Distribution of capsular types and antimicrobial susceptibility of invasive isolates of Streptococcus pneumoniae in Colombian children. Pneumococcal Study Group in Colombia

Serotypes and genotypes of Streptococcus pneumoniae isolates from Trinidad and Tobago

OBJECTIVES

There are currently 94 known pneumococcal capsular polysaccharide serotypes and their prevalence differs by geographic region and the period studied. Streptococcus pneumoniae infections have been diagnosed clinically in Trinidad and Tobago and other Caribbean countries, however data on the serotype and sequence type distributions in this country are limited. The objective of this study was to determine serotypes and multilocus sequence types (MLSTs) of invasive and non-invasive pneumococcal isolates from Trinidad and Tobago.

METHODS

Ninety-eight pneumococcal isolates from several regional hospitals in the country were analyzed using both standard microbiological methods and molecular analysis. These isolates included invasive (n=83) and selected non-invasive (n=15) strains recovered before (n=25) and after (n=73) the introduction of the pneumococcal conjugate vaccine.

RESULTS

More than half of the isolates (54.1%) were recovered from children under 15 years of age, with the largest proportion being from children under 2 years of age (24.5%). The most prevalent serotypes were 19F (18.4%), 6B (15.3%), 23F (14.3%), 3 (11.2%), 19A (6.1%), 6A (5.1%), 14 (5.1%), and 9V (4.1%). The most common serotype/MLST combinations were 6B/ST138 (n=10, 10.2%), 3/ST180 (n=5, 5.1%), 23F/ST629 (n=5, 5.1%), 19F/ST8398 (n=4, 4.1%), and three each of 6B/ST145, 14/9V/ST156, 9V/ST162, 19A/320, and 3/ST10440.

CONCLUSIONS

This report provides the first glimpse of the prevailing pneumococcal sequence types in the country. Most of the isolates represented serotypes in the 10-valent (61.2% of isolates) and 13-valent (83.7%) pneumococcal conjugate vaccines. A detailed population study is warranted to fully determine the circulating pneumococcal sequence types. Furthermore, the implementation of an effective and continuous surveillance system in Trinidad and Tobago is paramount to monitor vaccine impact.

Humoral immune responses to Streptococcus pneumoniae in the setting of HIV-1 infection

Streptococcus pneumoniae (pneumococcus) remains one of the most commonly identified causes of bacterial infection in the general population, and the risk is 30-100 fold higher in HIV-infected individuals. Both innate and adaptive host immune responses to pneumococcal infection are important against pathogen invasion. Pneumococcal-specific IgA antibody (Ab) is key to control infection at the mucosal sites. Ab responses against pneumococcal infection by B cells can be generated through T cell-dependent or T cell-independent pathways. Depletion of CD4+ T cells is a hallmark of immunodeficiency in HIV infection and this defect also contributes to B cell dysfunction, which predisposes to infections such as the pneumococcus. Two pneumococcal vaccines have been demonstrated to have potential benefits for HIV-infected patients. One is a T cell dependent 13-valent pneumococcal conjugate vaccine (PCV13); the other is a T cell independent 23-valent pneumococcal polysaccharide vaccine (PPV23). However, many questions remain unknown regarding these two vaccines in the clinical setting in HIV disease. Here we review the latest research regarding B cell immune responses against pneumococcal antigens, whether derived from potentially invading pathogens or vaccinations, in the setting of HIV-1 infection.

Epidemiology of pediatric pneumococcal meningitis and bacteremia in Latin America and the Caribbean: a systematic review and meta-analysis

BACKGROUND

Pneumococcal meningitis and bacteremia pose a significant disease burden in Latin America and the Caribbean (LAC).

METHODS

To perform a systematic review of studies of pediatric pneumococcal meningitis and non-pneumonia, non-meningitis pneumococcal bacteremia in LAC, we conducted an exhaustive search from 2000 to 2010 in electronic databases and grey literature. Pairs of independently selected reviewers assessed the quality and extracted the studies' data. A STROBE-based checklist was used to assess the risk of bias in observational studies. Meta-analyses were performed.

RESULTS

Of 1218 retrieved studies, 39 were included. In children <5 years, the pooled 95% confidence interval (CI) percentage of pneumococcal etiology out of cases studied with cerebrospinal fluid/blood cultures was 6.0% (95% CI: 3.3-9.5) for meningitis and 8.0% (95% CI: 5.3-12.4) for bacteremia. The incidences per 100,000 children were 4.7 (95% CI: 3.2-6.1) and 3.9 (95% CI: 2.0-5.9) for pneumococcal meningitis and non-pneumonia, non-meningitis bacteremia, respectively. The mortality was 8.3 (95% CI: 0.0-21.0) and 0.5 (95% CI: 0.3.0-0.6)/100,000 for meningitis and sepsis, respectively. The case fatality ratio was 33.2% (95% CI: 21.3-46.2) for meningitis and 29.0% (95% CI: 21.9-36.8) for sepsis. The pooled serotype distribution from SIREVA surveillance data showed that 14, 5, 6B (for meningitis) and 14, 6B, 19F (for bacteremia) were the most frequent serotypes, all included in licensed vaccines.

CONCLUSION

Pneumococcal meningitis and bacteremia are important causes of morbidity and mortality in LAC children <5 years of age. This systematic review provided evidence about the burden of pneumococcal disease and the serotype distribution to assess the impact the pneumococcal vaccines and to assist decision makers in the region.

