Pneumococci resistant to extended-spectrum cephalosporins in South Africa

The management of bacterial meningitis in children

Bacterial meningitis is still a major cause of death and disability in children worldwide. With the advent of conjugate vaccines against the three major pathogens, the burden of disease is increasingly concentrated in developing countries that cannot afford the vaccines. Antibiotic resistance is an increasing problem; in developed countries, high-level resistance to beta-lactams among Streptococcus pneumoniae necessitates the addition of vancomycin to third-generation cephalosporins. In many developing countries, the problems are more fundamental. Increasing resistance of S. pneumoniae to penicillin and chloramphenicol and of Haemophilus influenzae to chloramphenicol means that many children with bacterial meningitis receive ineffective treatments, as third-generation cephalosporins are often unavailable or unaffordable. Case fatality rates are as high as 50% and neurological sequelae occur in one-third of survivors. The use of corticosteroids in meningitis is controversial; the evidence that they protect against neurological complications of childhood meningitis (particularly severe hearing loss) is strongest when: meningitis is caused by H. influenzae type b; dexamethasone is given before the first dose of antibiotics; a bactericidal antibiotic such as a third-generation cephalosporin is used; and in the early stages of the infection. There are few controlled clinical trials on which to base recommendations about other adjuvant therapy for meningitis. Avoidance of secondary brain injury from hypoxia, hypotension, hypo-osmolarity and cerebral oedema, hypoglycaemia or convulsions is essential for a good outcome. The problem of bacterial meningitis will only be solved if protein-conjugate vaccines (or other effective vaccine strategies) against S. pneumonia, H. influenzae and epidemic strains of Neisseria meningitidis are available to all the world's children. Making third-generation cephalosporins affordable in the developing world is also a necessary intervention, but better antibiotics will not overcome the problems of poor access to hospitals and late presentation with established brain injury, and will inevitably bring further pressure for antimicrobial resistance.

Clinical isolates and nasopharyngeal carriage of antibiotic-resistant Streptococcus pneumoniae in Hospital for Infectious Diseases, Sofia, Bulgaria, 1991-1993

The antimicrobial resistance of Streptococcus pneumoniae was surveyed in 1991-1993 at the Hospital for Infectious Diseases in Sofia, Bulgaria. Pneumococcal isolates were collected from routine clinical specimens and from nasopharyngeal secretions of inpatient carriers. The incidence of penicillin-resistant S. pneumoniae (PRSP) was 24.3% among clinical samples and nasopharyngeal carriage of PRSP was as high as 40% among children. Penicillin-resistant strains were more frequently resistant to non-beta-lactam antibiotics than were penicillin-sensitive strains. More than half of the PRSP strains were multiply resistant. On the basis of MIC values of ampicillin, it was established that ampicillin was not superior to penicillin. The MICs of five cephalosporins were found to increase in parallel with the MICs of penicillin G. Some of the pneumococcal strains that were highly penicillin-resistant were also resistant to cefotaxime/ceftriaxone (MIC = 1-4 micrograms/ml), but the number of strains was small. On the basis of MIC values of cefotaxime and ceftriaxone for strains from cerebrospinal fluid, both antibiotics may be suitable alternatives for treating meningitis due to strains with resistance to penicillin.

Determination of penicillin susceptibility of Streptococcus pneumoniae using the polymerase chain reaction

AIM

To develop a polymerase chain reaction (PCR) based method to detect penicillin susceptibility in isolates of Streptococcus pneumoniae (SP).

METHOD

PCR primers were designed to amplify differential nucleotide sequences of the penicillin-binding protein (PBP) genes 2b, 2x, and 1a in penicillin susceptible and resistant strains of SP. Primers derived from the PBP 2x and 2b genes were designed to amplify products from penicillin susceptible S pneumoniae (PSSP), whereas primers derived from the PBP 1a gene were designed to amplify gene sequences of penicillin resistant S pneumoniae (PRSP).

RESULTS

Two hundred and thirty clinical isolates of SP from the USA, UK, Kenya, Romania, and the Kingdom of Saudi Arabia were tested. Of the isolates, 116 were penicillin susceptible, 65 were intermediately resistant, and 49 were highly resistant. PCR identified 108 (93%) of 116 of PSSP isolates, 55 (85%) of 65 intermediately resistant isolates, and all of the 49 highly resistant isolates of SP. The susceptibility of 16 (7%) isolates could not be determined using PCR. All of these 16 isolates had a minimum inhibitory concentration (MIC) of penicillin < 1 mg/l. None of the highly resistant isolates was identified as penicillin susceptible by PCR, although two of the isolates with intermediate resistance (MIC = 0.125 mg/l) were.

