Tag: case studies

Case History

A 73 year old man was brought to the emergency room with altered mental status and fever, which developed a few days following a 1-2 day illness characterized by myalgia and diarrhea. He was admitted to the hospital and blood cultures were drawn.

Laboratory Identification

The bottles flagged positive after 12 hours and Gram stain showed small, Gram positive rods (Figure 1). Growth of white, smooth translucent colonies was seen on the blood and chocolate plates, with a small rim of beta-hemolysis on the blood plate (Figure 2). MALDI-TOF confirmed the identification as Listeria monocytogenes.

Figure 1. Gram stain morphology of the colonies growing, demonstrating short Gram positive bacilli.

 

Figure 2. Smooth white colonies growing on the blood and chocolate plates, with a soft rim of beta-hemolysis visible on the blood plate.

Discussion

Listeria monocytogenes is prevalent throughout the environment, and can also colonize the human gastrointestinal tract. Humans are exposed by consumption of contaminated food, particularly soft cheeses, deli meats, and fruit. Listeria can grow at 4C which means it can multiply in refrigerated foods, making even low-level contamination a potential hazard. On gram stain, it is a short gram positive rod which may form chains. In some cases, the rods may be so short as to resemble chains of Streptococci, and with the soft surrounding beta hemolysis, could potentially be confused for Group B Streptococcus. However, Listeria is catalase positive, while Group B Strep is negative. Another characteristic feature of Listeria is the “tumbling motility” on wet prep at 20-25C, or “umbrella motility” in tube agar. Listeria also has the unique feature of manipulating the host cells’ intracellular actin framework, using it to facilitate direct cell-to-cell spread of the bacteria. The main virulence factor is the listeriolysin toxin, which is postulated to permit survival of the organism within macrophages via cytotoxic activity.

Listeria can cause a self-limited febrile gastroenteritis in previously healthy individuals, but typically only if they consume a large inoculum. However, in neonates, the elderly, or the immunosuppressed, it can invade and cause sepsis, meningitis, or meningoencephalitis. In pregnant women, Listeria can cross the placenta and lead to intrauterine fetal demise, premature labor, or neonatal meningitis, as well as the typically fatal condition granulomatosis infantiseptica in which the newborn develops widespread abscesses throughout multiple organ systems. Infection during pregnancy usually happens during the 3^rd trimester, though the effects seem to be more severe with earlier infection.

 Listeria has been cultured from the stool of up to 3.4% of healthy, asymptomatic humans, and so there is little utility in stool cultures for Listeria except for epidemiologic purposes during an outbreak. Infections due to outbreaks of Listeria are far less common than sporadic infections, which comprise 95% of Listeria infections. Additionally, traditional stool cultures are poor at detecting Listeria and selective media is usually required. Blood and cerebrospinal fluid are the preferred sites of culture if there is suspicion for disseminated infection. Meningitis caused by Listeria is unique in that is can cause a lymphocyte-predominant CSF pleocytosis, which may result in confusion for viral meningitis. Additionally, gram stains of the CSF are only positive in approximately 1/3 of patients, so a high index of suspicion needs to be maintained while awaiting final culture results. While antibiotic treatment is not recommended for otherwise healthy patients with febrile gastroenteritis, it is recommended for those with disseminated infection or at high risk of dissemination (i.e. extremes of age, immunocompromised, or pregnant).

 

-Alison Krywanczyk, MD is a 3^rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

Case History

A 5 month old girl was brought to her pediatrician by her mother for redness of the medial canthus of her left eye. There was some associated thick discharge as well. The mother mentioned that her daughter had excessive tearing from the left eye since birth. The pediatrician diagnosed dacryocystitis, and prescribed a course of oral cefdinir. However, the swelling and redness continued to worsen, and the infant began to have low-grade fevers. She was sent to pediatric ophthalmology for a consult, and admitted to the hospital on IV clindamycin. The following day, she was taken to the operating room, where they opened the obstructed nasolacrimal duct and sent the contents for culture.

Laboratory Work-Up

Gram stain and smear: No neutrophils, no bacteria seen.

Routine bacterial culture showed growth of small, smooth and translucent colonies on the chocolate agar only. The colonies had a distinct wet-mouse odor.

Repeat review of the gram stain showed moderate neutrophils, with gram negative coccibacilli both extracellular and intracellular.