Streptococcus pneumoniae serotype 19A in Latin America and the Caribbean: a systematic review and meta-analysis, 1990-2010

BACKGROUND

Pneumococcal conjugate vaccines (PCVs) are in the process of implementation in Latin America. Experience in developed countries has shown that they reduce the incidence of invasive and non-invasive disease. However, there is evidence that the introduction of PCVs in universal mass vaccination programs, combined with inappropriate and extensive use of antibiotics, could be associated to changes in non-PCV serotypes, including serotype 19A. We conducted a systematic review to determine the distribution of serotype 19A, burden of pneumococcal disease and antibiotic resistance in the region.

METHODS

We performed a systematic review of serotype 19A data from observational and randomized clinical studies in the region, conducted between 1990 and 2010, for children under 6 years. Pooled prevalence estimates from surveillance activities with confidence intervals were calculated.

RESULTS

We included 100 studies in 22 countries and extracted data from 63. These data reported 19733 serotyped invasive pneumococcal isolates, 3.8% of which were serotype 19A. Serotype 19A isolates were responsible for 2.4% acute otitis media episodes, and accounted for 4.1% and 4.4% of 4,380 nasopharyngeal isolates from healthy children and in hospital-based/sick children, respectively. This serotype was stable over the twenty years of surveillance in the region. A total of 53.7% Spn19A isolates from meningitis cases and only 14% from non meningitis were resistant to penicillin.

CONCLUSIONS

Before widespread PCV implementation in this region, serotype 19A was responsible for a relatively small number of pneumococcal disease cases. With increased use of PCVs and a greater number of serotypes included, monitoring S. pneumoniae serotype distribution will be essential for understanding the epidemiology of pneumococcal disease.

Population-based surveillance for invasive pneumococcal disease and pneumonia in infants and young children in Bogotá, Colombia

BACKGROUND

In children <5 years of age, Streptococcus pneumoniae (SP) is, globally, the leading cause of vaccine-preventable death. Surveillance conducted in Bogotá, Colombia estimated incidence rates of invasive pneumococcal disease (IPD), clinical and chest radiograph-confirmed pneumonia (CXR+Pn); SP serotype distribution and antimicrobial susceptibility.

METHODS

This prospective population-based surveillance was conducted from 2006 to 2008 in children 28 days to <36 months of age seeking care at SaludCoop centers. We determined incidence rates of IPD and pneumonia (clinical and CXR+Pn). Eligibility criteria included: temperature ≥39.0°C within 24h and/or clinical suspicion of IPD or pneumonia. Blood was obtained for culture in all children. Other sterile site specimens were obtained per routine practice.

RESULTS

Of 8261 subjects enrolled, a total of 64 had invasive pneumococcal disease detected by isolation of SP from nonduplicative cultures (62) or detected solely by PCR and a clinical picture consistent with IPD (2). The overall IPD incidence rates for culture-positive only cases for children aged 28 days to <36 months was 76.4/100,000 per year for years 1 and 2 combined. Age stratification found the highest rates in children 6-12 and 12 to <24 months of age. IPD incidence rates were assessed for bacteremic pneumonia (54.2/100,000), bacteremia (17.2/100,000), meningitis (3.7/100,000), and sepsis (1.2/100,000). Most common serotypes causing IPD were: 14 (51.6%), 6B (9.7%), and 19F (9.7%). Coverage of IPD cases by pneumococcal conjugate vaccine (PCV) 7, PCV10, and PCV13 was 77.4%, 85.5%, and 91.9%, respectively. Twenty-eight isolates (45.2%) were penicillin-nonsusceptible; PCV7 covered 96.3% of these; PCV10 covered 96.3% and PCV13 covered 100%. The overall incidence of clinical pneumonia and CXR+Pn was 6276/100,000 and 2120/100,000, respectively.

CONCLUSION

Pneumococcal disease and pneumonia burden is considerable in children in Bogotá, Colombia. Vaccination with pneumococcal conjugate vaccines has the potential to decrease this burden. Epidemiologic data are critical in assessing the potential impact of introduction of PCVs into national immunization schedules.

Increasing penicillin and trimethoprim-sulfamethoxazole resistance in nasopharyngeal Streptococcus pneumoniae isolates from Guatemalan children, 2001--2006

OBJECTIVES

We aimed to determine nasopharyngeal colonization rates and antibiotic resistance patterns of Streptococcus pneumoniae isolated from Guatemalan children, and to determine risk factors for colonization and antibiotic nonsusceptibility.

METHODS

Isolates were obtained from children aged 5 to 60 months attending public and private outpatient clinics and daycare centers during August 2001--June 2002 and outpatient clinics during November 2005--February 2006 in Guatemala City. Minimal inhibitory concentrations of penicillin, trimethoprim-sulfamethoxazole (TMS), cefotaxime, and erythromycin were determined using the E-test.

RESULTS

The overall nasopharyngeal colonization rate for S. pneumoniae was 59.1%. From 2001/2 to 2005/6 TMS nonsusceptibility increased from 42.4% to 60.8% (p<0.05) in public clinics and from 51.4% to 84.0% (p=0.009) in private clinics, and penicillin nonsusceptibility increased from 1.5% to 33.3% in public clinics (p<0.001). Reported antibiotic use was not strictly associated with nonsusceptibility to that same antibiotic. Resistance to three or four antibiotics increased in public clinics from 2001/2 (0%) to 2005/6 (10.7%; p<0.001). Risk factors for nasopharyngeal colonization with penicillin- or TMS-nonsusceptible S. pneumoniae were low family income, daycare center attendance, and recent penicillin use.

CONCLUSIONS

Increasing antibiotic nonsusceptibility rates in nasopharyngeal S. pneumoniae isolates from Guatemalan children reflect worldwide trends. Policies encouraging more judicious use of TMS should be considered.

