Albert Ludwig Sigesmund Neisser (1855–1916)

Albert Ludwig Sigesmund Neisser was a physician and scientist working in Poland who, in 1879, identified the bacterium that causes gonorrhea. Before Neisser’s discovery, physicians and scientists were unsure of what causes gonorrhea, a sexually transmitted infection, or STI, that typically causes genital pain and discharge in those infected. Using newly available microscopy techniques, Neisser examined genital discharge from patients with gonorrhea and observed the bacteria that eventually became known as Neisseria gonorrhoeae, named in his honor. Beyond discovering the bacterial cause of gonorrhea, Neisser also directed a dermatology clinic in Breslau, Poland, and researched other diseases including syphilis and leprosy. In addition to his discoveries, he also experienced scandals and ethical controversies regarding his research practices, which resulted in the implementation of directives regarding informed consent. By identifying the causative agent of gonorrhea, Neisser enabled future physicians and scientists to develop treatments for a disease that can cause infertility and be passed from mother to child causing serious illness in infants.

1. Early Life and Education
2. Research on Gonorrhea
3. Research on Leprosy
4. Research on Syphilis
5. Controversies and Legacy

Early Life and Education

Neisser was born in a town called Schweidntiz, which as of 2025 is Świdnica, Poland, on 22 January 1855 to Louise Neisser and Moritz Neisser. When Neisser was only a year old, his mother died and his stepmother subsequently helped raise him. According to John David Oriel, a historian and researcher who studies venereology, Neisser’s father was a well-known physician, who was strict, hardworking, and committed to his medical practice. According to Lee Ligon, who wrote a biography on Neisser, he attended elementary school in Münsterberg, Poland, before he started at St. Maria Magdalena Grammar School in Breslau, which as of 2025 is called Wrocław, Poland.

In 1872, while in Breslau, Neisser began attending the University of Breslau, now the University of Wrocław, as a medical student, studying clinical and laboratory medicine. He graduated in 1877 with a medical degree, having completed a thesis on echinococcosis, a disease caused by parasitic tapeworms. After graduating, according to Oriel, Neisser wanted to become a general physician but there were no available positions in the department of medicine at the university. Instead, Neisser took on training at the Royal Dermatological University Clinic in Breslau as well. At that time in Germany, dermatology and venereology were combined as one specialty. Dermatology is the branch of medicine concerning the diagnosis and treatment of skin conditions, while venereology is the branch of medicine concerning STIs. It took Neisser two years to finish his dermatology and venereology training, during which he worked under the direction of physician Oskar Simon.

Research on Gonorrhea

As a physician practicing dermatology and venereology, Neisser dedicated the early years of his career in the late 1870s to the investigation of the disease gonorrhea, including looking for the agent that caused the disease. At the time, some physicians and scientists believed that gonorrhea and syphilis were the same disease, only differing in physical expression. In 1767, John Hunter, a surgeon who worked in London, England, conducted an experiment and concluded that syphilis and gonorrhea were the same illness. According to Hunter, secretions from the body containing what Hunter called venereal poison causes venereal disease in those that come in contact with it. Hunter explains that the only way syphilis and gonorrhea are differentiated is where the site of initial infection occurs. According to Oriel, other physicians and researchers at the time accepted Hunter’s explanation. But in the late nineteenth century, Oriel explains that some researchers began to suspect that gonorrhea was caused by a bacterium because by that time other scientists like Louis Pasteur established the germ theory of disease, which is the idea that many diseases are caused by microorganisms such as bacteria. Another researcher at the time, Robert Koch, studied bacteria extensively, creating laboratory and staining techniques to visualize microorganisms with a microscope. Prior to Koch’s contributions, it was difficult for researchers to demonstrate that a bacterium caused gonorrhea because of the limited microscope and staining techniques available at the time.

In 1879, Neisser used laboratory techniques developed by Koch to visualize gonorrheal discharge under a microscope. In late 1800s, Zeiss microscopes were recognized as top-of-the-line microscopes, which used oil immersion technology to produce a higher-resolution image. Neisser had previously worked with microscopes and used staining techniques while earning his degree in clinical and laboratory medicine. He used a Zeiss microscope to examine slides smeared with the genital discharge of men and women afflicted with gonorrhea.

Neisser observed micrococci, or spherical bacteria, in the samples of discharge. The particular micrococci that Neisser described were not present in samples of discharge taken from people with syphilis, according to Oriel’s description of Neisser’s examination. In 1879, Neisser published his paper “Ueber eine der Gonorrhoe eigentümliche Micrococcusform” (About a Micrococcal Form Peculiar to Gonorrhea) in which he described his methods and findings. Neisser’s findings did not definitively establish that the micrococci he saw caused the disease. It took until 1883 for another researcher, Max Bockhar, to show that inoculating a person with the bacteria that Neisser saw produced the disease. In 1933, scientists named the bacterium that Neisser saw Neisseria gonorrhoeae, after Neisser himself.

