Answer to February 2023 Photo Quiz

Abstract

Read the full article for the answer.

ANSWER TO PHOTO QUIZ

The answer is hypermucoviscous Klebsiella pneumoniae. Klebsiella pneumoniae is a Gram-negative bacillus of the order Enterobacterales and is a well-known human commensal and opportunistic pathogen.

The hypermucoviscous variant was first described in Taiwan in the 1980s and is established in the Asian Pacific Rim (1), but in recent years there has been an increase in reports worldwide (2). It has not only been identified as the causative agent of community-acquired pyogenic liver abscess but has also been linked to cases of pneumonia, endophthalmitis, meningitis, nonhepatic abscess, and necrotizing fasciitis. Bacteremia is a common finding, as it represents the most probable source of metastatic spread of infection (1).

Phenotypically, the colonies display hypermucoviscosity and generate a string longer than 5 mm when stretched with an inoculation loop. This phenotype relates to virulence genes such as rmpA (regulator of mucoid phenotype A) and magA (mucoviscosity-associated gene A) (3). K1 and K2 capsular serotypes are more likely to harbor the hypermucoviscous plasmid (4).

All isolates were identified as K. pneumoniae by matrix-assisted laser desorption ionization–time of flight mass spectroscopy (Bruker Daltonics). Antimicrobial susceptibility testing was performed with MicroScan panels (Beckman Coulter, CA, USA) and showed low MICs of beta-lactams (amoxicillin-clavulanate, ≤8 and 4 μg/mL; cefotaxime, ≤1 μg/mL; cefepime, ≤1 μg/mL; ertapenem, ≤0.5 μg/mL), quinolones, aminoglycosides, trimethoprim-sulfamethoxazole, and colistin. All isolates generated a string when stretched with a loop, and an endpoint PCR demonstrated the presence of the rmpA gene.

The patient was treated with intravenous (i.v.) ceftriaxone throughout her 7-day hospital stay, followed by cefixime at 200 mg every 12 h for another month on an outpatient basis. Two weeks after finishing treatment, the patient returned, suffering from a recurrence of septic arthritis in the same joint. She was treated with surgical debridement and given a 14-day course of i.v. ceftriaxone. After being discharged, treatment continued with oral amoxicillin-clavulanate at 875 to 125 mg for 1 month, but the symptoms of septic arthritis recurred after finishing the antibiotic course.

The first recurrence led her providers to consider the involvement of other factors, such as the patient’s immunity status and a potential lack of source control (1). Transthoracic echocardiogram revealed no abnormalities, blood cultures returned negative, and further testing did not show any immunodeficiency disorder. Our patient received a long course of i.v. ceftriaxone, as she could not be treated with quinolones due to myasthenia gravis. Infection reoccurred despite having received an 8-week course of i.v. ceftriaxone followed by 6 weeks of oral cefixime, resulting in an osteomyelitis of the tibial plateau, ultimately requiring a knee prosthesis.

Increasing reports of hypermucoviscous K. pneumoniae outside the Asian Pacific Rim suggest that it may be underrecognized elsewhere. We should consider it in patients coming from areas of endemicity who show recurrence or a poor response to antimicrobials, hepatic abscesses, or when isolates have a hypermucoviscous phenotype. Early identification may allow clinicians to treat more aggressively, search for potential metastatic infections, and prevent further spread (1, 5).

Ethics statement.

Written informed consent has been obtained from the patient to publish this paper.