The development of significant mechanisms of resistance to beta-lactam antibiotics in Pseudomonas aeruginosa in cystic fibrosis (CF) patients have been studied in ten CF patients during a two week course of anti-pseudomonal beta-lactam antibiotic therapy. Sputum samples were collected on days 1, 7 and 15. Entire homogenized sputum samples were examined directly for the number of bacteria resistant to different levels of antibiotics. This allowed the detection of pre-existing resistant subpopulations of bacteria as well as following the changes in beta-lactam antibiotic susceptibility during treatment. P. aeruginosa isolates were characterized by means of sero-grouping, phage- and pyocin-typing. Outer membrane proteins of paired sensitive and resistant strains were characterized. Sonicated extracts of cells were assayed for basal and induced beta-lactamase activity. Beta-lactamase activity was further characterized by isoelectric focusing and inhibition profiles. Our observations were in accordance with the hypothesis that the sensitive inducible population was overrun by the pre-existing resistant subpopulation, during treatment. The resistant in-vivo selected P. aeruginosa population exhibited stable partially derepression but the beta-lactamase inhibitor tazobactam restored beta-lactam antibiotic activity.

The presence of both K and O antigens of Klebsiella aerogenes was found necessary to protect the organism from either complement-mediated serum killing or phagocytosis in the absence of specific antisera. Optimal phagocytic ingestion of K. aerogenes NCTC 5055 could be achieved in the presence of either anti-K or anti-O sera or to a much smaller extent in antisera raised against a rough unencapsulated mutant (M10B) derived from NCTC 5055. Anti-O sera failed to opsonize a clinical klebsiella isolate (DL1) possessing immunologically identical lipopolysaccharide, but did so when the amount of capsule was physically reduced. The serum sensitivity of the encapsulated strains was unaffected by the addition of specific antisera. Fresh serum was bacteriostatic for an unencapsulated smooth mutant (M10) derived from NCTC 5055. This bacteriostatic effect was reduced by heat-inactivation of the serum or by the addition of anti-O serum. M10 was rendered sensitive to the bactericidal action of serum in the presence of antisera raised against M10B or after chelation with MgEGTA to isolate alternative complement pathway activity. The rough unencapsulated mutant (M10B) was rapidly killed by fresh serum, an effect which could be delayed by chelation with MgEGTA. The serum sensitivity of M10B was unaffected by the presence of anti-M10B sera. Thus, the O antigen, unlike the K antigen, of these klebsiella strains is not antiphagocytic but it does confer some protection against the rapid bactericidal activity of serum complement.

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BackgroundOxytocin is the gold standard drug for the prevention of postpartum haemorrhage, but limitations in cold chain systems in resource-constrained settings can severely compromise the quality of oxytocin product available in these environments. This study investigated the perspectives and practices of stakeholders in low and lower-middle income countries towards oxytocin, its storage requirements and associated barriers, and the quality of product available.MethodsQualitative inquiries were undertaken in Ethiopia, India and Myanmar, where data was collected through Focus Group Discussions (FGDs) and In-Depth Interviews (IDIs). A total of 12 FGDs and 106 IDIs were conducted with 158 healthcare providers (pharmacists, midwives, nurses, doctors and obstetricians) and 40 key informants (supply chain experts, program managers and policy-makers). Direct observations of oxytocin storage practices and cold chain resources were conducted at 51 healthcare facilities. Verbatim transcripts of FGDs and IDIs were translated to English and analysed according to a thematic content analysis framework.FindingsStakeholder awareness of oxytocin heat sensitivity and the requirement for cold storage of the drug was widespread in Ethiopia but more limited in Myanmar and India. A consistent finding across all study regions was the significant barriers to maintaining a consistent cold chain, with the lack of refrigeration facilities and unreliability of electricity cited as major challenges. Perceptions of compromised oxytocin quality were expressed by some stakeholders in each country.ConclusionKnowledge of the heat sensitivity of oxytocin and the potential impacts of inconsistent cold storage on product quality is not widespread amongst healthcare providers, policy makers and supply chain experts in Myanmar, Ethiopia and India. Targeted training and advocacy messages are warranted to emphasise the importance of cold storage to maintain oxytocin quality.

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