Microbiology and Immunology

WORLD OF MICROBIOLOGY AND IMMUNOLOGY Staphylococci and staphylococci infections

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molecules. In 1955 Heinz Fraenkel-Conrat, a protein chemist,

and R. C. Williams, an electron microscopist, took TMV apart

and reassembled the viral RNA, thus proving that RNA was the

infectious component. In addition, their work indicated that the

protein component of TMV served only as a protective cover.

Other workers in the virus laboratory succeeded in isolating

and crystallizing the virus responsible for polio, and in 1960,

Stanley led a group that determined the complete amino acid

sequence of TMV protein. In the early 1960s, Stanley became

interested in a possible link between viruses and cancer.

Stanley was an advocate of academic freedom. In the

1950s, when his university was embroiled in the politics of

McCarthyism, members of the faculty were asked to sign

oaths of loyalty to the United States. Although Stanley signed

the oath of loyalty, he publicly defended those who chose not

to, and his actions led to court decisions which eventually

invalidated the requirement.

Stanley received many awards, including the Alder

Prize from Harvard University in 1938, the Nichols Medal of

the American Chemical Society in 1946, and the Scientific

Achievement Award of the American Medical Association in

1966. He held honorary doctorates from many colleges and
      universities. He was a prolific author of more than 150 publi-
      cations and he co-edited a three volume compendium entitled
      The Viruses.By lecturing, writing, and appearing on television
      he helped bring important scientific issues before the public.
      He served on many boards and commissions, including the
      National Institute of Health, the World Health Organization,
      and the National Cancer Institute.
      Stanley married Marian Staples Jay on June 25, 1929.
      The two met at the University of Illinois, when they both were
      graduate students in chemistry. They co-authored a scientific
      paper together with Adams, which was published the same
      year they were married. The Stanleys had three daughters and
      one son. While attending a conference on biochemistry in
      Spain, Stanley died from a heart attack at the age of 66.

See alsoHistory of immunology; History of microbiology;

Viral genetics; Viral vectors in gene therapy; Virology; Virus

replication; Viruses and responses to viral infection

STAPHYLOCOCCI AND STAPHYLOCOCCI

INFECTIONSStaphylococci and staphylococci infections

Staphylococci are a group of Gram-positive bacteriathat are

members of the genus Staphylococcus. Several infections are

caused by staphylococci. In particular, infections associated

with methicillin-resistant Staphylococcus aureus are an

increasing problem in hospitals.

The name staphyloccus is derived from Greek

(staphyle—a bunch of grapes). The designation describes the

typical grape-like clustered arrangement of staphylococci

viewed under a light microscope. Staphylococci are divided

into two groups based on the presence or absence of the

plasma-clotting enzyme called coagulase. The coagulase-pos-

itive staphylococci consist mainly of Staphylococcus aureus

and the coagulase-negative group consists primarily of

Staphylococcus epidermidisand Staphylococcus saprophyti-

cus. Because the treatment of infections caused by these bac-

teria can be different, the coagulase test provides a rapid

means of indicating the identity of the bacteria of concern.

Staphylococci are not capable of movement and do not

form spores. They are capable of growth in the presence and

absence of oxygen. Furthermore, staphylococci are hardy bac-

teria, capable of withstanding elevated conditions of tempera-

ture, salt concentration, and a wide pHrange. This hardiness

allows them to colonize the surface of the skin and the mucous

membranes of many mammals including humans.

Staphylococcus aureusis the cause of a variety of infec-

tions in humans. Many are more of an inconvenience than a

threat (e.g., skin infection, infection of hair follicles, etc.).

However, other infections are serious. One example is a skin

infection known as scalded skin syndrome. In newborns and

burn victims, scalded skin syndrome can be fatal. Another

example is toxic shock syndromethat results from the infec-

tion of a tampon with a toxin-producing strain (other mecha-

nisms also cause toxic shock syndrome). The latter syndrome

can overwhelm the body’s defenses, due to the production by

the bacteria of what is called a superantigen. This superantigen

causes a large proportion of a certain type of immune cells to

release a chemical that causes dramatic changes in the physi-

ology of the body.

Staphylococci can also infect wounds. From there, the

infection can spread further because some strains of staphylo-

cocci produce an arsenal of enzymesthat dissolve membranes,

protein, and degrade both DNAand RNA. Thus, the bacteria are

able to burrow deeper into tissue to evade the host’s immune

response and antibacterial agents such as antibiotics. If the

infection spreads to the bloodstream, a widespread contami-

nationof the body can result (e.g., meningitis, endocarditis,

pneumonia, bone inflammation).

Because staphylococci are resident on the skin of the

hands, the bacteria can be easily transferred to objects or peo-

ple. Within the past few decades the extent to which staphylo-

cocci infection of implanted devices is a cause of chronic

diseases has become clear. For example, contamination of

implanted heart valves and artificial hips joints is now recog-

nized to be the cause of heart damage and infection of the bone.

Additionally, the ready transfer of staphylococci from

the skin is an important reason why staphylococci infections

are pronounced in settings such as hospitals. Staphylococcus

aureusis an immense problem as the source of hospital-

acquired infections. This is especially true when the strain of

bacteria is resistant to the antibiotic methicillin and other com-

mon antibiotics. This resistance necessitates more elaborate

treatment with more expensive antibiotics. Furthermore, the

infection can be more established by the time the antibiotic

resistanceof the bacteria is determined. These so-called

methicillin-resistant Staphylococcus aureus (MRSA) are

resistant to only a few antibiotics currently available. The

prevalence of MRSA among all the Staphylococcus aureus

that is isolated in hospitals in the United States is about 50%.

The fear is that the bacteria will acquire resistance to the

remaining antibiotics that are currently effective. This fear is

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