Mycoplasmas, including Mycoplasma and Ureaplasma species, are free-living, self-replicating, small microorganisms classified as Mollicutes.¹ Mollicutes have eight genera and over 200 known species identified from humans, plants and animals.² In humans, mycoplasmas occur on the epithelial surfaces of respiratory and urogenital tissues.³ They infect the phloem sieve in plants⁴ and are found on mammary glands and serous membranes in animals.^3,5 Mycoplasma and Ureaplasma spp. cause symptomatic and asymptomatic infections. In humans, urogenital Mycoplasma and Ureaplasma usually cause asymptomatic infections and coexist with other sexually transmitted infections (STIs).^6,7 They are transmitted through direct genital contact, and if untreated, may result in chronic and acute non-gonococcal urethritis (NGU) in males⁸ and ectopic pregnancy, cervicitis, infertility and pelvic inflammatory diseases (PIDs) in women.^8,9,10 Mycoplasma pneumoniae is the most common pathogen among mycoplasmas and the only respiratory mycoplasma thus far. It causes community-acquired pneumonia (CAP), mostly in children, accounting for 41.1% of paediatric CAP cases.^11,12,13 Mycoplasma and Ureaplasma infections are not fully explored. Therefore, a bibliometric study will help unpack the patterns and gaps in this topic and possibly predict prospects for future research.

Bibliometric analysis uses bibliographic data and statistically assesses published papers to detect and understand their connections.¹⁴ Furthermore, this analysis can examine patterns and developments in the field of research. This method traces the conceptual history of a particular area of study and predicts upcoming trends. In addition to making huge dataset analysis easier, it enables carrying out a more systematic literature study, gathering data and spotting trends. By considering what has been effective in previous papers, these data can be utilised to enhance the quality of future documents. Ultimately, it can potentially enhance the discoverability of research papers.

Bibliometric analysis on various infectious diseases has been done to predict the patterns and burden of infections globally. Although Mycoplasma and Ureaplasma spp. have been reported for years, to our knowledge, no bibliometric analyses have been undertaken. Therefore, this study presents the first bibliometric analysis on Mycoplasma and Ureaplasma infections. The study’s main objectives were to evaluate the global research trends of available literature on Mycoplasma and Ureaplasma infections over three decades. To achieve this, we analysed (1) the annual number of publications, (2) the total and mean number of citations, (3) the most influential sources, and (4) the most frequently used keywords using conceptual mapping.

We analysed bibliometric data on ‘Mycoplasma and Ureaplasma infections’ from 1992 to 2022. Genital mycoplasmas, particularly M. genitalium, are considered clinically important as they cause various STIs and, if left untreated, can lead to serious reproductive health complications in both men and women and adverse pregnancy outcomes. Most developing countries have a high burden of human immunodeficiency virus (HIV) infections.

Therefore, if genital Mycoplasma and Ureaplasma infections are not investigated and treated, this may lead to an increased risk of HIV transmission and acquisition.

Furthermore, we created visual representations of the trends and current insights on the research topic. These findings could be a point of reference and recommendations for future studies related to Mycoplasma and Ureaplasma infections. We looked at the main information extracted from the 19 486 documents. We documented a continuous increase in publications since 1992, with a notable growth in the early 2000s, likely because of the adoption of molecular diagnosis rather than culture and increased awareness. The increase in publications observed in the last 2 years of the study period (2021–2022), with more than 1200 documents published annually, suggests recent intensification of research efforts in this field, likely driven by improved molecular diagnostics, heightened awareness of atypical and co-infecting pathogens, increasing research funding and broader global interest in infectious disease surveillance.

Citations and other research outputs in this research topic increase by 4.2% annually, indicating moderate and steady growth. The top three contributing countries based on publications were the United States (n = 18 099), China (n = 9288) and Japan (n = 4652) (Figure 3). These countries also received more citations than other countries.

The United States’ emergence as the leading country in Mycoplasma and Ureaplasma infections likely indicates a significant study focus because it has more resources and research funding. Moreover, the United States has funding that directly supports multicentre research activities on STIs, including genital mycoplasmas.²¹ Such advantages increase literature visibility, which does not necessarily translate to prevalence. The US government invests in STI research,²¹ as opposed to middle-income and especially low-income developing countries (commonly sub-Saharan African countries like South Africa), where funding is limited, and research depends on aid from other countries.^21,22 Possible reasons for the United States’ predominance in citations include (1) more research outputs and consequently citations, (2) prestigious research institutions, which may influence the number of citations by receiving more attention, most probably because of quality and groundbreaking research outputs, (3) major database indexing that covers mainly journals from high-income countries. Poor scientific production rates in developing countries may be because of the lack of sustainable funding, lack of resources and infrastructure, few collaborations and insufficient government investment in such research initiatives. In South Africa, 685 publications and 2031 citations were reported since 1992. While this reflects a considerable research activity, the relative citation impact suggests low international visibility in comparison to countries with apparent global impact and visibility. Factors such as diagnostic challenges and no routine surveillance may reduce clinical awareness, as well as the journals where research work is published, which might contribute to the low productivity and citations in developing countries.²³ South African data on Mycoplasma and Ureaplasma infections are published frequently in the Southern African Journal of Infectious Diseases, Sexually Transmitted Infections: Journal of Applied Microbiology and The Journal of Infection in Developing Countries. This is likely the barrier to the production and citations observed in South Africa.

