Invasive Pneumococcal Infection in a Healthy Infant Caused by Two Different Serotypes

Abstract

We present a case of invasive pneumococcal infection in a healthy 10-month-old infant from whom Streptococcus pneumoniae serotype 23F was isolated from the blood and serotype 23B was isolated from the cerebrospinal fluid. Both serotypes were penicillin nonsusceptible. Pulsed-field gel electrophoresis analysis demonstrated that the two serotypes had distinct DNA patterns, indicating that infection did not occur as a result of capsular transformation but as a result of a mixed infection with two distinct pneumococcal serotypes. CASE REPORTIn July 2001, a previously healthy 10-month-old boy was admitted to the Tropical Diseases Hospital in Goiânia, Central Brazil, with a 2-day history of fever, irritability, and vomiting. There was no history of otitis media, pulmonary infection, or immunosuppressive illness. He had received two doses of an oral antimicrobial 12 h before admission, but his parents did not know its name. He had previously received three doses of Haemophilus influenzae type b conjugate vaccine, but he had not been vaccinated against Streptococcus pneumoniae. On admission, he was afebrile. He had meningeal signs and a bulging fontanelle, but the rest of the physical exam was unremarkable. Blood cultures were obtained and a lumbar puncture was performed immediately. The cerebrospinal fluid (CSF) was cloudy, with a white cell count of 6,750 cells/ml (90% polymorphonuclear cells), a protein level of 85 mg/dl, and a glucose level of 63 mg/dl. A Gram stain of the CSF was negative. A complete blood count showed 26,500 leukocytes/mm 3 (14% bands, 56% neutrophils, 26% lymphocytes, and 4% monocytes). The hemoglobin was 9.4 g/dl, the hematocrit was 28.3%, and the platelet count was 274,000/mm 3 . Treatment was begun with ceftriaxone (100 mg/kg of body weight/day) and dexamethasone, and after a 10-day course of treatment, the patient was discharged in good health.Cultures of the patient's blood and CSF grew S. pneumoniae. According to NCCLS standards (9), both isolates were nonsusceptible to penicillin (MIC ϭ 0.125 g/ml) and trimethoprim-sulfamethoxazole (MIC ϭ 4.0 g/ml) and susceptible to chloramphenicol (MIC ϭ 1.0 g/ml for blood and 2.0 g/ml for CSF), ceftriaxone (MIC ϭ 0.06 g/ml), vancomycin (MIC ϭ 0.5 g/ml), and erythromycin (MIC ϭ 0.03 g/ml). Both isolates were serotyped by the Quellung reaction with sera produced by the Statens Seruminstitute, Copenhagen, Denmark. The tests were performed at the Adolfo Lutz Institute, the national reference center for S. pneumoniae located in São Paulo, Brazil. Serotype 23F was identified in the blood, and serotype 23B was identified in the CSF. These results were confirmed by the National Center for Streptococcus in Edmonton, Canada.The genetic relatedness of the two pneumococcal isolates was investigated at the Adolfo Lutz Institute by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA after SmaI digestion, as previously described (8). As shown in Fig. 1, the two isolates presented different DNA restriction patterns (lanes A and B) with seven band differences acc...

Invasive Disease Caused Simultaneously by Dual Serotypes of Streptococcus pneumoniae

“…We describe cases of invasive pneumococcal disease caused simultaneously by two different strains. This phenomenon has been reported by others mainly in immunocompromised patients or in young children (5)(6)(7). Similarly, in our study, children younger than 5 years and patients with underlying illness other than HIV were more likely to have dual-serotype infection compared to older individuals and those without underlying illness, respectively.…”

“…Similar to dual-serotype IPD cases reported previously where coinfecting isolates from the same patient were genotypically unrelated (5,6), the majority of our isolate pairs were different strains as indicated by unrelated sequence types. The core genome of each isolate clustered with genomes of other South African IPD isolates of the same serotype and sequence type.…”

“…pneumococcal strains obtained over a period of 7 months from a patient with chronic pneumococcal infection, we are aware of only two other studies that characterized pneumococcal isolates obtained simultaneously from the same disease episode (5,6). Using pulsed-field gel electrophoresis, both studies showed that the isolates had different serotypes and genotypes.…”

Blood stream infection is associated with altered heptavalent pneumococcal conjugate vaccine immune responses in very low birth weight infants

“…First, vaccine response (either achievement of protective cutoff concentration and/or adequate OT) for serotypes 23F and 6B were low in the primary study, and this finding has been recently confirmed in another cohort of preterm infants 20 . In addition, these serotypes are associated with invasive disease in infants and 6B is the most common serotype for breakthrough infection following vaccination 21, 22 . Second, the frequency of BSI in the preterm infant can be as high as 60% in the most immature infants 14 .…”

High carriage rate of high-level penicillin-resistant Streptococcus pneumoniaein a Taiwan kindergarten associated with a case of pneumococcal meningitis

“…There has been an alarming increase in recent years in the prevalence of penicillin- resistant S. pneumoniae and pneumococcal meningitis caused by penicillin non-susceptible S. pneumoniae . Thus far pneumococcal meningitis caused by high-level penicillin resistant strains (MIC = 4 ug/ml) accounts for only a small portion of the cases reported from various countries around the world [ 1 - 6 ]. A case of pneumococcal meningitis caused by a high-level penicillin resistant S. pneumoniae 19F recently occurred in a 5-year old boy in southern Taiwan.…”