally
well-tolerated in prophylactic doses, underlying cardiac conduction
abnormalities and neuropsychiatric disorders or seizures are generally
considered contraindications for mefloquine use. Thus, daily doxycycline taken from the start of the travel
period until 4 weeks after departure from malarial areas would be the best
choice for malaria chemoprophylaxis for such patient.
·
Disseminated
gonococcal infection is the leading cause of bacterial arthritis in
young adults. This disease often starts as an early tenosynovitis-dermatitis
syndrome, which is often followed by a septic arthritis.
·
Dogs are
responsible for 80% of animal bites; organisms include P.
multocida, Eikenella corrodens, and Capnocytophaga canimorsus (formerly called
DF-2). Aeromonas hydrophila is the organism seen in bite wounds from
alligators and other aquatic animals. Rabies is an acute viral disease of the
central nervous system and is transmitted by infected dogs, cats, skunks,
foxes, raccoons, mongooses, wolves, and bats. Pseudomonas
aeruginosa may cause a variety of skin lesions, such as “hot tub folliculitis” and ecthyma gangrenosum.
Vibrio parahemolyticus is an organism found in undercooked shellfish; patients
present with diarrhea.
·
Acanthamoeba castellanii
is associated with contact lens usage.
·
CARDINAL FEATURES
OF BOTULISM
1.
Symmetric descending paralysis (diplopia,
dysarthria, dysphonia & dysphagia)
2.
Absence of fever
3.
Responsive patient
4.
Normal or slow heart rate
5.
Absence of sensory deficits
·
Outbreaks of lymphocutaneous infection due to Sporothrix schenckii have occurred in nursery
and forestry workers who handle seedlings packed in sphagnum moss.
Disease has also been associated with contaminated hay, timbers, and thorny
bushes, such as roses.
·
Bartonella
species’ Infections:
B. bacilliformis: veruga peruana
B. quintana: Oroya
fever (Carrion's disease), trench fever, bacillary
angiomatosis/visceral peliosis, fever/bacteremia, endocarditis
B. henselae: lymphadenopathy,
fever/bacteremia, bacillary angiomatosis/visceral peliosis, cat-scratch
disease, endocarditis
B. elizabethae: endocarditis
B. clarridgeiae: cat-stratch disease
B. vinsonii subsp. berkhoffi: endocarditis
B. vinsonii subsp. arupensis: fever
B. grahamii: neuroretinitis
·
"LADY
WINDERMERE SYNDROME" DUE TO MYCOBACTERIUM AVIUM COMPLEX
- Elderly white women
- No significant underlying disease
- Multifocal, nodular bronchiectasis involving middle lobes and lingula
- Nonsmokers
- Isolation of M. avium complex in low numbers from sputum specimens
·
Koch postulates,
which were actually proposed by Henle, are used to establish a causal
relation between a specific agent and a specific disease:
- The agent must be present in every case of the disease.
- The agent must be isolated from the diseased host and grown in pure culture.
- The specific disease must be reproduced when a portion of the culture is inoculated into a healthy susceptible host.
- The organism must be recovered again from the experimentally infected host.
·
A. hydrophila,
which has the same freshwater habitat as the medicinal leech, Hirudo
medicinalis, may complicate microvascular surgical infections
where leeches are used because of their anticoagulant properties.
No comments:
Post a Comment