CONCLUSION

Using primers that differentially identify the genotypes of susceptible and resistant strains of SP, PCR provides a rapid method for determining the penicillin susceptibility of SP isolates and could potentially be used for testing clinical samples.

Penicillin-resistant pneumococci--an emerging threat to successful therapy

Pneumococci highly resistant to penicillin G [minimum inhibitory concentration (MIC) > or = 2 mg L-1] have become prevalent in many parts of the world since their emergence and spread in the late 1970s. In the USA, such organisms are seen primarily in two populations: infants and children, and adults with AIDS. Surveys in both rural and urban areas have revealed presence of these organisms, as well as an increasing frequency of Streptococcus pneumoniae strains relatively resistant to penicillin (MIC 0.1-1.0 mg L-1--now defined by some as 'intermediate' resistance). Predisposing factors are not yet clear. Prior antimicrobial therapy was given to some of the children and most of the adults who are colonized or infected with resistant strains. Prior or concurrent use of cotrimoxazole prophylaxis for Pneumocystis carinii pneumonia has been frequent in our cases in adults, most of whom had a concurrent diagnosis of AIDS. Children with disease often have a history of long-term prophylaxis with a beta-lactam drug (for sickle cell disease, etc). Many strains are also resistant to newer cephalosporins like cefotaxime and ceftriaxone (MIC > or = 2 mg L-1). The organisms are frequently multi-resistant, with high MIC values common as well for chloramphenicol and variable for tetracycline, macrolides, cotrimoxazole, and fluoroquinolones. Only to vancomycin are the organisms consistently susceptible. These findings raise alarms about the future of pneumococcal disease in both community and nosocomial disease. Increasing prevalence in otitis and pneumonia in children and in community-acquired pneumonia in adults may lead to use of vancomycin as empirical therapy for these clinical situations. This would increase the selective pressure for emergence of vancomycin-resistant organisms, whether S. pneumoniae or others. Moreover, the pneumococcus was a common cause of hospital infection prior to the introduction of penicillin. The potential now exists for nosocomial pneumococcal infection again to become a feared and ominous occurrence.

Capsular serotypes and antibiotic sensitivity of Streptococcus pneumoniae isolated from primary-school children

A total of 1049 primary-school children in 18 schools were screened for carriage of Streptococcus pneumoniae. Data on family size, antibiotic use, travel and hospital admissions were collected. Pneumococcal serotyping and sensitivity tests were performed. One third of children were found to be pneumococcal carriers. Ten of 344 isolates were penicillin-resistant (2.9%). Apart from resistance to trimethoprim and ciprofloxacin, resistance rates in penicillin-sensitive strains were low. Among penicillin-resistant strains (PRP), co-resistance to trimethoprim, chloramphenicol and tetracycline was common. Cefotaxime-resistance was seen in 90% of PRP. Although 24 serotypes were represented, groups 6, 19 and 23 accounted for 55% of strains. Serogroup 23 strains were significantly more likely to be penicillin-resistant than other groups/types. Clustering of strains by serotype and antibiotic resistance was seen in several schools. No association with foreign travel, family size or age of siblings was seen and penicillin resistance was not associated with prior antibiotic use. However, hospital admission was significantly associated with carriage of PRP. The implications of detecting PRP in the community are discussed.

Prevalence of antimicrobial resistance of Streptococcus pneumoniae in southwest Germany as determined by the E test

We have studied the prevalence of anti-microbial resistance of Streptococcus pneumoniae in Southwest Germany. One hundred seventy-four clinical isolates of pneumococci collected from hospitalized patients between October 1992 and April 1994 were used for MIC determinations. MICs for penicillin, ceftriaxone, erythromycin, and rifampicin were assessed by the E test. Eleven of the 174 strains (6.3%) were intermediately resistant to penicillin (MIC between 0.1 and 1.0 microgram/ml) and four of the 174 strains (2.3%) were intermediately resistant to ceftriaxone (MIC between 0.1 and 1.0 microgram/ml). All four isolates with a reduced susceptibility to ceftriaxone also demonstrated intermediate resistance to penicillin. Six of the 174 strains (3.5%) were highly resistant (MIC > or = 8 micrograms/ml) to erythromycin. Resistance to rifampicin was not observed. Our results demonstrate that pneumococcal resistance to penicillin and erythromycin has increased markedly in Germany over the last decade. Our findings underline the need for continuous surveillance of antimicrobial resistance of Streptococcus pneumoniae.