Ceftaroline activity on certain respiratory tract and wound infection agents at the minimum inhibitory concentration level

Introduction: The aim of this study was to investigate the effectiveness of ceftaroline against agents frequently isolated from respiratory tract and wound infections. Methodology: The study included a total of 250 strains isolated from various clinical specimens, among which were Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus dysagalactiae, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catharralis. The bacteria were identified using the matrix-assisted laser desorption/ionization time-of-flight method and conventional methods. The bacteria’s antibiotic susceptibility was tested using appropriate broth microdilution. Mueller-Hinton broth with 4% lysed horse blood, Haemophilus test medium broth, and Mueller-Hinton broth were used. Ceftaroline fosamil results at the minimum inhibitory concentration (MIC) were evaluated using Clinical and Laboratory Standards Institute (CLSI) criteria. For quality assurance, E. coli ATCC 35218, S. aureus ATCC 29213, S. aureus ATCC 43300, S. pneumoniae ATCC 49619, H. influenzae ATCC 49766, H. influenzae ATCC 10211, and H. influenzae ATCC 49247 standard strains were used. Results: According to CLSI criteria, resistance was not detected in any strains. Due to the absence of CLSI criteria for M. catharralis, the susceptibility state for this bacterium was not evaluated. The various strains’ MIC50–MIC90 values were as follows: for S. pyogenes, 0.015– 0.06; for S. agalactiae, 0.03–0.125; for S. dysagalactiae, 0.03–0.06; for S. pneumoniae, 0.06–0.125; for H. influenzae, 0.015–0.125; and for M. catharralis, 0.5–1. Conclusions: The results indicate that ceftaroline is quite effective against bacteria that are frequently isolated from respiratory tract and wound infections.


Introduction
Respiratory tract and wound infections are the most commonly encountered infections in the community.Community-acquired pneumonia is a major cause of morbidity and mortality throughout the world [1,2].In addition to fatal respiratory tract infections, there are wound infections reported that are unresponsive to empiric treatment [3].Complicated wound infections can require inpatient treatment and surgical intervention, and can frequently cause lifethreatening conditions.Antibiotics continue to be important for treating infections of these kinds; hence, new treatment options must be developed to prevent emerging resistance [4].Because of these considerations, there will continue to be studies to observe developing antibiotic resistance and to identify new and more efficient treatment options [2,3].As part of a new generation of cephalosporins, ceftaroline fosamil is a broad-spectrum antibiotic approved by the United States Food and Drug Administration (FDA) for the treatment of respiratory tract and wound infections [5][6][7].Our study aimed to investigate the effectiveness of the new generation of cephalosporins such as ceftaroline against frequently encountered respiratory tract and wound infection agents using the microdilution method.

Bacteria isolation
The study included a total of 250 strains, including Streptococcus pyogenes (n = 49), S. agalactiae (n = 98), S. dysagalactiae (n = 12), S. pneumoniae (n = 29), Haemophilus influenzae (n = 45), and Moraxella catharralis (n = 17), isolated from various clinical samples between 2012 July and 2014 July (Table 1).Only one bacterial strain was studied from any given patient, and repeating strains were skipped.Bacteria were identified using conventional tests (the pyrrolidonyl arylamidase [PYR] test, the Christie Atkins Munch-Petersen (CAMP) test, and satellite and hockey puck test ) as well as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) (BioMérieux, Marcy L'Etoile, France).MALDI-TOF MS fingerprinting is a method used for the classification and identification of microorganisms with applications in clinical diagnostics.It allows the analysis of molecules with higher masses, while mass spectrometry detects the mass-to-charge ratio of a bioanalyte and provides bacterial spectra within minutes.A database of known organisms is used to match the isolate under investigation, providing a matching score based on identified masses and their intensity correlation.As noted by De Carolis et al., this technology is rapid, robust, customizable pursuant to the needs of the laboratory, more cost effective than current phenotypic testing methods despite the initial cost of the instrument, and, perhaps most importantly, easy to use [8].

