BACTERIA FOUND IN FEMALE GENITAL INFECTIONS

FEMALE BACTERIA INFECTION.

BACTERIA
FOUND IN FEMALE GENITAL INFECTIONS

Streptococci

Many varieties of streptococci have been found in the pelvis, and they have been
classified by two independent schemes. In one scheme, the streptococci are
distinguished by their hemolytic properties on blood agar plates. Aerobic streptococci
showing partial (or green) hemolysis are termed alpha (a) streptococci, those showing
complete (or clear) hemolysis are termed beta (b) streptococci, and those showing no
hemolysis are termed gamma (g) streptococci.

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Group A Streptococci (Streptococcus pyogenes)

Streptococcus pyogenes causes pharyngeal, cutaneous, puerperal, and postoperative
infections and necrotizing fasciitis. Sequelae of group A streptococcal infections may
include rheumatic fever and acute glomerulonephritis. It is not generally considered to
be a member of the normal vaginal flora, as it is isolated in less than 1% of
asymptomatic women. Pelvic infection caused by group A streptococci may produce a
characteristic clinical picture, with a high, early initial fever, chills, prostration, and
diffuse tenderness. Historically, the group A b-hemolytic streptococcus was the
organism responsible for fatal puerperal sepsis. On Gram stains, one sees
Gram-positive cocci in chains. The microorganism remains exquisitely sensitive to
penicillin, and erythromycin or a cephalosporin usually can be substituted for treatment
of the penicillin-allergic patient. Clindamycin is an alternative agent, as is vancomycin.
Group A streptococcal pelvic infections occur in both sporadic and epidemic forms.
Epidemics usually are exogenous in origin, commonly resulting from nasopharyngeal
carriage of the microorganism or from skin infections in hospital staff members.
Occasionally, a mother may be the source.
Epidemics can be prevented by placing patients with group A streptococcal infections in
strict isolation and by early antibiotic treatment of hospital employees with group A
streptococcal infections. Employees with positive cultures should be relieved of duty on
obstetric, neonatal, and postoperative wards until their cultures become negative. When
epidemics have occurred, isolation and antibiotic therapy have not always sufficed to
effect control. In some recent outbreaks, additional measures, such as identifying and
treating all streptococcal carriers, canceling elective surgery, and prophylactic treatment
of all patients and personnel, have been necessary.

Group B Streptococci (Streptococcus agalactiae)

Before the 1960s, GBS were not recognized as frequent pathogens, but they have now
become a major cause of sepsis among neonates and postpartum women. Unlike group A streptococci, group B organisms are considered part of the
normal vaginal flora and can be recovered in about 20% of normal pregnant women.
Isolation rates are enhanced by use of selective broth containing nalidixic acid and
gentamicin. The clinical picture of GBS infection in puerperal women closely resembles
that of group A infection. Epidemic GBS disease has not been reported among mothers,
however. The neonate with GBS sepsis usually acquired the microorganism from the
maternal genital tract. Even with appropriate therapy, early-onset neonatal GBS
infection has a high fatality rate. In 1996, national guidelines were established to prevent
GBS perinatal sepsis

Group D Streptococci

This group is composed of two subgroups: “group D enterococci” and “group D not
enterococci.” The former, which includes Streptococcus faecalis, Streptococcus
faecium, and other less common species, occurs frequently. Although these organisms
cause endocarditis and urinary tract infection, their virulence in genital infections has
been debatable. They are considerably less virulent than group A or B streptococci, but
on occasion they have caused serious genital and abdominal infections. Enterococci are
important pathogens, particularly in situations where cephalosporin prophylaxis has
been used.

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Staphylococci

The aerobic staphylococci include S. epidermidis, Staphylococcus saprophyticus
(Micrococcus), and Staphylococcus aureus. The first two do not produce a coagulase
enzyme (the “coag-negative” staphylococci), whereas S. aureus does (“coag-positive”
staphylococci). Staphylococcus aureus is isolated from 5% to 10% of genital tract
cultures. This organism has been recognized as a cause of abdominal wound infections,
breast abscesses, and nursery outbreaks of infection. It has been isolated from nearly
all patients with toxic shock syndrome. Most species of S. aureus, whether isolated in
the community or in the hospital, elaborate penicillinase and are resistant to penicillin
and ampicillin. Agents of choice for treatment of S. aureus infections are the
penicillinase-resistant penicillins, such as cloxacillin, dicloxacillin, methicillin, oxacillin,
and nafcillin. Resistance to these antibiotics by methicillin-resistant S. aureus has
become a major nosocomial infection problem. Antibiotics for use in S. aureus
infections in the penicillin-allergic patient are the “first-generation” cephalosporins and
clindamycin. Vancomycin is the drug of choice for methicillin-resistant S. aureus.
Staphylococcus saprophyticus has been recognized recently as an important cause of
urinary tract infection. This organism is susceptible to a wide range of antibiotics,
including penicillins, cephalosporins, and trimethoprim-sulfamethoxazole (TMP-SMX).
Staphylococcus epidermidis is commonly isolated from the vagina and skin, but rarely
causes infection. Conditions in which S. epidermidis is recognized as a pathogen
include osteomyelitis, possibly late-onset neonatal sepsis, and association with foreign
bodies and invasive lines.

