Microbiology Case Study: A 90 Year Old Male with Acute Appendicitis

Case History

A 90 year old male is transferred from his nursing care facility to the hospital for management of acute appendicitis. He had acute onset of right lower quadrant abdominal pain the morning prior to admission with fevers, rigors and drenching sweats. Imaging showed ruptured appendicitis with a fecalith surrounded by small pockets of fluid. His past medical history included dementia, heart disease, hyperlipidemia, hypertension, and glucose intolerance. He denied having any prosthetic joints or valves. Blood was obtained for microbiological analysis.

Laboratory Identification

Blood culture bottles flagged positive. Gram stain of the blood culture bottles showed medium to long gram negative bacilli (Image 1). The blood culture media was plated on blood, chocolate, and MacConkey agar. Aerobically, yellow colonies grew on the blood and chocolate agar. The yellow colonies turned red when exposed to 10% KOH (Image 2). Definitive diagnosis of Chryseobacterium gleum was obtained by MALDI-TOF.

Image 1. Gram stain from the blood culture bottle shows gram negative bacilli.
Image 2. Growth of the organism on chocolate agar with addition of 10% KOH solution (circled in black).


Chryseobacterium gleum is a gram negative bacillus. They form yellow colonies that grow on blood and chocolate agar. They rarely grow on MacConkey agar and are non-fermenters when they do grow. Species of Chryseobacterium will turn red with addition of 20% KOH due to a pigment protein called flexirubin. Interestingly, our lab had only 10% KOH and the colonies turned red with this as well. Other key biochemical and physiologic characteristics of Chryseobacterium include being indole and oxidase positive and they are non-motile.

Chryseobacterium species are found in the environment and are usually not part of normal flora, therefore infection requires exposure of the bug to a debilitated patient in order to colonize the respiratory tract. However, infection of other body sites that may or may not have preceded respiratory tract colonization have been reported. These organisms can survive in chlorinated tap water. They are an emerging cause of hospital associated infections. No virulence factors have been studied. Risk factors for infection include immunosuppression, trauma, surgery, burns, foreign body implants and infused fluids. Of note, the patient was thought to obtain his Chryseobacterium bacteremia from his ruptured appendicitis.

For therapy, there are no definitive guidelines due to lack of understanding of resistance mechanisms. These antibiotics have been reported to have potential activity: Ciprofloxacin, rifampin, clindamycin, trimethoprim/sulfamethoxazole and vancomycin (reportedly for C. indologenes). Our patient was given Piperacillin/tazobactam, Ceftriaxone and metronidazole for two days, Cefepime for one day, Vancomycin for a day. Infectious disease recommended continuing piperacillin/tazobactam and starting trimethoprim/sulfamethoxazole and discontinuing vancomycin.

Antimicrobial susceptibility testing was performed and showed resistance to meropenem, aztreonam, gentamicin, and tobramycin. The organism was susceptible to piperacillin/tazobactam and trimethoprim/sulfamethoxazole.


  1. Tille P. Bailey & Scott’s Diagnostic Microbiology. Fourteenth Edition. Elsevier; 2017.
  2. Murray P. Medical Microbiology. Seventh Edition. Elsevier; 2013.
  3. Jain V, Hussain NAFA, Siddiqui T, Sahu C, Ghar M, Prasad KN. Simultaneous isolation of Chryseobacterium gleum from bloodstream and respiratory tract: first case report from India. JMM Case Rep. 2017;4(10):e005122. Published 2017 Oct 16. doi:10.1099/jmmcr.0.005122

-Angela Theiss, MD is a 3rd 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 Associate Professor at the University of Vermont.

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