Serological and molecular detection of Bartonella henselae in specimens from patients with suspected cat scratch disease in Italy: A comparative study

Abstract

Cat scratch disease (CSD) is an infectious disease caused by Bartonella henselae, usually characterized by self-limiting regional lymphadenopathy and fever. Given the low clinical diagnostic sensitivity and specificity of conventional anti-B. henselae indirect immunofluorescence assays (IFAs), real-time polymerase chain reaction (PCR)-based detection of B. henselae is now being proposed as a more sensitive tool to diagnose CSD. Thus, here we have assessed the efficacy of real-time PCR in detecting B. henselae in different specimens from patients with suspected CSD and compared it to that of IFA. From March 2011 to May 2016, at the Microbiology and Virology Unit, Azienda Ospedaliera Universitaria Città della Salute e della Scienza di Torino, Turin, Italy, 115 clinical specimens (56 aspirated pus, 39 fresh lymph node biopsies, and 20 whole blood samples) and 99 sera from 115 patients with suspected CSD (62 females and 53 males between the ages of 3 months and 68 years) were analyzed by both real-time PCR, used in a qualitative way, and IFA (IgM and IgG) for the presence of B. henselae. For 16 patients, serological results were not available due to a clinical decision not to request the test. B. henselae DNA positivity was detected by real-time PCR in 37.39% of patients, while 62.61% of them were negative. Thus, patients were divided into two groups: real-time PCR+ (n = 43) and real-time PCR- (n = 72). Real-time PCR screening of whole blood, biopsies, and aspirated pus revealed B. henselae positivity in 40%, 38.46%, and 35.71% of patients, respectively. When we analyzed samples by IFA, we found the presence of B. henselae in 28 out of 99 (28.28%) patients, of which 11 (11.11%) belonged to the real-time PCR+ group and 17 (17.17%) to the real-time PCR- group. Among the 71 seronegative subjects, 16 (16.16%) were found positive for B. henselae by real-time PCR. Thus, by combining the results of both assays, we were able to increase the percentage of B. henselae positive specimens from 27.27% (real-time PCR) or 28.28% (IFA) to 44.44% (real-time PCR+IFA). Altogether, these findings indicate that the early detection of B. henselae in patients with suspicious CSD through combined real-time PCR and serological analyses can lead to a more accurate diagnosis of CSD, thereby allowing prompt and appropriate disease management.

Clinical Manifestations of Bartonella henselae Infection Among Children

“…B. henselae IgG antibodies are detectable for approximately 22-28 weeks after exposure, while 25% of patients stay seropositive after one year. [16] In our study, serology was a useful test for diagnosing B. henselae infection. The detection of B. henselae DNA by real-time PCR has been presented as an alternative diagnostic test.…”

A Case of Atypical Bartonellosis in a 4-Year-Old Immunocompetent Child

“…Limitations can also derive from the use of PCR tests to detect B. henselae in blood or in tissue biopsies. Despite the fact that reliable results of DNA amplification methods for the identification of B. henselae have been reported [ 12 ], in the same cases of atypical CSD recently described, PCR tests were repeatedly found unable to detect the pathogen [ 13 ]. Finally, the authorization to perform biopsies for histological assessments may be delayed or even denied by the parents of children with a supposed infection.…”

Comparison of Serological and Molecular Assays for Bartonella Species in Dogs with Hemangiosarcoma

“…With so many factors influencing the accuracy of PCR, a broad range of PCR sensitivity has been reported (33–92%), even when testing solely patients with prototypical diseases caused by Bartonella spp. infection, such as endocarditis and CSD [ 14 , 18 ]. A true gold standard test is defined by a sensitivity and specificity of 100%, so the current human reference standard of serology is far from that.…”

“…DNA in their bloodstream or tissues are often seronegative [ 24 , 25 , 26 , 27 , 28 ]. Conceptually, serology also may have poor sensitivity due to the potential for antigenic switching and immune evasion, and poor specificity for active infection since seroreactivity may persist after exposure, despite effective immunological or antibiotic elimination of the infection [ 18 , 20 , 29 ]. Indeed, finding false negative serology in actively infected dogs can be common with other infectious and vector borne diseases, particularly those with an intracellular lifestyle such as brucellosis, leishmaniasis, or fungal diseases [ 30 , 31 , 32 , 33 , 34 , 35 ].…”