Ronit Trefler

Emergence of Penicillin-Nonsusceptible Streptococcus pneumoniae Clones Expressing Serotypes Not Present in the Antipneumococcal Conjugate Vaccine

BACKGROUND Penicillin-nonsusceptible Streptococcus pneumoniae isolates are confined mainly to a few serogroups. Capsular transformation may serve as a mechanism for spreading antibiotic resistance to new serotypes. METHODS Antibiogram and molecular typing, by pulsed-field gel electrophoresis (PFGE), were performed on 46 nasopharyngeal and middle ear fluid (MEF) isolates expressing serotype 11A, 45 MEF isolates expressing serotype 15B/C (recovered during 1998-2003 from Israeli children <5 years old), and 57 MEF isolates expressing serotype 19F (recovered during 1998-2001 from Costa Rican children <7.5 years old). RESULTS PFGE patterns showed that 49 (86%) of 57 serotype 19F isolates and 19 (41%) of 46 serotype 15B/C isolates were closely related. The vast majority of these isolates (80% of serotype 19F and 100% of serotype 15B/C isolates) were nonsusceptible to penicillin. Multilocus sequence typing (MLST) data show that the serotype 15B/C isolates belonged to the ST346 cluster, whereas the serotype 19F isolates were a single-locus variant of ST346. For serotype 11A isolates, PFGE patterns and MLST analysis showed that 8 (80%) of the 10 penicillin-nonsusceptible isolates belonged to a single clone--namely, ST156--which was identical to the international Spain9V-3 clone. CONCLUSIONS Penicillin-nonsusceptible pneumococcal clones of serotypes not related to those included in the 11-valent conjugate vaccines may derive from capsular transformation of vaccine-related serotypes. Of particular concern was the detection of serotype 11A variants of the successful international Spain9V-3 clone. This phenomenon, although seemingly rare at present, can have implications for the long-term effectiveness of the conjugate vaccines.

Outbreak of Kingella kingae skeletal system infections in children in daycare

Objective: The objective of this study is to describe the investigation of an outbreak of one culture-proven and two presumptive cases of Kingella kingae osteomyelitis detected within a 15-day period in a daycare center in Israel. Methods: Surveillance pharyngeal cultures were obtained from all attendees at the index daycare center and from two neighboring facilities. Combined amoxicillin–rifampin prophylaxis was administered to all children aged 6 to 30 months living in the community. K. kingae isolates were typed by pulsed field gel electrophoresis, random amplified polymorphic DNA analysis and sequencing of the rRNA genes. Results: Surveillance cultures showed that four of 11 attendees at the index facility as well as five of 12 and one of 15 attendees at neighboring daycare centers carried K. kingae. Typing of isolates showed that the isolate from a child with osteomyelitis was identical to all other isolates from the same daycare center and different from organisms derived from the other facilities. Administration of prophylactic antibiotics resulted in partial eradication of the organism. Conclusions: Dissemination of K. kingae in a susceptible pediatric population may result in an outbreak of invasive disease. Our experience suggests the need for increased alertness for clusters of K. kingae infections among children in daycare.

Four antibiotic-resistant Streptococcus pneumoniae clones unrelated to the pneumococcal conjugate vaccine serotypes, including 2 new serotypes, causing acute otitis media in southern Israel.

This study examined the prevalence of antibiotic-resistant clones that belong to serotypes not included in the pneumococcal conjugate vaccines and that cause a significant percentage of acute otitis media (AOM) in children in southern Israel. During 1998-2001, 2467 pneumococcal isolates, obtained from middle-ear fluid of children <3 years old with AOM, were characterized by antimicrobial susceptibility testing, serotype testing, and pulsed-field gel electrophoresis. Non-vaccine type (NVT) strains constituted 477 (19%) of the 2467 isolates, of which 173 (36%) belonged to only 4 serotypes: 35B, 33F, 21, and 15B/C. For serotype 35B, 47 (96%) of 49 strains were penicillin nonsusceptible, and 93% constituted a single clone; for serotype 33F, 31 (82%) of 38 strains were penicillin nonsusceptible, and 95% constituted a single clone; for serotype 21, 38 (93%) of 41 strains were penicillin nonsusceptible, and 93% constituted a single clone; for serotype 15B/C, 22 (49%) of 45 strains were penicillin nonsusceptible, and 42% constituted a single clone. Two of these clones have not been described elsewhere. The high prevalence of NVT clones should increase the awareness of the potential for replacement of the vaccine strains with these NVT antibiotic-resistant strains.

