In our current study, most common microorganism isolated from the patient’s sample was gram-positive MSSA, with similar results seen in other studies [20, 21, 51]. However, in other studies, gram negative bacteria appear more common that gram-positive bacteria [32]. This may well reflect different bacteria seen in different hospital care settings with different patient populations. In our study, most of the patients were suffering from bone diseases and mostly MSSA or gram-positive bacteria were involved in osteomyelitis and in bone infections [52]. The second most common bacteria found in our study was E. coli, similar to another study conducted in a tertiary care hospital in India [20] but different from another study conducted in England [21].
A high proportion of patients in our study received antibiotics before the availability of culture results, similar to other studies [53]. However, different to a recent study in South Africa where 83% of antibiotics were modified following sensitivity reports [54]. Consequently, prescribing behavior may be due to a desire to prevent patients getting severe infections without waiting for sensitivity reports. However, the empiric therapy can subsequently be adjusted according to the culture sensitivity reports to help reduce unnecessary prescribing of particularly broad spectrum antibiotics and associated costs. The most commonly used antibiotics for empiric treatment in our study were cefoperazone + sulbactam followed by amikacin. This is in contrast with the high use of piperacillin+tazobactam and meropenem as empiric therapy in other studies [20], as well as the high use of ceftriaxone in the recent point prevalence study in Pakistan [55]. This may be due to the ready availability of cefoperazone + sulbactam in GTTH and less resistance against microbes, and the use of amikacin may be due to the high prevalence of E. coli with amikacin have good therapeutic coverage against E. coli. However, this needs further analysis. We are aware that the main reasons for selecting antibiotics for empiric treatment needs to be investigated further to improve future antimicrobial use in this and other hospitals in Pakistan [56].
For definitive treatment, the most common antibiotic prescribed was linezolid, which contrasts with meropenem in another published study [20]. This may well be due to the high prevalence of MSSA in our study and that linezolid is seen to have good coverage against MSSA. However, again this needs further investigation [56]. In this study, the highest use of antibiotics was seen in ICU which was similar to the results observed in Kenya and Switzerland [35, 57], with high rates of antibiotic use in ICUs seen in the recent PPS study in Pakistan [37]. Overall, the extensive use of broad-spectrum antibiotics in definitive treatment could be explained by high bacterial resistance rates [58]. Antibiotic resistance may be reversed if the over-use of antibiotics among hospitals in Pakistan can be decreased.
Encouragingly in our study, empiric therapy was adjusted in 68.9% of the patients greater than the study conducted by Chuodhary et al (47.27%) [20]; however, this is less than the study conducted by Berild et al (88%) [25]. Adjustments were mostly undertaken in gram-negative microorganism compared with gram-positive microorganism similar to the study by Berild et.al [25]. We do not know why the results of culture reports were ignored by some physicians in our study. This may be because physicians mostly rely on the apparent clinical situation of the patient rather than the result of culture reports [32]. However, this will be investigated further in future studies as this is a concern.
In our study, it was observed that no national or international guidelines were available in hospital to guide empiric therapy [59]. This again needs to be urgently addressed as the high use of unnecessary antibiotics increases AMR rates [60], with adherence to guidance known to improve future antibiotic use and is increasingly considered as a robust measure of the quality of prescribing [13, 38, 61-64]. Our results suggest the urgent need to develop guidelines as well as instigate antimicrobial stewardship programmes (ASPs) in this hospital to reduce the unnecessary use of antibiotics [65]. This also applies to other hospitals in Pakistan to help improve future antimicrobial prescribing in hospitals [66].
Another major concern in our study was the high use of parenteral antibiotics (81.8%) similar to other studies [67]. High use of parenteral antibiotics may well reflect physician and patients’ views that the IV route is more effective compared with the oral route [68]. Whilst the parenteral route was more preferable in critically ill patients such as ICU patients where patients are often unable to take oral medicines, or in life threatening indication where no oral equivalent is available [68], the oral route is generally preferable where possible as it reduces the risk of cannula related infection and thrombophlebitis as well as reducing length of stay and ultimately the overall cost of treatment [62, 68-72]. This is helped by the fact that many antibiotics are now available for switching as they have more than 90% bioavailability in their oral form. These include linezolid, fluoroquinolones, doxycycline, metronidazole and rifampicin [68].
