Microbiology and Immunology

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HHaemophilusAEMOPHILUS

Haemophilusis a bacterial genus. The bacteriain this genus

all share the characteristic of preferring to grow on solid labo-

ratory media that contains blood cells. The blood supplies two

factors that Haemophilusspecies require for growth. These are

X factor and V factor. The utilization of these factors and of

the blood cells causes the destruction of the cells and various

characteristic reactions in the blood agar. Indeed, the name of

the genus arise from these reactions.

Haemophilusare Gram negative in their Gram staining

behavior and are very tiny rods in shape. The bacteria can dis-

play different shapes, and so is one of the types of bacteria

known as pleomorphic bacteria. A hallmark of Haemophilus

species is the formation of small colonies that are described as

“satellites” around colonies of Staphylococcus.

In humans, Haemophilusis a normal resident of the

throat and nose. However, spread of the bacteria beyond these

sites can cause infections.

Haemophilus influenzae commonly infects children,

causing a respiratory infection. This infection typically strikes

those who already have the flu. The bacteria that cause these

relatively severe reactions possess a glycocalyxthat surrounds

the each bacterium. The glycocalyx help thwart the host’s

immune response. Types of Haemophilus influenzae that

cause less severe infections of the ears and the sinuses typi-

cally do not possess the glycocalyx.

Haemophilus influenzaeinfections can spread beyond

the lungs. Spread to the central nervous system can result in an

infection and inflammationof the sheath that surrounds nerve

cells (meningitis). Haemophilus influenzaetype b (which is

also known as Hib) is particularly noteworthy in regard to

meningitis. Hib can cause of fatal brain infection in young

children.

Hib infections were once more common and dangerous.

Now, however, the availability of a vaccineand the wide-

spread requirement for a series of vaccinations early in life has

greatly reduced the incidence of Hib meningitis.

Haemophiluscan also spread to the airway. In that loca-

tion, an infection known as epiglottits can be produced. The

resulting obstruction of the airway in children less than 5 years

of age can be fatal.

Other species of note include Haemophilus aegyptius,

the cause of conjunctivitis (or pinkeye), a very contagious dis-

ease in children, and Haemophilus ducreyi, a sexually trans-

mitted disease that causes genital ulceration.

See alsoBacteria and bacterial infection; Blood agar, hemoly-

sis, and hemolytic reactions

HALOPHILIC BACTERIA•seeEXTREMOPHILES

HANCOCK, ROBERT ERNESTWILLIAM

(1949-Hancock, Robert Ernest William )

English bacteriologist

Robert (Bob) Hancock is a bacteriologist and professor of

microbiology in the department of microbiology and immunol-

ogy at the University of British Columbia (U.B.C.) in

Vancouver, British Columbia, Canada. He is internationally

renowned for his fundamental contributions to the study of

antibiotic resistanceof Gram-negative bacteria, particularly

the antibiotic resistance of Pseudomonas aeruginosa.

Hancock was born in Merton, Surrey, England.

Following his undergraduate education he obtained his Ph.D.

at the University of Adelaide in Australia in 1974.

Postdoctoral training followed at the University of Tübingen

(1975–1977) and at the University of California at Berkeley

(1977–1978). In 1978, Hancock became an assistant professor

in the department of microbiology and immunology at U.B.C.

In 1983, he became an associate professor with tenure, and

became an associate member of the department of Pediatrics

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