Community-Acquired Methicillin-Resistant Staphylococcus aureus in Institutionalized Adults with Developmental Disabilities

Methicillin-resistant Staphylococcus aureus (MRSA) has recently been reported to emerge in the community setting. We describe the investigation and control of a community-acquired outbreak of MRSA skin infections in a closed community of institutionalized adults with developmental disabilities. In a 9-month period in 1997, 20 (71%) of 28 residents had 73 infectious episodes. Of the cultures, 60% and 32% obtained from residents and personnel, respectively, grew S. aureus; 96% and 27% were MRSA. All isolates were genetically related by pulsed-field gel electrophoresis and belonged to a phage type not previously described in the region. No known risk factors for MRSA acquisition were found. However, 58 antibiotic courses had been administered to 16 residents during the preceding 9 months. Infection control measures, antibiotic restriction, and appropriate therapy resulted in successful termination of this outbreak. Selective antibiotic pressure may result in the emergence, persistence, and dissemination of MRSA strains, causing prolonged disease.

Dissemination of Kingella kingae in the community and long-term persistence of invasive clones.

Background: Although Kingella kingae is being increasingly recognized as an important pediatric pathogen, our current understanding of the transmission of the organism is limited. The dissemination of K. kingae in the community was studied in 2 ethnic groups living side-by-side in Southern Israel. Methods: Organisms recovered from oropharyngeal cultures, obtained from healthy young Jewish and Bedouin children during a 12-month period, were typed by pulsed-field gel electrophoresis and compared. Results: Isolates from Bedouin children usually differed from those derived from Jews, confirming the relative social isolation of the 2 populations and the importance of close mingling in the spread of K. kingae. Significant clustering of genotypic clones in households and Bedouin neighborhoods was observed, indicating person-to-person transmission through intimate contact. Organisms detected in the study were identical to historical isolates recovered over the last 15 years from respiratory carriers and patients with bacteremia or skeletal infections. Conclusions: The present study demonstrates that children may be asymptomatically colonized in the respiratory tract by virulent K. kingae clones. The organism is transmitted from child-to-child through intimate contact. Some strains exhibit increased fitness and are maintained in the population for prolonged periods.

Persistence of Two Invasive Streptococcus pneumoniae Clones of Serotypes 1 and 5 in Comparison to That of Multiple Clones of Serotypes 6B and 23F among Children in Southern Israel

ABSTRACT We conducted a study to examine the clonal distribution of invasive serotype 1 and 5 isolates as representatives of serotypes that are rarely carried by healthy individuals compared to that of invasive serotype 6B and 23F isolates as representatives of serotypes often carried by young children for prolonged periods. All invasive serotype 1, 5, 6B, and 23F isolates recovered from blood cultures during January 1995 to May 1999 were analyzed; these included 66 serotype 1, 30 serotype 5, 11 serotype 6B, and 15 serotype 23F isolates. One hundred thirty-three nasopharyngeal (NP) isolates of the indicated four serotypes from healthy children were also studied. The strains were characterized using serotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis profiling. We found that both invasive and NP serotype 1 and 5 isolates were susceptible to penicillin and that each serotype showed only one clonal type. In contrast, serotype 6B and 23F strains showed different phenotypic characteristics as well as multiple clonal types; 10 clones were identified among 6B isolates, and 11 clones were identified among 23F isolates.

An international serotype 3 clone causing pediatric noninvasive infections in Israel, Costa Rica, and Lithuania.

