Rocco Merolla

Restricted replication of respiratory syncytial virus in human alveolar macrophages

The cellular factors that regulate infection and replication of respiratory syncytial virus (RSV) in human alveolar macrophages were examined. RSV-exposed alveolar macrophages demonstrated a time-dependent expression of viral glycoproteins, maximal by 24 h post-infection resulting in infection of approx. 38% of the cells. Essentially all (33%) of these freshly isolated alveolar macrophages replicated RSV as shown by infectious centre assays. This RSV-permissive subpopulation of alveolar macrophages consisted primarily of major histocompatibility class II-expressing cells as determined by fluorescence-activated cell sorting. Re-infection of alveolar macrophages did not significantly alter the number of cells infected or capable of replicating RSV. However, in vitro differentiation of alveolar macrophages prior to infection resulted in a significant (P < 0.05), time-dependent decrease (approx. sevenfold) in the number of cells that replicated virus. The mechanism by which cellular differentiation restricted RSV replication is unknown. Production of defective interfering particles did not account for this decrease. Alveolar macrophages infected with RSV produce a variety of cytokines potentially contributing to this restricted viral replication. Pretreatment with several of these cytokines did not affect viral infection or replication. However, tumour necrosis factor (TNF alpha) significantly (P < 0.05) decreased viral replication but only by 30 to 60%. Thus RSV replication is reduced by in vitro differentiation of alveolar macrophages and, to a lesser degree, by pretreatment with TNF.

Detection of Pneumocystis carinii among children with chronic respiratory disorders in the absence of HIV infection and immunodeficiency

A nested polymerase chain reaction (PCR) assay was investigated for detection of Pneumocystis carinii in 96 respiratory tract specimens from 82 children, of whom 28 were immunocompetent but with chronic lung disorders (CLD), eight had AIDS and P. carinii pneumonia (PCP), 16 had AIDS but no respiratory symptoms, and 30 were healthy immunocompetent children. Gomori methenamine silver stain (GMS) and indirect immunofluorescence assay (IFA) were performed in parallel. Of 36 specimens from children with CLD, 12 were P. carinii PCR-positive compared to 10 positive by GMS-IFA. Of eight specimens from children with AIDS and PCP, seven were P. carinii-positive by PCR and six by GMS-IFA, and of 22 specimens from HIV-positive children without respiratory symptoms, two were positive by PCR and none by GMS-IFA. P. carinii DNA was also detected by PCR in blood samples from four children with P. carinii-positive nasopharyngeal aspirates. Specimens from healthy children were negative for P. carinii by both PCR and GMS-IFA. Of the seven children with CLD, who were P. carinii-positive, two had clinical and microbiological improvement with co-trimoxazole treatment, two improved initially but relapsed, and one had P. carinii cysts persistently in follow-up specimens despite co-trimoxazole treatment. These results suggest an association between P. carinii and exacerbations of CLD in childhood, in the absence of HIV infection or other immunodeficiency syndromes.

Prevalence of mefE, erm and tet(M) genes in Streptococcus pneumoniae strains from Central Italy.

One hundred and seventy-three Streptococcus pneumoniae strains isolated from surveillance studies conducted in daycare centres were studied. The mefE, erm and tet(M) genes were detected in 16.2, 45.1 and 47.4% of isolates respectively. Agreement between PCR results and antibiotic susceptibility patterns was 100%. Macrolide resistance was due to the presence of erm in 73.6% of strains and to the presence of mefE in the remaining 26.4%. All tetracycline resistant strains carried the tet(M) gene. erm was associated with tet(M) in 98.7% of strains, whereas no isolate carrying mefE carried tet(M). A significant association was found between mefE and serogroup 6 (P < 0.0005) and between erm and tet(M) and serogroup 19 (P < 0.00001).

Resistance Patterns of Streptococcus pneumoniae from Children in Central Italy

Abstract Nasopharyngeal swabs were collected from children aged 3–5 years in central Italy who were attending day-care centres or hospital outpatient clinics. One hundred and twenty-one strains of Streptococcus pneumoniae isolated were tested for susceptibility to penicillin, cefotaxime, erythromycin, clindamycin, tetracycline, chloramphenicol and cotrimoxazole. A high prevalence of penicillin-resistant (14%), erythromycin-resistant (60%) and multiply resistant strains (53%) were found. An unusual finding was that 49 of the 64 (76.6%) multiply resistant strains were penicillin-susceptible, 28 serogroup 6 strains also being resistant to the other antibiotics tested. Such strains have not previously been reported from Italy but have the same features as strains recently found in child carriers in the eastern Mediterranean area.