Gram-Positive Bacilli
The Gram-positive bacilli are common organisms in the normal vaginal flora.
Lactobacillus sp are the most frequent component of the normal vaginal flora in women
of reproductive age. Although lactobacilli are generally nonvirulent organisms, the
strains that produce hydrogen peroxide play a major role in controlling the vaginal flora.
In unusual circumstances, the usually avirulent lactobacilli may produce invasive
disease, such as bacteremia, which occurs in patients with underlying conditions such
as cancer, recent surgery, and diabetes mellitus. Many of these patients received prior
antibiotic therapy. When lactobacilli appear in cultures of the urine, it almost certainly
represents a contamination.
Listeria monocytogenes is present rarely in the vaginas of healthy women. Although the
predominant route for severe intrauterine infections due to this organism during
pregnancy is transplacental secondary to bacteremia, on occasion L. monocytogenes
ascends from the lower genital tract to cause intrauterine infection.
Epidemics due to Listeria organisms have occurred from contaminated dairy products.

Gram-Negative Bacilli

The Gram-negative bacilli include a large number of microorganisms with highly variable
patterns of antimicrobial susceptibility. Many species have been identified, but only a
few are commonly isolated from patients with pelvic infections.

Escherichia Coli

Escherichia coli is one of the most common members of this group isolated in genital
tract and urine specimens. It is present in approximately 70% of urinary tract infections.
Escherichia coli infections usually are mild, but occasionally they may be fulminant, as it
is the microorganism most commonly identified in bacteremic obstetric and gynecologic
patients. Escherichia coli frequently is recovered in mixed infections of the pelvis, such
as amnionitis, endometritis, and posthysterectomy cellulitis. Its susceptibility to
antibiotics varies from hospital to hospital and, probably, from service to service.
Gentamicin, tobramycin, amikacin, and chloramphenicol usually are effective against
more than 95% of E. coli isolates. Increasingly, E. coli resistance to ampicillin has
emerged. In general, more than 40% of E. coli (including community-acquired strains)
are resistant to ampicillin. The first-generation cephalosporin antibiotics have remained
active against E. coli isolates in most hospitals, but the newer cephalosporin agents
(second and third generation) and newer penicillins are more active. The new quinolone
agents, such as ciprofloxacin and ofloxacin, are very active against E. coli, as is
TMP-SMX.

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Gardnerella vaginalis

Formerly known as Haemophilus vaginalis and Corynebacterium vaginale, Gardnerella
vaginalis is found in vaginal cultures of nearly all women with bacterial vaginosis, but it
also can be found in vaginal cultures of 40% to 60% of asymptomatic women when a
selective medium is used. It has been reported to cause endometritis and bacteremia. In
some institutions, G. vaginalis is the most common Gram-negative aerobe recovered
from the endometrium and blood of patients with postpartum endometritis. Gardnerella
vaginalis has been frequently recovered from patients with pelvic inflammatory disease.
Rather than being a pathogen on its own, G. vaginalis probably is involved by
association with other bacterial vaginosis organisms. In vitro testing shows this
organism to be susceptible to ampicillin and tetracycline, but these agents are of limited
value in curing bacterial vaginosis.

Klebsiella Species

Klebsiella sp are found in less than 10% of genital tract infections, but they also cause
urinary tract infections and hospital-acquired pneumonia. Klebsiella pneumoniae is the
most common member of this group recovered from genital tract and urinary tract
infections. Klebsiella oxytocia is much less common. All the cephalosporin antibiotics
are highly effective against Klebsiella organisms, as are the aminoglycosides and
chloramphenicol. Ampicillin has little activity, but some of the newer penicillins, such as
piperacillin and mezlocillin, have improved activity. Quinoline agents are effective, as
are the new enzyme-blocking drugs, such as amoxicillin (Augmentin), ticarcillin
(Timentin), ampicillin (Unasyn), and piperacillin (Zosyn).

Enterobacter Species

Although closely related to Klebsiella species, Enterobacter species are encountered
much less frequently (less than 5% of genital infections). They are more resistant to
antibiotics than are Klebsiella species. Until recently, Enterobacter infections usually
required therapy with aminoglycoside antibiotics, but some of the newer cephalosporins
and newer penicillins show good activity. The most common of this group are
Enterobacter aerogenes and Enterobacter cloacae.