Research on Leprosy

In addition to investigating gonorrhea in the late 1870s, Neisser also researched leprosy, a disease that affects the body’s nerves, inner surface of the nose, and skin causing flaking, discoloration, ulcers, nodules, blindness, and nerve damage and paralysis. During Neisser’s time, physicians and researchers attributed the cause of leprosy to factors such as the environment and familial descent. In 1873, physician and researcher Gerhard Henrik Armauer Hansen, who was working in Norway, observed rod-shaped bodies in a leprosy sample, and noted that those bodies could potentially be the cause of leprosy. However, Hansen lacked the microscope techniques to distinguish whether the rod-shaped bodies were bacteria or something else. Then, in 1874, Hansen published a paper in which he surmises a probable relationship between the bodies he saw and the symptoms of leprosy but did not make any definite claims. Just a few years later, Neisser used his laboratory skills to continue investigating leprosy where Hansen had left off.

Neisser went to Norway in 1879 where he observed patients with leprosy and received leprosy tissue samples from Hansen. Back in Breslau, Neisser examined the tissue samples under a microscope, using staining techniques that were new at the time, and found rod-shaped bacteria that Neisser attributed to the cause of leprosy. Neisser went on to publish his findings in 1879, in an article titled “Zur Aetiologie der Lepra” (On the Etiology of Leprosy) in which he declared himself the discoverer of the bacteria that caused leprosy. That led to a dispute with Hansen about receiving credit for the discovery of the cause of leprosy.

After Neisser’s publication, Hansen responded to it with a paper of his own in 1880, which led to a back and forth between both researchers. In Hansen’s paper from 1880, he compiled his findings and research during the 1870s on the rod-shaped organisms in leprosy samples. Then, in 1881, Neisser published “Weitere Beiträge zur Aetiologie der Lepra” (Further Contributions to the Etiology of Leprosy). In that article, Neisser explains that he recognizes that he was not the first to see the bacteria, but that he was the one to note the connection between the bacteria and leprosy, and elaborates that Hansen’s colleagues did not regard Hansen’s discovery with much respect. As of 2025, most researchers recognize Hansen as the discoverer of Mycobacterium leprae, which is the bacterium that causes leprosy. As a result, researchers began referring to leprosy as Hansen’s disease. According to researchers Patrícia Deps and Alice Cruz, the term leprosy holds stigma and perpetuates discrimination. As a result, researchers began referring to leprosy as Hansen’s disease. In 1975, after Brazil officially started using the term Hansen’s disease instead, Deps and Cruz explain that it has helped fight both stigma and discrimination.

In 1882, Neisser’s mentor, Simon, died of stomach cancer, and Neisser rose to fill his position, becoming an associate professor and the director of the University of Breslau Skin Clinic. During the nineteenth century in Poland, it was standard practice for students to assume their mentor’s position when they died or stepped down. Soon after, in 1883, Neisser got married to Toni Kauffmann. In 1892, Neisser moved the dermatology and venereology department to an expansive new clinic building. The clinic contained various facilities including laboratories, areas for lectures, and even a museum.

Research on Syphilis

In the 1890s, Neisser began to research syphilis, and tested a potential preventative method in humans. Syphilis typically begins with a genital sore and then leads to rashes and flu-like symptoms. Afterwards, if a person with syphilis still does not receive treatment they reach the latent stage of syphilis, which is when they have no symptoms for many years, or the symptoms never appear again. However, without treatment the infection can disseminate to the brain, the eyes, and other organ systems. Additionally, the illness can be transmitted from mother to child during pregnancy. The risks of that transmission can be premature birth, blindness, numerous other physical effects, and even death.

During Neisser’s time, there were no effective medications to treat syphilis and physicians did not know the causative agent until 1905 when two scientists identified the cause as the bacterium Treponema pallidum. In the nineteenth century, most physicians considered mercury to be a cure for syphilis and used it as such, though mercury did not actually cure the disease. However, some physicians and scientists were exploring prophylactic measures of disease prevention, which are medical therapies that are given before a person contracts a disease to prevent them from becoming ill if exposed in the future, such as Edward Jenner’s vaccination for smallpox. Jenner researched the disease smallpox in the eighteenth century in England. Jenner performed one of the first vaccinations with positive results in 1796 when he inoculated a young boy with secretions of a sore from a person with cowpox, which is similar to the smallpox but is not as dangerous. Then, Jenner exposed the boy to smallpox again, but the boy did not become ill. That result demonstrated that exposure to certain diseases could ensure that an individual would not fall ill in the future with diseases similar to the one they had been exposed to. Neisser followed a similar framework in the 1890s and attempted to create a vaccine as Jenner had done.

