Pasteurella bettyae is a gram-negative bacillus for which main reservoirs are cats, dogs, other mammals, and birds. P. bettyae has caused infections of the human genitourinary tract (1) and lungs (2) and can be transmitted through neonatal sepsis (3). A recent publication from Spain suggested possible sexual transmission in 2 men who have sex with men (MSM) (4). We describe 9 cases of P. bettyae genital infections in MSM in France during 2018–2022. As required by national ethics regulations, all patients received written information concerning the retrospective use of anonymized data; none expressed opposition to use and publication of those data.

We extracted clinical and biologic data from medical and bacteriology laboratory records. All 9 patients were MSM who sought care at the Hôpital Saint-Louis Center for Genital and Sexually Transmitted Diseases in Paris, France. Patients were 22–58 (mean 41.33) years of age. Seven patients were living in Paris, 1 in a northern suburb of Paris, and 1 in the region north of Paris closest to the city. The average number of sexual partners was 10.4; 2 patients were in monogamous relationships. Six patients did not use protection; 3 used condoms except for oral sex. No patients were HIV-positive, but 1 was immunosuppressed because of a kidney transplant. Two were receiving preexposure prophylaxis (PrEP) for HIV (Table 1).

One patient had a cat, another acknowledged contact with cows 2 weeks before clinical signs appeared, and 2 reported no contact with animals; data were missing for the other 4 patients. The main clinical manifestations were balanitis (4/9, 44.4%) and balanoposthitis (2/9, 22.2%). Balano-preputial sulcus ulcers in 2 patients were ultimately diagnosed as lymphogranuloma venereum and syphilis and urethral discharge in 1 patient was diagnosed as gonorrhea. No other signs or symptoms, including fever or lymphadenopathy, were reported (Table 1).

According to national guidelines, we presumptively treated patients with antimicrobial drugs; those with ulcers received benzathine benzylpenicillin plus doxycycline and the patient with urethral discharge received ceftriaxone plus doxycycline. We targeted co-pathogens when detected by nucleic acid amplification tests. One patient who had not received antimicrobial drugs attended a review visit and recovered after receiving specific treatment (cefixime) (Table 1).

We obtained P. bettyae colonies after 24-hour culture on polyvitex agar (bioMérieux, https://www.biomerieux.com) at <5% CO₂ and 35°C–37°C. We identified P. bettyae using Vitek MS matrix assisted laser desorption/ionization time-of-flight mass spectrometry (bioMérieux). We used disk diffusion (BioRad Laboratories, https://www.bio-rad.com) on polyvitex agar to test antimicrobial susceptibility and interpreted results according to European Committee on Antimicrobial Susceptibility Testing recommendations (5). All P. bettyae isolates showed susceptibility to amoxicillin/clavulanic acid, ceftriaxone, tetracycline, and fluoroquinolones, as is usually observed for this genus. One isolate from patient 9 exhibited resistance to amoxicillin and penicillin G (penicillin G MIC of 0.75 mg/L), 1 from patient 4 to penicillin G only, and 1 from patient 8 to trimethoprim/sulfamethoxazole (Table 1).

We performed whole-genome sequencing and bioinformatics analysis of 6/9 available P. bettyae isolates (BioProject accession no. PRJNA1039245) as described elsewhere (6). We developed the distance matrix of Pasteurella clinical isolates and rooted it by comparison with the genome reference sequence of P. bettyae strain CCUG 2042 (National Center for Biotechnology Information Reference Sequence database accession no. NZ_AJSX01000007.1). We observed relatedness between all P. bettyae isolates (Table 2), highlighting that 4 isolates, from patients 1, 3, 5, and 6, were closely related, varying among them by only 12–270 single-nucleotides polymorphisms and by 587–628 SNPs from the P. bettyae CCUG 2042 strain described in 2012 in the United States. Isolates from patients 4 and 7 were more distant but had ribosomal identification and 16S rRNA of P. bettyae.

The 9 cases of genital P. bettyae infection exclusively in MSM we describe clustered within a 4-year period; no case was registered at our hospital before 2018. Fewer than 50 cases (mainly genital) have been reported worldwide across the previous 60 years, in male and female patients. In this series, the most specific clinical manifestation was balanitis/balanoposthitis. Because only 1 patient received targeted treatment, we could not deduce that P. bettyae was solely responsible for his symptoms or treatment responsible for his recovery. In case-patients with ulcers and urethritis, P. bettyae superinfection was more likely. Only half of patients for whom information was available had contact with animals, which provides insufficient support to determine direct anthropozoonotic transmission. Two thirds of patients reported not using condoms and the remaining third not using them for oral sex, which is not enough evidence to determine the transmission route and preventive efficacy of using condoms. However, if balanitis is indeed the main clinical manifestation, condoms provide an obvious physical barrier. Of note, the first case in this cluster occurred 2 years after PrEP policy implementation in France, but whether receding usage of condoms by PrEP users had any part in this emergence remains speculative.

P. bettyae appears to be an emerging cause of sexually transmitted genital infection among MSM in Europe (3). More case descriptions are needed to delineate its clinical spectrum and appropriate handling. We encourage physicians to test bacterial swab samples when managing similar genital symptoms, especially balanitis.

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Suggested citation for this article: Li A, Herms F, Pataut D, Louison J-B, Cassius C, Merimèche M, et al. Pasteurella bettyae infections in men who have sex with men, France. Emerg Infect Dis. 2024 Jul [date cited]. https://doi.org/10.3201/eid3007.240352