Discussion

The gram stain and colony morphology described above are consistent with Haemophilus influenzae. Identification of the organism was confirmed by MALDI-TOF.

Congenital nasolacrimal duct obstruction is a common problem, affecting up to 6% of newborns. The vast majority of cases will resolve without treatment by the time the child is 6 months old. However, complications can arise, include acute or chronic dacryocystitis. Acute dacryocystitis causes swelling, warmth, and erythema with or without purulent discharge. The organisms most commonly implicated are alpha-hemolytic streptococci, Staphylococcus epidermidis, and Staphylococcus aureus. In chronic dacryocystitis, there is purulent drainage from the eye but no other signs or symptoms. The most common organisms isolated in these cases are Streptococcus pneumonia, Haemophilus influenzae, Pseudomonas aeruginosa, and viridans group Streptococci.  Acute dacryocystitis usually requires systemic antibiotics, while chronic can be treated with topical antibiotics. In this case, the infant had clinical features of acute dacryocystitis, but infection with an organism more typically associated with chronic dacryocystitis.

H. influenzae is a gram negative coccobacillus, which grows only on chocolate agar due to its requirement for factors V and X. However, H. influenzae can grow on blood agar if it is growing around an organism that hemolyzes the red blood cells in the media, releasing factor V (i.e. Staphylococcus aureus), a phenomenon known as satelliting.

As illustrated by this case, reviewing gram smears inconsistent with the final culture is an important aspect of quality assurance in the microbiology laboratory. This allows the opportunity to provide continuous feedback to technologists on their technique, and lets us keep track of any trends or common mistakes that may be occurring. In this instance, on review of the gram smear it appears the original reader examined only the very thick portions of the smear, which were uninterpretable. However, by moving out to the edges, neutrophils and bacteria were clearly visible. Feedback was provided to the original reader. The provider was immediately called and notified that a corrected report would be issued; the patient was switched to oral Augmentin based on these results.

-Alison Krywanczyk, MD is a 3^rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

Case History

A 29 year old G2P1 woman presented in labor at 39+2 weeks gestational age. Her pregnancy had been previously uncomplicated. Prenatal infectious disease testing showed that she was negative for HIV and Hepatitis C, but that she was positive for Group B Streptococcus. No test results were available for rubella, VZV, toxoplasmosis, or syphilis.

A term male infant was born shortly afterwards by spontaneous vaginal delivery; the mother received less than 4 hours of antibiotics.  The baby was noted to be covered in petechiae, and in a moderate amount of respiratory distress. A CBC showed thrombocytopenia to 23 K/cmm. The baby was transported emergently to the neonatal intensive care unit, where platelet transfusions were given. Blood cultures were drawn. The baby was started empirically on ampicillin/gentamycin, and the following day, once platelet counts were improved, a lumbar puncture was performed. The cell counts in the CSF were unremarkable. A cranial ultrasound showed scattered bilateral parenchymal calcifications, mineralized vasculature of the lenticulostriate arteries, and a subependymal cyst. Urine PCR testing was positive for CMV.

Laboratory Work-up

• Bacterial Culture and Smear, CSF: No neutrophils, no bacteria. No growth.
• CSF Viral PCR: Negative for HSV and VZV.
• Urine CMV PCR: Positive.
• The placenta was not sent for pathologic examination.

Cranial ultrasound demonstrating scattered parenchymal calcifications.

 

Discussion

Cytomegalovirus is one of the classic “TORCH” infections. TORCH is an acronym for a group of pathogens that can cause in-utero or intrapartum infections:

•                 T= Toxoplasmosis
•                 O= other (syphilis, VZV, parvovirus)
•                 R= rubella
•                 C= CMV
•                 H= HSV

Although these infections share several common signs and symptoms, there are clinically suggestive findings that can help target testing. The combination of thrombocytopenia and intracranial calcifications in this infant raised strong suspicion for congenital CMV. CMV is a member of the herpesvirus family.  It is a double-stranded DNA virus with both a viral capsid and envelope. While most babies born with congenital CMV are asymptomatic (~90%), congenital CMV infection is the main etiology of non-hereditary sensorineural hearing loss. This occurs in up to 50% of symptomatic infants and in 10-15% of asymptomatic infants. Symptomatic infants may be small for gestational age, and can be afflicted by thrombocytopenia, petechiae, intracranial calcifications, chorioretinitis, hepatosplenomegaly, microcephaly, and jaundice. While toxoplasmosis can also cause intracranial calcifications, it does not typically cause thrombocytopenia. Congenital HSV can cause thrombocytopenia, but is not associated with intracranial calcifications.