Vaccine-induced human antibodies to PspA augment complement C3 deposition on Streptococcus pneumoniae

Pneumococcal surface protein (PspA) is a virulence factor expressed by all clinical isolates of Streptococcus pneumoniae. PspAs are variable in structure and have been grouped into clades and cross-reacting families based on sequence similarities and immunologic cross-reactivity. At least 98% of PspAs are found in PspA families 1 or 2. PspA has been shown to interfere with complement deposition on pneumococci, thus reducing opsonization and clearance of bacteria by the host immune system. Prior studies using pooled human sera have shown that PspA interferes with C3 deposition on a single strain of S. pneumoniae, WU2, and that mouse antibody to PspA can enhance the deposition of C3 on WU2. The present studies have demonstrated that these previous findings are representative of most normal human sera and each of seven different strains of S. pneumoniae. It was observed that PspAs of PspA families 1 and 2 could inhibit C3 deposition in the presence of immunoglobulin present in all but 3 of 22 normal human sera. These studies have also demonstrated that rabbit and human antibody to PspA can enhance the deposition of C3 on pneumococci expressing either family 1 or 2 PspAs and either capsular types 2, 3, or 11. A vaccine candidate that can elicit immunity that neutralizes or compensates for S. pneumoniae's ability to thwart host immunity would be of value.

Penicillin resistance and serotyping of Streptococcus pneumoniae in Latin America

Streptococcus pneumoniae (Strep. pneumoniae) is the main cause of bacterial pneumonia in children less than 5 years of age, with high mortality rates in developing countries. In 1993, the Regional System for Vaccines Group (SIREVA) of the pan-American Health Organisation (PAHO) began a study involving six Latin American countries to identify serotypes and their representativity in the new conjugated vaccines, and to determine the degree of resistance to penicillin. Serotypes 14 (highest resistance level), 5, 1, 6A/B, 23F, 7F, 9V, 19F, 18C, 19A, 9N, were prevalent in the region, with some differences among countries. Although resistance to penicillin ranged from 2% (Brazil) to 21.1% (Mexico), studies have shown that pneumonia caused by Strep. pneumoniae with diminished sensitivity to penillin can be treated with this antibiotic. Only 58% of the serotypes isolated in the region studied were represented in the seven-valent vaccine. Continual surveillance is essential to determine which formulation of conjugated vaccine will be suitable for use in Latin America.

Invasive pneumococcal infections among hospitalized children in Bamako, Mali

BACKGROUND

Prevention of invasive pneumococcal disease (IPD) in children is a global public health priority, and determination of the most common serotypes is crucial for vaccine development and implementation.

METHODS

We performed prospective surveillance for IPD in hospitalized children in Bamako, Mali. All febrile children and others suspected to have invasive bacterial disease had an admission blood culture and cultures of additional anatomic sites when indicated. Standard microbiologic methods were used to identify, serotype and determine antibiograms for pneumococcal isolates.

RESULTS

Of 2,049 children enrolled, 106 (5%) had an IPD, including 47 cases of meningitis and 44 bacteremic pneumonias. The incidence was highest in infants (84/100,000/year). The overall IPD case fatality rate was 24%. Only 2 of 96 isolates were nonsusceptible to penicillin. The serotypes isolated were 5 (54%), 2 (14%), 7F (10%), 19F (8%), 6A/B (3%), 9V (3%), 1 (2%) and 14 (1%).

CONCLUSIONS

IPD is common and frequently fatal among hospitalized children in Mali, but surprisingly little resistance has occurred. Notably, 91% of the serotypes causing IPD in Bamako children are found in the 11-valent pneumococcal conjugate vaccine.

Relative roles of genetic background and variation in PspA in the ability of antibodies to PspA to protect against capsular type 3 and 4 strains of Streptococcus pneumoniae

Pneumococcal surface protein A (PspA) is able to elicit antibodies in mice and humans that can protect mice against fatal infection with Streptococcus pneumoniae. It has been observed that immunization with a single family 1 PspA can protect mice against infections with capsular type 3 or 6B strains expressing PspA family 1 or 2. However, several studies have shown that immunity to PspA is less efficacious against several capsular type 4 strains than against strains of capsular types 3, 6A, and 6B. To determine whether the greater difficulty in protecting against capsular type 4 strains resulted from differences in their PspAs or from differences in their genetic backgrounds, we performed protection experiments using four different challenge strains: a capsular type 3 strain expressing a family 1 PspA (WU2), a capsular type 4 strain expressing a family 2 PspA (TIGR4), and genetically engineered variants of WU2 and TIGR4 expressing each other's PspAs. Prior to infection, the mice were immunized with recombinant family 1 or family 2 PspA. The results revealed that much of the difficulty in protecting against capsular type 4 strains was eliminated when mice were immunized with a homologous PspA of the same PspA family. However, regardless of which PspA the strains expressed, those on the TIGR4 background were about twice as hard to protect against as WU2 strains expressing the same PspA based on the efficacy rates seen in our experiments. These results point out the importance of including more than one PspA in any PspA vaccines developed for human use.

