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We wish to raise a few concerns regarding the study reported by Rahman and colleagues.1
We found it surprising that only five species of microorganisms were isolated in this series of over 1000 blood cultures obtained from neonates with sepsis. Similar studies done in other major cities of Pakistan, with much smaller sample sizes, have shown a wider spectrum of pathogens. Anwer et al2 showed 11 species types in 109 blood cultures, Bhutta and Yusuf3 showed 13 species types in 38 cultures, Khan and Akram4 showed more than eight different species types from 89 cultures, and Bhutta5 reported 11 species types in a series of 276 positive blood cultures. In addition to the five species causing neonatal sepsis reported by Rahman et al (Esherichia coli 36.6%, Staphylococcus aureus 29.5%, Pseudomonas 22.4%, Klebsiella 7.6%, and Proteus 3.8%), all the other investigators have also reported Serratia spp and Enterococcus, and most reported Streptococcus pneumoniae, Salmonella spp, and group B Streptococcus. Although the authors do not clearly state whether they excluded hospital acquired infections in their series, the studies reported by Bhutta5 did exclude nosocomial infections.
The antimicrobial susceptibility data reported by Rahman et al are not interpretable as the number of microorganisms on which antimicrobial susceptibility testing was performed is not presented. In addition, the susceptibility results are not internally consistent; 60% of the Staphylococcus aureus tested are reported to be ampicillin sensitive but only 27% were Amoxicillin + Clavulanate (Augmentin) sensitive. This represents a highly unusual susceptibility result with a high percentage of S aureus not producing beta-lactamase enzymes to inactivate penicillin (ampicillin), but still showing resistance to a penicillin-beta-lactamase-inhibitor combination such as Augmentin. We wonder if the 60% reported sensitivity of S aureus to ampicillin is erroneous since the vast majority of S aureus, even in developing countries, are now penicillin (ampicillin) resistant.5–8 We also find the 73% resistance rate of S aureus to amoxicillin-clavulanate (which is equivalent to methicillin resistance for S aureus) surprisingly high, and question if this indicates the presence of hospital acquired infections in this series.
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