CMV infection during pregnancy is most often acquired by contact with young children. CMV has the ability to remain latent in the host, and become reactivated at a later time, so pregnancies can be affected by either primary infection or by reactivation of the virus. The risk of vertical transmission is much higher with primary CMV infection (32%) than with recurrent infection (1.4%). Although the rate of vertical transmission increases if the infection occurs later in pregnancy, infections acquired in early pregnancy are more likely to cause symptomatic disease. Treatment for the baby is generally supportive, with antivirals generally used only in symptomatic disease (their utility in asymptomatic infection is debated).

An audiology screen and ophthalmologic exam were both normal in the infant presented here. Oral valgancyclovir was started in addition to other supportive measures.

 

-Alison Krywanczyk, MD is a 3^rd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

Case History

After experiencing increasingly frequent asthma attacks and multiple episodes of pneumonia within the last two years, a 60 year-old woman with a longstanding history of allergic asthma presents to a pulmonologist complaining of increased shortness of breath and cough. The patient reports a history of abnormal lung infiltrates for which she was previously treated with a three month course of azithromycin. A repeat chest CT shows diffusely scattered, nodular, ground-glass opacities which have increased in number since her last CT two year prior. A bronchoalveolar lavage is performed and specimen is sent for bacterial, fungal, and AFB cultures as well as a respiratory virus PCR panel.

 

Laboratory Identification

The bacterial and fungal cultures do not grow any pathogens and the respiratory virus panel is negative. The AFB culture, however, grows beaded, Gram-Positive bacilli which are Auramine/Rhodamine negative and Modified Kinyoun positive. The organism grows well on 7H11, Chocolate, and Buffered Charcoal Yeast Extract (BCYE) agars forming irregular, chalky, white-pink colonies.

The organism is confirmed as Nocardia nova by molecular methods.

Discussion

Nocardia nova is a ubiquitous soil bacteria and one of several Nocardia species known to cause disease in humans. When contracted through traumatic inoculation, Nocardia may cause cutaneous diseases such as a mycetoma, superficial abscesses, or cellulitis. More commonly, however, Nocardia is contracted via inhalation and presents as a chronic, slowly progressive pulmonary infection with cough, shortness of breath, and fever. Complicated pulmonary infections may result in pleural effusions, empyema, pericarditis, chest wall abscesses, or dissemination to the brain and other deep organs. Due to low virulence, Nocardia primarily affects only the immunocompromised but those with pre-existing pulmonary disease are also susceptible to infection.

Nocardia is identified in the laboratory as an aerobic filamentous, beaded, Gram-Positive bacilli demonstrating right-angled branching. Nocardia is also weakly acid-fast and is usually identified by a Modified Kinyoun stain. While Nocardia grows within 3-5 days on blood and chocolate agar, it is often isolated on mycobacterial media or BCYE plates where it forms chalky white to faintly pigmented colonies. Accurate identification and speciation of Nocardia currently requires the use of molecular methods (primarily 16S ribosomal RNA gene sequencing). While many infections are successfully treated with a sulfonamide for 6 months to 1 year, the CDC recommends performing speciation and anti-microbial susceptibility testing on every clinical isolate due to species specific susceptibility profiles and multi-drug resistant strains. Nocardia farcinica, for example, is resistant to many antibiotics including 3rd generation cephalosporins.

 

-Elaine Amoresano, MD, is a 2^nd year anatomic and clinical pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

 

Case presentation

A 12-year-old female is seen in gastroenterology clinic following 2 weeks of abdominal pain. She is an otherwise healthy child with no significant past medical history. Her abdominal pain was diffuse, but it has worsened in the past 5 days and is now localized to the left upper quadrant and is sharp in nature. The pain was severe enough to prevent her from attending school last week. She was evaluated for appendicitis, which was ruled out. The patient was admitted for further management including an upper and lower endoscopy. During the endoscopy procedure, small, mobile worms were visualized in the ascending colon. Two worms were collected and removed for identification (Figure 1).