Antimicrobial susceptibilities and serotype distribution of Streptococcus pneumoniae isolates from a Low socioeconomic area in Lima, Peru

Streptococcus pneumoniae isolates were obtained from nasopharyngeal swabs taken from children living in a low socioeconomic area of Lima, Peru, to determine the rates of antimicrobial resistance and serotype distribution. A total of 146 nasopharyngeal isolates were collected from children from 3 to 38 months of age. Twenty-one clinical laboratory isolates from both sterile and nonsterile sites were obtained from a local hospital. Isolates with reduced susceptibilities to penicillin represented 15.1 and 42.9% of the nasopharyngeal and clinical isolates, respectively. For neither group of isolates did penicillin MICs exceed 1.5 micro g/ml, indicating only intermediate resistance. Thirty-two different serotypes were identified from the 146 nasopharyngeal isolates. The serotypes of the clinical isolates were represented among those 32 types. Isolates with reduced susceptibility to multiple antimicrobial agents were present in both settings. These findings indicate some of the highest rates of antimicrobial resistance in the region as well as a slightly different serotype distribution pattern from those of other South American countries. The 7-valent conjugate pneumococcal vaccines would only have a limited effect, providing coverage for about half of all isolates. Increasing rates of resistance in Peru necessitate an awareness of antimicrobial treatment practices and vaccination strategies.

Dissemination of Streptococcus pneumoniae clone Colombia(5)-19 in Latin America

Streptococcus pneumoniae serotype 5 is the third most common capsular type causing invasive diseases in children younger than 5 years in Latin America. Preliminary data on Colombian serotype 5 isolates indicated a common clonal origin associated with resistance to tetracycline (TET) and chloramphenicol (CHL). We studied 172 S. pneumoniae serotype 5 invasive isolates from Argentina, Brazil, Colombia, Guatemala, Mexico, and Uruguay and confirmed the presence of the Colombia(5)-19 clone throughout Latin America. Fifteen subtypes of a pulsed-field gel electrophoresis pattern and 4 electrophoretic types (ET) were obtained. Most of the isolates from different geographical regions belonged to pattern A (34.3%), subtype A5 (41.9%), and ET1 (91.1%). The A pattern (n = 59) was resistant to TET and had variable resistance to CHL; it was present in Brazil (10.2%), Colombia (78%), Guatemala (8.5%), and Mexico (3.4%). Subtype A5 with variable susceptibility to TET and sensitive to CHL was found in Argentina (29.2%), Mexico (8.3%), and Uruguay (62.5%). Subtypes A1-A4, A7-A8, and A9-A11 (closely related to A) also shared ET1, while subtype A6 was assigned to ET1, ET2, and ET3. Eleven subtypes (n = 21) were found to be specific for one country each. In summary, the S. pneumoniae serotype 5 isolates from Latin American are genetically closely related but show different patterns of antibiotic resistance, probably as a result of horizontal transfer.

Antibiotic resistance in Streptococcus pneumoniae in six Latin American countries: 1993-1999 surveillance

The impact of invasive pneumococcal invasive disease is increased by the emergence of antibiotic resistance. We report regional and temporal variations in antibiotic resistance for 4,105 invasive Streptococcus pneumoniae isolates collected from Latin American children <5 years, between 1993 and 1999. Reduced susceptibility to penicillin was detected in 1,182 isolates (28.8%); 36% of these were resistant (> or = 2 microg/ml), including 12.6% with MIC > or = 4 microg/ml, occurring primarily in serotypes 14 and 23F. Reduced susceptibility to third-generation cephalosporins was detected in 12.1% of the collection. Mexico had the highest proportion of reduced susceptibility to penicillin (51.6%) and to third-generation cephalosporins (22%), whereas Brazil had the lowest at 20.9% and 0.7%, respectively. Isolates cultured from patients with pneumonia were more likely to have reduced susceptibility to third-generation cephalosporins than isolates from patients with meningitis (p < 0.0001). Susceptibility to trimethoprim-sulfamethoxazole, chloramphenicol, erythromycin, and vancomycin was tested by disk diffusion for 2.899 isolates. Reduced susceptibility was observed for 45.6%, 11.5%, 6.9%, and 0%, respectively. Thirty-one percent of the strains were resistant to > or = 2 drugs. High levels of antibiotic resistance in Latin America emphasize the need for the development of and adherence to rational antibiotic use guidelines. On-going surveillance will monitor the impact of these programs.

Presence of international multiresistant clones of Streptococcus pneumoniae in Colombia

In Colombia, penicillin resistance of Streptococcus pneumoniae invasive isolates recovered from children less than 5 years old has increased from 10% in 1994 to 49.4% in 1999, suggesting the circulation of international resistant clones in the country. A total of 167 S. pneumoniae invasive isolates with diminished susceptibility to penicillin (DSP) were studied. The techniques used were pulsed-field gel electrophoresis (PFGE) and restriction fragment length polymorphism (RFLP) of penicillin-binding proteins (PBPs) genes (2B, 2X, and 1A). Forty-nine serotype 23F isolates were grouped in two clusters: 15 (31%) multiresistant isolates showed PFGE pattern A and PBP I profile, thus making them indistinguishable from Spain23F-1 clone, and 34 (69%) with PFGE pattern C, PBP II profile, and intermediate level resistance (ILR) to penicillin and TMP-SMX, features unique to a Colombian clone. Fifty-five serotype 14 isolates were assigned to PFGE B pattern, PBP III profile, having high-level resistance to penicillin, and TMP-SMX, similar to the France9V variant 14. This same pattern was present in five capsular type 9V isolates. Four serotype 14 isolates were assigned to PFGE pattern F, and appeared to be similar to Slovakia(14)-10 PFGE pattern, although they had different PBP profiles. Nine capsular type 6B and one 6A isolates belonged to PFGE pattern M, similar to Spain6B-2, although they showed different PBP profiles. The remaining 44 isolates, corresponding to serotypes 14, 6B, 19F, and 34, showed variable PFGE and PBP patterns. These results show that as many as two international clones may be circulating in Colombia as well as a unique, widely distributed 23F clone with ILR to penicillin. Additionally, some Colombian isolates capsular type 14 and 6B might be related to Slovakia(14)-10 Spain6B-2 clones, respectively.