Mycoplasma and Ureaplasma infections can be asymptomatic, which may add to the topic’s unpopularity because of low diagnosis records. Nevertheless, citations in this research field are quite impressive. The most cited documents (n = 731) with a mean TC of 30.04 per document were produced in 2015. These citations could have been driven by Mycoplasma outbreaks, particularly for M. pneumoniae, which occur seasonally every 3–7 years.^24,25 Publications between 2004 and 2010 were quite low compared with those after 2020. However, citations between 2004 and 2010 were high, while TC post-2020 were low. As expected, given the increasing annual publication count after 2010, the mean citations per year may also increase as more work is done on this topic. China (n = 9288) and the United States (n = 187 078) represented the highest publications globally. This indicates that these two countries are leading performers, as evidenced by their TC rates and overall scientific outputs. Citations are also influenced by collaborations, particularly international ones, which accounted for 19.8% in our study. This is also influenced by publishing in journals with a strong impact and an established reputation.

The dataset of publications on Mycoplasma and Ureaplasma infections is spread across several journals focused primarily on veterinary science, infectious diseases and microbiology. Although journals such as Clinical Microbiology (410), PLOS One (391) and Veterinary Microbiology (450) published more documents, the American Journal of Obstetrics & Gynecology had the most TC and is the most influential in our research topic. A similar trend was also observed in an American journal, the Journal of Proceedings of the National Academy of Sciences of the United States (US), which produced 6474 citations from 56 documents since 1993. The Journal of Acta Obstetricia et Gynecologica Scandinavica presented the lowest citations (3013) from the lowest number of publications (59) since 1993. This suggests that articles in this journal do not reach a broader audience of researchers and are therefore less cited or used. Given the evidence that this journal was the lowest in the list and had lower TC than documents, we can safely conclude that the journal was less influential and made fewer contributions to this topic.

Our study analysed documents based on Mycoplasma and Ureaplasma infections as broad terms and did not arrange documents based on anatomical systems or clinical emphasis. This may not give a full representation of non-reproductive infections caused by clinical Mycoplasma and Ureaplasma species. Future bibliometric studies should classify keywords by clinical domains, such as urogenital, respiratory and systemic, to get a full representation of the literature.

Keywords from both veterinary and clinical settings were reported. Veterinary keywords suggest that studies on Mycoplasma and Ureaplasma infections in animals also contribute to the overall growth of this research topic. Nevertheless, keywords in clinical research appear more predominant, as shown in Figure 6. Our analysis of common keyword occurrence indicated that the word ‘infection’ was the leading keyword in this research topic from 1992 (Figure 6 and Table 5-A2 Online Appendix 2). The keyword ‘Ureaplasma urealyticum’, which is a bacterium that infects the genital tracts in humans, was the second most frequently used keyword. This may suggest that clinical Mycoplasma and Ureaplasma infections are the most studied infections. Furthermore, it is not surprising that this word tops the list, as it is the most commonly studied urogenital pathogen in the Mycoplasma family because of its commensal nature in the lower urogenital tract of human adults, mostly females.²⁶ However, these data were from developed countries, particularly countries outside Africa. This is evident because SA was the leading country in Africa with 685 documents between 1992 and 2022 (Table 6-A2 Online Appendix 2).

Moreover, fewer studies on clinical Mycoplasma and Ureaplasma infections were reported in South Africa.

Analysis of collaborative patterns, as shown by affiliations and study populations (Online Appendix 1), revealed that co-citations and high collaboration occurred between authors from America, Europe and Asia. Importantly, this analysis showed no South African authors or institutions, suggesting the lack of international collaborations and less engagement on this research topic, signalling the need for more research and collaborations.

All the top 10 frequent keywords co-occur with one another. The keywords ‘infection, identification, prevalence’ may indicate that most studies focused on the prevalence of these infections. Several investigations have revealed the prevalence of Mycoplasma and Ureaplasma infections.^{7,27,28,29,30,31} Furthermore, keywords such as diagnosis and polymerase-chain-reaction (PCR) suggest that PCR is the most commonly used method for diagnosing Mycoplasma and Ureaplasma.^{27,28,32,33,34} The terms ‘Ureaplasma urealyticum’, ‘association’ and ‘Chlamydia trachomatis’ all imply the co-existence of these infections. This is not surprising, given that Mycoplasma and Ureaplasma infections often co-exist with other STIs, including C. trachomatis.⁷ This observation also suggests a frequent co-infection or overlapping research covering both organisms. Mycoplasma and Ureaplasma spp. usually induce asymptomatic infections and are usually discovered in symptomatic patients with other STIs. Therefore, keywords such as ‘Mycoplasma’ and ‘Ureaplasma’ mostly co-occur with other STIs or STI-causing pathogens. The limitation of the study is that the analysis was solely based on the Web of Science database, which only focuses on peer-reviewed documents, and this may not have included all relevant literature indexed by other databases.

Additionally, the appearance of keywords that focus on antimicrobial resistance, resistance mechanisms and laboratory diagnostics suggests potential issues to be tackled. Therefore, future studies on genital Mycoplasma and Ureaplasma infections must be conducted, looking into specified populations, the emergence of antimicrobial resistance, the prevalence of these infections and finding diagnostic markers that can be used to develop new, rapid diagnostic assays. Some studies can be conducted to identify virulence markers to understand the pathogenicity of these species. These studies will guide the development of effective public health policies, such as screening programmes for high-risk populations and screening partners to prevent the continuous spread of these infections, thus bridging the local research gaps.

According to our bibliometric analysis on Mycoplasma and Ureaplasma infections between 1992 and 2022, there has been a noticeable increase in the amount of literature generated over the years. The key findings of the bibliometric metrics showed increasing publications and citations. This increase in research activity could be predicated on improvements in technology, research funding and increasing collaborative activities.