Figure 1. (A) Small, threadlike worms measuring 5-10 mm. Note pointed posterior tail. (B) Haematoxylin and eosin (H&E) stained cross section of the worm.

Figure 2. Cross section of the worms shows (A) anterior with cephalic inflations of the cuticle (arrows) and (B) a long pointed tail.

Figure 3. Internal eggs are 50-60 µm x 20-30 µm in size. They are elongated, flattened on one side, and have a thick colorless shell.

 

Discussion

The worms were identified as Enterobius vermicularis or pinworm. E. vermicularis is a nematode or round worm. Adult worms are 2.5 mm x 0.1 mm (males) and 8-13mm x 0.3-0.5mm (females). Both male and female worms have cephalic inflations of the cuticle at their anterior end (Figure 2A, arrows). Males have a wide blunt posterior tail while females have a long, pointed tail (Figure 1, 2B). Our worms were females as internal eggs were found in both worms. The eggs of E. vermicularis are 50-60 µm x 20-30 µm in size. They are elongated, flattened on one side, and have a thick colorless shell (Figure 3).

E. vermicularis infection is very common in preschool and school aged children as well as families and caregivers of infected children. Transmission occurs through the fecal-oral route. Embryonated eggs are ingested and travel to the small intestine. Adult worms reside in the colon. Gravid females migrate to the anus and deposit eggs onto the perianal area during the night. A single female can deposit as many as 10,000 fertilized eggs. Larvae within the eggs develop and become infective as quickly as 4-6 hours after they are deposited. The entire life cycle from ingestion until eggs are laid by a gravid female in the perianal area is 1-2 months. Perianal scratching and autoinfection are common as well as infection from contaminated fomites such as bedding, clothes, and shared toys.

The most common method of E. vermicularis detection is the Tape Prep method. Briefly, transparent (unfrosted) tape is used to touch the perianal region, after which the tape is placed on a glass slide for microscopic examination. The best time to detect E. vermicularis is 2-3 hours after the patient has gone to sleep due to the nocturnal cycle of the gravid females. Because E. vermicularis does not enter the stool stream, ova and parasite examination often fails to detect the parasite and is not recommended.

Discovery of E. vermicularis in our patient was an unexpected finding, as our patient had no perianal itching. Asymptomatic detection of E. vermicularis has been described in the past, so this finding is not unique. The patient was given a dose of albendazole and will receive another in two weeks, as the drug has reduced effectiveness at killing the eggs or larval stages of development. Her abdominal pain was attributed to overuse of nonsteroidal anti-inflammatory drugs (NSAIDS) and she is being monitored by gastroenterology outpatient clinic.

 

References

1. Ash and Orihel’s Atlas of Human Parasitology, 5^th
2. Red Book 2015 Report of the Committee on Infectious Diseases, 30^th

 

I would like to thank the staff of the Children’s Medical Center Histology Laboratory for sharing my enthusiasm for parasites as well as sectioning, staining, and taking images of the worms for educational purposes.

 

-Erin McElvania TeKippe, PhD, D(ABMM), is the Director of Clinical Microbiology at Children’s Medical Center in Dallas Texas and an Assistant Professor of Pathology and Pediatrics at University of Texas Southwestern Medical Center.

 

 

 

 

Case History

A 37 year old Indian male presents to the emergency department with complaints of a cyclic fever (102-103°F), chills, fatigue and a severe headache. He denies nausea, vomiting or diarrheal symptoms. His travel history is significant for a recent 2 month vacation to India and he is concerned he has malaria, given his symptoms. He reports no sick contacts or suspicious ingestions during his trip and his other family members are well. On physical exam, he is ill appearing, with dry mucous membranes but has no aversion to light or neck pain. Blood work revealed a normal white blood cell count and elevated liver enzymes (ALT 383 U/L, AST 282 U/L). Blood and CSF were collected and sent to the microbiology laboratory for Gram stain and culture. Additional tests for influenza, viral hepatitis and malaria were performed.

Laboratory Identification

Figure 1. Gram stain from a positive blood culture illustrating large Gram negative rods (100x, oil immersion).

Figure 2. Small, lactose negative colonies growing on MacConkey agar after 24 hours incubation in CO₂ at 35°C.

Figure 3. Green colonies growing on Hektoen enteric agar after 24 hours incubation in O₂ at 35°C.