Population-based survey of antimicrobial susceptibility and serotype distribution of Streptococcus pneumoniae from meningitis patients in Salvador, Brazil

Penicillin-nonsusceptible strains were isolated from 15% of 303 individuals with pneumococcal meningitis identified during a 4-year surveillance study in Salvador, Brazil. The estimated rate of coverage of the seven-valent conjugate vaccine was 74% among patients <5 years of age and 94% among those infected with nonsusceptible isolates, indicating that the use of conjugate vaccines may be an approach to the control of emerging penicillin resistance in Brazil.

Evolution of Streptococcus pneumoniae serotypes and penicillin susceptibility in Latin America, Sireva-Vigía Group, 1993 to 1999. PAHO Sireva-Vigía Study Group. Pan American Health Organization

BACKGROUND

Since 1993 the Pan American Health Organization has coordinated a surveillance network with the National Reference Laboratories of Argentina, Brazil, Chile, Colombia, Mexico and Uruguay aimed at monitoring capsular types and antimicrobial susceptibility of Streptococcus pneumoniae causing invasive disease in children <6 years of age.

METHODS

The surveillance system included children 6 years of age and younger with invasive disease caused by S. pneumoniae. The identification, capsular typing and susceptibility to penicillin of the isolates were conducted using a common protocol, based on standard methodologies.

RESULTS

By June, 1999, 4,105 invasive pneumococcal isolates had been collected mainly from pneumonia (44.1%) and meningitis (41.1%) cases. Thirteen capsular types accounting for 86.1% of the isolates (14, 6A/6B, 5, 1, 23F, 19F, 18C, 19A, 9V, 7F, 3, 9N and 4) remained the most common types during the surveillance period. Diminished susceptibility to penicillin was detected in 28.6% of the isolates, 17.3% with intermediate and 11.3% with high level resistance. Resistance varied among countries and increased during this period in Argentina, Colombia and Uruguay. Serotypes 14 and 23F accounted for 66.6% of the resistance.

CONCLUSION

These surveillance data clearly demonstrate the potential impact of the introduction of a conjugate vaccine on pneumococcal disease and the need for more judicious use of antibiotics to slow or reverse the development of antimicrobial resistance.

Worldwide prevalence of antimicrobial resistance in Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the SENTRY Antimicrobial Surveillance Program, 1997-1999

The in vitro activities of numerous antimicrobials against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis from patients with bloodstream and respiratory tract infections in the United States, Canada, Europe, Latin America, and the Asia-Pacific region were studied in the SENTRY Antimicrobial Surveillance Program. Penicillin resistance (minimum inhibitory concentration, > or =2 microg/mL) was noted in all 5 geographic regions, and a high and increasing rate of macrolide resistance among S. pneumoniae isolates was observed. Elevated rates of resistance to clindamycin, trimethoprim-sulfamethoxazole, chloramphenicol, and tetracycline were seen. beta-Lactamase-mediated resistance in H. influenzae to amoxicillin and variable trimethoprim-sulfamethoxazole resistance by region were documented. Resistance to several drugs continues to emerge among pneumococci worldwide, but more stable resistance patterns have been noted for H. influenzae and M. catarrhalis. Continued surveillance of this pathogen group appears to be prudent.

Pneumococcal surface protein A of invasive Streptococcus pneumoniae isolates from Colombian children

Pneumococcal surface protein A (PspA) elicits protection in mice against fatal bacteremia and sepsis caused by genetically diverse pneumococci and protects against carriage and lung infection. We determined the PspA families of invasive isolates of Streptococcus pneumoniae recovered from Colombian children <5 years of age. That 97.5% of Colombian isolates belong to PspA families 1 and 2 supports the hypothesis that a human PspA vaccine covering a few PspA families could be broadly effective.

Susceptibility of 1100 Streptococcus pneumoniae strains isolated in 1997 from seven Latin American and Caribbean countries. Laser Study Group

The antimicrobial susceptibility to beta-lactam and non-beta-lactam agents of 1100 isolates of Streptococcus pneumoniae recovered in 1997 from 16 centres in Argentina, Brazil, Chile, Mexico, Panama, Venezuela and West Indies was studied using E-test and disk diffusion methods. A total of 23.6% of isolates had raised penicillin MICs (16.7% intermediate and 6.9% resistant). The susceptibility of the other agents tested, from most active to least active, were, amoxycillin/clavulanate (99.5% susceptible); chloramphenicol (93.2%); cefotaxime (91.7%); erythromycin (87.1%); tetracycline (74.6%); trimethoprim/sulphamethoxazole (TMP-SMZ) (55.4%); and cefaclor (52.8%). The highest proportion of strains resistant to penicillin, chloramphenicol, erythromycin, tetracycline and TMP-SMZ was found in strains from Mexico while resistance to these agents was lowest in strains from the West Indies. Prevalence of penicillin resistance (including intermediate and resistant isolates) in each of the countries, from highest to lowest was, Mexico (40.8%); Chile (31.3%); Panama (23.0%); Venezuela (21.9%); Argentina (19.1%); Brazil (12.9%); and West Indies (7.1%). Based on current levels of antimicrobial resistance of S. pneumoniae in Latin American and Caribbean countries, continued surveillance efforts are necessary in order to guide clinical empiric treatment and provide for judicious use of antimicrobial agents.

