Hitch a Sugar to a Protein

The success of the conjugate Hib vaccines has been spectacular. Prior to their introduction, an estimated 10,000 cases of Hib meningitis occurred annually in the United States, which was approximately 1 in 300 children. It was even higher among native Alaskan and American Indian children. Since the widespread use of the vaccine, the disease has nearly disappeared in the United States, with only 40 cases in children under age 5 years reported by the Centers for Disease Control and Prevention in 2014. Thus, bacterial meningitis, once a scourge that killed and damaged too many American children is, for the most part, now a bad memory.

Antibiotic Treatment—Much Better than Nothing

Over the past five decades, many animal experiments as well as clinical trials of antibiotics in humans treated for meningitis have defined the levels of antibiotics that are present in infected meninges and in the blood, thus informing the drug doses necessary to successfully treat the infection. In spite of the different kinds of bacteria that cause meningitis and the availability of various antibiotics to treat it, several basic principles of effective management for all common forms of bacterial meningitis have emerged from the decades of research. As a result of these studies, most children with meningitis in America receive appropriate antibiotic treatment (the correct antibiotic and the correct dose for the correct duration of therapy), and their outcomes are much, much better than the disastrous outcomes of earlier eras.

The Flu and Richard Pfeiffer

For decades, scientists puzzled over which influenza virus was actually responsible for the Russian pandemic. Finally, in 2014, phylogenetic techniques (examining evolutionary patterns of the virus genes) and seroarcheologic techniques (measuring antibodies likely present in people at various points in time) were applied to the question of which virus caused the Russian flu of 1889–1892. Thus, Pfeiffer’s proclamation that his bacillus caused influenza was finally proven wrong. His identification of Bacillus influenzae in the respiratory tract, however, was a major contribution to the scientific understanding of bacterial infections and moved the field of bacteriology forward in allowing other investigators to unearth its full potential as an important human pathogen. Further, in the course of his studies of B. influenzae, Pfeiffer pioneered the field of nutritional requirements of bacteria. Finally, Pfeiffer’s identification of Haemophilus influenzae launched subsequent studies of the causes of bacterial meningitis and initiated in-depth explorations of bacterial meningitis-causing pathogens that ground our concepts of pathogenesis, and guide our management, of the infection.

Meningitis—What Is It?

Before the advent of antibiotics, meningitis was a dreadful infection by any standard; many of its victims were young children, and almost all died, succumbing to the disease from days to six weeks, or sometimes longer, after the onset of their illness. Incredibly, patients occasionally survived but were often left with varying degrees of neurologic damage. Before the first spinal tap, the diagnosis of meningitis was based on clinical signs and symptoms and could be confirmed only by pathologic examination of the brains of deceased patients during an autopsy. Since the advent of the spinal tap, the diagnosis of meningitis rests on examination of the cerebrospinal fluid. Treatment of meningitis depends on which bacteria cause the infection. Helen Keller may be a famous surviving victim of this disease.

A Scientist and a Scientist Walk into a Bar

Since Richard Pfeiffer first spotted his influenza bacilli in the respiratory secretions of patients suffering from influenza during the Russian pandemic, scientists of all stripes have built, one discovery at a time, a monument to understanding how Haemophilus influenzae, as well as pneumococci and meningococci, cause bacterial meningitis. The culmination of these many, diverse efforts is the near disappearance of this dreadful infection, at least in countries that provide vaccines to their young citizens. Earlier, smallpox, diphtheria, tetanus, whooping cough, measles, and polio became almost nonexistent in America because of a tower of scientific knowledge and the use of vaccines that emerged from that knowledge. Now, meningitis is almost there.

Early Treatment—Immune Serum from a Horse

Hope that patients with influenzal meningitis would benefit from treatment with influenzal immune serum, even serum specific to type b, was cruelly dashed. While immune serum had dramatically improved the outcome of patients with epidemic meningitis caused by meningococci, it just did not work against Haemophilus influenzae infection. Dorothy Wilkes-Weiss and Robert Huntington finally rang the death knell to the idea. They concluded that the results of serum treatment of influenzal meningitis were discouraging, with little optimism regarding the possibilities of future work. The use of such serum was experimental, without justification for commercial exploitation.

Finding the Capsule

Pfeiffer’s bacilli had baffled scientists since Richard Pfeiffer first discovered them. Their morphologic characteristics kept changing. When viewed under the microscope, the bacteria from culture plates sometimes appeared as cocci (tiny berries) and sometimes as bacilli (tiny ovals); the oval shapes varied in their thickness so that they sometimes were fat like tiny chicken’s eggs, other times skinny like grains of rice. Further, the bacteria in spinal fluid specimens were often elongated into threads. Sometimes the thread-like forms absorbed Gram stain most intensely on their ends, sometimes not. Thus, unlike other bacteria, they were not uniform in appearance, which made their identification from clinical specimens difficult and interfered with understanding their nature and clinical implications. All strains, however, either from the meninges or from the respiratory tracts of patients with meningitis, caused infection when injected into guinea pigs and mice, while only strains from the meninges were pathogenic in monkeys and rabbits. The only consistent feature of the bacteria was their requirement for blood—horse, pigeon, human, or rabbit, but not sheep, blood—to grow. Someone needed to sort out all that confusion.

On Immunity

During the late 1800s and early 1900s, a war of words raged among physicians and scientists regarding the nature of immunity: Some supported the so-called cellular theory and others the serum, or humoral, theory. Considerable laboratory research was mounted by scientists on each side to refute the findings of those on the other. The two camps on immunity, the cell theory people and the serum (or humoral) theory people, passionately clung to their respective beliefs and sometimes lobbed disrespectful comments, or downright insults, very publicly at each other. Ultimately, both theories, the killing power of serum and the phagocytic activity of the leukocytes, were recognized to be operative in immunity because they work together to facilitate a rich, complete, albeit complex, immune response.

Epilogue

The spring day we began our search for Richard Pfeiffer in Lądek Zdrój, Poland, was warm and sunny, Several windows of the house were open; their dainty lace curtains fluttered like dove wings in the breeze. In the days when Pfeiffer lived there, we would have heard his piano music—likely he would have played Chopin—wafting from behind those curtains. There, on the other side of the second floor windows, was where Pfeiffer was forced to live when the Polish troops occupied his home. His days at Heimatsonne had been a peaceful ending to Richard Pfeiffer’s productive life, a chance for him to reflect on his important additions to the understanding of microbes, on the miracle of living things, on the beauty of scientific inquiry. He, as much as anyone, had known the rewards of discovery.

Keeping DNA Out, Letting It In

All three meningitis bacteria (meningococci, Haemophilus influenzae, and pneumococci) are able to soak up DNA from their environments; thus, they all exhibit substantial genetic diversity. Those whose cell walls stain Gram negative (meningococci and H. influenzae) use DNA uptake signal sequences to take up the DNA, while pneumococci, which stain Gram positive and thus possess a different kind of cell wall, use a unique and less well understood mechanism. Although these interesting and important scientific discoveries have little to do with the clinical management of meningitis, they reveal a lot about the basic biology of H. influenzae and other meningitis-causing bacteria. By using the molecular tools that permit bacteria to acquire new DNA from their environments, H. influenzae bacteria are able to refashion themselves. In this way, at least a few of the bacteria in the enormous population of bacteria that live in humans are able to cope with whatever challenging environment they happen to fall into, including their transit from the throat, where they normally live, to the blood and meninges, where they cause meningitis.