European Journal of Cardiovascular Medicine

Breast abscesses are a common complication of mastitis and are typically associated with localized inflammation and systemic symptoms. While lactational breast abscesses arise as a consequence of mastitis during breastfeeding, non-lactational breast abscesses occur in women who are not breastfeeding. In recent years, there has been an increase in non-lactational cases, emphasizing the need for a deeper understanding of their microbial profiles and treatment strategies1.

Several factors predispose women to breast abscesses, including younger age, lower socioeconomic status, smoking, obesity, and comorbidities such as diabetes mellitus or HIV infection. Pathogenically, Staphylococcus aureus is the leading causative agent, followed by other organisms like Staphylococcus epidermidis, Streptococcus species, and anaerobes. Notably, resistance patterns, particularly the emergence of methicillin-resistant Staphylococcus aureus (MRSA)2, complicate treatment.

This study aimed to evaluate the microbiological spectrum of lactational and non-lactational breast abscesses and assess the antibiotic susceptibility patterns of the isolated pathogens to guide effective treatment strategies.

This retrospective cohort study was conducted at Indra Hospital, Supaul, Bihar, over one year (January 2023 to December 2023). A total of 150 patients diagnosed with breast abscesses were included. Data on age, clinical presentation, laboratory investigations, and treatment modalities were collected from medical records.

Sample Collection and Microbiological Processing

Pus samples were aseptically collected from all patients and transported to the microbiology laboratory in tightly sealed containers. Initial analysis included Gram staining, followed by inoculation onto Blood Agar and MacConkey Agar plates3. Cultures were incubated at 37°C for 18–24 hours, with extended incubation for up to 48 hours if necessary.

Colonies were identified based on morphological characteristics, Gram stain results, and biochemical tests, including catalase, coagulase, oxidase, indole, and citrate utilization tests, among others. Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method on Mueller-Hinton Agar, with results interpreted according to Clinical and Laboratory Standards Institute (CLSI) guidelines5.

Antibiotics Tested

The antimicrobial panel included Ampicillin, Amoxyclav, Amikacin, Clindamycin, Cefazolin, Ceftriaxone, Ciprofloxacin, Imipenem, Linezolid, Tetracycline, Piperacillin-Tazobactam, Teicoplanin, and Vancomycin. Methicillin resistance in Staphylococcus aureus was assessed using a 30 µg Cefoxitin disc, while ESBL production in Gram-negative bacilli was evaluated via the double-disc diffusion method⁴.

Data Analysis

The prevalence of microorganisms and their antibiotic susceptibility patterns were analyzed and summarized as percentages.

Patient Demographics

Of the 150 patients, the mean age was 24 years (range: 18–56 years). The majority (83%) were aged between 18 and 34 years, followed by 8% aged 35–45 years, and 9% aged 46 years or older. Lactational breast abscesses accounted for 71.3% (107/150) of cases, while non-lactational abscesses comprised 28.6% (43/150)

                  Microbiological Findings

Bacterial growth was observed in 86% (129/150) of the pus specimens. Staphylococcus aureus was the predominant pathogen⁶, accounting for 79% (102/129) of all isolates. Non-lactational abscesses demonstrated a more diverse microbial profile, including Proteus spp., and Acinetobacter spp^24,25.

                Fig- Cultural growth in breast abcess pts.

Gram-negative bacteria were identified in 10.9% (14/129) of cases, including Escherichia coli (4 isolates), Pseudomonas aeruginosa (2 isolates), Proteus spp. (1 isolate), and Acinetobacter spp. (1 isolate). Two E. coli isolates were confirmed as ESBL producers^22.23.

Antibiotic Susceptibility Patterns

Gram-Positive Isolates

• All Gram-positive isolates were resistant to Ampicillin²¹.
• Methicillin-sensitive Staphylococcus aureus (MSSA)⁷ demonstrated 100% sensitivity to Teicoplanin, Linezolid, and Vancomycin.
• Methicillin-resistant Staphylococcus aureus (MRSA) showed 100% sensitivity to Teicoplanin and Vancomycin, with 95% sensitivity to Linezolid⁸.
• Inducible clindamycin resistance (D-test positive)⁸ was observed in 18.9% (11/102) of S. aureus isolates, including 7 MRSA and 4 MSSA isolates.

All coagulase-negative staphylococci were methicillin-sensitive.

Gram-Negative Isolates

• All Gram-negative bacteria were resistant to Ampicillin.
• 100% sensitivity was observed to Imipenem.
• Most Gram-negative isolates demonstrated resistance to Ciprofloxacin, while all were sensitive to aminoglycosides, except for one E. coli isolate⁹.

This study confirms Staphylococcus aureus as the leading pathogen in both lactational and non-lactational breast abscesses, consistent with existing literature. However, the mixed bacterial flora in non-lactational abscesses highlights the need for broader-spectrum antibiotics in these cases^10.11.12.

The high prevalence of antibiotic resistance, particularly to Ampicillin and Ciprofloxacin, underscores the importance of routine pus culture and sensitivity testing to guide therapy. Notably, MRSA isolates exhibited significant resistance patterns¹³, necessitating the use of effective agents such as Teicoplanin, Vancomycin, and Linezolid.

The demographic distribution, with a predominance of younger women^13,14, reflects the impact of lactation and associated hormonal changes. The findings also underscore the role of tailored antimicrobial regimens to optimize outcomes and minimize complications¹⁵.

Breast abscesses, whether lactational or non-lactational, require targeted antimicrobial therapy based on culture and sensitivity results. Staphylococcus aureus remains the primary pathogen, but non-lactational abscesses often involve mixed flora, necessitating a broader therapeutic approach. The high rates of antibiotic resistance highlight the need for judicious antibiotic use and ongoing surveillance^16,17,18.

RECOMMENDATIONS

• Routine pus culture and sensitivity testing should be mandatory for all breast abscess cases.
• Empirical therapy for lactational abscesses should prioritize coverage against Staphylococcus aureus^19,20.
• Broader-spectrum antibiotics should be considered for non-lactational abscesses, pending culture results²¹.
• Continued monitoring of antibiotic resistance patterns is crucial to inform treatment protocols^23,26.
• Further research with larger sample sizes and longitudinal designs is recommended to validate these findings and explore emerging resistance trends.

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