Trends in antimicrobial resistance and serotype distribution of blood and cerebrospinal fluid isolates of Streptococcus pneumoniae in South Africa, 1991-1998.

OBJECTIVE: Since 1979, the South African Institute for Medical Research (SAIMR) has served as the national reference center for pneumococcal serotyping and monitoring of antibiotic resistance trends. This study documents trends in antimicrobial resistance in pneumococci isolated from blood or cerebrospinal fluid (CSF) between 1991 and 1998 in South Africa. METHODS: Pneumococcal isolates (n = 7406) from either blood or CSF were sent to the SAIMR reference laboratory for serotyping. The isolates were evaluated for resistance to penicillin, chloramphenicol, tetracycline, erythromycin, clindamycin, and rifampicin. RESULTS: Resistance to one or more antibiotics increased significantly from 19% in 1991 to 1994 to 25% in 1995 to 1998 in all ages, and in children from 32% to 38% (P < 10[-6]). Although penicillin resistance did not increase in children (28.1% vs. 28.9%), penicillin resistance in all ages increased from 9.6% to 18.0%. Significant increases in resistance to chloramphenicol, tetracycline, erythromycin, and rifampicin also were seen in both groups. Multiple resistance increased significantly, from 2.2% to 3.8%. The proportion of isolates with intermediate or high-level penicillin resistance remained constant during the surveillance period. Erythromycin resistance, predominantly expressed as simultaneous resistance to erythromycin and clindamycin, increased from 1.6% to 2.6%. The percentage of erythromycin-resistant isolates that were resistance to erythromycin alone increased from 10.6% to 28.7%, suggesting the emergence of mefE-mediated resistance. In children 2 years of age and younger, although serogroup 6 remained the most common, there were significant increases in serogroups 19, 18, and 13. The percentage of the total invasive pneumococcal disease in this population that is caused by serogroups found in the nonavalent pneumococcal conjugate vaccine (serogroups 1, 4, 5, 6B, 9V, 14, 18C, 19F, 23F) increased from 72% to 91%. CONCLUSIONS: Antibiotic resistance in the pneumococcus is increasing in South Africa, although the proportion of strains with high-level penicillin resistance has not increased. New conjugate vaccines may not only decrease the burden of all pneumococcal disease but, in addition, lower the incidence of antibiotic-resistant disease in South Africa.

Prevalence of nasopharyngeal antibiotic-resistant pneumococcal carriage in children attending private paediatric practices in Johannesburg.

OBJECTIVES: To determine the nasopharyngeal carriage rate, serogroups/types, and antibiotic resistance of Streptococcus pneumoniae in children attending paediatric practices in the private sector in Johannesburg and to relate patterns of resistance to antimicrobial exposure and other demographic characteristics in individual children. DESIGN: A total of 303 children aged from 1 month to 5 years were recruited from eight private paediatric practices in northern Johannesburg. Nasopharyngeal samples were taken and parent interviews were conducted. RESULTS: Pneumococci were isolated from 121 children (40%). The most common serotypes were 6B, 19F, 6A, 23F, 14, and 19A. Carriage was significantly associated with prior hospital admission (odds ratio 1.89) and day care attendance (odds ratio 2.31) and was negatively associated with antibiotic use within the previous 30 days. Antibiotic resistance was found in 84 isolates (69.4%); 45 (37.2%) were multiply resistant. One-third of the pneumococci showed intermediate level resistance to penicillin and 12.4% were highly resistant. There was a high level erythromycin resistance in 38% of the isolates. A total of 94/214 children (42%) had recently used antibiotics and were four times more likely to carry antibiotic-resistant pneumococci (P < 0.05). CONCLUSION: Pneumococcal resistance was significant in this group of children with easy access to paediatric services and antibiotic use. The implication of such high resistance for the treatment of pneumococcal diseases is that high-dose amoxicillin is the preferred empirical oral therapy for treatment of otitis media. Ceftriaxone or cefotaxime should be used in combination with vancomycin for the treatment of meningitis until a cephalosporin-resistant pneumococcal cause is excluded. Intravenous penicillin or ampicillin will successfully treat pneumococcal pneumonia in this population. Antimicrobial resistance among pneumococci colonising children in the private sector has increased dramatically in recent years.

Immunogenicity and impact on nasopharyngeal carriage of a nonavalent pneumococcal conjugate vaccine.

The safety, immunogenicity, and impact on carriage of a nonvalent pneumococcal vaccine given at ages 6, 10, and 14 weeks were examined in a double-blind, randomized, placebo-controlled trial in 500 infants in Soweto, South Africa. No serious local or systemic side effects were recorded. Significant antibody responses to all pneumococcal serotypes were observed 4 weeks after the third dose. Haemophilus influenzae type b polyribosylribitol phosphate (geometric mean titer, 11.62 microg/mL) and diphtheria (1.39 IU/mL) antibodies were significantly higher in children receiving pneumococcal conjugate, compared with placebo recipients (4.58 microgram/mL and 0.98 IU/mL, respectively). Nasopharyngeal carriage of vaccine serotypes decreased in vaccinees at age 9 months (18% vs. 36%), whereas carriage of nonvaccine serotypes increased (36% vs. 25%). Carriage of penicillin-resistant pneumococci (21% vs. 41%) and cotrimoxazole-resistant pneumococci (23% vs. 35%) were significantly reduced 9 months after vaccination, compared with controls.

Use of Dorset egg medium for maintenance and transport of Neisseria meningitidis and Haemophilus influenzae type b.

Studies of bacterial meningitis are hampered by the inability to maintain the viability of etiological agents during transport to reference laboratories. The long-term survival rate of 20 isolates of Neisseria meningitidis and Haemophilus influenzae type b (Hib) on Dorset egg medium, supplemented Columbia agar base medium, chocolate agar, and Amies medium was compared with that on 70% GC agar (chocolate) transport medium. N. meningitidis isolates were also inoculated onto 5% horse blood agar, and Hib was inoculated onto Haemophilus test medium. All of the N. meningitidis isolates remained viable on Dorset egg medium for 21 days; viability on the other media was poor after only 7 days. Recovery rates of Hib isolates were similar on Dorset egg and Haemophilus test media (100% after 21 days) and significantly better than on the other media. Dorset egg medium is inexpensive and easy to make and may be invaluable for studies of bacterial meningitis in developing countries.

Long-term survival of Streptococcus pneumoniae at room temperature on Dorset egg medium.

Forty-five isolates of Streptococcus pneumoniae were inoculated on Dorset egg and supplemented Columbia agar base media, incubated overnight at 37 degrees C, and then kept at room temperature (RT; 21 degrees C) or 4 degrees C. Long-term viability was best at RT for both media, with all isolates remaining viable on Dorset egg medium for 44 days; viability was 90 and 57% on Columbia agar base medium after 7 and 30 days. We recommend the use of Dorset egg medium for the maintenance of pneumococci at RT.