Proteus Species

Proteus sp are isolated in 10% to 15% of genital tract infections and in a similar
percentage of urinary tract infections. Proteus mirabilis, by far the most commonly
isolated species in obstetric and gynecologic patients, is susceptible to ampicillin and
the cephalosporins, as well as the aminoglycosides. Proteus vulgaris occurs much less
commonly. Former Proteus species, Proteus morganii and Proteus rettgeri, are now
classified as Morganella morganii and Providencia rettgeri, respectively. These species
are resistant to ampicillin and the first-generation cephalosporins, but they are sensitive
to the aminoglycosides and some of the newer penicillin and cephalosporin antibiotics.

 

Pseudomonas Species

Opportunistic pathogens in severe, usually hospital-acquired, infections, Pseudomonas
sp are found infrequently in infections in obstetrics and gynecology, but Pseudomonas
colonization is seen commonly in patients receiving antibiotic therapy. Antibiotic
susceptibility is good to gentamicin and usually better to tobramycin and amikacin.
Activity of the newer penicillins and some of the newer cephalosporins is good, and
combinations of antibiotics may produce higher cure rates in serious infections.

Other Gram-Negative Bacilli

Other Gram-negative bacilli include microorganisms such as Serratia, Citrobacter,
Acinetobacter, and Providencia species, all of which show resistance to commonly used
antibiotics. Fortunately, these species are found rarely among obstetric and gynecologic
patients, except in those who are debilitated or who are receiving antibiotic,
immunosuppressive, or cytotoxic therapy.

Gram-Negative Cocci.

In pelvic infections, the only significant member of the Gram-negative cocci is Neisseria
gonorrhoeae, which may produce an asymptomatic colonization of the cervix, cervicitis,
or salpingitis. Disseminated infection with septicemia, arthritis, and
dermatitis occurs not infrequently. Neisseria gonorrhoeae is a common cause of
neonatal conjunctivitis and has been reported recently as an unusual cause of
amnionitis and fetal scalp abscess. Penicillinase-producing strains of N. gonorrhoeae
have become a major problem in the United States. In addition, chromosomally
mediated resistance and tetracycline resistance have emerged in N. gonorrhoeae.
Penicillin is no longer a recommended antibiotic. Cephalosporins or quinolones are
preferred, usually in single-dose regimens, for uncomplicated gonococcal infections.

CHANGES IN VAGINAL MICROFLORA

One should not conclude from this description of vaginal microflora that it is a static
situation. Certainly, there are vast differences in flora between different groups of
women and interesting shifts from time to time in the flora of one particular woman.

Age

At birth, the vagina is sterile. Secondary to maternal estrogen effect, lactobacilli growth
is enhanced for a short time. The estrogen effect is gone within several weeks, and
lactobacilli disappear until the onset of puberty, when, under the influence of
endogenous estrogen, the vaginal flora becomes dominated by lactobacilli. It is
suggested that postmenopausal women have a decrease in Lactobacillus colonization,
but that treatment with estrogens results in a higher rate of recovery of lactobacilli and
probably of diphtheroids. Thus, there seems to be an important interaction between
vaginal colonization and hormonal milieu. Changes associated with aging have been
reported in other groups of bacteria, but the conclusions are less uniform.

Sexual Activity

Sexual intercourse leads to changes in lower genital tract microorganisms, mainly
sexually transmitted ones. In addition to introducing major pathogens such as N.
gonorrhoeae, C. trachomatis, and herpesvirus, intercourse leads to increases in genital
mycoplasmas.

Contraception

Use of oral contraceptives appears to have minimal effect on the vaginal ecosystem. On
the other hand, use of intrauterine contraceptive devices increases the number of
anaerobic bacteria in the cervix and augments the risk for bacterial vaginosis, thus
increasing the risk for pelvic inflammatory disease.

Pregnancy And Delivery

A number of studies have suggested that there is a progressive increase in colonization
by Lactobacillus organisms during pregnancy, but changes in other bacterial groups are
not well established. After delivery, dramatic changes in vaginal flora occur. There are
marked increases in anaerobic species by the third postpartum day. Possible
predisposing features to anaerobic vaginal colonization in postpartum women include
trauma, presence of lochia and suture material, examinations during labor, and changes
in hormonal levels. By the sixth week postpartum, the vaginal flora is restored to a
normal distribution.

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Surgery

Major procedures, such as hysterectomy, lead to wide changes in vaginal flora,
including decreases in lactobacilli and diphtheroids and increases in aerobic and
anaerobic Gram-negative rods (predominantly E. coli and various Bacteroides
[Prevotella]). In addition, most investigators have noted a further shift when prophylactic
or therapeutic antibiotics are used. As expected, use of antibiotics results in a decrease
in susceptible flora and a corresponding increase in resistant organisms.

Homeostasis

Homeostatic mechanisms have been identified that function to maintain the stability of
the normal vaginal flora. Production of hydrogen peroxide by certain Lactobacillus
species appears to play a crucial role in maintaining the normal vaginal ecosystem. In
addition, the low pH (acidity) of the normal vagina protects against exogenous
organisms. Antimicrobial agents can disrupt the normal vaginal ecosystem, especially if
they eliminate the hydrogen peroxide-producing lactobacilli