In the early 1890s, Neisser investigated blood serum, or the part of blood that has had all white blood cells, red blood cells, and clotting factors removed, as a prophylactic measure against syphilis. According to the 1898 article, “Was wissen wir von einer Serumtherapie bei Syphilis und was haben wir von ihr zu erhoffen” (What Do We Know About Serum Therapy for Syphilis and What Can We Hope for From It?), Neisser hoped that using the serum of people with syphilis could prevent others from contracting the disease because healing an existing disease is far more difficult than preventing the disease with inoculation. Neisser also explained in the publication that a prophylactic measure, or an inoculation, would be beneficial for people who are likely to be exposed to syphilis such as prostitutes, soldiers, and students. However, Neisser’s experiment used methods that are internationally considered unethical as of 2025.

In 1892, Neisser conducted an experiment to test his prophylactic measure against syphilis on both sex workers and younger children and published his work in 1898, which later received backlash due to ethical concerns. Ultimately, during the experiment, Neisser gave the participants inoculations of blood serum from people with different stages of syphilis, in various ways expecting them to produce an immune system response that could prevent the injected individuals from contracting syphilis if exposed in the future. According to Thomas G. Benedek, a physician and researcher on the history of medicine, Neisser acquired his patients from a hospital that had both female sex workers and children as patients. The sex workers were admitted to the hospital by the police, and the children were there due to other health issues. The first part of his experiment entailed injecting serum just under the skin from people with early syphilis in four people from the ages of ten to twenty-four. That group had either skin conditions or other STIs, but none of them contracted syphilis. Then, Neisser injected serum from people who had various stages of syphilis into four sex workers, but instead of under the skin he injected it into the vein. All four sex workers got syphilis, and the serum might have been the cause of syphilis for two of them. Neisser published the results of his syphilis research study in 1898, declaring that syphilis serum did not have prophylactic properties.

Controversies and Legacy

Neisser’s experiments to discover a treatment for syphilis were met with controversy and ethical questioning from physicians and legal authorities at the turn of the twentieth century. The Royal Prussian Disciplinary Court began a hearing to investigate Neisser’s research methodology on 16 January 1900. During that trial, ten physicians looked over Neisser’s experiment and all of them agreed that Neisser and his assistants did not get informed consent from the participants of the experiment. On 11 August 1900, the disciplinary court fined Neisser and formally reprimanded him for failing to get informed consent. After the trial on 29 December 1900, the Prussian Minister of Culture issued a statement or a directive to ensure all researchers obtained informed consent from participants. Informed consent as described in the decree included not medically intervening, or more specifically experimenting, on minors or people that were incapable of making an informed decision, obtaining clear consent to engage in the experiment from the participant, and informing participants of potential adverse consequences of engaging in the experiment. According to Benedek, that decree was one of the first of its kind, to specifically place regulations regarding informed consent.

Despite the controversy surrounding his research, Neisser was able to continue his research into syphilis, including studying the natural history of syphilis in primates. In 1905, Neisser went to Batavia, Indonesia, which as of 2025, is known as Jakarta, Indonesia. Using over 1,000 primates of varying species, Neisser and his assistants made a number of discoveries in relation to the progression of syphilis in the body. The researchers discovered that infection with syphilis did not produce immunity and it was possible to be reinfected with syphilis. They also learned that syphilis bacteria appear in the blood only a few hours after exposure. Additionally, during his time there, Neisser and his team attempted to create another syphilis immunization that ultimately failed. In 1906, after his trip to Indonesia, Neisser assisted fellow venereologist August Paul von Wasserman in developing a blood test for syphilis. Neisser gave Wasserman the livers and serum from primates infected with syphilis to use in his attempt to create a serology test for syphilis, or a test that could detect if a person had syphilis or not. Wasserman’s assistants used the donated serum in their research, which ultimately produced a successful serology test.

Outside of research, Neisser and his wife adopted a son, and according to researcher Ligon, they also loved the arts. Neisser played the piano, and both collected all forms of art such as sculptures and paintings. Their home was eventually turned into a city museum after Neisser died, but the museum was destroyed during World War II.

Despite Neisser’s controversial career, he continued his work with venerology late into his life and his discovery of Neisseria gonorrhoeae allowed for a better understanding on the causal agent and the disease. According to historian Oriel, Neisser spent the later years of his life raising awareness on how to control the spread of STIs. He advocated for the creation of public clinics, examination of sex workers, and health education. After Neisser initially made his discovery in 1879, other researchers were able to make advancements in the understanding of gonorrhea and its course of infection in humans. In 1911, Neisser received the Gold Medal of the West London Medico-Chirurgical Society for his contributions to venereology as a discipline.

Neisser died on 31 July 1916 in Breslau from sepsis.

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