Viridans streptococci are
usually regarded as
low-virulence alpha-hemolytic streptococci
that commonly colonize the human
oropharynx, gastrointestinal tract, and female genitalia. However,
infection can result in bacteremia and may disseminate to distant
sites in an immunocompromised patient.
Streptococcus pneumoniae is the most commonly
identified pathogen in community-acquired pneumonia. S.
Viridans is not commonly related to community-acquired
pneumonia. Most S. viridans strains are sensitive to
penicillin; nevertheless, the rate of penicillin resistance has
increased steadily worldwide. Herein, we report the case of an
immunocompetent 4-year-old boy who presented with cough,
intermittent fever, and dyspnea attributed to
penicillin-intermediate-resistant S. viridans-related
A 4-year-old boy presented with intermittent
fever and productive cough for 2 weeks. He was given medications to
alleviate the symptoms; however, high fever and shortness of breath
were noted 4 days later. The parents stated that the boy had no
history of aspiration, dental caries, or dental extraction. He had
previously received a four-dose pneumococcal 7-valent vaccination.
There was no history suggestive of food or drug allergy, chest pain,
On initial examination, the patient had fever
with a temperature of 39ºC, a heart rate of 143/min, a respiratory
rate of 28/min, blood pressure of 101/65 mmHg, and oxygen saturation
on room air of 98%. Coarse breathing sounds combined with rhonchi
over the right lung field were audible, and no heart murmur was
revealed by physical examination. No skin rash was found over any
part of the body. The remainder of the physical examination was
The patient’s laboratory studies revealed a white
blood cell count of 8.53 × 103
cells/mm3 with 60.5%
neutrophils, 27.7% lymphocytes, and 11% monocytes; a hemoglobin of
13.3 g/dL; and a platelet count of 275000/mm3.
C-reactive protein was 2.82 mg/dL. Mycoplasma IgM was undetectable
from serum. An influenza rapid test was negative in a sample
isolated from the nasopharynx. Initial chest radiography showed
focal parenchymal consolidations over the right upper lobe.
We prescribed empiric antibiotics with cefuroxime
and azithromycin at first. However, spikes fever persisted over 2
days. Two blood culture specimens grew S. viridans that were
intermediately resistant to penicillin (MIC = 0.5 µg/mL) but
sensitive to ceftriaxone and vancomycin (MIC <0.5 µg/mL in both).
Accordingly, the antibiotics were switched to ceftriaxone (600 mg
every 6 hours; 100 mg/kg/day). Subsequently, we performed an
echocardiogram that showed no regurgitation of the valves, no
obvious vegetations, and normal left ventricular systolic function.
The patient became afebrile and subjectively showed improvement
within 24 hours of commencing intravenous ceftriaxone treatment.
Blood culture, done 48 hours after beginning antibiotic treatment,
was sterile. A recheck chest radiography 5 days after ceftriaxone
therapy revealed only residual and small focal parenchymal
consolidations over the right upper lobe. The species from our
patient is identified as S. mitis. Therapy with
ceftriaxone was changed to oral ceftibuten (200 mg daily), which was
continued for 9 days. Consequently, the patient totally recovered
without sequelae on follow-up, 1 month after discharge.
Viridans streptococci are often regarded as
nonpathogenic bacteria; clinical isolation of S. viridans is
usually attributed to specimen contamination. However, the organism
is recognized as a cause of infective endocarditis in patients with
valvular disease. In particular, it is commonly associated with
dental caries followed by an episode of bacteremia and dissemination
to remote sites. The lower respiratory tract is the most common site
of infection . In addition, S. viridans is recognized as
an important cause of pneumonia and sepsis in neutropenic
individuals . Nevertheless, S. viridans is rarely reported
to be the cause of pneumonia in immunocompetent patients, such as
the case illustrated here.
In children with fever and neutropenia, Paganini
and colleagues demonstrated an increasing incidence of viridans
bacteremia paralleling the increasing use of histamine type 2
antagonists, the presence of oropharyngeal mucositis, prophylactic
antibiotic treatment with cotrimoxazole or quinolones, severe
neutropenia, and chemotherapy involving high doses of ARA-C .
Gingivitis and toothbrushes can play potential roles in viridans
streptococcus bacteremia in immunodeficient patients . However,
no obvious predisposing factor has been identified in
immunocompetent hosts with viridans bacteremia.
Gaudreau, et al. first reported the
clinical relevance of bacteremia caused by S. viridans in 71
children in 1981 . However, the report did not mention about the
immune status of the children. In 1989, the first case series of
primary pneumonia caused by S. viridans with bacteremia in
healthy adults was reported and all of the cases were sensitive to
In Brazil, Freitas, et al. reported that
viridans streptococci rank as the second most frequent causal agent
of community-acquired pneumonia in children under 5 years of age and
that all of the affected patients appeared to be without underlying
disease; in that study, other causes, such as degree of malnutrition
or dental cavities, could not be excluded . In our report, the
patient did not have poor dental hygiene, malnutrition, or evidence
of immune deficiency. Nevertheless, pneumonia was proved from chest
radiography, and S. viridans bacteremia was identified from
Inappropriate use of antibiotics may have
resulted in the increased prevalence of antibiotic-resistant S.
viridans. In recent decades, penicillin resistance has been
progressively increasing in S. viridans . Ioannidou, et
al. analyzed 200 S. viridans cultures isolated
from the oropharynxes of 96 healthy Greek children and documented
different resistance rates to several antibiotics . The
prevalence of penicillin-resistant S. viridans varies
worldwide, e.g., 37.8% in India  and 11% in the United Kingdom
. Furthermore, Smith, et al.
pointed out that a significant proportion of
penicillin-resistant S. viridans strains are susceptible to
The overuse of antibiotics may increase the
incidence of infection by formerly nonpathogenic organisms such as
viridans streptococci and may be a potential cause of bacteremia and
pneumonia in the absence of other pathogens. Clinicians should note
any increased local incidence of community-acquired pneumonia due to
viridans streptococci and should select empiric antibiotic therapy
based on the local pattern of antibiotic susceptibility among recent
Contributors: All authors were involved in
all aspects of manuscript preparation.
Funding: None; Competing interests:
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