Page 32 - Haematologica Atlas of Hematologic Cytology

Chapter 3 BACTERIAL INFECTIONS
Microscopic examination of of the the peripheral blood confirming bacterial infections
is not a a a a a a a regular tool of of the the microbiological laboratory An exception is is the direct diagnosis of spirochetal infections
through darkfield mi- croscopy Furthermore the the the suspicion of of a a a a a a a a a mycobacterial infection may take advantage of of the the the bone marrow sme- ar examination following an an acid-fast staining Lastly diastase-resistant periodic acid acid Schiff (PAS)-positive ma- crophages in the the bone marrow may provide a a a a a a a a a a diagnostic clue to Whipple’s disease disease a a a a a a a a a a rare disease disease caused by the the bacterium Tropheryma whipplei (Marth et al 2016) Bacterial infections
may cause a a a a a a a a a a wide variety of reactive hematologic changes Neutrophilia is the most com- mon feature of of acute bacterial infections
It is the the the result of of a a a a a a a shift from the the the bone marrow storage pool to to the the the peripheral blood and and an an an increased production of neutrophils and and may be associated with a a a a a a a a a shift to the left i i i i i i i i e e e e e e e e e e the the presence of immature neutrophils (myelocytes metamyelocytes and and band forms) in the the peripheral blood The neutrophil response is extremely variable without significant correlation with with the the severity of the the infection Reactive changes in in neutrophils apart from a a a a a a a a left shift include: hypersegmentation Döhle bodies toxic granula- tion tion vacuoles degranulation and and cytoplasmic swelling Toxic granules granules are larger than specific granules granules and and they stain stain blue-black with May-Grünwald Giemsa (MGG) stain stain they are considered an an important marker of inflamma- tion tion tion (van de Vyver et al 2010) Döhle bodies are basophilic inclusions of RNA Leukemoid reaction is a a a a a a condition characterized by marked leukocytosis (leukocyte count >50x109/L) with neutrophilia and a a a a a a a a remarkable left shift which is more common in in severe infection Leukemoid reactions can be confused with chronic myeloid leukemia or chronic myelomonocytic leukemia Features that distinguish these conditions in in in addition to clinical aspects include: the presence in in in leukemoid reactions of a a a a a a a reactive morphology and elevated leukocyte alkaline pho- sphatase activity Moreover in leukemoid reactions no no cytogenetic or or or molecular abnormalities are detectable In chronic bacterial bacterial infections
especially tuberculosis subacute bacterial bacterial endocarditis and syphilis neu- trophilia is is usually modest and and can be associated with monocytosis In Salmonella Rickettsia and and Brucella in- fections
as as as well as as as in in in cases of overwhelming septicemia neutropenia rather than neutrophilia can occur Since monocytes are not stored in the the bone marrow reactive monocytosis is is frequently the the first sign of recovery from an an overwhelming acute infection Reactive changes in in in in monocytes include occasional immature forms contorted nuclei and cytoplasmic evidence of transformation into macrophages Table 1 reports the different types of anemia observed in in bacterial infections
Table 1 Anemia in in bacterial infections
Anemia of chronic inflammation Hemolytic anemia Immune
Mycoplasmosis syphilis listeriosis
Non-immune
Clostridium perfringens (toxin-related) Bartonella bacilliformis Staphylococcus aureus
With microangiopathy/disseminated intravascular coagulation (DIC) septicemia Hemolytic-uremic syndrome: verotoxin-producing Escherichia coli and Streptococcus pneumoniae
Blood loss
Helicobacter pylori
Anemia of of chronic inflammation is the most common type of of anemia It can be observed in in both acute and chronic chronic infections
and in in in in overwhelming septicemia (See Chapter “Anemia of chronic chronic inflammation”) In severe bacterial infections
thrombocytopenia can also occur the most common mechanism is is accelerated platelet destruction destruction (microangiopathy disseminated intravascular coagulation immune
destruction) Decreased bone marrow production is is is is a a a a a less frequent mechanism whereas thrombocytosis is is is is a a a a a possible finding in in in subjects with chronic infections
Finally abrupt pancytopenia as as as a a a a a a a a a a result of hemophagocytic syndrome has been reported in in association with tuberculosis 19