Susceptibility study
For S. pneumoniae and the A, B, and C groups of β-hemolytic streptococci, a Mueller-Hinton broth with 4% lysed horse blood was used.For H. influenzae, a Haemophilus test medium was made by mixing Mueller-Hinton broth powder and yeast extract with 4% lysed horse blood, while for M. catharralis, a Mueller-Hinton broth was used.A ceftaroline (Zinforo, AstraZeneca, London, UK) 4,096 µg/mL stock solution was made by dissolving powder in dimethyl sulfoxide (DMSO).Standard 96-well microdilution plates were used, with 100 µL of broth placed in each well and serial dilutions made until the final dilution was achieved.The antibiotic dilution ranges in the wells were 0.003-2 µg/mL.In every plate, positive-and negative-control wells were used.For the inoculum, suspensions were prepared with a turbidity of 0.5 colony-forming units (CFUs)/mL using fresh cultures.All except the negative control wells were inoculated with 100 µL for each 1/100 dilution.The streptococci strains and H. influenza were incubated in 5% carbon dioxide (CO 2 ), and M. catharralis was incubated in an ambient atmosphere incubator, all for 24 hours.The respective strains' minimum inhibitory concentration (MIC) values were established using 2013 Clinical and Laboratory Standards Institute (CLSI) breakpoint values, and both MIC 50 and MIC 90 values were calculated [9]. For

Results
The strains included in the study comprised 49 S. pyogenes, 98 S. agalactiae, 29 S. pneumoniae, 12 S. dysagalactiae, 45 H. influenzae, and 17 M. catharralis.The strains studied and the samples from which they were isolated are shown in Table 1.

Discussion
Various studies have documented emerging antibiotic resistance over the course of time among respiratory tract and wound infection agents.This developing resistance to first-line antibiotics has led us to seek different alternatives for treatment.Although no studies of penicillin-resistant pneumococcus cases were published for many years, there are numerous recent studies noting increasing resistance [10][11][12].In addition, the presence of a penicillin allergy in 10% of the community, as well as reported resistance to substitute antibiotics such as macrolides for the treatment of community-acquired pneumonia, have caused a demand for the development and utilization of new alternatives [1].
Crespo-Ortiz et al. reported in a 17-year retrospective study that resistance to S. agalactiae isolates was emerging in Colombia [13].While no resistance to cefaclor and cefuroxime was noted with M. catharralis isolates during 1993-1994, Hsu et al. reported 8.3% and 1.3% resistance, respectively, in their study.In addition, ampicillin resistance was detected in all β-lactamase-producing M. catharralis isolates [12].Farrell et al. and Flamm et al. reported that penicillin resistance was emerging in S. pneumoniae isolates [14,15].A study by Rennie et al. pointed to a 9.1% resistance to amoxicillin clavulanic acid in H. influenzae isolates [16].Increasing erythromycin resistance to S. pyogenes was reported in 1970 in Japan, and the same condition was observed in European Union countries.Erythromycin, clarithromycin, and azithromycin resistance in the A, B, and C groups of β-hemolytic streptococci was encountered in a multicenter study performed in the United States [17].
As part of a new generation of cephalosporins, ceftaroline fosamil is a broad-spectrum antibiotic approved by the FDA for the treatment of respiratory tract and wound infections [5][6][7].Ceftaroline's effectiveness is related to its high binding affinity to modified penicillin-binding proteins as compared with other β-lactam antibiotics.Furthermore, ceftaroline is reported as being effective in vitro for bacteremia patients with penicillin-resistant S. pneumoniae [7].Since its approval in 2010, few clinical data is available about the efficacy of ceftaroline fosamil.
Our study included bacterial agents that are frequently isolated from respiratory tract and wound infections.These strains were identified using the latest technology in microbiological identification, particularly the MALDI-TOF method.We had an opportunity to rapidly identify and investigate the Unfortunately, the number of these strains was small.MIC ranges and MIC 50 and MIC 90 values for streptococcus and H. influenzae strains used in our study were similar to those found in other studies.This result gives rise to the observation that ceftaroline is effective against strains isolated from different regions.
The search for new antibiotics for treatment has come about because of the emergence of β-lactamaseproducing M. catharralis strains.The MIC range of M. catharralis isolates that were included in our study was between 0.125 and 2 µg/mL.These values are slightly higher than those found in other studies.Our data will perhaps be an example to other studies that may use an increased number of strains.On the other hand, the fact that current CLSI standards offer no evaluation data for MIC values makes research in this area difficult.

Conclusions
Our study showed that ceftaroline is quite effective against multiple and diverse bacterial isolates from different clinical samples of respiratory tract and wound infections.We recommend that ceftaroline could be a reasonable alternative for the treatment of these infections.

Table 1 .
Strain types and sample distribution RTS: respiratory tract samples; CSF: cerebrospinal fluid