The increasing prevalence of multidrug-resistant nosocomial pathogens such as Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae poses a great challenge to the treating physicians. The paucity of newer effective antimicrobials has led to renewed interest in the polymyxin group of drugs, as a last resort for treatment of gram-negative bacterial infections. There is a dearth of information on the pharmacological properties of colistin, leading to difficulties in selecting the right dose, dosing interval, and route of administration for treatment, especially in critically-ill patients. The increasing use of colistin over the last few years necessitates the need for accurate and reliable in vitro susceptibility testing methods. Development of heteroresistant strains as a result of colistin monotherapy is also a growing concern. There is a compelling need from the clinicians to provide options for probable and possible colistin combination therapy for multidrug-resistant bacterial infections in the ICU setting. Newer combination drug synergy determination tests are being developed and reported. There are no standardized recommendations from antimicrobial susceptibility testing reference agencies for the testing and interpretation of these drug combinations. Comparison and analysis of these reported methodologies may help to understand and assist the microbiologist to choose the best method that produces accurate results at the earliest. This will help clinicians to select the appropriate combination therapy. In this era of multidrug resistance it is important for the microbiology laboratory to be prepared, by default, to provide timely synergistic susceptibility results in addition to routine susceptibility, if warranted. Not as a favour or at request, but as a responsibility.

Background & objectives:Streptococcus pneumoniae is a major cause of morbidity and mortality especially in children less than five years, particularly in India. We present data on S. pneumoniae infections in children less than five years age group, with response to its serotype distribution, antibiotic resistance profile and available vaccines expected coverage.Methods:Children aged less than five, who were suspected for invasive pneumococcal disease were included in the study and their sterile body fluids were investigated for the presence of S. pneumoniae. Invasive S. pneumoniae isolates from sterile body fluids were identified by bile solubility and optochin susceptibility test. Pneumococcal serotyping was performed with co-agglutination technique and reconfirmed with multiplex PCR.Results:The most common pneumococcal serotypes causing invasive infections in children less than five years of age were 14, 19F, 5, 6A and 6B. Of the 114 S. pneumoniae isolates studied, 110 (96.4%) were non-susceptible to co-trimoxazole and 30 per cent were non-susceptible to erythromycin, 5.2 per cent of the isolates were non-susceptible to penicillin and only 0.8 per cent was non-susceptible to cefotaxime.Interpretation & conclusions:Our results indicate that PCV-10 can protect against 64 per cent of serotypes causing invasive pneumococcal infections. Use of PCV-13 in this region can provide increase in protection upto 74.6 per cent against serotypes causing invasive pneumococcal infections. Incorporating PCV-13 in the Universal Immunization Programme may provide incremental protection against IPD serotypes in the southern region of the country.