Penicillin-resistant Streptococcus pneumoniae in Argentina: frequent occurrence of an internationally spread serotype 14 clone

Six Latin-American countries participated in an epidemiological surveillance study conducted by the Pan American Health Organization in order to determine the relative prevalence of capsular types and antimicrobial resistance patterns of Streptococcus pneumoniae (SPN) causing invasive infections in children <5 years of age. In Argentina, the incidence of penicillin resistance (PR) was 24.4%, and it was significantly associated with serotype 14 (p < 0.001). The chromosomal DNA of 56 of those SPN isolates, 39 PR and 17 susceptible, was digested with SmaI and resolved by PFGE. Eighty-two percent (32/39) of the PR isolates shared characteristics with the widely spread International Spanish/French clone (clone B). All members of clone B except one expressed serotype 14, with the exception of one isolate that expressed serotype 19F and probably resulted from an in vivo capsular transformation event. Only a single isolate shared features with the 23F International Spanish/USA clone (clone A). The 17 penicillin-susceptible (PS) SPN isolates presented an enormous degree of variation in the chromosomal background, expressing 12 serotypes and 13 PFGE patterns. The data suggest that over 80% of the SPN-PR isolates in Argentina were imported, and this confirms the importance of the geographic spread of SPN clones in South America.

Geographic distribution of penicillin resistance of Streptococcus pneumoniae in Brazil: genetic relatedness

From January 1993 through December 1996, 1,252 Streptococcus pneumoniae strains from different geographic regions of Brazil were studied for penicillin (Pen) susceptibility. All pneumococci were isolated from normally sterile fluids from patients, newborns to 88 years old. Pen resistance (R) had a mean rate of 15.1%, with 14.5% of strains showing intermediate level Pen-R and 0.6% showing high-level Pen-R. Similar Pen-R rates were observed in different regions of the country, in the range of 9.5% to 17.1%. A Pen-R increase was noted from 9.6% in 1993 to 20.6% in 1996. Pen-R was mostly associated to serotypes 6B, 14, 19A, and 23F (89%). Chromosomal DNA relatedness of Pen-R strains was determined by pulsed field gel electrophoresis (PFGE). High genetic diversity was identified, being represented by 27 patterns among the 92 strains. Two important features were observed: the predominance of relatively low-level Pen MIC (range 0.1-0.5 mg/L) in 86 of the 92 strains, and the presence of 60.8% as four major PFGE clusters unique to Brazil. Another feature was the geographic spread of these clusters over large distances in the country. The city of São Paulo seems to be a Pen-R focus (18.4%) in Brazil. Only two strains representing the international clone B widely spread in France, Portugal, and Spain, belonging to serotype 14, were found.

Predominance of the multiresistant 23F international clone of Streptococcus pneumoniae among isolates from Mexico

During a surveillance study to determine the relative prevalence of capsular types of Streptococcus pneumoniae and antimicrobial susceptibility of invasive isolates in children <5 years old in Mexico City, 220 isolates were collected. The serotype 23F was the most common found, followed by types 6A + B, 14, 19F, and 19A. Diminished susceptibility to penicillin was detected in 106 isolates (48.2%), and high penicillin resistance was found in 49 strains (22.2%), 31 belonging to type 23F. Resistance was also observed to erythromycin (13.1%), to chloramphenicol (43.1%), and to cefotaxime (10.9%). No strains were resistant to ofloxacin or vancomycin. Forty-four of the highly penicillin resistant isolates (penicillin MIC > or =2.0 microg/ml) were examined with molecular fingerprinting techniques; 29 (65.9%) of these isolates (all except two strains) were serotype 23F and shared subtype variants of PFGE type A characteristic of the internationally spread Spanish/USA clone of S. pneumoniae. These strains were also resistant to trimethoprim/sulfametoxasole (TMP/SMX), chloramphenicol, and tetracycline, and most of them were susceptible to erythromycin. Another 6 of the highly penicillin-resistant strains (serogroups 9 and 14) showed PFGE fingerprints and antimicrobial susceptibility pattern characteristic of a second internationally spread clone (French/Spanish clone) and carried resistance to penicillin and TMP/SMX. The rest of the 9 penicillin-resistant isolates were represented by 7 distinct additional PFGE types. The findings suggest that almost 80% of all highly penicillin resistant strains may have been "imported" into Mexico.

Penicillin-resistant Streptococcus pneumoniae in Colombia: presence of international epidemic clones. Colombian pneumococcal study group

The global spread of multidrug-resistant Streptococcus pneumoniae clones is well documented in the literature. A study to determine type distribution and antimicrobial susceptibility of invasive pneumococcal isolates from Colombian children under the age of 5 was conducted from 1994 to 1996. Health centers in Santa Fe de Bogota, Medellin, Cali, and other cities collected 409 Streptococcus pneumoniae isolates. Diminished susceptibility to penicillin (DSP) was 15.6%; from these, 11.5% showed intermediate-level resistance (ILR) and 4.1% showed high-level resistance (HLR). Fifty-nine of the DSP isolates were examined by pulse field gel electrophoresis (PFGE). Capsular isolate types were 23F (54%), 14 (24%), 19F (10%), 6B (7%), 9V (3%), and 34 (2%). PFGE analysis revealed that 8 isolates shared the Spanish/USA international clone's characteristic features: PFGE pattern type A, serotype 23F; 87.5% exhibited HLR for penicillin, and all were resistant to trimethoprim/sulfamethoxazole (TMP-SMX), tetracycline, and chloramphenicol. Another 7 isolates showed the French/Spanish international clone's features: PFGE pattern type B, 2 of them being serotype 9V; and 5 type 14; HLR to penicillin was 71%, and all proved resistant to TMP-SMX. A large cluster of 24 isolates (41% of all isolates examined) shared a common PFGE type C, with 14 subtypes; all but one, serotype 34, were serotype 23F and had ILR to penicillin; 58% were resistant to TMP-SMX and 50% to tetracycline, but none presented erythromycin or chloramphenicol resistance. The remaining 20 isolates could be grouped into 12 different PFGE types; ILR was shown in 75% of isolates, 70% were resistant to TMP-SMX and to tetracycline, 15% were resistant to erythromycin, and none were resistant to chloramphenicol. These data suggest that some Colombian isolates are clonally related to two of the well-known international epidemic S. pneumoniae clones.