Background: Serotype 3 is known for its ability to cause invasive diseases worldwide. In the United States, after introduction of the 7-valent pneumococcal conjugate vaccine (PCV7), the prevalence of a serotype 3 clone (Netherlands3-31/ST180) increased. The present study was aimed to evaluate the importance of serotype 3 clones in noninvasive infections in Israel, Costa Rica, and Lithuania. Methods: Molecular typing and antibiotic resistance were performed on 77 serotype 3 strains recovered from pediatric noninvasive infections during 2003–2005, and on 50 carried strains from healthy carriers. Results: Serotype 3 ranked second among isolates from noninvasive infections in Costa Rica and Lithuania, and seventh among the Israeli isolates. Pulsed field gel electrophoresis (PFGE) analysis revealed the presence of 1 major cluster (64/77, 83%); this cluster comprised 60/64 fully susceptible strains that corresponded to the Netherlands3-31/ST180 clone, and 4/64 multidrug-resistant strains, all from Lithuania, that corresponded to ST505, a double locus variant of ST180. Two additional fully susceptible clones, ST458 (11/77, 14%) and ST1116 (2/77, 3%), were found among the Israeli and Costa Rican strains, respectively. The same PFGE clusters identified among noninvasive infections were found among 50 isolates from carriers, with the same molecular characteristics. Conclusions: Serotype 3 accounts for a large proportion of mucosal disease in children, even before the introduction of PCV7. The data presented here describe for the first time the importance of a multidrug-resistant serotype 3 clone, ST505, in noninvasive infections.

The Important Role of Nontypable Streptococcus pneumoniae International Clones in Acute Conjunctivitis

BACKGROUND In a recent epidemiological study in southern Israel, nontypable Streptococcus pneumoniae isolates were found to be highly associated with sporadic cases of acute conjunctivitis (AC). The purpose of the present study was to evaluate the relative importance in causing AC of the absence of capsule versus genotype properties. METHODS DNA typing by pulsed-field gel electrophoresis (PFGE) was performed on 148 nontypable organisms isolated from 3 sites: nasopharynx of healthy children, middle-ear fluid, and conjunctiva. RESULTS Analysis of the PFGE patterns revealed the presence of 6 clusters; 2 clusters that included 44% of the isolates (65/148) were associated with AC, and the remaining 4 were frequently isolated from the nasopharynx. Multilocus sequence typing, performed on representative isolates of the 2 major clusters, confirmed that the organisms were pneumococci; one is a single-locus variant of sequence type (ST) 448, and the other is related to ST344. Both types appear to be members of pneumococcal lineages that have lost capsular loci. The nontypable isolates showed high rates of resistance to antimicrobial agents. CONCLUSIONS Our data suggest that the absence of the capsule--along with other, yet-unidentified genetic characteristics--provide S. pneumoniae with a selective virulence advantage in conjunctivitis.

Epidemiology of invasive Kingella kingae infections in 2 distinct pediatric populations cohabiting in one geographic area.

The annual incidence of invasive Kingella kingae infection in children younger than 4 years of age was significantly higher in westernized Jews than in indigent Bedouins living side by side in southern Israel (12.21/100,000 and 5.83/100,000, respectively, (P , 0.05). One K. kingae clone was overrepresented among isolates from Jewish children, suggesting that differences in bacterial pathogenicity may contribute to the morbidity excess detected in this population group.

Molecular Typing of Streptococcus pneumoniae in Northeastern Romania: Unique Clones of S. pneumoniae Isolated from Children Hospitalized for Infections and from Healthy and Human Immunodeficiency Virus-Infected Children in the Community

Microbiologic, serologic, and molecular typing techniques were used to characterize 272 isolates of Streptococcus pneumoniae colonizing or infecting children in Iasi, Romania, during a surveillance study conducted in 1996-1998. The 574 children in the study were from the following groups: healthy children attending 2 institutions, healthy children hospitalized for elective surgery, hospitalized children with pneumococcal infections, and human immunodeficiency virus (HIV)-infected children in an orphanage. Pneumococci colonizing healthy children from closed communities showed close similarities to pneumococci from children with pneumococcal infections; they expressed a limited number of similar serotypes, showed high frequency of penicillin and multidrug resistance, and shared several common clonal types. In contrast, isolates recovered from healthy children hospitalized for elective surgery expressed a large variety of serotypes, were less frequently resistant to antimicrobial agents, and showed great genetic diversity. Pneumococcal flora colonizing HIV-infected children showed a more complex epidemiology. These observations suggest a possible epidemiologic connection between the flora of S. pneumoniae colonizing healthy children in closed communities and the flora found in children hospitalized for infection.