Within a day of collection, multiple blood cultures were positive for a large Gram negative rods (Figure 1). The organism grew after 24 hours incubation in CO₂ at 35°C on blood, chocolate and MacConkey agars and was lactose negative (Figure 2). The identification by MALDI-TOF was Salmonella group. The isolate was then sent to the public health department for additional testing via molecular typing methods. The diagnosis of Salmonella serotype Typhi was confirmed. Testing for influenza, viral hepatitis and malaria were all negative.

Discussion

Salmonella serotype Typhi is a motile, Gram negative rod that is a member of Enterobacteriaceae family.  Typhoid fever is the cause of serious bloodstream infections in developing countries and the great majority of cases in the United States are identified after recent travel. Clinically, it presents with high fever and headaches, in the absence of gastrointestinal manifestations and causes a more severe illness than other Salmonella serotypes. The infecting organism, of which humans are the only known reservoir, is transmitted by food or drink contaminated with feces or person to person contact and has a low infectious dose. Healthy carriers that are able to asymptomatically shed the bacteria have been documented.

Salmonella serotype Typhi is more commonly isolated from blood rather than fecal specimens and grows well on a variety of media including blood, chocolate and Hektoen enteric agar (Figure 3). The characteristic reaction on a triple sugar iron (TSI) slate is alkaline/acid (K/A, only glucose fermented) with a small moustache of H₂S production at the site of inoculation and no gas production. In addition, a positive lysine decarboxylase reaction helps to distinguish Typhi from non-typhoidal Salmonella subspecies I members. MALDI-TOF mass spectrometry is successfully able to identify the isolate as Salmonella spp., but additional testing must be performed to determine the particular serotypes.

Traditionally, serotyping of the O (somatic), H (flagellar) and Vi (capsular) antigens and applying results to the Kauffmann-White scheme is useful in confirming the diagnosis of Salmonella and defining the serotype name. In the case of Salmonella serotype Typhi, the somatic antigen groups as D1 and the Vi antigen is present. The Vi antigen (heat labile) sometimes masks the identity of the O antigen (heat stable). In these cases, heating the bacterial suspension in boiling water for 15 minutes and repeating the O antigen serotyping yields the correct O antigen. Given the expansion in molecular testing, methods based on identifying the genes responsible for the serotype are gaining favor.

Due to the high mortality rate in untreated cases of typhoid fever, treatment with antibiotics is necessary and given the increasing levels of resistance reported, particularly to ciprofloxacin, susceptibility testing should be performed in all cases of Salmonella serotype Typhi. It is recommended that ampicillin, a fluoroquinolone, trimethoprim-sulfamethoxazole and a 3^rd generation cephalosporin be reported for all typhoid isolates based on the most current M100S-26 CLSI guidelines. Also, in the case of S. Typhi, reporting susceptibilities to azithromycin is encouraged (MIC ≤16 µg/mL S, ≥32 µg/mL R, interpretative criteria based on MIC distribution data).

In the case of our patient, he was started on ceftriaxone and continued to receive this IV antibiotic for seven days after blood cultures became negative. Susceptibility testing showed intermediate results for ciprofloxacin by disk diffusion and azithromycin was found to be susceptible with an MIC of ≤16 µg/mL. The patient has an uncomplicated hospital course and made a complete recovery.

 

-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. Currently, she oversees testing performed in both the Chemistry and Microbiology Laboratories.  Her interests include infectious disease histology, process and quality improvement and resident education. 

 

Case History

A 3-year-old female with no significant past medical history presented to the emergency department 1 day following a provoked dog bite to the right cheek. At home, the bite area was cleaned, but it subsequently developed progressive erythema, swelling, and purulent discharge. Review of systems was otherwise negative. Both the patient and dog were up-to-date on vaccinations. On exam, the patient displayed a 1 cm area of induration with surrounding erythema and actively draining whitish fluid.

Fluid from the draining wound was sent to the microbiology laboratory for Gram stain and culture. On Gram stain, rare gram-negative rods were identified, as well as few polymorphonuclear leukocytes.  The following organism was recovered from culture the next day.

Figure 1: Growth on blood, chocolate and MacConkey agars. Note one larger and one smaller colony morphology growing on blood and chocolate agars.  The organism did not grow on MacConkey agar.

Figure 2. Subcultures of the two distinct colony types. The larger colonies (left) appeared more mucoid than the smaller colonies (right).

