Changes in Availability of Oxygen Accentuate Differences in Capsular Polysaccharide Expression by Phenotypic Variants and Clinical Isolates of
            <i>Streptococcus pneumoniae</i>

Weiser, Jeffrey N.; Bae, Deborah; Epino, Henry; Gordon, Stephen B.; Kapoor, Miki; Zenewicz, Lauren A.; Shchepetov, Mikhail

doi:10.1128/iai.69.9.5430-5439.2001

Cited by 118 publications

(113 citation statements)

References 40 publications

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“…T colonies appear smaller in size, concave (umbilicated) and transparent in the center. The opaque colony is larger, more uniformly whitish throughout and with a domed center as previously described [14]. The edge of the colony is slightly irregular in the T variant, but smoother in the opaque variant.…”

Section: Pneumococcal Phase Variantsmentioning

confidence: 51%

Interaction of pneumococcal phase variation and middle ear pressure/gas composition: An in vitro model of simulated otitis media

Li-Korotky¹,

Banks²,

Lo³

et al. 2008

Microbial Pathogenesis

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Streptococcus pneumoniae, a leading cause of otitis media (OM), undergoes spontaneous intra-strain variations in colony morphology. Transparent (T) variant is more efficient in colonizing the nasopharynx while the opaque (O) variant exhibits greater virulence during systemic infections. We hypothesized that changes in middle ear (ME) gas pressure/composition during Eustachian tube (ET) dysfunction and the treatment of that dysfunction, e.g., tympanostomy tube (TT) insertion, play a role in selecting the S. pneumonia variant that can efficiently colonize/infect the ME mucosa. Human ME epithelial cells were preconditioned for 24 hrs under one of three conditions that simulated 1) normal ME, 2) ME with ET obstruction (ETO) and 3) ME with TT; subsequently exposed to a dose (~10 7 CFU/ml) of either T or O variant of S. pneumoniae, and then incubated for 1 hr and 3 hrs. Under the simulated ETO and TT conditions, T variant exhibited a higher growth rate and greater epithelial adherence and killing than did O variants. Attachment of T variant to epithelial cells was documented by scanning electron microscopy. These results suggest that the T-variant is more highly adapted to various ME environments than the O-variants.

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Section: Pneumococcal Phase Variantsmentioning

confidence: 51%

Interaction of pneumococcal phase variation and middle ear pressure/gas composition: An in vitro model of simulated otitis media

Li-Korotky¹,

Banks²,

Lo³

et al. 2008

Microbial Pathogenesis

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“…However, after invasion there is a predominance of the opaque phenotype (Weiser et al, 2001) and anaerobic conditions cause an increase in the amount of capsule in opaque variants. As stated by Weiser et al (2001), the bacteria would be exposed to the highest ambient oxygen levels when on the airway surface, but the oxygen tension encountered would be much lower during pneumonia, in blood or in the middle ear. It would be interesting to determine in further studies whether in opaque clinical isolates there is a change in the transcription of cpsA under anaerobic conditions and whether this differs between serotypes with high and low invasive potential.…”

Section: Discussionmentioning

confidence: 99%

In vitro expression of the first capsule gene of Streptococcus pneumoniae, cpsA, is associated with serotype-specific colonization prevalence and invasiveness

2007

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“…Previous studies in animal models have shown that transparent variants are released when nasal tissues are washed with physiological salt solutions, while the majority of S. pneumoniae isolates recovered from previously washed homogenized nasal tissue, from blood specimens, or from lung aspirates were in the opaque phase (1,12). In chinchillas pretreated with live influenza virus, inoculation with opaque pneumococci caused more severe middle ear infections than did inoculation with transparent pneumococci (10).…”

mentioning

confidence: 99%

“…However, the phase shifts have never been clearly demonstrated with human samples. A study in 2001 examined 19 "minimally passaged" paired nasal and blood isolates, but no statistical association was observed between the phase and body isolation site (P ϭ 0.51) (12). The present study was designed to investigate the morphological phase of pneumococci by plating them on transparent agar immediately upon their isolation from the nasopharynx and middle ear of children with AOM.…”

mentioning

confidence: 99%

Streptococcus pneumoniae Isolates from Middle Ear Fluid and Nasopharynx of Children with Acute Otitis Media Exhibit Phase Variation

et al. 2011

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Pneumococcal phase variation of 37 middle ear and 31 nasopharyngeal isolates obtained from children with acute otitis media was examined in the absence of intervening culture. The fraction of the opaque colonies was significantly higher in middle ear isolates than in nasopharyngeal isolates. The difference is probably the result of the pneumococci adapting to differential selective environments.Streptococcus pneumoniae first colonizes the mucosal surface of the human nasopharynx and can then infect the middle ear cavity via the Eustachian tubes to cause acute otitis media (AOM). In 1994, Weiser et al. reported spontaneous, reversible intrastrain phase variation of pneumococci in colony opacity on transparent agar surfaces (15). Transparent variants associated with low levels of capsular polysaccharide are able to most efficiently colonize the nasopharynx in animal models of pneumococcal carriage (8). In contrast, opaque variants associated with greater amounts of capsular polysaccharide colonize poorly in animals and provide greater resistance to clearance by phagocytes but at the same time decrease the adherence of opaque variants to host cells (2, 4). Thus, the intrastrain phase shifts of pneumococci are hypothesized to be adaptations to different stages in the pathogenesis of infections (1,8,10,13,14). However, the phase shifts have never been clearly demonstrated with human samples. A study in 2001 examined 19 "minimally passaged" paired nasal and blood isolates, but no statistical association was observed between the phase and body isolation site (P ϭ 0.51) (12). The present study was designed to investigate the morphological phase of pneumococci by plating them on transparent agar immediately upon their isolation from the nasopharynx and middle ear of children with AOM. By avoiding any growth between isolation and plating, we hoped to minimize the effects of bacterial growth in vitro on bacterial phase. The study focused on samples from young children because of their high rates of pneumococcal carriage and AOM.Middle ear and nasopharyngeal cultures were collected from all children between 5 and 70 months of age who presented at our clinic with AOM from 2008 to 2010 and who had not previously been treated with antibiotics. No subsequent cultures were collected for the study from any patients at later clinic visits. The swabs used to collect cultures were stored on transport agar with charcoal media (Eiken Chemical Co., Tokyo, Japan) at room temperature and transported to the laboratory for processing, and within 18 h of collection, they were plated on tryptic soy agar (TSA) plates for phase determination (with no intervening culture).Samples were obtained from 42 children, 25 males and 17 females, with a median age of 21.5 months. The children were all unrelated to each other, and only one culture from the nasopharynx and one from each ear were included in the study for a single patient, when available from the patient. All together, from the 42 children, 37 middle ear and 31 nasopharyngeal cultures were e...

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Changes in Availability of Oxygen Accentuate Differences in Capsular Polysaccharide Expression by Phenotypic Variants and Clinical Isolates of Streptococcus pneumoniae

Cited by 118 publications

References 40 publications

Interaction of pneumococcal phase variation and middle ear pressure/gas composition: An in vitro model of simulated otitis media

Interaction of pneumococcal phase variation and middle ear pressure/gas composition: An in vitro model of simulated otitis media

In vitro expression of the first capsule gene of Streptococcus pneumoniae, cpsA, is associated with serotype-specific colonization prevalence and invasiveness

Streptococcus pneumoniae Isolates from Middle Ear Fluid and Nasopharynx of Children with Acute Otitis Media Exhibit Phase Variation

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