The consumption of antibiotics decreased by 13.8% with definitive treatment compared with empirical treatment, similar to findings of Berild et al [73]. Encouragingly as well, the cost of antibiotics used in definitive therapy was 8.2% less than empiric therapy, agin similar to findings of Berild et al [25]. The true cost savings may well be higher as the early availability of culture sensitivity reports decreased the length of stay, which would ultimately decrease overall cost of patient care similar to the findings of Stevenson et al in 2012 [74].
It was also encouraging to see that only 3.3% of the antibiotics were prescribed by their brand name as generic medicines tend to be considerably less expensive [75-78]. The rates of INN prescribing in this hospital are considerably less than seen in studies conducted in Karachi (12.26%), Hyderabad (12%), Bangladesh (78%) and in Islamabad (23%) [79-82]. Higher rates can be achieved through more stringent bioequivalent studies given some of the concerns as well as generally encouraging INN names to be taught in medical and pharmacy schools similar to the UK and continued post qualification [83-86].
In this study, the most common gram-negative microbe was E. coli. Encouragingly, antibiotic sensitivity test showed that E. coli showed maximum (more than 75%) sensitivity to fosfomycin (100%), colistin (95.8%), polymyxin-b (93.7%), tigecycline & nitrofurantoin (92.8%), amikacin (86%), imipenem (82.5%), erythromycin (80%), chloramphenicol (79.4%) and meropenem (78%). However, Nirangan et al (2014) showed a maximum sensitivity of imipenem (98.9%), amikacin (82.6%), nitrofurantoin (82.1%),and Piperacillin + tazobactam (78.2%) for E. coli [87] and Gales et al showed a maximum sensitivity to aztreonam (78.8%), cefoxitin (85.8%), ceftriaxone (75.3%), ceftazidime (82.1%), cefepime (84.1%), gentamicin (81.2%), tobramycin (75.7%) and more than 90% in piperacillin+tazobactam (90.5%), imipenem (99.6%), meropenem (99.9%), amikacin (98.6%) and colistin (99.8%) for E. coli [88]. We will be monitoring this closely in the future to help further guide antibiotic choices.
The most common gram-positive microbe was MSSA with antibiotic sensitivity testing showed that MSSA had maximum (more than 75%) sensitivity to cefoxitin (100%), vancomycin (100%), linezolid (95.7%), tigecycline (95.4%), chloramphenicol (94.1%), amikacin (90.1%), minocycline (89.7%), rifampicin (88.5%), gentamicin (75.9%), clindamycin (75.1%) and ceftriaxone (75%). However, Mir et al (2016) showed a maximum sensitivity of vancomycin, linezolid, rifampicin, chloramphenicol, clindamycin, amikacin, fusidic acid and gentamicin in the case of MSSA i.e. 100%, 98.9%, 95.7%, 94.7%, 86.2%, 84%, 83% and 76.6% respectively [89]. Our findings are a concern especially with some strains of MSSA showing resistance to linezolid which may well be due to the overuse of linezolid, and we will also be investigating this further.
We are aware of a number of limitations with this study. Firstly, no standard antibiotic guidelines were available for the selection of appropriate empiric and definitive therapy in he hospital. Consequently, it was impossible to determine physician adherence with hospital guidelines. Nonetheless, we believe this study was the first step to identifying the prescribing pattern of physicians after the availability of culture sensitivity reports. Secondly, our study was an observational study; consequently, we did not interfere with physician prescribing trends in the selection of antibiotic treatment. However, in the future, the impact of the involvement of a pharmacist or other key stakeholders actively involved in guiding antibiotic selection in hospitals will be investigated. Lastly, to the best of present knowledge, we believe no such research has been undertaken to date in Pakistan with a special focus on culture sensitivity reports; consequently, we were unable to compare our results with any existing studies in Pakistan.
In spite of these limitation, we believe our findings are robust with this study highlighting the impact of culture sensitivity reports on the antibiotic use as well as the significance of culture guided therapy on definitive versus empiric treatment in Pakistan. In addition, this study highlighted the need for antibiotic guidelines for the selection of appropriate antibiotics in empiric and in definite treatment which will be helped by the instigation of ASPs in this hospital and wider.