Figure 3. Gram stains of the two colony types revealed a small, Gram-negative coccobacilli identified as Pasteurella multocida (right) and a larger, pleomorphic Gram-negative rod identified as Pasteurella canis (left).

Laboratory Work-Up

The specimen was cultured on 5% sheep blood, chocolate, and MacConkey agars. Two colony morphologies emerged on the blood and chocolate agar plates (Figure 1). The organism did not grow on MacConkey agar. Representatives of each colony morphology were subcultured onto 5% sheep blood agar with growth shown in Figure 2. One colony is larger and mucoid (Figure 2, left) while the second is smaller and non-mucoid (Figure 2, right).

MALDI-TOF (Matrix Assisted Laser Desorption/Ionization Time-of-Flight) identified two different species of Pasteurella. Colony Gram stains show P. multocida as small Gram-negative coccobacilli (Figure 3, right) and P. canis as pleomorphic Gram-negative rod (Figure 3, left).

Discussion

The Pasteurella spp. are non-motile, facultatively anaerobic, Gram-negative coccobacilli found in the respiratory tracts of nonhuman mammals, most notably cats and dogs. By current classification the genus includes P. multocida (with 3 subspecies), P. dagmatis, P. canis, and P. stomatis, with P. multocida being the most common human pathogen and species recovered from animals (>70% carriage in cats, >40% in dogs) [1]. The foremost human infection is bite or scratch wound with cellulitis, with rapid development of erythema, swelling, and purulent drainage as observed in this case. Licking may also transmit the bacteria.  Possible associated findings include fever and regional lymphadenopathy. More serious potential infections include osteomyelitis, septic joint, endocarditis, bacteremia, sepsis, and meningitis. Systemic illness typically requires immunocompromise (classically liver disease). The organisms are generally penicillin-sensitive [2].

Key identification features of Pasteurella spp. include oxidase positivity and failure to grow on MacConkey agar, both differentiating Pasteurella from the Enterobacteriaceae. Other common features include and catalase and indole positivity. Unlike other certain fastidious gram negative bacteria (e.g., Haemophilus), Pasteurella grow independently on blood agar without the requirement for hemin or NAD. Of note, Capnocytophaga spp. (also associated with dog bites) also grows on blood and chocolate but not MAC. However, Capnocytophaga require a CO₂-enriched environment and the Gram stain is notably different as they are long, slender Gram-negative rods [1].

This case was notable for a dual Pasteurella infection, an uncommon but previously reported phenomenon [3]. The organisms differed by colony morphology, with P. multocida appearing larger and mucoid (reflecting capsule production) on the blood agar, and P. canis appearing smaller, grey, and non-mucoid. Capsule is a key virulence factor of P. multocida and tends to be associated with more severe infections [4].

The patient was treated with a 10 day course of amoxicillin-clavulanate and has completely recovered.

References

1. Procop, G. W., Church, D. L., Hall, G. S., Janda, W. M., Koneman, E. W., Schreckenberger, P. C., & Woods, G. L. (2016). Koneman’s Color Atlas and Textbook of Diagnostic Microbiology (7th ed.). Philadelphia: Wolters Kluwer.
2. Graevenitz, A., & Zbinden, R. (n.d.). Actinobacillus, Capnocytophaga, Eikenella, Kingella, Pasteurella, and Other Fastidious or Rarely Encountered Gram-Negative Rods. In Manual of Clinical Microbiology, 10th Edition (pp. 574–587). American Society of Microbiology.
3. Holst, E., Rollof, J., Larsson, L., & Nielsen, J. P. (1992). Characterization and distribution of Pasteurella species recovered from infected humans. Journal of Clinical Microbiology, 30(11), 2984–7.
4. Harper, M., Boyce, J. D., & Adler, B. (2006). Pasteurella multocida pathogenesis: 125 years after Pasteur. FEMS Microbiology Letters, 265(1), 1–10.

 

-William Phipps, M.D., 1st year Anatomic and Clinical Pathology Resident, UT Southwestern Medical Center

-Erin McElvania TeKippe, Ph.D., D(ABMM), is the Director of Clinical Microbiology at Children’s Medical Center in Dallas Texas and an Assistant Professor of Pathology and Pediatrics at University of Texas Southwestern Medical Center.