The contribution of specific pneumococcal serogroups to different disease manifestations: implications for conjugate vaccine formulation and use, part II

To assess whether certain serogroups of Streptococcus pneumoniae are preferentially associated with specific disease manifestations, we analyzed all recent pneumococcal disease studies and assessed the relative frequency of isolation of each serogroup by clinical site (as a proxy for different disease states). In all age groups, serogroups 1 and 14 were more often isolated from blood, and serogroups 6, 10, and 23 were more often isolated from cerebrospinal fluid (CSF); in young children, serogroups 3, 19, and 23 were more often isolated from middle ear fluid (MEF). Serogroups represented in conjugate vaccines were isolated slightly less frequently from CSF than from blood or MEF. Nonetheless, serogroups in the 9-valent conjugate vaccine formulation still comprised approximately 75% of pneumococcal isolates from the CSF of young children in Europe and in the United States and Canada. These analyses indicate that pneumococcal conjugate vaccines could potentially prevent a substantial proportion of episodes of bacteremic disease, pneumonia, meningitis, and otitis media, especially in young children.

Which pneumococcal serogroups cause the most invasive disease: implications for conjugate vaccine formulation and use, part I

We analyzed >70 recent data sets to compare the serogroups causing invasive pneumococcal disease (IPD) with those represented in conjugate vaccine formulations. Five to 8 and 10-11 serogroups comprise at least 75% of pneumococcal isolates from young children and older children/adults, respectively, in each geographic region. Serogroups in the 7-valent formulation (4, 6, 9, 14, 18, 19, and 23) cause 70%-88% of IPD in young children in the United States and Canada, Oceania, Africa, and Europe, and <65% in Latin America and Asia. Serogroups in the 9-valent formulation (7-valent+1, 5) cause 80%-90% of IPD in each region except Asia (66%). Serogroup 1 accounts for >6% of IPD in each region, including Europe, except the United States and Canada and Oceania. In contrast, several serogroups not found in 7-, 9-, and 11-valent conjugate formulations are significant causes of disease in older children/adults. Nevertheless, each conjugate formulation could prevent a substantial IPD burden in each region and age group.

Dissemination of a chloramphenicol- and tetracycline-resistant but penicillin-susceptible invasive clone of serotype 5 Streptococcus pneumoniae in Colombia

A national surveillance conducted in Colombia between 1994 and 1996 identified serotype 5 Streptococcus pneumoniae as the second most frequent cause of invasive disease in children younger than 5 years of age. All 43 serotype 5 isolates collected during this period were shown to be susceptible to penicillin, erythromycin, cefotaxime, and vancomycin, but most (38 of 43, or 88%) were highly resistant to chloramphenicol. In order to clarify a possible genetic relatedness among these isolates, additional microbiological and molecular characterizations were performed. Most (40 of 43, or 93%) of the isolates were found to be resistant to tetracycline. Pulsed-field gel electrophoresis (PFGE) patterns of chromosomal DNAs revealed that all the 43 isolates were closely related and that 38 of the 43 isolates were representatives of a "Colombian clone" of S. pneumoniae isolates which were recovered throughout the 3-year surveillance period from patients in 13 hospitals located in five Colombian cities. Isolates belonging to this Colombian clone were resistant to chloramphenicol and tetracycline, hybridized with the cat and tetM DNA probes in the same 340-kb SmaI fragment, and had identical PFGE patterns after both SmaI and ApaI digestions.

Risk factors and course of illness among children with invasive penicillin-resistant Streptococcus pneumoniae. The Streptococcus pneumoniae Working Group

OBJECTIVES

To assess differences in risk factors, clinical presentation, and course of illness between children infected with penicillin-sensitive and drug-resistant Streptococcus pneumoniae (DRSP).

DESIGN

A retrospective cohort study conducted in Uruguay and Argentina using information from a hospital-based surveillance system. Hospitalized children 5 years of age and younger who had S pneumoniae isolated from a normally sterile site between June 1993 and October 1996 were eligible. Hospital records were linked with surveillance data. Both stratified univariate analysis and logistic regression was completed.

RESULTS

Of the 380 children eligible for the study, 274 records (72%) were available for review. Ninety-nine children (36%) had DRSP; 46 showed intermediate susceptibility (minimum inhibitory concentration, 0.12-1.0 microg/mL) and 53 showed high-level resistance (minimum inhibitory concentration >/=2.0 microg/mL). Children with meningitis were less likely to have DRSP than those with other forms of invasive disease (relative risk = 0. 5; 95% confidence interval [CI], 0.2-0.9). Risk factors associated with DRSP were use of penicillin or ampicillin in the 3 months before illness (odds ratio = 2.9; 95% CI, 1.5-5.7) and possession of private medical coverage (odds ratio = 2.4; 95% CI, 1.2-5.0). Response to therapy, including response to penicillin or ampicillin among children with nonmeningeal invasive disease, course of illness, and clinical outcome did not differ significantly between children infected with penicillin-susceptible or penicillin-resistant isolates.

CONCLUSION

In this study, previous use of penicillin or ampicillin and private medical coverage were associated with having DRSP. Children with nonmeningeal invasive disease responded equally well to penicillin regardless of the penicillin susceptibility of their pneumococcal isolate.

Microbiology of acute otitis media in Costa Rican children

BACKGROUND

Because of the increasing number of resistant middle ear pathogens reported from different centers worldwide, an active surveillance of the microbiology and susceptibility pattern of middle ear pathogens is required for proper antimicrobial recommendations among different regions of the world.

OBJECTIVE

To study the microbiology and susceptibility pattern of middle ear pathogens obtained from Costa Rican children with acute otitis media.

METHODS

Between 1992 and 1997 a diagnostic tympanocentesis was performed in 398 Costa Rican patients with acute otitis media. Middle ear fluid was obtained for culture and minimal inhibitory concentrations were determined by the E-test technique in those isolates obtained between October, 1995, and January, 1997.

RESULTS

The most common pathogens cultured were Streptococcus pneumoniae (30%), Haemophilus influenzae (14%), Staphylococcus aureus (4%) and Streptococcus pyogenes (4%). Moraxella catarrhalis was uncommon. Beta-lactamase production was low (3.7%) among the H. influenzae isolates but frequent among the Staphylococcus aureus (57.1%) and M. catarrhalis (100%) strains. Overall 9 of 46 S. pneumoniae isolates (19.6%) exhibited decreased susceptibility to penicillin of which 8 isolates (17.4%) showed intermediate and one strain (2.2%) high level resistance. Among the penicillin-susceptible S. pneumoniae isolates, susceptibility to the following antimicrobials was: 81%, azithromycin; 89%, clarithromycin; and 100%, ceftriaxone and trimethoprim-sulfamethoxazole (TMP-SMX). Among the penicillin-resistant S. pneumoniae isolates the percentage of susceptible strains was 89% for azithromycin, clarithromycin and ceftriaxone and 67% for TMP-SMX.

CONCLUSIONS

Based on this microbiologic information the agents considered first line drugs in the treatment of acute otitis media in Costa Rica remain amoxicillin or TMP-SMX.

Epidemiology of emerging/re-emerging antimicrobial-resistant bacterial pathogens

The rapid global expansion of bacteria resistant to antimicrobials is the most important development over the past year in emerging bacterial diseases. The critical events are the emergence of Staphylococcus aureus with decreased sensitivity to vancomycin, worldwide resistance to penicillin in Streptococcus pneumoniae, and the remorseless progression of multiply-resistant Mycobacterium tuberculosis. Most startling was the isolation from a human in Madagascar of a plague bacillus possessing a plasmid readily transferable to Escherichia coli, which confers multiple antibiotic resistance. The hospital environment continues to see the transmission of resistant organisms, notably vancomycin-resistant enterococci. Finally, as food markets become more open around the world, food-borne outbreaks of E. coli O157 and cholera demonstrate how difficult it can be to establish effective health and safety barriers.

Multicenter evaluation of antimicrobial resistance to six broad-spectrum beta-lactams in Colombia using the Etest method. The Colombian Antimicrobial Resistance Study Group

The need for comprehensive and quantitative accurate antimicrobial resistance surveillance systems has become acute as a guide to problem recognition and to focus local interventions. A multilaboratory (10 medical centers) Colombia surveillance project was initiated in early 1997 to monitor the potency and spectrum of six (cefepime, cefotaxime, ceftazidime, cefoperazone/sulbactam, aztreonam, and imipenem) broad-spectrum antimicrobial agents tested against 100 organisms per participant center (802 strains). Ten groups of organisms were tested by a reference-quality method (Etest; AB BIODISK, Solna, Sweden) with results validated by concurrent quality control and additional challenge strain analysis. Results from nine qualifying medical centers were tabulated, and 95.7 to 96.8% of quality assurance tests were within expected ranges. Only cefepime (90.1-100.0% susceptible) and imipenem (96.3-100.0%) were active against all Enterobacteriaceae at > 90% of susceptible isolates using the breakpoint concentrations recommended by the National Committee for Clinical Laboratory Standards. Among ceftazidime- (or cefotaxime- or aztreonam-) resistant Enterobacter spp. and Citrobacter freundii, cefepime remained active, but not cefoperazone with sulbactam. Escherichia coli and Klebsiella spp. strains having resistance phenotypes consistent with extended spectrum beta-lactamase production were discovered in approximately 5 to 10% of isolates. All tested drugs except ceftazidime (31.8-57.7% susceptible) were active against > 94% of oxacillin-susceptible staphylococci. Similar rates of resistance (9.1-14.8%) were observed in Pseudomonas aeruginosa for five of six drugs (not cefotaxime; 15.9% of strains were susceptible). Acinetobacter spp. isolates were most susceptible to imipenem (95.8%), cefepime (86.1%), and cefoperazone/sulbactam (83.3%). Overall for the 1997 order of antimicrobial spectrums for these tested compounds was: imipenem (96.6%) > cefepime (93.6%) > cefoperazone/sulbactam (90.5%) > cefotaxime (74.9%) > aztreonam (74.3% for Gram-negative bacilli only) > ceftazidime (73.2%). These data should be used to guide empiric regimens in Colombia, and additionally will provide a resistance statistical baseline to which future studies in this nation can be compared.